An analysis of maleless and histone H4 acetylation in Drosophila melanogaster spermatogenesis.

Maleless (mle) is essential in Drosophila melanogaster males both in somatic cells and in germ cells. In somatic cells mle is necessary for X-chromosome dosage compensation. The role of mle in the germline is unknown. We have analyzed the expression pattern and localization of MLE, the other MSLs and acetylated isoforms of histone H4 in male germ cells to address whether dosage compensation and/or X inactivation occur in the Drosophila germline. We observed that MLE is the only MSL expressed in the male germ cells and it is not localized to the X chromosome. We conclude that in the germline mle is not involved in chromosomal dosage compensation but may be involved in post-transcriptional gene regulation. We also observed that the acetylation pattern of histone H4 is very dynamic during spermatogenesis. While the pattern is not compatible with dosage compensation or X inactivation, it is consistent with all premeiotic chromosomes being in an active configuration that is replaced in post-meiotic stages with an inactive chromatin constitution.