Publications by authors named "Katja Kloth"

22 Publications

  • Page 1 of 1

Severe congenital contractural arachnodactyly caused by biallelic pathogenic variants in FBN2.

Eur J Med Genet 2021 Mar 9;64(3):104161. Epub 2021 Feb 9.

Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Fibrillin-2, encoded by FBN2, plays an important role in the early process of elastic fiber assembly. To date, heterozygous pathogenic variants in FBN2 have been shown to cause congenital contractural arachnodactyly (CCA; Beals-Hecht syndrome). Classical CCA is characterized by long and slender fingers and toes, ear deformities, joint contractures at birth, clubfeet, muscular hypoplasia and often tall stature. In individuals with a severe CCA form, different cardiovascular or gastrointestinal anomalies have been described. Here, we report on a 15-year-old girl with a severe form of CCA and novel biallelic variants in FBN2. The girl inherited the missense variant c.3563G > T/p.(Gly1188Val) from her unaffected father and the nonsense variant c.6831C > A/p.(Cys2277*) from her healthy mother. We could detect only a small amount of FBN2 transcripts harboring the nonsense variant in leukocyte-derived mRNA from the patient and mother suggesting nonsense-mediated mRNA decay. As the father did not show any clinical signs of CCA we hypothesize the missense variant c.3563G > T to be a hypomorphic allele. Taken together, our data suggests that severe CCA can be inherited in an autosomal-recessive manner by compound heterozygosity of a hypomorphic and a null allele of the FBN2 gene.
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http://dx.doi.org/10.1016/j.ejmg.2021.104161DOI Listing
March 2021

CDK19-related disorder results from both loss-of-function and gain-of-function de novo missense variants.

Genet Med 2021 Jan 25. Epub 2021 Jan 25.

Center for Medical Genetics, Keio University School of Medicine, Tokyo, Japan.

Purpose: To expand the recent description of a new neurodevelopmental syndrome related to alterations in CDK19.

Methods: Individuals were identified through international collaboration. Functional studies included autophosphorylation assays for CDK19 Gly28Arg and Tyr32His variants and in vivo zebrafish assays of the CDK19 and CDK19.

Results: We describe 11 unrelated individuals (age range: 9 months to 14 years) with de novo missense variants mapped to the kinase domain of CDK19, including two recurrent changes at residues Tyr32 and Gly28. In vitro autophosphorylation and substrate phosphorylation assays revealed that kinase activity of protein was lower for p.Gly28Arg and higher for p.Tyr32His substitutions compared with that of the wild-type protein. Injection of CDK19 messenger RNA (mRNA) with either the Tyr32His or the Gly28Arg variants using in vivo zebrafish model significantly increased fraction of embryos with morphological abnormalities. Overall, the phenotype of the now 14 individuals with CDK19-related disorder includes universal developmental delay and facial dysmorphism, hypotonia (79%), seizures (64%), ophthalmologic anomalies (64%), and autism/autistic traits (56%).

Conclusion: CDK19 de novo missense variants are responsible for a novel neurodevelopmental disorder. Both kinase assay and zebrafish experiments showed that the pathogenetic mechanism may be more diverse than previously thought.
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http://dx.doi.org/10.1038/s41436-020-01091-9DOI Listing
January 2021

Heterogeneous phenotypes in families with duplications of the paternal allele within the imprinting center 1 (H19/IGF2:TSS-DMR) in 11p15.5.

Clin Genet 2020 10 9;98(4):418-419. Epub 2020 Aug 9.

Institute of Human Genetics, University of Würzburg, Würzburg, Germany.

The clinical impact of duplications affecting the 11p15.5 region is difficult to predict, and depends on the parent-of-origin of the affected allele as well as on the type (deletion, duplication), the extent and genomic content of the variant. Three unrelated families with inheritance of duplications affecting the IC1 region in 11p15.5 through two generations but different phenotypes (Beckwith-Wiedemann and Silver-Russell syndromes, normal phenotype) are reported. The inconsistent phenotypic patterns of carriers of the same variant strongly indicate the impact of cis- and/or trans-acting modifiers on the clinical outcome of IC1 duplication carriers.
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http://dx.doi.org/10.1111/cge.13820DOI Listing
October 2020

Mucopolysaccharidosis type I due to maternal uniparental disomy of chromosome 4 with partial isodisomy of 4p16.3p15.2.

Mol Genet Metab Rep 2020 Dec 22;25:100660. Epub 2020 Oct 22.

International Center for Lysosomal Disorders (ICLD), Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Mucopolysaccharidosis type I (MPS I) is a rare lysosomal storage disease caused by biallelic mutations in , the gene coding for the lysosomal enzyme alpha iduronidase. Clinically MPS I is a chronic progressive multisystem disease typically presenting with coarse facial features, skeletal deformities, joint contractures, and multi-organ involvement. Hurler syndrome (MPS IH) represents the severe end of the spectrum of mucopolysaccharidosis type I and is characterized by central nervous system involvement leading to childhood dementia. Here we report on a severe affected MPS IH patient who is homozygous for a splice site mutation (c.158 + 1G > A) in the gene. Further analyses revealed maternal uniparental disomy of chromosome 4 with partial isodisomy of the telomeric end of chromosome 4 (4.p16.3p15.2), representing an extraordinary mode of inheritance with a much lower re-occurrence risk for MPS I in the family.
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http://dx.doi.org/10.1016/j.ymgmr.2020.100660DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7582098PMC
December 2020

Dystonia as initial presentation of compound heterozygous GBA2 mutations: Expanding the phenotypic spectrum of SPG46.

Eur J Med Genet 2020 Sep 24;63(9):103992. Epub 2020 Jun 24.

Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Electronic address:

GBA2 associated spastic paraplegia type 46 (SPG46) is an autosomal-recessive disorder associated with a clinical presentation of spastic gait, muscle weakness as well as an array of clinical symptoms including pseudobulbar palsy and progressive cognitive decline. Several neurological and non-neurological symptoms are associated with GBA2 mutations. An initial presentation with dystonia has not been reported so far. We report clinical, genetic and brain imaging findings in two siblings with hereditary spastic paraparesis. One sister presented with juvenile-onset leg spasticity and progressed to spastic tetraparesis, cervical and jaw opening dystonia, pseudobulbar symptoms and dementia. The other sister initially developed cervical dystonia in adulthood followed by gait spasticity and cognitive decline in the disease course. Molecular genetic testing revealed novel compound heterozygous variants in GBA2 in both sisters. The initial presentation with cervical dystonia and the differing clinical disease progression expand the clinical phenotype of GBA2 associated SPG46.
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http://dx.doi.org/10.1016/j.ejmg.2020.103992DOI Listing
September 2020

A second cohort of CHD3 patients expands the molecular mechanisms known to cause Snijders Blok-Campeau syndrome.

Eur J Hum Genet 2020 10 1;28(10):1422-1431. Epub 2020 Jun 1.

Children's Hospital of Philadelphia, Philadelphia, PA, USA.

There has been one previous report of a cohort of patients with variants in Chromodomain Helicase DNA-binding 3 (CHD3), now recognized as Snijders Blok-Campeau syndrome. However, with only three previously-reported patients with variants outside the ATPase/helicase domain, it was unclear if variants outside of this domain caused a clinically similar phenotype. We have analyzed 24 new patients with CHD3 variants, including nine outside the ATPase/helicase domain. All patients were detected with unbiased molecular genetic methods. There is not a significant difference in the clinical or facial features of patients with variants in or outside this domain. These additional patients further expand the clinical and molecular data associated with CHD3 variants. Importantly we conclude that there is not a significant difference in the phenotypic features of patients with various molecular disruptions, including whole gene deletions and duplications, and missense variants outside the ATPase/helicase domain. This data will aid both clinical geneticists and molecular geneticists in the diagnosis of this emerging syndrome.
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http://dx.doi.org/10.1038/s41431-020-0654-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7608102PMC
October 2020

Truncating mutations in SHANK3 associated with global developmental delay interfere with nuclear β-catenin signaling.

J Neurochem 2020 11 16;155(3):250-263. Epub 2020 Apr 16.

Institute for Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Mutations in SHANK3, coding for a large scaffold protein of excitatory synapses in the CNS, are associated with neurodevelopmental disorders including autism spectrum disorders and intellectual disability (ID). Several cases have been identified in which the mutation leads to truncation of the protein, eliminating C-terminal sequences required for post-synaptic targeting of the protein. We identify here a patient with a truncating mutation in SHANK3, affected by severe global developmental delay and intellectual disability. By analyzing the subcellular distribution of this truncated form of Shank3, we identified a nuclear localization signal (NLS) in the N-terminal part of the protein which is responsible for targeting Shank3 fragments to the nucleus. To determine the relevance of Shank3 for nuclear signaling, we analyze how it affects signaling by β-catenin, a component of the Wnt pathway. We show that full length as well as truncated variants of Shank3 interact with β-catenin via the PDZ domain of Shank3, and the armadillo repeats of β-catenin. As a result of this interaction, truncated forms of Shank3 and β-catenin strictly co-localize in small intra-nuclear bodies both in 293T cells and in rat hippocampal neurons. On a functional level, the sequestration of both proteins in these nuclear bodies is associated with a strongly repressed transcriptional activation by β-catenin owing to interaction with the truncated Shank3 fragment found in patients. Our data suggest that truncating mutations in SHANK3 may not only lead to a reduction in Shank3 protein available at postsynaptic sites but also negatively affect the Wnt signaling pathway.
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http://dx.doi.org/10.1111/jnc.15014DOI Listing
November 2020

Excessive Seizure Clusters in an Otherwise Well-Controlled Epilepsy as a Possible Hallmark of Untreated Vitamin B6-Responsive Epilepsy due to a Homozygous Missense Variant.

J Pediatr Genet 2019 Dec 20;8(4):222-225. Epub 2019 Apr 20.

Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Recently, mutations in the gene were described as a novel cause for vitamin B6-responsive epilepsy. We report the outcome in case of a male adolescent with a novel homozygous missense variant in who was never treated with pyridoxine until the age of 16 years. He presented with only mild cognitive impairment and an early-onset, well-controlled epilepsy. In our patient, excessive seizure clusters and anxiety states occurred intermittently, suggesting that the combination might be a hallmark in untreated patients. Thus, mutations in should be addressed even in adolescent patients with only mild learning disabilities and relatively good seizure control over the years.
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http://dx.doi.org/10.1055/s-0039-1685501DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6824897PMC
December 2019

Exome Sequencing in Children.

Dtsch Arztebl Int 2019 03;116(12):197-204

*Joint last authors; Institute of Human Genetics, University Medical Center Hamburg-Eppendorf; Department of Pediatrics, University Medical Center Hamburg-Eppendorf; Institute of Human Genetics, Klinikum Rechts der Isar, TUM, Munich; Institute of Medical Genetics and Applied Genomics, University Hospital Tübingen; Institute of Human Genetics, Helmholtz Center Munich; Undiagnosed Disease Program at the University Medical Center Hamburg-Eppendorf (UDP-UKE).

Background: In developed countries, global developmental disorders are encounter- ed in approximately 1% of all children. The causes are manifold, and no exogenous cause can be identified in about half of the affected children. The parallel investi- gation of the coding sequences of all genes of the affected individual (whole exome sequencing, WES) has developed into a successful diagnostic method for identify- ing the cause of the problem. It is not yet clear, however, when WES should best be used in routine clinical practice in order to exploit the potential of this method to the fullest.

Methods: In an interdisciplinary study, we carried out standardized clinical pheno- typing and a systematic genetic analysis (WES of the index patient and his or her parents, so-called trio WES) in 50 children with developmental disturbances of unclear etiology and with nonspecific neurological manifestations.

Results: In 21 children (42% of the collective), we were able to identify the cause of the disorder by demonstrating a mutation in a gene known to be associated with disease. Three of these children subsequently underwent specific treatment. In 22 other children (44%), we detected possibly etiological changes in candidate genes not currently known to be associated with human disease.

Conclusion: Our detection rate of at least 42% is high in comparison with the results obtained in other studies from Germany and other countries to date and implies that WES can be used to good effect as a differential diagnostic tool in pediatric neurol- ogy. WES should be carried out in both the index patient and his or her parents (trio- WES) and accompanied by close interdisciplinary collaboration of human geneti- cists and pediatricians, by comprehensive and targeted phenotyping (also after the diagnosis is established), and by the meticulous evaluation of all gene variants.
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http://dx.doi.org/10.3238/arztebl.2019.0197DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6514384PMC
March 2019

Author Correction: CHD3 helicase domain mutations cause a neurodevelopmental syndrome with macrocephaly and impaired speech and language.

Nat Commun 2019 May 2;10(1):2079. Epub 2019 May 2.

CHU Sainte-Justine Research Center, Montreal, QC H3T 1C5, Canada.

The HTML and PDF versions of this Article were updated after publication to remove images of one individual from Figure 1.
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http://dx.doi.org/10.1038/s41467-019-10161-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6497626PMC
May 2019

16p13.11 microdeletion uncovers loss-of-function of a MYH11 missense variant in a patient with megacystis-microcolon-intestinal-hypoperistalsis syndrome.

Clin Genet 2019 07 16;96(1):85-90. Epub 2019 May 16.

Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS), a rare condition that affects smooth muscle cells, is caused by biallelic null alleles in MYH11. We report on a girl with MMIHS in addition to growth hormone deficiency, central hypothyroidism and a tonically dilated pupil with accommodation deficit. Sanger sequencing and arrayCGH uncovered the novel heterozygous missense variant c.379C>T in MYH11 and a heterozygous 1.3 Mb deletion in 16q13.11 encompassing MYH11, respectively. Her mother carries the deletion, whereas her father is heterozygous for the c.379C>T p.(Pro127Ser) change. Proline 127 is crucial for the formation of the Adenosine triphosphate binding pocket of the MYH11 motor domain and molecular modeling indicated that p.Pro127Ser alters nucleotide binding properties. Thus, the unusual and complex clinical presentation of the patient results from compound heterozygosity for a 16p13.11 microdeletion including the entire MYH11 gene and a loss-of-function missense variant on the remaining MYH11 allele. In conclusion, we recommend genetic testing both for MYH11 sequence alterations and copy number imbalances in individuals with MMIHS and smooth muscle cell-associated abnormalities in additional organs, that is, multisystemic smooth muscle dysfunction.
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http://dx.doi.org/10.1111/cge.13557DOI Listing
July 2019

Biallelic variants in SMAD6 are associated with a complex cardiovascular phenotype.

Hum Genet 2019 Jun 8;138(6):625-634. Epub 2019 Apr 8.

Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany.

Rare heterozygous variants in SMAD6 have been identified as a significant genetic contributor to bicuspid aortic valve-associated thoracic aortic aneurysm on one hand and non-syndromic midline craniosynostosis on the other. In this study, we report two individuals with biallelic missense variants in SMAD6 and a complex cardiac phenotype. Trio exome sequencing in Proband 1, a male who had aortic isthmus stenosis, revealed the homozygous SMAD6 variant p.(Ile466Thr). He also had mild intellectual disability and radio-ulnar synostosis. Proband 2 is a female who presented with a more severe cardiac phenotype with a dysplastic and stenotic pulmonary valve and dilated cardiomyopathy. In addition, she had vascular anomalies, including a stenotic left main coronary artery requiring a bypass procedure, narrowing of the proximal left pulmonary artery and a venous anomaly in the brain. Proband 2 has compound heterozygous SMAD6 missense variants, p.(Phe357Ile) and p.(Ser483Pro). Absence of these SMAD6 variants in the general population and high pathogenicity prediction scores suggest that these variants caused the probands' phenotypes. This is further corroborated by cardiovascular anomalies and appendicular skeletal defects in Smad6-deficient mice. SMAD6 acts as an inhibitory SMAD and preferentially inhibits bone morphogenetic protein (BMP)-induced signaling. Our data suggest that biallelic variants in SMAD6 may affect the inhibitory activity of SMAD6 and cause enhanced BMP signaling underlying the cardiovascular anomalies and possibly other clinical features in the two probands.
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http://dx.doi.org/10.1007/s00439-019-02011-xDOI Listing
June 2019

Novel likely pathogenic variants in TMEM126A identified in non-syndromic autosomal recessive optic atrophy: two case reports.

BMC Med Genet 2019 04 8;20(1):62. Epub 2019 Apr 8.

Center for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany.

Background: Reports on autosomal recessive optic atrophy (arOA) are sparse and so far, only one gene has been specifically associated with non-syndromic arOA, namely TMEM126A. To date, all reports of pathogenic TMEM126A variants are from affected individuals of Maghrebian origin, who all carry an identical nonsense variant. Here we report two novel variants in the TMEM126A gene from non-Maghreb individuals, both found in affected individuals with an arOA phenotype.

Case Presentation: We report three affected individuals from two families. The proband of family A, a 24-year-old Turkish woman, was diagnosed with visual loss in early childhood but a diagnosis of optic atrophy was only made at 14 years. A diagnostic gene panel revealed a splice donor variant (c.86 + 2 T > C) in homozygous state in the TMEM126A gene. Analysis of this variant based on RNA from whole blood revealed a single aberrant transcript lacking exon 2, presumably representing a functional null allele. Two siblings from family B, a 16-year old Iraqi girl and her 14-year old brother, were diagnosed with optic atrophy in early childhood. A missense variant p.(S36 L) in the TMEM126A gene was identified in homozygous state in a gene panel-based diagnostic setting in both siblings. This missense variant is ultra rare in the general population, affects a highly evolutionarily conserved amino acid and segregates with the disease within the family. The three probands reported in this study had a relatively mild clinical course without any evidence of a syndromic (e.g. neurological) comorbidity, which is in line with previous studies.

Conclusions: We provide additional evidence for the implication of biallelic pathogenic TMEM126A variants in arOA. Our findings extend both the mutational spectrum and geographic presence of TMEM126A in arOA. Screening of the entire gene should be considered in affected individuals presenting with features resembling arOA and also from non-Maghrebian descent.
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http://dx.doi.org/10.1186/s12881-019-0795-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6454730PMC
April 2019

Author Correction: CHD3 helicase domain mutations cause a neurodevelopmental syndrome with macrocephaly and impaired speech and language.

Nat Commun 2019 02 15;10(1):883. Epub 2019 Feb 15.

CHU Sainte-Justine Research Center, Montreal, QC, H3T 1C5, Canada.

The original version of this Article contained an error in the spelling of the author Laurence Faivre, which was incorrectly given as Laurence Faive. This has now been corrected in both the PDF and HTML versions of the Article.
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http://dx.doi.org/10.1038/s41467-019-08800-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6377600PMC
February 2019

Next-generation sequencing of 32 genes associated with hereditary aortopathies and related disorders of connective tissue in a cohort of 199 patients.

Genet Med 2019 08 24;21(8):1832-1841. Epub 2019 Jan 24.

Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Purpose: Heritable factors play an important etiologic role in connective tissue disorders (CTD) with vascular involvement, and a genetic diagnosis is getting increasingly important for gene-tailored, personalized patient management.

Methods: We analyzed 32 disease-associated genes by using targeted next-generation sequencing and exome sequencing in a clinically relevant cohort of 199 individuals. We classified and refined sequence variants according to their likelihood for pathogenicity.

Results: We identified 1 pathogenic variant (PV; in FBN1 or SMAD3) in 15 patients (7.5%) and ≥1 likely pathogenic variant (LPV; in COL3A1, FBN1, FBN2, LOX, MYH11, SMAD3, TGFBR1, or TGFBR2) in 19 individuals (9.6%), together resulting in 17.1% diagnostic yield. Thirteen PV/LPV were novel. Of PV/LPV-negative patients 47 (23.6%) showed ≥1 variant of uncertain significance (VUS). Twenty-five patients had concomitant variants. In-depth evaluation of reported/calculated variant classes resulted in reclassification of 19.8% of variants.

Conclusion: Variant classification and refinement are essential for shaping mutational spectra of disease genes, thereby improving clinical sensitivity. Obligate stringent multigene analysis is a powerful tool for identifying genetic causes of clinically related CTDs. Nonetheless, the relatively high rate of PV/LPV/VUS-negative patients underscores the existence of yet unknown disease loci and/or oligogenic/polygenic inheritance.
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http://dx.doi.org/10.1038/s41436-019-0435-zDOI Listing
August 2019

Recurrent, Activating Variants in the Receptor Tyrosine Kinase DDR2 Cause Warburg-Cinotti Syndrome.

Am J Hum Genet 2018 12 15;103(6):976-983. Epub 2018 Nov 15.

Department of Ophthalmology, Haukeland University Hospital, N-5021 Bergen, Norway; Department of Medical Genetics, Haukeland University Hospital, N-5021 Bergen, Norway; Department of Clinical Medicine, University of Bergen, N-5021 Bergen, Norway.

We have investigated a distinct disorder with progressive corneal neovascularization, keloid formation, chronic skin ulcers, wasting of subcutaneous tissue, flexion contractures of the fingers, and acro-osteolysis. In six affected individuals from four families, we found one of two recurrent variants in discoidin domain receptor tyrosine kinase 2 (DDR2): c.1829T>C (p.Leu610Pro) or c.2219A>G (p.Tyr740Cys). DDR2 encodes a collagen-responsive receptor tyrosine kinase that regulates connective-tissue formation. In three of the families, affected individuals comprise singleton adult individuals, and parental samples were not available for verification of the de novo occurrence of the DDR2 variants. In the fourth family, a mother and two of her children were affected, and the c.2219A>G missense variant was proven to be de novo in the mother. Phosphorylation of DDR2 was increased in fibroblasts from affected individuals, suggesting reduced receptor autoinhibition and ligand-independent kinase activation. Evidence for activation of other growth-regulatory signaling pathways was not found. Finally, we found that the protein kinase inhibitor dasatinib prevented DDR2 autophosphorylation in fibroblasts, suggesting an approach to treatment. We propose this progressive, fibrotic condition should be designated as Warburg-Cinotti syndrome.
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http://dx.doi.org/10.1016/j.ajhg.2018.10.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6288050PMC
December 2018

CHD3 helicase domain mutations cause a neurodevelopmental syndrome with macrocephaly and impaired speech and language.

Nat Commun 2018 11 5;9(1):4619. Epub 2018 Nov 5.

CHU Sainte-Justine Research Center, Montreal, QC H3T 1C5, Canada.

Chromatin remodeling is of crucial importance during brain development. Pathogenic alterations of several chromatin remodeling ATPases have been implicated in neurodevelopmental disorders. We describe an index case with a de novo missense mutation in CHD3, identified during whole genome sequencing of a cohort of children with rare speech disorders. To gain a comprehensive view of features associated with disruption of this gene, we use a genotype-driven approach, collecting and characterizing 35 individuals with de novo CHD3 mutations and overlapping phenotypes. Most mutations cluster within the ATPase/helicase domain of the encoded protein. Modeling their impact on the three-dimensional structure demonstrates disturbance of critical binding and interaction motifs. Experimental assays with six of the identified mutations show that a subset directly affects ATPase activity, and all but one yield alterations in chromatin remodeling. We implicate de novo CHD3 mutations in a syndrome characterized by intellectual disability, macrocephaly, and impaired speech and language.
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http://dx.doi.org/10.1038/s41467-018-06014-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6218476PMC
November 2018

Activating Mutations in PAK1, Encoding p21-Activated Kinase 1, Cause a Neurodevelopmental Disorder.

Am J Hum Genet 2018 10;103(4):579-591

Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany. Electronic address:

p21-activated kinases (PAKs) are serine/threonine protein kinases acting as effectors of CDC42 and RAC, which are members of the RHO family of small GTPases. PAK1's kinase activity is autoinhibited by homodimerization, whereas CDC42 or RAC1 binding causes PAK1 activation by dimer dissociation. Major functions of the PAKs include actin cytoskeleton reorganization, for example regulation of the cellular protruding activity during cell spreading. We report the de novo PAK1 mutations c.392A>G (p.Tyr131Cys) and c.1286A>G (p.Tyr429Cys) in two unrelated subjects with developmental delay, secondary macrocephaly, seizures, and ataxic gait. We identified enhanced phosphorylation of the PAK1 targets JNK and AKT in fibroblasts of one subject and of c-JUN in those of both subjects compared with control subjects. In fibroblasts of the two affected individuals, we observed a trend toward enhanced PAK1 kinase activity. By using co-immunoprecipitation and size-exclusion chromatography, we observed a significantly reduced dimerization for both PAK1 mutants compared with wild-type PAK1. These data demonstrate that the two PAK1 variants function as activating alleles. In a cell spreading assay, subject-derived fibroblasts showed significant enrichment in cells occupied by filopodia. Interestingly, application of the PAK1 inhibitor FRAX486 completely reversed this cellular phenotype. Together, our data reveal that dominantly acting, gain-of-function PAK1 mutations cause a neurodevelopmental phenotype with increased head circumference, possibly by a combined effect of defective homodimerization and enhanced kinase activity of PAK1. This condition, along with the developmental disorders associated with RAC1 and CDC42 missense mutations, highlight the importance of RHO GTPase members and effectors in neuronal development.
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http://dx.doi.org/10.1016/j.ajhg.2018.09.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6174322PMC
October 2018

Dual antibody induction and de novo use of everolimus enable low-dose tacrolimus with early corticosteroid withdrawal in simultaneous pancreas-kidney transplantation.

Transpl Immunol 2018 10 6;50:26-33. Epub 2018 Jun 6.

Department of Hepatobiliary Surgery and Transplantation, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Background: To be an optimal immunosuppressive regimen after simultaneous pancreas kidney transplantation (SPK), low dose calcineurin inhibitor and early withdrawal of corticosteroids are desired.

Methods: Immunosuppressive regimen as such has been conducted consecutively in SPK recipients since 2009 in authors' institute. In addition to tacrolimus in low trough level and early corticosteroid withdraw, dual induction with basiliximab and low-dose thymoglobulin in combination with everolimus are the important components of the protocol.

Results: 25 consecutive primary SPK recipients were included in the study. Lymphocyte depletion by low dose thymoglobulin was limited to two weeks, and CD25 coating with basiliximab was detectable for 4 weeks. The BPAR within the first 12 months was 13%. During a median follow-up of 58 months, new-onset diabetes mellitus and renal function deterioration were rare events. No cytomegalovirus activation was encountered. The patients, pancreas and kidney graft survival at 1-year and 5-year was 100% and 94.4%, 95.8% and 95.8%, 100% and 100% respectively.
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http://dx.doi.org/10.1016/j.trim.2018.06.001DOI Listing
October 2018

Whole-genome sequencing in patients with ciliopathies uncovers a novel recurrent tandem duplication in IFT140.

Hum Mutat 2018 07 8;39(7):983-992. Epub 2018 May 8.

Laboratoire de Génétique médicale, UMR_S INSERM U1112, IGMA, Faculté de Médecine FMTS, Université de Strasbourg, Strasbourg, France.

Ciliopathies represent a wide spectrum of rare diseases with overlapping phenotypes and a high genetic heterogeneity. Among those, IFT140 is implicated in a variety of phenotypes ranging from isolated retinis pigmentosa to more syndromic cases. Using whole-genome sequencing in patients with uncharacterized ciliopathies, we identified a novel recurrent tandem duplication of exon 27-30 (6.7 kb) in IFT140, c.3454-488_4182+2588dup p.(Tyr1152_Thr1394dup), missed by whole-exome sequencing. Pathogenicity of the mutation was assessed on the patients' skin fibroblasts. Several hundreds of patients with a ciliopathy phenotype were screened and biallelic mutations were identified in 11 families representing 12 pathogenic variants of which seven are novel. Among those unrelated families especially with a Mainzer-Saldino syndrome, eight carried the same tandem duplication (two at the homozygous state and six at the heterozygous state). In conclusion, we demonstrated the implication of structural variations in IFT140-related diseases expanding its mutation spectrum. We also provide evidences for a unique genomic event mediated by an Alu-Alu recombination occurring on a shared haplotype. We confirm that whole-genome sequencing can be instrumental in the ability to detect structural variants for genomic disorders.
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http://dx.doi.org/10.1002/humu.23539DOI Listing
July 2018

First de novo ANK3 nonsense mutation in a boy with intellectual disability, speech impairment and autistic features.

Eur J Med Genet 2017 Sep 4;60(9):494-498. Epub 2017 Jul 4.

Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Electronic address:

Ankyrin-G, encoded by ANK3, plays an important role in neurodevelopment and neuronal function. There are multiple isoforms of Ankyrin-G resulting in differential tissue expression and function. Heterozygous missense mutations in ANK3 have been associated with autism spectrum disorder. Further, in three siblings a homozygous frameshift mutation affecting only the longest isoform and a patient with a balanced translocation disrupting all isoforms were documented. The latter four patients were affected by a variable degree of intellectual disability, attention deficit hyperactivity disorder and autism. Here, we report on a boy with speech impairment, intellectual disability, autistic features, macrocephaly, macrosomia, chronic hunger and an altered sleeping pattern. By trio-whole-exome sequencing, we identified the first de novo nonsense mutation affecting all ANK3 transcripts. Thus, our data expand the phenotype of ANK3-associated diseases and suggest an isoform-based, phenotypic continuum between dominant and recessive ANK3-associated pathologies.
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http://dx.doi.org/10.1016/j.ejmg.2017.07.001DOI Listing
September 2017

Options and limitations in applying the fistula classification by the International Study Group for Pancreatic Fistula.

Ann Surg 2012 Jul;256(1):130-8

Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, University of Hamburg, Germany.

Background: Because of its retrospective character, the classification system of the International Study Group of Pancreatic Fistula (ISGPF) lacks prognostic capacity regarding fistula-related complications. This study aimed to evaluate the options and limitations of the ISGPF classification system and to identify risk factors with respect to clinical decision making.

Methods: Between 1992 and 2009, 1966 patients underwent surgery of the pancreas. All patient data were entered into a prospective clinical data management system.

Results: After surgery, 276 patients (14%) developed postoperative pancreatic fistula (POPF). ISGPF type A fistula was seen in 69 patients (25%), type B in 110 (39.9%), and type C in 97 (34.1%). Solely due to their death, 16 patients had to be classified as type C fistula, even though they suffered only type A or B. Compared to genuine C fistulas, we were not able to detect any significant predictors, which may allow to distinguish the development in their further clinical course. The level of drainage amylase is of no use, whereas univariate analysis identified underlying disease, type of operation, and high levels of serum amylase or bilirubin on the day of onset of POPF to be prognostic parameters for reoperation. Multivariate analysis found elevated serum C-reactive protein to be an independent factor for increased in-hospital mortality.

Conclusions: The ISGPF classification system has its limitations in clinical decision making, because it does not adequately describe a large subgroup of patients. To improve clinical decision making about management of patients, it is crucial that the ISGPF classification system is merged with newer clinical data.
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http://dx.doi.org/10.1097/SLA.0b013e31824f24e4DOI Listing
July 2012