No Neurotrophins Needed

Abstract

Adult mammalian olfactory neurons can regenerate, but are the mechanisms at work in these mature neurons the same as those that regulate olfactory neuron proliferation and differentiation during development? Nef et al. report that the neurotrophins and their cognate Trk receptors that have been implicated in the regenerative process are not at work in the developing mouse olfactory system. The authors analyzed mice that did not express TrkA, TrkB, or TrkC, or the neurotrophins NT3 and BDNF. Although the olfactory epithelium and olfactory bulb of wild-type mice did show expression of some Trk receptors and neurotrophins at birth, their absence in mutant mice did not affect nasal cavity or olfactory bulb development at this time, nor did it alter axonal projections from the former to the latter. All the mutant mice do die at early postnatal ages. Hence, neurotrophin signaling is critical to the proliferation of mature neurons, but not to the proliferation and development of embryonic neurons. S. Nef, M. E. Lush, T. E. Shipman, L. F. Parada, Neurotrophins are not required for normal embryonic development of olfactory neurons. Dev. Biol. 234 , 80-92 (2001). [Online Journal]