Role of Experience in Regulating Levels of the Fragile X Protein
Kenneth J. Mack, MD, PhD
Principal Investigator
Peter K. Todd, MD, PhD
FRAXA Postdoctoral Fellow
Mayo Clinic
Rochester, MN
2000-2001 Grant Funding: $49,000
The Results
The team published their findings demonstrating that FMRP is required for type-I metabotropic glutamate receptor-dependent translation of PSD-95. Peter K. Todd, Kenneth J. Mack, and James S. Malter, PNAS | November 25, 2003 | vol. 100 | no. 24
These results showed that FMRP plays a dynamic, activity-dependent role in synaptic function, rather than simply being absent in Fragile X. This helped establish a key concept in the field: that Fragile X involves dysregulated synaptic signaling and protein synthesis in response to neuronal activity, not just loss of a structural protein.
Importantly, this work contributed to the scientific foundation for targeting mGluR signaling and synaptic protein translation as therapeutic strategies—approaches that have driven multiple Fragile X drug development programs over the past two decades.
The Next Steps
Dr. Peter Todd went on to establish his own lab at the University of Michigan where he was awarded additional grants from FRAXA to further his work.
The Science
This FRAXA-funded project, led by Kenneth J. Mack at the Mayo Clinic, investigated how levels of the Fragile X protein (FMRP) are regulated in the brain in response to activity and experience. Rather than treating FMRP as a static molecule, the team asked a fundamental question: does neuronal activity — such as seizures or environmental stimulation — change how much FMRP is produced and how it functions?
To address this, the researchers studied FMRP regulation in vivo (in living animals), focusing on how synaptic activity and signaling pathways influence protein translation at synapses. Their work centered on mGluR-dependent translation and synaptic proteins such as PSD-95, key components of learning and memory.
This research was part of a broader effort to understand how Fragile X disrupts activity-dependent protein synthesis in the brain, an idea that later became central to the mGluR theory of Fragile X and to many subsequent therapeutic strategies.