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Pomona College Professor Makes Groundbreaking Discovery of Molecular Mechanism Behind Learning and Memory

Scientists understand that for learning and memory to take place, certain synapses must be strengthened. But exactly how this takes place has remained a mystery.

Pomona College Professor Karl Johnson is the lead author of a ground-breaking paper, to be published in the February 16 issue of Neuron, announcing the discovery of a novel molecular mechanism that controls synapse strength, which may be a key regulator of learning and memory.

Led by Johnson, the research team discovered that the Drosophila herapan sulfate proteoglycans (HSPGs) Syndecan (Sdc) and Dallylike (Dip) control distinct aspects of synaptic biology. While Sdc and Dip both act by binding the receptor molecule LAR, Sdc-LAR interactions increase synaptic strength, while Dlp-LAR interactions weaken synapses.

The discovery is important because these genes are highly conserved throughout evolution. Humans, for example, have three versions of LAR and four versions of Sdc. The larger question is how memory takes place in humans at the molecular level, and there is some evidence that the same molecular process is at work.

Sdc and LAR are both present in the hippocampus of vertebrate brains. Evidence has been found that mutations in LAR in vertebrates (e.g. mice) cause memory deficits.

This newest discovery, along with previous research, indicates that these three genes are a potent mechanism for synapse strengthening and weakening and are likely to serve as the molecular building blocks for learning and memory.

The Neuron article is titled "The HSPGs Syndecan and Dallylike Bind the Receptor Phosphatase LAR and Exert Distinct Effects on Synaptic Development.”

Karl Johnson is the Sarah Rempel and Herbert S. Rempel Professor of Neuroscience and assistant professor of biology at Pomona College.