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 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 Müller glia cells. Analysis of intercellular communication revealed an overall reduced signaling efficiency, particularly affecting Müller 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 levels of apoptosis, as well as morphological and functional changes related to phototransduction. Our results demonstrate that disruption of Müller glia signaling contributes to an overall loss of retinal integrity, providing novel insights into USH1C pathogenesis and offering targets for therapeutic interventions.
Nicole Wenck, Mark Zorin, Qiang Wang et al.· Cellular and Molecular Life...· 0 citations
Summary Inherited retinal diseases (IRDs) encompass a broad spectrum of genetic conditions leading to visual impairment. In this study, we identify KATNA1, encoding the catalytic p60 subunit of the microtubule-severing enzyme katanin, as a previously unrecognized cause of autosomal dominant macular dystrophy (adMD), a form of IRD. Specifically, we could ascertain the presence of 10 heterozygous missense changes affecting six conserved amino acids in 21 individuals from 16 unrelated families from various parts of the world, all presenting with non-syndromic MD of variable severity. Structure-guided analyses indicated that the identified variants potentially disrupt katanin’s assembly into hexamers or its ability to bind or hydrolyze ATP, thus compromising its microtubule-severing function. Characterization of patient-derived fibroblasts revealed accumulation of acetylated microtubules both in the cytoplasm and within the primary cilium, together with an altered subcellular distribution of KATNA1. Immunostaining of human retinal tissue showed that KATNA1 specifically localizes to photoreceptors, with distinct distribution patterns between rod and cone photoreceptors. Immunogold transmission electron microscopy confirmed this finding, revealing KATNA1 distribution along the rod axoneme and predominantly within the cone connecting cilium. Together, these results establish KATNA1 as a novel gene associated with adMD, possibly accounting for ~4% of all unresolved MD cases, and associate defective microtubule severing and cytoskeletal dysregulation with macular degeneration.
Carlo Rivolta, Karolina Kaminska, Abigail R. Moye et al.· Research Square· 0 citations
Findings further support AP5B1 as a cause of macular dystrophy, identify p.(Leu785Pro) as a relatively frequent pathogenic allele in individuals of European and Ashkenazi Jewish ancestry, and expand the associated phenotypic spectrum to include both isolated macular dystrophy and possible syndromic presentations.
Petra Liskova, L. Dudakova, Karolina Kaminska et al.· HGG advances· 0 citations