Evolution of MHC class I in the order Crocodylia

Area of Science:

• Evolutionary genetics
• Immunology
• Herpetology

Background:

• The major histocompatibility complex (MHC) is crucial for adaptive immunity in jawed vertebrates.
• MHC evolution is characterized by gene duplication and loss (birth-and-death process).
• MHC research in non-avian reptiles, like crocodiles, is limited.

Purpose of the Study:

• To investigate the evolutionary mechanisms shaping MHC class I diversity in the Order Crocodylia.
• To analyze MHC class I exon 3, intron 3, and exon 4 across Alligatoridae and Crocodilidae families.

Main Methods:

• Generated 124 DNA sequences from 20 crocodylian species.
• Identified 31 functional and 14 null MHC class I variants.
• Performed phylogenetic analyses to understand gene group distribution and evolution.

Main Results:

• Discovered three MHC class I gene groups, present in Crocodilidae but only one in Alligatoridae.
• Observed variant clustering at genus/family levels, not species-specific.
• Found variation in gene copy number and evidence of interlocus recombination.

Conclusions:

• MHC class I in Crocodylia has undergone independent gene duplication events, particularly within Crocodilidae.
• These findings provide insights into MHC class I evolution in reptiles.
• Establishes a framework for comparative MHC studies in non-avian reptiles and Crocodylia diversity assessment.