Deficient mitochondrial Ca 2+ buffering in the Cln8mnd mouse model of neuronal ceroid lipofuscinosis

Abstract

Neuronal ceroid lipofuscinoses (NCLs) are a group of genetic childhood-onset progressive brain diseases characterized by a decline in mental and motor capacities, epilepsy, visual loss and premature death. Using patch clamp, fluorescence imaging and caged Ca 2+ photolysis, we evaluated the mechanisms of neuronal Ca 2+ clearance in Cln8 mnd mice, a model of the human NCL caused by mutations in the CLN8 gene. In Cln8 mnd hippocampal slices, Ca 2+ clearance efficiency in interneurons and, to some extent, principal neurons declined with age. In cultured Cln8 mnd hippocampal neurons, clearance of large Ca 2+ loads was inefficient due to impaired mitochondrial Ca 2+ uptake. In contrast, neither Ca 2+ uptake by sarco/endoplasmic reticulum Ca 2+ ATPase, nor Ca 2+ extrusion through plasma membrane was affected by the Cln8 mutation. Excitotoxic glutamate challenge caused Ca 2+ deregulation more readily in Cln8 mnd than in wt neurons. We propose that neurodegeneration in human CLN8 disorders is primarily caused by reduced mitochondrial Ca 2+ buffering capacity.