elt-1 is a hypodermal GATA factor that is essential for the early specification of hypodermal cell fates Due to the early embryonic lethal phenotype of
elt-1 mutants little is known regarding the later functions of
elt-1 and consequently we are using RNAi to investigate this. A chromosomally integrated
elt-1::GFP reporter gene is expressed in most hypodermal cell precursors in early embryos but becomes restricted to lateral seam cells from the comma stage onwards. Post-embryonically, there is continued expression in seam cells and additional expression in the ventral nerve cord and cell bodies of the retro-pharyngeal ganglion. There is also expression in the sex muscles surrounding the vulva. When RNAi is applied to adults the most severe RNAi effect in the progeny phenocopies the
elt-1(
zu180) mutant but the less severely affected animals show a differential loss of lateral seam cells relative to the rest of the hypodermis.
elt-1 RNAi also represses
elt-3::GFP expression suggesting
elt-1 is required for the initiation of
elt-3 expression. When RNAi is applied post-embryonically, larvae appear to develop at a similar rate to wild type worms but become extremely sick within 3 hours after the L4-adult moult and rupture at the vulva. Examination of seam cell development shows that seam cells are progressively lost from the mid L4 stage onwards. Scanning electron microscopy and
col-19::GFP immunolocalisation shows that the adult cuticle lacks alae and, while the cuticle is broadly intact, there is some disruption of lateral cuticle organisation. Seam cells are still lost when
elt-1 RNAi is applied to
lin-29 mutants suggesting that terminal differentiation of lateral seam cells is not in itself the requirement for
elt-1 function. The RNAi phenotype appears to be suppressed in
ced-4 and to a lesser extent
ced-3 mutants suggesting that seam cells may be lost by apoptosis.
elt-1 RNAi applied post-embryonically also produces an unc phenotype in L1 to adult stages and an adult egl phenotype. Both these phenotypes are consistent with the
elt-1 expression pattern and suggests that
elt-1 has essential functions in multiple tissues.