Survival of neurons is dependent on neurotrophins both in vitro and in vivo. In the absence of these growth factors, the neurons undergo apoptosis. Apoptosis occurs early in neurogenesis before target-derived growth factors are present. Díaz et al. demonstrate that, in developing chick retina, survival of the neuroretinal cells is dependent on insulin. Blockade of insulin signaling with antibodies to proinsulin or the insulin receptor in ovo increased the number of apoptotic cells. Embryonic retinas in culture exhibited the same dependence on insulin for survival and survival correlated with insulin-stimulated phosphorylation of Akt. Thus, the neurotrophic actions of insulin may be mediated by the Akt survival pathway.
Díaz, B., Serna, J., De Pablo, F., and de la Rosa, E.J. (2000) In vivo regulation of cell death by embryonic (pro)insulin and the insulin receptor during early retinal neurogenesis. Development 127: 1641-1649. [Online Journal]