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David A Pearce

Publications and source records attributed to David A Pearce.

At least 19 recordsLinked to original sources
PubMed2006

IgG entry and deposition are components of the neuroimmune response in Batten disease.

Patients and a mouse model of Batten disease, the juvenile form of neuronal ceroid lipofuscinosis (JNCL), raise autoantibodies against GAD65 and other brain-directed antigens. Here we investigate the adaptive component of the neuroimmune response. Cln3(-/-) mice have autoantibodies to GAD65 in their cerebrospinal fluid and elevated levels of brain bound immunoglobulin G (IgG). IgG deposition was found within human JNCL autopsy material, a feature that became more evident with increased age in Cln3(-/-) mice. The lymphocyte infiltration present in human and murine JNCL occurred late in disease progression, and was not capable of central/intrathecal IgG production. In contrast, we found evidence for an early systemic immune dysregulation in Cln3(-/-) mice. In addition evidence for a size-selective breach in the blood-brain barrier integrity in these mice suggests that systemically produced autoantibodies can access the JNCL central nervous system and contribute to a progressive inflammatory response.

Animals↗
PubMed2006

Maternal antibrain antibodies in autism.

Autism is a neurodevelopmental disorder of prenatal onset that is behaviorally defined. There is increasing evidence for systemic and neuroimmune mechanisms in children with autism. Although genetic factors are important, atypical prenatal maternal immune responses may also be linked to the pathogenesis of autism. We tested serum reactivity in 11 mothers and their autistic children, maternal controls, and several groups of control children, to prenatal, postnatal, and adult rat brain proteins, by immunoblotting. Similar patterns of reactivity to prenatal (gestational day 18), but not postnatal (day 8) or adult rat brain proteins were identified in autistic children, their mothers, and children with other neurodevelopmental disorders, and differed from mothers of normal children, normal siblings of children with autism and normal child controls. Specific patterns of antibody reactivity were present in sera from the autism mothers, from 2 to 18 years after the birth of their affected children and were unrelated to birth order. Immunoblotting using specific antigens for myelin basic protein (MBP) and glial acidic fibrillary protein (GFAP) suggests that these proteins were not targets of the maternal antibodies. The identification of specific serum antibodies in mothers of children with autism that recognize prenatally expressed brain antigens suggests that these autoantibodies could cross the placenta and alter fetal brain development.

Adolescent↗
PubMed2006

Characterizing pathogenic processes in Batten disease: use of small eukaryotic model systems.

The neuronal ceroid lipofuscinoses (NCLs) are neurodegenerative disorders. Nevertheless, small model organisms, including those lacking a nervous system, have proven invaluable in the study of mechanisms that underlie the disease and in studying the functions of the conserved proteins associated to each disease. From the single-celled yeast, Saccharomyces cerevisiae and Schizosaccharomyces pombe, to the worm, Caenorhabditis elegans and the fruitfly, Drosophila melanogaster, biochemical and, in particular, genetic studies on these organisms have provided insight into the NCLs.

Amino Acid Sequence↗
PubMed2006

Homogeneous PCR nucleobase quenching assays to detect four mutations that cause neuronal ceroid lipofuscinosis: T75P and R151X in CLN1, and IVS5-1G>C and R208X in CLN2.

The neuronal ceroid lipofuscinoses (NCLs) are a family of autosomal recessive lysosomal storage diseases characterized by progressive epilepsy, dementia and visual loss. The juvenile form of the disease (onset age 4-8 years with visual loss) is usually caused by mutations in the CLN3 gene, but some cases have been shown to be due to specific mutations in the CLN1 or CLN2 genes, which are usually associated with NCL with onset in infancy or late infancy, respectively. The CLN1 mutations T75P and R151X, and the CLN2 mutations R208X and IVS5-1G>C, are found in many NCL patients with a juvenile presentation that is not due to CLN3 mutation. We have developed and validated a set of assays for these mutations using PCR followed by differential melting of a fluorescently labeled oligo probe, on a Roche LightCycler platform. The nucleobase quenching phenomenon was used to detect probe hybridization. The tests were validated using alternate assays: PCR followed by allele specific restriction enzyme digestion for the CLN1 mutations, and PCR followed by sequencing for the CLN2 mutations. The homogeneous PCR method gave 100% concordance of results with the alternate methods. This new assay, combined with a test for the common 1 kbp deletion in the CLN3 gene, provides a set of DNA-based assays suitable for detection of the most common mutations causing NCL with onset in the juvenile age range.

Aminopeptidases↗
PubMed2006

Selectively increased sensitivity of cerebellar granule cells to AMPA receptor-mediated excitotoxicity in a mouse model of Batten disease.

Batten disease, a lysosomal storage disorder, is caused by mutations in the CLN3 gene. The Cln3-knockout (Cln3-/-) mouse model of the disease exhibits many characteristic pathological features of the human disorder. Here, we show that Cln3-/- mice, similarly to Batten disease patients, have a deficit in cerebellar motor coordination. To explore the possible cellular cause of this functional impairment, we compared the vulnerability of wild type (WT) and Cln3-/- cerebellar granule cell cultures to different toxic insults. We have found that cultured Cln3-/- cerebellar granule cells are selectively more vulnerable to AMPA-type glutamate receptor-mediated toxicity than their WT counterparts. This selective sensitivity was also observed in organotypic cerebellar slice cultures. Our results suggest that lack of the CLN3 protein has a significant influence on the function of AMPA receptors in cerebellar granule neurons, and that AMPA receptor dysregulation may be a major contributor to the cerebellar dysfunction in Batten disease.

Animals↗
PubMed2006

You say lipofuscin, we say ceroid: defining autofluorescent storage material.

Accumulation of intracellular autofluorescent material or "aging pigment" has been characterized as a normal aging event. Certain diseases also exhibit a similar accumulation of intracellular autofluorescent material. However, autofluorescent storage material associated with aging and disease has distinct characteristics. Lipofuscin is a common term for aging pigments, whereas ceroid is used to describe pathologically derived storage material, for example, in the neuronal ceroid lipofuscinoses (NCLs). NCLs are a family of neurodegenerative diseases that are characterized by an accumulation of autofluorescent storage material (ceroid) in the lysosome, which has been termed "lipofuscin-like". There have been many studies that describe this autofluorescent storage material, but what is it? Is this accumulation lipofuscin or ceroid? In this review we will try to answer the following questions: (1) What is lipofuscin and ceroid? (2) What contributes to the accumulation of this storage material in one or the other? (3) Does this material have an effect on cellular function? Studying parallels between the accumulation of lipofuscin and ceroid may provide insight into the biological relevance of these phenomena.

Aging↗
PubMed2006

Visual deficits in a mouse model of Batten disease are the result of optic nerve degeneration and loss of dorsal lateral geniculate thalamic neurons.

Juvenile neuronal ceroid lipofuscinosis (JNCL) is an autosomal recessive disorder of childhood caused by mutations in CLN3. Although visual deterioration is typically the first clinical sign to manifest in affected children, loss of Cln3 in a mouse model of JNCL does not recapitulate this retinal deterioration. This suggests that either the loss of CLN3 does not directly affect retinal cell survival or that nuclei involved in visual processing are affected prior to retinal degeneration. Having previously demonstrated that Cln3(-/-) mice have decreased optic nerve axonal density, we now demonstrate a decrease in nerve conduction. Examination of retino-recipient regions revealed a decreased number of neurons within the dorsal lateral geniculate nucleus (LGNd). We demonstrate decreased transport of amino acids from the retina to the LGN, suggesting an impediment in communication between the retina and projection nuclei. This study defines a novel path of degeneration within the LGNd, providing a mechanism for causation of JNCL visual deficits.

Animals↗
PubMed2006

Saccharomyces cerevisiae lacking Btn1p modulate vacuolar ATPase activity to regulate pH imbalance in the vacuole.

The vacuolar H(+)-ATPase (V-ATPase) along with ion channels and transporters maintains vacuolar pH. V-ATPase ATP hydrolysis is coupled with proton transport and establishes an electrochemical gradient between the cytosol and vacuolar lumen for coupled transport of metabolites. Btn1p, the yeast homolog to human CLN3 that is defective in Batten disease, localizes to the vacuole. We previously reported that Btn1p is required for vacuolar pH maintenance and ATP-dependent vacuolar arginine transport. We report that extracellular pH alters both V-ATPase activity and proton transport into the vacuole of wild-type Saccharomyces cerevisiae. V-ATPase activity is modulated through the assembly and disassembly of the V(0) and V(1) V-ATPase subunits located in the vacuolar membrane and on the cytosolic side of the vacuolar membrane, respectively. V-ATPase assembly is increased in yeast cells grown in high extracellular pH. In addition, at elevated extracellular pH, S. cerevisiae lacking BTN1 (btn1-Delta), have decreased V-ATPase activity while proton transport into the vacuole remains similar to that for wild type. Thus, coupling of V-ATPase activity and proton transport in btn1-Delta is altered. We show that down-regulation of V-ATPase activity compensates the vacuolar pH imbalance for btn1-Delta at early growth phases. We therefore propose that Btn1p is required for tight regulation of vacuolar pH to maintain the vacuolar luminal content and optimal activity of this organelle and that disruption in Btn1p function leads to a modulation of V-ATPase activity to maintain cellular pH homeostasis and vacuolar luminal content.

Adenosine Triphosphatases↗
PubMed2006

Chronic olanzapine treatment causes differential expression of genes in frontal cortex of rats as revealed by DNA microarray technique.

Recent emerging biochemical data indicate that several important neuroregulatory genes and proteins may be involved in the etiology of schizophrenia and bipolar disorder. Additionally, the same genes appear to be targets of several psychotropic medications that are used to treat these disorders. Recent DNA microarray studies show that genes involved in synaptic neurotransmission, signal transduction, and glutamate/GABA regulation may be differentially regulated in brains of subjects with schizophrenia. We hypothesized that chronic administration of olanzapine to rats would alter expression of various genes that may be involved in the etiology of schizophrenia and mood disorders. Rats were administered olanzapine (N=20, 2 mg/kg/day) or sterile saline intraperitoneally (N=20) daily for 21 days. Control and olanzapine-treated frontal cortices were analyzed using cDNA microarray technology. The results showed significant downregulation of 31 genes and upregulation of 38 genes by greater than two-fold in the drug-treated brains vs controls. Our results provide evidence for altered regulation of genes involved with signal transduction and cell communication, metabolism and energy pathways, transport, immune response, nucleic acid metabolism, and neuronal growth factors. Real-time quantitative RT-PCR analysis verified the direction and magnitude of change in six genes of interest: calbindin 3, homer 1, regulator of G-protein signaling (RGS) 2, pyruvate kinase, Reelin and insulin 2. Western blotting showed significant upregulation in protein products for Reelin 410 and Reelin 180 kDa and downregulation for NMDA3B and RGS2. Our results show for the first time that olanzapine causes changes in levels of several important genes that may be involved in the etiology and treatment of schizophrenia and other psychiatric disorders.

Animals↗
PubMed2006

Standardized assessment of behavior and adaptive living skills in juvenile neuronal ceroid lipofuscinosis.

We obtained information about the behavioral, psychiatric, and functional status of 26 children (13 males, 13 females) with juvenile neuronal ceroid lipofuscinosis (JNCL; mean age 12y 3mo [SD 3y 4mo]; range 6y 9mo to 18y 8mo). Twenty-five children had visual impairment and 18 were known to have a positive seizure history before enrollment. Parents completed the Child Behavior Checklist, Scales of Independent Behavior - Revised, and a structured interview to assess obsessive-compulsive symptoms. Participants exhibited a broad range of behavioral and psychiatric problems, rated as occurring frequently and/or as severe in more than half of the sample. Males and females did not differ with regard to the number of behavioral and psychiatric problems. Children were also limited in their ability to perform activities of daily living, including self-care, hygiene, socialization, and other age-appropriate tasks. Results provide a quantitative baseline for behavioral and psychiatric problems and functional level in JNCL, against which further decline can be measured. Longitudinal assessment of behavioral and psychiatric symptoms and functional abilities is continuing and will provide much-needed data on the natural history of JNCL.

Activities of Daily Living↗
PubMed2006

Channeling studies in yeast: yeast as a model for channelopathies?

Regulation of the concentration of ions within a cell is mediated by their specific transport and sequestration across cellular membranes. This regulation constitutes a major factor in the maintenance of correct cellular homeostasis, with the transport occurring through the action of a large number of different channel proteins localized to the plasma membrane as well as to various organelles. These ion channels vary in specificity from broad (cationic vs anionic) to highly selective (chloride vs sodium). Mutations in many of these channels result in a large number of human diseases, collectively termed channelopathies. Characterization of many of these channels has been undertaken in a variety of both prokaryotic and eukaryotic organisms. Among these organisms is the budding yeast Saccharomyces cerevisiae. Possessing a fully annotated genome, S. cerevisiae would appear to be an ideal organism in which to study this class of proteins associated to diseases. We have compiled and reviewed a list of yeast ion channels, each possessing a human homolog implicated in a channelopathy. Although yeast has been used for the study of other human disease, it has been under utilized for channelopathy research. The utility of using yeast as a model system for studying ion channels associated to human disease is illustrated using yeast lacking the GEF1 gene product that encodes the human homolog to the chloride channel CLC-3.

Animals↗
PubMed2005

Defective lysosomal arginine transport in juvenile Batten disease.

Mutations in the CLN3 gene, which encodes a lysosomal membrane protein, are responsible for the neurodegenerative disorder juvenile Batten disease. A previous study on the yeast homolog to CLN3, designated Btn1p, revealed a potential role for CLN3 in the transport of arginine into the yeast vacuole, the equivalent organelle to the mammalian lysosome. Lysosomes isolated from lymphoblast cell lines, established from individuals with juvenile Batten disease-bearing mutations in CLN3, but not age-matched controls, demonstrate defective transport of arginine. Furthermore, we show that there is a depletion of arginine in cells derived from individuals with juvenile Batten disease. We have, therefore, characterized lysosomal arginine transport in normal lysosomes and show that it is ATP-, v-ATPase- and cationic-dependent. This and previous studies have shown that both arginine and lysine are transported by the same transport system, designated system c. However, we report that lysosomes isolated from juvenile Batten disease lymphoblasts are only defective for arginine transport. These results suggest that the CLN3 defect in juvenile Batten disease may affect how intracellular levels of arginine are regulated or distributed throughout the cell. This assertion is supported by two other experimental approaches. First, an antibody to CLN3 can block lysosomal arginine transport and second, expression of CLN3 in JNCL cells using a lentiviral vector can restore lysosomal arginine transport. CLN3 may have a role in regulating intracellular levels of arginine possibly through control of the transport of this amino acid into lysosomes.

Adenosine Triphosphate↗
PubMed2005

Novel CLN3 mutation predicted to cause complete loss of protein function does not modify the classical JNCL phenotype.

Juvenile Neuronal Ceroid Lipofuscinosis (JNCL), or Batten disease, is a childhood neurodegenerative disease that is characterized clinically by progressive visual loss, seizures, dementia, and motor incoordination. Children affected with this disease tend to develop normally for the first 5 years of life. However, once disease onset occurs, they decline rapidly and die in their late 20s to early 30s. Though this represents the typical disease course, the onset and severity of disease symptoms can vary. This variability is presumed to be the result of both differences in the causative genetic mutation in the CLN3 gene as well as environmental influences. Most cases of JNCL are caused by a 1 kb deletion in the CLN3 gene, resulting in a frameshift mutation predicted to leave the first 153 amino acids of the CLN3 protein intact, followed by the addition of 28 novel amino acids. Here we report the discovery of a novel mutation identified as a G to T transversion at nucleotide 49 (G49T) in exon 2 of CLN3, introducing a premature stop codon (E17X) near the N-terminus. This mutation represents the most 5' mutation described to date. The patient examined in this study was heterozygous for the common 1 kb deletion and E17X. She had classical disease progression, suggesting that this mutation in CLN3 mimics the more prevalent 1 kb deletion and that progression of JNCL is predominantly the result of loss of CLN3 function.

Adult↗
PubMed2005

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 -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.

Aging↗
PubMed2005

The structure and stability of the bacterioplankton community in Antarctic freshwater lakes, subject to extremely rapid environmental change.

In this study, variation in the bacterioplankton community structure of three Antarctic lakes of different nutrient status, was determined in relation to physical and chemical gradients at depth and at time intervals, across the seasonal transition from winter ice-cover to the summer ice-free period. The three lakes studied were: Moss Lake (low nutrient, with typical nutrient concentrations of 80 microg l(-1) nitrate and 10 microg l(-1) dissolved reactive phosphate), Sombre Lake (low nutrient, but becoming progressively enriched, with typical nutrient concentrations of 185 microg l(-1) nitrate and 7 microg l(-1) dissolved reactive phosphate) and Heywood Lake (enriched, with typical nutrient concentrations of 1180 microg l(-1) nitrate and 124 microg l(-1) dissolved reactive phosphate). Bacterioplankton community structure was determined using a combination of PCR amplification of 16S rRNA gene fragments and denaturing gradient gel electrophoresis (DGGE). Results indicated marked changes in this bacterioplankton community structure, which were particularly associated with the transition period. However, significant changes also occurred during the period of holomixis. Comparison of the results from lakes of different nutrient status suggest that increased levels of nutrient input, and in the timing and duration of ice cover will lead to marked changes in the structure and stability of the bacterioplankton community at existing levels of environmental change.

Antarctic Regions↗
PubMed2005

Elevation of Hook1 in a disease model of Batten disease does not affect a novel interaction between Ankyrin G and Hook1.

Hook1 is a member of a family of microtubule-binding proteins. Studies on the Drosophila homolog of Hook1 have suggested a role in the maturation and trafficking of internalized proteins to the late endosome. A weak interaction between Hook1 and the lysosomal/late endosomal protein, CLN3, was recently reported. Mutations in CLN3 result in the neurological disorder Batten disease. Here we show a novel interaction between Hook1 and Ankyrin G, an adaptor protein that binds the spectrin-actin cytoskeleton and targets proteins to the peripheral membrane. Although we demonstrate co-localization of Hook1 and Ankyrin G, Hook1 also localizes to additional regions of the cell devoid of Ankyrin G where it likely interacts with other proteins. There is no disruption of the Hook1-Ankyrin G interaction or localization in tissue derived from a Cln3-knockout mouse despite a nearly threefold increase in the expression of Hook1. However, mutation of CLN3 could lead to alterations in the functioning and positioning of organelles and membrane proteins through this Hook1-Ankyrin G interaction.

Animals↗
PubMed2005

Reelin signaling is impaired in autism.

BACKGROUND: Autism is a severe neurodevelopmental disorder with genetic and environmental etiologies. Recent genetic linkage studies implicate Reelin glycoprotein in causation of autism. To further investigate these studies, brain levels of Reelin protein and mRNA and mRNAs for VLDLR, Dab-1, and GSK3 were investigated. METHODS: Postmortem superior frontal, parietal, and cerebellar cortices of age, gender, and postmortem interval-matched autistic and control subjects were subjected to SDS-PAGE and Western blotting of Reelin protein. Quantitative reverse transcriptase polymerase chain reaction analysis of Reelin, VLDL-R, Dab-1, and GSK3 mRNA species in superior frontal and cerebellar cortices of autistic and control subjects were also performed. RESULTS: Reelin 410, 330, and 180 kDa/beta-actin values were reduced significantly in frontal and cerebellar, and nonsignificantly in parietal, areas of autistic brains versus control subjects, respectively. The mRNAs for Reln and Dab-1 were reduced significantly whereas the mRNA for Reln receptor VLDLR was elevated significantly in superior frontal and cerebellar areas of autistic brains versus control brains, respectively. CONCLUSIONS: Reductions in Reelin protein and mRNA and Dab 1 mRNA and elevations in Reln receptor VLDLR mRNA demonstrate impairments in the Reelin signaling system in autism, accounting for some of the brain structural and cognitive deficits observed in the disorder.

Actins↗