The forkhead box A (FoxA) transcription factor plays a critical role in endoderm development in all animals examined to date (1,2). Its C. elegans orthologue,
pha-4, is the organ selector gene for pharynx development, and tight regulation of temporal, spatial and degree of
pha-4 activity is essential for successful pharynx formation (3,4). Therefore, identification of molecules that genetically interact with
pha-4 will inform us of additional regulatory mechanisms that control pharyngeal cell fate specification and differentiation. To this end, we performed EMS mutagenesis and RNAi screening to look for
pha-4 suppressors and enhancers. For the screens, we generated and used
pha-4 (ts) strains that rapidly degrade
pha-4 transcripts at restrictive temperature through NMD pathway and thus fail to grow to adulthood. Our screening identified 250 genes, including
ruvb-1, that enabled
pha-4 (ts) animals to survive at restrictive temperature (5,6). Conversely, we undertook a
pha-4 RNAi suppression assay to verify the positive hits from the initial screens and to expand the repertoire of potential suppressors and enhancers in candidate pathways; weak
pha-4 RNAi treatment causes defects in pharynx development, which leads to lethality in approximately 80% of wild-type worms. We found that some mutants are able to enhance or suppress the lethality associated with a partial loss of
pha-4. The candidate genes for
pha-4 enhancers and suppressors will be further investigated to determine how they interact with
pha-4 and modulate pharynx development.
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4. J. Gaudet, S. E. Mango, Science 295, 821 (2002).
5. D. L. Updike, S. E. Mango, Genetics 177, 819 (2007).
6. K. L. Sheaffer, D. L. Updike, S. E. Mango, Curr. Biol. 18, 1355 (2008).