Polymorphisms of the HRG, FETUB, and GUCY1A1 genes and their association with litter size in sheep

Abstract. Litter size is one of the key factors affecting the efficiency of sheep breeding, and previous studies found that the HRG, FETUB, and GUCY1A1 genes were closely related to litter size in sheep. This experiment aims to explore the polymorphisms of the g.405442728A>G locus of the HRG gene, the g.421655951C>T locus of the FETUB gene, and the g.414050897G>C locus of the GUCY1A1 gene and their association with sheep litter size. The MassARRAY® single-nucleotide polymorphism (SNP) genotyping technique was used to detect the polymorphisms of these loci in five sheep breeds, i.e., Small-tailed Han sheep, Hu sheep, Cele black sheep, Sunite sheep, and Bamei mutton sheep. In addition, the association between the polymorphisms of these genes and the litter size of Small-tailed Han sheep was also analyzed. The results showed that the g.405442728A>G locus of the HRG gene was moderately polymorphic (0.25 < PIC <0.5) in both monotocous and polytocous sheep breeds; the g.421655951C>T locus of the FETUB gene was lowly polymorphic (PIC <0.25) in five sheep breeds; the g.414050897G>C locus of GUCY1A1 showed moderately polymorphism in Small-tailed Han sheep (0.25 ≤ PIC <0.5) and low polymorphism in four other sheep breeds (PIC <0.25). The chi-squared test results showed that the g.405442728A>G locus of the HRG gene was in the Hardy–Weinberg equilibrium state in five sheep breeds (P>0.05). The g.421655951 C>T locus of the FETUB gene and the g.414050897G>C locus of the GUCY1A1 gene were in the Hardy–Weinberg equilibrium state in Small-tailed Han sheep (P>0.05) and in the Hardy–Weinberg disequilibrium state in other sheep breeds (P<0.05). The association analysis showed that the g.405442728A>G locus of the HRG gene and the g.421655951C>T locus of the FETUB gene had a significant impact on the litter size of sheep (P<0.05), while the g.414050897G>C locus of the GUCY1A1 gene had no significant impact on the litter size (P>0.05). In summary, the HRG gene and the FETUB gene can be used as potential molecular markers for the selection of the litter size in sheep.