Three Novel Snps Of C3 Gene In Chinese Holstein Cattle And Its Associations With Production Traits

Infectious disease has major adverse effects both on the economics of livestock production and on animal welfare. The costs of disease are estimated as 17% of turnover in the developed world (￡1.7 billion in the UK each year) and 35-50% in the developing world. Cow mastitis is a common disease in dairy industry worldwide, and has caused tremendous loss to the dairy production. A number of therapeutic, prophylactic and management strategies have been proposed to minimize this complex disease. Although these treatments have very good clinical outcome, emerge of drug-resistant strains and remaining antibiotics in milk have brought great concerns. Thus, an approach based on improving the host genetics in resistance to infectious diseases through molecular marker selective breeding is becoming widely accepted.Complement is an ancient defense mechanism that evolved into a large protein-interaction network in mammals that initiates and serves innate immune functions and links innate immunity with adaptive immunity. The complement component C3 is the key molecule of the three pathways of complement activation (alternative, classical and lectin pathways), which are involved in phagocytosis, inflammation and immunoregulation processes to destroy infectious microorganism. It's not only can participate in the complement cascade reaction by it's activation,but also interact with all kinds of correlation factor.It's deficiency in hosts causes increasing susceptibility to bacterial or viral infections.Chinese Holstein Cattle is derived from grading cross breeding and selection between the Chinese native cow and pure-bred bull of Holstein introduced to China. The frequency of mastitis in the breed is about 38%～50%. The Luxi yellow cattle and Bohai black cattle are two of the representative indigenous bovine (Bos taurus) breeds in China, which have been bred as beef and draft dual-purpose cattle for thousands of years because of the lower disease and enduring unfavourable feeding condition.In the present study we detected 3 single-nucleotide polymorphisms of C3 gene in Chinese native cattle and analyzed Chinese Holstein cattle's associations with milk traits. By screening the genetic variation of C3 in 952 individuals of three Chinese native cattle breeds including Chinese Holstein, Luxi Yellow and Bohai Black using Created Restriction Site-Polymerase chain reaction (CRS-PCR), PCR-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing techniques, three new SNPs (g.-1293C>G, g.56T>C, g.7017C>T) with allele frequencies ranging from 11.79% to 24%, 14.15% to 29.38% and 17.11% to 20%, respectively, were found. One SNP (g. -1293C>G) of C3 gene was located in 5'- flanking regions and the other two SNPs (g.56T>C, g.7017C>T) in exon I and exon XII, which respectively showed one non-synonymous mutation ATG (Met)>ACG (Thr) and one synonymous mutation CAC (His) >CAT (His). The SNPs were submitted to the National Centre for Biotechnology Information (submitter SNP numbers: ss289377982, ss289377985, ss289377986) In Chinese Holstein cattle and Luxi Yellow cattle and Bohai Black cattle, predominant allele were identical at g.-1293C>G, g.56T>C and g.7017C>T, which were C, T, C, and the allelic frequencies were 83.5%/88.21%/76%, 70.62%/85.85%/82%, 82.89%/80.19%/80%, respectively. Chi-square test indicated that except for the g.-1293C>G of Luxi Yellow cattle, the other sites of all three cattles were in accordance with the Hardy-Weinberg equilibrium (P>0.05). The value of polymorphism information content indicated that g.-1293C>G of Chinese Holstein and Luxi Yellow cattle, g.56T>C of Luxi Yellow cattle, g.7017C>T of Chinese Holstein cattle were slight polymorphism; the others were moderate polymorphism in the three breeds (0.25G and somatic cell score (SCS), however exists significant associations between it and protein rate (P<0.05). The individuals with haplotype combination H1H1(CCC/CCC) showed higher protein content and fat content (P < 0.05) than the ones with haplotype combinations of H1H8(CCC/GTT) (P < 0.05),combined with the results of that individuals with haplotype combination H1H5(CCC/GCC) showed significantly lower SCS scores and the lowest C3 concentration in serum in comparison to the haplotype combinations of H1H8 (CCC/GTT) (P<0.01) and H4H4(CTT/CTT) (P<0.01),we can conclude the H1H8 (CCC/GTT)should be abandoned, the cattle with combination H1H1 (CCC/CCC)and H1H5 (CCC/GCC)can be selected to breeding record its lower SCS.In 354 Chinese Holstein cattle, eight different haplotypes and eighteen combinations were detected. Between g.56T>C and ACH50 (P<0.01) exists significant associations. There are significant associations between g.7017C>T and ACH50 (P<0.01). All these data indicates that SNP g.56T>C and g.7017C>T might play roles in the host response against mastitis. The cows with H2H4 (CCT/CTT) have the higher value of CH50 than the other cows (P>0.05). The individuals with haplotype combination H1H2 (CCC/CCT)had significantly higher ACH50 than the ones with haplotype combinations of H1H3(CCC/CTC)(P<0.01) and H3H7 (CTC/GTC)(P<0.01).So the cows with H2H4 and H1H2 can be more resistant to pathogens for the breeding.Our data also demonstrated that combined genotype H1H5 with the lowest SCS and C3 protein concentration,H2H4 with the highest CH50,H1H2 with the highest AH50,H1H1 with the highest protein content and fat content and H2H4 with the highest 305-d milk yield were favorable for the mastitis resistance and milk production traits. Bacterial count of antibacterial activity of C3 further proved the conclusion. Thus, H1H5, H1H1, H1H2 and H2H4 can be used as a possible candidate for marker-assisted selection in dairy cattle breeding program.