December 02, 2007

ASHG 2007 abstracts

You can get the 656-page volume of abstracts (pdf) of this year's American Society of Human Genetics meeting. Some titles/abstracts that caught my eye.

A. Rosa et al.

Mitochondrial haplogroup H1 is protective for stroke.

S. Sharma et al.

The Autochthonous Origin and a Tribal Link of Indian Brahmins: Evaluation Through Molecular Genetic Markers

The co-existence and associated genetic evidences for the major rival models: i) recent Central Asian introduction of Indian caste system, ii) rank related west Eurasian admixture, iii) South Asian origin for Indian caste communities, and iv) late Pleistocene heritage of tribal and caste populations, leave the question of the origin of caste system in India hazy and obscure. To resolve the issue, we screened 621 Y-chromosomes (of Brahmins, occupying upper most caste position and Dalits and Tribals with the lower most positions in the Indian caste hierarchical system) with fifty-five Y-chromosomal binary markers and Y-microsatellite markers and compiled a data set of 2809 Y-chromosomes (681 Brahmins, 2128 Tribals and Dalits) for conclusions. Overall, no consistent difference was observed in Y-haplogroups distribution between Brahmins, Dalits and Tribals, except for some differences confined to a given geographical region. A peculiar observation of highest frequency (upto 72.22%) of Y-haplogroups R1a1* in Brahmins, hinted at its presence as a founder lineage for this caste group. The widespread distribution and high frequency across Eurasia and Central Asia of R1a1* as well as scanty representation of its ancestral (R*, R1* and R1a*) and derived lineages across the region has kept the origin of this haplogroup unresolved. The analyses of a pooled dataset of 530 Indians, 224 Pakistanis and 276 Central Asians and Eurasians, bearing R1a1* haplogroup resolved the controversy of origin of R1a1*. The conclusion was drawn on the basis of: i) presence of this haplogroup in many of the tribal populations such as, Saharia (present study) and Chenchu tribe in high frequency, ii) the highest ever reported presence of R1a* (ancestral haplogroup of R1a1*) in Kashmiri Pandits (Brahmins) and Saharia tribe, and iii) associated averaged phylogenetic ages of R1a* (~18,478 years) and R1a1* (~13,768 years) in India. The study supported the autochthonous origin of R1a1 lineage and a tribal link to Indian Brahmins.

Population structure in Sweden - A Y-chromosomal and mitochondrial DNA analysis.

T. Lappalainen et al.

A population sample representing the current Swedish population was analyzed for both maternally and paternally inherited markers with the aim of characterizing the genetic variation and structure of a modern North European population. We genotyped 12 Y-chromosomal and 27 mitochondrial DNA SNPs from DNA extracted and amplified from Guthrie cards of all the children born in Sweden during one week in 2003. The sample set consisted of 1914 samples (960 males) grouped according to place of birth. The ancient migration patterns are reflected in the clear north-south gradients in several palaeolithic and neolithic haplogroups in the mtDNA (U5, I, K, T, X) and the Y chromosome (R1b, N3). The haplogroup frequencies of the counties closest to Finland and Norway showed clear associations to the neighboring populations, resulting from the formation of the nations during the past millennium. Moreover, the recent immigration waves of the 20th century are visible both maternally and paternally, and have led to increased diversity and divergence from the main population in the major cities. Unfavorable population development in the ancient or recent past can be detected in several remote counties with low diversities and other signs of low population size and/or population crises. In conclusion, our study yielded valuable information about the various factors affecting the structure of the modern Swedish population that is vital for the use of the population in large population-based studies. Our sampling strategy, nonselective on the current population rather than stratified according to ancestry, represents the future of genetic studies in the increasingly panmictic populations of the world.

Relic Distribution of Y-Chromosome Haplogroup D Suggests Ancient Paleolithic Migration of Modern Humans in Eastern Asia.

H. Shi et al.

The Y chromosome haplogroup D is East Asian specific and prevalent in Tibetan and Japanese populations (30%-40%), but rare in other East Asian populations (<5%). We analyzed 5,174 Y chromosomes from 74 East Asian populations by typing haplogroup D related SNPs and eight Y chromosome microsatellite loci. We identified six sublineages under haplogroup D, and their distribution across East Asia suggested an ancient Paleolithic south-to-north migration, which likely predates the previously proposed northward diaspora of modern humans (reflected by the dominant occurrence of O3-M122 in East Asians) resulting in current relic distribution of haplogroup D in East Asia.

E. Marchani et al. Culture creates genetic structure in Daghestan.

M. Coelho et al. On the edge of the Bantu expansions: patterns of mtDNA and Y-chromosome variation in southwestern Angola.

J.S. Friedlaender et al. The genetic structure of Pacific Islanders.

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