pubmed.ncbi.nlm.nih.gov

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

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

Carina M Schlebusch et al. Eur J Hum Genet. 2013 May.

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.

PubMed Disclaimer

Figures

Figure 1
Figure 1

Selection scans. (a) winiHS across the genome (see text) of the MKK population. Light blue corresponds to odd-numbered chromosomes while even-numbered chromosomes are colored dark blue. The LCT/MCM6 region on chromosome 2 and the MHC regions on chromosome 6 are marked by horizontal lines. (b) Close-up of winiHS in the lactase region (position 125 Mb to 145 Mb on chromosome 2). The numbers correspond to the rank across the entire genome of each population of the winiHS for the SNPs (the top 20 SNPs are shown). The gray vertical line marks the region of LCT/MCM6. (c) Close-up of the winPBS in the lactase region (position 125 Mb to 145 Mb on chromosome 2). The numbers correspond to the rank across the entire genome (the top 10 SNPs are shown).

Figure 2
Figure 2

Haplotype network and frequency table for 60-SNP haplotypes encompassing the LCT and MCM6 loci. The network shows the relationship of the 60-SNP haplotypes in five selected HapMap3 populations. The CEU LP haplotype is indicated in the figure, as defined by the 13910C-T mutation (rs4988235). The inset-table shows the frequencies of the CEU LP haplotype, the MKK LP haplotype and other haplotypes in five different HapMap populations. The average PBS for the 60 SNPs had a greater value for MKK (0.57) than for CEU (0.43), where the genome average PBS values were 0.071 for MKK and 0.036 for CEU.

Similar articles

Cited by

References

    1. Ingram CJ, Mulcare CA, Itan Y, Thomas MG, Swallow DM. Lactose digestion and the evolutionary genetics of lactase persistence. Hum Genet. 2009;124:579–591. - PubMed
    1. Ingram CJ, Raga TO, Tarekegn A, et al. Multiple rare variants as a cause of a common phenotype: several different lactase persistence associated alleles in a single ethnic group. J Mol Evol. 2009;69:579–588. - PubMed
    1. Swallow DM. Genetics of lactase persistence and lactose intolerance. Annu Rev Genet. 2003;37:197–219. - PubMed
    1. Enattah NS, Jensen TG, Nielsen M, et al. Independent introduction of two lactase-persistence alleles into human populations reflects different history of adaptation to milk culture. Am J Hum Genet. 2008;82:57–72. - PMC - PubMed
    1. Enattah NS, Sahi T, Savilahti E, Terwilliger JD, Peltonen L, Jarvela I. Identification of a variant associated with adult-type hypolactasia. Nat Genet. 2002;30:233–237. - PubMed

Publication types

MeSH terms

Substances