Our current model is that the GATA-factor ELT-2 is the predominant transcription factor controlling gene expression in the C. elegans intestine following endoderm specification. We are interested if other transcription factors besides ELT-2 have critical roles in the intestine. We have identified roughly 300 different transcription factors in SAGE libraries prepared from FACS-sorted cells of the embryonic intestine. The loss of function of 32 of these transcription factors results in embryonic lethal or larval lethal phenotypes, but their specific requirements in the intestine are difficult to ascertain because these genes may also be expressed in non-intestinal tissues. In order to examine their intestinal function, we used a strain of worms that is RNAi sensitive only in the intestine (OLB11, kindly provided by Olaf Bossinger). OLB11 worms are deficient in RNAi due to a mutation in the
rde-1 gene, but have intestinal RNAi rescued by an integrated array containing
rde-1 cDNA controlled by the intestinal-specific promoter of the
elt-2 gene. Control experiments show the strain behaves as expected: embryos and larvae of injected mothers are completely resistant to RNAi effects of genes expressed exclusively or predominantly outside of the intestine but are sensitive to RNAi against genes expressed exclusively or predominantly in the intestine. Double stranded RNA corresponding to each of the 32 intestinally expressed transcription factors were injected into OLB11 worms and their progeny were scored for viability and growth rates. Intestinal-specific RNAi against only two transcription factors,
elt-2 and
sbp-1, results in larval lethality, with injected progeny arresting as L1 larvae, matching the RNAi effects of these genes in wild type worms. Intestinal RNAi against four genes, F57B10.1 (
let-607), C16A3.4, F23B12.7 and
dve-1 causes a slow growth phenotype; however, these worms develop into fertile adults with no apparent defects in the structure of the intestine. Intestinal RNAi against the other 26 transcription factors does not affect viability or growth rates. Currently we are using the OLB11 worms to assess the intestinal function of some of these transcription factors in regulating aging. So far we have determined loss of intestinal
skn-1 (RNAi performed by feeding) results in a shortened life span, and we are presently looking at other genes, such as
pha-4, in this process.