A cluster of four genes selectively expressed in the male germ line of Drosophila melanogaster.

The gene Mst87F is exclusively expressed in the male germ line and is subject to translational regulation. The Mst87F mRNA is transcribed in the primary spermatocytes, stored for three days and then subsequently translated in the post-elongation period of spermiogenesis. Here we report on the isolation of a cluster of four small genes closely related in structure and function to Mst87F. These genes are located at polytene band 84D on the right arm of chromosome three and are named Mst84Da, Mst84Db, Mst84Dc and Mst84Dd. All four genes encode putative proteins composed primarily of a repetitive motif of cysteine-glycine-proline. The genes are exclusively expressed in the male germ line. The poly(A) tail of the Mst84D mRNAs increases in length at day three of pupal development, the time at which a similar change in Mst87F mRNA and translation has been shown to begin. In addition we have identified a conserved 12 base pair element within the 5' untranslated region (UTR) of each gene which is also found at an identical position in Mst87F and which has been demonstrated to be the structural element for translational control of Mst87F expression (Schäfer et al., 1990 EMBO J. 9, 4519-4525). We have mapped the gene cluster to a small deletion associated with a rotund mutation at 84D. Although flies with a homozygous deletion of the cluster still produce motile sperm, electron microscopic examination revealed numerous malformations in the ultrastructure of the axoneme resulting in a drastic reduction of motile sperm.