Pc. Svendsen et Jd. Mcghee, THE C-ELEGANS NEURONALLY EXPRESSED HOMEOBOX GENE CEH-10 IS CLOSELY-RELATED TO GENES EXPRESSED IN THE VERTEBRATE EYE, Development, 121(5), 1995, pp. 1253-1262
We describe the homeobox gene ceh-10 from the nematode Caenorhabditis
elegans. The homeodomain of ceh-10 is closely related to the homeodoma
ins of two genes recently cloned from the vertebrate retina, Chx10 fro
m mice and Vsx-1 from goldfish. We show that the sequence conservation
extends well beyond the homeodomain and includes a region (named the
CVC domain) of roughly 60 amino acids immediately C-terminal to the ho
meodomain. As assayed in transgenic worms, the promoter region of ceh-
10 directs expression of a lacZ reporter gene to a small number of neu
rons. We draw a parallel between the bipolar cells of the inner nuclea
r layer of the vertebrate retina, which express Chx10 and Vsx-1, and a
n interneuron in C. elegans called AIY, which expresses ceh-10. AIY re
ceives synaptic input from a sensory cell, just as do bipolar cells of
the vertebrate retina. In C. elegans, the sensory cell AFD is not kno
wn to be photosensitive but is known to be thermosensitive; moreover,
a cell with similar position in the amphids of other nematodes has bee
n suggested indeed to be photosensitive. Our results emphasize the hig
hly conserved nature of sensory regulatory mechanisms and suggest one
way in which photosensitive organelles might have originated in evolut
ion.