Disease-specific pathology in neurons cultured from sheep affected with ceroid lipofuscinosis.
The neuronal ceroid lipofuscinoses (NCL, Batten disease) are a group of inherited neurodegenerative storage diseases in children. Mutations in different genes underlie different forms. Subunit c of mitochondrial ATP synthase is specifically stored in autofluorescent bodies in most of them, including a form in sheep. Mature bodies are lysosomal but the initial site of storage is not known, nor is it known how this leads to the characteristic neurodegeneration. Neurons were cultured in serum-free medium from control and affected sheep fetuses at 90 days gestation. They showed positive microtubule-associated protein staining, developed neurites, and had typical neuron morphology. Time-dependent accumulation of subunit c and of fluorescent storage bodies was observed in affected cells by immunocytochemistry and confocal microscopy. A small number of autofluorescent bodies were apparent after 4 days in culture. After 10 days these bodies were more numerous, more intensely autofluorescent, and often larger in size. By 14 and 21 days many neurons were packed with autofluorescent material. These bodies were not seen in control cultures. Immunocytochemistry revealed subunit c-positive storage material only in affected neurons and not in affected glial cells. Confocal microscope analysis, using organelle-specific dyes, demonstrated colocalization of autofluorescent bodies with lysosomes, not with mitochondria. Survival rates of the affected cells were unaffected by the storage body accumulation over a 3-month period. These cultures can now be used to study the mechanism of subunit c accumulation and of neurodegeneration and to test therapeutic possibilities.