Intestinal protease overactivity — not neuronal dysfunction — drives motor neuron loss in C. elegans SMA model

Spinal muscular atrophy (SMA) is caused by loss-of-function mutations in SMN1, a gene encoding a ubiquitously expressed spliceosome assembly factor. A longstanding puzzle in SMA biology is why a protein present in all cells selectively destroys motor neurons. A preprint posted to bioRxiv on 17 August 2026 from Cold Spring Harbor Laboratory describes work in the nematode Caenorhabditis elegans that challenges the prevailing cell-autonomous model of this selective vulnerability.

Using C. elegans strains carrying loss-of-function alleles in smn-1, researchers report that the primary driver of neuromuscular decline is not a defect intrinsic to neurons or muscle cells, but rather hyperactive intestinal proteolysis. Elevated protease activity in the gut appears to produce systemic effects that ultimately compromise motor neuron viability. The authors propose that understanding inter-tissue communication from the intestine may open alternative avenues for thinking about SMA pathology.

The study is notable for its non-neuronal framing of a canonical neurological disease gene. The C. elegans model allows tissue-specific genetic manipulations that are difficult to achieve in mammalian systems, though the translational relevance to human SMA remains to be established. The work has not yet been peer-reviewed.