Visual Recovery Reflects Cortical MeCP2 Sensitivity in Rett Syndrome

Area of Science:

• Neuroscience
• Genetics
• Developmental Biology

Background:

• Rett syndrome (RTT) is a neurodevelopmental disorder characterized by regression in motor, sensory, and cognitive functions.
• Sensory disruptions, particularly in visual processing, significantly contribute to RTT's complex symptoms.
• Current genetic therapies for RTT have shown success in motor and respiratory functions, but their impact on sensory deficits is less understood.

Purpose of the Study:

• To investigate the efficacy of restoring MeCP2 expression in reversing visual pathway deficits in mouse models of Rett syndrome.
• To explore the potential of genetic medicine-based therapies for addressing sensory impairments in RTT.

Main Methods:

• Utilized genetically reversible mouse models (Mecp2^stop/y and Mecp2^stop/x) of MeCP2 deficiency.
• Employed advanced electrophysiological, anatomical, and behavioral techniques to assess visual function.
• Evaluated the effects of initiating MeCP2 expression at different stages of development and disease progression.

Main Results:

• Reactivation of MeCP2 after postnatal day 35 in Mecp2^stop/y mice reversed cortical dysfunction and restored visual function.
• Thalamic circuit organization was preserved with MeCP2 restoration, despite some residual cortical abnormalities.
• Even in adult Mecp2^stop/x mice with established regression, MeCP2 reactivation significantly reduced symptoms.

Conclusions:

• Cortical circuits demonstrate high sensitivity to MeCP2 expression levels throughout development and in mature brains.
• Partial restoration (60-70%) of MeCP2 protein levels is sufficient to rescue sensory functions, even post-regression.
• These findings support the transformative potential of genetic therapies for RTT, indicating that partial MeCP2 restoration can substantially improve sensory processing and patient quality of life.