Jonathan D. Cooper

Failed retrograde transport of NGF in a mouse model of Down's syndrome: Reversal of cholinergic neurodegenerative phenotypes following NGF infusion

Age-related degeneration of basal forebrain cholinergic neurons (BFCNs) contributes to cognitive decline in Alzheimers disease and Downs syndrome. With aging, the partial trisomy 16 (Ts65Dn) mouse model of Downs syndrome exhibited reductions in BFCN size and number and regressive changes in the hippocampal terminal fields of these neurons with respect to diploid controls. The changes were associated with significantly impaired retrograde transport of nerve growth factor (NGF) from the hippocampus to the basal forebrain. Intracerebroventricular NGF infusion reversed well established abnormalities in BFCN size and number and restored the deficit in cholinergic innervation. The findings are evidence that even BFCNs chronically deprived of endogenous NGF respond to an intervention that compensates for defective retrograde transport. We suggest that age-related cholinergic neurodegeneration may be a treatable disorder of failed retrograde NGF signaling.

High resolution 1H NMR-based metabolomics indicates a neurotransmitter cycling deficit in cerebral tissue from a mouse model of Batten disease.

The neuronal ceroid lipofuscinoses (NCLs) constitute a range of progressive neurological disorders primarily affecting children. Although six of the causative genes have been characterized, the underlying disease pathogenesis for this family of disorders is unknown. Using a metabolomics approach based on high resolution 1H NMR spectroscopy of the cortex, cerebellum, and remaining regions of the brain in conjunction with statistical pattern recognition, we report metabolic deficits associated with juvenile NCL in a Cln3 knock-out mouse model. Tissue from Cln3 null mutant mice aged 1–6 months was characterized by an increased glutamate concentration and a decrease in γ-amino butyric acid (GABA) concentration in aqueous extracts from the three regions of the brain. These changes are consistent with the reported altered expression of genes involved in glutamate metabolism in older mice and imply a change in neurotransmitter cycling between glutamate/glutamine and the production of GABA. Further variations in myo-inositol, creatine, and N-acetyl-aspartate were also identified. These metabolic changes were distinct from the normal aging/developmental process. Together, these changes represent the first documented pre-symptomatic symptoms of the Cln3 mouse at 1 month of age and demonstrate the versatility of 1H NMR spectroscopy as a tool for phenotyping mouse models of disease.

Projections to the rostral reticular thalamic nucleus in the rat

SummaryAfferent pathways to the rostral reticular thalamic nucleus (Rt) in the rat were studied using anterograde and retrograde lectin tracing techniques, with sensitive immunocytochemical methods. The analysis was carried out to further investigate previously described subregions of the reticular thalamic nucleus, which are related to subdivisions of the dorsal thalamus, in the paraventricular and midline nuclei and three segments of the mediodorsal thalamic nucleus. Cortical inputs to the rostral reticular nucleus were found from lamina VI of cingulate, orbital and infralimbic cortex. These projected with a clear topography to lateral, intermediate and medial reticular nucleus respectively. Thalamic inputs were found from lateral and central segments of the mediodorsal nucleus to the lateral and intermediate rostral reticular nucleus respectively and heavy paraventricular thalamic inputs were found to the medial reticular nucleus. In the basal forebrain, afferents were found from the vertical and horizontal limbs of the diagonal band, substantia innominata, ventral pallidum and medial globus pallidus. Brainstem projections were identified from ventrolateral periaqueductal grey and adjacent sites in the mesencephalic reticular formation, laterodorsal tegmental nucleus, pedunculopontine nucleus, medial pretectum and ventral tegmental area. The results suggest a general similarity in the organisation of some brainstem Rt afferents in rat and cat, but also show previously unsuspected inputs. Furthermore, there appear to be at least two functional subdivisions of rostral Rt which is reflected by their connections with cortex and thalamus. The studies also extend recent findings that the ventral striatum, via inputs from the paraventricular thalamic nucleus, is included in the circuitry of the rostral Rt, providing further evidence that basal ganglia may function in concert with Rt. Evidence is also outlined with regard to the possibility that rostral Rt plays a significant role in visuomotor functions.

Late onset neurodegeneration in the Cln3−/− mouse model of juvenile neuronal ceroid lipofuscinosis is preceded by low level glial activation

Mouse models of neuronal ceroid lipofuscinosis (NCL) exhibit many features of the human disorder, with widespread regional atrophy and significant loss of GABAergic interneurons in the hippocampus and neocortex. Reactive gliosis is a characteristic of all forms of NCL, but it is unclear whether glial activation precedes or is triggered by neuronal loss. To explore this issue we undertook detailed morphological characterization of the Cln3 null mutant (Cln3(-/-)) mouse model of juvenile NCL (JNCL) that revealed a delayed onset neurodegenerative phenotype with no significant regional atrophy, but with widespread loss of hippocampal interneurons that was first evident at 14 months of age. Quantitative image analysis demonstrated upregulation of markers of astrocytic and microglial activation in presymptomatic Cln3(-/-) mice at 5 months of age, many months before significant neuronal loss occurs. These data provide evidence for subtle glial responses early in JNCL pathogenesis.

Risk of microalbuminuria and progression to macroalbuminuria in a cohort with childhood onset type 1 diabetes: prospective observational study

Objectives To describe independent predictors for the development of microalbuminuria and progression to macroalbuminuria in those with childhood onset type 1 diabetes. Design Prospective observational study with follow-up for 9.8 (SD 3.8) years. Setting Oxford regional prospective study. Participants 527 participants with a diagnosis of type 1 diabetes at mean age 8.8 (SD 4.0) years. Main outcome measures Annual measurement of glycated haemoglobin (HbA1c) and assessment of urinary albumin:creatinine ratio. Results Cumulative prevalence of microalbuminuria was 25.7% (95% confidence interval 21.3% to 30.1%) after 10 years of diabetes and 50.7% (40.5% to 60.9%) after 19 years of diabetes and 5182 patient years of follow-up. The only modifiable adjusted predictor for microalbuminuria was high HbA1c concentrations (hazard ratio per 1% rise in HbA1c 1.39, 1.27 to 1.52). Blood pressure and history of smoking were not predictors. Microalbuminuria was persistent in 48% of patients. Cumulative prevalence of progression from microalbuminuria to macroalbuminuria was 13.9% (12.9% to 14.9%); progression occurred at a mean age of 18.5 (5.8) years. Although the sample size was small, modifiable predictors of macroalbuminuria were higher HbA1c levels and both persistent and intermittent microalbuminuria (hazard ratios 1.42 (1.22 to 1.78), 27.72 (7.99 to 96.12), and 8.76 (2.44 to 31.44), respectively). Conclusion In childhood onset type 1 diabetes, the only modifiable predictors were poor glycaemic control for the development of microalbuminuria and poor control and microalbuminuria (both persistent and intermittent) for progression to macroalbuminuria. Risk for macroalbuminuria is similar to that observed in cohorts with adult onset disease but as it occurs in young adult life early intervention in normotensive adolescents might be needed to improve prognosis.

Intraventricular Enzyme Replacement Improves Disease Phenotypes in a Mouse Model of Late Infantile Neuronal Ceroid Lipofuscinosis

Late infantile neuronal ceroid lipofuscinosis (LINCL) is an autosomal recessive neurodegenerative disease caused by mutations in CLN2, which encodes the lysosomal protease tripeptidyl peptidase 1 (TPP1). LINCL is characterized clinically by progressive motor and cognitive decline, and premature death. Enzyme-replacement therapy (ERT) is currently available for lysosomal storage diseases affecting peripheral tissues, but has not been used in patients with central nervous system (CNS) involvement. Enzyme delivery through the cerebrospinal fluid is a potential alternative route to the CNS, but has not been studied for LINCL. In this study, we identified relevant neuropathological and behavioral hallmarks of disease in a mouse model of LINCL and correlated those findings with tissues from LINCL patients. Subsequently, we tested if intraventricular delivery of TPP1 to the LINCL mouse was efficacious. We found that infusion of recombinant human TPP1 through an intraventricular cannula led to enzyme distribution in several regions of the brain of treated mice. In vitro activity assays confirm increased TPP1 activity throughout the rostral-caudal extent of the brain. Importantly, treated mice showed attenuated neuropathology, and decreased resting tremor relative to vehicle-treated mice. This data demonstrates that intraventricular enzyme delivery to the CNS is feasible and may be of therapeutic value.

Reduced transport of [125I]nerve growth factor by cholinergic neurons and down-regulated trka expression in the medial septum of aged rats

Basal forebrain cholinergic neurons atrophy and degenerate in aging and Alzheimers disease for unknown reasons. In this study, aged male Sprague-Dawley rats (26-30 months old) showed a significant 31% reduction in the number of septal cholinergic neurons which take up and retrogradely transport 125I-labelled nerve growth factor injected into their target hippocampus, as compared with young adult rats (three to six months old). In aged rats, cholinergic neurons not transporting nerve growth factor were severely atrophied and had a significant 60% reduction in mean cross-sectional area as compared with [125I]nerve growth factor transporting neurons. These changes were accompanied by a significant 43% decline in relative levels of messenger RNA encoding the high affinity nerve growth factor receptor TrkA, in the septal region of aged rats. There was no difference between young and aged rats in messenger RNA levels encoding the low affinity nerve growth factor receptor, p75NGFR. These findings suggest that aged basal forebrain cholinergic neurons exhibit a reduced capacity to sustain receptor mediated uptake and retrograde transport of target-derived neurotrophin. This reduced capacity is associated with severe neuronal atrophy and may contribute to the pronounced vulnerability of these neurons to degeneration in aging and Alzheimers disease.

Regulation of Btk by Src family tyrosine kinases.

Loss of function of Brutons tyrosine kinase (Btk) results in X-linked immunodeficiencies characterized by a broad spectrum of signaling defects, including those dependent on Src family kinase-linked cell surface receptors. A gain-of-function mutant, Btk*, induces the growth of fibroblasts in soft agar and relieves the interleukin-5 dependence of a pre-B-cell line. To genetically define Btk signaling pathways, we used a strategy to either activate or inactivate Src family kinases in fibroblasts that express Btk*. The transformation potential of Btk* was dramatically increased by coexpression with a partly activated c-Src mutant (E-378 --> G). This synergy was further potentiated by deletion of the Btk Src homology 3 domain. Downregulation of Src family kinases by the C-terminal Src kinase (Csk) suppressed Btk* activation and biological potency. In contrast, kinase-inactive Csk (K-222 --> R), which functioned as a dominant negative molecule, synergized with Btk* in biological transformation. Activation of Btk* correlated with increased phosphotyrosine on transphosphorylation and autophosphorylation sites. These findings suggest that the Src and Btk kinase families form specific signaling units in tissues in which both are expressed.

Neuroprotection of Host Cells by Human Central Nervous System Stem Cells in a Mouse Model of Infantile Neuronal Ceroid Lipofuscinosis

Infantile neuronal ceroid lipofuscinosis (INCL) is a fatal neurodegenerative disease caused by a deficiency in the lysosomal enzyme palmitoyl protein thioesterase-1 (PPT1). Ppt1 knockout mice display hallmarks of INCL and mimic the human pathology: accumulation of lipofuscin, degeneration of CNS neurons, and a shortened life span. Purified non-genetically modified human CNS stem cells, grown as neurospheres (hCNS-SCns), were transplanted into the brains of immunodeficient Ppt1(-/)(-) mice where they engrafted robustly, migrated extensively, and produced sufficient levels of PPT1 to alter host neuropathology. Grafted mice displayed reduced autofluorescent lipofuscin, significant neuroprotection of host hippocampal and cortical neurons, and delayed loss of motor coordination. Early intervention with cellular transplants of hCNS-SCns into the brains of INCL patients may supply a continuous and long-lasting source of the missing PPT1 and provide some therapeutic benefit through protection of endogenous neurons. These data provide the experimental basis for human clinical trials with these banked hCNS-SCns.

Progress towards understanding the neurobiology of Batten disease or neuronal ceroid lipofuscinosis

Purpose of reviewThe identification of genes mutated in the neuronal ceroid lipofuscinoses has accelerated research into the mechanisms that underlie these fatal autosomal recessive storage disorders, which are often referred to as Batten disease. This review summarizes progress in this field since October 2001, describing advances in cell biology, the characterization of new animal models of neuronal ceroid lipofuscinosis, and the impact of novel methodology to reveal insights into its pathogenesis. Recent findingsGene products for six of the eight forms of neuronal ceroid lipofuscinosis have now been discovered, and concerted efforts are underway to understand the normal biology of each gene product and how this may be altered by mutation. Several lines of evidence point to functions for the CLN genes in the endosomal-lysosomal system, and suggest neuron-specific roles for these proteins. Indeed, a requirement for appropriate protein trafficking within neurons may explain the profound and selective effects of these disorders upon the central nervous system. The development of mouse and large animal models has enabled comparative studies of the progressive effects of disease, including characterization by morphological and biochemical means supplemented by metabonomic and microarray techniques. SummaryInsights into disease mechanisms are building a detailed profile of the impact of neuronal ceroid lipofuscinosis upon the brain. With the eventual aim of developing successful therapeutic strategies, it will be equally important to characterize the clinical progression of the disorder, and to identify quantifiable endpoints that can ultimately be used in clinical trials.