Cover image

Cover The Myb-Muv B subunit Mip40 is expressed in spermatocytes and is part of a new testis-specific meitoic arrest complex in Drosophila. Shown here is a merged confocal image of whole testes from wild-type males labeled with BrdU, and stained with antibodies directed against Mip40 (red) and BrdU (green). DNA was stained with DAPI (blue). Mip40 is expressed in both the mitotic stage (yellow) and the spermatocyte stage (red) nuclei. Purification of Mip40 complexes from testis nuclear extracts identified Mip40 as part of a new complex (named tMAC) that contains the testis-specific proteins Aly, Comr, Topi, and Tomb, which are all involved in the meiotic cell cycle and differentiation programs required for sperm development. In the absence of Mip40, the spermatogonial cells continue to proliferate but do not differentiate beyond the premeiotic spermatocyte stages. (For details, see Beall et al., p. 904.)