CRISPR-Mediated Removal of Mutated COL7A1 Exons Shows Therapeutic Potential for Epidermolysis Bullosa

Premature stop codons caused by mutations in the COL7A1 gene frequently lead to generalised recessive dystrophic epidermolysis bullosa (RDEB). This devastating, incurable inherited skin disorder causes widespread blistering from birth, that while healing, create severe scarring that impairs eating, mobility, and vision.

Individuals with RDEB carry a very high risk of developing a form of skin cancer called squamous cell carcinoma in young adulthood. In these individuals, this cancer tends to be unusually aggressive and is often life-threatening, further highlighting the urgent need for new therapies.

Earlier research has shown that eliminating mutated COL7A1 exons and subsequently reframing the gene may preserve protein function, suggesting a promising therapeutic approach. However, investigations examining the long-term in vivo effects of mutant exon removal have primarily focused on a single small exon known as exon 80.

In a study published this week in Human Gene Therapy, researchers from Spain and Germany investigated whether CRISPR-mediated targeted exon removal through non-homologous end joining could be successfully applied to larger exons, specifically exons 73 and 105 of COL7A1.

The research team demonstrated that ribonucleoprotein complexes containing Cas9 protein and optimised sgRNA pairs could efficiently remove the target exons when delivered via electroporation. Notably, deletion of exons 73 and 105 restored type VII collagen (C7) production in primary RDEB patient cells harbouring frameshift mutations within these regions. In vitro biochemical studies confirmed that the resulting C7 protein variants maintained normal stability when expressed at physiological concentrations.

Furthermore, in vivo experiments using regenerated skin grafted onto immunocompromised mice showed that cells edited to remove exon 73 or 105 properly deposited C7 at the basement membrane zone, successfully restoring normal adhesion between the dermis and epidermis. These findings further emphasise the potential of exon-deletion strategies for treating RDEB.

Read the full article entitled 'Safe and Efficacious Permanent Removal of Large COL7A1 Exons for Gene Reframing as a Reliable Therapeutic Strategy for Recessive Dystrophic Epidermolysis Bullosa' here.