Compromised astrocyte function and survival negatively impact neurons in infantile neuronal ceroid lipofuscinosis

Abstract

The neuronal ceroid lipofuscinoses (NCLs) are the most common cause of childhood dementia and are invariably fatal. Early localized glial activation occurs in these disorders, and accurately predicts where neuronal loss is most pronounced. Recent evidence suggests that glial dysfunction may contribute to neuron loss, and we have now explored this possibility in infantile NCL (INCL, CLN1 disease). We grew primary cultures of astrocytes, microglia, and neurons derived from Ppt1 deficient mice (Ppt1−/−) and assessed their properties compared to wildtype (WT) cultures, before co-culturing them in different combinations (astrocytes with microglia, astrocytes or microglia with neurons, all three cell types together). These studies revealed that both Ppt1−/− astrocytes and microglia exhibit a more activated phenotype under basal unstimulated conditions, as well as alterations to their protein expression profile following pharmacological stimulation. Ppt1- /− astrocytes also displayed abnormal calcium signalling and an elevated cytoplasmic Ca2+ level, and a profound defect in their survival. Ppt1−/− neurons displayed decreased neurite outgrowth, altered complexity, a reduction in cell body size, and impaired neuron survival with prolonged time in culture. In co-cultures, the presence of both astrocytes and microglia from Ppt1−/− mice further impaired the morphology of both wild type and Ppt1−/− neurons. This negative influence was more pronounced for Ppt1−/− microglia, which appeared to trigger increased Ppt1−/− neuronal death. In contrast, wild type glial cells, especially astrocytes, ameliorated some of the morphological defects observed in Ppt1−/− neurons. These findings suggest that both Ppt1−/− microglia and astrocytes are dysfunctional and may contribute to the neurodegeneration observed in CLN1 disease. However, the dysfunctional phenotypes of Ppt1−/− glia are different from those present in CLN3 disease, suggesting that the pathogenic role of glia may differ between NCLs.Electronic supplementary materialThe online version of this article (10.1186/s40478-018-0575-4) contains supplementary material, which is available to authorized users.

Neuroinflammation and progressive myoclonus epilepsies: from basic science to therapeutic opportunities

“…Therefore the primary cause of NCL-CLN3 disease is an alteration of the functionality of the astrocytes rather than a problem at the neuronal level. Similar results were reported recently in another model of NCL, carrying a defective CLN1 gene (OMIM #256730) (Ref 45)…”

Clinical challenges and future therapeutic approaches for neuronal ceroid lipofuscinosis

“…2,40 In adult onset NCLs, brain atrophy is less obvious. 2,40 Pronounced microglial and astrocytic activation precedes and per haps causes neuron loss, 19,41,42 accurately predicting its dis tribution. 41 Brain atrophy of the cerebral cortex and enlargement of the subarachnoid space and ventricles progresses throughout the disease.…”

“…19 Mice that are genetically modified or have spontaneous mutations exist for all NCL genes, 5,46 and their char acterisation has provided insights into the staging of neuropathological changes. 6,7 This has revealed differences in the extent, timing, and nature of changes 41,42 despite leading to a similar pathological endpoint. The spinal cord has been identi fied as exhibiting important patho logy, including loss of neurons, activation of microglia, and buildup of lipo pigment storage in Cln1 mice, 47 with impairments of the peri pheral nervous system evi dent resembling paroxysmal sympathetic hyperactivity in juvenile CLN3 disease.…”

Neuropathophysiology of Lysosomal Storage Diseases: Synaptic Dysfunction as a Starting Point for Disease Progression

“…In the neuron-specific GCase knockout mouse model of Gaucher disease (Gba flox/flox(Nestin-Cre) ) astrogliosis as observed at P10 in layer V of cerebral cortex, lateral globus pallidus, and thalamic nuclei preceding the neuronal loss occurring at P14 [46]. Co-culturing wild-type primary mouse neurons with astrocytes and glia from a mouse model of CLN1 (Ppt1 -/-), resulted in abnormal Ca 2+ signaling, decreased neurite outgrowth and impaired neuronal survival [47]. However, culturing mutant neurons with healthy glia reversed the phenotype [48].…”