A Novel KH-Domain Protein Mediates Cell Adhesion Processes inDrosophila

Abstract

Adhesion of cells to one another and to extracellular matrices has major roles in morphogenetic processes during development. One important family of cell adhesion receptors are the integrins, which inDrosophilahave crucial functions in at least two adhesion-mediated developmental events: embryonic muscle attachment and adhesion of the wing epithelia. We have cloned and characterized a gene (struthio) that is expressed in embryonic mesodermal and muscle cells, including cardioblasts, and epidermal muscle attachment sites in a pattern that is reminiscent of the expression pattern of the PS integrins. Maternal and zygotic transcripts are produced by this gene and encode similar proteins with two alternative carboxy tails. Both proteins contain identical KH domains, a protein sequence motif that is found in numerous proteins that interact with RNA. Thestruthioprotein is highly homologous in a region including the KH domain to the mousequakingandC. elegans gld-1proteins, two developmentally important genes. Somatic homozygous clones of an embryonic lethal mutation in this gene (stru1A122) cause wing blisters and flight impairment, phenotypes which are associated with PS integrin subunit mutations. Thus, thestruthiogene encodes a putative RNA-binding protein that appears to regulate some aspects ofDrosophilaintegrin functioning.