Mechanism of speciation: sperm development is controlled by rapidly evolving piRNAs

Sperm development—central to male reproductive health—is an intricate programmed process of germ cell development.

Male germ cells express a uniquely broad repertoire of transcripts that notably includes rapidly evolving pachytene piRNAs.

While the transcripts of male germ cells are known to program sperm function, I hypothesize that they build isolating mechanisms that prevent the formation of fertile offspring across species.

This proposal aims to unravel a novel genetic mechanism of reproductive isolation (speciation) driven by pachytene piRNAs.

Moreover, the proposal aims to decipher how novel factors in sperm development coordinate the expression of transcripts in time and space.

During sperm development, pachytene piRNAs silence target mRNAs based on sequence complementarity, raising the possibility that pachytene piRNAs and their targets comprise pairs of “interacting genes”?

Incompatibility of different alleles of two interacting genes from two different species results in hybrid sterility, which is a hallmark of reproductive isolation.

Using geographically isolated mouse species and our unique hybrid sterility model in mice, we will directly test if rapid evolution of pachytene piRNA sequences results in building reproductive isolation across species.

Implementing this proposal will provide a new genetic concept to the community of evolutionary genetics, and will contribute to male germ cell biology with new knowledge enabling future therapies for male infertility.