MHC class II B diversity in blue tits: a preliminary study

Area of Science:

• Immunogenetics
• Avian Biology
• Molecular Ecology

Background:

• The Major Histocompatibility Complex (MHC) plays a crucial role in immune response and disease resistance.
• Understanding MHC diversity in wild bird populations is vital for conservation and disease management.
• The blue tit (Cyanistes caeruleus) serves as a model species for studying avian immune gene evolution.

Purpose of the Study:

• To partly characterize the MHC class II B genes in the blue tit.
• To investigate MHC allelic diversity across different European populations.
• To explore the evolutionary history and selection pressures on MHC genes in this species.

Main Methods:

• Screening of 22 blue tit individuals from Spain, The Netherlands, and Sweden.
• Utilizing PCR-based methods, Restriction Fragment Length Polymorphism (RFLP), and Southern blots.
• Sequencing of exon 2 from DNA and RNA to confirm gene transcription and functionality.

Main Results:

• Identification of 13 distinct exon 2 MHC class II B sequences.
• Detection of shared alleles across multiple European locations, with two alleles present in all sampled countries.
• Evidence of positive selection in the peptide binding region (PBR) of the MHC genes.
• Estimation of 2-4 MHC loci per individual based on sequencing and RFLP data.
• Phylogenetic analysis revealed a divergent MHC lineage in blue tits compared to other passerines.

Conclusions:

• The blue tit exhibits significant MHC class II B allelic diversity with evidence of balancing selection.
• Shared alleles across populations suggest gene flow and potential adaptation to common environmental factors.
• The unique MHC lineage highlights distinct evolutionary pathways within passerine birds.