A critical feature of the meiotic cell cycle is an extended G2 phase, termed meiotic prophase, during which many genes required for gamete differentiation are transcribed. The duration of meiotic prophase is controlled differently in males than in females. We will investigate mechanisms that regulate timing of the G2/M transition in males and coordinate meiotic cell cycle progression with the transcription program for spermatid differentiation using Drosophila as a model system. We will investigate two independent pathways that may regulate exit from meiotic prophase: 1) post-transcriptional delay in expression of cyclin B protein, and 2) mechanisms that link expression of boule to the transcriptional program for spermatid differentiation. The boule protein (a homolog of human Deleted Azoospermia) regulates translational of the cell cycle regulatory phosphatase twine-cdc25. We will test if translational repression or protein turnover regulate cyclin B and boule protein expression in primary spermatocytes, identify cis-actin sequences responsible, screen for possible translational regulators that bind crucial cis-acting sequences, and test their role in meiotic progression in vivo. We will identify candidates that might link expression of boule to the transcription program for spermatid differentiation by microarray analysis of testing mRNA from the Drosophila meiotic arrest mutants, which are defective in transcription of spermatid differentiation genes. To identify additional genes that might act to control meiotic cell cycle progression in males, we will identify transcripts co-regulated with cyclin B, twine, and boule in wild type and mutant testes by microarray analysis and test whether potential key regulators expressed in primary spermatocytes are required for meiotic cell cycle progression, cyclin B, boule or twine protein expression, or spermatid differentiation. Our findings will be enriched by comparison with mechanisms that control the G2/M transition in oocytes in the context of this center grant and suggest mechanisms and gene products to test for similar function during mammalian spermatogenesis.