Transgenic Huntington's Mice Research Articles

DNA microarray analysis of striatal gene expression in symptomatic transgenic Huntington's mice (R6/2) reveals neuroinflammation and insulin associations

Huntington's disease (HD) is an inherited, progressive neurodegenerative disorder caused by CAG repeat expansion in the gene that codes for the protein huntingtin. The underlying neuropathological events leading to the selectivity of striatal neuronal loss are unknown. However, the huntingtin mutation interferes at several levels of normal cell function. The complexity of this disease makes microarray analysis an appealing technique to begin the identification of common pathways that may contribute to the pathology. In this study, striatal tissue was extracted for gene expression profiling from wild-type and symptomatic transgenic Huntington mice (R6/2) expressing part of the human Huntington's disease gene. We interrogated a 15 K high-density mouse EST array not previously used for HD and identified 170 significantly differentially expressed ESTs in symptomatic R6/2 mice. Of the 80 genes with known function, 9 genes had previously been identified as altered in HD. 71 known genes were associated with HD for the first time. The data obtained from this study confirm and extend previous observations using DNA microarray techniques on genetic models for HD, revealing novel changes in expression in a number of genes not previously associated with HD. Further bioinformatic analysis, using software to construct biological association maps, focused attention on proteins such as insulin and TH1-mediated cytokines, suggesting that they may be important regulators of affected genes. These results may provide insight into the regulation and interaction of genes that contribute to adaptive and pathological processes involved in HD.

Clioquinol down-regulates mutant huntingtin expressionin vitroand mitigates pathology in a Huntington's disease mouse model

In investigating the role of metal ions in the pathogenesis of Huntington's disease, we examined the effects of clioquinol, a metal-binding compound currently in clinical trials for Alzheimer's disease treatment, on mutant huntingtin-expressing cells. We found that PC12 cells expressing polyglutamine-expanded huntingtin exon 1 accumulated less mutant protein and showed decreased cell death when treated with clioquinol. This effect was polyglutamine-length-specific and did not alter mRNA levels or protein degradation rates. Clioquinol treatment of transgenic Huntington's mice (R6/2) improved behavioral and pathologic phenotypes, including decreased huntingtin aggregate accumulation, decreased striatal atrophy, improved rotarod performance, reduction of weight loss, normalization of blood glucose and insulin levels, and extension of lifespan. Our results suggest that clioquinol is a candidate therapy for Huntington's disease and other polyglutamine-expansion diseases.

51. Adenoviral BDNF/Noggin-Induced Neurogenesis from Endogenous Neural Stem Cells Delays Motor Impairment and Extends Survival in a Transgenic Model of Huntington's Disease

Ependymal overexpression of BDNF stimulates neuronal addition to the adult striatum, from subependymal progenitors. Noggin, by suppressing subependymal gliogenesis, potentiates this process. We asked if BDNF/Noggin overexpression might be used to recruit new striatal neurons in R6/2 transgenic Huntington's mice. In series 1, 18 R6/2 mice and matched wild-type (WT) controls were given bilateral intraventricular injections of either adenoviral (Ad) BDNF/Noggin, AdBDNF, AdNull or saline at 6 weeks of age. The mice were given daily injections of BrdU for 4 weeks to tag new mitotic cells, sacrificed at 10 weeks, and their brains cut at 15 |[mu]|m. Sections were stained for BrdU and either bIII-tubulin, DARPP-32, GAD67, enkephalin, or substance P. AdBDNF/Noggin-treatment resulted in the addition of approximately 300 BrdU+/bIII-tubulin+ neurons/mm3 in both R6/2 and WT striata. These developed largely as DARPP32+ medium spiny neurons, with enkephalin+ and substance P+ GABAergic subpopulations generated in roughly equal proportions; each type extended fibers to the globus pallidus, as revealed by Fluorogold backfills.

Cerebral PET imaging and histological evidence of transglutaminase inhibitor cystamine induced neuroprotection in transgenic R6/2 mouse model of Huntington's disease

To investigate efficacy of cystamine induced neuroprotection, we conducted PET imaging studies of cerebral glucose metabolism with [18F]FDG (2-deoxy-2-[18F]fluoro-d-glucose) and striatal dopamine D2 receptor function with [11C]raclopride in R6/2 transgenic Huntington mice. In the control mice, exponentially decreasing glucose utilization was observed in the striatum Nstr [SUV]=(41.75±11.80)58,str*exp(−(0.041±0.007)*t [days]); cortex Ncort [SUV]=24.14±3.66)58,cort*exp(−(0.043±0.007)*t [days]); and cerebellum Ncer [SUV]=(34.97±10.58)58,cer*exp(−(0.037±0.008)*t [days]) as a function of age starting at 58 days. Given that the underlying degeneration rate in the cystamine treated mice is similar to that observed in control animals, the protection coefficient (β) calculated from the equation Nt=N58*exp(−(1−β)*k*t) was 0.133±0.035 for the striatum; 0.122±0.028 for the cortex and 0.224±00.042 for the cerebellum with a dose of 100 mg/kg. The 50 mg/kg cystamine dose provided significant protection only for the striatum and only minor protection was obtained using lower doses. Striatal binding potential of [11C]raclopride was 1.059±0.030 in the control mice, and enhanced in the cystamine treated animals in a dose dependent manner up to 1.245±0.063 using the 100 mg/kg dose.Histological analysis confirmed cystamine induced neuroprotection of striatal and cortical neurons and Nissl staining revealed that formation of cellular inclusions was reversed in a dose dependent manner. Cerebral imaging and histological evidence support the use of cystamine as a neuroprotective agent for Huntington's disease (HD) pathology.

High-resolution x-ray absorption spectroscopy studies of metal compounds in neurodegenerative brain tissue

Fluorescence mapping and microfocus X-ray absorption spectroscopy are used to detect, locate and identify iron biominerals and other inorganic metal accumulations in neurodegenerative brain tissue at sub-cellular resolution (<5 microns). Recent progress in developing the technique is reviewed. Synchrotron X-rays are used to map tissue sections for metals of interest, and XANES and XAFS are used to characterise anomalous concentrations of the metals in-situ so that they can be correlated with tissue structures and disease pathology. Iron anomalies associated with biogenic magnetite, ferritin and haemoglobin are located and identified in an avian tissue model with a pixel resolution ∼5 microns. Subsequent studies include brain tissue sections from transgenic Huntington's mice, and the first high-resolution mapping and identification of iron biominerals in human Alzheimer's and control autopsy brain tissue. Technical developments include use of microfocus diffraction to obtain structural information about biominerals in-situ, and depositing sample location grids by lithography for the location of anomalies by conventional microscopy. The combined techniques provide a breakthrough in the study of both intra- and extra-cellular iron compounds and related metals in tissue. The information to be gained from this approach has implications for future diagnosis and treatment of neurodegeneration, and for our understanding of the mechanisms involved.

Altered striatal amino acid neurotransmitter release monitored using microdialysis in R6/1 Huntington transgenic mice.

Huntington's disease is an autosomal dominant disease which presents with striatal and cortical degeneration causing involuntary movements, dementia and emotional changes. We employed 16-week-old transgenic Huntington mice (R6/1 line developed by Bates and coworkers) that express exon 1 of the mutant human Huntington gene with 115 CAG triplet repeats. At this age, R6/1 mice do not exhibit an overt neurological phenotype nor any striatal neuronal loss. Using microdialysis, we monitored basal and intrastriatal N-methyl D-aspartate (NMDA, 100 microM, 15 min)- and KCl (100 mM, 15 min)-induced increases in local aspartate, glutamate and GABA release in halothane-anaesthetized transgenic mice and wild-type controls. Basal striatal dialysate glutamate levels were reduced by 42% in R6/1 mice whilst aspartate and GABA levels did not differ from those observed in control mice. Intrastriatal NMDA was associated with significantly greater aspartate (at 15 min) and GABA (at 30 min) levels in the R6/1 mice compared to controls, whilst glutamate release rapidly increased to the same extent in both groups. Intrastriatal KCl was associated with enhanced increases (30 min) in local aspartate and glutamate release in the R6/1 mice above those observed in controls whilst the rapid increase (15 min) in GABA release was similar in both groups. The results provide compelling evidence for specific alterations in both basal, as well as NMDA- and KCl-induced, release of striatal amino acid neurotransmitters in this transgenic model of Huntington's disease, even in the absence of manifest neurodegeneration.