SNPs Screening Of Growth Related Genes And Correlation Analysis Between Genetic Polymorphisms And Growth Traits In Dazu Black Goats

The purpose of this study was to excavate and identify genetic markers significantly correlated with the important growth traits of Dazu black goat,and to provide scientific basis for marker-assisted selection to improve growth performance in Dazu black goats.Firstly,the MSTN gene of Boer goat and Dazu black goat was amplified,the mutation sites were screened,and genetic divergence of the mutation sites and their haplotypes was evaluated in Boer goat,Nubian goat,Youzhou goat and Dazu black goat population.Secondly,using the principle of linkage disequilibrium to screen the tag SNP of MSTN gene,and combined with the known candidate SNPs of growth-related gene GH and IGF1 to perform correlation analysis between genetic polymorphisms and growth traits?body weight,body length,chest circumference,body height?)in Dazu black goat to find the dominant genotypes.The results and conclusions of this study are as follows:1.MSTN gene amplification and the variable sites screeningThe MSTN gene of Boer goat and Dazu black goat was amplified by PCR and sequenced,and the sequence covering all coding regions was successfully obtained.The published sequence?GenBank:JF312048.1 and GenBank:JX078969.1,88 bp-6029 bp?was used as a reference,and 29 SNPs were screened in two populations.One of the loci was distributed in the regulatory region,three were located in the coding region,and the remaining 25 were distributed in intron.2.Polymorphic analysis of SNPs of MSTN gene in different populationsCombined with SNaPshot and resequencing technology,20 SNPs were found to be polymorphic in Boer goats,Nubian goats,Youzhou black goats and Dazu black goats?a total of 148 samples?.Among them,only 5 loci in the Boer goats were polymorphic,and 18 and 20 SNPs were found to be polymorphic in the local breeds of Youzhou goat and Dazu black goats.The average H_E values of the 20 SNPs in the four populations were larger than the H_O values;the H_O,H_E and PIC values were the smallest in the Boer goat,while the H_O,H_E and PIC values in the Dazu black goat were the largest.20 SNPs were in low polymorphism?PIC=0.070?in Boer goats and moderate polymorphisms in all other three population?PIC ranged from 0.263 to 0.307?.Except for four sites in Nubian goats that deviated from Hardy Weinberg's balance,the remaining sites were in the Hardy Weinberg equilibrium in all four population samples.3.Genetic divergence of SNPs of MSTN gene among populationsThe genetic divergence of 20 SNPs between the Boer goat and the other three goat breeds was significantly different(F_ST,p<0.05).However,there was no significant differences or low degree of divergence between Dazu Black Goat,Nubian Goat and Youzhou goat.A total of 18 haplotypes were constructed by using the Phase method in the four population.Among them,haplotype H₂ was shared among all four populations and has the highest frequency?54.05%?,and 8 haplotypes were found in Dazu black goats,of which H₁7 and H₁8 were unique to this breed.Using phylogenetic methods such as Network and MEGA 5,found that 18 haplotypes formed two major branches.The haplotypes carried by Boer goats only exist in the first branch,the haplotypes connecting the two branches were mainly distributed in Nubian goats,and the haplotypes found in the two local breeds were distributed in both branches.4.Correlation analysis between tag SNPs polymorphism of MSTN gene and growth traits in Dazu black goatFive tag SNPs including Snp₄25?C/T?,Snp₁583?A/G?,Snp₂732?C/T?,Snp₄552?A/C?,and Snp₅167?C/T?were screened using Haplo View software.Correlation analysis between genotype of tag SNPs and growth performance was performed in 169 individuals of Dazu black goat.The results showed that there was no significant correlation between the genotypes of five tag SNPs and the growth traits of Dazu black goats?P>0.05?.In the genotype combination analysis,the GE-M3?C/T,A/A,T/T,C/C,C/C?was the dominant genotype combination for both primary weight and2-month weight?P<0.05?.The haplotype HP-M1?TATCC?found in GE-M3 genotype was only exist in two local breeds and belonged to branch?.In addition,the genotype combination GE-M13?C/C,A/A,C/T,A/A,C/C?significantly correlated to the body height of the Dazu black goats at 6 months?P<0.05?,which was composed of haplotype HP-M5?CACAC?.This haplotype accounts for 45.27%of the total number and belongs to branch?in phylogenetic differentiation.5.Correlation analysis between genetic diversity of GH and IGF1 genes and growth traits of Dazu black goatsCorrelation analysis between 5 SNPs?GH-781,GH-1148,IGF1-1617,IGF1-4700and IGF1-5752?and growth traits of Dazu black goat?totally 169 individuals?found that GH-1148?C/The T?was significantly correlated with body length?P<0.05?,height?P<0.05?and chest circumference?P<0.01?at the age of six month,and the T/T type was the dominant genotype.The IGF1-1617?G/A?was significantly correlated with body weight and body height of two-month-old goats?P<0.05?,and the G/A type was the dominant genotype.There were no significant correlations at other sites.The genotype combination analysis found that GE-G4?G/G,T/T?combination was significantly correlated with body length,height and chest circumference at the age of six months?P<0.05?,and GT was dominant haplotype.The combination of GE-I3?G/A,T/T,G/G?was significantly correlated with body weight and body height at the age two months?P<0.05?,and G-T-G and A-T-G were dominant haplotypes.