Directional and balancing selection in human beta-defensins.

Area of Science:

• Evolutionary biology
• Genomics
• Immunology

Background:

• Infectious diseases significantly drive gene evolution in primates, impacting human health.
• Beta-defensins are crucial innate immune molecules with antimicrobial, signaling, and reproductive roles.
• This study investigates beta-defensin evolution in catarrhine primates and human population variations.

Purpose of the Study:

• To analyze the evolutionary trajectory of beta-defensin genes in catarrhine primates.
• To identify instances of positive selection and their specific locations within these genes.
• To explore beta-defensin variation across diverse human populations.

Main Methods:

• Comparative genomic analysis of beta-defensin genes across catarrhine primates.
• Identification of codons under positive selective pressure.
• Haplotyping of specific genes (e.g., DEFB127) in human populations.
• Analysis of genetic diversity in beta-defensin genes (e.g., DEFB132) in hunter-gatherer versus agricultural populations.

Main Results:

• Five beta-defensin genes exhibit positive selection in catarrhine primates, with identified codons under selective pressure.
• DEFB127 shows long-term balancing selection in humans, with two distinct haplotype clades.
• DEFB132 displays significant diversity in African and non-African hunter-gatherer populations, absent in agricultural groups.

Conclusions:

• Not all beta-defensin genes are under positive selection in catarrhine primates.
• Evidence suggests varying selective pressures on beta-defensins within human populations.
• The precise nature of these selective pressures requires further investigation.