“…Except for the known effect of the notochord on the floor plate of the neural tube through the secretion of shh (Echelard et al, 1993;Martí et al, 1995), several reports indicate that the neuroepithelium shows autonomous behavior, which is exerted by the autocrine and/or paracrine secretion of diffusible molecules (Vaccarino et al, 1999b). Certain growth factors have been implicated in the control of neuroepithelial stem cell proliferation, neurogenesis, and gliogenesis, e.g., FGF2 and EGF, which may be involved in the control of replication and neurogenesis at early developmental stages (Gensburger et al, 1987;Murphy et al, 1990;Kilpatrick and Bartlet, 1993;Tropepe et al, 1999;Vaccarino et al, 1999aVaccarino et al, , 1999bPanchision and McKay, 2002;Rajan et al, 2003).…”