Article

European Journal of Human Genetics (2013) 21, 550–553; doi:10.1038/ejhg.2012.199; published online 5 September 2012

Stronger signal of recent selection for lactase persistence in Maasai than in Europeans

Carina M Schlebusch1,3, Per Sjödin1,3, Pontus Skoglund1,3 and Mattias Jakobsson1,2

  1. 1Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden
  2. 2Science for Life Laboratory, Uppsala University, Uppsala, Sweden

Correspondence: Dr CM Schlebusch, Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden. Tel: +46 76 306 3341; Fax: +46 18 471 6310; E-mail: cschlebu@gmail.com

3These authors contributed equally to this work.

Received 29 February 2012; Revised 26 July 2012; Accepted 10 August 2012
Advance online publication 5 September 2012

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Abstract

Continued ability to digest lactose after weaning provides a possible selective advantage to individuals who have access to milk as a food source. The lactase persistence (LP) phenotype exists at varying frequencies in different populations and SNPs that modulate the regulation of the LCT gene have been identified in many of these populations. Very strong positive selection for LP has been illustrated for a single SNP (rs4988235) in northwestern European populations, which has become a textbook example of the effect of recent selective sweeps on genetic variation and linkage disequilibrium. In this study, we employed two different methods to detect signatures of positive selection in an East African pastoralist population in the HapMap collection, the Maasai from Kenya, and compared results with other HapMap populations. We found that signatures of recent selection coinciding with the LCT gene are the strongest across the genome in the Maasai population. Furthermore, the genome-wide signal of recent positive selection on haplotypic variation and population differentiation around the LCT gene is greater in the Maasai than in the CEU population (northwestern European descent), possibly due to stronger selection pressure, but it could also be an indication of more recent selection in Maasai compared with the Central European group or more efficient selection in the Maasai due to less genetic drift for their larger effective population size. This signal of recent selection is driven by a putative East African LP haplotype that is different from the haplotype that contributes to the LP phenotype in northwestern Europe.

Keywords:

lactase persistence; selection; East Africa; Maasai; pastoralism