lola encodes a putative transcription factor required for axon growth and guidance in Drosophila

Mutations in the gene longitudinals lacking (lola) lead to defects in the development of axon tracts in the Drosophila embryonic central nervous system. We now show that lola mutations also cause defects of axon growth and guidance in the peripheral nervous system, and causes a particular cluster of embryonic sense organs (lch5) to be oriented improperly. Axonal aberrations caused by lola are similar to those caused by mutations of three other genes, logo, Notch and Delta, raising the possibility that lola works in the same genetic pathway as do these other molecules. The lola gene encodes at least two nuclear protein products, apparently by differential RNA splicing. The predicted proteins contain an amino-terminal motif similar to that recently described for a family of transcription factors, including the products of the Drosophila genes tramtrack and the Broad Complex. Like Ttk and BR-C, one of the two characterized products of the lola locus bears sequences similar to the zinc-finger motif, but the other (neuronal) form of the protein has no recognizable DNA-binding motif.