Batten disease (JNCL) is linked to disturbances in mitochondrial, cytoskeletal, and synaptic compartments

Abstract

Intracellular pathways leading to neuronal degeneration are poorly understood in the juvenile neuronal ceroid lipofuscinosis (JNCL, Batten disease), caused by mutations in the CLN3 gene. To elucidate the early pathology, we carried out comparative global transcript profiling of the embryonic, primary cultures of the Cln3-/- mouse neurons. Statistical and functional analyses delineated three major cellular pathways or compartments affected: mitochondrial glucose metabolism, cytoskeleton, and synaptosome. Further functional studies showed a slight mitochondrial dysfunction and abnormalities in the microtubule cytoskeleton plus-end components. Synaptic dysfunction was also indicated by the pathway analysis, and by the gross upregulation of the G protein beta 1 subunit, known to regulate synaptic transmission via the voltage-gated calcium channels. Intracellular calcium imaging showed a delay in the recovery from depolarization in the Cln3-/- neurons, when the N-type Ca2+ channels had been blocked. The data suggests a link between the mitochondrial dysfunction and cytoskeleton-mediated presynaptic inhibition, thus providing a foundation for further investigation of the disease mechanism underlying JNCL disease.

Analysis of Potential Biomarkers and Modifier Genes Affecting the Clinical Course of CLN3 Disease

“…The mRNA expression of another member of the dual-specificity phosphatases group, DUSP7, was increased 1.7-fold in embryonic, primary neuron cultures of Cln3-deficient mice in comparison with control neuronal cells (23). These data support our findings and suggest members of the DUSP family as likely candidates linked to CLN3 deficiency.…”

“…RAPGEF1 protein plays a role in multiple signal transduction pathways that regulate growth, differentiation and neuronal migration processes during brain development (23,25,26). RapGef1-deficient mouse embryos exhibit a cortical neuron migration defect resulting in a failure to split the preplate into marginal zone and subplate and a failure to form a cortical plate (27).…”

Unbiased Cell-based Screening in a Neuronal Cell Model of Batten Disease Highlights an Interaction between Ca2+ Homeostasis, Autophagy, and CLN3 Protein Function

“…In addition to this link between CLN3 function and Ca 2ϩ , pharmacological studies in CLN3 siRNA knockdown SH-SY5Y cells have also implicated a potential involvement of Ca 2ϩ in neuronal cell death due to CLN3 loss (36,58). A delayed recovery of intracellular Ca 2ϩ levels was also reported following inhibition of N-type Ca 2ϩ channels in depolarized primary cortical neurons isolated from Cln3 knock-out mice (59). Notably, we did not observe a significantly altered sensitivity to cell death of the CbCln3 ⌬ex7/8/⌬ex7/8 cells to low dose thapsigargin treatment compared with wild type cells, perhaps due to the changes we observed in the other intracellular Ca 2ϩ stores, which may serve to protect the cells from Ca 2ϩ -mediated excitotoxicity.…”

A Knock-In Reporter Model of Batten Disease

“…Other studies with human fibroblasts indicate CLN3 involvement in lysosomal pH maintenance and degradation (Golabek et al, 2000) and endocytosis (Luiro et al, 2004). Cells derived from Cln3 ⌬ex7/8 mice display defects in endosome-to-lysosome vesicular trafficking and mitochondrial function (Fossale et al, 2004), and microarray analysis of neurons from Cln3 ⌬ex7/8 mice reveals altered levels of transcripts coding for proteins involved in synaptic, cytoskeletal, and metabolic functions (Luiro et al, 2006). In addition, a recent study indicates that CLN3 may impact palmitoyl desaturation (Narayan et al, 2006).…”