Novel Variants in GDF9 Gene Affect Promoter Activity and Litter Size in Mongolia Sheep

Litter size is an economically important trait in sheep breeding. The objectives of this study were as follows: (1) to ascertain if any of the 19 known variants in the , 5, and genes are present and associated with the litter size of Mongolia sheep; (2) to identify novel variants in and perform association analysis; and (3) to validate the effects of these promoter variants on the activity of the gene. The results of the 19 known variants showed that the affected the litter size of Mongolia sheep ( < 0.001). The association analysis results of novel variants showed that the (GenBank accession: NC_040256, the same below) in the 3' untranslated region (3' UTR), the (Phe347Ser) in the exon 2, and the SNP in the promotor of were significantly associated with litter size of Mongolia ewes ( < 0.01, < 0.05, and < 0.001, respectively). In addition, the promoter activity analysis showed that the allele at the -332 position ( ) could decrease luciferase activity compared with the allele ( < 0.01). Our findings may facilitate effective marker-assisted selection to increase litter size in Mongolia sheep populations, as well as bring new insights into expression.