RESCUE OF CAENORHABDITIS-ELEGANS PHARYNGEAL DEVELOPMENT BY A VERTEBRATE HEART SPECIFICATION GENE

Development of pharyngeal muscle in nematodes and cardiac muscle in ve rtebrates and insects involves the related homeobox genes ceh-22, nkx2 .5, and tinman, respectively, To determine whether the nematode and ve rtebrate genes perform similar functions, we examined activity of the zebrafish nkx2.5 gene in transgenic Caenorhabditis elegans. Here, we r eport that ectopic expression of nkx2.5 in C. elegans body wail muscle can directly activate expression of both the endogenous myo-2 gene, a ceh-22 target normally expressed only ire pharyngeal muscle, and a sy nthetic reporter construct controlled by a multimerized CEH-22 binding site. nkx2.5 also efficiently rescues a ceh-22 mutant when expressed in pharyngeal muscle. Together, these results indicate that nkx2.5 and ceh-22 provide a single conserved molecular function, Further, they s uggest that an evolutionarily conserved mechanism underlies heart deve lopment in vertebrates and insects and pharyngeal development in nemat odes.