Allelic series of Huntington's disease knock-in mice reveals expression discorrelates.

Identifying molecular drivers of pathology provides potential therapeutic targets. Differentiating between drivers and coincidental molecular alterations presents a major challenge. Variation unrelated to pathology further complicates transcriptomic, proteomic and metabolomic studies which measure large numbers of individual molecules.

Involvement of the mitochondrial permeability transition pore in chronic ethanol-mediated liver injury in mice.

Chronic ethanol consumption increases sensitivity of the mitochondrial permeability transition (MPT) pore induction in liver. Ca(2+) promotes MPT pore opening, and genetic ablation of cyclophilin D (CypD) increases the Ca(2+) threshold for the MPT. We used wild-type (WT) and CypD-null (CypD(-/-)) mice fed a control or an ethanol-containing diet to investigate the role of the MPT in ethanol-mediated liver injury.

Hyperactivity and cortical disinhibition in mice with restricted expression of mutant huntingtin to parvalbumin-positive cells.

Recent evidence suggests that interneurons are involved in the pathophysiology of Huntington Disease (HD). Abnormalities in the function of interneurons expressing the calcium buffer parvalbumin (PV) have been observed in multiple mouse models of HD, although it is not clear how PV-positive interneuron dysfunction contributes to behavioral and synaptic deficits. Here, we use the cre-lox system to drive expression of mutant huntingtin (mthtt) in parvalbumin (PV)-positive neurons and find that mutant mice exhibit diffuse mthtt immunoreactivity in PV-rich areas at 10months of age and mthtt aggregates in PV-positive processes at 24months of age.

Enhanced Ca(2+)-dependent glutamate release from astrocytes of the BACHD Huntington's disease mouse model.

Huntington's disease (HD) causes preferential loss of a subset of neurons in the brain although the huntingtin protein is expressed broadly in various neural cell types, including astrocytes. Glutamate-mediated excitotoxicity is thought to cause selective neuronal injury, and brain astrocytes have a central role in regulating extracellular glutamate. To determine whether full-length mutant huntingtin expression causes a cell-autonomous phenotype and perturbs astrocyte gliotransmitter release, we studied cultured cortical astrocytes from BACHD mice.

Purkinje cell dysfunction and loss in a knock-in mouse model of Huntington disease.

Huntington Disease (HD) is an autosomal dominant neurological disorder characterized by motor, psychiatric and cognitive disturbances. Recent evidence indicates that the viability and function of cerebellar Purkinje cells (PCs) are compromised in an aggressive mouse model of HD. Here we investigate whether this is also the case in the HdhQ200 knock-in mouse model of HD.

Tissue transglutaminase overexpression does not modify the disease phenotype of the R6/2 mouse model of Huntington's disease.

Huntington's disease (HD) is a devastating autosomal-dominant neurodegenerative disorder initiated by an abnormally expanded polyglutamine in the huntingtin protein. Determining the contribution of specific factors to the pathogenesis of HD should provide rational targets for therapeutic intervention. One suggested contributor is the type 2 transglutaminase (TG2), a multifunctional calcium dependent enzyme.

Disruption of Purkinje cell function prior to huntingtin accumulation and cell loss in an animal model of Huntington disease.

Huntington Disease (HD) is a devastating neurological disorder characterized by progressive deterioration of psychiatric, motor, and cognitive function. Purkinje cells (PCs), the output neurons of the cerebellar cortex, have been found to be vulnerable in multiple CAG repeat disorders, but little is known about the involvement of PC dysfunction in HD. To investigate possible PC abnormalities, we performed quantitative real time PCR, Western blot analysis, and immunohistochemistry experiments to explore the changes in PC markers in the R6/2 mouse model of severe HD.

14-3-3theta protects against neurotoxicity in a cellular Parkinson's disease model through inhibition of the apoptotic factor Bax.

Disruption of 14-3-3 function by alpha-synuclein has been implicated in Parkinson's disease. As 14-3-3s are important regulators of cell death pathways, disruption of 14-3-3s could result in the release of pro-apoptotic factors, such as Bax. We have previously shown that overexpression of 14-3-3θ reduces cell loss in response to rotenone and MPP(+) in dopaminergic cell culture and reduces cell loss in transgenic C.

Immunophilin deficiency augments Ca2+-dependent glutamate release from mouse cortical astrocytes.

Immunophilins are receptors for immunosuppressive drugs such as the macrolides cyclosporin A (CsA) and FK506; correspondingly these immunophilins are referred to as cyclophilins and FK506-binding proteins (FKBPs). In particular, CsA targets cyclophilin D (CypD), which can modulate mitochondrial Ca(2+) dynamics. Since mitochondria have been implicated in the regulation of astrocytic cytosolic Ca(2+) (Ca(cyt)(2+)) dynamics and consequential Ca(2+)-dependent exocytotic release of glutamate, we investigated the role of CypD in this process.

Human cytomegalovirus UL97 kinase prevents the deposition of mutant protein aggregates in cellular models of Huntington's disease and ataxia.

The presence of aggregates of abnormally expanded polyglutamine (polyQ)-containing proteins are a pathological hallmark of a number of neurodegenerative diseases including Huntington's disease (HD) and spinocerebellar ataxia-3 (SCA3). Previous studies in cellular, Drosophila, and mouse models of HD and SCA have shown that neurodegeneration can be prevented by manipulations that inhibit polyQ aggregation. We have shown that the UL97 kinase of the human cytomegalovirus (HCMV) prevents aggregation of the pp71 and pp65 viral tegument proteins.

Chronic ethanol consumption enhances sensitivity to Ca(2+)-mediated opening of the mitochondrial permeability transition pore and increases cyclophilin D in liver.

Chronic ethanol consumption increases mitochondrial oxidative stress and sensitivity to form the mitochondrial permeability transition pore (MPTP). The mechanism responsible for increased MPTP sensitivity in ethanol-exposed mitochondria and its relation to mitochondrial Ca(2+) handling is unknown. Herein, we investigated whether increased sensitivity to MPTP induction in liver mitochondria from ethanol-fed rats compared with controls is related to an ethanol-dependent change in mitochondrial Ca(2+) accumulation.

Early autophagic response in a novel knock-in model of Huntington disease.

The aggregation of mutant polyglutamine (polyQ) proteins has sparked interest in the role of protein quality-control pathways in Huntington's disease (HD) and related polyQ disorders. Employing a novel knock-in HD mouse model, we provide in vivo evidence of early, sustained alterations of autophagy in response to mutant huntingtin (mhtt). The HdhQ200 knock-in model, derived from the selective breeding of HdhQ150 knock-in mice, manifests an accelerated and more robust phenotype than the parent line.

Mitochondrial calcium uptake capacity as a therapeutic target in the R6/2 mouse model of Huntington's disease.

Huntington's disease (HD) is an incurable autosomal-dominant neurodegenerative disorder initiated by an abnormally expanded polyglutamine domain in the huntingtin protein. It is proposed that abnormal mitochondrial Ca2+ capacity results in an increased susceptibility to mitochondrial permeability transition (MPT) induction that may contribute significantly to HD pathogenesis. The in vivo contribution of these hypothesized defects remains to be elucidated.

Ubiquitin-proteasome system alterations in a striatal cell model of Huntington's disease.

Huntington's disease (HD) is a progressive, autosomal dominant neurodegenerative disease caused by an abnormally expanded CAG repeat in the HD gene. Ubiquitylated aggregates containing mutant huntingtin protein in neurons are hallmarks of HD. Misfolded mutant huntingtin monomers, oligomers, or aggregates may be a result of, and cause, ubiquitin- proteasome dysfunction.

HD CAG repeat implicates a dominant property of huntingtin in mitochondrial energy metabolism.

The 'expanded' HD CAG repeat that causes Huntington's disease (HD) encodes a polyglutamine tract in huntingtin, which first targets the death of medium-sized spiny striatal neurons. Mitochondrial energetics, related to N-methyl-d-aspartate (NMDA) Ca2+-signaling, has long been implicated in this neuronal specificity, implying an integral role for huntingtin in mitochondrial energy metabolism. As a genetic test of this hypothesis, we have looked for a relationship between the length of the HD CAG repeat, expressed in endogenous huntingtin, and mitochondrial ATP production.

Verification of somatic CAG repeat expansion by pre-PCR fractionation.

The inheritance of a long CAG repeat causes several late onset neurological disorders including Huntington's disease (HD). Longer CAG repeats correlate with earlier onset of HD suggesting an increased toxicity for the products of long repeat alleles. PCR based data has been used to show that HD CAG repeat expansion beyond the inherited length occurs in affected tissues indicating a possible role for somatic instability in the disease process.

Striatal cells from mutant huntingtin knock-in mice are selectively vulnerable to mitochondrial complex II inhibitor-induced cell death through a non-apoptotic pathway.

Extensive striatal neuronal loss occurs in Huntington's disease (HD), which is caused by an expanded polyglutamine tract in huntingtin (htt). Evidence suggests that mutant htt directly or indirectly compromises mitochondrial function, contributing to the neuronal loss. To determine the role of compromised mitochondrial function in the neuronal cell death in HD, immortalized striatal cells established from Hdh(Q7) (wild-type) and Hdh(Q111) (mutant) mouse knock-in embryos were treated with 3-nitropropionic acid (3-NP), a mitochondrial complex II toxin.

Transient osmotic stress facilitates mutant huntingtin aggregation.

Human neuroblastoma SH-SY5Y cell lines stably expressing mutant truncated huntingtin with 82 (mutant) glutamine repeats (N63-82Q) were briefly exposed to hyperosmotic conditions which decrease cell volume and therefore transiently increased the concentration of N63-82Q, as well as activating specific stress-induced pathways. Transient hyperosmotic treatment significantly increased the number of cells with aggregates. When the N63-82Q cells were subsequently returned to iso-osmotic medium after the treatment, the number of cells with aggregates remained constant up to 12 h.

Cystamine inhibits caspase activity. Implications for the treatment of polyglutamine disorders.

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by an abnormally expended polyglutamine domain. There is no effective treatment for HD; however, inhibition of caspase activity or prevention of mitochondria dysfunction delays disease progression in HD mouse models. Similarly administration of cystamine, which can inhibit transglutaminase, prolonged survival of HD mice, suggesting that inhibition of transglutaminase might provide a new treatment strategy.

Mutant huntingtin aggregates do not sensitize cells to apoptotic stressors.

It has been postulated that neuronal inclusions composed of mutant huntingtin may play a causative role in the pathogenesis of Huntington's disease. To study the putative role of aggregates in modulating apoptotic vulnerability, SH-SY5Y cell lines stably expressing truncated huntingtin with 18 (wild-type) (N63-18Q) or 82 (mutant) (N63-82Q) glutamine repeats were established. Aggregates were observed in approximately 13% of the N63-82Q cells; no aggregates were observed in the N63-18Q cells.

Does tissue transglutaminase play a role in Huntington's disease?

Tissue transglutaminase (tTG) likely plays a role in numerous processes in the nervous system. tTG posttranslationally modifies proteins by transamidation of specific polypeptide bound glutamines (Glns). This reaction results in the incorporation of polyamines into substrate proteins or the formation of protein crosslinks, modifications that likely have significant effects on neural function.

Tissue transglutaminase selectively modifies proteins associated with truncated mutant huntingtin in intact cells.

The cause of Huntington's disease (HD) is a pathological expansion of the polyglutamine domain within the N-terminal region of huntingtin. Neuronal intranuclear inclusions and cytoplasmic aggregates composed of the mutant huntingtin within certain neuronal populations are a characteristic hallmark of HD. However, how the expanded polyglutamine repeats of mutant huntingtin cause HD is not known.