Y Chromosome Variation In Cham Population And Lactose Tolerance Variantion In Tibetans

Numerous researches have demonstrated that the culture has played an important role in human evolution, and left several footprints in human genome. In the present study, we performed investigations concerning the effects of language (Austronesian) and diet (milk consumption) on human population genetic variation. The origin and expansion of the Austronesians in Southeast Asia remains debatable. Our first work focused on the Austronesian diffusion in Mainland Southeast Asia (MSEA) from patrilineal perspective. As the arising of Neolithic Revolution, diets of human have been changed a lot. To digest the lactose in milk, Lactase persistence (LP) should be required. Our second work is about the lactose tolerance (LT) variants in Tibetan population from Tibet.Comparing with the extensive distribution in Island Southeast Asia (ISEA), the Austronesian languages in this family have a rather limited distribution on the mainland. The Cham people are the major Austronesian speakers of MSEA and the reconstruction of the Cham population history can provide insights into their diffusion. In this study, we analyzed non-recombining region of the Y chromosome (NRY) markers, including26single-nucleotide polymorphisms (Y-SNPs) and eight short tandem repeats (Y-STRs), in177unrelated males from four populations in MSEA (59Cham,76Kinh,25Lao, and17Thai). Incorporating published data from mitochondrial DNA (mtDNA), our results indicate that, in general, the Chams are an indigenous Southeast Asian population. The origin of the Cham people involves the genetic admixture of the Austronesian immigrants from ISEA with the local populations in MSEA. Discordance between the overall patterns of Y chromosome and mtDNA in the Chams is evidenced by the presence of some Y chromosome lineages that prevail in South Asians (R-M17, R-M124). Our results suggest that male-mediated dispersals via the spread of religions and business trade might play an important role in shaping the patrilineal gene pool of the Cham people.Milk consumption is prevalent in daily diets for Tibetans. Although there is evidence that LP prevalence in Tibetans was higher than in Han Chinese, little is known about the genetic basis of LT in Tibetans. We screened in495Tibetan individuals for the previously reported five SNPs (-13907C/G,-13910C/T,-13915T/G,-14010G/C, and-22018G/A) that are associated with the LT in populations surrounding Tibet. For the four candidate SNPs-13907C/G,-13910C/T,-13915T/G, and-14010G/C, the alleles responsible for LT are completely absent in Tibetan samples. For-22018G/A, only one heterozygous form is present in the population from Nagqu. The results indicate that the LT in Tibetans may not be explained by these known SNPs, suggesting an independent origin of LT in Tibetans. Three novel SNPs (-13838G/A:6.6%,-13906T/A:0.6%, and-13908C/T:0.1%) are identified in current study. Taking the evidences from previous researches together, we suggest that the SNP-13838G/A may be responsible for LT in Tibetans. However, further comprehensive genotype-phenotype association analyses and functional experiments are required in the future.