A TBX5 NONSENSE MUTATION IN SIBLINGS WITH DIVERGENT PHENOTYPES ASSOCIATED WITH ISOLATED SEPTAL DEFECTS

  Objective: Heart septal defects (HSD) account for 50% of the congenital heart malformations and are characterized by the hole in the wall of tissue which separates the heart chambers. The known causes of the SD are multifactorial and complex inheritance.Methods: Isolated 15 subjects with ostium secundum atrial SD (OS-ASD) and one subject with perimembranous ventricular SD (VSD) among 125 clinically diagnosed SD were included in the study. Sanger sequencing was performed for all the exons of TBX5 genes using genomic DNA of these patients.Results: Sequence variation c.444 G>A substitution, leads to the alteration of tryptophan residue into premature stop codon at codon 148. We observed a divergent phenotype within a family of four, where one sibling and the mother had OS-ASD, another sibling had phenotype of perimembranous VSD, and the father had normal genotype.Conclusion: We believe that this novel sequence variant in TBX5 gene is one of the factors in the SD and may hold a key determining the role of TBX5 gene in the heart development

ANALYSIS OF GENE COPY NUMBER VARIATIONS IN PATIENTS WITH CARDIAC SEPTAL DEFECTS USING MULTIPLEX LIGATION-DEPENDENT PROBE AMPLIFICATION: CNVs analysis in CSDs

Objective: Cardiac septal defects (CSDs), the most common human congenital heart malformations are complex and heterogeneous. Progress in molecular biology has helped to identify many genes responsible for cardiac morphogenesis. However, etiologic factors in familial as well as isolated syndromes are being identified; the root genetic cause still needs to be resolved and its mechanism is yet to be revealed. The objective of this study is to identify DNA copy number variations (CNVs) and their possible association with septal defects. Methods: Multiplex ligation-dependent probe amplification (MLPA) was used to detect DNA copy number in non-syndromic CSDs using the P311-A1 Kit consisting of probes for the key genes, namely, NKX2-5 (NK2 transcription factor related, locus 5), GATA4 (GATA binding protein 4), TBX5 (T-box transcription factor), bone morphogenetic protein 4, and CRELD1 (cysteine rich with EGF-like domains 1). Results: We studied 124 clinically diagnosed CSD subjects, of which 111 (89.5%) had atrial septal defects and 13 (10.5%) had ventricular septal defects. MLPA assay was carried out in all these patients after a thorough clinical and cytogenetic screening. CNVs were identified in 16 (12.9%) cases, of which heterozygous deletions and heterozygous duplications were detected (8 patients each) with apparent phenotypes. Conclusion: MLPA could be a useful assay for the detection of CNVs and to be adopted as the first line of screening in patients with congenital heart diseases