Expression of calmodulin in Drosophila is highly regulated in a stage- and tissue-specific manner.

The expression of the Drosophila calmodulin (CAM) gene is surprisingly complex. The nervous system, which shows intense transcription in embryogenesis, contains no detectable transcripts at the end of larval life, but becomes transcriptionally active again at pupariation. The gut shows high levels of expression throughout the life cycle, except during pupal reorganization. In contrast, CAM expression in the thoracic muscles drops significantly on transition from pupal to adult life. In the testis, transcription is strongly up-regulated prior to meiosis. Growing cells show lower transcript levels than most differentiated tissues and in general, cells with intense exocytotic or endocytotic activity show the highest mRNA levels.