Graded expression of ceh-14 reporters in the hypodermis is induced by a gonadal signal

Caenorhabditis elegans, is the orthologue of the vertebrate Lhx3/Lhx4 genes . ceh-14 reporter constructs are expressed in several different cell types: head and tail neurons, spermatheca and hypodermis. An intriguing aspect of the hypodermal expression pattern is that it takes the form of a gradient which is strongest in the central body region in L4 to young adult hermaphr odites. Promoter deletion analyses revealed that important regulatory eleme nts for hypodermal expression are located within the transcribed region of ceh-14. Since a large part of the hypodermis is a syncytium, we hypothesize d that this expression is triggered in a non-cell-autonomous fashion, a pos sible source being the underlying gonad. In males, which have a different g onadal organisation, the ceh-14 reporter constructs are expressed in a grad ient that is strongest in the tail. By laser ablation of the gonadal precur sor cells we found that ceh-14 reporter construct expression is eliminated in the hermaphrodite hypodermis, suggesting that the gonad plays a role in the generation of the gradient. Several signaling pathways are known in the gonad and the vulva, thus we crossed the mutations lin-3, egl-17 and lin-1 2 with the ceh-14 reporter lines. However, the expression of the reporter c onstructs is not affected in these mutant backgrounds. This suggests that a nother, presently unknown, signal triggers the graded hypodermal expression .