Active MHC class Ib genes in rat are pseudogenes in the mouse

Area of Science:

• Immunogenetics
• Comparative genomics
• Mammalian evolution

Background:

• The M region of the Major Histocompatibility Complex (MHC) in rodents contains class I genes.
• Genes M4 and M6 are orthologous between rats and mice.
• M4 and M6 are pseudogenes in mice but functional genes in rats.

Purpose of the Study:

• To investigate the pseudogene status of mouse M4 and M6 genes in detail.
• To compare the genetic integrity of these genes across different mouse strains.
• To understand the evolutionary divergence of MHC class I genes between rats and mice.

Main Methods:

• Sequencing of M4 and M6 exons from representative mouse haplotypes.
• Analysis of sequence variations, including stop codons, insertions, and deletions.
• Comparative sequence analysis between mouse and rat orthologs.

Main Results:

• Conserved stop codons were identified in the M4 and M6 genes across all analyzed mouse strains.
• Additional insertions and deletions, further compromising functionality, were observed in mouse M4 and M6.
• These findings confirm the pseudogene status of M4 and M6 in mice, contrasting with their intact state in rats.

Conclusions:

• Mouse M4 and M6 genes exhibit a 'split status,' being non-functional pseudogenes in mice but functional genes in rats.
• Sequence analysis supports the evolutionary divergence and loss of function for these specific MHC class I genes in the mouse lineage.
• The study underscores the dynamic nature of MHC gene evolution and the importance of comparative genomics in understanding gene function and pseudogenization.