Identification of Variants and Mutational Analyses of Cardiac Myosin-binding Protein C (MYBPC3) Gene of Adult Bangladeshi Patients with Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most prevalent genetic hereditary cardiomyopathy characterized by sudden cardiac death. Mutations in the MYBPC3 gene are often the most prevalent genetic abnormality in HCM with a prevalence ranging from 20.0 to 42.0%. The mutation spectrum is available for different countries, but such studies are lacking in the Asian population including Bangladeshi patients. A cross-sectional descriptive study was conducted for mutation analysis of the whole MYBPC3 gene on a cohort of 75 HCM Bengali Bangladeshi probands through Next Generation Sequencing at the Genetic Research Lab of Bangabandhu Sheikh Mujib Medical University from 2016 to 2019. The structural and functional impact of the mutations was further analyzed by in silico process. We analyzed the data and found 103 variants in 102 locations in the MYBPC3 gene. Variants were identified in both the coding region and the non-coding region. We found one possibly novel variant in the MYBPC3 gene. The findings of this research will help to develop a genetic database of HCM which will help in the early diagnosis and proper management of HCM patients in Bangladesh. One pathogenic splice donor variant (47356592 C >T) was found in the intronic region. Among the variants in the coding region, one missense mutation was pathogenic (NP₋000247.2: p.Asp770Asn) which was found in seven patients and another one is of conflicting interpretations of pathogenicity (NP₋000247.2: p.Ser217Gly) which was found in two patients. We have identified one in-frame deletion (NP₋000247.2: p.Ala433del) that is possible a novel variant responsible for the development of HCM.

The Aspect of NK2 Transcription Factor Related Locus-5 (NKX2.5) Gene Mutations in Bangladeshi Atrial Septal Defect (ASD) patients and 2D Relationship with their Age

Atrial septal defect (ASD) is a developmental defect of the heart which arises from the congenital abnormality of interatrial septum that perturbs the normal blood flow. Development of the heart is a complex biological process regulated by numerous genetic and environmental factors. During this process DNA binding proteins Myocardin, NKX2.5 (NK2 Transcription Factor Related Locus-5) and GATA4 (GATA Binding Protein-4) function by binding to SRF (Serum Response Factor) which is also a key regulator of myogenic terminal differentiation and frequently results in mitogenesis. Several studies suggest that mutations in the homeodomain containing transcription factor, NKX2.5, is implicated with atrial septal defect. This cross sectional descriptive study was done to investigate the frequency of NKX2.5 gene mutations among the patient with ASD who were undergoing surgical repair at the National Institute of Cardiovascular Diseases (NICVD) and National Heart Foundation and Research Institute (NHF&RI), Dhaka from July 2010 to June 2011. Patients presented with ASD at any age of both sexes were selected as study population. We found six distinct polymorphic sites among Bangladeshi population. Among six polymorphic sites, two were located at position 487 and 495. These were present in around 80% of the affected individuals. However they were not present in control population. Our study also revealed that mutations present in the downstream sites or towards the end of the genes are restricted to older people, whereas mutations present towards the 5' site is common to population of all ages. This interesting relationship has encouraged us to raise two new hypotheses.

Effects of inorganic phosphorus compounds on the hydrolysis of phosphatidylcholine liposomes by phospholipid-deacylating enzymes

Structural requirements of inorganic phosphorus compounds as specific activators or inhibitors for phospholipase A2 and phospholipase B were investigated using orthophosphate, pyrophosphate and polyphosphate. It was observed that orthophosphate and pyrophosphate stimulated the activities of phospholipase A2 from bee venom, snake (Naja naja) venom and pig pancreas, and also phospholipase B from the yeast Torulaspora delbrueckii. However, polyphosphate was found to act as an inhibitor for phospholipase A2 in the above species and also for phospholipase B from T. delbrueckii. Orthophosphate and pyrophosphate induced gradual aggregation of liposome, but polyphosphate prolonged the lifetime of the liposome, suggesting that orthophosphate and pyrophosphate destabilize the bilayer structure of phosphatidylcholine and polyphosphate stabilizes it.

Cloning and sequencing of phospholipase B gene from the yeast Torulaspora delbrueckii

The extracellular phospholipase B gene from baker's yeast Torulaspora delbrueckii was cloned and sequenced. Analysis of DNA sequence data revealed an open reading frame (ORF) encoding a 649-amino acid protein, that included amino acid sequences obtained from the purified enzyme. Comparison of these sequence data with the N-terminal amino acid sequence of the enzyme indicated that this secreted protein is synthesized as a large precursor with a 21-amino acid N-terminal extension to the mature enzyme of 628 amino acids. A homology search was carried out between phospholipase B from T. delbrueckii and Penicillium notatum. The deduced amino acid sequence of the cloned phospholipase B was homologous (about 50% identity) to phospholipase B from P. notatum, and contained six conserved regions. The transcriptional level of mRNA of the phospholipase B gene was higher in the cells from early exponential and stationary phases.

Calcium ion dependent interaction of inorganic phosphorus compounds with phosphatidylcholine

The translocation of orthophosphate, pyrophosphate, and polyphosphate into an organic phase was examined by means of the two-phase partition method. When the organic phase contained phosphatidylcholine (PtdCho), the phosphorus compounds translocated from the water-phase into the organic phase, depending on the concentrations of PtdCho and Ca2+, and the pH of the solution. Calcium ions were essential for the translocation. The concentration of Ca2+ necessary for the translocation appeared to depend on the molar concentration of the phosphorus compounds. Orthophosphate was translocated above pH 6.5, while pyrophosphate was translocated above pH 3.5. In contrast, polyphosphate was translocated in the whole pH range examined (pH 2.5-9.0), although approx. 9% of the total polyphosphate remained in the water-phase even at alkaline pH. These results suggest that phosphorus compounds can interact with PtdCho when the phosphorus compounds have formed complexes with Ca2+.