View Full Version : European Palaeolithic expansion shown by resequencing of non-recombining X-chromosome

27-01-17, 19:26

Signatures of human European Palaeolithic expansion

shown by resequencing of non-recombining
X-chromosome segments

Human genetic diversity in Europe has been extensively studied using uniparentally inherited sequences (mitochondrial DNA
(mtDNA) and the Y chromosome), which reveal very different patterns indicating sex-speci
c demographic histories. The
X chromosome, haploid in males and inherited twice as often from mothers as from fathers, could provide insights into past
female behaviours, but has not been extensively investigated. Here, we use HapMap single-nucleotide polymorphism data to
identify genome-wide segments of the X chromosome in which recombination is historically absent and mutations are likely to be
the only source of genetic variation, referring to these as phylogeographically informative haplotypes on autosomes and
X chromosome (PHAXs). Three such sequences on the X chromosome spanning a total of ~49 kb were resequenced in 240
males from Europe, the Middle East and Africa at an average coverage of 181 ×. These PHAXs were con
rmed to be essentially

recombining across European samples. All three loci show highly homogeneous patterns across Europe and are highly
differentiated from the African sample. Star-like structures of European-speci
c haplotypes in median-joining networks indicate
past population expansions. Bayesian skyline plots and time-to-most-recent-common-ancestor estimates suggest expansions pre-
dating the Neolithic transition, a
nding that is more compatible with data on mtDNA than the Y chromosome, and with the
female bias of X-chromosomal inheritance. This study demonstrates the potential of the use of X-chromosomal haplotype blocks,
and the utility of the accurate ascertainment of rare variants for inferring human demographic history.