Yang Xiong, Al-Bustan Suzanne, Feng Qidi, Guo Wei, Ma Zhiming, Marafie Makia, Jacob Sindhu, Al-Mulla Fahd, Xu Shuhua
Chinese Academy of Sciences (CAS) Key Laboratory of Computational Biology, Max-Planck Independent Research Group on Population Genomics, CAS-MPG Partner Institute for Computational Biology (PICB), Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
Department of Biological Sciences, Kuwait University, Safat, Kuwait.
J Hum Genet. 2014 Nov;59(11):615-22. doi: 10.1038/jhg.2014.81. Epub 2014 Sep 25.
The Middle East (ME) is an important crossroad where modern humans migrated 'out of Africa' and spread into Europe and Asia. After the initial peopling and long-term isolation leading to well-differentiated populations, the ME also had a crucial role in subsequent human migrations among Africa, Europe and Asia; thus, recent population admixture has been common in the ME. On the other hand, consanguinity, a well-known practice in the ME, often reduces genetic diversity and works in opposition to admixture. Here, we explored the degree to which admixture and consanguinity jointly affected genetic diversity in ME populations. Genome-wide single-nucleotide polymorphism data were generated in two representative ME populations (Arabian and Iranian), with comparisons made with populations worldwide. Our results revealed an overall higher genetic diversity in both ME populations relative to other non-African populations. We identified a much larger number of long runs of homozygosity in ME populations than in any other populations, which was most likely attributed to high levels of consanguineous marriages that significantly decreased both individual and population heterozygosity. Additionally, we were able to distinguish African, European and Asian ancestries in ME populations and quantify the impact of admixture and consanguinity with statistical approaches. Interestingly, genomic regions with significantly excessive ancestry from individual source populations are functionally enriched in olfactory pathways, which were suspected to be under natural selection. Our findings suggest that genetic admixture, consanguinity and natural selection have collectively shaped the genetic diversity of ME populations, which has important implications in both evolutionary studies and medical practices.
中东地区是现代人类“走出非洲”并扩散至欧洲和亚洲的重要十字路口。在最初的人类定居以及长期隔离导致形成差异显著的人群之后，中东地区在随后非洲、欧洲和亚洲之间的人类迁徙中也发挥了关键作用；因此，近期的人群混合在中东地区很常见。另一方面，近亲结婚作为中东地区一种广为人知的习俗，往往会降低遗传多样性，与人群混合的作用相反。在此，我们探究了混合与近亲结婚共同影响中东地区人群遗传多样性的程度。我们在两个具有代表性的中东人群（阿拉伯人和伊朗人）中生成了全基因组单核苷酸多态性数据，并与全球其他人群进行了比较。我们的结果显示，相对于其他非非洲人群，这两个中东人群的遗传多样性总体上更高。我们发现中东人群中纯合子长片段的数量比其他任何人群都多得多，这很可能归因于近亲结婚的高比例，近亲结婚显著降低了个体和群体的杂合度。此外，我们能够区分中东人群中的非洲、欧洲和亚洲血统，并通过统计方法量化混合与近亲结婚的影响。有趣的是，来自单个源人群的血统显著过多的基因组区域在嗅觉通路中功能富集，这些通路被怀疑受到自然选择。我们的研究结果表明，遗传混合、近亲结婚和自然选择共同塑造了中东人群的遗传多样性，这在进化研究和医学实践中都具有重要意义。
