Molecular cloning of the pawn locus from Drosophila melanogaster

Alleles of pawn have numerous morphological phenotypes, including dark deposits on the eye, truncated bristles, and semilethality. The gene encoding the pawn locus was cloned. The Pawn protein is predicted to be a large cell adhesion molecule with a single transmembrane domain, a short cytoplasmic tail and two extracellular epidermal growth factor (EGF)-like repeats. The identity of the pawn gene product was confirmed by sequencing the defects in four different pawn alleles. Analysis of cDNAs showed a complex genomic structure with two 5' untranslated exons and developmental-specific RNA splicing. The gene is expressed throughout development with highest expression found in the late embryonic and larval stages.