piRNA expression patterns in high vs. low fertility bovine sperm

Area of Science:

• Reproductive Biology
• Epigenetics
• Genomics

Background:

• PIWI-interacting RNAs (piRNAs) are vital for germline development and genomic defense against transposable elements.
• Sperm piRNAs play a role in transmitting epigenetic information to the embryo.
• Idiopathic infertility in Holstein bulls provides a model to study piRNA function in sperm quality.

Purpose of the Study:

• To characterize piRNA expression and genomic clusters in sperm from bulls with varying fertility.
• To investigate the relationship between piRNA profiles, transposable element suppression, and fertility outcomes.
• To assess the impact of sperm piRNAs on early embryogenesis.

Main Methods:

• RNA sequencing to profile piRNA populations in bull sperm.
• Principal component and differential expression analysis to compare fertility groups.
• Bioinformatic mapping to identify piRNA origins and transposable element targets.

Main Results:

• PiRNA populations showed high similarity between high and low fertility bulls, indicating strong conservation.
• Evidence of 'ping-pong' activity confirmed active transposable element targeting in both groups.
• Sperm piRNAs, predominantly 29-30 nucleotides, originated from 226 genomic clusters and targeted multiple transposable element families.
• Targeted gene expression was reduced in early embryogenesis, suggesting a role in epigenetic regulation.

Conclusions:

• Sperm piRNA profiles are highly conserved, essential for viable sperm production and genomic integrity.
• PiRNA-mediated suppression of transposable elements in sperm influences early embryonic gene expression.
• Epigenetic regulation by piRNAs in spermatogenesis likely impacts sperm quality and fertilizing capacity.