EN1 transcribed and synthesized in V1 (pink) has a cell‐autonomous activity in these cells contributing to the expression of several V1 factors (FA, FB, …) that may signal to MNs (yellow) and other cell types (blue). All the latter F factors do not necessarily require EN1 activity. EN1 after its secretion by V1 interneurons is preferentially internalized by MNs (fat red arrow) and less by other cell types (thin red arrow), if at all. These other cell types express other F Factors (FX, FY, …) which are secreted and are, or not, under non‐cell‐autonomous EN1 activity. As a result, MNs experience the signaling activity of F factors (possibly EN1‐dependent as in the scheme, but not necessarily so) and internalize EN1. Following internalization, EN1 can work alone or in synergy with the F factors to regulate transcription, translation, and chromatin conformation within MNs.