# Drosophila Arc1 capsids assembled in vitro delivered Cas9 to mouse muscle, up to 18% exon skipping

- Published: 2026-11-05 21:19 UTC
- Section: Life & Health › Biotechnology
- Tags: Drosophila Arc1 capsid, Cas9 delivery, exon skipping, dystrophin restoration, Duchenne muscular dystrophy mouse model, SORCS2 receptor, cell-free protein nanoparticles, Broad Institute, Feng Zhang
- URL: https://realtech.media/news/rt-ca70fe312fc61bebb9465122_drosophila_arc1_capsids/

**Researchers at the Broad Institute and MIT built capsids from purified protein and RNA without cells; in a mouse model of Duchenne muscular dystrophy they restored dystrophin in muscle fibers.**

![Drosophila Arc1 capsids assembled in vitro delivered Cas9 to mouse muscle, up to 18% exon skipping](https://sgzwpqqelzmajkcubgkl.supabase.co/storage/v1/object/public/rt-media/2026/11/7958b35c7d23bfd4.jpg)
*Ruberte, J., Schofield, P.N., Sundberg, J.P. et al., Wikimedia Commons, CC BY 4.0*

A team led by Feng Zhang at the Broad Institute of MIT and Harvard, MIT and the Howard Hughes Medical Institute reconstituted a capsid of the Drosophila melanogaster protein Arc1 (dArc1) from purified recombinant components and in vitro transcribed RNA. The capsids carried Cas9 gene editors into muscle of mice that model Duchenne muscular dystrophy. According to the report in Nature Communications, intramuscular injection achieved up to 18% exon skipping and restored dystrophin expression in muscle fibers [1].

## Cell-free capsid assembly

Arc1 is a capsid-forming protein derived from a retroelement. Earlier capsid-based delivery systems, the authors note, required assembly inside cells or relied on fusogens to enter cells, which limited scalability and utility. Here the whole system is fully defined and assembled without cells from purified protein and RNA [1].

The authors engineered the RNA-binding domain of dArc1 so that the capsids efficiently encapsulate both mRNA payloads and Cas9 ribonucleoproteins [1]. This allowed the same particle platform to carry different types of molecular cargo.

## Receptor binding and muscle editing

The study shows that dArc1 capsids bind mammalian cells through a direct interaction with the surface receptor SORCS2 [1]. The authors used this interaction to direct delivery of the cargo into cells without added fusogens.

For the in vivo test, capsids carrying Cas9 gene editors were injected into muscle of mdx mice, a model of Duchenne muscular dystrophy. The result was up to 18% exon skipping, and dystrophin expression was restored in muscle fibers [1]. The experiment was carried out in animals only.

The authors conclude that protein nanoparticles assembled in vitro have potential for delivering molecular cargoes [1]. Several authors, including Feng Zhang, are coinventors on a pending patent application related to dArc and its use as a delivery vehicle, filed by the Broad Institute and MIT.

## Sources

1. [Nature Communications](https://doi.org/10.1038/s41467-026-79058-8)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-ca70fe312fc61bebb9465122_drosophila_arc1_capsids/