Modulating alternative splicing of MECP2 is a potential therapeutic strategy for Rett syndrome

Area of Science:

• Neuroscience and Genetics
• Molecular Biology and Therapeutics

Background:

• Rett syndrome (RTT) is a neurological disorder caused by loss-of-function mutations in the methyl-CpG-binding protein 2 (MECP2) gene.
• Current treatments like trofinetide offer only mild symptom relief; increasing MECP2 levels shows promise in RTT models.
• MECP2 exists in different isoforms (e1, e2), with e1 being more efficiently translated.

Purpose of the Study:

• To devise a therapeutic strategy to moderately increase functional MECP2 protein by modulating alternative splicing.
• To switch MECP2 isoform translation from the less efficient e2 to the more efficient e1 isoform.
• To investigate the therapeutic potential of this isoform switching strategy in RTT models.

Main Methods:

• Deletion of the MECP2 exon 2 (unique to the e2 isoform) in mouse models to promote e1 isoform production.
• Generation and analysis of induced pluripotent stem cell (iPSC)-derived neurons from RTT patients with MECP2 mutations.
• Utilizing exon 2-skipping morpholinos to induce isoform switching in vivo in mice.

Main Results:

• Exon 2 deletion in mice increased MECP2 protein levels by 50-60% and improved neurological phenotypes.
• In patient-derived iPSC neurons (MECP2-G118E), exon 2 deletion upregulated MECP2, ameliorated cellular deficits, and corrected transcriptomic dysregulation.
• Isoform switching using morpholinos successfully upregulated MECP2-E1 in vivo in mice.

Conclusions:

• Modulating MECP2 alternative splicing to favor the e1 isoform is a viable strategy to increase functional protein levels.
• This isoform switching approach shows therapeutic potential for Rett syndrome, particularly for patients with partially functioning MECP2 alleles.
• Antisense oligonucleotide-based strategies promoting isoform switching represent a promising avenue for future RTT therapeutics.