Association Between Novel Polymorphisms In Lepr Gene And Litter Size In Mongolia And Ujimqin Sheep Breeds

Litter size is one of the important economic traits of sheep,which determines the production efficiency of mutton sheep industry.Increasing the litter size is the primary goal in Mongolia and Ujimqin sheep breeding.Therefore,the identification of fecundity-related candidate gene and mutation in Mongolia and Ujimqin sheep breeds,and utilization of markerassisted selection(MAS)technology for increasing the fecundity of Mongolia and Ujimqin sheep breeds,are very important aims of the development of Mongolia and Ujimqin sheep industry at this stage.There were three mutations(rs411478947(R62H),rs428867159 and rs405459906)of Leptin receptor(LEPR)gene have been found in the Davisdale sheep,among them the R62 H mutation is related to the ovulation rate and litter size in this breed.Thus,LEPR gene was considered as a new functional candidate gene affecting the fecundity in sheep.In order to confirm whether the 3 known mutations of LEPR gene are associated with the litter size in Mongolia and Ujimqin sheep breeds,and to identify the breed-specific mutation which associated with the litter size in Mongolia and Ujimqin sheep in LEPR gene.In this study,six Mongolia sheep and six Ujimqin sheep were directly sequenced to identify breed-specific mutation,and the genotypes of known and novel mutations in 250 Mongolia sheep and 121 Ujimqin sheep were detected by Mass ARRAY technology.Therefore,genetic diversity analysis and association analysis between variants and litter size in Mongolia and Ujimqin sheep breeds were performed.In addition,the m RNA secondary structure,amino acid sequence characteristics and protein secondary structure and tertiary structure of LEPR gene were analyzed by bioinformatics.The results showed that:(1)Ten mutations were found in the LEPR gene of Mongolia and Ujimqin sheep(including 1 known mutations:rs411478947(R62H)and 9 novel mutations).Among them,the c.82A>G,c.189T>A,c.240C>T and c.279C>T mutations are in exon 4,the c.546C>T mutation is in exon 6,the c.743C>T mutation is in exon 7,the c.1683G>A mutation is in exon 12,the c.2373T>C mutation is in exon 16 and the g.43179091G>A mutation is in intron 12 of the LEPR gene.(2)There were no significant departures at the 5% level detected by any test for each variant in Mongolia and Ujimqin sheep populations,except for R62 H.The linkage disequilibrium analysis indicated that the c.240C>T and c.279C>T(LD1)SNPs,as well as the g.43179091G>A and c.1683G>A(LD2)SNPs,were in nearly complete Linkage disequilibrium;Association analysis showed that both c.240C>T and c.279C>T(LD1)were significantly associated with the litter size of the two sheep breeds(P < 0.05).(3)Bioinformatics analysis showed that both of c.240C>T and c.279C>T(LD1)could alter the secondary structure and stability of m RNA by affecting minimum free energy.In addition,the c.547C>T(H182Q)and c.743C>T(T248I)could affect the tertiary structure of LEPR protein.In conclusion,the c.240C>T and c.279C>T(LD1)mutations of the LEPR gene were significantly associated with the litter size of Mongolia and Ujimqin sheep breeds.These results provide effective molecular markers for improving the litter size of Mongolia and Ujimqin sheep breeds,and provide scientific basis for the genetic improvement of Mongolia and Ujimqin sheep breeds.