title: Photoreceptor phagosome processing defects and disturbed autophagy in retinal pigment epithelium of Cln3Δex1-6 mice modelling juvenile neuronal ceroid lipofuscinosis (Batten disease).
abstract: Retinal degeneration and visual impairment are the first signs of juvenile neuronal ceroid lipofuscinosis caused by CLN3 mutations, followed by inevitable progression to blindness. We investigated retinal degeneration in Cln3(Δex1-6) null mice, revealing classic 'fingerprint' lysosomal storage in the retinal pigment epithelium (RPE), replicating the human disease. The lysosomes contain mitochondrial F0-ATP synthase subunit c along with undigested membranes, indicating a reduced degradative capacity. Mature autophagosomes and basal phagolysosomes, the terminal degradative compartments of autophagy and phagocytosis, are also increased in Cln3(Δex1) (-6) RPE, reflecting disruption to these key pathways that underpin the daily phagocytic turnover of photoreceptor outer segments (POS) required for maintenance of vision. The accumulated autophagosomes have post-lysosome fusion morphology, with undigested internal contents visible, while accumulated phagosomes are frequently docked to cathepsin D-positive lysosomes, without mixing of phagosomal and lysosomal contents. This suggests lysosome-processing defects affect both autophagy and phagocytosis, supported by evidence that phagosomes induced in Cln3(Δex1) (-) (6)-derived mouse embryonic fibroblasts have visibly disorganized membranes, unprocessed internal vesicles and membrane contents, in addition to reduced LAMP1 membrane recruitment. We propose that defective lysosomes in Cln3(Δex1) (-) (6) RPE have a reduced degradative capacity that impairs the final steps of the intimately connected autophagic and phagocytic pathways that are responsible for degradation of POS. A build-up of degradative organellar by-products and decreased recycling of cellular materials is likely to disrupt processes vital to maintenance of vision by the RPE.
authors.affiliation: UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK, Molecular Medicine, National Heart and Lung Institute, Imperial College London, London SW7 2AZ, UK.
authors.forename: Silène T
authors.initials: ST
authors.lastname: Wavre-Shapton
authors.affiliation: Nuclear Dynamics and Architecture, Institute of Medical Biology, Singapore 138648, Singapore.
authors.forename: Alessandra A
authors.initials: AA
authors.lastname: Calvi
authors.affiliation: Faculty of Life Sciences, Division of Biosciences and.
authors.forename: Mark
authors.initials: M
authors.lastname: Turmaine
authors.affiliation: Molecular Medicine, National Heart and Lung Institute, Imperial College London, London SW7 2AZ, UK.
authors.forename: Miguel C
authors.initials: MC
authors.lastname: Seabra
authors.affiliation: Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK and MRC Cell Biology Unit, MRC Laboratory for Molecular Cell Biology, London, UK.
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Cutler
authors.affiliation: UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK, h.mitchison@ucl.ac.uk c.futter@ucl.ac.uk.
authors.forename: Clare E
authors.initials: CE
authors.lastname: Futter
authors.affiliation: Genetics and Genomic Medicine Programme and Birth Defects Research Centre, Institute of Child Health, University College London, London WC1N 1EH, UK, h.mitchison@ucl.ac.uk c.futter@ucl.ac.uk.
authors.forename: Hannah M
authors.initials: HM
authors.lastname: Mitchison
mesh_terms: D000375:Aging; D000818:Animals; D001343:Autophagy; D001921:Brain / Q000473:pathology; D004195:Disease Models, Animal; D008247:Lysosomes / Q000378:metabolism; D008561:Membrane Fusion; D008562:Membrane Glycoproteins / Q000172:deficiency* / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008863:Microspheres; D025261:Mitochondrial Proton-Translocating ATPases / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics; D009472:Neuronal Ceroid-Lipofuscinoses / Q000378:metabolism / Q000503:physiopathology*; D009474:Neurons / Q000473:pathology; D010588:Phagosomes / Q000378:metabolism*; D055213:Retinal Pigment Epithelium / Q000378:metabolism / Q000503:physiopathology*
chemical_list: C102229:CLN3 protein, mouse; D008562:Membrane Glycoproteins; D018832:Molecular Chaperones; D025261:Mitochondrial Proton-Translocating ATPases