Nucleotide sequence, polymorphism, and evolution of ovine MHC class II DQA genes

Area of Science:

• Immunogenetics
• Comparative genomics
• Molecular evolution

Background:

• The ovine major histocompatibility complex (MhcOvar) plays a crucial role in immune responses.
• Understanding the structure and function of ovine DQA genes is essential for comparative immunology.
• Previous studies have characterized DQA genes in various mammalian species.

Purpose of the Study:

• To determine the nucleotide sequence and gene structure of ovine DQA genes (MhcOvar) analogous to human HLA-DQA1 and HLA-DQA2.
• To compare predicted amino acid sequences and elucidate evolutionary relationships with DQA genes from other species.
• To investigate the transcriptional activity and allelic polymorphism of ovine DQA genes.

Main Methods:

• Nucleotide sequencing of ovine DQA gene exons and introns.
• Amino acid sequence prediction and comparison with orthologous genes in humans, mice, rats, rabbits, and cattle.
• Northern blot analysis to assess mRNA expression.
• Restriction fragment length polymorphism (RFLP) analysis for allelic diversity and gene copy number variation.

Main Results:

• The gene structure of ovine DQA genes is similar to that reported in other species.
• Both ovine Ovar-DQA genes are transcriptionally active, unlike human HLA-DQA2.
• RFLP analysis revealed polymorphic alleles and variable DQA gene copy numbers in sheep, contrasting with the constant number in humans.

Conclusions:

• Ovine DQA genes exhibit conserved structural features and evolutionary relationships with other mammalian DQA genes.
• Differential transcriptional activity of Ovar-DQA genes compared to human HLA-DQA2 suggests species-specific regulation.
• The variable number of DQA genes in sheep highlights a unique genetic characteristic within the ovine MHC.