First published online July 11, 2008
Development 135, 1503e (2008)
© The Company of Biologists Limited
Fragile X marks synaptic defects
The fragile X syndrome (FraX) mental retardation and autism spectrum
disorder is caused by loss of FMR1 function. FMRP, the RNA-binding
translation regulator encoded by FMR1, modulates synapse structure
and function, but where and when its loss causes synaptic defects is unclear.
Now, on p. 2637,
Gatto and Broadie reveal FMRP's spatiotemporal roles in synaptogenesis by
conditionally driving its expression in a FraX fly model. The constitutive
presynaptic expression of dFMRP in these flies rescues their synaptic
architectural defects but not normal neurotransmission. From these and other
findings, they conclude that dFMRP has a crucial presynaptic role in
regulating neuromuscular junction synaptic architecture, but acts
post-synaptically in regulating neurotransmission strength. The authors also
rescued synaptic structural defects in FraX flies by expressing dFMRP in early
and late larval development; the rescue of defects in later development
indicates that dFMRP can mediate late-stage plasticity to reverse some
synaptic impairments. Thus, although FraX is primarily a developmental
disease, late-stage therapeutic intervention might prove to be beneficial.

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Related articles in Development:
- Temporal requirements of the fragile X mental retardation protein in the regulation of synaptic structure
- Cheryl L. Gatto and Kendal Broadie
Development 2008 135: 2637-2648.
[Abstract]
[Full Text]