A new study reveals the keys to a crucial mechanism in the evolution of vertebrates. Decades of work with birds and rodents have shown that in the early stage of embryonic development, the peripheral nervous system neurons are produced in greater quantities than is needed to adjust their numbers after the size of the organ or tissue they innervate.

The team, comprised of researchers from different countries, has confirmed that only the cells better adapted “survive, or what is the same, only those with the action of two neurotrophic protein, called nerve growth factor (NGF) and neurotrophin-3 (NT3), get around this selection.

The research, which will be posted in the next issue of the journal Nature, noted in embryonic stem cells in mouse embryos that the key lies in two of the NGF and NT3 receptors in particular in the tyrosine kinase TrkA and TrkC, which induce the death of neurons in the absence of NGF and NT3.

“However, we found that another receptor, TrkB, mostly in the central nervous system, does not induce neuronal death,” says Jose Maria Frade, one of the study’s authors and expert at the Cajal Institute (CSIC).

Duplicate recipients

The scientists propose that the classical neurotrophic mechanism promoted by NGF and NT3 in the peripheral nervous system arises in the evolution of vertebrates in a manner similar to the diversification of Trk receptors. In the direct ancestors of vertebrates reveals the existence of a single Trk receptor.

“It is most likely that during evolution there has been a doubling, giving rise to the ancestor of TrkB and TrkA / TrkC,” said Frade. The latter, probably capable of promoting neuronal death in the first vertebrates, has been doubled again to cause the receptors TrkA and TrkC, an evolutionary process parallel with the acquisition of new types of neurons in the peripheral nervous system. “

In addition, the study suggests an explanation for the different forecasts associated with tumors derived from neural crest, particularly neuroblastoma, the most common extracranial solid cancer in children. “It is known that neuroblastomas expressing TrkA or TrkC have a better prognosis than those expressing TrkB, probably due to the effect that we have demonstrated,” concluded Frade.

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Citation: V. Nikoletopoulou, H. Lickert, JM Frade, C. Rencurel, P. Giallonardo, L. Zhang, M. Bibel, Y. Barde. “TrkC neurotrophin receptors TrkA and TrkB Whereas cause neuronal death does not”. Nature, September 2, 2010.

Source: SINC