Study On The Phenotype Of Major Skeletal Muscle And Related Gene In Mongolian Horses

Unlike other livestock and poultry,horses are studied not only for food production,but also for the study of their athletic performance.In order to obtain the characteristics of Mongolian horses in terms of movement and meat quality,this study selected healthy and untrained adult stallions and collected skeletal muscles of representative parts of their whole body(head and neck,forelimbs,trunk,abdominal wall side,hind limbs)as the research object.Paraffin-embedded tissue sectioning technology was used to obtain skeletal muscle phenotypic spectrum by immunohistochemistry and HE staining.It was compared to the thoroughbred skeletal muscle phenotype(MINAKO KAWAI,2009)in a punlished article.Due to the differences in the phenotypes of skeletal muscle in different parts,skeletal muscle was divided into five groups by site for statistical comparison.Transcriptome sequencing was performed on skeletal muscle samples from different parts of Mongolian horse to obtain the genes and pathways affecting muscle fiber type,and then two groups of skeletal muscles with large differences in fast and slow muscle fibers were selected from the anterior limbs with high correlation between pathway and skeletal muscle development to compare and analyze,and the genes and pathways related to slow muscle fiber development in Mongolian horse were explored.It seeks a basis for the biological characteristics of Mongolian horse endurance,and also provides theoretical support for Mongolian horse training and the commercial development of horse meat.The results obtained are as follows:1.The phenotypic spectrum of the main skeletal muscles of Mongolian horses was obtained,among which the slow muscle fibers of Serratus cervico,supraspinatus,biceps brachia,flexor carpal radial,gastrocnemius,rhomboid and thoracoventral serratus were relatively low,and had high endurance training potential.The proportion of wrist radial extensors,triceps brachial and gluteus mesoamericas slow twitch fibers reaches more than70%,which meets the requirements of high-quality meat and can be used as the key part of Mongolian horse meat development.2.The obtained Mongolian horse phenotypic spectrum was compared with the quoted thoroughbred horse phenotypic spectrum,and Mongolian horses were higher than thoroughbred horses except for the uniform rhomboid muscle in the proportion of skeletal muscle slow twitch fibers,and Mongolian horses conformed to the characteristics of endurance horse breeds.Among them,the differences in forelimbs and trunk were very significant(P<0.01),and the differences in hindlimbs and abdominal wall were significant(P<0.05).The triceps brachia,gluteus medius and hemimaebra muscle had a large difference in slow muscle fibers in the two horse breeds,and it was suspected that they were the key skeletal muscles affecting the athletic performance of horses.3.Through the RNA-seq study of different parts of skeletal muscle in Mongolian horse,the results of differential expression gene enrichment were as follows: head and neck skeletal muscle was mainly enriched into pathways related to lipid metabolism and amino acid metabolism,which could be used for the development and research of meat quality.Trunk,ventral lateral skeletal muscle enrichment into terms related to differentiation in different parts of the body.Skeletal muscle of the anterior and forelimb is more related to the classification of skeletal muscle and can be used to study the development of slow twitch fibers.4.Two groups of skeletal muscles with large differences in fast and slow muscle fibers were selected from the front and rear limbs for RNA-seq study,and 192 differentially expressed genes were screened,including 46 upregulated genes in the slow twitch fiber group and 4 upregulated genes in the fast twitch fiber group.GO and KEGG enrichment analysis showed that pathways such as TCA circulation and adrenergic signaling in cardiomyocytes were associated with the development of slow twitch fiber types.