Attenuation of AMPA receptor activity improves motor skills in a mouse model of juvenile Batten disease

Neuropeptide changes and neuroactive amino acids in CSF from humans and sheep with neuronal ceroid lipofuscinoses (NCLs, Batten disease)

Anomalies in neuropeptides and neuroactive amino acids have been postulated to play a role in neurodegeneration in a variety of diseases including the inherited neuronal ceroid lipofuscinoses (NCLs, Batten disease). These are often indicated by concentration changes in cerebrospinal fluid (CSF). Here we compare CSF neuropeptide concentrations in patients with the classical juvenile CLN3 form of NCL and the classical late infantile CLN2 form with neuropeptide and neuroactive amino acid concentrations in CSF from sheep with the late infantile variant CLN6 form. A marked disease related increase in CSF concentrations of neuron specific enolase and tau protein was noted in the juvenile CLN3 patients but this was not observed in an advanced CLN2 patient nor CLN6 affected sheep. No changes were noted in S-100b, GFAP or MBP in patients or of S-100b, GFAP or IGF-1 in affected sheep. There were no disease related changes in CSF concentrations of the neuroactive amino acids, aspartate, glutamate, serine, glutamine, glycine, taurine and GABA in these sheep. The changes observed in the CLN3 patients may be progressive markers of neurodegeneration, or of underlying metabolic changes perhaps associated with CLN3 specific changes in neuroactive amino acids, as have been postulated. The lack of changes in the CLN2 and CLN6 subjects indicate that these changes are not shared by the CLN2 or CLN6 forms and changes in CSF concentrations of these compounds are unreliable as biomarkers of neurodegeneration in the NCLs in general.

The fission yeast model for the lysosomal storage disorder Batten disease predicts disease severity caused by mutations in CLN3

The function of the CLN3 protein, which is mutated in patients with the neurodegenerative lysosomal storage disorder Batten disease, has remained elusive since it was identified 13 years ago. Here, we exploited the Schizosaccharomyces pombe model to gain new insights into CLN3 function. We modelled all missense mutations of CLN3 in the orthologous protein Btn1p, as well as a series of targeted mutations, and assessed trafficking and the ability of the mutant proteins to rescue four distinct phenotypes of btn1Delta cells. Mutating the C-terminal cysteine residues of Btn1p caused it to be internalised into the vacuole, providing further evidence that this protein functions from pre-vacuole compartments. Mutations in the lumenal regions of the multi-spanning membrane protein, especially in the third lumenal domain which contains a predicted amphipathic helix, had the most significant impact on Btn1p function, indicating that these domains of CLN3 are functionally important. Only one mutant protein was able to rescue the cell curving phenotype (p.Glu295Lys), and since this mutation is associated with a very protracted disease progression, this phenotype could be used to predict the disease severity of novel mutations in CLN3. The ability to predict disease phenotypes in S. pombe confirms this yeast as an invaluable tool to understanding Batten disease.