Publications by authors named "Jill Urquhart"

62 Publications

Ligase IV syndrome can present with microcephaly and radial ray anomalies similar to Fanconi anaemia plus fatal kidney malformations.

Eur J Med Genet 2020 Sep 12;63(9):103974. Epub 2020 Jun 12.

Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK; Manchester Centre for Genomic Medicine, Manchester University NHS Foundation Trust, Manchester, UK. Electronic address:

Ligase IV (LIG4) syndrome is a rare disorder of DNA damage repair caused by biallelic, pathogenic variants in LIG4. This is a phenotypically heterogeneous condition with clinical presentation varying from lymphoreticular malignancies in developmentally normal individuals to significant microcephaly, primordial dwarfism, radiation hypersensitivity, severe combined immunodeficiency and early mortality. Renal defects have only rarely been described as part of the ligase IV disease spectrum. We identified a consanguineous family where three siblings presenting with antenatal growth retardation, microcephaly, severe renal anomalies and skeletal abnormalities, including radial ray defects. Autozygosity mapping and exome sequencing identified a novel homozygous frameshift variant in LIG4, c.597_600delTCAG, p.(Gln200LysfsTer33), which segregated in the family. LIG4 is encoded by a single exon and so this frameshift variant is predicted to result in a protein truncated by 678 amino acids. This is the shortest predicted LIG4 protein product reported and correlates with the most severe clinical phenotype described to date. We note the clinical overlap with Fanconi anemia and suggest that LIG4 syndrome is considered in the differential diagnosis of this severe developmental disorder.
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http://dx.doi.org/10.1016/j.ejmg.2020.103974DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7445424PMC
September 2020

A homozygous missense variant in CHRM3 associated with familial urinary bladder disease.

Clin Genet 2019 12 11;96(6):515-520. Epub 2019 Sep 11.

Manchester Centre for Genomic Medicine, Manchester University NHS Foundation Trust, Health Innovation Manchester, Manchester, UK.

CHRM3 codes for the M3 muscarinic acetylcholine receptor that is located on the surface of smooth muscle cells of the detrusor, the muscle that effects urinary voiding. Previously, we reported brothers in a family affected by a congenital prune belly-like syndrome with mydriasis due to homozygous CHRM3 frameshift variants. In this study, we describe two sisters with bladders that failed to empty completely and pupils that failed to constrict fully in response to light, who are homozygous for the missense CHRM3 variant c.352G > A; p.(Gly118Arg). Samples were not available for genotyping from their brother, who had a history of multiple urinary tract infections and underwent surgical bladder draining in the first year of life. He died at the age of 6 years. This is the first independent report of biallelic variants in CHRM3 in a family with a rare serious bladder disorder associated with mydriasis and provides important evidence of this association.
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http://dx.doi.org/10.1111/cge.13631DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6899476PMC
December 2019

Expanding the genetic and phenotypic spectrum of branched-chain amino acid transferase 2 deficiency.

J Inherit Metab Dis 2019 09 1;42(5):809-817. Epub 2019 Aug 1.

Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester University NHS Foundation Trust, Health Innovation Manchester, Manchester, UK.

The first step in branched-chain amino acid (BCAA) catabolism is catalyzed by the two BCAA transferase isoenzymes, cytoplasmic branched-chain amino acid transferase (BCAT) 1, and mitochondrial BCAT2. Defects in the second step of BCAA catabolism cause maple syrup urine disease (MSUD), a condition which has been far more extensively investigated. Here, we studied the consequences of BCAT2 deficiency, an ultra-rare condition in humans. We present genetic, clinical, and functional data in five individuals from four different families with homozygous or compound heterozygous BCAT2 mutations which were all detected following abnormal biochemical profile results or familial mutation segregation studies. We demonstrate that BCAT2 deficiency has a recognizable biochemical profile with raised plasma BCAAs and, in contrast with MSUD, low-normal branched-chain keto acids (BCKAs) with undetectable l-allo-isoleucine. Interestingly, unlike in MSUD, none of the individuals with BCAT2 deficiency developed acute encephalopathy even with exceptionally high BCAA levels. We observed wide-ranging clinical phenotypes in individuals with BCAT2 deficiency. While one adult was apparently asymptomatic, three individuals had presented with developmental delay and autistic features. We show that the biochemical characteristics of BCAT2 deficiency may be amenable to protein-restricted diet and that early treatment may improve outcome in affected individuals. BCAT2 deficiency is an inborn error of BCAA catabolism. At present, it is unclear whether developmental delay and autism are parts of the variable phenotypic spectrum of this condition or coincidental. Further studies will be required to explore this.
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http://dx.doi.org/10.1002/jimd.12135DOI Listing
September 2019

Variants in myelin regulatory factor (MYRF) cause autosomal dominant and syndromic nanophthalmos in humans and retinal degeneration in mice.

PLoS Genet 2019 05 2;15(5):e1008130. Epub 2019 May 2.

Department of Ophthalmology and Visual Sciences, W.K. Kellogg Eye Center, University of Michigan, Ann Arbor, MI, United States of America.

Nanophthalmos is a rare, potentially devastating eye condition characterized by small eyes with relatively normal anatomy, a high hyperopic refractive error, and frequent association with angle closure glaucoma and vision loss. The condition constitutes the extreme of hyperopia or farsightedness, a common refractive error that is associated with strabismus and amblyopia in children. NNO1 was the first mapped nanophthalmos locus. We used combined pooled exome sequencing and strong linkage data in the large family used to map this locus to identify a canonical splice site alteration upstream of the last exon of the gene encoding myelin regulatory factor (MYRF c.3376-1G>A), a membrane bound transcription factor that undergoes autoproteolytic cleavage for nuclear localization. This variant produced a stable RNA transcript, leading to a frameshift mutation p.Gly1126Valfs*31 in the C-terminus of the protein. In addition, we identified an early truncating MYRF frameshift mutation, c.769dupC (p.S264QfsX74), in a patient with extreme axial hyperopia and syndromic features. Myrf conditional knockout mice (CKO) developed depigmentation of the retinal pigment epithelium (RPE) and retinal degeneration supporting a role of this gene in retinal and RPE development. Furthermore, we demonstrated the reduced expression of Tmem98, another known nanophthalmos gene, in Myrf CKO mice, and the physical interaction of MYRF with TMEM98. Our study establishes MYRF as a nanophthalmos gene and uncovers a new pathway for eye growth and development.
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http://dx.doi.org/10.1371/journal.pgen.1008130DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6527243PMC
May 2019

De Novo Pathogenic Variants in CACNA1E Cause Developmental and Epileptic Encephalopathy with Contractures, Macrocephaly, and Dyskinesias.

Authors:
Katherine L Helbig Robert J Lauerer Jacqueline C Bahr Ivana A Souza Candace T Myers Betül Uysal Niklas Schwarz Maria A Gandini Sun Huang Boris Keren Cyril Mignot Alexandra Afenjar Thierry Billette de Villemeur Delphine Héron Caroline Nava Stéphanie Valence Julien Buratti Christina R Fagerberg Kristina P Soerensen Maria Kibaek Erik-Jan Kamsteeg David A Koolen Boudewijn Gunning H Jurgen Schelhaas Michael C Kruer Jordana Fox Somayeh Bakhtiari Randa Jarrar Sergio Padilla-Lopez Kristin Lindstrom Sheng Chih Jin Xue Zeng Kaya Bilguvar Antigone Papavasileiou Qinghe Xing Changlian Zhu Katja Boysen Filippo Vairo Brendan C Lanpher Eric W Klee Jan-Mendelt Tillema Eric T Payne Margot A Cousin Teresa M Kruisselbrink Myra J Wick Joshua Baker Eric Haan Nicholas Smith Azita Sadeghpour Erica E Davis Nicholas Katsanis Mark A Corbett Alastair H MacLennan Jozef Gecz Saskia Biskup Eva Goldmann Lance H Rodan Elizabeth Kichula Eric Segal Kelly E Jackson Alexander Asamoah David Dimmock Julie McCarrier Lorenzo D Botto Francis Filloux Tatiana Tvrdik Gregory D Cascino Sherry Klingerman Catherine Neumann Raymond Wang Jessie C Jacobsen Melinda A Nolan Russell G Snell Klaus Lehnert Lynette G Sadleir Britt-Marie Anderlid Malin Kvarnung Renzo Guerrini Michael J Friez Michael J Lyons Jennifer Leonhard Gabriel Kringlen Kari Casas Christelle M El Achkar Lacey A Smith Alexander Rotenberg Annapurna Poduri Alba Sanchis-Juan Keren J Carss Julia Rankin Adam Zeman F Lucy Raymond Moira Blyth Bronwyn Kerr Karla Ruiz Jill Urquhart Imelda Hughes Siddharth Banka Ulrike B S Hedrich Ingrid E Scheffer Ingo Helbig Gerald W Zamponi Holger Lerche Heather C Mefford
March 2019

A patient with a novel CNTNAP2 homozygous variant: further delineation of the CASPR2 deficiency syndrome and review of the literature.

Clin Dysmorphol 2019 Apr;28(2):66-70

Manchester Centre for Genomic Medicine, St Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust Manchester Academic Health Sciences Centre.

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http://dx.doi.org/10.1097/MCD.0000000000000259DOI Listing
April 2019

22q11.2 duplications in a UK cohort with bladder exstrophy-epispadias complex.

Am J Med Genet A 2019 03 9;179(3):404-409. Epub 2019 Jan 9.

Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom.

The bladder exstrophy-epispadias complex (BEEC) comprises of a spectrum of anterior midline defects, all affecting the lower urinary tract, the external genitalia, and the bony pelvis. In extreme cases, the gastrointestinal tract is also affected. The pathogenesis of BEEC is unclear but chromosomal aberrations have been reported. In particular, duplications of 22q11.2 have been identified in eight unrelated individuals with BEEC. The current study aimed to identify chromosomal copy number variants in BEEC. Analyses was performed using the Affymetrix Genome-wide SNP6.0 assay in 92 unrelated patients cared for by two UK pediatric urology centers. Three individuals had a 22q11.2 duplication, a significantly higher number than that found in a control group of 12,500 individuals with developmental delay who had undergone microarray testing (p < .0001). Sequencing of CRKL, implicated in renal tract malformations in DiGeorge syndrome critical region at 22q11, in 89 individuals with BEEC lacking 22q11 duplications revealed no pathogenic variants. To date, 22q11.2 duplication is the genetic variant most commonly associated with BEEC. This is consistent with the hypothesis that altered expression of a single, yet to be defined, gene therein is critical to the pathogenesis of this potentially devastating congenital disorder.
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http://dx.doi.org/10.1002/ajmg.a.61032DOI Listing
March 2019

De Novo Pathogenic Variants in CACNA1E Cause Developmental and Epileptic Encephalopathy with Contractures, Macrocephaly, and Dyskinesias.

Authors:
Katherine L Helbig Robert J Lauerer Jacqueline C Bahr Ivana A Souza Candace T Myers Betül Uysal Niklas Schwarz Maria A Gandini Sun Huang Boris Keren Cyril Mignot Alexandra Afenjar Thierry Billette de Villemeur Delphine Héron Caroline Nava Stéphanie Valence Julien Buratti Christina R Fagerberg Kristina P Soerensen Maria Kibaek Erik-Jan Kamsteeg David A Koolen Boudewijn Gunning H Jurgen Schelhaas Michael C Kruer Jordana Fox Somayeh Bakhtiari Randa Jarrar Sergio Padilla-Lopez Kristin Lindstrom Sheng Chih Jin Xue Zeng Kaya Bilguvar Antigone Papavasileiou Qinghe Xing Changlian Zhu Katja Boysen Filippo Vairo Brendan C Lanpher Eric W Klee Jan-Mendelt Tillema Eric T Payne Margot A Cousin Teresa M Kruisselbrink Myra J Wick Joshua Baker Eric Haan Nicholas Smith Azita Sadeghpour Erica E Davis Nicholas Katsanis Mark A Corbett Alastair H MacLennan Jozef Gecz Saskia Biskup Eva Goldmann Lance H Rodan Elizabeth Kichula Eric Segal Kelly E Jackson Alexander Asamoah David Dimmock Julie McCarrier Lorenzo D Botto Francis Filloux Tatiana Tvrdik Gregory D Cascino Sherry Klingerman Catherine Neumann Raymond Wang Jessie C Jacobsen Melinda A Nolan Russell G Snell Klaus Lehnert Lynette G Sadleir Britt-Marie Anderlid Malin Kvarnung Renzo Guerrini Michael J Friez Michael J Lyons Jennifer Leonhard Gabriel Kringlen Kari Casas Christelle M El Achkar Lacey A Smith Alexander Rotenberg Annapurna Poduri Alba Sanchis-Juan Keren J Carss Julia Rankin Adam Zeman F Lucy Raymond Moira Blyth Bronwyn Kerr Karla Ruiz Jill Urquhart Imelda Hughes Siddharth Banka Ulrike B S Hedrich Ingrid E Scheffer Ingo Helbig Gerald W Zamponi Holger Lerche Heather C Mefford

Am J Hum Genet 2018 11 18;103(5):666-678. Epub 2018 Oct 18.

Division of Genetic Medicine, University of Washington, Seattle, WA 98195, USA. Electronic address:

Developmental and epileptic encephalopathies (DEEs) are severe neurodevelopmental disorders often beginning in infancy or early childhood that are characterized by intractable seizures, abundant epileptiform activity on EEG, and developmental impairment or regression. CACNA1E is highly expressed in the central nervous system and encodes the α-subunit of the voltage-gated Ca2.3 channel, which conducts high voltage-activated R-type calcium currents that initiate synaptic transmission. Using next-generation sequencing techniques, we identified de novo CACNA1E variants in 30 individuals with DEE, characterized by refractory infantile-onset seizures, severe hypotonia, and profound developmental impairment, often with congenital contractures, macrocephaly, hyperkinetic movement disorders, and early death. Most of the 14, partially recurring, variants cluster within the cytoplasmic ends of all four S6 segments, which form the presumed Ca2.3 channel activation gate. Functional analysis of several S6 variants revealed consistent gain-of-function effects comprising facilitated voltage-dependent activation and slowed inactivation. Another variant located in the domain II S4-S5 linker results in facilitated activation and increased current density. Five participants achieved seizure freedom on the anti-epileptic drug topiramate, which blocks R-type calcium channels. We establish pathogenic variants in CACNA1E as a cause of DEEs and suggest facilitated R-type calcium currents as a disease mechanism for human epilepsy and developmental disorders.
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http://dx.doi.org/10.1016/j.ajhg.2018.09.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6216110PMC
November 2018

Marfanoid habitus is a nonspecific feature of Perrault syndrome.

Clin Dysmorphol 2017 Oct;26(4):200-204

aCenter for Human Genomics, Faculty of Medicine and Pharmacy bDepartment of Endocrinology, Diabetology and Nutrition, Avicenna Hospital, Mohammed V University cDepartment of Medical Genetics, National Institute of Health, Rabat, Morocco dDivision of Evolution and Genomic Sciences, Faculty of Biology, Medicine and Health, School of Biological Sciences, University of Manchester eManchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK.

The objective of this study was to report the clinical and biological characteristics of two Perrault syndrome cases in a Moroccan family with homozygous variant c.1565C>A in the LARS2 gene and to establish genotype-phenotype correlation of patients with the same mutation by review of the literature. Whole-exome sequencing was performed. Data analysis was carried out and confirmed by Sanger sequencing and segregation. The affected siblings were diagnosed as having Perrault syndrome with sensorineural hearing loss at low frequencies; the female proband had primary amenorrhea and ovarian dysgenesis. Both affected individuals had a marfanoid habitus and no neurological features. Both patients carried the homozygous variant c.1565C>A; p.Thr522Asn in exon 13 of the LARS2 gene. This variant has already been reported as a homozygous variant in three other Perrault syndrome families. Both affected siblings of a Moroccan consanguineous family with LARS2 variants had low-frequency sensorineural hearing loss, marfanoid habitus, and primary ovarian insufficiency in the affected girl. According to the literature, this variant, c.1565C>A; p.Thr522Asn, can be correlated with low-frequency hearing loss. However, marfanoid habitus was been considered a nonspecific feature in Perrault syndrome, but we believe that it may be more specific than considered previously. This diagnosis allowed us to provide appropriate management to the patients and to provide more accurate genetic counseling to this family.
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http://dx.doi.org/10.1097/MCD.0000000000000198DOI Listing
October 2017

Confirmation that mutations in DDX59 cause an autosomal recessive form of oral-facial-digital syndrome: Further delineation of the DDX59 phenotype in two new families.

Eur J Med Genet 2017 Oct 12;60(10):527-532. Epub 2017 Jul 12.

Manchester Centre for Genomic Medicine, University of Manchester, St Mary's Hospital, Manchester, M13 9WL, United Kingdom; Division of Evolution and Genomic Sciences, School of Biological Sciences, University of Manchester, M13 9PL, United Kingdom.

We report three probands from two unrelated consanguineous families of South Asian origin who all carry the same rare novel homozygous variant within the dead box helicase gene DDX59 in association with features of oral-facial-digital syndrome (OFDS). DDX59 variants have been reported previously in an unclassified, autosomal recessive form of OFDS; clinically associated with features including tongue lobulation, cleft palate, frontal bossing, hypertelorism and postaxial polydactyly. All three probands had lobulated tongues with tongue hamartomas, abnormal tongue tip, developmental delay and microcephaly, with just one proband demonstrating polydactlyly. The novel DDX59 variant was identified through autozygosity studies followed by sequencing of homozygous regions identified. It affects a stop codon, extending the protein product and is therefore predicted to be pathogenic. It is only the third reported DDX59 mutation associated with OFDS reported so far.
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http://dx.doi.org/10.1016/j.ejmg.2017.07.009DOI Listing
October 2017

Diagnosing childhood-onset inborn errors of metabolism by next-generation sequencing.

Arch Dis Child 2017 11 3;102(11):1019-1029. Epub 2017 May 3.

Manchester Centre for Genomic Medicine, St. Mary's Hospital, Central Manchester NHS Trust, Manchester Academic Health Science Centre, Manchester, UK.

Background: Inborn errors of metabolism (IEMs) underlie a substantial proportion of paediatric disease burden but their genetic diagnosis can be challenging using the traditional approaches.

Methods: We designed and validated a next-generation sequencing (NGS) panel of 226 IEM genes, created six overlapping phenotype-based subpanels and tested 102 individuals, who presented clinically with suspected childhood-onset IEMs.

Results: In 51/102 individuals, NGS fully or partially established the molecular cause or identified other actionable diagnoses. Causal mutations were identified significantly more frequently when the biochemical phenotype suggested a specific IEM or a group of IEMs (p<0.0001), demonstrating the pivotal role of prior biochemical testing in guiding NGS analysis. The NGS panel helped to avoid further invasive, hazardous, lengthy or expensive investigations in 69% individuals (p<0.0001). Additional functional testing due to novel or unexpected findings had to be undertaken in only 3% of subjects, demonstrating that the use of NGS does not significantly increase the burden of subsequent follow-up testing. Even where a molecular diagnosis could not be achieved, NGS-based approach assisted in the management and counselling by reducing the likelihood of a high-penetrant genetic cause.

Conclusion: NGS has significant clinical utility for the diagnosis of IEMs. Biochemical testing and NGS analysis play complementary roles in the diagnosis of IEMs. Incorporating NGS into the diagnostic algorithm of IEMs can improve the accuracy of diagnosis.
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http://dx.doi.org/10.1136/archdischild-2017-312738DOI Listing
November 2017

Phenotypic Heterogeneity in a Congenital Disorder of Glycosylation Caused by Mutations in STT3A.

J Child Neurol 2017 05 16;32(6):560-565. Epub 2017 Mar 16.

3 Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK.

STT3A encodes the catalytic subunit of the oligosaccharyltransferase complex. A congenital disorder of glycosylation caused by mutations in STT3A has only been reported in one family to date, associated with a Type I congenital disorder of glycosylation pattern of transferrin glycoforms. The authors describe a further 5 related individuals with a likely pathogenic variant in STT3A, 2 of whom also had variants in TUSC3. Common phenotypic features in all symptomatic individuals include developmental delay, intellectual disability, with absent speech and seizures. Two individuals also developed episodic hypothermia and altered consciousness. The family were investigated by autozygosity mapping, which revealed both a homozygous region containing STT3A and, in addition, a homozygous deletion of TUSC3 in one child. A likely pathogenic variant in STT3A was confirmed on Sanger sequencing of all affected individuals: the authors discuss the molecular findings in detail and further delineate the clinical phenotype of this rare disorder.
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http://dx.doi.org/10.1177/0883073817696816DOI Listing
May 2017

Homozygous mutation in PTRH2 gene causes progressive sensorineural deafness and peripheral neuropathy.

Am J Med Genet A 2017 Apr;173(4):1051-1055

Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.

PTRH2 is an evolutionarily highly conserved mitochondrial protein that belongs to a family of peptidyl-tRNA hydrolases. Recently, patients from two consanguineous families with mutations in the PTRH2 gene were reported. Global developmental delay associated with microcephaly, growth retardation, progressive ataxia, distal muscle weakness with ankle contractures, demyelinating sensorimotor neuropathy, and sensorineural hearing loss were present in all patients, while facial dysmorphism with widely spaced eyes, exotropia, thin upper lip, proximally placed thumbs, and deformities of the fingers and toes were present in some individuals. Here, we report a new family with three siblings affected by sensorineural hearing loss and peripheral neuropathy. Autozygosity mapping followed by exome sequencing identified a previously reported homozygous missense mutation in PTRH2 (c.254A>C; p.(Gln85Pro)). Sanger sequencing confirmed that the variant segregated with the phenotype. In contrast to the previously reported patient, the affected siblings had normal intelligence, milder microcephaly, delayed puberty, myopia, and moderate insensitivity to pain. Our findings expand the clinical phenotype and further demonstrate the clinical heterogeneity related to PTRH2 variants.
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http://dx.doi.org/10.1002/ajmg.a.38140DOI Listing
April 2017

Severe intellectual disability in a patient with Burn-McKeown syndrome.

Clin Dysmorphol 2017 Jul;26(3):193-194

aManchester Centre for Genomic Medicine, St Mary's Hospital, Central Manchester University Hospitals, NHS Foundation Trust Manchester Academic Health Sciences Centre bDivision of Evolution and Genomic Sciences, School of Biological Sciences, University of Manchester, Manchester, UK cThe Folkhaelsan Department of Medical Genetics dChildren's Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland.

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http://dx.doi.org/10.1097/MCD.0000000000000175DOI Listing
July 2017

Novel PEX11B Mutations Extend the Peroxisome Biogenesis Disorder 14B Phenotypic Spectrum and Underscore Congenital Cataract as an Early Feature.

Invest Ophthalmol Vis Sci 2017 01;58(1):594-603

Manchester Centre for Genomic Medicine, Division of Evolution and Genomic Sciences, Faculty of Biology, Medicines and Health, The University of Manchester, Manchester Academic Health Science Centre (MAHSC), Saint Mary's Hospital, Manchester, United Kingdom 3Manchester Centre for Genomic Medicine, Central Manchester University Hospitals National Health Service (NHS) Foundation Trust, MAHSC, Saint Mary's Hospital, Manchester, United Kingdom.

Purpose: Peroxisomes perform complex metabolic and catabolic functions essential for normal growth and development. Mutations in 14 genes cause a spectrum of peroxisomal disease in humans. Most recently, PEX11B was associated with an atypical peroxisome biogenesis disorder (PBD) in a single individual. In this study, we identify further PEX11B cases and delineate associated phenotypes.

Methods: Probands from three families underwent next generation sequencing (NGS) for diagnosis of a multisystem developmental disorder. Autozygosity mapping was conducted in one affected sibling pair. ExomeDepth was used to identify copy number variants from NGS data and confirmed by dosage analysis. Biochemical profiling was used to investigate the metabolic signature of the condition.

Results: All patients presented with bilateral cataract at birth but the systemic phenotype was variable, including short stature, skeletal abnormalities, and dysmorphism-features not described in the original case. Next generation sequencing identified biallelic loss-of-function mutations in PEX11B as the underlying cause of disease in each case (PEX11B c.235C>T p.(Arg79Ter) homozygous; PEX11B c.136C>T p.(Arg46Ter) homozygous; PEX11B c.595C>T p.(Arg199Ter) heterozygous, PEX11B ex1-3 del heterozygous). Biochemical studies identified very low plasmalogens in one patient, whilst a mildly deranged very long chain fatty acid profile was found in another.

Conclusions: Our findings expand the phenotypic spectrum of the condition and underscore congenital cataract as the consistent primary presenting feature. We also find that biochemical measurements of peroxisome function may be disturbed in some cases. Furthermore, diagnosis by NGS is proficient and may circumvent the requirement for an invasive skin biopsy for disease identification from fibroblast cells.
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http://dx.doi.org/10.1167/iovs.16-21026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5841568PMC
January 2017

ORAI1 Mutations with Distinct Channel Gating Defects in Tubular Aggregate Myopathy.

Hum Mutat 2017 04 2;38(4):426-438. Epub 2017 Feb 2.

Departement of Translational Medicine and Neurogenetics, IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Illkirch, France.

Calcium (Ca ) is a physiological key factor, and the precise modulation of free cytosolic Ca levels regulates multiple cellular functions. Store-operated Ca entry (SOCE) is a major mechanism controlling Ca homeostasis, and is mediated by the concerted activity of the Ca sensor STIM1 and the Ca channel ORAI1. Dominant gain-of-function mutations in STIM1 or ORAI1 cause tubular aggregate myopathy (TAM) or Stormorken syndrome, whereas recessive loss-of-function mutations are associated with immunodeficiency. Here, we report the identification and functional characterization of novel ORAI1 mutations in TAM patients. We assess basal activity and SOCE of the mutant ORAI1 channels, and we demonstrate that the G98S and V107M mutations generate constitutively permeable ORAI1 channels, whereas T184M alters the channel permeability only in the presence of STIM1. These data indicate a mutation-dependent pathomechanism and a genotype/phenotype correlation, as the ORAI1 mutations associated with the most severe symptoms induce the strongest functional cellular effect. Examination of the non-muscle features of our patients strongly suggests that TAM and Stormorken syndrome are spectra of the same disease. Overall, our results emphasize the importance of SOCE in skeletal muscle physiology, and provide new insights in the pathomechanisms involving aberrant Ca homeostasis and leading to muscle dysfunction.
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http://dx.doi.org/10.1002/humu.23172DOI Listing
April 2017

Non lethal Raine syndrome and differential diagnosis.

Eur J Med Genet 2016 Nov 22;59(11):577-583. Epub 2016 Sep 22.

Centre de Génomique Humaine, Faculté de Médecine et de Pharmacie, Université Mohammed V Souissi, Rabat, Morocco; Département de Génétique Médicale, Institut National d'Hygiène, Rabat, Morocco.

Raine syndrome is a rare autosomal recessive bone dysplasia characterized by characteristic facial features with exophthalmos and generalized osteosclerosis. Amelogenesis imperfecta, hearing loss, seizures, and intracerebral calcification are apparent in some affected individuals. Originally, Raine syndrome was originally reported as a lethal syndrome. However, recently a milder phenotype, compatible with life, has been described. Biallelic variants inFAM20C, encoding aGolgi casein kinase involved in biomineralisation, have been identified in affected individuals. We report here a consanguineous Moroccan family with two affected siblingsa girl aged 18 and a boy of 15years. Clinical features, including learning disability, seizures and amelogenesis imperfecta, initially suggested a diagnosis of Kohlschutter-Tonz syndrome. However,a novel homozygous FAM20Cvariantc.676T > A, p.(Trp226Arg) was identified in the affected siblings. Our report reinforces that Raine syndrome is compatible with life, and that mild hypophosphatemia and amelogenesis imperfecta are key features of the attenuated form.
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http://dx.doi.org/10.1016/j.ejmg.2016.09.018DOI Listing
November 2016

Mutations in SNORD118 cause the cerebral microangiopathy leukoencephalopathy with calcifications and cysts.

Nat Genet 2016 10 29;48(10):1185-92. Epub 2016 Aug 29.

Faculty of Biology, Medicine and Health, School of Biological Sciences, Division of Evolution and Genomic Sciences, University of Manchester, Manchester, UK.

Although ribosomes are ubiquitous and essential for life, recent data indicate that monogenic causes of ribosomal dysfunction can confer a remarkable degree of specificity in terms of human disease phenotype. Box C/D small nucleolar RNAs (snoRNAs) are evolutionarily conserved non-protein-coding RNAs involved in ribosome biogenesis. Here we show that biallelic mutations in the gene SNORD118, encoding the box C/D snoRNA U8, cause the cerebral microangiopathy leukoencephalopathy with calcifications and cysts (LCC), presenting at any age from early childhood to late adulthood. These mutations affect U8 expression, processing and protein binding and thus implicate U8 as essential in cerebral vascular homeostasis.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5045717PMC
http://dx.doi.org/10.1038/ng.3661DOI Listing
October 2016

Exploring the genetic basis of 3MC syndrome: Findings in 12 further families.

Am J Med Genet A 2016 May 20;170A(5):1216-24. Epub 2016 Jan 20.

Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, MAHSC, Manchester, United Kingdom.

The 3MC syndromes are a group of rare autosomal recessive disorders where the main clinical features are cleft lip and palate, hypertelorism, highly arched eyebrows, caudal appendage, postnatal growth deficiency, and genitourinary tract anomalies. Ophthalmological abnormalities, most notably anterior chamber defects may also be seen. We describe the clinical and molecular findings in 13 individuals with suspected 3MC syndrome from 12 previously unreported families. The exclusion of the MASP1 and COLEC11 Loci in two individuals from different consanguineous families and the absence of mutations in four further individuals sequenced for both genes raises the possibility that that there is further genetic heterogeneity of 3MC syndrome.
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http://dx.doi.org/10.1002/ajmg.a.37564DOI Listing
May 2016

The Contribution of Whole Gene Deletions and Large Rearrangements to the Mutation Spectrum in Inherited Tumor Predisposing Syndromes.

Hum Mutat 2016 Mar 11;37(3):250-6. Epub 2016 Jan 11.

Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester Academic Health Sciences Centre (MAHSC), University of Manchester, Manchester, M13 9WL, UK.

Heterozygous whole gene deletions (WGDs), and intragenic microdeletions, account for a significant proportion of mutations underlying cancer predisposition syndromes. We analyzed the frequency and genotype-phenotype correlations of microdeletions in 12 genes (BRCA1, BRCA2, TP53, MSH2, MLH1, MSH6, PMS2, NF1, NF2, APC, PTCH1, and VHL) representing seven tumor predisposition syndromes in 5,897 individuals (2,611 families) from our center. Overall, microdeletions accounted for 14% of identified mutations. As expected, smaller deletions or duplications were more common (12%) than WGDs (2.2%). Where a WGD was identified in the germline in NF2, the mechanism of somatic second hit was not deletion, as previously described for NF1. For neurofibromatosis type 1 and 2, we compared the mechanism of germline deletion. Unlike NF1, where three specific deletion sizes account for most germline WGDs, NF2 deletion breakpoints were different across seven samples tested. One of these deletions was 3.93 Mb and conferred a severe phenotype, thus refining the region for a potential NF2 modifier gene to a 2.04-Mb region on chromosome 22. The milder phenotype of NF2 WGDs may be due to the apparent absence of chromosome 22 loss as the second hit. These observations of WGD phenotypes will be helpful for interpreting incidental findings from microarray analysis and next-generation sequencing.
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http://dx.doi.org/10.1002/humu.22938DOI Listing
March 2016

Heimler Syndrome Is Caused by Hypomorphic Mutations in the Peroxisome-Biogenesis Genes PEX1 and PEX6.

Am J Hum Genet 2015 Oct 17;97(4):535-45. Epub 2015 Sep 17.

Department of Medical Genetics, University of Antwerp, Antwerp 2610, Belgium. Electronic address:

Heimler syndrome (HS) is a rare recessive disorder characterized by sensorineural hearing loss (SNHL), amelogenesis imperfecta, nail abnormalities, and occasional or late-onset retinal pigmentation. We ascertained eight families affected by HS and, by using a whole-exome sequencing approach, identified biallelic mutations in PEX1 or PEX6 in six of them. Loss-of-function mutations in both genes are known causes of a spectrum of autosomal-recessive peroxisome-biogenesis disorders (PBDs), including Zellweger syndrome. PBDs are characterized by leukodystrophy, hypotonia, SNHL, retinopathy, and skeletal, craniofacial, and liver abnormalities. We demonstrate that each HS-affected family has at least one hypomorphic allele that results in extremely mild peroxisomal dysfunction. Although individuals with HS share some subtle clinical features found in PBDs, the diagnosis was not suggested by routine blood and skin fibroblast analyses used to detect PBDs. In conclusion, our findings define HS as a mild PBD, expanding the pleiotropy of mutations in PEX1 and PEX6.
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http://dx.doi.org/10.1016/j.ajhg.2015.08.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4596894PMC
October 2015

Deletion of 19q13 reveals clinical overlap with Dubowitz syndrome.

J Hum Genet 2015 Dec 17;60(12):781-5. Epub 2015 Sep 17.

Manchester Centre for Genomic Medicine, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Science Centre (MAHSC), Manchester, UK.

Dubowitz syndrome is a presumed autosomal recessive disorder characterized by multiple congenital abnormalities: microcephaly, learning and developmental delay, growth failure, and a predisposition to allergies and eczema. There have been more than 150 individuals reported to have this diagnosis, but no unifying genetic alteration has been identified indicating genetic heterogeneity. We report on a pair of monozygotic twins diagnosed clinically with Dubowitz syndrome by Professor Dubowitz over 30 years ago and identified to have a de novo heterozygous 3.2-Mb deletion at 19q13.11q13.12. Exome sequencing did not identify either a putative pathogenic variant on the trans allele supporting recessive inheritance or any other causative sequence variants. Comparison of the phenotype in our cases shows considerable overlap with the 19q13.11 microdeletion syndrome, suggesting that a subset of individuals diagnosed with Dubowitz syndrome may be due to deletions at 19q13. Our finding further reinforces the genetic and phenotypic heterogeneity of Dubowitz syndrome.
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http://dx.doi.org/10.1038/jhg.2015.111DOI Listing
December 2015

Next-generation Sequencing in the Diagnosis of Metabolic Disease Marked by Pediatric Cataract.

Ophthalmology 2016 Jan 30;123(1):217-20. Epub 2015 Jul 30.

Manchester Centre for Genomic Medicine, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Science Centre (MAHSC), Saint Mary's Hospital, Manchester, UK; Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, MAHSC, Saint Mary's Hospital, Manchester, UK. Electronic address:

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http://dx.doi.org/10.1016/j.ophtha.2015.06.035DOI Listing
January 2016

Oculo-auriculo-vertebral spectrum: clinical and molecular analysis of 51 patients.

Eur J Med Genet 2015 Sep 20;58(9):455-65. Epub 2015 Jul 20.

Manchester Centre for Genomic Medicine, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester, Manchester, UK; Central Manchester University Hospitals NHS Foundation Trust as part of Manchester Academic Health Science Centre (MAHSC), Manchester, UK. Electronic address:

Introduction: Oculo-auriculo-vertebral spectrum (OAVS OMIM 164210) is a craniofacial developmental disorder affecting the development of the structures derived from the 1st and the 2nd branchial arches during embryogenesis, with consequential maxillary, mandibular, and ear abnormalities. The phenotype in OAVS is variable and associated clinical features can involve the cardiac, renal, skeletal, and central nervous systems. Its aetiology is still poorly understood.

Methods: We have evaluated the clinical phenotypes of 51 previously unpublished patients with OAVS and their parents, and performed comparative genomic hybridization microarray studies to identify potential causative loci.

Results: Of all 51 patients, 16 (31%) had a family history of OAVS. Most had no relevant pre-natal history and only 5 (10%) cases had a history of environmental exposures that have previously been described as risk factors for OAVS. In 28 (55%) cases, the malformations were unilateral. When the involvement was bilateral, it was asymmetric. Ear abnormalities were present in 47 (92%) patients (unilateral in 24; and bilateral in 23). Hearing loss was common (85%), mostly conductive, but also sensorineural, or a combination of both. Hemifacial microsomia was present in 46 (90%) patients (17 also presented facial nerve palsy). Ocular anomalies were present in 15 (29%) patients. Vertebral anomalies were confirmed in 10 (20%) cases; 50% of those had additional heart, brain and/or other organ abnormalities. Brain abnormalities were present in 5 (10%) patients; developmental delay was more common among these patients. Limb abnormalities were found in 6 (12%) patients, and urogenital anomalies in 5 (10%). Array-CGH analysis identified 22q11 dosage anomalies in 10 out of 22 index cases screened.

Discussion: In this study we carried out in-depth phenotyping of OAVS in a large, multicentre cohort. Clinical characteristics are in line with those reported previously, however, we observed a higher incidence of hemifacial microsomia and lower incidence of ocular anomalies. Furthermore our data suggests that OAVS patients with vertebral anomalies or congenital heart defects have a higher frequency of additional brain, limb or other malformations. We had a higher rate of familial cases in our cohort in comparison with previous reports, possibly because these cases were referred preferentially to our genetic clinic where family members underwent examination. We propose that familial OAVS cases show phenotypic variability, hence, affected relatives might have been misclassified in previous reports. Moreover, in view of its phenotypic variability, OAVS is potentially a spectrum of conditions, which overlap with other conditions, such as mandibulofacial dysostosis. Array CGH in our cohort identified recurrent dosage anomalies on 22q11, which may contribute to, or increase the risk of OAVS. We hypothesize that although the 22q11 locus may harbour gene(s) or regulatory elements that play a role in the regulation of craniofacial symmetry and 1st and 2nd branchial arch development, OAVS is a heterogeneous condition and many cases have a multifactorial aetiology or are caused by mutations in as yet unidentified gene(s).
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http://dx.doi.org/10.1016/j.ejmg.2015.07.003DOI Listing
September 2015

MiR-204 is responsible for inherited retinal dystrophy associated with ocular coloboma.

Proc Natl Acad Sci U S A 2015 Jun 8;112(25):E3236-45. Epub 2015 Jun 8.

Manchester Centre for Genomic Medicine, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester, Manchester M13 9WL, United Kingdom; Manchester Centre for Genomic Medicine, St. Mary's Hospital, Central Manchester University Hospitals National Health Service Foundation Trust, Manchester Academic Health Sciences Centre, Manchester M13 9WL, United Kingdom; European Retinal Dystrophy Consortium; United Kingdom Inherited Retinal Disease Consortium, Manchester Centre for Genomic Medicine, St. Mary's Hospital, Central Manchester University Hospitals National Health Service Foundation Trust, Manchester Academic Health Sciences Centre, Manchester M13 9WL, United Kingdom

Ocular developmental disorders, including the group classified as microphthalmia, anophthalmia, and coloboma (MAC) and inherited retinal dystrophies, collectively represent leading causes of hereditary blindness. Characterized by extreme genetic and clinical heterogeneity, the separate groups share many common genetic causes, in particular relating to pathways controlling retinal and retinal pigment epithelial maintenance. To understand these shared pathways and delineate the overlap between these groups, we investigated the genetic cause of an autosomal dominantly inherited condition of retinal dystrophy and bilateral coloboma, present in varying degrees in a large, five-generation family. By linkage analysis and exome sequencing, we identified a previously undescribed heterozygous mutation, n.37 C > T, in the seed region of microRNA-204 (miR-204), which segregates with the disease in all affected individuals. We demonstrated that this mutation determines significant alterations of miR-204 targeting capabilities via in vitro assays, including transcriptome analysis. In vivo injection, in medaka fish (Oryzias latipes), of the mutated miR-204 caused a phenotype consistent with that observed in the family, including photoreceptor alterations with reduced numbers of both cones and rods as a result of increased apoptosis, thereby confirming the pathogenic effect of the n.37 C > T mutation. Finally, knockdown assays in medaka fish demonstrated that miR-204 is necessary for normal photoreceptor function. Overall, these data highlight the importance of miR-204 in the regulation of ocular development and maintenance and provide the first evidence, to our knowledge, of its contribution to eye disease, likely through a gain-of-function mechanism.
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http://dx.doi.org/10.1073/pnas.1401464112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4485104PMC
June 2015

Agnathia-otocephaly complex and asymmetric velopharyngeal insufficiency due to an in-frame duplication in OTX2.

J Hum Genet 2015 Apr 15;60(4):199-202. Epub 2015 Jan 15.

1] Institute of Human Development, University of Manchester, Manchester, UK [2] Manchester Centre for Genomic Medicine, St Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK.

Agnathia-otocephaly complex is a malformation characterized by absent/hypoplastic mandible and abnormally positioned ears. Mutations in two genes, PRRX1 and OTX2, have been described in a small number of families with this disorder. We performed clinical and genetic testing in an additional family. The proband is a healthy female with a complicated pregnancy history that includes two offspring diagnosed with agnathia-otocephaly during prenatal ultrasound scans. Exome sequencing was performed in fetal DNA from one of these two offspring revealing a heterozygous duplication in OTX2: c.271_273dupCAG, p.(Gln91dup). This change leads to the insertion of a glutamine within the OTX2 homeodomain region, and is predicted to alter this signaling molecule's ability to interact with DNA. The same variant was also identified in the proband's clinically unaffected 38-year-old husband and their 9-year-old daughter, who presented with a small mandible, normal ears and velopharyngeal insufficiency due to a short hemi-palate. This unusual presentation of OTX2-related disease suggests that OTX2 might have a role in palatal hypoplasia cases. A previously unreported OTX2 variant associated with extreme intrafamilial variability is described and the utility of exome sequencing as a tool to confirm the diagnosis of agnathia-otocephaly and to inform the reproductive decisions of affected families is highlighted.
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http://dx.doi.org/10.1038/jhg.2014.122DOI Listing
April 2015

Abrogation of HMX1 function causes rare oculoauricular syndrome associated with congenital cataract, anterior segment dysgenesis, and retinal dystrophy.

Invest Ophthalmol Vis Sci 2015 Jan 8;56(2):883-91. Epub 2015 Jan 8.

Manchester Centre for Genomic Medicine, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Science Centre (MAHSC), Saint Mary's Hospital, Manchester, United Kingdom Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, MAHSC, Saint Mary's Hospital, Manchester, United Kingdom.

Purpose: To define the phenotypic manifestation, confirm the genetic basis, and delineate the pathogenic mechanisms underlying an oculoauricular syndrome (OAS).

Methods: Two individuals from a consanguineous family underwent comprehensive clinical phenotyping and electrodiagnostic testing (EDT). Genome-wide microarray analysis and Sanger sequencing of the candidate gene were used to identify the likely causal variant. Protein modelling, Western blotting, and dual luciferase assays were used to assess the pathogenic effect of the variant in vitro.

Results: Complex developmental ocular abnormalities of congenital cataract, anterior segment dysgenesis, iris coloboma, early-onset retinal dystrophy, and abnormal external ear cartilage presented in the affected family members. Genetic analyses identified a homozygous c.650A>C; p.(Gln217Pro) missense mutation within the highly conserved homeodomain of the H6 family homeobox 1 (HMX1) gene. Protein modelling predicts that the variant may have a detrimental effect on protein folding and/or stability. In vitro analyses were able to demonstrate that the mutation has no effect on protein expression but adversely alters function.

Conclusions: Oculoauricular syndrome is an autosomal recessive condition that has a profound effect on the development of the external ear, anterior segment, and retina, leading to significant visual loss at an early age. This study has delineated the phenotype and confirmed HMX1 as the gene causative of OAS, enabling the description of only the second family with the condition. HMX1 is a key player in ocular development, possibly in both the pathway responsible for lens and retina development, and via the gene network integral to optic fissure closure.
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http://dx.doi.org/10.1167/iovs.14-15861DOI Listing
January 2015

Mutations in LZTR1 add to the complex heterogeneity of schwannomatosis.

Neurology 2015 Jan 5;84(2):141-7. Epub 2014 Dec 5.

From the Manchester Centre for Genomic Medicine (M.J.S., W.G.N., D.G.E.) and University of Manchester Biomedical Imaging Institute (S.J.M.), Manchester Academic Health Sciences Centre, and Centre for Imaging Sciences (S.J.M.), University of Manchester, UK; Service de Dermatologie (S.B.) and Service de Genetique Medicale (B.I.), CHU Nantes, France; Institut für Klinische Chemie und Laboratoriumsdiagnostik Universitätsklinikum Jena (C.B.), Germany; Centre for Genomic Medicine (S.G.W., S.S.B., J.O., B.A., S.B.D., J.E.U., W.G.N., D.G.E.), St. Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, UK; INSERM U830 (W.R., F.B.), Laboratoire de Genetique et Biologie des Cancers, Paris, France; Department of Clinical Genetics (A.F.), Alder Hey Children's Hospital, Liverpool, UK; Department of Medical Genetics (C.F.R.), Oslo University Hospital, Norway; International Neuroscience Institute (A.S.), Hannover, Germany; Department of Cellular Pathology and Greater Manchester Neurosciences Centre (D.d.P.), Salford Royal Hospitals NHS Foundation Trust; Department of Clinical Genetics (D.H.), Oxford Radcliffe Hospitals NHS Trust, UK; and Institut Curie (F.B.), SIRIC and Departement d'Oncologie Pediatrique d'Adolescents et Jeunes Adultes, Paris, France.

Objectives: We aimed to determine the proportion of individuals in our schwannomatosis cohort whose disease is associated with an LZTR1 mutation.

Methods: We used exome sequencing, Sanger sequencing, and copy number analysis to screen 65 unrelated individuals with schwannomatosis who were negative for a germline NF2 or SMARCB1 mutation. We also screened samples from 39 patients with a unilateral vestibular schwannoma (UVS), plus at least one other schwannoma, but who did not have an identifiable germline or mosaic NF2 mutation.

Results: We identified germline LZTR1 mutations in 6 of 16 patients (37.5%) with schwannomatosis who had at least one affected relative, 11 of 49 (22%) sporadic patients, and 2 of 39 patients with UVS in our cohort. Three germline mutation-positive patients in total had developed a UVS. Mosaicism was excluded in 3 patients without germline mutation in NF2, SMARCB1, or LZTR1 by mutation screening in 2 tumors from each.

Conclusions: Our data confirm the relationship between mutations in LZTR1 and schwannomatosis. They indicate that germline mutations in LZTR1 confer an increased risk of vestibular schwannoma, providing further overlap with NF2, and that further causative genes for schwannomatosis remain to be identified.
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http://dx.doi.org/10.1212/WNL.0000000000001129DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4336087PMC
January 2015

Mutations in CKAP2L, the human homolog of the mouse Radmis gene, cause Filippi syndrome.

Am J Hum Genet 2014 Nov 6;95(5):622-32. Epub 2014 Nov 6.

Cologne Center for Genomics, University of Cologne, 50931 Cologne, Germany; Center for Molecular Medicine Cologne, University of Cologne, 50931 Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, 50931 Cologne, Germany. Electronic address:

Filippi syndrome is a rare, presumably autosomal-recessive disorder characterized by microcephaly, pre- and postnatal growth failure, syndactyly, and distinctive facial features, including a broad nasal bridge and underdeveloped alae nasi. Some affected individuals have intellectual disability, seizures, undescended testicles in males, and teeth and hair abnormalities. We performed homozygosity mapping and whole-exome sequencing in a Sardinian family with two affected children and identified a homozygous frameshift mutation, c.571dupA (p.Ile191Asnfs(∗)6), in CKAP2L, encoding the protein cytoskeleton-associated protein 2-like (CKAP2L). The function of this protein was unknown until it was rediscovered in mice as Radmis (radial fiber and mitotic spindle) and shown to play a pivotal role in cell division of neural progenitors. Sanger sequencing of CKAP2L in a further eight unrelated individuals with clinical features consistent with Filippi syndrome revealed biallelic mutations in four subjects. In contrast to wild-type lymphoblastoid cell lines (LCLs), dividing LCLs established from the individuals homozygous for the c.571dupA mutation did not show CKAP2L at the spindle poles. Furthermore, in cells from the affected individuals, we observed an increase in the number of disorganized spindle microtubules owing to multipolar configurations and defects in chromosome segregation. The observed cellular phenotypes are in keeping with data from in vitro and in vivo knockdown studies performed in human cells and mice, respectively. Our findings show that loss-of-function mutations in CKAP2L are a major cause of Filippi syndrome.
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http://dx.doi.org/10.1016/j.ajhg.2014.10.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4225581PMC
November 2014