Identification of Genetic Variants Associated With Myocardial Infarction in Saudi Arabia.

The genetic variants associated with various genetic disorders have not been identified decisively in Saudi Arabia. Among these variants, six known for their association with coronary artery disease or myocardial infarction (MI) were studied on Saudi patients. Reference single nucleotide polymorphisms (SNPs) of these variants are rs5174, rs11591147, rs2259816, rs111245230, rs3782886 and rs2259820, referring to genes LRP8, PCSK9, HNF1A, SVEP1, BRAP and HNF1A, respectively. The analysis employed polymerase chain reaction panel coupled with mini-sequencing (SNapShot multiplex system) in order to identify these variants. A total of 100 MI patients and 103 healthy control individuals participated in this study. The six variants (SNPs) were evaluated for the risk of developing MI in the Saudi patients. Analysis of allele frequencies indicated that A allele of rs11591147 variant can be a protective allele, thus, is associated with the decreased risk of MI in Saudi individuals. Rare allele of rs111245230 variant (e.g., C allele) was extremely reduced, while rare allele of rs3782886 variant (e.g., G allele) does not exist in the ethnic signature of the Saudi population. This study elucidates the possible prediction of risk factors associated with severe diseases in Saudi population utilizing SNapShot multiplex system.

Whole exome sequencing of a consanguineous family identifies the possible modifying effect of a globally rare AK5 allelic variant in celiac disease development among Saudi patients.

Celiac disease (CD), a multi-factorial auto-inflammatory disease of the small intestine, is known to occur in both sporadic and familial forms. Together HLA and Non-HLA genes can explain up to 50% of CD's heritability. In order to discover the missing heritability due to rare variants, we have exome sequenced a consanguineous Saudi family presenting CD in an autosomal recessive (AR) pattern. We have identified a rare homozygous insertion c.1683_1684insATT, in the conserved coding region of AK5 gene that showed classical AR model segregation in this family. Sequence validation of 200 chromosomes each of sporadic CD cases and controls, revealed that this extremely rare (EXac MAF 0.000008) mutation is highly penetrant among general Saudi populations (MAF is 0.62). Genotype and allelic distribution analysis have indicated that this AK5 (c.1683_1684insATT) mutation is negatively selected among patient groups and positively selected in the control group, in whom it may modify the risk against CD development [p<0.002]. Our observation gains additional support from computational analysis which predicted that Iso561 insertion shifts the existing H-bonds between 400th and 556th amino acid residues lying near the functional domain of adenylate kinase. This shuffling of amino acids and their H-bond interactions is likely to disturb the secondary structure orientation of the polypeptide and induces the gain-of-function in nucleoside phosphate kinase activity of AK5, which may eventually down-regulates the reactivity potential of CD4+ T-cells against gluten antigens. Our study underlines the need to have population-specific genome databases to avoid false leads and to identify true candidate causal genes for the familial form of celiac disease.

Replication of GWAS Coding SNPs Implicates MMEL1 as a Potential Susceptibility Locus among Saudi Arabian Celiac Disease Patients.

Celiac disease (CD), a gluten intolerance disorder, was implicated to have 57 genetic susceptibility loci for Europeans but not for culturally and geographically distinct ethnic populations like Saudi Arabian CD patients. Therefore, we genotyped Saudi CD patients and healthy controls for three polymorphisms, that is, Phe196Ser in IRAK1, Trp262Arg in SH2B3, and Met518Thr in MMEL1 genes. Single locus analysis identified that carriers of the 518 Thr/Thr (MMEL1) genotype conferred a 1.6-fold increased disease risk compared to the noncarriers (OR = 2.6; 95% CI: 1.22-5.54; P < 0.01). This significance persisted even under allelic (OR = 1.55; 95% CI: 1.05-2.28; P = 0.02) and additive (OR = 0.35; 95% CI: 0.17-0.71; P = 0.03) genetic models. However, frequencies for Trp262Arg (SH2B3) and Phe196Ser (IRAK1) polymorphisms were not significantly different between patients and controls. The overall best MDR model included Met518Thr and Trp262Arg polymorphisms, with a maximal testing accuracy of 64.1% and a maximal cross-validation consistency of 10 out of 10 (P = 0.0156). Allelic distribution of the 518 Thr/Thr polymorphism in MMEL1 primarily suggests its independent and synergistic contribution towards CD susceptibility among Saudi patients. Lack of significant association of IRAK and SH2B3 gene polymorphisms in Saudi patients but their association in European groups suggests the genetic heterogeneity of CD.