Further Delineation of Phenotype and Genotype of Primary Microcephaly Syndrome with Cortical Malformations Associated with Mutations in the WDR62 Gene.
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ABSTRACT:
SUBMITTER: Slezak R
PROVIDER: S-EPMC8072659 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Genes associated with human microcephaly, a condition characterized by a small brain, include critical regulators of proliferation, cell fate and DNA repair. We describe a syndrome of congenital microcephaly and diverse defects in cerebral cortical architecture. Genome-wide linkage analysis in two families identified a 7.5-Mb locus on chromosome 19q13.12 containing 148 genes. Targeted high throughput sequence analysis of linked genes in each family yielded > 4,000 DNA variants and implicated a single gene, WDR62, as harboring potentially deleterious changes. We subsequently identified additional WDR62 mutations in four other families. Magnetic resonance imaging and postmortem brain analysis supports important roles for WDR62 in the proliferation and migration of neuronal precursors. WDR62 is a WD40 repeat-containing protein expressed in neuronal precursors as well as in postmitotic neurons in the developing brain and localizes to the spindle poles of dividing cells. The diverse phenotypes of WDR62 suggest it has central roles in many aspects of cerebral cortical development.
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Project description:SATB2 is an evolutionarily highly conserved chromatin remodeling gene located on chromosome 2q33.1. Vertebrate animal models have shown that Satb2 has a crucial role in craniofacial patterning and osteoblast differentiation, as well as in determining the fates of neuronal projections in the developing neocortex. In humans, chromosomal translocations and deletions of 2q33.1 leading to SATB2 haploinsufficiency are associated with cleft palate (CP), facial dysmorphism and intellectual disability (ID). A single patient carrying a nonsense mutation in SATB2 has been described to date. In this study, we performed trio-exome sequencing in a 3-year-old girl with CP and severely delayed speech development, and her unaffected parents. Previously, the girl had undergone conventional and molecular karyotyping (microarray analysis), as well as targeted analysis for different diseases associated with developmental delay, including Angelman syndrome, Rett syndrome and Fragile X syndrome. No diagnosis could be established. Exome sequencing revealed a de novo nonsense mutation in the SATB2 gene (c.715C>T; p.R239*). The identification of a second patient carrying a de novo nonsense mutation in SATB2 confirms that this gene is essential for normal craniofacial patterning and cognitive development. Based on our data and the literature published so far, we propose a new clinically recognizable syndrome - the SATB2-associated syndrome (SAS). SAS is likely to be underdiagnosed and should be considered in children with ID, severe speech delay, cleft or high-arched palate and abnormal dentition with crowded and irregularly shaped teeth.
| S-EPMC4350596 | biostudies-literature
Project description:The genetic causes of malformations of cortical development (MCD) remain largely unknown. Here we report the discovery of multiple pathogenic missense mutations in TUBG1, DYNC1H1 and KIF2A, as well as a single germline mosaic mutation in KIF5C, in subjects with MCD. We found a frequent recurrence of mutations in DYNC1H1, implying that this gene is a major locus for unexplained MCD. We further show that the mutations in KIF5C, KIF2A and DYNC1H1 affect ATP hydrolysis, productive protein folding and microtubule binding, respectively. In addition, we show that suppression of mouse Tubg1 expression in vivo interferes with proper neuronal migration, whereas expression of altered ?-tubulin proteins in Saccharomyces cerevisiae disrupts normal microtubule behavior. Our data reinforce the importance of centrosomal and microtubule-related proteins in cortical development and strongly suggest that microtubule-dependent mitotic and postmitotic processes are major contributors to the pathogenesis of MCD.
| S-EPMC3826256 | biostudies-literature
Project description:Hypomyelination with atrophy of the basal ganglia and cerebellum is a rare leukoencephalopathy that was identified using magnetic resonance imaging in 2002. In 2013, whole exome sequencing of 11 patients with the disease revealed that they all had the same de novo mutation in TUBB4A, which encodes tubulin β-4A. We investigated the mutation spectrum in a cohort of 42 patients and the relationship between genotype and phenotype. Patients were selected on the basis of clinical and magnetic resonance imaging abnormalities that are indicative of hypomyelination with atrophy of the basal ganglia and cerebellum. Genetic testing and a clinical inventory were performed, and sequential magnetic resonance images were evaluated using a standard protocol. The heterozygous TUBB4A mutation observed in the first 11 patients was the most common (25 patients). Additionally, 13 other heterozygous mutations were identified, located in different structural domains of tubulin β-4A. We confirmed that the mutations were de novo in all but three patients. In two of these three cases we lacked parental DNA and in one the mutation was also found in the mother, most likely due to mosaicism. Patients showed a phenotypic continuum ranging from neonatal to childhood disease onset, normal to delayed early development and slow to more rapid neurological deterioration. Neurological symptomatology consisted of extrapyramidal movement abnormalities, spasticity, ataxia, cognitive deficit and sometimes epilepsy. Three patients died and the oldest living patient was 29 years of age. The patients' magnetic resonance images showed an absent or disappearing putamen, variable cerebellar atrophy and highly variable cerebral atrophy. Apart from hypomyelination, myelin loss was evident in several cases. Three severely affected patients had similar, somewhat atypical magnetic resonance image abnormalities. The study results were strongly suggestive of a genotype-phenotype correlation. The 25 patients with the common c.745G>A mutation generally had a less rapidly progressive disease course than the 17 cases with other TUBB4A mutations. Overall, this work demonstrates that the distinctive magnetic resonance imaging pattern for hypomyelination with atrophy of the basal ganglia and cerebellum defines a homogeneous clinical phenotype of variable severity. Patients almost invariably have prominent extrapyramidal movement abnormalities, which are rarely seen in patients with hypomyelination of different origin. A dominant TUBB4A mutation is also associated with dystonia type 4, in which magnetic resonance images of the brain seem normal. It is highly likely that there is a disease continuum associated with TUBB4A mutations, of which hypomyelination with atrophy of the basal ganglia and cerebellum and dystonia type 4 are the extremes. This would indicate that extrapyramidal movement abnormalities constitute the core feature of the disease spectrum related to dominant TUBB4A mutations and that all other features are variable.
| S-EPMC4345790 | biostudies-literature
Project description:BACKGROUND: Primary microcephaly is a disorder of the brain resulting in a reduced head circumference that can come along with intellectual disability but with hardly any other neurological abnormalities. CASE PRESENTATION: In this study we report on three Pakistani males from a consanguineous family with 2, 4 and 25 years, diagnosed with autosomal recessive primary microcephaly. By genotyping, Sanger sequencing and using bioinformatical approaches the disease causing mutation was identified and evaluated. CONCLUSION: By using a 250K SNP array, we were able to detect an 11Mb large autozygous region in the MCPH2 locus on chromosome 19q13.12. Sequencing of the associated gene, WDR62, revealed the frameshift causing single base pair duplication, c.2527dupG. This mutation is predicted to affect the structural features of WDR62 which in turn changes the conformation and function of the protein. Aspartic acid (D) at position 843 was found to be conserved among various ortholog species. The present findings will be helpful in genetic diagnosis of patients and future studies of WDR62.
| S-EPMC4258795 | biostudies-literature
Project description:Large Xq22.3 deletion in Czech family inherited from unaffaceted mother leading to manifestation of X-linked contiguous gene deletion syndrome known as Alport syndrome with intellectual disability (ATS-ID) or AMME complex (OMIM #300194)
2019-12-02 | E-MTAB-8324 | biostudies-arrayexpress
Project description:The development of the human cerebral cortex is an orchestrated process involving the generation of neural progenitors in the periventricular germinal zones, cell proliferation characterized by symmetric and asymmetric mitoses, followed by migration of post-mitotic neurons to their final destinations in six highly ordered, functionally specialized layers. An understanding of the molecular mechanisms guiding these intricate processes is in its infancy, substantially driven by the discovery of rare mutations that cause malformations of cortical development. Mapping of disease loci in putative Mendelian forms of malformations of cortical development has been hindered by marked locus heterogeneity, small kindred sizes and diagnostic classifications that may not reflect molecular pathogenesis. Here we demonstrate the use of whole-exome sequencing to overcome these obstacles by identifying recessive mutations in WD repeat domain 62 (WDR62) as the cause of a wide spectrum of severe cerebral cortical malformations including microcephaly, pachygyria with cortical thickening as well as hypoplasia of the corpus callosum. Some patients with mutations in WDR62 had evidence of additional abnormalities including lissencephaly, schizencephaly, polymicrogyria and, in one instance, cerebellar hypoplasia, all traits traditionally regarded as distinct entities. In mice and humans, WDR62 transcripts and protein are enriched in neural progenitors within the ventricular and subventricular zones. Expression of WDR62 in the neocortex is transient, spanning the period of embryonic neurogenesis. Unlike other known microcephaly genes, WDR62 does not apparently associate with centrosomes and is predominantly nuclear in localization. These findings unify previously disparate aspects of cerebral cortical development and highlight the use of whole-exome sequencing to identify disease loci in settings in which traditional methods have proved challenging.
| S-EPMC3129007 | biostudies-literature
Project description:ObjectivePrimary microcephaly (MCPH) is a rare autosomal recessive disorder characterized by impaired congenital reduction of brain size along with head circumference and intellectual disability. MCPH is a heterogeneous disorder and more than twenty four genes associated with this disease have been identified so far. The objective of this study was to find out the novel genes or mutations leading to the genetic defect in a Saudi family with primary microcephaly.MethodsWhole exome sequencing was carried out to find the novel mutation and the results was further validated using Sanger sequencing analysis. This study was done in the Center of excellence in Genomic Medicine and Research, King Abdulaziz University under KACST project during 2017 and 2018.ResultsWe report a novel compound heterozygous mutations c.797C>T in exon 7 and c.1102G>A in exon 9 of the WD repeat domain 62 (WDR62) (OMIM 604317) gene in two affected siblings in Saudi family with intellectual disability, speech impediments walking difficulty along with primary microcephaly. Two rare, missense variants were detected in heterozygous state in the WDR62 gene in these two affected individuals from the heterozygous parents.ConclusionsA compound heterozygous mutations c.797C>T in exon 7 and c.1102G> A in exon 9 of the WDR62 gene was identified. WDR62 gene is very important gene and mutation can lead to neuro developmental defects, brain malformations, reduced brain and head size. These results should be taken into consideration during prognostic discussions and mutation spectrum with affected patients and their families in the Saudi population.
| S-EPMC6572970 | biostudies-literature
Project description:Severe congenital neutropenia type 4 (SCN4) is an autosomal recessive condition, which was defined recently with identification of the causative mutations in G6PC3. To date there are only three reports in the literature describing patients with SCN4 with mutations in the G6PC3 gene. We report four individuals with SCN4 who belong to a single large consanguineous kindred. We provide an overview of the non-haematological features of the condition with a focus on the adult phenotype, which has not been previously described in detail. We show that the superficial venous changes seen in SCN4 patients can develop into varicose veins and venous ulcers in adulthood. We review the range of congenital anomalies associated with SCN4. We demonstrate that secundum atrial septal defect, patent ductus arteriosus and valvular defects are the most frequent cardiac anomalies in SCN4. Drawing parallels with type 1 glycogen storage disease, we propose that poor growth of prenatal onset, mild-to-moderate learning disability, primary pulmonary hypertension, delayed or incomplete puberty, hypothyroidism and dysmorphism likely represent features of this syndrome. We also suggest monitoring for lipid anomalies, and kidney and liver function in affected patients. Delineation of the SCN4 phenotype may help in appropriate treatment and management and provide further insights into the pathogenesis of this multisystem disease.
| S-EPMC3039503 | biostudies-literature
Project description:Primary microcephaly (MCPH) is a rare developmental defect characterized by impaired cognitive functions, retarded neurodevelopment and reduced brain size. It is genetically heterogeneous and more than 17 genes so far have been identified that are associated with this disease.To study the genetic defect in a consanguineous Saudi family with primary microcephaly.Cross-sectional clinical genetics study of a Saudi family.Medical genomics research center.Blood samples collected from six members of a family of healthy consanguineous parents were analyzed by whole exome sequencing to identify the underlying pathogenic mutations in two members of the family (23-year-old female and 7-year-old male) who presented with primary microcephaly, intellectual disability, delayed psychomotor development and walking difficulty, speech impedi-ments and seizures.Detection of mutation in the WD repeat domain 62 (WDR62) gene in a family segregating autosomal recessive primary microcephaly.The exome variant analysis identified a novel missense mutation (c.3878C > A) in WDR62 gene in exon 30 resulting in amino acid change from alanine to aspartate (p.Ala1293Asp). Further validation in the affected patients and healthy members of family and 100 unrelated healthy persons as controls confirmed it to be pathogenic.Functional impairment of the WDR62 gene can lead to severe neurodevelopmental de-fects, brain malformations and reduced head size. A missense mutation of exon 30 changed alanine to aspartate in the WDR62 protein leading to the typical MCPH phenotype.Mutation was identified in a single family.
| S-EPMC6150548 | biostudies-literature