No to blindness
Biologists have unblocked the natural vision restoration system
Anatoly Glossev, Vesti
Mammalian DNA contains genes responsible for repairing the damaged retina of the eye. Evolution has blocked their work for some reason, but these genes can be artificially "turned on". Biologists have already performed this operation in experiments with experimental mice, and animals have new neurons to replace the damaged ones.
The achievement is described in a scientific article published in the journal Science by a group led by Seth Blackshaw from Johns Hopkins University (Hoang et al., Gene regulatory networks controlling vertebrate retinal regeneration).
It's no secret that many animals are much more capable of regeneration than mammals, including humans. For example, danio rerio fish can repair damaged retina of the eye. Many people who have lost their sight due to retinal injuries would not give up such an ability.
As scientists have found out, after damage to the retina in these fish, cells of the so-called Muller glia are activated. They are "reprogrammed", turning into stem cells. New retinal neurons are formed from these stem cells. Mammals also have Muller's glia, but for some reason the process described above does not start. Why?
The authors of the new study were looking for an answer to this question. They found out which genes are activated when the retina is damaged in danio rerio, chickens and mice (note that the eyes of mice are very similar to human ones).
Scientists have identified the genes that are responsible for reprogramming glia cells in danio rerio. It turned out that the same genes are present in birds and mice. These genes are not damaged by mutations and are ready to work. Moreover, if the retina is damaged, they are put in a "state of high alert". But in the end, only some of them are included in chickens. In mice, glial cell reprogramming genes are not activated at all.
Why? As biologists have found out, there are genes that actively counteract this. They encode proteins from a family known as nuclear factor I (or NF-I).
These are so–called transcription factors - proteins that attach to the DNA molecule and block the work of some genes. Including, as it turned out, the genes responsible for the regeneration of the retina.
As an experiment, biologists blocked the synthesis of NF-I in mice. And the cells of Muller's glia immediately began the process of "rebirth". After 21 days, new neurons were formed from them, however, only two types: bipolar and amacrine.
Let's explain that the retina contains many types of nerve cells, so this result is still far from full regeneration. But, at least, it has been established that mammals have genes responsible for restoring neurons, and that their work is actively hindered by some other genes.
"Our study as a whole shows that mammals, including humans, have the potential for regeneration, but evolutionary pressure for some reason turned it off," sums up Blackshaw (Johns Hopkins Scientists Find Mammals Share Gene Pathways That Allow Zebrafish to Grow New Eyes).
This is an amazing result. It is difficult to understand what evolutionary advantages were given by genes suppressing neuronal repair. Scientists have yet to figure this out.
A thorough study of the retinal neuron regeneration system and the forces that counteract it can pave the way to victory over blindness. And perhaps to many other victories, because similar regeneration mechanisms work in danio rerio in a variety of organs.
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