Poster abstracts

Poster number 53 submitted by Anthony Hinrich

An antisense oligonucleotide that targets splicing to treat Usher syndrome in mice

Jennifer J. Lentz (Neuroscience Center, LSUHSC, New Orleans, LA), Anthony J. Hinrich (Department of Cell Biology and Anatomy, Rosalind Franklin University of Medicine and Science, North Chicago, IL), Francine M. Jodelka, Kate E. McCaffrey, Dominik M. Duelli (Rosalind Franklin University of Medicine and Science, North Chicago, IL), Mette Flaat, Nicolas G. Bazan (Neuroscience Center, LSUHSC, New Orleans, LA), Frank Rigo (Isis Pharmaceuticals, Carlsbad, CA), Michelle L. Hastings (Department of Cell Biology and Anatomy, Rosalind Franklin University of Medicine and Science, North Chicago, IL)

Abstract:
Usher syndrome (Usher) is the leading genetic cause of combined deafness and blindness. Type 1 Usher (Usher 1) is the most severe form of the disease and is characterized by hearing impairment and vestibular dysfunction from birth, and the development of retinitis pigmentosa (RP) in early adolescence. A 216G>A (216A) mutation in USH1C accounts for all Usher 1 cases in Acadian populations of the United States and Canada. The USH1C gene codes for the protein harmonin which is essential for development of hair cells in the ear and survival of retinal cells. The 216G>A mutation creates a cryptic splice site that is used preferentially over the authentic splice site. Use of the cryptic site gives rise to a frame-shift that results in the production of a truncated, non-functional protein.

We developed an antisense oligonucleotide, called ASO-Ush, which binds to the 216A mutation in USH1C RNA and blocks it from being recognized by the cellular splicing machinery and splicing is re-estalished at the authentic splice site. In this way, the deleterious effects of the mutation are subverted and harmonin expression restored. The chemistry of ASO-USH makes the molecule very stable and easily deliverable to different cell types in the body. The specificity of the molecule eliminates harmful side-effects that typically arise from off-target effects of drugs.

ASO-USH was tested for its ability to block the 216A mutation and restore harmonin expression in a mouse model of Usher syndrome. These mice were engineered to have the identical Ush1c.216G>A mutation (216AA) as humans. These Usher mice are deaf, exhibit circling behavior indicative of severe vestibular dysfunction and have retinal dysfunction by 1 month of age and begin to lose photoreceptors between 6 and 12 months of age. We found that mice treated with a single dose of ASO-USH shortly after birth had normal vestibular function and could hear for up to six months of age. The treated mice also had a modest improvement in visual function at one month of age. Our results demonstrate that ASO-USH can effectively correct an Ush1c mutation and suggest the therapeutic potential of this class of molecule in Usher syndrome and other diseases of the eye and ear.

Keywords: antisense oligonucleotide, splicing, Usher syndrome