Major histocompatibility complex heterozygosity enhances reproductive success

Area of Science:

• Evolutionary genetics
• Immunogenetics

Background:

• The Major Histocompatibility Complex (MHC) plays a crucial role in immune response and mate selection.
• Understanding heterozygosity-fitness correlations is key to evolutionary biology.
• Previous studies often used inbred laboratory strains, limiting generalizability.

Purpose of the Study:

• To investigate the impact of MHC heterozygosity on fitness in outbred house mice.
• To differentiate MHC effects from genome-wide heterozygosity and inbreeding.
• To explore how background heterozygosity modulates MHC's fitness benefits.

Main Methods:

• Used systematically outbred F2 house mice (Mus musculus musculus).
• Assessed heterozygosity at MHC and 15 background microsatellite loci.
• Measured individual survival and reproductive success (RS) in semi-natural enclosures.

Main Results:

• Overall heterozygosity significantly increased RS, driven entirely by MHC heterozygosity.
• MHC heterozygosity enhanced RS without improving survival.
• MHC heterozygosity effects were contingent on background heterozygosity levels, showing a curvilinear relationship.

Conclusions:

• MHC heterozygosity enhances fitness in both wild and laboratory mice.
• Fitness benefits of heterozygosity can be attributed to specific loci like the MHC.
• MHC heterozygosity increases fitness via enhanced mating success and RS, not survival.
• The fitness advantage of MHC heterozygosity is context-dependent, influenced by background genetic diversity.