Analysis of Drosophila ssp4

CAMSAP 1 is a spectrin associated, Calmodulin regulated protein that is a member of a large ubiquitous family of cytoskeletal proteins in the animal kingdom, defined by a novel C-terminal domain, the CKK domain. The role of the CAMSAP proteins is unknown but studies using rat PC12 cells have shown that CAMSAP1 plays a key role in neurite outgrowth. It has been shown to colocalise with microtubules in cultured cells and binds to microtubules in vitro via the CKK domain. The CAMSAP family member in the fruit fly Drosophila melanogastor is encoded by the gene short spindles4 (ssp4). Little is known about this gene but a role in microtubule dynamics has been shown in cultured cells.

I have interrogated bioinformatics databases and compared Ssp4 with Human CAMSAP proteins and found many similarities, and some differences, between the proteins. Using in situ hybridisation I show that ssp4 transcripts are expressed in the gut, head and central nervous system during embryogenesis and an antibody that recognises the Ssp4 C-terminus reveals expression throughout the development of the gut and nervous system, and in a discrete population of cells in the head.

I have investigated the effects of two independent P-element induced mutant alleles of ssp4 and show that mutant flies die in late embryonic or early larval stages. Disruptions to the locus do not seem to affect the nervous system but mutants were found to have aberrant head involution. I present preliminary evidence that suggests this defect may be the result of reduced apoptosis in the embryo

Head involution is a complex process, dependent upon co-ordinated changes to cell shape and the movement of groups of cells from different origins. As Ssp4 is a multidomain cytoskeletal protein that is required for embryonic development, it may play a role in processes that are common to these morphogenetic events.