Dual Genetic Approach Enhances Treatment of Spinal Muscular Atrophy

The study employs a CRISPR-Cas9-based homology-independent targeted integration (HITI) strategy to correct the SMA mutation in mice in conjunction with Smn1 cDNA supplementation. HITI, effective in both dividing and non-dividing cells, uses non-homologous end joining (NHEJ) to integrate transgenes, ensuring stable gene correction without the need for homologous recombination.

The researchers targeted intronic sequences upstream of exon 2 of the Smn1 gene to avoid deleterious insertions and deletions, incorporating a codon-optimised Smn1 cDNA to restore functional SMN protein production. AAV-PHP.eB capsids were utilised for their superior transduction efficiency, delivering the genetic constructs to motor neurons and peripheral tissues.

The results demonstrated significant improvements in SMA mice treated with the Gene-DUET strategy. The dual treatment not only corrected the genetic defect but also enhanced SMN1 protein levels, leading to increased body weight, improved motor function, and prolonged survival compared to untreated mice.

Notably, treated mice exhibited restored motor capabilities and better overall health, with RNA sequencing showing a reversal of SMA-induced molecular dysfunctions in the spinal cord. The Gene-DUET approach outperformed cDNA supplementation alone, offering a promising avenue for durable and effective SMA therapy.

The research was led by Fumiyuki Hatanaka and Juan Carlos Izpisua Belmonte at the Salk Institute for Biological Studies and the Altos Labs. The findings were published today in Nature Communications.