MHC allele frequency distributions under parasite-driven selection : a simulation model

doi:10.1186/1471-2148-10-332

MHC allele frequency distributions under parasite-driven selection : a simulation model

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MHC allele frequency distributions under parasite-driven selection : a simulation model

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Bibliographic description

punktacja MNiSW [2010 A]: 32

title:	MHC allele frequency distributions under parasite-driven selection : a simulation model
author:	Ejsmond Maciej , Babik Wiesław , Radwan Jacek
journal title:	BMC Evolutionary Biology
volume:	10
date of publication :	2010
article ID:	332
eISSN:	1471-2148
DOI:	10.1186/1471-2148-10-332
notes:	Bibliogr. s. 8-9
language:	English
journal language:	English
abstract in English:	Background. The extreme polymorphism that is observed in major histocompatibility complex (MHC) genes, which code for proteins involved in recognition of non-self oligopeptides, is thought to result from a pressure exerted by parasites because parasite antigens are more likely to be recognized by MHC heterozygotes (heterozygote advantage) and/or by rare MHC alleles (negative frequency-dependent selection). The Ewens-Watterson test (EW) is often used to detect selection acting on MHC genes over the recent history of a population. EW is based on the expectation that allele frequencies under balancing selection should be more even than under neutrality. We used computer simulations to investigate whether this expectation holds for selection exerted by parasites on host MHC genes under conditions of heterozygote advantage and negative frequency-dependent selection acting either simultaneously or separately. Results. In agreement with simple models of symmetrical overdominance, we found that heterozygote advantage acting alone in populations does, indeed, result in more even allele frequency distributions than expected under neutrality, and this is easily detectable by EW. However, under negative frequency-dependent selection, or under the joint action of negative frequency-dependent selection and heterozygote advantage, distributions of allele frequencies were less predictable: the majority of distributions were indistinguishable from neutral expectations, while the remaining runs resulted in either more even or more skewed distributions than under neutrality. Conclusions. Our results indicate that, as long as negative frequency-dependent selection is an important force maintaining MHC variation, the EW test has limited utility in detecting selection acting on these genes.
affiliation:	Wydział Biologii i Nauk o Ziemi : Instytut Nauk o Środowisku
type:	journal article
subtype:	academic paper