Some genes and proteins boosting growth and development of embryos also contribute in channeling chemical signals that help adults learn, remember, forget perchance even get addicted, the biologists of University of Utah have discovered.
"We found that these molecules and signaling pathways [named Wnt] do not retire after development of the organism, but have a new and surprising role in the adult. They are called back to action to change the properties of the nervous system in response to experience," says biology Professor Andres Villu Maricq, senior author of the new study in the March 30 issue of the journal Cell
The study was performed in C. elegans - the millimeter-long roundworm or nematode - which has a nervous system that serves as a model for those of vertebrate animals, including humans.
Because other Wnt pathways in worms are known to work in humans too, the researchers believe that Wnt genes, the Wnt proteins they produce and so-called "Wnt signaling" also are involved in human learning, memory and forgetting.
"Almost certainly what we have discovered is going on in our brain as well," Maricq says. And because a worm nerve-signal "receptor" in the study is analogous to a human nicotine receptor involved in addiction, schizophrenia and some other mental disorders, some of the genes identified in the worm study "represent possible new targets for treatment of schizophrenia and perhaps addiction," he adds.
Wnt genes and their proteins already were known to "pattern the development and distribution of organs in the body" during embryo development, and to be responsible for various cancers and developmental defects when mutated, he says.
Maricq conducted the study with these Utah biologists: doctoral students Michael Jensen and Dane Maxfield; postdoctoral researchers Michael M. Francis, Frederic Hoerndli and Rui Wang; undergraduate Erica Johnson; Penelope Brockie, a research associate professor; and David M. Madsen, a senior research specialist. The study was funded by the National Institutes of Health and the American Heart Association.
Synapse Plasticity is the Basis of Learning and Memory
Synapses are the connections between nerve cells (neurons). Nerve signals are transmitted through synapses. Learning and memory concern how these connections are made, broken, strengthened or weakened. Proteins known as receptors are delivered to the synapses or removed from them to strengthen or weaken the connection.
In the new study, Maricq and colleagues identified a "Wnt signaling pathway" - a series of genes and the proteins they produce - that controls the strength of nerve signal transmission from one neuron through a synapse to the next neuron. This allows "plasticity" of synapses - a key factor in learning, retaining memories and forgetting.