Activation of Hypodermal Differentiation in the Caenorhabditis elegans Embryo by GATA Transcription Factors ELT-1 and ELT-3

Abstract

The Caenorhabditis elegans GATA transcription factor genes elt-1 and elt-3 are expressed in the embryonic hypodermis (also called the epidermis). elt-1 is expressed in precursor cells and is essential for the production of most hypodermal cells (22). elt-3 is expressed in all of the major hypodermal cells except the lateral seam cells, and expression is initiated immediately after the terminal division of precursor lineages (13). Although this expression pattern suggests a role for ELT-3 in hypodermal development, no functional studies have yet been performed. In the present paper, we show that either elt-3 or elt-1 is sufficient, when force expressed in early embryonic blastomeres, to activate a program of hypodermal differentiation even in blastomeres that are not hypodermal precursors in wild-type embryos. We have deleted the elt-3gene and shown that ELT-3 is not essential for either hypodermal cell differentiation or the viability of the organism. We showed that ELT-3 can activate hypodermal gene expression in the absence of ELT-1 and that, conversely, ELT-1 can activate hypodermal gene expression in the absence of ELT-3. Overall, the combined results of the mutant phenotypes, initial expression times, and our forced-expression experiments suggest that ELT-3 acts downstream of ELT-1 in a redundant pathway controlling hypodermal cell differentiation.

ACKNOWLEDGMENTS

We thank J. Culotti (Toronto, Ontario, Canada) for strains NW1122 and NW1129, Axys Pharmaceuticals (San Francisco, Calif.) for strain NS3239, Andrew Fire (Baltimore, Md.) for providing convenient reporter vectors, Barbara Page (Seattle, Wash.) for strain J1129, Michel Labouesse (Strasbourg, France) for the LIN-26 antibody, R. Waterson (St. Louis, Mo.) for the MH27 antibody, Iain Johnstone (Glasgow, United Kingdom) for strain IA105, and Kyunghee Koh and Joel Rothman (Santa Barbara, Calif.) for generously providing information prior to publication. Particular thanks are due to Tetsunari Fukushige (Calgary, Alberta, Canada) for providing strains JM53 through JM60. Several strains in this work were supplied by the Caenorhabditis Genetics Centre, which is funded by the NIH Centre for Research Resources.

This work was funded by the Wellcome Trust by virtue of a Wellcome Trust Prize Traveling Fellowship (J.G.) and by the Medical Research Council of Canada (J.D.M.). J.D.M. is a Medical Scientist of the Alberta Heritage Foundation for Medical Research.