A human model of Batten disease shows role of CLN3 in phagocytosis at the photoreceptor-RPE interface

Mutations in CLN3 lead to photoreceptor cell loss in CLN3 disease, a lysosomal storage disorder characterized by childhood-onset vision loss, neurological impairment, and premature death. However, how CLN3 mutations cause photoreceptor cell death is not known. Here, we show that CLN3 is required for phagocytosis of photoreceptor outer segment (POS) by retinal pigment epithelium (RPE) cells, a cellular process essential for photoreceptor survival. Specifically, a proportion of CLN3 in human, mouse, and iPSC-RPE cells localized to RPE microvilli, the site of POS phagocytosis. Furthermore, patient-derived CLN3 disease iPSC-RPE cells showed decreased RPE microvilli density and reduced POS binding and ingestion. Notably, POS phagocytosis defect in CLN3 disease iPSC-RPE cells could be rescued by wild-type CLN3 gene supplementation. Altogether, these results illustrate a novel role of CLN3 in regulating POS phagocytosis and suggest a contribution of primary RPE dysfunction for photoreceptor cell loss in CLN3 disease that can be targeted by gene therapy. CLN3 disease is characterised by childhood-onset vision loss and premature death. Using patient-derived retinal cells, the authors show that CLN3 is required for retinal pigment epithelium (RPE) cell structure, microvilli and phagocytosis of photoreceptor outer segments that are essential for vision. They further suggest that gene-therapy targeting RPE cells can be effective for CLN3 disease.

Automated summary

Mutations in CLN3 lead to photoreceptor cell loss in CLN3 disease, affecting the phagocytosis of photoreceptor outer segments by retinal pigment epithelium (RPE) cells. Patient-derived cells show that CLN3 is essential for RPE cell structure and phagocytosis, suggesting potential for gene therapy targeting RPE cells in treating CLN3 disease.