HBS1L and male infertility: Here we demonstrate a novel and specific function of Hbs1 in spermatogenesis in Drosophila. Loss of function of Hbs1 causes defects in meiotic cell division and spermatid differentiation during spermatogenesis, leading to male infertility with no apparent defect in viability, and this revealed a male-specific germline function of Hbs1.