Investigate The Association Of Polymorphisms Of PPARγ Gene And MYF5 Gene With Part Economic Traits In Rabbits

peroxisome proliferator-activated receptors (PPARγ) plays a key role in the regulation of adipocyte differentiation, fat metabolism, insulin sensitivity, glucose metabolism and energy metabolism, while myogenic factor 5 (MYF5) regulates the muscle determination, differentiation, proliferation and postnatal muscle development. In this study, the polymorphisms in coding regions of PPARy and MYF5 genes by direct sequencing and a total 235 rabbits including 93 Ira (IRA),81 Champagne (CHA) and 61 Tianfu Black (TFB) rabbits were genotyped using Sequenom MassARRAYTM SNP genotyping method. And then, the candidate SNPs which had genetic effects were screened. Next, the 271 New Zealand White (NZW) rabbits were used to verify the association. Finally, the expression of PPARy mRNA was investigated with RT-PCR method to research the mechanism to traits. The association analysis being performed between candidate SNPs and performance traits was to provide the molecular markers for rabbit breeding. The results were followed:1. One SNP (c.207A>C) and three SNPs (c.66G>A, c.571T>C, c.708C>T) were detected in coding regions of PPARy gene and MYF5 gene by direct sequencing, respectively. c.571T>C was nonsynonymous mutation, which resulted in amino acid change from serine to proline. While the|ΔRSCU| of c.708C>T was higher than that of c.66G>A. So PPARy gene c.207A>C and MYF5 gene c.571T>C, c.708C>T were further researched.2. Three genotypes (AA, AC, CC) of PPARy gene c.207A>C were all detected in IRA, CHA and TFB rabbits. Genetic structure analysis demonstrated that the frequencies of three genotypes were 0.3804,0.4565,0.1631 in IRA rabbits, respectively. In CHA rabbits, the frequencies of three genotypes were 0.2375,0.5500, 0.2125, respectively. In TFB rabbit, the frequencies of three genotypes were 0.4590, 0.5246,0.0164. A allele was the superiority allele, the frequencies were 0.6086, 0.5125,0.7213, respectively. In amplied population, NZW rabbits, the frequency of AA genotype was highest, which was 0.5092. The frequencies of AC and CC genotypes were 0.4317,0.0590, respectively. x2 test suggested that c.207A>C was in Hardy-Weinberg equilibrium in four rabbit breeds (P>0.05).3. Three genotypes (TT, TC, CC) of MYF5 gene c.571T>C were all detected in IRA, CHA and TFB rabbits. Genetic structure analysis demonstrated that the frequencies of three genotypes were 0.3371,0.3371,0.3248 in IRA rabbits, respectively. In CHA rabbits, the frequencies of three genotypes were 0.1235,0.3580, 0.5185, respectively. In TFB rabbits, the frequencies of three genotypes were 0.5833, 0.3000,0.1167, respectively. T allele was the superiority allele, the frequencies were 0.5056,0.3025,0.6975, respectively. In amplied population, NZW rabbits, the frequency of TT genotype was highest, which was 0.5234. The frequencies of TC and CC genotypes were 0.2031,0.2735, respectively, χ2 test showed that c.571T>C locus was in Hardy-weinberg equilibrium in CHA and TFB rabbits, while c.571T>C locus severely deviated from Hardy-Weinberg equilibrium in IRA and NZW rabbits (P< 0.01).4. Three genotypes (CC, CT, TT) of MYF5 gene c.708C>T were all detected in IRA, CHA and TFB rabbits. Genetic structure analysis demonstrated that the frequencies of three genotypes were 0.3978,0.4946,0.1076 in IRA rabbits, respectively. In CHA rabbits, the frequencies of three genotypes were 0.1605、0.6420、 0.1975, respectively. In TFB rabbits, the frequencies of three genotypes were 0.6721, 0.3115,0.0163, respectively. T allele was the superiority allele, the frequencies were 0.6451,0.4814,0.8278, respectively. In amplied population, NZW rabbits, the frequency of CC genotype was highest, which was 0.5352. The frequencies of TC and CC genotypes were 0.2031,0.2735, respectively. χ2 test suggested that c.708C>T locus deviated from Hardy-Weinberg equilibrium in CHA (p<0.05) and NZW rabbits (P<0.01).5. For PPARy c.207A>C in CHA and IRA rabbits, the body weight of 84 days of age (BW84) of AC genotype was markedly higher than that of AA genotype individuals (P<0.05), but the AA and AC genotypes had observably higher intramuscular fat content of longissimus muscle (IMF) than CC genotype individuals (P<0.01) and the IMF of AA genotype was significantly higher than that of AC genotype (P<0.05). For PPARy c.207A>C locus in NZW rabbits, the BW70 and BW84 of CC genotype individuals were significantly higher than those of AA genotype individuals(P<0.05), and the average daily weight gain from 35 to 84 days of age (ADG1) of individuals with AC genotype was significantly higher than that of individuals with AA(P<0.05) and AC genotypes (P<0.01).6. MYF5 c.571T>C was significantly associated with BW84 in IRA and CHA rabbits. The BW84 of TC genotype individuals was significantly higher than that of TT genotype individuals (P<0.05). Similarly, the BW84 of TC genotype NZW rabbits was markedly higher than that of individuals with TT genotype (P<0.05), and ADG1 was significantly higher than those with TT genotype (P<0.05). But there is no statistical significance between c.571T>C and other observed traits including BW28, BW70, average daily weight gain from 28 to 84 days of age (ADG2), eviscerated weight (EW), semi-eviscerated weight (ESW), eviscerated slaughter rate (ESR), semi-eviscerated slaughter rate (SESR), IMF, intramuscular fat content of right hind leg (HIF) and ripe meat rate (RMR) in IRA, CHA rabbit (P>0.05).7. MYF5 c.708C>T locus was significantly associated with BW84, EW, ESW in IRA and CHA rabbits. The BW84 of CT genotype individuals was significantly higher than those with CC genotype (P<0.05), and the least squares mean of EW (1309.4243±13.3502), ESW (1413.9414±14.3049) markedly greater than that of CC genotype (EW=1250.4335±18.9968 and SEW=1352.6705±20.3554) (P< 0.05). Similarly, the BW 84 of CT genotype of NZW rabbits was significantly higher than those with CC genotype (P<0.05).8. The expression of PPARy mRNA was increasing from 35 days to 56 days of age and decreasing from 56 days to 70 days of age in NZW rabbits. The expression of PPARy mRNA at age stage of 56 days was significantly higher than that at age stages of 35 days and 70 days (P<0.01). Besides, the expression of PPARy mRNA at age stage of 35 days was also significantly different from that at age stage of 70 days (P< 0.01). However, there was no significant difference among expression of PPARy mRNA of different genotypes of c.207A>C at all age stages (P>0.05).The results of study suggested that MYF5 gene could be used as a candidate gene affecting rabbit growth, and MYF5 c.571T>C and c.708C>T were used as molecular markers for selecting body weight of 84 days of age. Selecting TC genotype of c.571T>C and CT genotype of c.708C>T could bring better performance. PPARy c.207A>C was associated with body weight of 84 days of age, but it could not make the expression change of PPARy mRNA.