Study On The Molecular Mechanism Of Mongolian Spotted Horse Hair Color Formation

Mongolian horse is one of the oldest horse breeds in the world.After a long period of natural and artificial selection,it has formed the characteristics of strong disease resistance,easy fat gain,slow fat loss,cold tolerance,rough feeding resistance,and good grouping.The coat is dense and complex in color.Among them,the phenotype of the spotted hair color is rich and diverse,with spots evenly distributed throughout the body,and spots distributed like a blanket,and the size and shape of the spots are different.In this study,Mongolian spotted horses(adult horses and embryos)were used as experimental subjects.Based on previous researches on equine animal hair color,molecular biology and histological identification of multiple possible candidate genes related to coat color were performed to determine Their role in the process of producing differences in coat color,and the relationship between them.The conclusions are as follows:1.Morphological study of Mongolian spotted horse hair follicle: The structure of Mongolian spotted horse hair follicle is mainly composed of hair shaft and hair root.The results of HE staining showed that the pigment distribution in black skin tissue and white skin tissue of Mongolian spotted horses was significantly different.Melanocytes were mainly distributed in the epidermis and hair bulb of black skin tissue,while no melanin was found in the corresponding position of white skin tissue.Deposition.2.Transcriptomics study of Mongolian spotted horse hair color formation: In this study,6 RNA sequencing libraries of Mongolian spotted adult horses and embryos were filtered and finally obtained about 500 M(million)and 275 M(million)valid data.Significant difference analysis of all m RNAs in the black and white skin tissue libraries of Mongolian spotted adult horses revealed that the expression levels of 740 genes were significantly different in black and white skin tissues of different colors(P<0.05),of which 109 were The gene expression is higher in the black skin tissue of Mongolian spotted horses,and 215 genes are expressed higher in the white skin tissue of Mongolian spotted horses.The significant difference analysis of all m RNAs in the black and white skin tissue library of Mongolian spotted horse embryos revealed that the expression levels of 660 genes were significantly different in the two different color skin tissues of black and white(P<0.05),of which 197 were Gene expression levels were higher in the black skin tissues of Mongolian spotted horse embryos,and 59 genes were expressed higher in white skin tissues of Mongolian spotted horse embryos.In the functional analysis,GO annotations were performed on 109 genes differentially expressed in black skin tissue of Mongolian spotted adult horses.As a result,109 differentially expressed genes were significantly annotated to 26 GO pathways,of which 13 pathways were annotated to biological processes,7 pathways were annotated to cell composition,and 6pathways were annotated to pigment-related genes including TYR,TYRP1,DCT,PMEL,GPR143.GO annotations were performed on 197 genes differentially expressed in the black skin tissues of Mongolian spotted horse embryos.As a result,the differentially expressed 197 genes were significantly annotated to 21 GO pathways,of which,biological processes were annotated to 9 pathways,cell composition was annotated to 5pathways,and molecular function was annotated to 7 pathways.Pigment-related genes were TYR,TYRP1.The differentially expressed genes of Mongolian spotted adult horses and embryos were analyzed by KEGG.The results showed that Mongolian spotted adult horses were significantly enriched in 11 pathways(P<0.05),of which TYR,TYRP1,and DCT were enriched in Tyrosine metabolism and Melanogenesis pathways.Embryos were significantly enriched in 12 pathways(P<0.05),of which TYR,TYRP1,and DCT were enriched in Melanogenesis pathway.Finally,an intersection analysis of the differential genes in the black skin tissues of adult horses and embryos found that TYR,TYRP1,DCT,PAX3,DAPL1,LOC1117690506 are expressed in embryos and adult horses.3.Location of genes related to pigment synthesis in Mongolian spotted horse hair follicles: In Mongolian spotted horse hair follicles,TYR and TYRP1 proteins are not expressed in the hair bulb of the hair follicle.DCT is expressed in the hair matrix of the hair bulb where melanin is deposited.