RBM5 Is a Male Germ Cell Splicing Factor and Is Required for Spermatid Differentiation and Male Fertility

Abstract

Alternative splicing of precursor messenger RNA (pre-mRNA) is common in mammalian cells and enables the production of multiple gene products from a single gene, thus increasing transcriptome and proteome diversity. Disturbance of splicing regulation is associated with many human diseases; however, key splicing factors that control tissue-specific alternative splicing remain largely undefined. In an unbiased genetic screen for essential male fertility genes in the mouse, we identified the RNA binding protein RBM5 (RNA binding motif 5) as an essential regulator of haploid male germ cell pre-mRNA splicing and fertility. Mice carrying a missense mutation (R263P) in the second RNA recognition motif (RRM) of RBM5 exhibited spermatid differentiation arrest, germ cell sloughing and apoptosis, which ultimately led to azoospermia (no sperm in the ejaculate) and male sterility. Molecular modelling suggested that the R263P mutation resulted in compromised mRNA binding. Within the adult mouse testis, RBM5 localises to somatic and germ cells including spermatogonia, spermatocytes and round spermatids. Through the use of RNA pull down coupled with microarrays, we identified 11 round spermatid-expressed mRNAs as putative RBM5 targets. Importantly, the R263P mutation affected pre-mRNA splicing and resulted in a shift in the isoform ratios, or the production of novel spliced transcripts, of most targets. Microarray analysis of isolated round spermatids suggests that altered splicing of RBM5 target pre-mRNAs affected expression of genes in several pathways, including those implicated in germ cell adhesion, spermatid head shaping, and acrosome and tail formation. In summary, our findings reveal a critical role for RBM5 as a pre-mRNA splicing regulator in round spermatids and male fertility. Our findings also suggest that the second RRM of RBM5 is pivotal for appropriate pre-mRNA splicing.

RBM5 reduces small cell lung cancer growth, increases cisplatin sensitivity and regulates key transformation-associated pathways

“…Gene sets with FDR at or below 10% in control vs. C4 are presented in Table 1, along with their FDR in control vs. T2. Interestingly, many differentially expressed gene sets are important to development, which validates our experimental findings, as RBM5 was recently shown to be involved in myogenesis, spermatogenesis and neuronal development (Fushimi et al, 2008; Loiselle and Sutherland, 2014; O'Bryan et al, 2013). Furthermore, apoptosis and TNFα signaling, both pathways RBM5 has been previously associated with in Jurkat T lymphoblastoid cells (Rintala-Maki and Sutherland, 2004; Sutherland et al, 2000) and MCF-7 cells (Rintala-Maki et al, 2004) were altered in T2 and C4.…”

Unmasking alternative splicing inside protein-coding exons defines exitrons and their role in proteome plasticity

“…SUA, a homolog of the mammalian splicing factor RBM5 (Bonnal et al 2008;Sugliani et al 2010;O'Bryan et al 2013), is responsible for the splicing inhibition of a cryptic intron in the ABI3 gene (Sugliani et al 2010). This cryptic intron is an internal part of a protein-coding exon; thus it qualifies as an exitron.…”

RBM-5 modulates U2AF large subunit-dependent alternative splicing inC. elegans

“…It is also required for spermatid differentiation and male fertility probably by affecting spermatid RNA splicing [57]. C. elegans rbm-5 is primarily expressed in neurons and not essential for survival or fertility.…”