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Altered synaptic plasticity in a mouse model of fragile X mental retardation
Kimberly M Huber1, Sean M Gallagher, Stephen T Warren
1Department of Neuroscience, Howard Hughes Medical Institute, Brown University, Providence, RI 02912, USA.
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.
Insights
Fragile X syndrome results from FMR1 gene mutations, impacting fragile X mental retardation protein (FMRP) levels. Loss of FMRP enhances a specific form of synaptic plasticity in mice, suggesting new therapeutic targets.
Area of Science:
- Neuroscience
- Genetics
- Molecular Biology
Background:
- Fragile X syndrome is the most common inherited cause of intellectual disability.
- It stems from mutations in the FMR1 gene, affecting fragile X mental retardation protein (FMRP).
- FMRP is known to bind mRNAs and regulate translation, but its role in neuronal function is unclear.
Purpose of the Study:
- To investigate the functional consequences of FMRP loss on mammalian neuronal function.
- To explore the role of FMRP in activity-dependent synaptic plasticity.
Main Methods:
- Utilized mutant mice lacking the FMRP protein.
- Examined protein synthesis-dependent long-term depression (LTD) in the hippocampus.
- Investigated LTD triggered by metabotropic glutamate receptor activation.
Main Results:
- A specific form of protein synthesis-dependent synaptic plasticity, LTD, was selectively enhanced in the hippocampus of FMRP-deficient mice.
- This indicates FMRP normally inhibits this form of plasticity.
Conclusions:
- FMRP plays a crucial role in regulating activity-dependent synaptic plasticity in the brain.
- These findings suggest potential new therapeutic strategies for Fragile X syndrome.