Abstract
Purpose :
Usher Syndrome is a recessive disease resulting in blindness, deafness, and in some cases vestibular dysfunction. Besides cochlear implants that can restore hearing, no treatments are available for the progressive retinitis pigmentosa that ensues. Here, we investigate Usher1 syndrome – the most severe subtype. More specifically, Usher1f which is encoded by the PCDH15 gene. Owing to the inherent complexity of the retina, cochlear and vestibular system, studying Usher1f pathophysiology has proven difficult in both in vitro and in vivo systems.
Methods :
To characterise the pathology of this disease, we use retinal organoids derived from patient induced pluripotent stem cells (iPSCs) and isogenic control lines. Single cell RNA sequencing (ScRNA-seq) was performed on 30-week-old retinal Usher1f and wild-type organoids.
Results :
Usher1f retinal organoids displayed a reduction in the number of cone and rod photoreceptor cells relative to wild-type. Interestingly, diseased organoids also displayed a higher proportion of Müller glia cells. Encouraging genes implicated in retinitis pigmentosa were significantly upregulated in Usher1f in cone and rod cell populations. Mitochondrial oxidative stress was also found to be implicated in Usher1f and genes involved in maintenance and survival of photoreceptor cells were also upregulated, particularly within the connecting cilium region, where PCHD15 is known to localise. Interestingly, these Usher1f photoreceptor cells also displayed an upregulation of genes involved in the phototransduction pathway. Validation studies are ongoing, and investigation of other pathways involved in development and pathology will provide further insight into Usher’s disease.
Conclusions :
This study promises to elucidate previously unknown phenotypic Usher1f mechanisms. Future studies will include investigating novel biomarkers identified in this study and testing of gene therapeutic methods using viral and non-viral methods.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.