Null Mutation of the Gene by TALEN Leading to Progressive Hearing Loss and Retinal Degeneration in C57BL/6J Mice.

Fascin2 (FSCN2) is an actin cross-linking protein that is mainly localized in retinas and in the stereocilia of hair cells. Earlier studies showed that a deletion mutation in human () gene could cause autosomal dominant retinitis pigmentosa. Recent studies have indicated that a missense mutation in mouse gene (R109H) can contribute to the early onset of hearing loss in DBA/2J mice. To explore the function of the gene, was knocked out using TALEN (transcription activator-like effector nucleases) on the C57BL/6J background. Four mouse strains with deletions of 1, 4, 5, and 41 nucleotides in the target region of were developed. F1 heterozygous ( ) mice carrying the same deletion of 41 nucleotides were mated to generate the mice. As a result, the mice showed progressive hearing loss, as measured in the elevation of auditory brainstem-response thresholds. The hearing impairment began at age 3 weeks at high-stimulus frequencies and became most severe at age 24 weeks. Moreover, degeneration of hair cells and loss of stereocilia were remarkable in mice, as revealed by F-actin staining and scanning electron microscopy. Furthermore, compared to the controls, the mice displayed significantly lower electroretinogram amplitudes and thinner retinas at 8, 16, and 24 weeks. These results demonstrate that, in C57BL/6Jmice, is essential for maintaining ear and eye function and that a null mutation of leads to progressive hearing loss and retinal degeneration.