CNS-dominant human FMRP isoform rescues seizures, fear, and sleep abnormalities in Fmr1-KO mice

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Fragile X syndrome is a genetic neurodevelopmental disorder caused by the absence of the fragile X messenger ribonucleoprotein (FMRP).
• FMRP is a crucial protein regulating hundreds of genes, making gene replacement therapy a potential treatment strategy.
• Viral vector-mediated gene therapy is being explored to address the underlying molecular pathology of Fragile X syndrome.

Purpose of the Study:

• To evaluate the safety and therapeutic efficacy of a self-complementary adeno-associated viral (AAV) vector delivering a human brain isoform of FMRP.
• To assess the effects of intrathecal AAV vector injection on neurological and behavioral deficits in a mouse model of Fragile X syndrome.

Main Methods:

• Intrathecal administration of a self-complementary AAV vector encoding human FMRP into wild-type and Fragile X knockout (KO) mice.
• Analysis of neuronal and glial cell transduction patterns in the brain.
• Assessment of seizure activity, fear conditioning, electroencephalographic (EEG) slow-wave activity, circadian motor activity, and sleep patterns.

Main Results:

• Intrathecal AAV vector delivery resulted in primarily neuronal transduction in the brain, mimicking endogenous FMRP expression.
• AAV vector-treated KO mice exhibited recovery from epileptic seizures and normalized fear conditioning.
• EEG recordings showed reversal of slow-wave deficits, and circadian motor activity and sleep patterns were restored in treated KO mice.
• A correlation was observed between the level and distribution of brain transduction and the therapeutic response.

Conclusions:

• AAV vector-mediated gene therapy is a safe and effective preclinical approach for Fragile X syndrome.
• Restoration of FMRP levels via gene therapy can reverse key neurological and behavioral deficits associated with the disorder.
• These findings support the potential of AAV gene therapy for treating the most common genetic cause of cognitive impairment and autism in children.