The Variations Of Candidate Genes Related To Energy Homeostasis And Their Association With Growth Traits In Cattle

Genetic variations of energy homeostasis related genes (AGRP, POMC, CART, MC3R, MC4R, Ghrelin, HTR1B, and HTR2A) were detected by PCR-RFLP, PCR-SSCP and DNA sequencing techniques in 671 individuals of seven populations (Nanyang, Qinchuan, Jiaxian Red cattle, Jinnan, Luxi, Angus, and Chinese Holstein), and association analysis were carried out to evaluate the effects of genotypes of candidate genes on growth traits of three Chinese cattle. The objects were to discovery the hereditary characteristics and to explore molecular markers with significant effects on economic important traits for efficient selection and improvement of Chinese cattle, and to provide genetic information for foundation of molecular marker database, protection and usage of breed resource of Chinese cattle. The results were as follows:1. Relationship between genetic variation of AGRP gene and growth traits in Nanyang and Qinchuan cattleThe varations of three loci in AGRP gene were studied. Two SNPs (603243 C>T and 603093 C>T,ref. NW₉29325) were detected in 3'flanking region for the first time. The 603093 C>T mutation introduced a MspI recognizing site. The similarity of AGRP gene between Bos tarus and Babalus bubalis is 96%. There was significant difference between Holstein and Chinese native cattle and Angus in genotype distribution. No polymorphism in AGRP exons was detected in the studied populations.The association between AGRP-MspI polymorphism and growth traits in Nanyang and Qinchuan cattle was analyzed. The results indicated that it didn't influence the growth traits of Nanyang cattle. The individuals carried 603093T allele had higher body weight and withers height than that of wild genotype individuals of Qinchuan cattle. 2. Relationship between genetic variation of POMC gene and growth traits in three Chinese cattleFor the first time, three SNPs (811845 C>T, 811821 T>C and 811797 A>G,ref. NW₉28357) were detected in P5 locus, which located at 3'flanking region of POMC gene. The two SNPs was moderate polymorphic (0.256 month was higher in Nanyang cattle with genotype BB than that with genotype AA (P<0.05). The body weight, height at hip cross and rump length was higher in Qinchuan cattle with genotype AB than that with genotype AA (P<0.05). The wither height, heart girth and hip width in Jiaxian red cattle with genotype BB was higher than that with genotype AA (P<0.05).3. Relationship between genetic variation of CART gene and growth traits in Nanyang and Qinchuan cattleNine SNPs (329037 T>C, 329004 T>C, 328914 T>C, 328899 T>C, 329668 A>G, 330141 G>C, 330216 G>A, 330854 C>G and 330852 C>T,ref. NW₉29854) of CART gene were detected in 4 loci, which were all located at noncoding region. The genotype distribution of the 4 polymorphic loci in Holstein was different from Chinese native cattle (P<0.01). The PIC of detected SNPs in 7 population was less than 0.25 except 329668 A>G, which indicated that bovine CART gene was conserved.The 4 studied loci were significantly associated with body weight of 18 month and 24 month, and body length of 18 month in Nanyang cattle. The individuals with genotype AA in C1 and C4 loci were higher than that of individuals with genotype AB, and the individuals with genotype AA in C2 and C3 loci were higher than that of individuals with genotype AB and BB (P<0.05). For Qinchuan cattle, the body weight and body length of individuals with genotype AA were significantly higher than that of the individuals with genotype AB in C1 locus, the height at hip cross of individuals with genotype AA were significantly higher than that of the individuals with genotype BB in C2 locus, the hip width of individuals with genotype AA were significantly higher than that of the individuals with genotype AB and BB in C3 locus, and the hip width of individuals with genotype AA were significantly less than that of the individuals with genotype BB in C4 locus (P<0.05). 4. Relationship between genetic variation of MC3R gene and growth traits in Nanyang and Qinchuan cattleTen SNPs (1986929 T>G, 1986830 C>T, 1986764 T>C, 1986395 T>C, 1986353 T>C, 1986342 C>T, 1986227 T>C, 1986167 G>A, 1985897 G>A and 1985724 C>T,ref. NW₀01502669) of MC3R gene were detected in 3 loci. The mutation 1986342 C>T resulted to183 S>F of MC3R peptide. The PIC of MC3R1 locus in 7 populations was over 0.5, which indicated the locus was polymorphic. And this locus was in Hardy-Weinberg disequilibrium (P<0.05).MC3R1 locus was significantly associated with the withers height and body length of 6 month, average daily gain of 0⁶ month, body length and heart girth of 18 month, body weight and withers height of 24 month were significantly associated with of Nanyang cattle, of which the mutational individuals were higher than wildtypes (P<0.05). MC3R3 locus was significantly associated with body length of 6 month, body weight and heart girth of 12 month, body weight and heart girth of 18 month, body weight and body length of 24 month, and average daily gain of 13¹8 month of Nanyang cattle, which of the mutational individuals were higher than wildtype individuals (P<0.05).The body weight, body length and heart girth of mutational individuals in MC3R1 locus were significantly higher than that of wildtype individuals in Qinchuan cattle (P<0.05). The body weight and heart girth of individuals with heterozygous genotype in MC3R2 locus were higher than that of homozygous genotype individuals (P<0.05). The body weight and height at hip cross of individuals with genotype AB of MC3R3 locus were significantly higher than that in individuals with genotype AA and AC (P<0.05).5. Relationship between genetic variation of POMC gene and growth traits in three Chinese cattleSix SNPs (109021 C>T, 109163 C>G, 110279 C>G, 110209 A>T, 110210 T>G and 110147 A>G,ref NW₉30353) of POMC gene were detected in 5 loci, four of which located at 5'flanking region were detected for the first time. Four SNP haplotypes (00, 01, 10, 11) were detected in studied populations. Haplotype 00 was not detected in Jiaxian red cattle population, haplotype 00 and 01 were not detected in Holstein population, and only haplotype 11 was detected in Angus population.MC4R4 locus was significantly associated with body weight and body length of 12 month, average daily gain of 7¹2 month, body weight and body length of 18 month, average daily gain of 13¹8 month, body weight and hucklebone width of 24 month, and average daily gain of 17²4 month of Nanyang cattle, of which mutational individuals were higher than that of wildtype individuals (P<0.05). For the MC4R4 locus, the body weight and body length of individuals with genotype BB were significantly higher than that of individuals with genotype AA in Jiaxian red and Qinchuan population (P<0.05). For MC4R5 locus, the body weight and heart girth of mutational individuals in Nanyang cattle were significantly less than that of wildtype individuals (P<0.05), and the body weight and body length of individuals with genotype AA were significantly higher than that of individuals with genotype BB in Jiaxian red population (P<0.05).6. Relationship between genetic variation of Ghrelin gene and growth traits in three Chinese cattleOnly one SNPs (ref NW₀01494127) of Ghrelin gene were detected in 4 loci in studied populations. The SNP locus 403725 T>C were in Hardy-Weinberg disequilibrium in Jiaxian red and Jinnan populations (P<0.05), and was in Hardy-Weinberg equilibrium in the other 5 populations (P>0.05).The body weight and hucklebone width of 24 month of individuals with genotype BB were significantly higher than that of individuals with genotype AA in Nanyang population (P<0.05). The body weight and heart girth of individuals with genotype BB were significantly higher than that of individuals with genotype AA in Qinchuan population (P<0.05). The body weight, heart girth, and body length of individuals with genotype BB were significantly higher than that of individuals with genotype AA in Jiaxian red population (P<0.05).7. The genetic variation of HTR1B geneA total of six SNPs (G205T, C507T, C546G, C744T, G816A and G942A) of HTR1B gene were detected in 4 loci in studied populations. The mutation G205T resulted to 69 Ala>Ser of HTR1B peptide. The SNPs were at Hardy-Weinberg equilibrium except C507T and C546G in all genetic population. The frequencies of allele 205T of Holstein were much higher than that of the other six beef cattle population. Almost the PIC of all SNPs were not more than 0.10 except that of G205T in Holstein cows, which indicated the bovine HTR1B gene was conserved.