MYLK4 And MTPN Gene Polymorphisms And Their Association With Growth Traits Of Different Sheep Breed

Sheep is one of the most important economic animals in the world.In order to improve the production efficiency of sheep,identification of molecular markers related to growth traits is so important for animal husbandry and breeding workers.Traditional breeding needs a long time of observation,while molecular marker breeding technics can quickly and accurately evaluate and select potential excellent genotypes in sheep,so as to improve the yield and quality of animal products and then improve the economic benefits of breeding.MYLK4(Myosin Light Chain Kinase 4,myosin light chain kinase)is a kinase that plays an important role in muscle contraction and is closely related to the growth traits of animals.Studies have shown that MYLK4 is involved in muscle contraction,cell proliferation and differentiation,and is an important regulatory factor in muscle development.The protein encoded by MTPN(Myotrophin)gene is a binding protein that participates in and maintains muscle development.Related studies have shown that the protein encoded by MTPN gene may play an important role in regulating the proliferation,differentiation and remodeling of extracellular matrix of animal muscle cells by interacting with Myo D protein.In this study,the physicochemical properties and transmembrane domains of amino acids encoded by two candidate genes were analyzed,and the SNP which may affect the main growth traits of sheep was mined and verified by PCR-SSCP combined with first-generation sequencing in a total of 1557 adult sheep individuals,in order to provide reference for molecular marker breeding of sheep.The main results of this study are as follow:1.Bioinformatics analysis of MYLK4 and MTPN genes in sheepBased on the nucleotide sequence data of sheep MYLK4 and MTPN genes,the physical and chemical properties of the amino acid sequences encoded by the two genes were analyzed.The results showed that the products encoded by MYLK4 were unstable,while those encoded by MTPN were all stable proteins.The transmembrane domains of MYLK4 and MTPN were predicted,and no transmembrane domains were found.In the hydrophilic / hydrophobic analysis of the proteins encoded by the two genes,both showed strong hydrophilicity,which proved that MYLK4 and MTPN did not belong to transmembrane proteins.In the multiple sequence alignment and evolutionary analysis of the two genes,it was found that MYLK4 gene was the most close to antelope and goat and farthest from orangutan and dolphin,while sheep MTPN and goat were closest,and farthest from orangutan and human,which indicated that MYLK4 and MTPN were highly conservative,but there were some species specificity,and it showed no high conservation among different species.A total 14 SNP loci which may affect the growth and development of sheep were screened by mining the SNP mutations of MYLK4 and MTPN genes,including 6 polymorphic variation sites of MYLK4 gene and 8polymorphic loci of MTPN gene.The correlation between 14 SNP loci and sheep growth traits was verified in the follow-up experiments.2.Polymorphism of MYLK4 gene and its association with main growth and development traits in sheepBased on the association analysis between MYLK4 gene polymorphism and growth traits in three sheep species(1557),two polymorphic loci(g.50049402 G>C、g.50049360 C>G)were screened,in which g.50049402 G>C was the dominant allele and CC was the dominant genotype.This polymorphism showed significant effects on the chest circumference,tube circumference,chest width and body height of sheep.G was the dominant allele and GG was the dominant genotype in g.50049360 C>G.This polymorphic locus had significant effects on the oblique length,chest depth and chest circumference of sheep.3.Polymorphism of MTPN gene and its association with main growth and development traits in sheepBased on the analysis of the association between MTPN gene polymorphism and growth traits in three sheep species(1557),a polymorphic locus g.101185485 G>A was determined.Allele A of this polymorphic locus was the dominant allele and AA was the dominant genotype,which significantly affects the body size traits such as body height,chest circumference,tube circumference and so on.In summary,this study analyzed the physical and chemical properties of the amino acid sequences encoded by the two candidate genes MYLK4 and MTPN,excavated and identified the molecular markers affects the key growth traits of sheep,provide a basis for the further study of MYLK4 gene and MTPN gene in sheep,and supporting for more accurate and efficient molecular marker-assisted selection breeding of sheep.