Drosophila RecQ5 is involved in proper progression of early spermatogenesis

RecQ5, a member of the conserved RecQ DNA helicase family, is required for the maintenance of genome stability. The human RECQL5 gene is expressed ubiquitously in almost all tissues, with strong expression in the testes (Shimamoto et al., 2000). However, it remains to be elucidated in which cells RecQ5 is expressed and how RecQ5 functions in the testes. In this present study we analyzed the expression of RecQ5 in Drosophila testes. The RecQ5 protein was specifically expressed in germline cells in larval, pupal, and adult testes. Drosophila RecQ5 was localized in nuclei of male germline stem cells, spermatogoniablasts, spermatogonia, and early spermatocytes. As growth of the early spermatocyte proceeded, the amount of RecQ5 increased in the nuclei. However, before maturation of the spermatocyte, the level of RecQ5 declined. Thus, RecQ5 expression was regulated. Furthermore, we compared recq5 mutant testes with the wild-type ones. The most conspicuous alterations were swelling of the apical region of and an increase in the number of spermatocytes in the recq5 testis, suggesting a relative accumulation of spermatocytes in the recq5 mutant testes. Therefore, Drosophila RecQ5 may contribute to the proper progression from germline stem cells to spermatocytes for maintenance of genome stability.