FMRP links optimal codons to mRNA stability in neurons

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Fragile X syndrome (FXS) is a genetic disorder caused by the inactivation of the FMR1 gene.
• This inactivation leads to the loss of Fragile X mental retardation protein (FMRP), an RNA-binding protein crucial for regulating gene expression.
• FMRP's primary role involves repressing the translation of specific target messenger RNAs (mRNAs).

Purpose of the Study:

• To investigate the translational dysregulation in the mouse brain cortex in the context of Fragile X syndrome.
• To understand the role of FMRP in mRNA stability and translational control.
• To elucidate the molecular mechanisms underlying FXS pathogenesis and potential therapeutic rescue strategies.

Main Methods:

• Ribosome profiling and RNA sequencing were employed to analyze translational changes in the mouse brain cortex.
• RNA metabolic labeling was used to assess mRNA degradation rates in FMRP-deficient neurons.
• Analysis of FMRP binding targets and their correlation with codon optimality was performed.

Main Results:

• Most observed changes in ribosome occupancy on mRNAs were primarily driven by alterations in transcript abundance.
• Down-regulated mRNAs, critical for neuronal and synaptic functions, were significantly enriched for FMRP binding targets.
• FMRP preferentially binds to mRNAs with optimal codons, suggesting a role in stabilizing these transcripts through translational machinery interactions.
• In FMRP-deficient neurons, reduced mRNA levels were linked to increased degradation, correlated with codon optimality.

Conclusions:

• FMRP plays a critical role in maintaining neuronal and synaptic function by regulating mRNA stability.
• Codon optimality is a key factor in FMRP-mediated mRNA stabilization, impacting translational homeostasis.
• Genetic rescue of FXS-like phenotypes involves restoring steady-state RNA levels and rebalancing translational control, highlighting FMRP's essential function.