Description
Purpose: Retinitis pigmentosa 54 (RP54) is a severe inherited retinal dystrophy caused by pathogenic variants in PCARE, which encodes the photoreceptor cilium actin regulator protein (PCARE), essential for the outer segment (OS) disc formation. To date, PCARE mutations have been reported in ~40 families, and no treatment exists. This study aims to define the pathogenic mechanisms underlying PCARE-related retinal degeneration and to establish patient-derived retinal models and a knockout mouse model (BC -/-) as platforms for future PCARE gene therapy.
Methods: A homozygous PCARE c.946delA (p.Asn237MetfsX5) hiPSC line from a patient with atypical RP54 and a control hiPSC line were differentiated into retinal organoids (ROs) and retinal pigment epithelium (RPE) cells. For in vivo studies, we used the BC027072 knockout mouse (referred to as BC -/-), which lacks the murine pcare homolog.
Results: RP54-hiPSCs maintained pluripotency and differentiated into all germ layers. RP54-RPE cells exhibited normal morphology but displayed dysregulated RPE-specific gene expression, suggesting functional defects. Early-stage RP54 ROs developed normally, but at later stages, ROs displayed aberrant OS structures and a disrupted external limiting membrane, mislocalization of PCARE, and abnormal retinal cell proliferation. BC-/- mice exhibited rapid and severe photoreceptor and retinal degeneration with markedly impaired light responses beginning at one month of age.
Conclusions: PCARE loss leads to profound structural and functional photoreceptor abnormalities in both hiPSC-derived retinal models and BC-/- mice. These models represent robust preclinical platforms for evaluating AAV-mediated PCARE gene therapy, which will be assessed in upcoming studies.
Lay Abstract
This poster presents work on retinitis pigmentosa 54 (RP54), a rare inherited eye disease that causes severe, progressive vision loss due to changes in a gene called PCARE. The PCARE protein is needed for disc neogenesis of photoreceptor cells in the retina; when PCARE is missing or faulty, these photoreceptors are degenerated, and there is currently no treatment.
To investigate how PCARE defects lead to retinal degeneration and to prepare for future gene therapy, we used two complementary disease models. First, we generated “mini‑retinas” (retinal organoids) and retinal pigment epithelium cells in the lab from a patient’s stem cells carrying a disease‑causing PCARE mutation and from a healthy control. Second, we studied a mouse that completely lacks the mouse version of PCARE, which develops retinal disease similar to human RP54. Together, these models offer powerful tools to uncover the disease mechanism and to test PCARE gene replacement strategies.
| Lay Title | Modelling PCARE-Associated Retinopathy in Human Retinal Organoids and a Mouse Model |
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| Role | PhD Student |