Postsynaptic FMRP bidirectionally regulates excitatory synapses as a function of developmental age and MEF2 activity

Area of Science:

• Neuroscience
• Molecular Biology
• Developmental Biology

Background:

• Synapse formation and elimination are critical during postnatal development.
• Molecular mechanisms governing these developmental shifts remain largely unknown.

Purpose of the Study:

• To investigate the roles of fragile X mental retardation protein (FMRP) and myocyte enhancer factor 2 (MEF2) in regulating synapse development.
• To elucidate how FMRP and MEF2 interact to control synapse formation and elimination rates.

Main Methods:

• Utilized hippocampal slice cultures from rodents at different postnatal ages (P6-P7 and P13-P16).
• Manipulated the expression of FMRP and MEF2 using acute postsynaptic expression and knockout strategies.
• Assessed excitatory synaptic function and synapse number.

Main Results:

• FMRP promotes synapse maturation in early postnatal development (P6-P7).
• FMRP suppresses synapse number in later postnatal development (P13-P16).
• MEF2 activity levels correlate with developmental age and modulate FMRP's effects on synapses.

Conclusions:

• FMRP and MEF2 act in concert to fine-tune synapse formation and elimination.
• This interaction is dependent on developmental stage and neuronal activity.
• Findings reveal a molecular mechanism for activity-dependent synaptic plasticity during development.