Fig. 9

A Model for Evx Function in V0v cells. A possible model that would reconcile the different phenotypes of mouse and zebrafish Evx1 mutants. In this model, Dbx1 expression in P0 cells is required for the expression of Evx1 and Evx2 in V0v cells (for simplicity this interaction is not shown) and Dbx1 can also independently repress the V1 fate. In zebrafish, Dbx1 expression persists for a while in newly formed V0v cells. This may be sufficient for the V1 fate to be inhibited in post-mitotic V0v cells, even in the absence of Evx1 and Evx2, thereby revealing other functions of Evx transcription factors. This could explain why V0v cells still form in evx1;evx2 double mutants, but they express glycinergic rather than glutamatergic markers. In contrast, in mouse Dbx1 is expressed only in progenitor cells. Therefore, in newly formed V0v cells only Evx1 and Evx2 inhibit the V1 fate and in the absence of these transcription factors V0v cells transfate into V1 cells