Loss of G9a does not phenocopy the requirement for Prdm12 in the development of the nociceptive neuron lineage

Prdm12 is an epigenetic regulator expressed in developing and mature nociceptive neurons, playing a key role in their specification during neurogenesis and modulating pain sensation at adulthood. In vitro studies suggested that Prdm12 recruits the methyltransferase G9a through its zinc finger domains to regulate target gene expression, but how Prdm12 interacts with G9a and whether G9a plays a role in Prdm12s functional properties in sensory ganglia remain unknown. Here we report that the SET domain of G9a is necessary and sufficient for the interaction with Prdm12. We show that Prdm12 is co-expressed with G9a in dorsal root ganglia during early murine development. To address the role of G9a in somatosensory neurogenesis and test the hypothesis that it may function as a mediator of Prdm12s function during somatosensory neurogenesis, we conditionally inactivated it in neural crest using a Wnt1-Cre transgenic mouse line. We found that G9a ablation in neural crest does not lead to dorsal root ganglia hypoplasia due to the loss of somatic nociceptive neurons nor to the ectopic expression of the visceral determinant Phox2b as observed upon Prdm12 ablation. Together, our results confirm Prdm12s ability to interact with G9a and reveal that this interaction is however not instrumental for its developmental function during nociceptive neuron development.