Scientists have found how mutations in a single gene can produce the complex cognitive deficits characteristic of Fragile X Syndrome, the most common inherited form of intellectual disability.
As the majority of patients with Fragile X Syndrome also display autism-like symptoms, the findings offer hope for treating both conditions.
Their study defines a set of messenger RNA (mRNA) molecules that the Fragile-X mental retardation protein (FMRP) binds in the brains of mice.
Many of these mRNAs encode proteins that function at neurons' connection points.
When properly bound, FMRP prevents the translation of these mRNAs into proteins until the time is right.
"By understanding for the first time the direct targets of FMRP and its actions, we open up a whole world of potential avenues for therapies designed to make kids with Fragile X or autism better," said Robert Darnell, a Howard Hughes Medical Institute investigator at The Rockefeller University.
Further experiments suggest that FMRP acts as a "brake," reversibly stalling ribosomes after they bind mRNA.
Robert Darnell likened FMRP to the nozzle at the end of a hose.
It allows the mRNA transcripts to be loaded with ribosomes in the locations where they will be needed, and when the time is right, bursts of translation (protein synthesis) can occur.
That sort of tight control is likely to be critical for the formation and plasticity of neural connections, the cellular foundation for learning and memory.
Their basic scientific discoveries suggest two different overall strategies for treating Fragile X Syndrome: by lowering the activity of particular proteins normally kept under wraps by FMRP or by replacing FMRP's ability to stall ribosomes.
The finding was reported in the July 22nd issue of the journal Cell.