The E3 ubiquitin ligase RNF220 maintains hindbrain <i>Hox</i> expression patterns through regulation of WDR5 stability.

Abstract

The spatial and temporal linear expression of <i>Hox</i> genes establishes a regional <i>Hox</i> code, which is crucial for the antero-posterior (A-P) patterning, segmentation, and neuronal circuit development of the hindbrain. RNF220, an E3 ubiquitin ligase, is widely involved in neural development via targeting of multiple substrates. Here, we found that the expression of <i>Hox</i> genes in the pons was markedly up-regulated at the late developmental stage (post-embryonic day E15.5) in <i>Rnf220^-/-</i> and <i>Rnf220^+/-</i> mouse embryos. Single-nucleus RNA sequencing (RNA-seq) analysis revealed different <i>Hox</i> de-repression profiles in different groups of neurons, including the pontine nuclei (PN). The <i>Hox</i> pattern was disrupted and the neural circuits were affected in the PN of <i>Rnf220^+/-</i> mice. We showed that this phenomenon was mediated by WDR5, a key component of the TrxG complex, which can be polyubiquitinated and degraded by RNF220. Intrauterine injection of WDR5 inhibitor (WDR5-IN-4) and genetic ablation of <i>Wdr5</i> in <i>Rnf220^+/-</i> mice largely recovered the de-repressed <i>Hox</i> expression pattern in the hindbrain. In P19 embryonal carcinoma cells, the retinoic acid-induced <i>Hox</i> expression was further stimulated by <i>Rnf220</i> knockdown, which can also be rescued by <i>Wdr5</i> knockdown. In short, our data suggest a new role of RNF220/WDR5 in <i>Hox</i> pattern maintenance and pons development in mice.