Targeted RNA editing in brainstem alleviates respiratory dysfunction in a mouse model of Rett syndrome.

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Rett syndrome is a severe neurological disorder caused by loss-of-function mutations in the Methyl CpG binding protein 2 (MECP2) gene.
• Both loss-of-function and overexpression of MECP2 can lead to disease, necessitating precise therapeutic interventions.
• Current therapeutic strategies are limited, highlighting the need for innovative approaches.

Purpose of the Study:

• To investigate the efficacy of a targeted RNA-editing strategy using engineered ADAR2 to correct MECP2 mutations.
• To evaluate if this approach can restore MECP2 protein levels without exceeding physiological limits.
• To assess the therapeutic benefits, including symptom alleviation and survival extension, in a mouse model of Rett syndrome.

Main Methods:

• Development of adeno-associated viruses (AAVs) coexpressing a bioengineered wild-type ADAR2 catalytic domain (Editase^wt) and either *Mecp2*-targeting or non-targeting *gfp* RNA guides.
• Systemic administration of these AAVs into male mice with a specific guanosine to adenosine mutation in *Mecp2*.
• Quantification of RNA-editing frequency, MECP2 expression and function, respiratory patterns, and survival rates in treated mice.

Main Results:

• The *Mecp2*-targeting virus achieved the highest RNA-editing frequency in the brainstem of mutant mice.
• Successful rescue of MECP2 expression and function was observed in the brainstem following treatment with the *Mecp2*-targeting virus.
• Abnormal Rett-like respiratory patterns were alleviated, and survival was significantly prolonged in treated mice compared to controls.

Conclusions:

• Targeted RNA editing offers a promising therapeutic avenue for Rett syndrome by precisely correcting MECP2 mutations.
• This approach can restore essential protein function and ameliorate key disease phenotypes in a relevant animal model.
• The distribution of guide RNA, rather than the editing enzyme, primarily influenced regional editing levels, providing insights for future therapeutic design.