HDAC1/2-mediated repression of Wnt receptor expression orients asymmetric division polarity in Caenorhabditis elegans.

Asymmetric cell division generates distinct daughter cells essential for tissue development, yet the mechanisms orienting division polarity within tissues remain incompletely understood. Here, we uncover a role for chromatin-mediated transcriptional repression in controlling polarity orientation during asymmetric division of Caenorhabditis elegans epidermal stem cells, known as the seam cells. Tissue-specific loss of the class I histone deacetylase hda-1, homologous to mammalian HDAC1/2, causes polarity reversals and reduces molecular asymmetry between daughter cells. Using Targeted DamID, we identify the Wnt receptors lin-17 (frizzled homologue) and cam-1 (Ror homologue) as key targets. Single-molecule fluorescence in situ hybridisation reveals opposing expression gradients along the body axis, with cam-1 enriched anteriorly and lin-17 posteriorly. In hda-1 mutants, both receptors are upregulated and differences between seam cells are flattened. Overexpression of either receptor alone is sufficient to reproduce the polarity reversals, while co-overexpression produces additive effects. The polarity phenotype is independent of the canonical NuRD and SIN3 complexes, suggesting that HDA-1 acts through an alternative mechanism. These findings link histone deacetylase activity to Wnt receptor expression and suggest that graded receptor expression may provide cues that orient asymmetric division polarity.