MHC class I diversity in chimpanzees and bonobos

Area of Science:

• Evolutionary biology
• Immunogenetics
• Primate genetics

Background:

• Major histocompatibility complex (MHC) class I genes are crucial for identifying intracellular pathogens.
• Comparing MHC diversity in closely related species can reveal evolutionary selective processes.
• Bonobos and chimpanzees are humans' closest living relatives, sharing a common ancestor approximately one million years ago.

Purpose of the Study:

• To assess and compare the diversity of classical MHC class I genes (A, B, C, and A-like) in bonobos and central chimpanzees.
• To identify novel coding region sequences for these MHC genes in both species.
• To investigate potential differences in MHC class I diversity between bonobos and chimpanzees.

Main Methods:

• Utilized long-read sequencing technology (PacBio) to analyze MHC class I genes.
• Sequenced classical MHC class I genes (A, B, C, and A-like) in 20 bonobos and 30 central chimpanzees.
• Focused on wild-born individuals to represent natural populations.

Main Results:

• Described 21 novel coding region sequences in bonobos and 42 in central chimpanzees.
• Observed significantly reduced MHC class I diversity in bonobos compared to central chimpanzees.
• Found bonobo MHC class I diversity to be lower than that of western chimpanzees and humans.

Conclusions:

• Bonobos exhibit reduced MHC class I diversity relative to their closest relatives, chimpanzees.
• This reduction may indicate past evolutionary selective events specific to the bonobo lineage.
• Further research is needed to fully understand the implications of this reduced diversity for bonobo health and adaptation.