| IRS, IR/IGF receptor protein tyrosine kinase substrate,is an important mediators to connecting the signal molecules on the upstream and downstream of IR/IGF signaling pathways. Its function is regulating body growth and development. BMPR1B is bone morphogenetic protein receptor. It regulates granular cell differentiation, promotes follicular development, increase the number of follicles and promote bone growth through participating in signal transduction of BMP-2,BMP-4,BMP-6,BMP-7, BMP-15 and GDF-5. In this study, IRS-1 and BMPR1B genes were served as the candidate genes. A total of 785 rabbits in four breeds including 587 growing rabbits and 198 adult female rabbits were involved in the study. The SNPs in the coding regions of IRS-1 and BMPR1B genes were detected by PCR direct-sequencing. After that, the candidate SNPs were genotyped using RFLP and HRM methods. Then, a ssociation analysis between candidate SNPs and rabbit production and reproduction traits were analyzed. Finally, the IRS-1 mRNA relative expression in liver was analyzed. The results were followed:1. Nine silent mutation SNPs, c.189G>T、c.337C>T、c.1341C>T、c.2541T>A、 c.2574G>A、c.2811C>T、c.3234G>A、c.3508T>C and C.3636C>T, were detected in IRS-1 coding region.2.Three genotypes (GG、GT、TT) of c.189G>T and three genotypes (GG、AG、 AA) of c.2574G>A were detected in New Zealand Rabbits and Tianfu black rabbit, while only two genotypes (GG、GT) of c.189G>T and two genotypes (GG、AG) of c.2574G>A were found in Ira rabbit and Champagne rabbit. The two loci were in moderate polymorphism (0.25<PIC<0.5) in New Zealand rabbit, while in low polymorphism (PIC<0.25) in Ira rabbit and Champagne rabbit, and Tianfu black rabbit, X2 test showed that two candidate SNPs were in Hardy-Weinberg equilibrium in four breeds (P> 0.05).3. In New Zealand Rabbit, the c.189G>T and c.2574G>A were all significantly associated with body weight of 56 (BW56),70 (BW70),84 (BW84) days of age and average daily gain weight from 35 days to 84 days (ADG35.84) (p< 0.01 or p< 0.05). In Tianfu black rabbit, Ira rabbit and Champagne rabbit, the BW84, ADG35-84 PH24 of hind leg muscle of GT genotype of c.189G>T locus were significantly higher than those of GG genotype. There is no statistic association between c.2574G>A and observed traits.4. There were four haplotypes (c.189G>T and c.2574G>A) for c.189G>T and c.2574G>A. Seven haplotype combinations (hlh2(GGAG), hlh3(GTAA), hlh4(GTAG), h2h2(GGGG), h2h4(GTGG), h3h3(TTAA), h3h4(TTAG) were detected in New Zealand Rabbit and four haplotype combinations (hlh2(GGAG), hlh4(GTAG) h2h2(GGGG), h2h4(GTGG))were detected in other three breeds. The BW56, BW70 and ADG35-84 of h3h3 were significantly higher than those of hlh2, hlh4, h2h2 and h2h4 (p< 0.01 or p< 0.05) in New Zealand Rabbit. The BW84, ADG35-84, intramuscular fat content (IMF) of hlh4 were significantly higher than those of other three combinations (P<0.05) and the IMF of h2h4 was significantly higher than that of h1h2 (P<0.05) in other breeds.5. The relative IRS-1 mRNA expression at 56 days of age was significantly higher than that at 35 days of age (P<0.05). For c.189G>T, the expression of GG genotype individuals was significantly higher than that of TT genotype individuals (P<0.05).6. Thirteen synonymous mutations (c.9C>T, C.54C>T, c.75T>A, c.88C>T、 c.96T>C, c.117G>A, c.384A>G C.540C>T, c.603T>C, c.1254T>A、c.1332A>G, c.1356A>G, c.1436A>G)) and a synonymous mutation (leu 131 ser) were detected by mixed sequencing.7. Three genotypes (GG, GA and AA) of c.117G>A were detected in New Zealand rabbit and Tianfu black rabbit. This locus was in moderate polymorphism in these two breeds (0.25<PIC<0.5). X2 test showed that two candidate SNPs were in Hardy-Weinberg equilibrium in New Zealand rabbit and Tianfu black rabbit (p> 0.05).8. The association analysis indicated that litter numbers, numbers born alive, numbers born alive of 21 days of age and litter weight of 21 days of age of AA genotype of c.117G>A were significantly higher than those of GG and GA genotypes (P< 0.05 or P< 0.01). The association analysis between c.117G>A and growth traits in New Zealand growing rabbit demonstrated that the BW35 of AA genotype individuals was significantly greater than that of GG genotype individuals (p< 0.05). |
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