Reproduction Abstracts

Introduction: The production of functional spermatozoa is a highly complex process that requires tight regulation of gene expression. Pre-mRNA splicing is an essential post-transcriptional process. Over 95% of multi-exon human genes undergo alternative splicing to create diverse arrays of mRNAs from a single gene. Disturbance of splicing regulation is associated with many human diseases.

Materials and methods: A genome-wide ENU mutagenesis screen was carried out to identify novel male fertility regulators. An array of gene functional analyses was carried out to define the function(s) of genes identified through the ENU mutagenesis approach.

Results and discussion: We identified the RNA binding protein RBM5 as an essential splicing regulator in male germ cells. Male mice carrying a missense mutation (R263P) in the second RNA recognition motif (RRM2) of RBM5 were sterile due to defects in spermatogonia differentiation, meiosis progression and spermatid maturation, which ultimately led to azoospermia. In round spermatids, RBM5 interacted with several splicing factors and regulated the splicing of several target pre-mRNAs, which have been implicated in germ cell adhesion, spermatid head shaping, and acrosome and tail formation. In addition, RBM5 dysfunction resulted in a significant reduction of spermatogonial progenitor cells and only 27% of those that entered meiosis successfully made the conversion to round spermatids. These findings suggest a role for RBM5 in spermatogonia differentiation and meiosis progression. In summary, our study demonstrates that RBM5 is a critical splicing regulator in male germ cells and is absolutely required for the correct progression of spermatogenesis and male fertility.