Epistatic interactions in idiopathic pulmonary arterial hypertension.

BACKGROUND: Idiopathic pulmonary arterial hypertension (IPAH) is a poorly understood complex disorder, which results in progressive remodeling of the pulmonary artery that ultimately leads to right ventricular failure. A two-hit hypothesis has been implicated in pathogenesis of IPAH, according to which the vascular abnormalities characteristic of PAH are triggered by the accumulation of genetic and/or environmental insults in an already existing genetic background. The multifactor dimensionality reduction (MDR) analysis is a statistical method used to identify gene-gene interaction or epistasis and gene-environment interactions that are associated with a particular disease. The MDR method collapses high-dimensional genetic data into a single dimension, thus permitting interactions to be detected in relatively small sample sizes. AIM: To identify and characterize polymorphisms/genes that increases the susceptibility to IPAH using MDR analysis. MATERIALS AND METHODS: A total of 77 IPAH patients and 100 controls were genotyped for eight polymorphisms of five genes (5HTT, EDN1, NOS3, ALK-1, and PPAR-γ2). MDR method was adopted to determine gene-gene interactions that increase the risk of IPAH. RESULTS: With MDR method, the single-locus model of 5HTT (L/S) polymorphism and the combination of 5HTT(L/S), EDN1(K198N), and NOS3(G894T) polymorphisms in the three-locus model were attributed to be the best models for predicting susceptibility to IPAH, with a P value of 0.05. CONCLUSION: MDR method can be useful in understanding the role of epistatic and gene-environmental interactions in pathogenesis of IPAH.

Genetic variations of ß-MYH7 in hypertrophic cardiomyopathy and dilated cardiomyopathy.

CONTEXT: Hypertrophic cardiomyopathy (HCM) is known to be manifested by mutations in 12 sarcomeric genes and dilated cardiomyopathy (DCM) is known to manifest due to cytoskeletal mutations. Studies have revealed that sarcomeric mutations can also lead to DCM. Therefore, in the present study, we have made an attempt to compare and analyze the genetic variations of beta-myosin heavy chain gene (ß-MYH7), which are interestingly found to be common in both HCM and DCM. The underlying pathophysiological mechanism leading to two different phenotypes has been discussed in this study. Till date, about 186 and 73 different mutations have been reported in HCM and DCM, respectively, with respect to this gene. AIM: The screening of ß-MYH7 gene in both HCM and DCM has revealed some common genetic variations. The aim of the present study is to understand the pathophysiological mechanism underlying the manifestation of two different phenotypes. MATERIALS AND METHODS: 100 controls, 95 HCM and 97 DCM samples were collected. Genomic DNA was extracted following rapid nonenzymatic method as described by Lahiri and Nurnberger (1991), and the extracted DNA was later subjected to polymerase chain reaction (PCR) based single stranded conformation polymorphism (SSCP) analysis to identify single nucleotide polymorphism (SNP)s/mutations associated with the diseased phenotypes. RESULTS AND CONCLUSION: Similar variations were observed in ß-MYH7 exons 7, 12, 19 and 20 in both HCM and DCM. This could be attributed to impaired energy compromise, or to dose effect of the mutant protein, or to even environmental factors/modifier gene effects wherein an HCM could progress to a DCM phenotype affecting both right and left ventricles, leading to heart failure.

Endothelin-1 and endothelial nitric oxide polymorphisms in idiopathic pulmonary arterial hypertension.

Idiopathic Pulmonary arterial hypertension (IPAH) is a debilitating disease associated with very poor prognosis. The disease is characterised by endothelial dysfunction, smooth muscle proliferation and insitu thrombosis in the pulmonary artery, eventually leading to right ventricular failure. Two of the key endothelial mediators implicated in the pathogenesis of IPAH are endothelin-1 (EDN1) and nitric oxide (NO). EDN1 is a potent endogenous vasoconstrictor whereas NO is a vasodilator. In the present study screening of the EDN1 gene (EDN1) and NOS3 polymorphisms was taken up, to evaluate their association with IPAH. A significant association of EDN1 3A/4A polymorphism (+138 A; rs10478694) (OR-3.485; CI-1.254, 9.999; p=0.013) and EDN1 Lys198Asn polymorphism (G/T, rs5370) (OR-3.378, CI-1.104, 10.582; p=0.03) with IPAH was observed. Our results indicate that EDN1 polymorphisms in interaction with other genetic markers may play a significant role in individual's susceptibility to the disease and its clinical progression.

t-plasminogen activator inhibitor-1 polymorphism in idiopathic pulmonary arterial hypertension.

AIM: The aim of the present study was to identify the possible genotypic association of 3'UTR Hind III polymorphism of Plasminogen activator Inhibitor-1 (PAI-1) gene with idiopathic pulmonary arterial hypertension (IPAH). BACKGROUND: IPAH is a disorder with abnormally raised mean pulmonary arterial pressure and increase in the resistance to blood flow in pulmonary artery. One of the pathological features seen is development of intraluminal thrombin deposition leading to thrombosis. Plasminogen activator inhibitor-1 is an important inhibitor of the fibrinolytic system; its up-regulation may suppress fibrinolysis and result in an increased risk of thrombosis. METHOD: Blood samples from 54 IPAH patients and 100 healthy voluntary donors were analyzed by PCR-RFLP method for 3'UTR Hind III polymorphism. RESULTS AND DISSCUSSION: A significant association of Hd2 allele with the disease was observed. Raised mean level of right ventricular systolic pressure was observed in the Hd2/Hd2 genotypic patients, strengthening the role of Hd2 allele in the disease progression. Our data suggests an association of Hd2/Hd2 genotype, which may lead to the up-regulation of PAI-1 gene leading to increased levels of PAI-1, which is seen in IPAH. PAI-1 competes with plasminogen activators and hinders the normal mechanism of plasminogen activation system and leads to thrombosis and formation of plexiform lesions in the lung tissue, further strengthening its role in tissue remodeling and disease progression.