The brain is the user of the genetic toolkit
On may 14, 2010, a group of researchers from Friedrich Miescher Institute in Basel, Switzerland and Universität Heidelberg, Germany reported that in response to light, as well as in response to synaptic stimulation in hippocampal and cortical neurons, retinal neurons upregulate synthesis of the miR-183/96/182 cluster, miR-204, and miR211. This is another experimental example of the neural control of gene expression. These results add to the abundant volume of empirical evidence on the role of the nervous system in regulating gene expression. and in response to synaptic stimulation in hippocampal and cortical neurons.
“Here, we demonstrate that levels of the miR-183/96/182 cluster, miR-204, and miR-211 are regulated by different light levels in the mouse retina. Concentrations of these microRNAs were downregulated during dark adaptation and upregulated in light-adapted retinas, with rapid decay and increased transcription being responsible for the respective changes. We identified the voltage-dependent glutamate transporter Slc1a1 as one of the miR-183/96/182 targets in photoreceptor cells. We found that microRNAs in retinal neurons decay much faster than microRNAs in nonneuronal cells. The high turnover is also characteristic of microRNAs in hippocampal and cortical neurons, and neurons differentiated from ES cells in vitro. Blocking activity reduced turnover of microRNAs in neuronal cells while stimulation with glutamate accelerated it. Our results demonstrate that microRNA metabolism in neurons is higher than in most other cells types and linked to neuronal activity”.
Why does the light not induce these miRNA genes in other non-neuronal cells? It’s clear that it is not the light per se, rather the output of the processing of light in neurons and neural circuits that induces expression and rapid decay of specific miRNAs. It is clear that this is a nongenetic mechanism. One can’t predict how much longer neoDarwinian biology will continue neglect and ignore these epigenetic mechanisms of gene expression and their evolutionary potential, but one thing is certain: It does this at its own cost and credibility.