Search

Background: The muscle Ras (MRAS) gene resides on chromosome 3q22.3 and encodes a member of the membrane-associated Ras small GTPase proteins, which function as signal transducers in multiple processes including cell growth and differentiation. Its role in cardiovascular disease is not fully understood yet. In a preliminary study in heterozygous familial hypercholesterolaemia, we identified a locus linking the early onset of coronary artery disease (CAD) to chromosome 3q.22 and elected to sequence the MRAS gene using the MegaBACE DNA analysis system. In the present study, we investigated the association of seven single-nucleotide polymorphisms (SNPs) at this locus with CAD and its dyslipidaemia-related risk traits in 4,650 Saudi angiographed individuals using TaqMan assays by the Applied Biosystems real-time Prism 7900HT Sequence Detection System. Results: Among the studied SNPs, rs6782181 (p = 0.017) and rs9818870T (p = 0.009) were associated with CAD following adjustment for sex, age and other confounding risk factors. The rs6782181_GG also conferred risk for obesity (1,764 cases vs. 2,586 controls) [1.16(1.03-1.30); p = 0.017], hypercholesterolaemia (1,686 vs. 2,744) [1.23(1.02-1.47); p = 0.019], hypertriglyceridaemia (1,155 vs. 3,496) [1.29(1.01-1.45); p = 0.043] and low high-density lipoprotein-cholesterol (lHDL-chol) levels (1,935 vs. 2,401) [1.15(1.02-1.30); p = 0.023] after adjustment. Additionally, rs253662_(CT+TT) [1.16(1.01-1.32); p = 0.030] was associated with lHDL-chol levels. Interestingly, rs253662 (p =0.014) and rs6782181 (p = 0.019) were protective against acquiring high low-density lipoprotein-cholesterol (hLDL-chol) levels (p = 0.014), while rs1720819 showed similar effects against CAD (p < 0.0001). More importantly, a 7-mer haplotype, ACCTGAC (χ²=7.66; p = 0.0056), constructed from the studied SNPs, its 6-mer derivative CCTGAC (χ²=6.90; p = 0.0086) and several other shorter derivatives conferred risk for obesity. hLDL-chol was weakly linked to CTAA (χ²=3.79; p = 0.052) and CCT (χ²=4.32; p = 0.038), while several other haplotypes were protective against both obesity and hLDL-chol level. Conclusion: Our results demonstrate that the genomic locus for the MRAS gene confers risk for CAD, obesity and dyslipidaemia and point to the possible involvement of other genes or regulatory elements at this locus, rather than changes in the M-Ras protein function, in these events. [ABSTRACT FROM AUTHOR]

The role of the KIAA0391 and PSMA6 genes in predisposing individuals to disease is still not fully understood. We evaluated by molecular beacon-based genotyping assays the roles of five single nucleotide polymorphisms (SNPs) in the chromosomal region 14q13.2 harbouring the KIAA0391 and PSMA6 gene cluster in coronary artery disease (CAD) in the Saudi population. Two of the studied SNPs rs8008319 (denoted as 1) and rs7157492 (2), reside in the KIAA0391 locus, two others rs1048990 (3) and rs12878391 (4) are components of the PSMA6, while rs4981283 (5) resides downstream of both genes. In a study involving 1071 patients and 929 controls, none of the studied SNPs showed significant association with CAD. In contrast, two haplotypes consisting of 1A-2G-3C-4A-5A [O.R.(95% C.I.) = 1.49(0.95–2.35); p = 0.022] and 1A-2G-3G-4A-5A [2.24(0.84–5.98); p = 0.031] conferred risk for both CAD and myocardial infarction (MI) in a five-SNP locus model, while another comprising 1A-2G-3C-4A-5G [2.24(0.84–5.98); p = 0.079] showed a borderline association. One haplotype consisting of 1T-2G-3C-4G-5A [0.79(0.59–1.05); p = 0.015] exhibited protective properties and another, 1T-2G-3C-4A-5G [0.20(0.03–139); p = 0.073], showed a similar but weaker trend. Our study identified haplotypes in the chromosomal region encompassing the KIAA0391 and PSMA6 genes as a possible genetic link between CAD and MI. These results also suggest that haplotypes may be more informative than individual SNPs in identifying risk factors for disease. [ABSTRACT FROM AUTHOR]

Abstract: Background: Heterogeneous familial hypercholesterolemia (HFH) partly underlies polymorphic changes in the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB) and protein convertase subtilisin/kexin type 9 (PCSK9), exhibiting intra-ethnical variations in its clinical features. Methods: We employed the Affymetrix whole genome scan 250 sty1 array to characterize possible genomic linkage to heterozygous familial hypercholesterolemia (HFH) and sequencing techniques to identify related mutations in the above three genes in a Saudi family of 11 individuals harbouring clinical features of FH. The propositus had early onset of coronary artery disease (CAD) and very significantly elevated cholesterol (Chol) level of 10.1mmol/L and LDL-cholesterol (LDL-C) of 7.9mmol/L as well as low HDL-C level of 0.51mmol/L, while 4 siblings were affected with HFH. Results: Whole genome scan for the autosomal dominant model showed high homology for the affected individuals in several regions including chromosomes (chr) 1 and 2 which harbour PCSK9 and APOB, respectively. Subsequent sequencing of the coding regions of these two and LDLR identified 11 single nucleotide polymorphisms (SNPs) in the LDLR, 8 in the APOB and 6 in the PCSK9 genes. The propositus uniquely carried the homozygous mutant genotypes (haplotype) for all 11 LDLR SNPs, in direct contrast to the only normolipidemic sibling and a control who carried the homozygous wild type genotypes at these loci. Another set of 7 SNPs in the APOB also isolated with FH. Interestingly, all family members were heterozygous for all except the rs2228671 C>T of this gene, for which the mother shared the C/C genotype with the propositus, two other affected off-springs and a control, all of whom exhibited low HDL-C levels. A confirmation experiment involving 70 individuals harbouring low HDL-C revealed 74.3% of them as C/C carriers. Conclusions: Our study identified a haplotype in the LDLR as a marker for early onset of CAD, and rs2228671 C>T in the LDLR in association with a reduction in HDL-C concentrations in FH. The results also substantiate the notion of genetic heterogeneity in HFH, underlining the essence of recognizing ethnic-specific gene variability as a potential basis for appropriate management of FH. [Copyright &y& Elsevier]