A regulatory module controlling pharyngeal development and function in Caenorhabditis elegans

In Caenorhabditis elegans, the differentiation and morphogenesis of the foregut are controlled by several transcriptional regulators and cell signaling events, and by PHA-1, an essential cytoplasmic protein of unknown function. Previously we have shown that LIN-35 and UBC-18-ARI-1 contribute to the regulation of pha-1 and pharyngeal development through the Zn-finger protein SUP-35/ZTF-21. Here we characterize SUP-37/ZTF-12 as an additional component of the PHA-1 network regulating pharyngeal development. SUP-37 is encoded by four distinct splice isoforms, which contain up to seven C2H2 Zn-finger domains, and is localized to the nucleus, suggesting a role in transcription. Similar to sup-35, sup-37 loss-of-function mutations can suppress both LOF mutations in pha-1 as well as synthetic-lethal double mutants, including lin-35; ubc-18, which are defective in pharyngeal development. Genetic, molecular, and expression data further indicate that SUP-37 and SUP-35 may act at a common step to control pharyngeal morphogenesis, in part through the transcriptional regulation of pha-1. Moreover, we find that SUP-35 and SUP-37 effect pharyngeal development through a mechanism that can genetically bypass the requirement for pha-1 activity. Unlike SUP-35, SUP-37 expression is not regulated by either the LIN-35 or UBC-18-ARI-1 pathways. In addition, SUP-37 carries out two essential functions that are distinct from its role in regulating pharyngeal development with SUP-35. SUP-37 is required within a subset of pharyngeal muscle cells to facilitate coordinated rhythmic pumping and in the somatic gonad to promote ovulation. These latter observations suggest that SUP-37 may be required for the orchestrated contraction of muscle cells within several tissues.