Single Nucleotide Polymorphisms in SLC5A1, CCNA1, and ABCC1 and the Association with Litter Size in Small-Tail Han Sheep

SIMPLE SUMMARY: Litter size is one of the most important reproductive traits in sheep. Four single nucleotide polymorphisms (SNPs), g.70067210 T > C in SLC5A1, g.25350431 C > T and g.25360220 T > C in CCNA1, and g.14413132 C > T in ABCC1, were identified by mass spectrometry and may be associated with litter size in sheep. Four SNPs were genotyped in Small-Tail Han, Hu, Cele Black, Suffolk, Sunite, Prairie Tibetan, and Tan sheep, and the expression patterns of SLC5A1, CCNA1, and ABCC1 were determined in Small-Tail Han sheep with different fecundities. Furthermore, we also studied the FecB mutation’s association with litter size in Small-Tail Han sheep. The results indicated that all genes included in this study were differentially expressed in the ovary and uterus of polytocous and monotocous Small-Tail Han sheep. Furthermore, association analysis indicated that both g.70067210 T > C in SLC5A1 and the FecB mutation in BMPR-IB were significantly associated with litter size in Small-Tail Han sheep. Linear regression analysis of the association of multiple markers (FecB and g.70067210 T > C in SCL5A1) with litter size indicated that homozygous ewes carrying the BB/TT genotype had a larger litter size than any other genotype. ABSTRACT: SLC5A1, CCNA1, and ABCC1 have been extensively studied as candidate genes because of their great influence on the reproductive traits of animals. However, little is known about the association between polymorphisms of the SLC5A1, CCNA1, and ABCC1 genes and litter size in Small-Tail Han sheep. In this study, the expression levels of SLC5A1, CCNA1, and ABCC1 in HPG (hypothalamic–pituitary–gonadal) axis tissues of polytocous and monotocous Small-Tail Han sheep were analyzed by qPCR. To better understand the effects of four single nucleotide polymorphisms (SNPs) comprising of g.70067210 T > C in SLC5A1, g.25350431 C > T and g.25360220 T > C in CCNA1, and g.14413132 C > T in ABCC1, a population genetic analysis was conducted using data obtained from genotyping in 728 sheep from seven breeds. The results indicated that all genes included in this study were differentially expressed in the pituitary and uterus of polytocous and monotocous Small-Tail Han sheep (p < 0.05). The associations of these four SNPs and the FecB mutation with litter size in 384 Small-Tail Han sheep were analyzed, therefore, and it was found that both g.70067210T > C and the FecB mutation were significantly associated with litter size (p < 0.05). The linear regression analysis of the association of multiple markers (FecB and g.70067210 T > C in SCL5A1) with litter size indicated that homozygous ewes carrying the BB/TT genotype had larger litter size than any ewes with any other genotype. In conclusion, the SLC5A1 SNPs significantly affect litter size in sheep and are useful as genetic marker for litter size.