Neuronal expression of a Caenorhabditis elegans elav-like gene and the effect of its ectopic expression

We examined the expression of a Caenorhabditis elegans (C. elegans) elav-like gene, which we designated elr-1. The elr-1 gene encodes a predicted 456-amino-acid protein containing three putative RNA-binding domains and belongs to the ELAV family, which is functionally involved in neuronal differentiation. Northern blot analysis suggested that the levels of elr-1 mRNA are regulated developmentally. A elr-1::gfp reporter gene under the control of the elr-1 promoter was expressed specifically in the ring ganglia near the nerve ring, the ventral nerve cord (VNC), and the pre-anal and lumbar ganglia. In the VNC, GFP-positive cells were shown to be acetylcholine-producing motor neurons which increased in number as development proceeded, suggesting that elr-1 is expressed in mature neurons. Ectopic expression of ELR-1 protein at the L4 larval and adult stages, but not earlier stages, caused irreversible death, accompanied by uncoordinated movement (Unc), clear (Clr), and egg-laying defective (Egl) phenotypes, which are often observed in mutants with neuronal defects. These results suggest that ELR-1 may have important functions in specific mature neurons in C. elegans.