| The goat industry dominated by Shaanbei white cashmere(SBWC)goat is one of the leading industry of the agricultural economy in northwest China.Its reproductive performance and growth performance affect the economic development of local goat breeding industry.The application of molecular marker-assisted selection(MAS)breeding has been identified as an effective way to improve the economic traits of goats,thereby promoting the high-quality development of the goat industry.Insulin-like growth factor 2m RNA binding proteins(IGF2BPs)family members include IGF2BP1,IGF2BP2 and IGF2BP3.Our laboratory has previously verified that In Del mutations of IGF2BP1 were associated with the growth traits of SBWC goats and reproductive traits of sheep.Based on our previous study,a total of 918 SBWC goats were selected.Their ear tissues were collected and the genomic DNA was extracted.Primers were designed to amplify In Del of goat IGF2BP2 and IGF2BP3 genes.Thereafter,the association between these In Del loci and reproductive and growth performance was assessed.Then,bioinformatics analyses were performed to predict the sequence characteristics of IGF2BP2 and IGF2BP3 genes,along with this,their m RNA expression in different tissues of goats was also detected.Finally,the key In Del mutation sites of IGF2BP2 and IGF2BP3 genes were excavated with an attempt to provide the scientific theoretical basis for improving reproductive and growth traits of goats.The main results of this experiment are as follows:1.Bioinformatics analysis and mRNA expression of IGF2BP2 and IGF2BP3 genes in goatsFirst of all,based on the sequences provided by NCBI,the sequence characteristics and structural similarities and differences of IGF2BP2 and IGF2BP3 genes were predicted through bioinformatics analysis.The results showed that the m RNA sequences of goat IGF2BP2 and IGF2BP3 genes had the highest similarity with sheep and the lowest similarity with chicken.Their secondary structures are composed of α-helix,strand and loop,and their domains are composed of RRM and KH domains.Subsequently,The m RNA expression levels of IGF2BP2 and IGF2BP3 genes in different tissues of SBWC goats and ovarian tissues of ewes with different fertility were further analyzed.The results showed that the IGF2BP2 gene had the highest expression levels in the muscle and spleen tissues of fetal goats,and the highest expression levels in the fat tissues of adult goats.Moreover,the highest expression level of IGF2BP3 gene was found in the spleen tissue of fetal goats,and the highest expression level was found in the spleen and fat tissue of adult goats.In addition,in the ovarian tissue of adult female SBWC goat,the m RNA expression level of IGF2BP2 in the single-lamb group was significantly higher than that of the multi-lamb group(P<0.05).2.Discovery of genetic variation loci of IGF2BP2 and IGF2BP3 genes in goatsBased on the mRNA expression levels of IGF2BP2 and IGF2BP3 genes,we designed primers according to the sequence and mutation information provided by NCBI and Ensembl databases to detect whether the IGF2BP2 and IGF2BP3 genes have polymorphisms.The results showed that the IGF2BP2 gene had polymorphisms at P4-Ins-13 bp and P5-Del-12 bp sites.The minor allelic frequencies of P4-Ins-13 bp and P5-Del-12 bp sites were 0.349 and 0.295,and their PIC values were between 0.329 and0.351,which belonged to moderate polymorphism,and there was no linkage relationship between them.The P3-Ins-12 bp and P7-Del-10 bp sites were found to have polymorphisms for the IGF2BP3 gene.The minor allelic frequencies of P3-Ins-12 bp and P7-Del-10 bp sites were 0.431 and 0.346,and their PIC values also indicated that they were moderate polymorphisms,and there was no linkage relationship between them.In conclusion,P4-Ins-13 bp and P5-Del-12 bp of IGF2BP2 gene,as well as,P3-Ins-12 bp and P7-Del-10 bp of IGF2BP3 gene were identified to have polymorphisms which are worthy of further exploration.3.Association analysis between genetic variation sites of IGF2BP2 and IGF2BP3 genes and economic traits in goatsThen,we continued to investigate the practical value of the four In Dels identified in the above results,along with this,their impact on the economic traits of SBWC goats was measured using χ2 test and association analysis.For the IGF2BP2 gene,P4-Ins-13 bp was significantly associated with litter size(P<0.05).Also,different genotypes were also differentially distributed in different lambing type populations and DD genotypes were the dominant genotypes.In keeping with this,this locus was significantly associated with chest width,chest depth,heart girth,and cannon circumference(P<0.05),and II genotypes showed superior phenotype in growth performance.However,no significance was observed between P5-Del-12 bp and litter size and growth traits of SBWC goats(P>0.05).For the IGF2BP3 gene,as expected,different genotypes and alleles of P3-Ins-12 bp have different distributions in single-lamb and multi-lamb populations.It is also significantly associated with litter size of SBWC goats(P<0.05)and ID genotypes showed superior phenotypes.Additionally,P3-Ins-12 bp also exerted influence on the height at hip cross and heart girth(P<0.05).Of note,the significant level between this locus and the heart girth reaches 0.01,and II genotypes showed better potential for improving heart girth.No significant association was detected between P7-Del-10 bp and litter size and growth traits of SBWC goats(P>0.05).In conclusion,the P4-Ins-13 bp of IGF2BP2 gene and the P3-Ins-12 bp locus of IGF2BP3 gene showed potential to be applied as effective molecular markers to improve litter size and growth traits of SBWC goats and provide a certain scientific theoretical basis for actual breeding. |
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