From neurons to brains; origin of neurons (Introduction)

by David Turell , Monday, November 23, 2015, 15:43 (3076 days ago) @ David Turell

The lowly hydra may hold the explanation. Their epithelial cells can have a neuron-like function:-http://phys.org/news/2015-11-hydra-genetic.html-"Champion of regeneration, the freshwater polyp Hydra is capable of reforming a complete individual from any fragment of its body. It is even able to remain alive when all its neurons have disappeared. Researcher the University of Geneva (UNIGE), Switzerland, have discovered how: cells of the epithelial type modify their genetic program by overexpressing a series of genes, among which some are involved in diverse nervous functions. Studying Hydra cellular plasticity may thus influence research in the context of neurodegenerative diseases. - ***-"Epithelial cells do not possess typical neuronal functions. However, Hydra's loss of neurogenesis induces epithelial cells to modify their genetic program accordingly, indicating that they are ready to assume some of these functions. These "naturally" genetically modified epithelial cells are thus likely to enhance their sensitivity and response to environmental signals, to partially compensate for the lack of nervous system", explains Wanda Buzgariu, co-first author of the article. The detail of these new functions remains to be discovered, as well as how epithelial cells proceed to overexpress these genes and thus adapt their genetic program.-***-"This study also allows to go back to the origins of nervous systems. Epithelial cells most probably preceded nerve cells, performing some of their functions, although in a much slower way. «The loss of neurogenesis in Hydra may provide an opportunity to observe a reverse evolutive process, because it sheds light on a repressed ancestral genetic toolkit. An atavism of epithelial cells, when they most probably also possessed proto-neuronal functions", concludes Brigitte Galliot. "-Comment: As shown in the preceding articles in this series, neurons appeared about 600 million years ago, the most complex of the cell types to develop. They allowed the very complex Cambrian animals to appear, and this all led finally to our brains.