Distinct Early Molecular Responses to Mutations Causing vLINCL and JNCL Presage ATP Synthase Subunit c Accumulation in Cerebellar Cells

Variant late-infantile (vLINCL) and juvenile neuronal ceroid lipofuscinosis (JNCL) share clinical and pathological features, including lysosomal accumulation of mitochondrial ATP synthase subunit c, but the unrelated CLN6 and CLN3 genes may initiate disease via similar or distinct cellular processes. To gain insight into the NCL pathways, we established murine wild-type and vLINCL CbCln6nclf cerebellar cells and compared them to wild-type and JNCL CbCln3ex7/8 cerebellar cells. CbCln6nclf/nclf cells and CbCln3ex7/8/ex7/8 cells both displayed abnormally elongated mitochondria and reduced cellular ATP levels and, as cells aged to confluence, exhibited accumulation of subunit c protein in Lamp 1-positive organelles. However, at sub-confluence, endoplasmic reticulum PDI immunostain was decreased only in CbCln6nclf/nclf cells, while fluid-phase endocytosis and LysoTracker labeled vesicles were decreased in both CbCln6nclf/nclf and CbCln3ex7/8/ex7/8 cells, though only the latter cells exhibited abnormal vesicle subcellular distribution. Furthermore, unbiased gene expression analyses revealed only partial overlap in the cerebellar cell genes and pathways that were altered by the Cln3ex7/8 and Cln6nclf mutations. Thus, these data support the hypothesis that vLINCL and JNCL mutations trigger distinct processes that converge on a shared pathway, which is responsible for proper subunit c protein turnover and neuronal cell survival.

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Cao Y, Staropoli JF, Biswas S, Espinola JA, MacDonald ME, Lee JM, Cotman SL