A Novel Missense Mutation in the TGF-ß-binding Protein-Like Domain 3 of FBN1 Causes Weill-Marchesani Syndrome with Intellectual Disability.

Background: Weill-Marchesani syndrome (WMS) is a rare connective tissue disorder characterized by locus heterogeneity and variable expressivity. Patients suffering from WMS are described by short stature, brachydactyly, joint stiffness, congenital heart defects, and eye abnormalities. This disorder is inherited in two different modes; the autosomal dominant form of the disease occurs due to a mutation in FBN1, and the recessive form results from mutations in ADAMTS10, ADAMTS17, or LTP2 genes. Materials and Methods: The family recruited in this study was a consanguineous Iranian family with an intellectually disabled girl referred to the Sadra Genetics laboratory, Shahrekord, Iran. The clinical history of family members was investigated. Whole-Exome Sequencing (WES) for the proband was performed. Sanger sequencing was used to assess the segregation of candidate variants in the other family members. Results: Whole-exome sequencing analysis revealed a novel heterozygote mutation in the proband located at the third TGF-ß-binding protein-like (TB) domain of the FBN1 gene (NM000138: c.2066A>G: (p. Glu689Gly), NP_000129.3, in exon 17 of the gene). Co-segregation analysis with Sanger sequencing confirmed this mutation in the affected members of the pedigree. Conclusion: Our findings represent an autosomal dominant form of specific WMS resulting from a substitution mutation in the FBN1 gene. In addition to the typical manifestations of the disorder, mild intellectual disability (ID) was identified in the 8-year-old proband. Given the fact that ID is primarily reported in ADAMTS10 mutated cases, this family was clinically and genetically a novel case.

Whole-Exome Sequencing Identifies Three Candidate Homozygous Variants in a Consanguineous Iranian Family with Autism Spectrum Disorder and Skeletal Problems.

Autism spectrum disorder (ASD) is characterized by 3 core symptoms with impaired social communication, repetitive behavior, and/or restricted interests in early childhood. As a complex neurodevelopmental disorder (NDD), the phenotype and severity of autism are extremely heterogeneous. Genetic factors have a key role in the etiology of autism. In this study, we investigated an Azeri Turkish family with 2 ASD-affected individuals to identify probable ASD-causing variants. First, the affected individuals were karyotyped in order to exclude chromosomal abnormalities. Then, whole-exome sequencing was carried out in one affected sibling followed by cosegregation analysis for the candidate variants in the family. In addition, SNP genotyping was carried out in the patients to identify possible homozygosity regions. Both proband and sibling had a normal karyotype. We detected 3 possible causative variants in this family: c.5443G>A; p.Gly1815Ser, c.1027C>T; p.Arg343Trp, and c.382A>G; p.Lys128Glu, which are in the FBN1, TF, and PLOD2 genes, respectively. All of the variants cosegregated in the family, and SNP genotyping revealed that these 3 variants are located in the homozygosity regions. This family serves as an example of a multimodal polygenic risk for a complex developmental disorder. Of these 3 genes, confluence of the variants in FBN1 and PLOD2 may contribute to the autistic features of the patient in addition to skeletal problems. Our study highlights the genetic complexity and heterogeneity of NDDs such as autism. In other words, in some patients with ASD, multiple rare variants in different loci rather than a monogenic state may contribute to the development of phenotypes.

Bi-allelic Mutations in ALDH5A1 is associated with succinic semialdehyde dehydrogenase deficiency and severe intellectual disability.

Homozygous mutations of ALDH5A1 have been reportedly associated with Succinic semialdehyde dehydrogenase deficiency (SSADHD) that affects gamma-aminobutyric acid (GABA) catabolism and evinces a wide range of clinical phenotype from mild intellectual disability to severe neurodegenerative disorders. We report clinical and molecular data of a Lor family with 2 affected members presenting with severe intellectual disability, developmental delay, and generalized tonic-clonic seizures. A comprehensive genetic study that included whole-exome sequencing identified a homozygous missense substitution (NM_001080:c.G1321A:p.G441R) in ALDH5A1 (Aldehyde Dehydrogenase 5 Family Member A1) gene, consistent with clinical phenotype in the patients and co-segregating with the disease in the family. The non-synonymous mutation, p.G441R, affects a highly conserved amino acid residue, which is expected to cause a severe destabilization of the enzyme. Protein modeling demonstrated an impairment of the succinic semialdehyde (SSA) binding tunnel accessibility, and the anticipation of the protein folding stability and dynamics was a decrease in the free energy by 4.02 kcal/mol. Consistent with these in silico findings, excessive γ -hydroxybutyrate (GHB) could be detected in patients' urine as the byproduct of the GABA pathway. SSADHD, Succinic semialdehyde dehydrogenase deficiency; GABA, gamma-aminobutyric acid; ALDH5A1, Aldehyde Dehydrogenase 5 Family Member A1; GHB, γ -hydroxybutyrate; SSA, succinic semi aldehyde; WISC, Wechsler Intelligence Scale for Children; CNS, central nervous system ; EEG, electroencephalography; EEEF, empirical effective energy functions; ASD, autism spectrum disorder; ADHD, attention deficit hyperactivity disorder; IQ, intelligence quotient; EMG, electromyography; NCV, nerve conduction velocity; CP, cerebral palsy.

Investigation of Chromosomal Abnormalities and Microdeletion/ Microduplication(s) in Fifty Iranian Patients with Multiple Congenital Anomalies.

OBJECTIVE: Major birth defects are inborn structural or functional anomalies with long-term disability and adverse impacts on individuals, families, health-care systems, and societies. Approximately 20% of birth defects are due to chromosomal and genetic conditions. Inspired by the fact that neonatal deaths are caused by birth defects in about 20 and 10% of cases in Iran and worldwide respectively, we conducted the present study to unravel the role of chromosome abnormalities, including microdeletion/microduplication(s), in multiple congenital abnormalities in a number of Iranian patients. MATERIALS AND METHODS: In this descriptive cross-sectional study, 50 sporadic patients with Multiple Congenital Anomalies (MCA) were selected. The techniques employed included conventional karyotyping, fluorescence in situ hybridization (FISH), multiplex ligation-dependent probe amplification (MLPA), and array comparative genomic hybridisation (array-CGH), according to the clinical diagnosis for each patient. RESULTS: Chromosomal abnormalities and microdeletion/microduplication(s) were observed in eight out of fifty patients (16%). The abnormalities proved to result from the imbalances in chromosomes 1, 3, 12, and 18 in four of the patients. However, the other four patients were diagnosed to suffer from the known microdeletions of 22q11.21, 16p13.3, 5q35.3, and 7q11.23. CONCLUSION: In the present study, we report a patient with 46,XY, der(18)[12]/46,XY, der(18), +mar[8] dn presented with MCA associated with hypogammaglobulinemia. Given the patient's seemingly rare and highly complex chromosomal abnormality and the lack of any concise mechanism presented in the literature to justify the case, we hereby propose a novel mechanism for the formation of both derivative and ring chromosome 18. In addition, we introduce a new 12q abnormality and a novel association of an Xp22.33 duplication with 1q43q44 deletion syndrome. The phenotype analysis of the patients with chromosome abnormality would be beneficial for further phenotype-genotype correlation studies.

A Pathogenic Homozygous Mutation in The Pleckstrin Homology Domain of RASA1 Is Responsible for Familial Tricuspid Atresia in An Iranian Consanguineous Family.

OBJECTIVE: Tricuspid atresia (TA) is a rare life-threatening form of congenital heart defect (CHD). The genetic mechanisms underlying TA are not clearly understood. According to previous studies, the endocardial cushioning event, as the primary sign of cardiac valvulogenesis, is governed by several overlapping signaling pathways including Ras/ ERK pathway. RASA1, a regulator of cardiovascular development, is involved in this pathway and its haploinsufficiency (due to heterozygous mutations) has been identified as the underlying etiology of the autosomal dominant capillary malformation/arteriovenous malformation (CM/AVM). MATERIALS AND METHODS: In this prospective study, we used whole exome sequencing (WES) followed by serial bioinformatics filtering steps for two siblings with TA and early onset CM. Their parents were consanguineous which had a history of recurrent abortions. Patients were carefully assessed to exclude extra-cardiac anomalies. RESULTS: We identified a homozygous RASA1 germline mutation, c.1583A>G (p.Tyr528Cys) in the family. This mutation lies in the pleckstrin homology (PH) domain of the gene. The parents who were heterozygous for this variant displayed CM. CONCLUSION: This is the first study reporting an adverse phenotypic outcome of a RASA1 homozygous mutation. Here, we propose that the phenotypic consequence of the homozygous RASA1 p.Tyr528Cys mutation is more serious than the heterozygous type. This could be responsible for the TA pathogenesis in our patients. We strongly suggest that parents with CM/AVM should be investigated for RASA1 heterozygous mutations. Prenatal diagnosis and fetal echocardiography should also be carried out in the event of pregnancy in heterozygous parents.

A novel splicing variant in FLNC gene responsible for a highly penetrant familial dilated cardiomyopathy in an extended Iranian family.

Recent achievements in the genetic diagnosis of Dilated Cardiomyopathy (DCM) have disclosed rare variants in numerous genes encoding different types of myocardial proteins. However, the causative gene underlying the pathogenesis of about 60% of familial cases with DCM has not been identified. One novel gene introduced in 2016 for cardiac-restricted DCM is FLNC. In this study, we applied Whole Exome Sequencing (WES) and bioinformatics-based methods to a member of an extended non-consanguineous family with DCM history accompanied with fatal arrhythmia in at least four consecutive generations. We found a novel splice-site mutation in FLNC gene (c.2389+1G>A) which cosegregated with all symptomatic individuals in the family. Computational prediction software tools as well as RT-PCR method were used to evaluate the impact of the FLNC splice site mutation. This substitution leads to exon 15th donor-site disruption and exon skipping, which would result in a premature stop codon three aminocids downstream of the mutation site. The aberrantly mRNA transcript can induce nonsense-mediated mRNA decay. Although carrier individuals show remarkable variable expression regarding the severity of DCM as well as the disease age of onset, a highly penetrant fatal arrhythmia was found to be shared between them. We strongly suggest that the involvement of FLNC gene, due to haploinsufficiency, should be considered in familial cases with DCM, especially if accompanied with arrhythmia and increased incidence of sudden cardiac death.