Phosphorylation of the retinoic acid receptor RARγ2 is crucial for the neuronal differentiation of mouse embryonic stem cells

Abstract

Retinoic acid (RA) plays key roles in cell differentiation and growth arrest by activating nuclear receptors, RARs (α, β and γ), which are ligand dependent transcriptional factors. RARs are also phosphorylated in response to RA. Here we investigated the in vivo relevance of RARs phosphorylation during RA-induced neuronal differentiation of mouse embryonic stem (mES) cells. Using ES cells where the genes encoding each RAR subtype have been inactivated and stable rescue lines expressing RARs mutated in phosphor-acceptor sites, we show that RA-induced neuronal differentiation involves RARγ2 and requires RARγ2 phosphorylation. By gene expression profiling, we found that the phosphorylated form of RARγ2 regulates a small subset of genes through binding an unusual RA response element consisting of two direct repeats with a 7 base pair spacer. These new findings suggest an important role for RARγ phosphorylation during cell differentiation, and pave the way for further investigations during embryonic development.