Imp (IGF-II mRNA-binding protein) is expressed during spermatogenesis in Drosophila melanogaster.

Drosophila spermatogenesis results in the production of sixty‑four ~2-mm spermatozoa from an individual founder cell. Little is known, however, about the elongation of spermatids to such an extraordinary length. In a partial screen of a GFP-tagged protein trap collection, four insertions were uncovered that exhibit expression toward the tail ends of spermatid cysts and within the apical tip of the testis, suggesting that these protein traps may represent genes involved in spermatid elongation and pre-meiotic spermatogenesis, respectively.