Genetic structure and contrasting selection pattern at two major histocompatibility complex genes in wild house mouse...

Area of Science:

• Evolutionary genetics
• Immunogenetics
• Population genetics

Background:

• The mammalian major histocompatibility complex (MHC) is a critical immune gene cluster often inherited as a unit.
• This has led to the assumption that studying a single MHC gene can represent the evolutionary patterns of the entire complex.
• However, the evolutionary dynamics of individual MHC genes may vary.

Purpose of the Study:

• To compare evolutionary signals and diversification patterns between two closely linked MHC class II genes (H-2Aa and H-2Eb).
• To investigate MHC variation across a 1000-km transect of the European house mouse hybrid zone.
• To determine if studying a single MHC gene provides representative evolutionary insights.

Main Methods:

• Analysis of MHC variation across a European house mouse hybrid zone.
• Comparison of evolutionary patterns and selection signals at H-2Aa and H-2Eb genes.
• Assessment of allelic polymorphism, mutation rates, selection, and population structuring.

Main Results:

• Despite close linkage (0.01 cM), H-2Aa and H-2Eb exhibit disparate evolutionary patterns.
• H-2Aa shows higher polymorphism, faster turnover, stronger positive selection, and greater population structuring.
• H-2Eb alleles have longer persistence, mixed selection pressures (positive and negative), and instances of non-expression.

Conclusions:

• Evolutionary studies of MHC genes in wild vertebrates yield substantially different results depending on the specific gene examined.
• The level of polymorphism in a related species is an unreliable criterion for selecting an MHC gene for study.
• Close linkage does not guarantee similar evolutionary trajectories for MHC genes.