The death of neurons, both in the brain and in the eye, leads to a number of neurodegenerative diseases in humans, including blindness and Parkinson's disease.Current treatments for these diseases can only slow the progress of the disease, because once the neurons die, there is no substitute.

Now, researchers from the University of Notre Dame, Johns Hopkins University, Ohio State University and the University of Florida have uncovered key genetic networks that regulate whether neurons regenerate in certain animals.

Study author David Hyde, professor of biological sciences at Notre Dame, said: 'This study shows that retinal neurons can regenerate.We now think that the regeneration of neurons in the brain will be similar.".

In the study, published in the journal Science, researchers mapped the genes of animals with the ability to regenerate retinal neurons.When a zebrafish's retina is damaged, for example, cells called Muller glia undergo a process called reprogramming.During the reprogramming process, Muller glia change their gene expression, making them resemble progenitor cells or cells in an organism's early development.As a result, these now-progenitor cell-like cells can become any cell needed to repair a damaged retina.

Like zebrafish, people have Muller glia cells.However, when the human retina is damaged, Muller glia proliferate, a process that does not allow them to be reprogrammed.

"After identifying different retinal injury recovery animal processes, we had to determine whether reprogramming and glial formation processes were similar.Would the Muller glia follow the same path in regenerative and non-regenerative animals, or would they be completely different?If we want to be able to regenerate human retinal neurons using Muller glia, we need to know whether we need to redirect the current Muller glia pathway or do we need a completely different pathway?"

The regeneration process, the team found, requires only that an organism "reactivate" its early development.In addition, the researchers were able to show that Muller glia cells also experienced glial proliferation during the regeneration process of zebrafish, suggesting that organisms capable of regenerating retinal neurons follow a similar path to animals that cannot.The gene network in zebrafish can transfer Muller glia cells from glia cells to the reprogramming state, while the gene network in the mouse model prevents the reprogramming of Muller glia cells.

The researchers modified the Muller glia cells in zebrafish to a similar state, preventing reprogramming, and also regenerated some retinal neurons in the mouse model.Next, the researchers will look at the number of gene regulatory networks responsible for neuronal regeneration, and which genes in those networks are responsible for regeneration.