Publications by authors named "Sandra Donkervoort"

108 Publications

Antibiotic prophylaxis for acute cholecystectomy: PEANUTS II multicentre randomized non-inferiority clinical trial.

Br J Surg 2022 Jan 10. Epub 2022 Jan 10.

Department of Surgery, St Antonius Hospital, Nieuwegein, the Netherlands.

Background: Guidelines recommending antibiotic prophylaxis at emergency cholecystectomy for cholecystitis were based on low-quality evidence. The aim of this trial was to demonstrate that omitting antibiotics is not inferior to their prophylactic use.

Methods: This multicentre, randomized, open-label, non-inferiority clinical trial randomly assigned adults with mild-to-moderate acute calculous cholecystitis (immediate cholecystectomy indicated) to 2 g cefazolin administered before incision or no antibiotic prophylaxis. The primary endpoint was a composite of all postoperative infectious complications in the first 30 days after surgery. Secondary endpoints included all individual components of the primary endpoint, other morbidity, and duration of hospital stay.

Results: Sixteen of 226 patients (7.1 per cent) in the single-dose prophylaxis group and 29 of 231 (12.6 per cent) in the no-prophylaxis group developed postoperative infectious complications (absolute difference 5.5 (95 per cent c.i. -0.4 to 11.3) per cent). With a non-inferiority margin of 10 per cent, non-inferiority of no prophylaxis was not proven. The number of surgical-site infections was significantly higher in the no-prophylaxis group (5.3 versus 12.1 per cent; P = 0.010). No differences were observed in the number of other complications, or duration of hospital stay.

Conclusion: Omitting antibiotic prophylaxis is not recommended.
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http://dx.doi.org/10.1093/bjs/znab441DOI Listing
January 2022

BET1 variants establish impaired vesicular transport as a cause for muscular dystrophy with epilepsy.

EMBO Mol Med 2021 Dec 15;13(12):e13787. Epub 2021 Nov 15.

Biochemistry III/Faculty of Chemistry, Bielefeld University, Bielefeld, Germany.

BET1 is required, together with its SNARE complex partners GOSR2, SEC22b, and Syntaxin-5 for fusion of endoplasmic reticulum-derived vesicles with the ER-Golgi intermediate compartment (ERGIC) and the cis-Golgi. Here, we report three individuals, from two families, with severe congenital muscular dystrophy (CMD) and biallelic variants in BET1 (P1 p.(Asp68His)/p.(Ala45Valfs*2); P2 and P3 homozygous p.(Ile51Ser)). Due to aberrant splicing and frameshifting, the variants in P1 result in low BET1 protein levels and impaired ER-to-Golgi transport. Since in silico modeling suggested that p.(Ile51Ser) interferes with binding to interaction partners other than SNARE complex subunits, we set off and identified novel BET1 interaction partners with low affinity for p.(Ile51Ser) BET1 protein compared to wild-type, among them ERGIC-53. The BET1/ERGIC-53 interaction was validated by endogenous co-immunoprecipitation with both proteins colocalizing to the ERGIC compartment. Mislocalization of ERGIC-53 was observed in P1 and P2's derived fibroblasts; while in the p.(Ile51Ser) P2 fibroblasts specifically, mutant BET1 was also mislocalized along with ERGIC-53. Thus, we establish BET1 as a novel CMD/epilepsy gene and confirm the emerging role of ER/Golgi SNAREs in CMD.
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http://dx.doi.org/10.15252/emmm.202013787DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8649873PMC
December 2021

MLIP causes recessive myopathy with rhabdomyolysis, myalgia and baseline elevated  serum creatine kinase.

Brain 2021 10;144(9):2722-2731

Department of Chemistry and Earth Science, College of Arts and Sciences, Qatar University, Qatar.

Striated muscle needs to maintain cellular homeostasis in adaptation to increases in physiological and metabolic demands. Failure to do so can result in rhabdomyolysis. The identification of novel genetic conditions associated with rhabdomyolysis helps to shed light on hitherto unrecognized homeostatic mechanisms. Here we report seven individuals in six families from different ethnic backgrounds with biallelic variants in MLIP, which encodes the muscular lamin A/C-interacting protein, MLIP. Patients presented with a consistent phenotype characterized by mild muscle weakness, exercise-induced muscle pain, variable susceptibility to episodes of rhabdomyolysis, and persistent basal elevated serum creatine kinase levels. The biallelic truncating variants were predicted to result in disruption of the nuclear localizing signal of MLIP. Additionally, reduced overall RNA expression levels of the predominant MLIP isoform were observed in patients' skeletal muscle. Collectively, our data increase the understanding of the genetic landscape of rhabdomyolysis to now include MLIP as a novel disease gene in humans and solidifies MLIP's role in normal and diseased skeletal muscle homeostasis.
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http://dx.doi.org/10.1093/brain/awab275DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8536936PMC
October 2021

Recruitment challenges to the I CARE study: a randomised trial on general practitioner-led colon cancer survivorship care.

BMJ Open 2021 08 24;11(8):e048985. Epub 2021 Aug 24.

Department of General Practice, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands.

Objectives: The I CARE study (Improving Care After colon canceR treatment in the Netherlands) aims to compare surgeon-led to general practitioner (GP)-led colon cancer survivorship care. Recruitment to the trial took longer than expected. In this descriptive study, recruitment is critically reviewed.

Setting: Patients were recruited from eight Dutch medical centres.

Participants: Patients treated with curative intent for stages I-III colon cancer. Target patient sample size was calculated at 300.

Interventions: Patients were randomised to surgeon-led (usual) versus GP-led care, with or without access to an eHealth application (Oncokompas).

Outcome Measures: Baseline characteristics of (non-)participants, reasons for non-participation and strategies to improve recruitment were reviewed.

Results: Out of 1238 eligible patients, 353 patients were included. Of these, 50 patients dropped out shortly after randomisation and before start of the intervention, resulting in a participation rate of 25%. Participants were on average slightly younger (68.1 years vs 69.3 years) and more often male (67% vs 50%) in comparison to non-participants. A total of 806 patients declined participation for reasons most often relating to research (57%), including the wish to remain in specialist care (31%) and too much effort to participate (12%). Some patients mentioned health (9%) and confrontation with the disease (5%) as a reason. In 43 cases, GPs declined participation, often related to the study objective, need for financial compensation and time restraints. The generally low participation rate led to concerns about reaching the target sample size. Methods to overcome recruitment challenges included changes to the original recruitment procedure and the addition of new study centres.

Conclusions: Challenges were faced in the recruitment to a randomised trial on GP-led colon cancer survivorship care. Research on the transition of care requires sufficient time, funding and support base among patients and healthcare professionals. These findings will help inform researchers and policy-makers on the development of future practices.

Trial Registration Number: NTR4860.
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http://dx.doi.org/10.1136/bmjopen-2021-048985DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8386209PMC
August 2021

A Clinical Decision Tool for Selection of Patients With Symptomatic Cholelithiasis for Cholecystectomy Based on Reduction of Pain and a Pain-Free State Following Surgery.

JAMA Surg 2021 10 13;156(10):e213706. Epub 2021 Oct 13.

Department of Surgery, Radboud University Medical Center, Nijmegen, the Netherlands.

Importance: There is currently no consensus on the indication for cholecystectomy in patients with uncomplicated gallstone disease.

Objective: To report on the development and validation of a multivariable prediction model to better select patients for surgery.

Design, Setting, And Participants: This study evaluates data from 2 multicenter prospective trials (the previously published Scrutinizing (In)efficient Use of Cholecystectomy: A Randomized Trial Concerning Variation in Practice [SECURE] and the Standardized Work-up for Symptomatic Cholecystolithiasis [Success] trial) collected from the outpatient clinics of 25 Dutch hospitals between April 2014 and June 2019 and including 1561 patients with symptomatic uncomplicated cholelithiasis, defined as gallstone disease without signs of complicated cholelithiasis (ie, biliary pancreatitis, cholangitis, common bile duct stones or cholecystitis). Data were analyzed from January 2020 to June 2020.

Exposures: Patient characteristics, comorbidity, surgical outcomes, pain, and symptoms measured at baseline and at 6 months' follow-up.

Main Outcomes And Measures: A multivariable regression model to predict a pain-free state or a clinically relevant reduction in pain after surgery. Model performance was evaluated using calibration and discrimination.

Results: A total of 1561 patients were included (494 patients in 7 hospitals in the development cohort and 1067 patients in 24 hospitals in the validation cohort; 6 hospitals included patients in both cohorts). In the development cohort, 395 patients (80.0%) underwent cholecystectomy. After surgery, 225 patients (57.0%) reported that they were pain free and 295 (74.7%) reported a clinically relevant reduction in pain. A multivariable prediction model showed that increased age, no history of abdominal surgery, increased visual analog scale pain score at baseline, pain radiation to the back, pain reduction with simple analgesics, nausea, and no heartburn were independent predictors of clinically relevant pain reduction after cholecystectomy. After internal validation, good discrimination was found (C statistic, 0.80; 95% CI, 0.74-0.84) between patients with and without clinically relevant pain reduction. The model had very good overall calibration and minimal underestimation of the probability. External validation indicated a good discrimination between patients with and without clinically relevant pain reduction (C statistic, 0.74; 95% CI, 0.70-0.78) and fair calibration with some overestimation of probability by the model.

Conclusions And Relevance: The model validated in this study may help predict the probability of pain reduction after cholecystectomy and thus aid surgeons in deciding whether patients with uncomplicated cholelithiasis will benefit from cholecystectomy.
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http://dx.doi.org/10.1001/jamasurg.2021.3706DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8358816PMC
October 2021

International retrospective natural history study of -related congenital muscular dystrophy.

Brain Commun 2021 Jul 11;3(3):fcab075. Epub 2021 Apr 11.

Children's Neurosciences Centre, Royal Children's Hospital, Victoria, Australia.

Muscular dystrophies due to heterozygous pathogenic variants in gene cover a broad spectrum of clinical presentations and severity with an age of onset ranging from the neonatal period to adulthood. The natural history of these conditions is not well defined, particularly in patients with congenital or early onset who arguably present with the highest disease burden. Thus the definition of natural history endpoints along with clinically revelant outcome measures is essential to establishing both clinical care planning and clinical trial readiness for this patient group. We designed a large international cross-sectional retrospective natural history study of patients with genetically proven muscle laminopathy who presented with symptoms before two years of age intending to identify and characterize an optimal clinical trial cohort with pertinent motor, cardiac and respiratory endpoints. Quantitative statistics were used to evaluate associations between variants and distinct clinical events. The study included 151 patients (median age at symptom onset 0.9years, range: 0.0-2.0). Age of onset and age of death were significantly lower in patients who never acquired independent ambulation compared to patients who achieved independent ambulation. Most of the patients acquired independent ambulation (n = 101, 66.9%), and subsequently lost this ability (n = 86; 85%). The age of ambulation acquisition (median: 1.2 years, range: 0.8-4.0) and age of ambulation loss (median: 7 years, range: 1.2-38.0) were significantly associated with the age of the first respiratory interventions and the first cardiac symptoms. Respiratory and gastrointestinal interventions occurred during first decade while cardiac interventions occurred later. Genotype-phenotype analysis showed that the most common mutation, p.Arg249Trp (20%), was significantly associated with a more severe disease course. This retrospective natural history study of early onset -related muscular dystrophy confirms the progressive nature of the disorder, initially involving motor symptoms prior to onset of other symptoms (respiratory, orthopaedic, cardiac and gastrointestinal). The study also identifies subgroups of patients with a range of long-term outcomes. Ambulatory status was an important mean of stratification along with the presence or absence of the p.Arg249Trp mutation. These categorizations will be important for future clinical trial cohorts. Finally, this study furthers our understanding of the progression of early onset -related muscular dystrophy and provides important insights into the anticipatory care needs of -related respiratory and cardiac manifestations.
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http://dx.doi.org/10.1093/braincomms/fcab075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8260964PMC
July 2021

Giant axonal neuropathy: cross-sectional analysis of a large natural history cohort.

Brain 2021 11;144(10):3239-3250

National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD 20892, USA.

Giant axonal neuropathy (GAN) is an ultra-rare autosomal recessive, progressive neurodegenerative disease with early childhood onset that presents as a prominent sensorimotor neuropathy and commonly progresses to affect both the PNS and CNS. The disease is caused by biallelic mutations in the GAN gene located on 16q23.2, leading to loss of functional gigaxonin, a substrate specific ubiquitin ligase adapter protein necessary for the regulation of intermediate filament turnover. Here, we report on cross-sectional data from the first study visit of a prospectively collected natural history study of 45 individuals, age range 3-21 years with genetically confirmed GAN to describe and cross-correlate baseline clinical and functional cohort characteristics. We review causative variants distributed throughout the GAN gene in this cohort and identify a recurrent founder mutation in individuals with GAN of Mexican descent as well as cases of recurrent uniparental isodisomy. Through cross-correlational analysis of measures of strength, motor function and electrophysiological markers of disease severity, we identified the Motor Function Measure 32 to have the strongest correlation across measures and age in individuals with GAN. We analysed the Motor Function Measure 32 scores as they correspond to age and ambulatory status. Importantly, we identified and characterized a subcohort of individuals with a milder form of GAN and with a presentation similar to Charcot-Marie-Tooth disease. Such a clinical presentation is distinct from the classic presentation of GAN, and we demonstrate how the two groups diverge in performance on the Motor Function Measure 32 and other functional motor scales. We further present data on the first systematic clinical analysis of autonomic impairment in GAN as performed on a subset of the natural history cohort. Our cohort of individuals with genetically confirmed GAN is the largest reported to date and highlights the clinical heterogeneity and the unique phenotypic and functional characteristics of GAN in relation to disease state. The present work is designed to serve as a foundation for a prospective natural history study and functions in concert with the ongoing gene therapy trial for children with GAN.
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http://dx.doi.org/10.1093/brain/awab179DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8634068PMC
November 2021

Childhood amyotrophic lateral sclerosis caused by excess sphingolipid synthesis.

Nat Med 2021 Jul 31;27(7):1197-1204. Epub 2021 May 31.

Department of Neurology, Hereditary Neuropathy Foundation Center of Excellence, Neuroscience Institute, Hackensack University Medical Center, Hackensack Meridian School of Medicine, Hackensack, NJ, USA.

Amyotrophic lateral sclerosis (ALS) is a progressive, neurodegenerative disease of the lower and upper motor neurons with sporadic or hereditary occurrence. Age of onset, pattern of motor neuron degeneration and disease progression vary widely among individuals with ALS. Various cellular processes may drive ALS pathomechanisms, but a monogenic direct metabolic disturbance has not been causally linked to ALS. Here we show SPTLC1 variants that result in unrestrained sphingoid base synthesis cause a monogenic form of ALS. We identified four specific, dominantly acting SPTLC1 variants in seven families manifesting as childhood-onset ALS. These variants disrupt the normal homeostatic regulation of serine palmitoyltransferase (SPT) by ORMDL proteins, resulting in unregulated SPT activity and elevated levels of canonical SPT products. Notably, this is in contrast with SPTLC1 variants that shift SPT amino acid usage from serine to alanine, result in elevated levels of deoxysphingolipids and manifest with the alternate phenotype of hereditary sensory and autonomic neuropathy. We custom designed small interfering RNAs that selectively target the SPTLC1 ALS allele for degradation, leave the normal allele intact and normalize sphingolipid levels in vitro. The role of primary metabolic disturbances in ALS has been elusive; this study defines excess sphingolipid biosynthesis as a fundamental metabolic mechanism for motor neuron disease.
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http://dx.doi.org/10.1038/s41591-021-01346-1DOI Listing
July 2021

Loss of function mutations in GEMIN5 cause a neurodevelopmental disorder.

Nat Commun 2021 05 7;12(1):2558. Epub 2021 May 7.

Department of Pediatric Neurophysiology AP-HP, Necker Enfants Malades Hospital, Paris University, Paris, France.

GEMIN5, an RNA-binding protein is essential for assembly of the survival motor neuron (SMN) protein complex and facilitates the formation of small nuclear ribonucleoproteins (snRNPs), the building blocks of spliceosomes. Here, we have identified 30 affected individuals from 22 unrelated families presenting with developmental delay, hypotonia, and cerebellar ataxia harboring biallelic variants in the GEMIN5 gene. Mutations in GEMIN5 perturb the subcellular distribution, stability, and expression of GEMIN5 protein and its interacting partners in patient iPSC-derived neurons, suggesting a potential loss-of-function mechanism. GEMIN5 mutations result in disruption of snRNP complex assembly formation in patient iPSC neurons. Furthermore, knock down of rigor mortis, the fly homolog of human GEMIN5, leads to developmental defects, motor dysfunction, and a reduced lifespan. Interestingly, we observed that GEMIN5 variants disrupt a distinct set of transcripts and pathways as compared to SMA patient neurons, suggesting different molecular pathomechanisms. These findings collectively provide evidence that pathogenic variants in GEMIN5 perturb physiological functions and result in a neurodevelopmental delay and ataxia syndrome.
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http://dx.doi.org/10.1038/s41467-021-22627-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8105379PMC
May 2021

A form of muscular dystrophy associated with pathogenic variants in JAG2.

Am J Hum Genet 2021 05 15;108(5):840-856. Epub 2021 Apr 15.

Centre de Référence Neuromusculaire and Paediatric Neurology Department, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles, 1020 Brussels, Belgium.

JAG2 encodes the Notch ligand Jagged2. The conserved Notch signaling pathway contributes to the development and homeostasis of multiple tissues, including skeletal muscle. We studied an international cohort of 23 individuals with genetically unsolved muscular dystrophy from 13 unrelated families. Whole-exome sequencing identified rare homozygous or compound heterozygous JAG2 variants in all 13 families. The identified bi-allelic variants include 10 missense variants that disrupt highly conserved amino acids, a nonsense variant, two frameshift variants, an in-frame deletion, and a microdeletion encompassing JAG2. Onset of muscle weakness occurred from infancy to young adulthood. Serum creatine kinase (CK) levels were normal or mildly elevated. Muscle histology was primarily dystrophic. MRI of the lower extremities revealed a distinct, slightly asymmetric pattern of muscle involvement with cores of preserved and affected muscles in quadriceps and tibialis anterior, in some cases resembling patterns seen in POGLUT1-associated muscular dystrophy. Transcriptome analysis of muscle tissue from two participants suggested misregulation of genes involved in myogenesis, including PAX7. In complementary studies, Jag2 downregulation in murine myoblasts led to downregulation of multiple components of the Notch pathway, including Megf10. Investigations in Drosophila suggested an interaction between Serrate and Drpr, the fly orthologs of JAG1/JAG2 and MEGF10, respectively. In silico analysis predicted that many Jagged2 missense variants are associated with structural changes and protein misfolding. In summary, we describe a muscular dystrophy associated with pathogenic variants in JAG2 and evidence suggests a disease mechanism related to Notch pathway dysfunction.
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http://dx.doi.org/10.1016/j.ajhg.2021.03.020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8206160PMC
May 2021

Pathogenic variants in TNNC2 cause congenital myopathy due to an impaired force response to calcium.

J Clin Invest 2021 05;131(9)

Deptartment of Physiology, Amsterdam UMC (location VUmc), Amsterdam, Netherlands.

Troponin C (TnC) is a critical regulator of skeletal muscle contraction; it binds Ca2+ to activate muscle contraction. Surprisingly, the gene encoding fast skeletal TnC (TNNC2) has not yet been implicated in muscle disease. Here, we report 2 families with pathogenic variants in TNNC2. Patients present with a distinct, dominantly inherited congenital muscle disease. Molecular dynamics simulations suggested that the pathomechanisms by which the variants cause muscle disease include disruption of the binding sites for Ca2+ and for troponin I. In line with these findings, physiological studies in myofibers isolated from patients' biopsies revealed a markedly reduced force response of the sarcomeres to [Ca2+]. This pathomechanism was further confirmed in experiments in which contractile dysfunction was evoked by replacing TnC in myofibers from healthy control subjects with recombinant, mutant TnC. Conversely, the contractile dysfunction of myofibers from patients was repaired by replacing endogenous, mutant TnC with recombinant, wild-type TnC. Finally, we tested the therapeutic potential of the fast skeletal muscle troponin activator tirasemtiv in patients' myofibers and showed that the contractile dysfunction was repaired. Thus, our data reveal that pathogenic variants in TNNC2 cause congenital muscle disease, and they provide therapeutic angles to repair muscle contractility.
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http://dx.doi.org/10.1172/JCI145700DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8087209PMC
May 2021

A novel variant in the COL6A1 gene causing Ullrich congenital muscular dystrophy in a consanguineous family: a case report.

BMC Neurol 2021 Mar 9;21(1):105. Epub 2021 Mar 9.

Human Genetics Unit, Department of Anatomy, Faculty of Medicine, University of Colombo, Colombo 8, Sri Lanka.

Background: Collagen VI-related dystrophies are a subtype of congenital muscular dystrophy caused by pathogenic variants in COL6A1, COL6A2 or COL6A3 genes affecting skeletal muscles and connective tissue. The clinical phenotype ranges from the milder Bethlem myopathy to the severe Ullrich congenital muscular dystrophy (UCMD). Herein, we report the first consanguineous Sri Lankan family with two children affected with UCMD due to a novel variant in the COL6A1 gene.

Case Presentation: Two sisters, aged 10-years and 7-years, presented with progressive, bilateral proximal muscle weakness. Both probands had delayed motor milestones and demonstrated difficulty in standing from a squatting position, climbing stairs and raising arms above the shoulders. Cognitive, language and social development were age appropriate. Examination showed proximal muscle weakness of the upper and lower extremities and hyperlaxity of the wrist and fingers in both with some variability in clinical severity noted between the two siblings. Serum creatine kinase levels were elevated, and electromyography showed low polyphasic motor unit potentials in the 10-year-old and myopathic features with short duration motor unit potentials with no polyphasia in the 7-year-old. Whole exome sequencing (WES) was performed and a novel, homozygous missense, likely pathogenic variant in exon 25 of COL6A1 gene [NM_001848: c.1667G > T;NP_001839.2:p.Gly556Val] was identified in both probands. This variant was validated by Sanger sequencing in proband 1 as well as proband 2, and the parents and an unaffected sibling were found to be heterozygote carriers for the same variant.

Conclusions: The findings in this family add to the expanding number of COL6A1 variants identified and provides a better understanding of the genotype-phenotype correlations associated with UCMD.
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http://dx.doi.org/10.1186/s12883-021-02134-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7941924PMC
March 2021

Clinical and Molecular Spectrum Associated with COL6A3 c.7447A>G p.(Lys2483Glu) Variant: Elucidating its Role in Collagen VI-related Myopathies.

J Neuromuscul Dis 2021 ;8(4):633-645

Centre de Recherche en Myologie, Institut de Myologie, Sorbonne Université, Inserm, Paris, France.

Background: Dominant and recessive autosomal pathogenic variants in the three major genes (COL6A1-A2-A3) encoding the extracellular matrix protein collagen VI underlie a group of myopathies ranging from early-onset severe conditions (Ullrich congenital muscular dystrophy) to milder forms maintaining independent ambulation (Bethlem myopathy). Diagnosis is based on the combination of clinical presentation, muscle MRI, muscle biopsy, analysis of collagen VI secretion, and COL6A1-A2-A3 genetic analysis, the interpretation of which can be challenging.

Objective: To refine the phenotypical spectrum associated with the frequent COL6A3 missense variant c.7447A>G (p.Lys2483Glu).

Methods: We report the clinical and molecular findings in 16 patients: 12 patients carrying this variant in compound heterozygosity with another COL6A3 variant, and four homozygous patients.

Results: Patients carrying this variant in compound heterozygosity with a truncating COL6A3 variant exhibit a phenotype consistent with COL6-related myopathies (COL6-RM), with joint contractures, proximal weakness and skin abnormalities. All remain ambulant in adulthood and only three have mild respiratory involvement. Most show typical muscle MRI findings. In five patients, reduced collagen VI secretion was observed in skin fibroblasts cultures. All tested parents were unaffected heterozygous carriers. Conversely, two out of four homozygous patients did not present with the classical COL6-RM clinical and imaging findings. Collagen VI immunolabelling on cultured fibroblasts revealed rather normal secretion in one and reduced secretion in another. Muscle biopsy from one homozygous patient showed myofibrillar disorganization and rimmed vacuoles.

Conclusions: In light of our results, we postulate that the COL6A3 variant c.7447A>G may act as a modulator of the clinical phenotype. Thus, in patients with a typical COL6-RM phenotype, a second variant must be thoroughly searched for, while for patients with atypical phenotypes further investigations should be conducted to exclude alternative causes. This works expands the clinical and molecular spectrum of COLVI-related myopathies.
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http://dx.doi.org/10.3233/JND-200577DOI Listing
December 2021

An ancestral 10-bp repeat expansion in VWA1 causes recessive hereditary motor neuropathy.

Brain 2021 03;144(2):584-600

Divisions of Neurology and Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, USA.

The extracellular matrix comprises a network of macromolecules such as collagens, proteoglycans and glycoproteins. VWA1 (von Willebrand factor A domain containing 1) encodes a component of the extracellular matrix that interacts with perlecan/collagen VI, appears to be involved in stabilizing extracellular matrix structures, and demonstrates high expression levels in tibial nerve. Vwa1-deficient mice manifest with abnormal peripheral nerve structure/function; however, VWA1 variants have not previously been associated with human disease. By interrogating the genome sequences of 74 180 individuals from the 100K Genomes Project in combination with international gene-matching efforts and targeted sequencing, we identified 17 individuals from 15 families with an autosomal-recessive, non-length dependent, hereditary motor neuropathy and rare biallelic variants in VWA1. A single disease-associated allele p.(G25Rfs*74), a 10-bp repeat expansion, was observed in 14/15 families and was homozygous in 10/15. Given an allele frequency in European populations approaching 1/1000, the seven unrelated homozygote individuals ascertained from the 100K Genomes Project represents a substantial enrichment above expected. Haplotype analysis identified a shared 220 kb region suggesting that this founder mutation arose >7000 years ago. A wide age-range of patients (6-83 years) helped delineate the clinical phenotype over time. The commonest disease presentation in the cohort was an early-onset (mean 2.0 ± 1.4 years) non-length-dependent axonal hereditary motor neuropathy, confirmed on electrophysiology, which will have to be differentiated from other predominantly or pure motor neuropathies and neuronopathies. Because of slow disease progression, ambulation was largely preserved. Neurophysiology, muscle histopathology, and muscle MRI findings typically revealed clear neurogenic changes with single isolated cases displaying additional myopathic process. We speculate that a few findings of myopathic changes might be secondary to chronic denervation rather than indicating an additional myopathic disease process. Duplex reverse transcription polymerase chain reaction and immunoblotting using patient fibroblasts revealed that the founder allele results in partial nonsense mediated decay and an absence of detectable protein. CRISPR and morpholino vwa1 modelling in zebrafish demonstrated reductions in motor neuron axonal growth, synaptic formation in the skeletal muscles and locomotive behaviour. In summary, we estimate that biallelic variants in VWA1 may be responsible for up to 1% of unexplained hereditary motor neuropathy cases in Europeans. The detailed clinical characterization provided here will facilitate targeted testing on suitable patient cohorts. This novel disease gene may have previously evaded detection because of high GC content, consequential low coverage and computational difficulties associated with robustly detecting repeat-expansions. Reviewing previously unsolved exomes using lower QC filters may generate further diagnoses.
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http://dx.doi.org/10.1093/brain/awaa420DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8263055PMC
March 2021

Innocuous pressure sensation requires A-type afferents but not functional ΡΙΕΖΟ2 channels in humans.

Nat Commun 2021 01 28;12(1):657. Epub 2021 Jan 28.

National Center for Complementary and Integrative Health, NIH, Bethesda, MD, USA.

The sensation of pressure allows us to feel sustained compression and body strain. While our understanding of cutaneous touch has grown significantly in recent years, how deep tissue sensations are detected remains less clear. Here, we use quantitative sensory evaluations of patients with rare sensory disorders, as well as nerve blocks in typical individuals, to probe the neural and genetic mechanisms for detecting non-painful pressure. We show that the ability to perceive innocuous pressures is lost when myelinated fiber function is experimentally blocked in healthy volunteers and that two patients lacking Aβ fibers are strikingly unable to feel innocuous pressures at all. We find that seven individuals with inherited mutations in the mechanoreceptor PIEZO2 gene, who have major deficits in touch and proprioception, are nearly as good at sensing pressure as healthy control subjects. Together, these data support a role for Aβ afferents in pressure sensation and suggest the existence of an unknown molecular pathway for its detection.
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http://dx.doi.org/10.1038/s41467-021-20939-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7844252PMC
January 2021

Association of Initial Maximal Motor Ability With Long-term Functional Outcome in Patients With COL6-Related Dystrophies.

Neurology 2021 03 13;96(10):e1413-e1424. Epub 2021 Jan 13.

From the Neuromuscular Unit (D.N.-d.B., C.O., L.C.-G., J.E.-E., M.A., J.C., C.J., C.J.-M., A.N.), Neuropaediatrics Department, Institut de Recerca Pediàtrica Hospital Sant Joan de Déu, Barcelona; Center for the Biomedical Research on Rare Diseases (CIBERER), ISCIII, Spain; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., S.D., Y.H., M.F., P.Y., T.O., M.E.L., J.D., C.G.B.), National Institute of Neurological Disorders and Stroke, Rehabilitation Medicine Department (M.J., A.M.), Clinical Research Center, and Neuromuscular Symptoms Unit (K.G.M.), Tissue Injury Branch, National Institute of Nursing Research, NIH, Bethesda, MD; Department of Neurology (C.D.-G., E.M.-M.), Hospital Universitario 12 de Octubre, Research Institute (imas12), Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain; Department of Rehabilitation and Physical Medicine (J.M., M.V.), Hospital Sant Joan de Deu, Barcelona, Spain; Neuromuscular Diseases Unit (J.D.-M.), Department of Neurology, Hospital de La Santa Creu i Sant Pau, Universitat Autònoma de Barcelona and Centre for Biomedical Network Research on Rare Diseases (CIBERER); Statistics Department (D.C.), Fundació Sant Joan de Déu; Department of Internal Medicine (J.C.M.), Hospital Clinic, Universitat de Barcelona and CIBERER, Villarroel 170; Neuropathology Unit (R.D.-R., M.O.), Department of Pathology and Neuromuscular Unit, IDIBELL-Hospital Universitari de Bellvitge, Barcelona, Spain; and Department of Pathology (C.J.), Hospital Sant Joan de Déu, Barcelona, Spain.

Objective: To accurately categorize the phenotypes of individuals with collagen VI-related dystrophies (COL6-RDs) during the first years of life to predict long-term motor function and pulmonary function, to provide phenotype-specific anticipatory care, and to improve clinical trial readiness.

Methods: This retrospective, multicenter, international study analyzed the relationship of long-term motor and pulmonary function with the initial maximal motor ability achieved in individuals with COL6-RD.

Results: We studied 119 patients with COL6-RD from Spain (n = 54) and the United States (n = 65). The early maximal motor milestones of ability to rise from the floor unassisted and ability to climb 4 steps without holding onto a railing demonstrated reliability in distinguishing between 3 COL6-RD phenotypic subgroups: (1) Ullrich congenital muscular dystrophy, (2) intermediate COL6-RD, and (3) Bethlem myopathy. Long-term motor function and pulmonary function are strongly correlated with the maximal motor ability achieved during the first years of life. Maximal motor capacity can predict other disease-relevant events such as the age at loss of ambulation and the need for the initiation of nocturnal noninvasive ventilation.

Conclusion: This work proposes a prospective phenotypic classification for COL6-RDs that will enable an accurate prediction of a patient's COL6-RD phenotype during the first years of life. The ability to establish a patient's COL6-RD phenotypic classification early will enable a more accurate prognosis of future motor and pulmonary function, thus improving anticipatory clinical care, and it will be instrumental in aiding the design of future clinical trials by allowing early stratification of trial cohorts.
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http://dx.doi.org/10.1212/WNL.0000000000011499DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8055317PMC
March 2021

De novo variants in SNAP25 cause an early-onset developmental and epileptic encephalopathy.

Genet Med 2021 04 10;23(4):653-660. Epub 2020 Dec 10.

Institute of Child Health, University Collge London, London, UK.

Purpose: This study aims to provide a comprehensive description of the phenotypic and genotypic spectrum of SNAP25 developmental and epileptic encephalopathy (SNAP25-DEE) by reviewing newly identified and previously reported individuals.

Methods: Individuals harboring heterozygous missense or loss-of-function variants in SNAP25 were assembled through collaboration with international colleagues, matchmaking platforms, and literature review. For each individual, detailed phenotyping, classification, and structural modeling of the identified variant were performed.

Results: The cohort comprises 23 individuals with pathogenic or likely pathogenic de novo variants in SNAP25. Intellectual disability and early-onset epilepsy were identified as the core symptoms of SNAP25-DEE, with recurrent findings of movement disorders, cerebral visual impairment, and brain atrophy. Structural modeling for all variants predicted possible functional defects concerning SNAP25 or impaired interaction with other components of the SNARE complex.

Conclusion: We provide a comprehensive description of SNAP25-DEE with intellectual disability and early-onset epilepsy mostly occurring before the age of two years. These core symptoms and additional recurrent phenotypes show an overlap to genes encoding other components or associated proteins of the SNARE complex such as STX1B, STXBP1, or VAMP2. Thus, these findings advance the concept of a group of neurodevelopmental disorders that may be termed "SNAREopathies."
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http://dx.doi.org/10.1038/s41436-020-01020-wDOI Listing
April 2021

FBXO28 causes developmental and epileptic encephalopathy with profound intellectual disability.

Epilepsia 2021 01 6;62(1):e13-e21. Epub 2020 Dec 6.

Epilepsy Research Centre, Department of Medicine, Austin Health, The University of Melbourne, Heidelberg, Victoria, Australia.

Chromosome 1q41-q42 deletion syndrome is a rare cause of intellectual disability, seizures, dysmorphology, and multiple anomalies. Two genes in the 1q41-q42 microdeletion, WDR26 and FBXO28, have been implicated in monogenic disease. Patients with WDR26 encephalopathy overlap clinically with those with 1q41-q42 deletion syndrome, whereas only one patient with FBXO28 encephalopathy has been described. Seizures are a prominent feature of 1q41-q42 deletion syndrome; therefore, we hypothesized that pathogenic FBXO28 variants cause developmental and epileptic encephalopathies (DEEs). We describe nine new patients with FBXO28 pathogenic variants (four missense, including one recurrent, three nonsense, and one frameshift) and analyze all 10 known cases to delineate the phenotypic spectrum. All patients had epilepsy and 9 of 10 had DEE, including infantile spasms (3) and a progressive myoclonic epilepsy (1). Median age at seizure onset was 22.5 months (range 8 months to 5 years). Nine of 10 patients had intellectual disability, which was profound in six of nine and severe in three of nine. Movement disorders occurred in eight of 10 patients, six of 10 had hypotonia, four of 10 had acquired microcephaly, and five of 10 had dysmorphic features, albeit different to those typically seen in 1q41-q42 deletion syndrome and WDR26 encephalopathy. We distinguish FBXO28 encephalopathy from both of these disorders with more severe intellectual impairment, drug-resistant epilepsy, and hyperkinetic movement disorders.
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http://dx.doi.org/10.1111/epi.16784DOI Listing
January 2021

Pathogenic Variants in the Myosin Chaperone UNC-45B Cause Progressive Myopathy with Eccentric Cores.

Am J Hum Genet 2020 12 19;107(6):1078-1095. Epub 2020 Nov 19.

Department of Clinical Genome Analysis, Medical Genome Center, National Center of Neurology and Psychiatry, 187-8551 Tokyo, Japan.

The myosin-directed chaperone UNC-45B is essential for sarcomeric organization and muscle function from Caenorhabditis elegans to humans. The pathological impact of UNC-45B in muscle disease remained elusive. We report ten individuals with bi-allelic variants in UNC45B who exhibit childhood-onset progressive muscle weakness. We identified a common UNC45B variant that acts as a complex hypomorph splice variant. Purified UNC-45B mutants showed changes in folding and solubility. In situ localization studies further demonstrated reduced expression of mutant UNC-45B in muscle combined with abnormal localization away from the A-band towards the Z-disk of the sarcomere. The physiological relevance of these observations was investigated in C. elegans by transgenic expression of conserved UNC-45 missense variants, which showed impaired myosin binding for one and defective muscle function for three. Together, our results demonstrate that UNC-45B impairment manifests as a chaperonopathy with progressive muscle pathology, which discovers the previously unknown conserved role of UNC-45B in myofibrillar organization.
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http://dx.doi.org/10.1016/j.ajhg.2020.11.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820787PMC
December 2020

Responsiveness and Minimal Clinically Important Difference of the Motor Function Measure in Collagen VI-Related Dystrophies and Laminin Alpha2-Related Muscular Dystrophy.

Arch Phys Med Rehabil 2021 04 6;102(4):604-610. Epub 2020 Nov 6.

Department of Pediatric Physical Medicine and Rehabilitation, Hospices Civils de Lyon, Bron, France; Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD; Neuromyogen Institute, CNRS UMR 5310-INSERM, University of Lyon, Lyon, France; University of Lyon 1, F-69100, Villeurbanne, France.

Objectives: To investigate the responsiveness of the motor function measure (MFM) and determine the minimal clinically important difference (MCID) in individuals with 2 common types of congenital muscular dystrophy (CMD).

Design: Observational, prospective, single center, cohort study.

Setting: National Institute of Neurological Disorders and Stroke (NINDS) of the National Institutes of Health (NIH).

Participants: Individuals (N=44) with collagen VI-related dystrophies (COL6-RD, n=23) and 21 individuals laminin alpha2-related muscular dystrophy (LAMA2-RD, n=21) enrolled in a 4-year longitudinal natural history study.

Interventions: Not applicable.

Main Outcome Measures: Responsiveness of the MFM-32 and the Rasch-scaled MFM-25 and the MCID of the MFM-32 determined from a patient-reported anchor with 2 different methods, within-patient and between-patient.

Results: The original MFM-32 and Rasch-scaled MFM-25 performed similarly overall in both the COL6-RD and LAMA2-RD populations, with all subscores (D1, standing and transfers; D2, axial and proximal; D3, distal) showing a significant decrease over time, except MFM D1 and D3 for LAMA2-RD. The MFM D1 subscore was the most sensitive to change for ambulant individuals, whereas the MFM D2 subscore was the most sensitive to change for nonambulant individuals. The MCID for the MFM-32 total score was calculated as 2.5 and 3.9 percentage points according to 2 different methods.

Conclusions: The MFM showed strong responsiveness in individuals with LAMA2-RD and COL6-RD. Because a floor effect was identified more prominently with the Rasch-Scaled MFM-25, the use of the original MFM-32 as a quantitative variable with the assumption of scale linearity appears to be a good compromise. When designing clinical trials in congenital muscular dystrophies, the use of MCID for MFM should be considered to determine if a given intervention effects show not only a statistically significant change but also a clinically meaningful change.
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http://dx.doi.org/10.1016/j.apmr.2020.10.116DOI Listing
April 2021

Cardiac MRI identifies valvular and myocardial disease in a subset of ANO5-related muscular dystrophy patients.

Neuromuscul Disord 2020 09 24;30(9):742-749. Epub 2020 Jul 24.

Neuromuscular and Neurogenetic Disorders of Childhood Section, Neurogenetics Branch, NINDS, NIH, Bethesda, MD, United States. Electronic address:

Patients with bi-allelic loss-of-function mutations in the gene ANO5 most commonly present with muscular dystrophy. In some studies, patients with ANO5-related dystrophy (ANO5-RD) had evidence of mild cardiac abnormalities; however, cardiac magnetic resonance imaging (MRI) has not been used for myocardial characterization. Ten patients with genetically confirmed ANO5-RD were enrolled in a phenotyping study to better characterize cardiac involvement. Evaluations included medical history, neurological examination and cardiac evaluations (electrocardiogram, echocardiogram and cardiac MRI). All patients were clinically asymptomatic from a cardiac perspective. Muscle MRI was consistent with previous studies of ANO5-RD with increased T1 signal in the posterior and medial compartments of the upper leg and the posterior compartment of the lower leg. Cardiac studies using echocardiography and cardiac MRI revealed dilation of the aortic root and thickening of the aortic valve without significant stenosis in 3/10 patients. There was evidence of abnormal late gadolinium enhancement (LGE) on cardiac MRI in 2/10 patients. In ANO5-RD, the development of cardiac fibrosis, edema or inflammation as demonstrated by LGE has not yet been reported. Cardiac MRI can characterize cardiac tissue and may detect subtle changes before they appear on echocardiography, with potential prognostic implications.
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http://dx.doi.org/10.1016/j.nmd.2020.07.001DOI Listing
September 2020

The clinical, histologic, and genotypic spectrum of -related myopathy: A case series.

Neurology 2020 09 13;95(11):e1512-e1527. Epub 2020 Aug 13.

From the Basic and Translational Myology Lab (R.N.V.-Q., V.G., A.F.), UMR8251, Université de Paris/CNRS; Centre de Référence des Maladies Neuromusculaires Nord/Est/Ile de France (R.N.V.-Q., B. Eymard, N.B.R., A.F.) and Neuromuscular Morphology Unit (N.B.R., M.F.), Institut de Myologie, Pitié-Salpêtrière Hospital, AP-HP, Paris, France; Department of Paediatric Neurology (M.v.d.H.), Medinzinische Fakultät Carl Gustav Carus, Technische Universität Dresden, Germany; AP-HP (C.M., P.R.), Centre de Génétique Moléculaire et Chromosomique, UF Cardiogénétique et Myogénétique Moléculaire et Cellulaire, GH Pitié-Salpêtrière, Paris; Department of Neurology (V.G.), University Hospital of Montpellier, France; Neuromuscular and Neurogenetic Disorders of Childhood Section (S.D.), National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD; Unit of Neuromuscular and Neurodegenerative Disorders (E.B.), Bambino Gesu' Children's Research Hospital, Rome, Italy; Departamento de Neurología Pediátrica (C.C.), Clínica Las Condes, Santiago, Chile; Paediatrics Department (D.C.), Hôpital de Hautepierre, Strasbourg, France; Neuromuscular Unit (J.C.), Neuropaediatrics Department, Institut de Recerca Hospital Universitari Sant Joan de Deu, Barcelona; Center for the Biomedical Research on Rare Diseases (CIBERER) (J.C.), ISCIII; Department of Neurology (M.L.C.), Hospital Clínico San Carlos, Instituto de Investigación Sanitaria San Carlos; Department of Medicine (M.L.C.), Universidad Complutense de Madrid, Spain; Department of Neurology (M.d.V.), Amsterdam University Medical Centre, Amsterdam Neuroscience, the Netherlands; Department of Pediatric Neurology (I.D.), Necker Enfants Malades Hospital, Paris Descartes University, France; Department of Child Neurology (N.G.), University Hospitals Leuven, Belgium; Department of Pediatric Neurology (A.K.), Center for Chronically Sick Children, Institute of Cell Biology and Neurobiology, Charité-Universitätsmedizin Berlin, Germany; Department of Neuropediatrics (E.L.), CHRU de Tours, Université François Rabelais de Tours, UMR INSERM U1253, Tours, France; Department of Neuropediatrics (J.L.), University Children's Hospital of Basel (UKBB), Switzerland; Centre de Référence des Maladies Neuromusculaires Nord/Est/Ile de France (E.M.), Neurology Department, Raymond-Poincaré Hospital, AP-HP, Garches; Centre de Référence des Maladies Neuromusculaires Nord/Est/Ile de France (M.M.), Service de Neuropédiatrie, Hôpital Trousseau, Paris, France; Department of Biomedical and Neuromotor Sciences (L.M.), University of Bologna, Italy; Réanimation Médicale, Physiologie-Explorations Fonctionnelles et Centre d'Investigation Clinique, UMR 1429 (D.O.), INSERM-UMR, 1179, UVSQ (D.O.), and Neuromuscular Unit, Department of Pediatric Neurology, Intensive Care and Rehabilitation, AP-HP, UVSQ Paris Saclay (B. Estournet, S.Q.-R.), Hôpital Raymond Poincaré, Garches, France; Department of Neurology (U.R.), Medizinische Fakultät Carl Gustav Carus Technische Universität Dresden, German; Division of Pediatric Neurology, Department of Pediatrics (M.A.S.), College of Medicine, King Saud University, Riyadh, Saudi Arabia; Friedrich-Baur-Institut (B.S.-W.), Department of Neurology, Ludwig-Maximilians-University of Munich; Department of Pediatric Neurology (M.S.), University of Tübingen, Germany; The John Walton Muscular Dystrophy Research Centre (V.S.), Institute of Genetic Medicine, Newcastle University, Newcastle Hospitals NHS Foundation Trust, UK; Department of Child Neurology (H.T.), Hacettepe University, School of Medicine, Ankara, Turkey; Centre de Compétence Neuromusculaire (J.A.U.), Hôpital Marin, Hendaye, France; Department of Neurology (A.v.d.K.), Amsterdam UMC, University of Amsterdam, Amsterdam Neuroscience, the Netherlands; Pediatrics and Adolescent Medicine, Division of Pediatric Neurology (E.W.), University Medical Center Göttingen, Georg-August University Göttingen, Germany; Neuromuscular and Neurogenetic Disorders of Childhood Section (C.G.B.), National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD; and Department of Pediatric Neurology (U.S.), Developmental Neurology and Social Pediatrics, University of Essen, Germany.

Objective: To clarify the prevalence, long-term natural history, and severity determinants of -related myopathy (SEPN1-RM), we analyzed a large international case series.

Methods: Retrospective clinical, histologic, and genetic analysis of 132 pediatric and adult patients (2-58 years) followed up for several decades.

Results: The clinical phenotype was marked by severe axial muscle weakness, spinal rigidity, and scoliosis (86.1%, from 8.9 ± 4 years), with relatively preserved limb strength and previously unreported ophthalmoparesis in severe cases. All patients developed respiratory failure (from 10.1±6 years), 81.7% requiring ventilation while ambulant. Histopathologically, 79 muscle biopsies showed large variability, partly determined by site of biopsy and age. Multi-minicores were the most common lesion (59.5%), often associated with mild dystrophic features and occasionally with eosinophilic inclusions. Identification of 65 mutations, including 32 novel ones and the first pathogenic copy number variation, unveiled exon 1 as the main mutational hotspot and revealed the first genotype-phenotype correlations, bi-allelic null mutations being significantly associated with disease severity ( = 0.017). SEPN1-RM was more severe and progressive than previously thought, leading to loss of ambulation in 10% of cases, systematic functional decline from the end of the third decade, and reduced lifespan even in mild cases. The main prognosis determinants were scoliosis/respiratory management, mutations, and body mass abnormalities, which correlated with disease severity. We propose a set of severity criteria, provide quantitative data for outcome identification, and establish a need for age stratification.

Conclusion: Our results inform clinical practice, improving diagnosis and management, and represent a major breakthrough for clinical trial readiness in this not so rare disease.
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http://dx.doi.org/10.1212/WNL.0000000000010327DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7713742PMC
September 2020

Biallelic loss of function variants in SYT2 cause a treatable congenital onset presynaptic myasthenic syndrome.

Am J Med Genet A 2020 10 10;182(10):2272-2283. Epub 2020 Aug 10.

Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.

Synaptotagmins are integral synaptic vesicle membrane proteins that function as calcium sensors and regulate neurotransmitter release at the presynaptic nerve terminal. Synaptotagmin-2 (SYT2), is the major isoform expressed at the neuromuscular junction. Recently, dominant missense variants in SYT2 have been reported as a rare cause of distal motor neuropathy and myasthenic syndrome, manifesting with stable or slowly progressive distal weakness of variable severity along with presynaptic NMJ impairment. These variants are thought to have a dominant-negative effect on synaptic vesicle exocytosis, although the precise pathomechanism remains to be elucidated. Here we report seven patients of five families, with biallelic loss of function variants in SYT2, clinically manifesting with a remarkably consistent phenotype of severe congenital onset hypotonia and weakness, with variable degrees of respiratory involvement. Electrodiagnostic findings were consistent with a presynaptic congenital myasthenic syndrome (CMS) in some. Treatment with an acetylcholinesterase inhibitor pursued in three patients showed clinical improvement with increased strength and function. This series further establishes SYT2 as a CMS-disease gene and expands its clinical and genetic spectrum to include recessive loss-of-function variants, manifesting as a severe congenital onset presynaptic CMS with potential treatment implications.
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http://dx.doi.org/10.1002/ajmg.a.61765DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7959540PMC
October 2020

GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.

Ann Neurol 2020 08 18;88(2):332-347. Epub 2020 Jun 18.

Botnar Research Centre, National Institute for Health Research Biomedical Research Centre Oxford, University of Oxford, Oxford, United Kingdom.

Objective: A hitherto undescribed phenotype of early onset muscular dystrophy associated with sensorineural hearing loss and primary ovarian insufficiency was initially identified in 2 siblings and in subsequent patients with a similar constellation of findings. The goal of this study was to understand the genetic and molecular etiology of this condition.

Methods: We applied whole exome sequencing (WES) superimposed on shared haplotype regions to identify the initial biallelic variants in GGPS1 followed by GGPS1 Sanger sequencing or WES in 5 additional families with the same phenotype. Molecular modeling, biochemical analysis, laser membrane injury assay, and the generation of a Y259C knock-in mouse were done.

Results: A total of 11 patients in 6 families carrying 5 different biallelic pathogenic variants in specific domains of GGPS1 were identified. GGPS1 encodes geranylgeranyl diphosphate synthase in the mevalonate/isoprenoid pathway, which catalyzes the synthesis of geranylgeranyl pyrophosphate, the lipid precursor of geranylgeranylated proteins including small guanosine triphosphatases. In addition to proximal weakness, all but one patient presented with congenital sensorineural hearing loss, and all postpubertal females had primary ovarian insufficiency. Muscle histology was dystrophic, with ultrastructural evidence of autophagic material and large mitochondria in the most severe cases. There was delayed membrane healing after laser injury in patient-derived myogenic cells, and a knock-in mouse of one of the mutations (Y259C) resulted in prenatal lethality.

Interpretation: The identification of specific GGPS1 mutations defines the cause of a unique form of muscular dystrophy with hearing loss and ovarian insufficiency and points to a novel pathway for this clinical constellation. ANN NEUROL 2020;88:332-347.
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http://dx.doi.org/10.1002/ana.25772DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7496979PMC
August 2020

Distinct effects on mRNA export factor GANP underlie neurological disease phenotypes and alter gene expression depending on intron content.

Hum Mol Genet 2020 06;29(9):1426-1439

Stem Cells and Metabolism Research Program, Research Programs Unit, University of Helsinki, 00290 Helsinki, Finland.

Defects in the mRNA export scaffold protein GANP, encoded by the MCM3AP gene, cause autosomal recessive early-onset peripheral neuropathy with or without intellectual disability. We extend here the phenotypic range associated with MCM3AP variants, by describing a severely hypotonic child and a sibling pair with a progressive encephalopathic syndrome. In addition, our analysis of skin fibroblasts from affected individuals from seven unrelated families indicates that disease variants result in depletion of GANP except when they alter critical residues in the Sac3 mRNA binding domain. GANP depletion was associated with more severe phenotypes compared with the Sac3 variants. Patient fibroblasts showed transcriptome alterations that suggested intron content-dependent regulation of gene expression. For example, all differentially expressed intronless genes were downregulated, including ATXN7L3B, which couples mRNA export to transcription activation by association with the TREX-2 and SAGA complexes. Our results provide insight into the molecular basis behind genotype-phenotype correlations in MCM3AP-associated disease and suggest mechanisms by which GANP defects might alter RNA metabolism.
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http://dx.doi.org/10.1093/hmg/ddaa051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7297229PMC
June 2020

Hypoglycemia in patients with congenital muscle disease.

BMC Pediatr 2020 02 6;20(1):57. Epub 2020 Feb 6.

Neuromuscular and Neurogenetic Disorders of Childhood Section, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Building 10, Room 2B 39, MSC 1477, 10 Center Drive, Bethesda, MD, 20892, USA.

Background: Only a few small studies have previously reported episodes of hypoglycemia in children with neuromuscular diseases; however, there has been no broader investigation into the occurrence of hypoglycemia in children with congenital muscle disease (CMD).

Methods: Pediatric patients enrolled in the CMD International Registry (CMDIR) with a history of hypoglycemia were included in this retrospective review. Hypoglycemic episodes and associated clinical and biochemical characteristics were characterized.

Results: Ten patients with CMD (5 with LAMA2-related muscular dystrophy) reported at least one episode of hypoglycemia beginning at an average age of 3.5 years. Predominant symptoms included altered mental status and nausea/vomiting, and laboratory studies demonstrated metabolic acidosis and ketonuria, consistent with ketotic hypoglycemia.

Conclusion: Patients with CMD may have an increased risk of hypoglycemia during fasting, illness, or stress due to their relatively low muscle mass and hence, paucity of gluconeogenic substrate. Clinicians should therefore maintain a high index of suspicion for hypoglycemia in this high-risk patient population and caregivers should routinely be trained to recognize and treat hypoglycemia.
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http://dx.doi.org/10.1186/s12887-020-1909-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7006143PMC
February 2020

Bile leakage after loop closure clip closure of the cystic duct during laparoscopic cholecystectomy: A retrospective analysis of a prospective cohort.

World J Gastrointest Surg 2020 Jan;12(1):9-16

Department of Research and Epidemiology, St. Antonius Hospital, Nieuwegein 3435 CM, Netherlands.

Background: Laparoscopic cholecystectomy (LC) is one of the most frequently performed surgical procedures. Cystic stump leakage is an underestimated, potentially life threatening complication that occurs in 1%-6% of the patients. With a secure cystic duct occlusion technique during LC, bile leakage becomes a preventable complication.

Aim: To investigate the effect of polydioxanone (PDS) loop closure of the cystic duct on bile leakage rate in LC patients.

Methods: In this retrospective analysis of a prospective cohort, the effect of PDS loop closure of the cystic duct on bile leakage complication was compared to patients with conventional clip closure. Logistic regression analysis was used to develop a risk score to identify bile leakage risk. Leakage rate was assessed for categories of patients with increasing levels of bile leakage risk.

Results: Of the 4359 patients who underwent LC, 136 (3%) underwent cystic duct closure by a PDS loop. Preoperatively, loop closure patients had significantly more complicated biliary disease compared to the clipped closure patients. In the loop closure cohort, zero (0%) bile leakage occurred compared to 59 of 4223 (1.4%) clip closure patients. For patients at increased bile leakage risk (risk score ≥ 1) rates were 1.6% and up to 13% (4/30) for clip closure patients with a risk score ≥ 4. This risk increase paralleled a stepwise increase of actual bile leakage complication for clip closure patients, which was not observed for loop closure patients.

Conclusion: Cystic duct closure with a PDS loop during LC may reduce bile leakage in patients at increased risk for bile leakage.
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http://dx.doi.org/10.4240/wjgs.v12.i1.9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6943090PMC
January 2020
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