Fetal akinesia (FA) results in variable clinical presentations and has been associated with more than 166 different disease loci. However, the underlying molecular cause remains unclear in many ...individuals. We aimed to further define the set of genes involved.
We performed in-depth clinical characterisation and exome sequencing on a cohort of 23 FA index cases sharing arthrogryposis as a common feature.
We identified likely pathogenic or pathogenic variants in 12 different established disease genes explaining the disease phenotype in 13 index cases and report 12 novel variants. In the unsolved families, a search for recessive-type variants affecting the same gene was performed; and in five affected fetuses of two unrelated families, a homozygous loss-of-function variant in the
gene (
) was found.
Our study underlines the broad locus heterogeneity of FA with well-established and atypical genotype-phenotype associations. We describe
as a new factor implicated in the pathogenesis of severe neurogenic FA sequence with arthrogryposis of multiple joints, pulmonary hypoplasia and facial dysmorphisms. This hypothesis is further corroborated by a recent report on overlapping phenotypes observed in Kif21a null piglets.
Pathogenic variants in A Disintegrin And Metalloproteinase (ADAM) 22, the postsynaptic cell membrane receptor for the glycoprotein leucine-rich repeat glioma-inactivated protein 1 (LGI1), have been ...recently associated with recessive developmental and epileptic encephalopathy. However, so far, only two affected individuals have been described and many features of this disorder are unknown. We refine the phenotype and report 19 additional individuals harbouring compound heterozygous or homozygous inactivating ADAM22 variants, of whom 18 had clinical data available. Additionally, we provide follow-up data from two previously reported cases. All affected individuals exhibited infantile-onset, treatment-resistant epilepsy. Additional clinical features included moderate to profound global developmental delay/intellectual disability (20/20), hypotonia (12/20) and delayed motor development (19/20). Brain MRI findings included cerebral atrophy (13/20), supported by post-mortem histological examination in patient-derived brain tissue, cerebellar vermis atrophy (5/20), and callosal hypoplasia (4/20). Functional studies in transfected cell lines confirmed the deleteriousness of all identified variants and indicated at least three distinct pathological mechanisms: (i) defective cell membrane expression; (ii) impaired LGI1-binding; and/or (iii) impaired interaction with the postsynaptic density protein PSD-95. We reveal novel clinical and molecular hallmarks of ADAM22 deficiency and provide knowledge that might inform clinical management and early diagnostics.
Postsynaptic density protein-95 (PSD-95), encoded by DLG4, regulates excitatory synaptic function in the brain. Here we present the clinical and genetic features of 53 patients (42 previously ...unpublished) with DLG4 variants.
The clinical and genetic information were collected through GeneMatcher collaboration. All the individuals were investigated by local clinicians and the gene variants were identified by clinical exome/genome sequencing.
The clinical picture was predominated by early onset global developmental delay, intellectual disability, autism spectrum disorder, and attention deficit-hyperactivity disorder, all of which point to a brain disorder. Marfanoid habitus, which was previously suggested to be a characteristic feature of DLG4-related phenotypes, was found in only nine individuals and despite some overlapping features, a distinct facial dysmorphism could not be established. Of the 45 different DLG4 variants, 39 were predicted to lead to loss of protein function and the majority occurred de novo (four with unknown origin). The six missense variants identified were suggested to lead to structural or functional changes by protein modeling studies.
The present study shows that clinical manifestations associated with DLG4 overlap with those found in other neurodevelopmental disorders of synaptic dysfunction; thus, we designate this group of disorders as DLG4-related synaptopathy.
Very tall people attract much attention and represent a clinically and genetically heterogenous group of individuals. Identifying the genetic etiology can provide important insights into the ...molecular mechanisms regulating linear growth. We studied a three-generation pedigree with five isolated (non-syndromic) tall members and one individual with normal stature by whole exome sequencing; the tallest man had a height of 211 cm. Six heterozygous gene variants predicted as damaging were shared among the four genetically related tall individuals and not present in a family member with normal height. To gain insight into the putative role of these candidate genes in bone growth, we assessed the transcriptome of murine growth plate by microarray and RNA Seq. Two (
) of the six genes were well-expressed in the growth plate.
(
-value 1.91E-62) as well as
(
-value of 2.98E-06) showed significant downregulation of gene expression between the proliferative and hypertrophic zone, suggesting that these genes may be involved in the regulation of chondrocyte proliferation and/or hypertrophic differentiation.
and
have also significantly associated with height in GWAS studies. Pathway and network analysis indicated functional connections between
,
and
and previously associated (tall) stature genes. Knockout of the all-trans retinoic acid responsive gene, neuron navigator 2
, in
supports its functional role as a growth promotor. Collectively, our data expand the spectrum of genes with a putative role in tall stature phenotypes and, among other genes, highlight
as an interesting gene to this phenotype.
Bone morphogenetic protein 2 (BMP2) in chromosomal region 20p12 belongs to a gene superfamily encoding TGF-β-signaling proteins involved in bone and cartilage biology. Monoallelic deletions of 20p12 ...are variably associated with cleft palate, short stature, and developmental delay. Here, we report a cranioskeletal phenotype due to monoallelic truncating and frameshift BMP2 variants and deletions in 12 individuals from eight unrelated families that share features of short stature, a recognizable craniofacial gestalt, skeletal anomalies, and congenital heart disease. De novo occurrence and autosomal-dominant inheritance of variants, including paternal mosaicism in two affected sisters who inherited a BMP2 splice-altering variant, were observed across all reported families. Additionally, we observed similarity to the human phenotype of short stature and skeletal anomalies in a heterozygous Bmp2-knockout mouse model, suggesting that haploinsufficiency of BMP2 could be the primary phenotypic determinant in individuals with predicted truncating variants and deletions encompassing BMP2. These findings demonstrate the important role of BMP2 in human craniofacial, skeletal, and cardiac development and confirm that individuals heterozygous for BMP2 truncating sequence variants or deletions display a consistent distinct phenotype characterized by short stature and skeletal and cardiac anomalies without neurological deficits.
With the implementation of high-throughput sequencing protocols, the exhaustive scanning of known and candidate disease genes has become a feasible approach to genetic testing of patients with ...cardiomyopathy. A primary objective of the present study was to assess the performance characteristics of a 46-gene next-generation sequencing (NGS) assay that targets well-established cardiomyopathy genes. A total of 25 samples were analyzed. Twelve of those had previously been sequenced using resequencing arrays and served as reference samples for the assessment of the assay's performance characteristics. The remaining 13 samples were derived from consecutive patients. Both the analytical sensitivity and the specificity of the assay were 100% and the percentage of low-coverage bases was 0.4%, at an average read depth of 210×. In order to assess the diagnostic yield of the test, 13 consecutive samples representing cases of Dilated (n = 7), Hypertrophic (n = 4) and Left Ventricular Non-Compaction Cardiomyopathy (n = 2), were subjected to the 46-gene NGS assay. Including predicted pathogenic variants in the gene TTN, a total of 22 variants (11 novel) were detected in 10 patients, with a clear preponderance of variants of unknown pathogenicity (class 3 variants, 21/22, 95%). Of the seven DCM cases, two were digenic, involving variants in the genes MYH7 and RBM20 in one case and in DSP and TTN in the other case. Three other patients carried single TTN variants predicted to be pathogenic. Of the four HCM patients, one was trigenic (LAMA4, PKP2 and TTN) and three were digenic (DSP and TTN, MYH7 and NEXN, NEXN and TTN, respectively). As to LVNC, one of the two patients had one variant in the gene ABCC9 and two predicted pathogenic variants in the gene TTN. Strikingly, out of the thirteen investigated cases, only a single case exhibited a likely pathogenic or pathogenic variant justifying a positive test report. The percentage of inconclusive cases thus amounted to 69%. Three cases were devoid of any relevant variant. Two of these “negative” cases were subsequently taken to initially evaluate the use of an alternative NGS assay addressing 4813 genes previously implicated in genetic diseases (the so-called clinical exome). Although showing similar sensitivity and specificity values, the coverage of the 46 established cardiomyopathy genes was less efficient (low-coverage bases: 5%). In a case of DCM, the assay revealed a disruptive variant in the gene encoding the adrenoreceptor beta 2 (ADRB2), a protein implicated in signal transduction and energy metabolism in the heart. In conclusion, the 46 gene assay is applicable to routine genetic diagnostics of cardiomyopathy. The test detects many variants of unknown pathogenicity which need to be followed-up in order to gain benefit for the patients and their families. Samples devoid of any relevant variant may be subjected to a clinical exome assay, in order to identify interesting novel candidate genes.
•The data presented confirm previous findings pointing to a high rate of inconclusive cases associated with multigene testing.•Clinical exome sequencing provided a pointer to the gene ADRB2 being a new candidate gene in dilated cardiomyopathy.
Aims
Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) can both be due to mutations in the genes encoding β-myosin heavy chain (MYH7) or cardiac myosin-binding protein C (MYBPC3). ...The aim of the present study was to determine the prevalence and spectrum of mutations in both genes in German HCM and DCM patients and to establish novel genotype-to-phenotype correlations.
Methods and results
Coding exons and intron flanks of the two genes MYH7 and MYBPC3 of 236 patients with HCM and 652 patients with DCM were sequenced by conventional and array-based means. Clinical records were established following standard protocols. Mutations were detected in 41 and 11% of the patients with HCM and DCM, respectively. Differences were observed in the frequency of splice site and frame-shift mutations in the gene MYBPC3, which occurred more frequently (P< 0.02, P< 0.001, respectively) in HCM than in DCM, suggesting that cardiac myosin-binding protein C haploinsufficiency predisposes to hypertrophy rather than to dilation. Additional novel genotype-to-phenotype correlations were found in HCM, among these a link between MYBPC3 mutations and a particularly large thickness of the interventricular septum (P= 0.04 vs. carriers of a mutation in MYH7). Interestingly, this correlation and a link between MYH7 mutations and a higher degree of mitral valve regurgitation held true for both HCM and DCM, indicating that the gene affected by a mutation may determine the magnitude of structural and functional alterations in both HCM and DCM.
Conclusion
A large clinical-genetic study has unravelled novel genotype-to-phenotype correlations in HCM and DCM which warrant future investigation of both the underlying mechanisms and the prognostic use.
De novo pathogenic variants in the GATAD2B gene have been associated with a syndromic neurodevelopmental disorder (GAND) characterized by severe intellectual disability (ID), impaired speech, ...childhood hypotonia, and dysmorphic features. Since its first description in 2013, nine patients have been reported in case reports and a series of 50 patients was recently published, which is consistent with the relative frequency of GATAD2B pathogenic variants in public databases. We report the detailed phenotype of 19 patients from various ethnic backgrounds with confirmed pathogenic GATAD2B variants including intragenic deletions. All individuals presented developmental delay with a median age of 2.5 years for independent walking and of 3 years for first spoken words. GATAD2B variant carriers showed very little subsequent speech progress, two patients over 30 years of age remaining non-verbal. ID was mostly moderate to severe, with one profound and one mild case, which shows a wider spectrum of disease severity than previously reported. We confirm macrocephaly as a major feature in GAND (53%). Most common dysmorphic features included broad forehead, deeply set eyes, hypertelorism, wide nasal base, and pointed chin. Conversely, prenatal abnormalities, non-cerebral malformations, epilepsy, and autistic behavior were uncommon. Other features included feeding difficulties, behavioral abnormalities, and unspecific abnormalities on brain MRI. Improving our knowledge of the clinical phenotype is essential for correct interpretation of the molecular results and accurate patient management.
Noncompaction of the ventricular myocardium (NVM) is the morphological hallmark of a rare familial or sporadic unclassified heart disease of heterogeneous origin. NVM results presumably from a ...congenital developmental error and has been traced back to single point mutations in various genes. The objective of this study was to determine the underlying genetic defect in a large German family suffering from NVM. Twenty four family members were clinically assessed using advanced imaging techniques. For molecular characterization, a genome-wide linkage analysis was undertaken and the disease locus was mapped to chromosome 14ptel-14q12. Subsequently, two genes of the disease interval, MYH6 and MYH7 (encoding the alpha- and beta-myosin heavy chain, respectively) were sequenced, leading to the identification of a previously unknown de novo missense mutation, c.842G>C, in the gene MYH7. The mutation affects a highly conserved amino acid in the myosin subfragment-1 (R281T). In silico simulations suggest that the mutation R281T prevents the formation of a salt bridge between residues R281 and D325, thereby destabilizing the myosin head. The mutation was exclusively present in morphologically affected family members. A few members of the family displayed NVM in combination with other heart defects, such as dislocation of the tricuspid valve (Ebstein's anomaly, EA) and atrial septal defect (ASD). A high degree of clinical variability was observed, ranging from the absence of symptoms in childhood to cardiac death in the third decade of life. The data presented in this report provide first evidence that a mutation in a sarcomeric protein can cause noncompaction of the ventricular myocardium.
PDF
