Studies On Polymorphisms Of LEPR And ZAG Genes And Their Associations With Growth Traits In Cattle

Genetic variations of LEPR and ZAG genes were detected by PCR-SSCP and DNA sequencing techniques in 655 individuals from six cattle populations(Nanyang,Qinchuan, Jiaxian Red cattle,Jinnan,Angus,and Chinese Holstein),and association analysis were carried out to evaluate the effects of genotypes of the candidate genes on growth traits of three Chinese cattle(Nanyang,Qinchuan,Jiaxian Red 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.Polymorphisms of LEPR gene in six breeds of cattleThe varations of six loci(L1～L6) in LEPR gene were studied.Five SNPs(NC₀07301:g. 26767T>C,26805C>T,27050A>G,27063G>A and 27079G>A)were detected in exon 4 and intron 3 for the first time,and five SNPs were linked completely.The mutation 27079G>A and 27050 A>G resulted to 197 His>Arg and 207 Asp>Asn of LEPR peptide,respectively. SNP was not found in Chinese Holstein cattle.L3 locus was in Hardy-Weinberg disequilibrium in Jiaxian red populations(P<0.05),and was in Hardy-Weinberg equilibrium in the others five populations(P>0.05).Genetic diversity indexes of Ne/PIC/He in Nanyang, Qinchuan,Jiaxian Red cattle,Jinnan,Angus,and Chinese Holstein were 1.56/0.29/0.36, 1.83/0.35/0.45,1.82/0.35/0.45,1.68/0.32/0.41,1.82/0.35/0.45.1.00/0.00/0.00.There was significant difference between Chinese Holstein and Chinese native cattle and Angus in genotype distribution(P<0.01).2.Relationships between genetic variation of LEPR gene and growth traits in three Chinese cattleThree genotypes(AA,AB,and BB) were found in L3 locus.In Nanyang population at 6 months old,genotype AA had greater body height and average daily gain than genotype BB (P<0.05);genotype AA had greater body height,body length than genotype AB and BB (P<0.05 or P<0.01);genotype AA and AB had greater heart girth than genotype BB(P<0.05). In Nanyang population at 12 months old,genotype AA had greater body height,body length than genotype AB and BB(P<0.05 or P<0.01);genotype AA and AB had greater heart girth than genotype BB(P<0.05 or P<0.01).Genotype AA had greater heart girth and hucklebone width than genotype BB(P<0.05),while different genotypes had no significant association with growth traits in Qinchuan population.3.Polymorphisms of ZAG gene in six breeds of cattlePolymorphisms of four loci(Z1～Z4) of the bovine ZAG gene were detected,and polymorphisms were found on Zl,Z3,Z4 loci.Six SNPs(NC₀07326:g 115 T>C,3257 G>A,4013 G>A,4027 C>T,4032 T>C and 4120 C>T) of ZAG gene were detected in 4 loci in six populations,which were all located at coding region.The variations at five SNPs loci (115 T>C,3257 G>A,4013 G>A,4027 C>T and 4120 C>T) caused amino acid mutations, namely,Ser to Pro at position 17,Arg to Lys at positionl89,Gly to Glu at position 233,Arg to Trp at position 238 and Pro to Ser at position 269 of the ZAG peptide.In Chinese Holstein cattle,SNP was only found in Zl locus.In Zl locus,genetic diversity indexes of Ne/PIC/He in six breeds of cattle was 1.41/0.25/0.29,1.48/0.27/0.32,1.47/0.28/0.32,1.34/0.22/0.26, 1.48/0.27/0.32,1.36/0.23/0.27.In Z3 locus,genetic diversity indexes of Ne/PIC/He in six breeds of cattle was 1.25/0.18/0.20,1.06/0.06/0.06,1.05/0.04/0.05,1.03/0.04/0.03, 1.14/0.11/0.12,1.00/0.00/0.00.In Z4 locus,genetic diversity indexes of Ne/PIC/He in six breeds of cattle was 1.52/0.30/0.34,1.47/0.28/0.32,1.48/0.29/0.32,1.39/0.27/0.29, 1.27/0.17/0.18,1.00/0.00/0.00.Most of populations were moderate polymorphic (0.25