Two members of a novel class of genes have been identified in Drosophila that encode putative transmembrane proteins with six leucine-rich repeats and a single immunoglobulin loop. These two molecules, Kekkon1 and Kekkon2, show striking conservation in their extracellular domains and have large and more divergent intracellular regions. The homology of the two kek genes to other known adhesion and signaling molecules, together with their expression patterns, suggests that both genes are involved in interactions at the cell surface. Genetic analysis reveals that deletion of the kek1 gene causes no obvious developmental defects. Its expression is correlated with aspects of segmentation and neurogenesis, including the formation of neuroblasts, sensory mother cells, and peripheral nerves.
Mutants are also defective in muscle organization.
The transcript of the LRR47 gene is detected in adult females and in early embryogenesis. It is not found in adult males and is only present at low levels in embryos after 6 h of development. In Western blot experiments, a protein of approx. 47 kDa, which is expressed in a similar developmental profile and purifies in peripheral membrane protein extracts, is detected by an antibody specific for LRR47. Upon reaching the target region, neuronal growth cones transiently search through them and form synaptic connections with only a subset of these potential targets.