Complement component 3 haplotypes influence serum complement activity and milk production traits in Chinese Holstein...

Area of Science:

• Animal Genetics
• Immunology
• Biochemistry

Background:

• Complement component 3 (C3) is central to innate immunity, mediating pathogen destruction via alternative, classical, and lectin complement pathways.
• C3 plays critical roles in phagocytosis, inflammation, and immunoregulation, essential for defending against infectious agents.

Purpose of the Study:

• To investigate novel single-nucleotide polymorphisms (SNPs) in the cattle C3 gene.
• To analyze the association of C3 gene polymorphisms with serum C3 levels, complement hemolytic activity, and milk production traits.
• To evaluate the impact of C3 gene variations on resistance to bacterial infections, particularly in mastitis.

Main Methods:

• Genotyping of three novel C3 gene SNPs (g.-1293C>G, g.56T>C, and g.7017C>T) in 952 cattle using PCR-RFLP and DNA sequencing.
• Analysis of genotype and haplotype associations with serum C3 concentration, CH50, ACH50, somatic cell score (SCS), and 305-day milk yield.
• In vitro antibacterial activity assays against Staphylococcus aureus and Escherichia coli using serum from cattle with different C3 genotypes.

Main Results:

• The g.56T>C SNP in exon I and the g.7017C>T SNP in exon XII significantly affected serum ACH50.
• Specific genotypes (e.g., CCC/GCC) were associated with lower SCS and reduced serum C3 concentration, while others (e.g., CCC/CCT) showed higher ACH50.
• Genetically resistant cattle (CCC/GCC) exhibited significantly higher serum antibacterial activity against S. aureus and E. coli compared to susceptible cattle (CCC/GTT).

Conclusions:

• The C3 gene polymorphisms are associated with variations in complement activity and milk production traits in cattle.
• The identified C3 gene SNPs can serve as molecular markers for enhancing complement activity and milk production.
• The C3 gene plays a significant role in cattle's resistance to bacterial infections, offering potential for marker-assisted selection in breeding programs.