P. Dufourcq and M. Victor contributed equally. Our lab is interested in chromatin remodeling activities in C. elegans development with a particular emphasis on histone acetylases and histone deacetylases. We showed previously that a histone acetylase, CBP-1, is essential for all non-neuronal cell differentiation in C. elegans embryogenesis. In endodermal cells, CBP-1 appears to promote their differentiation by antagonizing the repressive activity of a histone deacetylase gene,
hda-1 (1). Inhibition of
hda-1 expression by RNAi results in embryonic arrest at the comma stage, and the cause of this embryonic lethality is currently unclear. To understand the dynamic genetic interaction between
cbp-1 and
hda-1 in C. elegans development, we analyzed the zygotic function of
hda-1. To inhibit
hda-1 zygotic expression, we took advantage of the
rde-1 strain generated by the Mello lab. We find by RNAi experiment in the
rde-1 genetic background that loss of zygotic
hda-1 expression results in sterile animals that have abnormal somatic gonad tissues and a defect in germline development. The
hda-1 gene is located on chromosome V in a region where a previously isolated genetic mutant termed
gon-10 is mapped to. We find that
gon-10 mutants share many of the phenotypes displayed by the animals that lack zygotic
hda-1. We have sequenced the complete
hda-1 gene isolated from the homozygotic
gon-10 mutant (including its promoter and 3 untranslated regions) and have identified a single nucleotide change that alters a conserved amino acid near the catalytic domain of HDA-1. Using affinity-purified HDA-1 antibodies that we developed, we found
hda-1 expression to be virtually undetectable in these mutants. Thus, the finding of a point mutation in the
hda-1 gene coupled with a lack of
hda-1 expression in the
gon-10 mutant are highly suggestive that
gon-10 may be an
hda-1 mutant. To determine whether this is indeed the case, experiments are in progress to rescue the
gon-10 defects. Analysis and comparison of the phenotypes of the
gon-10 mutant and the
rde-1;
hda-1/RNAi animals will be presented. 1. Shi, Y., and Mello, C.C. (1998). Gen.& Dev. 12, 943-955.