Wenck, N.; Zorin, M.; Wang, Q.; Kroell, S.; Hay, K.; Rickert, C.; Mendez-Lago, M.; Karunanithi, S.; Athanasiou, D.; Ziaka, K.; De Angeli, P.; Stingl, K.; Kohl, S.; Cheetham, M. E.; Mittmann, T.; Nagel-Wolfrum, K.

Usher syndrome type 1, caused by pathogenic variants in the USH1C gene, leads to congenital deafness and progressive retinal degeneration resulting in vision loss. While auditory deficits can be compensated by cochlea implants and hearing aids, no treatment exists to prevent retinal degeneration. Here, we generated retinal organoids from induced pluripotent stem cells of two USH1C patients to elucidate the cellular and molecular mechanisms driving ocular pathogenesis. Single-cell RNA sequencing of both healthy and USH1C retinal organoids identified differential expression of genes related to phototransduction in photoreceptors, as well as alterations in cell adhesion and canonical Wnt signaling in Mueller glia cells. Analysis of intercellular communication revealed an overall reduced signaling efficiency, particularly affecting Mueller glia-mediated retinal adhesion processes. Morphological characterization of organoids confirmed transcriptome changes by showing degeneration of the outer limiting membrane and loss of adherens junction architecture. Moreover, photoreceptors revealed increased susceptibility to morphological and functional changes related to phototransduction. These results demonstrate that disruption of Mueller glia signaling contributes to a loss of retinal integrity, providing novel insights into USH1C pathogenesis and offering targets for therapeutic interventions.