ABSTRACT Background The PAPPA2 gene encodes a metalloproteinase critical for regulating insulin‐like growth factor (IGF) bioavailability through cleavage of insulin‐like growth factor‐binding protein 5 (IGFBP5). While its role in human and murine reproduction is documented, its function in sheep reproductive traits remains underexplored. Objective This study aimed to investigate the differential expression patterns and polymorphisms in PAPPA2 gene across diverse sheep breeds and their association with litter size. Methods Genotyping of two single nucleotide polymorphisms (SNPs; g.55757202C>A and g.55924884C>G) was performed in 760 ewes from six breeds. Three high‐fertility Small Tail Han ewes and three low‐fertility Tibetan ewes were selected for tissue‐specific expression analysis. Associations between SNPs and litter size were statistically analysed, and bioinformatics tools were employed to assess structural impacts of mutations. Results The g.55924884C>G SNP exhibited a significant association with litter size in Small Tail Han sheep across parities ( p G mutation induced substantial alterations in the secondary and tertiary structures of PAPPA2 protein, while g.55757202C>A had minimal structural impact, which may be the reason for the change in litter size caused by the g.55924884C>G mutation. Conclusions The g.55924884C>G polymorphism in PAPPA2 gene significantly influences ovine litter size and may serve a genetic marker for selective breeding.
Wang et al. (Thu,) studied this question.