Intronic variants in the long non-coding RNA CDKN2B-AS1 are strongly associated with the risk of coronary artery disease in the Northern Tribes of Tanzania

Introduction: Sub-Saharan Africa (SSA) is facing a rising epidemic of non-communicable diseases including the coronary artery disease (CAD) ranking at the top of the list. Chromosome locus 9p21.3 containing CDKN2B antisense RNA 1 (CDKN2B-AS1), identified in many genome-wide association studies for coronary artery disease (CAD), encompasses multiple single nucleotide polymorphisms (SNPs). This study aimed to conduct the first genetic study evaluating the common polymorphisms in 9p21.3 locus in Tanzanian CAD patients from different regions of Tanzania and their associations with CAD risk factors. Material and Methods: A total of 90 patients from Northern region (N-CAD) of Tanzania and 65 patients from other regions (South, East, West and Central) (R-CAD) were included in the study. Further the biochemical analysis the genotyping of common variants was performed with the LightSNiP typing assay using qRT-PCR method.  Results: Our analyses revealed that both genotype and allele frequencies of rs10757274, rs10757278 and rs10811656 were significantly different between the groups (p<0.05, respectively). We identified that one previously undescribed three-marker haplotype (rs1333049, rs10757274 and rs10757278) encompassing CDKN2B-AS1 was overrepresented (G-G-G, the risk haplotype, p<0.05) in N-CAD group compared to R-CAD group. The AUC of a risk model based on non-genetic factors was 0.730 (0.654-0.797) and the combination with genetic risk factors improved the AUC to 0.784 (95%CI=0.713-0.844, p<0.0001). Conclusion: Our results identified the presence of a novel three-marker haplotype having a significant association with CAD in Northern Tanzania. Moreover, combination of the nongenetic and genetic risk models were demonstrated to indicate good diagnostic accuracy for CAD in Northern Tanzania.