Comprehensive Analysis of PAPPA2 Expression and Genetic Variants in Sheep and Their Association With Litter Size

Area of Science:

• Animal Genetics
• Reproductive Biology
• Genomic Selection

Background:

• The PAPPA2 gene is crucial for regulating insulin-like growth factor (IGF) bioavailability.
• Its role in sheep reproductive traits, particularly litter size, is not well understood.
• IGFBP5 cleavage by PAPPA2 influences reproductive functions.

Purpose of the Study:

• Investigate PAPPA2 gene expression patterns in sheep.
• Identify PAPPA2 gene polymorphisms associated with litter size.
• Analyze the structural impact of identified polymorphisms on the PAPPA2 protein.

Main Methods:

• Genotyped 760 ewes from six breeds for two PAPPA2 SNPs (g.55757202C>A and g.55924884C>G).
• Performed quantitative PCR (qPCR) for tissue-specific gene expression analysis.
• Utilized bioinformatics tools to assess the structural consequences of mutations.

Main Results:

• The g.55924884C>G SNP was significantly associated with litter size in Small Tail Han sheep.
• PAPPA2 expression was notably higher in the ovaries of low-fertility Tibetan sheep compared to high-fertility Small Tail Han sheep.
• The g.55924884C>G mutation caused significant structural changes in the PAPPA2 protein.

Conclusions:

• The g.55924884C>G polymorphism in the PAPPA2 gene is a key factor influencing ovine litter size.
• This specific polymorphism may serve as a valuable genetic marker for selective breeding programs in sheep.
• Understanding PAPPA2's role can enhance sheep reproductive efficiency.