Gayden Tenzin, Cadenas Alicia M, Regueiro Maria, Singh Nanda B, Zhivotovsky Lev A, Underhill Peter A, Cavalli-Sforza Luigi L, Herrera Rene J
Department of Biological Sciences, Florida International University, Miami, FL 33199, USA.
Am J Hum Genet. 2007 May;80(5):884-94. doi: 10.1086/516757. Epub 2007 Apr 4.
High-resolution Y-chromosome haplogroup analyses coupled with Y-short tandem repeat (STR) haplotypes were used to (1) investigate the genetic affinities of three populations from Nepal--including Newar, Tamang, and people from cosmopolitan Kathmandu (referred to as "Kathmandu" subsequently)--as well as a collection from Tibet and (2) evaluate whether the Himalayan mountain range represents a geographic barrier for gene flow between the Tibetan plateau and the South Asian subcontinent. The results suggest that the Tibetans and Nepalese are in part descendants of Tibeto-Burman-speaking groups originating from Northeast Asia. All four populations are represented predominantly by haplogroup O3a5-M134-derived chromosomes, whose Y-STR-based age (+/-SE) was estimated at 8.1+/-2.9 thousand years ago (KYA), more recent than its Southeast Asian counterpart. The most pronounced difference between the two regions is reflected in the opposing high-frequency distributions of haplogroups D in Tibet and R in Nepal. With the exception of Tamang, both Newar and Kathmandu exhibit considerable similarities to the Indian Y-haplogroup distribution, particularly in their haplogroup R and H composition. These results indicate gene flow from the Indian subcontinent and, in the case of haplogroup R, from Eurasia as well, a conclusion that is also supported by the admixture analysis. In contrast, whereas haplogroup D is completely absent in Nepal, it accounts for 50.6% of the Tibetan Y-chromosome gene pool. Coalescent analyses suggest that the expansion of haplogroup D derivatives--namely, D1-M15 and D3-P47 in Tibet--involved two different demographic events (5.1+/-1.8 and 11.3+/-3.7 KYA, respectively) that are more recent than those of D2-M55 representatives common in Japan. Low frequencies, relative to Nepal, of haplogroup J and R lineages in Tibet are also consistent with restricted gene flow from the subcontinent. Yet the presence of haplogroup O3a5-M134 representatives in Nepal indicates that the Himalayas have been permeable to dispersals from the east. These genetic patterns suggest that this cordillera has been a biased bidirectional barrier.
高分辨率Y染色体单倍群分析结合Y短串联重复序列（STR）单倍型，用于（1）研究来自尼泊尔的三个人口群体——包括尼瓦尔人、塔芒人以及来自国际化都市加德满都的人群（以下简称“加德满都人”）——以及一组来自西藏的人群的遗传亲缘关系，以及（2）评估喜马拉雅山脉是否是青藏高原和南亚次大陆之间基因流动的地理障碍。结果表明，藏族和尼泊尔人部分是源自东北亚说藏缅语族群体的后裔。所有四个人口群体主要由单倍群O3a5-M134衍生的染色体代表，基于Y-STR的年龄（±标准误）估计为8100±2900年前（KYA），比其东南亚对应群体更近。两个地区最明显的差异体现在西藏单倍群D和尼泊尔单倍群R的相反高频分布上。除了塔芒人，尼瓦尔人和加德满都人都与印度Y单倍群分布有相当大的相似性，特别是在它们的单倍群R和H组成方面。这些结果表明基因从印度次大陆流入，就单倍群R而言，也从欧亚大陆流入，这一结论也得到了混合分析的支持。相比之下，虽然单倍群D在尼泊尔完全不存在，但它占藏族Y染色体基因库的50.6%。溯祖分析表明，西藏单倍群D衍生物——即D1-M15和D3-P47——的扩张涉及两个不同的人口事件（分别为5100±1800和11300±3700 KYA），比日本常见的D2-M55代表更近。相对于尼泊尔，西藏单倍群J和R谱系的低频也与来自次大陆的有限基因流动一致。然而，尼泊尔存在单倍群O3a5-M134代表表明，喜马拉雅山脉对来自东部的扩散是可渗透的。这些遗传模式表明，这条山脉一直是一个有偏向的双向障碍。
