KLINGON, A NOVEL MEMBER OF THE DROSOPHILA IMMUNOGLOBULIN SUPERFAMILY,IS REQUIRED FOR THE DEVELOPMENT OF THE R7 PHOTORECEPTOR NEURON

klingon is a member of the Immunoglobulin superfamily and is expressed in a restricted pattern of neurons during embryonic neurogenesis and in the R7 photoreceptor precursor throughout its development, Starting from the H214 enhancer trap line, we identified a transcription unit, klingon, that encodes a putative protein of 528 amino acids and conta ins three C2-type Immunoglobulin-like domains followed by one fibronec tin type III repeat. When Klingon is expressed in S2 tissue culture ce lls, it is associated with the cell membrane by a glycosyl-phosphatidy linositol linkage and can mediate hemophilic adhesion, Genetic analysi s has revealed that klingon is an essential gene that participates in the development of the R7 neuron, Ectopic expression of klingon in all neurons in a sevenless background can alter the position of the R8 rh abdomere.