H. Al-Saud1 ; SM. Wakil1 ; BF. Meyer1 ; M. Falchi2 ; N. Dzimiri1
1) Genetics Department, King Faisal Hospital and Research Centre, Riyadh, Saudi Arabia; 2) Department of Twin Research and Genetic Epidemiology, King’s College London, London, United Kingdom.
Saudi Arabia is the largest Gulf Cooperation Council (GCC) country. Its population consists of different tribes that originated in the northern, western, eastern, middle and south regions of Saudi Arabia, respectively. Due to political and cultural reasons, there has historically been very limited admixture between different tribes. People from the different Saudi tribes then migrated from Saudi Arabia, contributing to foundation of the populations now inhabiting other Gulf countries. Few population genetics research projects have been conducted on this highly consanguineous population that has been shown to have one of the highest prevalence in the world of recessive disorders and common metabolic diseases, especially diabetes. It is therefore important to identify the genetic substructures of the Saudi population, both to help in tracing the migratory genetic flows that contributed to other Gulf populations, and to permit designing of efficient genetic studies aimed at the identification of risk factors underlying common and rare diseases in the GCC countries. We carried out the largest population genetic study in Saudi Arabia to date, by genotyping 2,150 Saudi nationals sampled from different regions of Saudi Arabia using Axiom GWH-96 Array (Affymetrix) arrays. Model-based and model-free clustering were applied to these data, including in our analyses data on eight populations (encompassing Europe, America, Oceana, East Asia, Central South Asia, Middle East, Africa and Qatari populations) from the Human Genetic Diversity Project (HGDP) data set. We identified clear clustering of the Saudi samples into different subgroups, with some tribes showing similarity with both Central East Asian (Kalash Pakistan, Balochi Pakistan, Sindhi Pakistan, Makrani Pakistan and Brahui Pakistan subpopulations) European (Orkney Islands Europe, Russian Europe and Russian Caucasus subpopulations) and Qatari populations, while other tribes appear to show specificity of background.These data strongly support the presence of genetic stratification within the Saudi population, and suggest the presence of subgroups that are characterized by a unique genetic background different from other Arabian populations. Our findings constitute a valuable resource for the investigation of both general and population-specific genetic risk variants associated with different disorders in this population.