Thymic Stromal Lymphopoietin (TSLP) gene variant rs1837253 is significantly associated with Asthma prevalence in Pakistani Pashtun women.

Asthma is a chronic inflammatory disease of the airways characterized by airway hyperresponsiveness and remodeling. Thymic stromal lymphopoietin (TSLP), a member of the interleukin-2 family of cytokines, is produced by activated lung and intestinal epithelial cells, mast, and other immune cells. Population-based studies identified associations between SNPs in the TSLP promoter region and asthma pathogenesis. In this study, we analyzed the genotypic association of TSLP rs1837253 with asthma predisposition in the Pashtun population of Khyber Pakhtunkhwa, Pakistan. Target DNA sequence of 250 asthmatics and an equal number of healthy individuals was PCR amplified, and allelic determination was performed by Sanger sequencing. Statistical analysis was conducted using chi-square tests and logistic regression analysis. Homozygous T/T genotype was frequent in the asthmatic subjects with a statistically significant level (P<0.05). Genetic models, including recessive, dominant, co-dominant, over-dominant, and additive were tested while adjusting allele frequencies with covariates (gender and age). Combined C/T and T/T individuals had higher odds ratios of 3.00, 1.91, and 1.73 in co-dominant, dominant, and additive models with statistically significant P-values of 0.029*, 0.022*, and 0.02*, respectively. T allele of rs1837253 was associated with increased susceptibility to asthma among Pashtuns, particularly in females, and we corroborate rs1837253 as a SNP of interest with a potential functional role.

Genetic spectrum of Saudi Arabian patients with antenatal cystic kidney disease and ciliopathy phenotypes using a targeted renal gene panel.

BACKGROUND: Inherited cystic kidney disorders are a common cause of end-stage renal disease. Over 50 ciliopathy genes, which encode proteins that influence the structure and function of the primary cilia, are implicated in cystic kidney disease. METHODS: To define the phenotype and genotype of cystic kidney disease in fetuses and neonates, we correlated antenatal ultrasound examination and postnatal renal ultrasound examination with targeted exon sequencing, using a renal gene panel. A cohort of 44 families in whom antenatal renal ultrasound scanning findings in affected cases included bilateral cystic kidney disease, echogenic kidneys or enlarged kidneys was investigated. RESULTS: In this cohort, disease phenotypes were severe with 36 cases of stillbirth or perinatal death. Extra renal malformations, including encephalocele, polydactyly and heart malformations, consistent with ciliopathy phenotypes, were frequently detected. Renal gene panel testing identified causative mutations in 21 out of 34 families (62%), where patient and parental DNA was available. In the remaining 10 families, where only parental DNA was available, 7 inferred causative mutations were found. Together, mutations were found in 12 different genes with a total of 13 novel pathogenic variants, including an inferred novel variant in NEK8. Mutations in CC2D2A were the most common cause of an antenatal cystic kidney disease and a suspected ciliopathy in our cohort. CONCLUSIONS: In families with ciliopathy phenotypes, mutational analysis using a targeted renal gene panel allows a rapid molecular diagnosis and provides important information for patients, parents and their physicians.

A study of the role of GATA4 polymorphism in cardiovascular metabolic disorders.

BACKGROUND: The study was designed to evaluate the association of GATA4 gene polymorphism with coronary artery disease (CAD) and its metabolic risk factors, including dyslipidaemic disorders, obesity, type 2 diabetes and hypertension, following a preliminary study linking early onset of CAD in heterozygous familial hypercholesterolaemia to chromosome 8, which harbours the GATA4 gene. RESULTS: We first sequenced the whole GATA4 gene in 250 individuals to identify variants of interest and then investigated the association of 12 single-nucleotide polymorphisms (SNPs) with the disease traits using Taqman chemistry in 4,278 angiographed Saudi individuals. Of the studied SNPs, rs804280 (1.14 (1.03 to 1.27); p = 0.009) was associated with CAD (2,274 cases vs 2,004 controls), hypercholesterolaemia (1,590 vs 2,487) (1.61 (1.03-2.52); p = 0.037) and elevated low-density lipoprotein-cholesterol (hLDLC) (575 vs 3,404) (1.87 (1.10-3.15); p = 0.020). Additionally, rs3729855_T (1.52 (1.09-2.11; p = 0.013)) and rs17153743 (AG + GG) (2.30 (1.30-4.26); p = 0.005) were implicated in hypertension (3,312 vs 966), following adjustments for confounders. Furthermore, haplotypes CCCGTGCC (χ2 = 4.71; p = 0.041) and GACCCGTG (χ2 = 3.84; p = 0.050) constructed from the SNPs were associated with CAD and ACCCACGC (χ2 = 6.58; p = 0.010) with myocardial infarction, while hypercholesterolaemia (χ2 = 3.86; p = 0.050) and hLDLC (χ2 = 4.94; p = 0.026) shared the AACCCATGT, and AACCCATGTC was associated with hLDLC (χ2 = 4.83; p = 0.028). A 10-mer GACCCGCGCC (χ2 = 7.59; p = 0.006) was associated with obesity (1,631 vs 2,362), and the GACACACCC (χ2 = 4.05; p = 0.044) was implicated in type 2 diabetes mellitus 2,378 vs 1,900). CONCLUSION: Our study implicates GATA4 in CAD and its metabolic risk traits. The finding also points to the possible involvement of yet undefined entities related to GATA4 transcription activity or gene regulatory pathways in events leading to these cardiovascular disorders.

The 3'-UTR of the adiponectin Q gene harbours susceptibility loci for atherosclerosis and its metabolic risk traits.

BACKGROUND: Adiponectin Q is a hormone that modulates several metabolic processes and contributes to the suppression of biochemical pathways leading to metabolic syndrome. Hence, polymorphic changes in the adiponectin Q (ADIPOQ) gene are likely to contribute to metabolic disorders, and consequently lead to atherosclerosis. In the present study, we performed a population-based association study for 8 SNPs in 4646 Saudi individuals (2339 CAD cases versus angiographed 2307 controls) by real-time PCR. METHODS: Linkage analysis was done by the Affymetrix Gene Chip array, sequencing by the MegaBACE DNA analysis system and genotyping accomplished by TaqMan chemistry with the Applied Biosystem real-time Prism 7900HT Sequence Detection System. RESULTS: The rs2241766 (TG + GG) [Odds ratio(95% Confidence Interval = 1.35(1.01-1.72); p = 0.015] and rs9842733A > T [1.48(1.01-2.07); p = 0.042] were associated with hypertension [HTN; 3541 cases vs 1101 controls), following adjustment for the presence of other cardiovascular risk traits. The rs2241766 (TG + GG) was further implicated in harbouring of low high density lipoprotein levels (LHDL; 1353 versus 2156 controls) [1.35(1.10-1.67); p = 0.005], but lost its association with obesity after the adjustment for confounders. Besides, low high density lipoprotein was also linked with rs6444174 (TC + CC) [1.28(1.05-1.59)]. On the other hand, while initial univariate logistic regression analysis pointed to rs1063537 C > T (p = 0.010), rs2082940 C > T (p = 0.035) and rs1063539 G > C (p = 0.035) as being associated with myocardial infarction, significance levels of these relationships were diminished following adjustment for the influence of confounding covariates. Interestingly, haplotyping showed that an 8-mer haplotype GTGCCTCA and several of its derivatives constructed from the studied SNPs were commonly implicated in MI (χ² = 4.12; p = 0.042), HTN (χ² = 6.40; p = 0.011) and OBS (χ² = 5.18; p = 0.023). CONCLUSION: These results demonstrate that the ADIPOQ 3'UTR harbours common susceptibility variants for metabolic risk traits and CAD, pointing to the importance of this region in atherosclerosis disease pathways.

Association of the angiotensinogen gene polymorphism with atherosclerosis and its risk traits in the Saudi population.

BACKGROUND: Angiotensinogen (AGT) constitutes a central component of the renin-angiotensin system that controls the systemic blood pressure and several other cardiovascular functions and may play an important role in atherosclerosis pathways. In this study, we employed TaqMan genotyping assays to evaluate the role of 8 AGT variants in primary hypertension (HTN), type 2 diabetes mellitus (T2DM), and obesity as a possible trigger of coronary artery disease (CAD) in a population of 4615 angiographed native Saudi individuals. METHODS: Linkage analysis was done by using the Affymetrix Gene Chip array, sequencing by using the MegaBACE DNA analysis system and genotyping accomplished by TaqMan chemistry using the Applied Biosystem real-time Prism 7900HT Sequence Detection System. RESULTS: Six variants, rs2067853 GG [Odds ratio(95% Confidence Interval) = 1.44(1.17-1.78); p = 0.001], rs7079 [1.49(1.20-1.85); p < 0.0001], rs699 G [1.19(1.08-1.13); p < 0.0001], rs3789679 A [1.51(1.14-1.99); p = 0.004], rs2148582 GG [1.31(1.11-1.55); p = 0.002] and rs5051 TC + CC [1.32(1.13-1.60); p = 0.001] conferred risk for HTN (3521 cases versus 1094 controls). The rs2067853 (p = 0.042), rs699G (p = 0.007) and rs5051 (p = 0.051) also conferred risk for myocardial infarction (MI; 2982 vs 1633), while rs3789679 A (p < 0.0001) and GA + AA (p < 0.0001) as well as rs4762G (p = 0.019) were associated with obesity (1576 vs 2458). However, while these variants appeared to be also associated with CAD (2323 vs 2292), only the rs7079G (p = 0.035) retained its significant relationship. Interestingly, among the haplotypes constructed from these SNPs, the baseline 8-mer haplotype, GGTGGGGT (χ² = 7.02; p = 0.0081) and another GGCGGAGT (χ² = 5.10; p = 0.024), together with several of their derivatives were associated with HTN. T2DM was associated with two 8-mer haplotypes, GGTAGGAC (χ2 = 5.66; p = 0.017) and ATTGAGAC (χ² = 5.93; p = 0.015), obesity with GGCGGAGT (χ² = 9.49; p = 0.0021) and MI was linked to ATTGGGAC (χ² = 6.68; p = 0.010) and GGTGGGAT (χ² = 4.25; p = 0.039). Furthermore, several causative haplotypes were also shared among the risk traits as well as with CAD. CONCLUSION: These results point to AGT as independently conferring risk for various cardiovascular traits, and possibly interacting with these traits in events leading to atherosclerosis.

Validation of Ion TorrentTM Inherited Disease Panel with the PGMTM Sequencing Platform for Rapid and Comprehensive Mutation Detection.

Quick and accurate molecular testing is necessary for the better management of many inherited diseases. Recent technological advances in various next generation sequencing (NGS) platforms, such as target panel-based sequencing, has enabled comprehensive, quick, and precise interrogation of many genetic variations. As a result, these technologies have become a valuable tool for gene discovery and for clinical diagnostics. The AmpliSeq Inherited Disease Panel (IDP) consists of 328 genes underlying more than 700 inherited diseases. Here, we aimed to assess the performance of the IDP as a sensitive and rapid comprehensive gene panel testing. A total of 88 patients with inherited diseases and causal mutations that were previously identified by Sanger sequencing were randomly selected for assessing the performance of the IDP. The IDP successfully detected 93.1% of the mutations in our validation cohort, achieving high overall gene coverage (98%). The sensitivity for detecting single nucleotide variants (SNVs) and short Indels was 97.3% and 69.2%, respectively. IDP, when coupled with Ion Torrent Personal Genome Machine (PGM), delivers comprehensive and rapid sequencing for genes that are responsible for various inherited diseases. Our validation results suggest the suitability of this panel for use as a first-line screening test after applying the necessary clinical validation.

Twenty novel mutations in BCKDHA, BCKDHB and DBT genes in a cohort of 52 Saudi Arabian patients with maple syrup urine disease.

Maple syrup urine disease (MSUD), an autosomal recessive inborn error of metabolism due to defects in the branched-chain α-ketoacid dehydrogenase (BCKD) complex, is commonly observed among other inherited metabolic disorders in the kingdom of Saudi Arabia. This report presents the results of mutation analysis of three of the four genes encoding the BCKD complex in 52 biochemically diagnosed MSUD patients originating from Saudi Arabia. The 25 mutations (20 novel) detected spanned across the entire coding regions of the BCKHDA, BCKDHB and DBT genes. There were no mutations found in the DLD gene in this cohort of patients. Prediction effects, conservation and modelling of novel mutations demonstrated that all were predicted to be disease-causing. All mutations presented in a homozygous form and we did not detect the presence of a "founder" mutation in any of three genes. In addition, prenatal molecular genetic testing was successfully carried out on chorionic villus samples or amniocenteses in 10 expectant mothers with affected children with MSUD, molecularly characterized by this study.

Clinical heterogeneity of PLA2G6-related Parkinsonism: analysis of two Saudi families.

BACKGROUND: Recessive mutations in PLA2G6 have been associated with different neurodegenerative disorders, including infantile neuroaxonal dystrophy, neurodegeneration with brain iron accumulation and more recently, early-onset dystonia parkinsonism. METHOD: Targeted-next generation sequencing using a custom Neurology panel, containing 758 OMIM-listed genes implicated in neurological disorders, was carried out in two index cases from two different Saudi families displaying early-onset levodopa-responsive Parkinsonism with pyramidal signs and additional clinical features. The detected mutations were verified in the index cases and available family members by direct sequencing. RESULTS AND CONCLUSION: We identified a previously described PLA2G6 homozygous p.R741Q mutation in three affected and two asymptomatic individuals from two Saudi families. Our finding reinforces the notion of the broadness of the clinical spectrum of PLA2G6-related neurodegeneration.

The Affymetrix DMET Plus platform reveals unique distribution of ADME-related variants in ethnic Arabs.

BACKGROUND: The Affymetrix Drug Metabolizing Enzymes and Transporters (DMET) Plus Premier Pack has been designed to genotype 1936 gene variants thought to be essential for screening patients in personalized drug therapy. These variants include the cytochrome P450s (CYP450s), the key metabolizing enzymes, many other enzymes involved in phase I and phase II pharmacokinetic reactions, and signaling mediators associated with variability in clinical response to numerous drugs not only among individuals, but also between ethnic populations. MATERIALS AND METHODS: We genotyped 600 Saudi individuals for 1936 variants on the DMET platform to evaluate their clinical potential in personalized medicine in ethnic Arabs. RESULTS: Approximately 49% each of the 437 CYP450 variants, 56% of the 581 transporters, 56% of 419 transferases, 48% of the 104 dehydrogenases, and 58% of the remaining 390 variants were detected. Several variants, such as rs3740071, rs6193, rs258751, rs6199, rs11568421, and rs8187797, exhibited significantly either higher or lower minor allele frequencies (MAFs) than those in other ethnic groups. DISCUSSION: The present study revealed some unique distribution trends for several variants in Arabs, which displayed partly inverse allelic prevalence compared to other ethnic populations. The results point therefore to the need to verify and ascertain the prevalence of a variant as a prerequisite for engaging it in clinical routine screening in personalized medicine in any given population.

Parkinson's Disease in Saudi Patients: A Genetic Study.

Parkinson's disease (PD) is one of the major causes of parkinsonism syndrome. Its characteristic motor symptoms are attributable to dopaminergic neurons loss in the midbrain. Genetic advances have highlighted underlying molecular mechanisms and provided clues to potential therapies. However, most of the studies focusing on the genetic component of PD have been performed on American, European and Asian populations, whereas Arab populations (excluding North African Arabs), particularly Saudis remain to be explored. Here we investigated the genetic causes of PD in Saudis by recruiting 98 PD-cases (sporadic and familial) and screening them for potential pathogenic mutations in PD-established genes; SNCA, PARKIN, PINK1, PARK7/DJ1, LRRK2 and other PD-associated genes using direct sequencing. To our surprise, the screening revealed only three pathogenic point mutations; two in PINK1 and one in PARKIN. In addition to mutational analysis, CNV and cDNA analysis was performed on a subset of patients. Exon/intron dosage alterations in PARKIN were detected and confirmed in 2 cases. Our study suggests that mutations in the ORF of the screened genes are not a common cause of PD in Saudi population; however, these findings by no means exclude the possibility that other genetic events such as gene expression/dosage alteration may be more common nor does it eliminate the possibility of the involvement of novel genes.

ILDR1: Novel mutation and a rare cause of congenital deafness in the Saudi Arabian population.

Hearing impairment is the common human sensorineural disorder and is a genetically heterogeneous phenotype for which more than 100 genomic loci have been mapped so far. ILDR1 located on chromosome 3q13.33, encodes a putative transmembrane receptor containing an immunoglobulin-like domain. We used a combination of autozygosity mapping and candidate gene sequencing to identify a novel mutation in ILDR1, as a causative gene for autosomal-recessive non-syndromic hearing loss (arNSHL) in a consanguineous Saudi family with three affected children. Autozygosity mapping identified a shared region between the affected individuals encompassing ILDR1 on chromosome 3q13.12-3q22.1. Sequencing revealed homozygous 9 base pair duplication, resulting in an in-frame duplication of three amino acids p.(Asn109_Pro111dup). The mutation was segregating with the disease phenotype and is predicted to be pathogenic by SIFT and PROVEAN. The identified mutation is located in the immunoglobulin-type domain of the ILDR1 protein. In silico analysis using I-TASSER server and PyMOL offers the first predictions on the structural and functional consequences of this mutation. To our knowledge, this is the first ILDR1 mutation identified in a Saudi family. Identification of ILDR1 mutation in only one of 100 Saudi familial and sporadic individuals with hearing loss suggests that this mutation is unique to this family and that ILDR1 should be considered as a rare cause of congenital deafness among Saudi Arabian population. Our data also confirms the evidence for ILDR1 allelic heterogeneity and expands the number of familial arNSHL-associated ILDR1 gene mutations.

A new susceptibility locus for myocardial infarction, hypertension, type 2 diabetes mellitus, and dyslipidemia on chromosome 12q24.

We examined the role of hepatic nuclear factor-1 alpha (HNF1a) gene polymorphism on coronary artery disease (CAD) traits in 4631 Saudi angiographed individuals (2419 CAD versus 2212 controls) using TaqMan assay on ABI Prism 7900HT sequence detection system. Following adjustment for confounders, the rs2259820_CC (1.19 (1.01-1.42); P = 0.041), rs2464196_TT (1.19 (1.00-1.40); P = 0.045), and rs2259816_T (1.13 (1.01-1.26); P = 0.031) were associated with MI. The rs2259820_T (1.14 (1.03-1.26); P = 0.011) and rs2464196_C (1.12 (1.02-1.24); P = 0.024) were associated with type 2 diabetes mellitus (T2DM), while the rs2393791_T (1.14 (1.01-1.28); P = 0.032), rs7310409_G (1.16 (1.03-1.30); P = 0.013), and rs2464196_AG+GG (1.25 (1.05-1.49); P = 0.012) were implicated in hypertension. Hypertriglyceridemia was linked to the rs2393791_T (1.14 (1.02-1.27); P = 0.018), rs7310409_G (1.12 (1.01-1.25); P = 0.031), rs1169310_G (1.15 (1.04-1.28); P = 0.010), and rs1169313_CT+TT (1.24 (1.06-1.45); P = 0.008) and high low density lipoprotein-cholesterol levels were associated with rs2259820_T (1.23 (1.07-1.41); P = 0.004), rs2464196_T (1.22 (1.06-1.39); P = 0.004), and rs2259816_T (1.18 (1.02-1.36); P = 0.023). A 7-mer haplotype CATATAC (χ(2) = 7.50; P = 0.0062), constructed from the studied SNPs, was associated with MI, and CATATA implicated in T2DM (χ(2) = 3.94; P = 0.047). Hypertriglyceridemia was linked to TGCGGG (χ(2) = 4.26; P = 0.039), and obesity to ACGGGT (χ(2) = 5.04; P = 0.025). Our results suggest that the HNF1a is a common susceptibility gene for MI, T2DM, hypertension, and dyslipidemia.

A study of the role of GATA2 gene polymorphism in coronary artery disease risk traits.

The GATA2 is a multi-catalytic transcription factor believed to play an important role in regulating inflammatory processes, largely contributory to cardiovascular-related events. However, its role in coronary artery disease (CAD) risk traits remains poorly understood. In a preliminary study using Affymetrix 250K, we established a link on chromosome (chr) 3, which harbors the GATA2 gene, to early onset of CAD in two families with heterozygous familial hyperlipidemia (HFH), suggesting a role for the gene in metabolic-related CAD in the general population. We then sequenced the gene in the families and an additional 200 individuals in the general population, followed by an association study for 8 SNPs on CAD metabolic risk traits in a total of 4557 individuals (2386 CAD cases versus 2171 angiographed controls) by the Applied Biosystems real-time PCR system. The rs1573949_C [1.15(1.00-1.32); p=0.049] was associated with MI, rs7431368_AA [5.2(1.05-26.60); p=0.43] conferred risk for harboring low high density lipoprotein, and obesity was linked to rs10934857_AA [5.69(1.04-30.98); p=0.045] following Bonferroni corrections and multivariate adjustments for confounders. Furthermore, a haplotype CCCGGGTC (χ(2)=4.23; p=0.04) constructed from the eight studied SNPs and its 6-mer derivative CGGGTC (χ(2)=5.05; p=0.025) were associated with CAD. Obesity was associated with the 6-mer CATAAA (χ(2)=3.66; p=0.049), and hypercholesterolemia was linked to the 8-mer CCTGGACC (χ(2)=6.02; p=0.014), but most significantly so with its 5-mer derivative, CTGGA (χ(2)=6.75; p=0.009). On the other hand, high low density lipoprotein was linked to TGG (χ(2)=4.48; p=0.034). Our study points to an association of GATA2 at both SNP and haplotype levels with important metabolic risk traits for atherosclerosis.