Cloning and characterization of peter pan, a novel Drosophila gene required for larval growth

We identified a new Drosophila gene, peter pan (ppan), in a screen for larv al growth-defective mutants, ppan mutant larvae do not grow and show minima l DNA replication but can survive until well after their heterozygotic sibl ings have pupariated. We cloned the ppan gene by P-element plasmid rescue. ppan belongs to a highly conserved gene family that includes Saccharomyces cerevisiae SSF1 and SSF2, as well as Schizosaccharomyces pombe, Arabidopsis , Caenorhabditis elegans, mouse, and human homologues. Deletion of both SSF 1 and SSF2 in yeast is lethal, and depletion of the gene products causes ce ll division arrest. Mosaic analysis of ppan mutant clones in Drosophila ima ginal disks and ovaries demonstrates that ppan is cell autonomous and requi red for normal mitotic growth but is not absolutely required for general bi osynthesis or DNA replication. Overexpression of the wild-type gene causes cell death and disrupts the normal development of adult structures. The ppa n gene family appears to have an essential and evolutionarily conserved rol e in cell growth.