The Eurasian heartland: a continental perspective on Y-chromosome diversity

The nonrecombining portion of the human Y chromosome has proven to be a valuable tool for the study of population history. The maintenance of extended haplotypes characteristic of particular geographic regions, despite extensive admixture, allows complex demographic events to be deconstructed. In this study we report the frequencies of 23 Y-chromosome biallelic polymorphism haplotypes in 1,935 men from 49 Eurasian populations, with a particular focus on Central Asia. These haplotypes reveal traces of historical migrations, and provide an insight into the earliest patterns of settlement of anatomically modern humans on the Eurasian continent. Central Asia is revealed to be an important reservoir of genetic diversity, and the source of at least three major waves of migration leading into Europe, the Americas, and India. The genetic results are interpreted in the context of Eurasian linguistic patterns.

A major susceptibility locus for leprosy in India maps to chromosome 10p13

Leprosy, a chronic infectious disease caused by Mycobacterium leprae, is prevalent in India, where about half of the world's estimated 800,000 cases occur. A role for the genetics of the host in variable susceptibility to leprosy has been indicated by familial clustering, twin studies, complex segregation analyses and human leukocyte antigen (HLA) association studies. We report here a genetic linkage scan of the genomes of 224 families from South India, containing 245 independent affected sibpairs with leprosy, mainly of the paucibacillary type. In a two-stage genome screen using 396 microsatellite markers, we found significant linkage (maximum lod score (MLS) = 4.09, P < 2x10-5) on chromosome 10p13 for a series of neighboring microsatellite markers, providing evidence for a major locus for this prevalent infectious disease. Thus, despite the polygenic nature of infectious disease susceptibility, some major, non-HLA-linked loci exist that may be mapped through obtainable numbers of affected sibling pairs.

Thymus-dependent lymphoid regions in the spleen of the lizard, Calotes versicolor

This paper describes the distribution of thymus-derived lymphocytes in the spleen of the lizard, Calotes versicolor. Our studies reveal the existence of red and white pulp in the spleen. The red pulp consists of collagenous fibrous septae containing lymphocytes, erythrocytes and sinuses. The white pulp is an area enclosed by fibrous septae, containing lymphocytes, reticular cells and arterioles. The region around the arteriole in the white pulp was depleted of lymphocytes either one month after adult thymectomy or after anti-thymocyte serum treatment. The repopulation of this region was observed in sham-thymectomized controls, but not in thymectomized lizards. Therefore, this peri-arteriolar region may be designated as a thymus-dependent area, as described previously in higher vertebrates. The significance of these findings is discussed in relation to the phylogeny of the immune system.