Retinoic acid induces expression of HOXD3 in neuroblastoma cells (Zha et al. 2012) and mouse embryos but it is unknown if the effect is direct or indirect. In mouse embryos the retinoid receptor Rarb is not responsible for the inducibility. As inferred from mouse embryos HOXD3 is expressed in rhombomeres 5, 6, and 7 (r5-7). As inferred from mouse Hoxd3, activation of HOXD3 chromatin is associated with loss of methylation at lysine-27 of histone H3 (H3K27), loss of PRC2, and gain of methylation at H3K4.