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#HesC

2 public questions tagged with this topic.

Sea Urchin -ll

HesC directly represses:

HesC is hairy and Enhancer-of-split family basic helix-loop-helix transcriptional repressor expressed broadly throughout early sea urchin embryo except in large micromeres where Pmar1 actively suppresses it. Its primary developmental role is keeping skeletogenic and signaling genes silent outside micromere lineage. Chromatin immunoprecipitation studies show HesC binds directly to cis-regulatory elements of Alx1, Tbr, Ets1 activators and Delta ligand gene, preventing their transcription in non-micromere cells. Removal of HesC by morpholino causes ectopic spiculogenesis throughout embryo. Thus direct molecular targets repressed by HesC include core skeletogenic transcription factors and Delta, restricting primary mesenchyme specification exclusively to vegetal pole.

Ref: Revilla-i-Domingo et al., PNAS 2007, HesC represses skeletogenic genes and Delta; Davidson Lab GRN.

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Sea urchin -lll

HesC expression represses:

HesC is global transcriptional repressor containing basic helix-loop-helix Orange domain expressed ubiquitously early in sea urchin. It binds E-boxes in promoters of micromere-specific genes including Delta ligand and skeletogenic transcription factors alx1, ets1, tbr, dri. Repression keeps Delta silent outside micromeres. In micromeres, Pmar1 represses hesC gene, derepressing targets and allowing Delta-Notch signaling. Therefore HesC expression represses Delta expression, ensuring spatially restricted signaling. Overexpression of HesC eliminates Delta and skeleton, while HesC morpholino knockdown causes ectopic Delta throughout embryo, confirming direct negative regulation rather than regulation of beta-catenin or micromere formation itself.

Ref: Davidson Lab, Sea Urchin GRN: HesC represses Delta expression non-micromere lineages double-negative gate.

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