Rescue of a familial dysautonomia mouse model by AAV9-Exon-specific U1 snRNA.

Familial dysautonomia (FD) is a currently untreatable, neurodegenerative disease caused by a splicing mutation (c.2204+6T>C) that causes skipping of exon 20 of the elongator complex protein 1 (ELP1) pre-mRNA. Here, we used adeno-associated virus serotype 9 (AAV9-U1-FD) to deliver an exon-specific U1 (ExSpeU1) small nuclear RNA, designed to cause inclusion of ELP1 exon 20 only in those cells expressing the target pre-mRNA, in a phenotypic mouse model of FD. Postnatal systemic and intracerebral ventricular treatment in these mice increased the inclusion of ELP1 exon 20. This also augmented the production of functional protein in several tissues including brain, dorsal root, and trigeminal ganglia. Crucially, the treatment rescued most of the FD mouse mortality before one month of age (89% vs 52%). There were notable improvements in ataxic gait as well as renal (serum creatinine) and cardiac (ejection fraction) functions. RNA-seq analyses of dorsal root ganglia from treated mice and human cells overexpressing FD-ExSpeU1 revealed only minimal global changes in gene expression and splicing. Overall then, our data prove that AAV9-U1-FD is highly specific and will likely be a safe and effective therapeutic strategy for this debilitating disease.
Competing Interests: Declaration of interests F.P. is listed as inventor of the U.S. patent n. 9,669,109 “A modified human U1snRNA molecule, a gene encoding for the modified human U1snRNA molecule, an expression vector including the gene, and the use thereof in gene therapy of familial dysautonomia and spinal muscular atrophy.” As such, the inventors could potentially benefit from any future commercial exploitation of patent rights, including the use of ExSpeU1s in FD. S.A.S. is a paid consultant to PTC Therapeutics and is an inventor on several U.S. and foreign patents and patent applications assigned to the Massachusetts General Hospital, including U.S. Patents 8,729,025 and 9,265,766, both entitled “Methods for altering mRNA splicing and treating familial dysautonomia by administering benzyladenine,” filed on August 31, 2012 and May 19, 2014 and related to use of kinetin; and U.S. Patent 10,675,475 entitled, “Compounds for improving mRNA splicing” filed on July 14, 2017 and related to use of BPN-15477. E.M. and S.A.S. are inventors on an International Patent Application Number PCT/US2021/012,103, assigned to Massachusetts General Hospital and entitled “RNA Splicing Modulation” related to use of BPN-15477 in modulating splicing.
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