Clinical phenotype and the lack of mutations in the CHRNG, CHRND, and CHRNA1 genes in two Indian families with Escobar syndrome

The objective of this study was to report the clinical phenotype and genetic analysis of two Indian families with Escobar syndrome (ES). The diagnosis of ES in both families was made on the basis of published clinical features. Blood samples were collected from members of both families and used in genomic DNA isolation. The entire coding regions and intron-exon junctions of the ES gene CHRNG (cholinergic receptor, nicotinic, gamma), and two other related genes, CHRND and CHRNA1, were amplified and sequenced to search for mutations in both families. Both families show a typical form of ES. Sequencing of the entire coding regions including the intron-exon junctions of the three genes did not yield any mutations in these families. In conclusion, it is possible that the mutations in these genes are located in the promoter or deep intronic regions that we failed to identify or the ES in these families is caused by mutations in a different gene. The lack of mutations in CHRNG has also been reported in several families, suggesting the possibility of at least one more gene for this syndrome. Clin Dysmorphol 22:54-58 (C) 2013 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.

Whole exome sequencing identifies a novel splice-site mutation in ADAMTS17 in an Indian family with Weill-Marchesani syndrome

Purpose: Weill-Marchesani syndrome (WMS) is a rare connective tissue disorder, characterized by short stature, micro-spherophakic lens, and stubby hands and feet (brachydactyly). WMS is caused by mutations in the FBN1, ADAMTS10, and LTBP2 genes. Mutations in the LTBP2 and ADAMTS17 genes cause a WMS-like syndrome, in which the affected individuals show major features of WMS but do not display brachydactyly and joint stiffness. The main purpose of our study was to determine the genetic cause of WMS in an Indian family. Methods: Whole exome sequencing (WES) was used to identify the genetic cause of WMS in the family. The cosegregation of the mutation was determined with Sanger sequencing. Reverse transcription (RT)-PCR analysis was used to assess the effect of a splice-site mutation on splicing of the ADAMTS17 transcript. Results: The WES analysis identified a homozygous novel splice-site mutation c.873+1G>T in a known WMS-like syndrome gene, ADAMTS17, in the family. RT-PCR analysis in the patient showed that exon 5 was skipped, which resulted in the deletion of 28 amino acids in the ADAMTS17 protein. Conclusions: The mutation in the WMS-like syndrome gene ADAMTS17 also causes WMS in an Indian family. The present study will be helpful in genetic diagnosis of this family and increases the number of mutations of this gene to six.

Mapping Post-translational Modifications of Mammalian Testicular Specific Histone Variant TH2B in Tetraploid and Haploid Germ Cells and Their Implications on the Dynamics of Nucleosome Structure

Histones regulate a variety of chromatin templated events by their post-translational modifications (PTMs). Although there are extensive reports on the PTMs of canonical histones, the information on the histone variants remains very scanty. Here, we report the identification of different PTMs, such as acetylation, methylation, and phosphorylation of a major mammalian histone variant TH2B. Our mass spectrometric analysis has led to the identification of both conserved and unique modifications across tetraploid spermatocytes and haploid spermatids. We have also computationally derived the 3-dimensional model of a TH2B containing nucleosome in order to study the spatial orientation of the PTMs identified and their effect on nucleosome stability and DNA binding potential. From our nucleosome model, it is evident that substititution of specific amino acid residues in TH2B results in both differential histone-DNA and histone-histone contacts. Furthermore, we have also observed that acetylation on the N-terminal tail of TH2B weakens the interactions with the DNA. These results provide direct evidence that, similar to somatic H2B, the testis specific histone TH2B also undergoes multiple PTMs, suggesting the possibility of chromatin regulation by such covalent modifications in mammalian male germ cells.

Whole exome sequencing in an Indian family links Coats plus syndrome and dextrocardia with a homozygous novel CTC1 and a rare HES7 variation

Background: Coats plus syndrome is an autosomal recessive, pleiotropic, multisystem disorder characterized by retinal telangiectasia and exudates, intracranial calcification with leukoencephalopathy and brain cysts, osteopenia with predisposition to fractures, bone marrow suppression, gastrointestinal bleeding and portal hypertension. It is caused by compound heterozygous mutations in the CTC1 gene. Case presentation: We encountered a case of an eight-year old boy from an Indian family with manifestations of Coats plus syndrome along with an unusual occurrence of dextrocardia and situs inversus. Targeted resequencing of the CTC1 gene as well as whole exome sequencing (WES) were conducted in this family to identify the causal variations. The identified candidate variations were screened in ethnicity matched healthy controls. The effect of CTC1 variation on telomere length was assessed using Southern blot. A novel homozygous missense mutation c.1451A > C (p.H484P) in exon 9 of the CTC1 gene and a rare 3'UTR known dbSNP variation (c.*556 T > C) in HES7 were identified as the plausible candidates associated with this complex phenotype of Coats plus and dextrocardia. This CTC1 variation was absent in the controls and we also observed a reduced telomere length in the affected individual's DNA, suggesting its likely pathogenic nature. The reported p.H484P mutation is located in the N-terminal 700 amino acid regionthat is important for the binding of CTC1 to ssDNA through its two OB domains. WES data also showed a rare homozygous missense variation in the TEK gene in the affected individual. Both HES7 and TEK are targets of the Notch signaling pathway. Conclusions: This is the first report of a genetically confirmed case of Coats plus syndrome from India. By means of WES, the genetic variations in this family with unique and rare complex phenotype could be traced effectively. We speculate the important role of Notch signaling in this complex phenotypic presentation of Coats plus syndrome and dextrocardia. The present finding will be useful for genetic diagnosis and carrier detection in the family and for other patients with similar disease manifestations.