<P> The neural tube patterns along the dorsal - ventral axis to establish defined compartments of neural progenitor cells that lead to distinct classes of neurons . According to the French flag model of morphogenesis , this patterning occurs early in development and results from the activity of several secreted signaling molecules . Sonic hedgehog ( Shh ) is a key player in patterning the ventral axis , while bone morphogenic proteins ( BMPs ) and Wnt family members play an important role in patterning the dorsal axis . Other factors shown to provide positional information to the neural progenitor cells include fibroblast growth factors ( FGFs ) and retinoic acid . Retinoic acid is required ventrally along with Shh to induce Pax6 and Olig2 during differentiation of motor neurons . </P>
what is the function of the proteins secreted by cells of the ventral midline of the spinal cord
patterning the ventral axis