Altered synaptic plasticity in a mouse model of fragile X mental retardation

TLDR

Fragile X syndrome arises from Fmr1 mutations that eliminate FMRP, a protein that binds specific mRNAs to regulate translation, yet its effect on neuronal function has been unclear. In Fmr1‑knockout mice, mGluR‑dependent long‑term depression in the hippocampus is markedly increased, showing that FMRP normally limits this synaptic plasticity and suggesting new therapeutic targets for fragile X syndrome.

Abstract

Fragile X syndrome, the most common inherited form of human mental retardation, is caused by mutations of the Fmr1 gene that encodes the fragile X mental retardation protein (FMRP). Biochemical evidence indicates that FMRP binds a subset of mRNAs and acts as a regulator of translation. However, the consequences of FMRP loss on neuronal function in mammals remain unknown. Here we show that a form of protein synthesis-dependent synaptic plasticity, long-term depression triggered by activation of metabotropic glutamate receptors, is selectively enhanced in the hippocampus of mutant mice lacking FMRP. This finding indicates that FMRP plays an important functional role in regulating activity-dependent synaptic plasticity in the brain and suggests new therapeutic approaches for fragile X syndrome.