Androcam, a Drosophila calmodulin-related protein, is expressed specifically in the testis and decorates loop kl-3 of the Y chromosome

The Drosophila genome encodes a protein that is 68% identical to Drosophila calmodulin (Cam). We show here that this Cam-related gene is specifically expressed in the germ-line of the testis, leading to the name Androcam (Aca m). Early in spermatogenesis Acam accumulates on one of the chromatin loops of the Y chromosome, kl-3. This association with kl-3 may indicate an RNA processing-related role for Acam and/or could reflect an unusual storage/as sembly function hypothesized for the Y loops. After meiosis Acam is detecta ble in developing sperm tail cytoplasm, where at least some of the protein is not tightly associated with tubulin. Late in spermiogenesis, some Acam s taining overlaps the periphery of the investment cones, actin-containing st ructures hypothesized to support the motor function for cytoplasmic strippi ng of the tail. Acam cannot be detected in mature sperm by immunolocalizati on, but immunoblotting established that Acam is present in sperm stored in mated females, suggesting epitope masking during final maturation. Proteins more related to Acam than Cam are present in the testes of other Drosophil a species and a mammalian species, the mouse. (C) 2000 Elsevier Science Ire land Ltd. All rights reserved.