The GATA-factor elt-2 is essential for formation of the Caenorhabditis elegans intestine

The Caenorhabditis elegans elt-2 gene encodes a single-finger GATA factor, previously cloned by virtue of its binding to a tandem pair of GATA sites that control the gut-specific ges-l esterase gene. In the present paper, we show that elt-2 expression is completely gut specific, beginning when the embryonic gut has only two cells (one cell cycle prior to ges-l expression) and continuing in every cell of the gut throughout the life of the worm. When elt-2 is expressed ectopically using a transgenic heat-shock construct, the endogenous ges-l gene is now expressed in most if not all cells of the embryo; several other gut markers (including a transgenic elt-2-promoter::lacZ reporter construct designed to test for elt-2 autoregulation) are also expressed ectopically in the same experiment. These effects are specific in that two other C. elegans GATA factors (elt-1 and elt-3) do not cause ectopic gut gene expression. An imprecise transposon excision was identified that removes the entire elt-2 coding region. Homozygous elt-2 null mutants die at the L1 larval stage with an apparent malformation or degeneration of gut cells. Although the loss of elt-2 function has major consequences for later gut morphogenesis and function, mutant embryos still express ges-1. We suggest that elt-2 is part of a redundant network of genes that controls embryonic gut development; other factors may be able to compensate for elt-2 loss in the earlier stages of gut development but not in later stages. We discuss whether elements of this regulatory network may be conserved in all metazoa. (C) 1998 Academic Press.