Mice deficient for RNA‐binding protein brunol1 show reduction of spermatogenesis but are fertile

RNA-binding proteins are involved in post-transcriptional processes like mRNA stabilization, alternative splicing, and transport. Brunol1 is a novel mouse gene related to elav/Bruno family of genes encoding for RNA-binding proteins. We report here the expression and functional analysis of murine Brunol1. Expression analysis of Brunol1 during embryogenesis by RT-PCR showed that Brunol1 expression starts at 9.5 dpc and continues to the later stages of embryonic development. In adult mice, the Brunol1 expression is restricted to brain and testis. We also analyzed the Brunol1 expression in testes of different mutants with spermatogenesis defects: W/W(V), Tfm/y, Leyl(-/-), olt/olt, and qk/qk. Brunol1 transcript was detectable in Leyl(-/-), olt/olt, and qk/qk mutant but not in W/W(V) and Tfm/y mutants. We also showed by transfection of a fusion protein of green fluorescent protein and Brunol1 protein into NIH3T3 cells, that Brunol1 is localized in cytoplasm and nucleus. In order to elucidate the function of the Brunol1 protein in spermatogenesis, we disrupted the Brunol1 locus in mouse by homologous recombination, which resulted in a complete loss of the Brunol1 transcript. Male and female Brunol1(+/-) and Brunol1(-/-) mice from genetic backgrounds C57BL/6J x 129/Sv hybrid and 129X1/SvJ when inbred exhibited normal phenotype and are fertile, although the number and motility of sperms are significantly reduced. An intensive phenotypic analysis showed no gross abnormalities in testis morphology. Collectively our results demonstrate that Brunol1 might be nonessential protein for mouse embryonic development and spermatogenesis.