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Dyna I Shirasaki,
Erin R Greiner,
Ismael Al-Ramahi,
Michelle Gray,
Pinmanee Boontheung,
Daniel H Geschwind,
Juan Botas,
Giovanni Coppola,
Steve Horvath,
Joseph A Loo, X William Yang
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ABSTRACT: We used affinity-purification mass spectrometry to identify 747 candidate proteins that are complexed with Huntingtin (Htt) in distinct brain regions and ages in Huntington's disease (HD) and wild-type mouse brains. To gain a systems-level view of the Htt interactome, we applied Weighted Correlation Network Analysis to the entire proteomic data set to unveil a verifiable rank of Htt-correlated proteins and a network of Htt-interacting protein modules, with each module highlighting distinct aspects of Htt biology. Importantly, the Htt-containing module is highly enriched with proteins involved in 14-3-3 signaling, microtubule-based transport, and proteostasis. Top-ranked proteins in this module were validated as Htt interactors and genetic modifiers in an HD Drosophila model. Our study provides a compendium of spatiotemporal Htt-interacting proteins in the mammalian brain and presents an approach for analyzing proteomic interactome data sets to build in vivo protein networks in complex tissues, such as the brain.
Neuron 07/2012; 75(1):41-57. · 14.74 Impact Factor
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ABSTRACT: Lowering mutant Huntingtin is a consensus therapeutic strategy for Huntington's disease. In this issue of Neuron, Kordasiewicz et al. (2012) show the benefit of transient antisense oligonucleotide (ASO) therapy to degrade Huntingtin mRNA and elicit sustained therapeutic benefit in HD mice.
Neuron 06/2012; 74(6):964-6. · 14.74 Impact Factor
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Jason Miller,
Montserrat Arrasate,
Elizabeth Brooks,
Clare Peters Libeu,
Justin Legleiter,
Danny Hatters,
Jessica Curtis,
Kenneth Cheung,
Preethi Krishnan,
Siddhartha Mitra, [......],
Michelle Gray,
Vanitha Thulasiramin,
Frédéric Saudou,
Mark Segal, X William Yang,
Eliezer Masliah,
Leslie M Thompson,
Paul J Muchowski,
Karl H Weisgraber,
Steven Finkbeiner
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ABSTRACT: Polyglutamine (polyQ) stretches exceeding a threshold length confer a toxic function to proteins that contain them and cause at least nine neurological disorders. The basis for this toxicity threshold is unclear. Although polyQ expansions render proteins prone to aggregate into inclusion bodies, this may be a neuronal coping response to more toxic forms of polyQ. The exact structure of these more toxic forms is unknown. Here we show that the monoclonal antibody 3B5H10 recognizes a species of polyQ protein in situ that strongly predicts neuronal death. The epitope selectively appears among some of the many low-molecular-weight conformational states assumed by expanded polyQ and disappears in higher-molecular-weight aggregated forms, such as inclusion bodies. These results suggest that protein monomers and possibly small oligomers containing expanded polyQ stretches can adopt a conformation that is recognized by 3B5H10 and is toxic or closely related to a toxic species.
Nature Chemical Biology 12/2011; 7(12):925-34. · 14.69 Impact Factor
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Jifang Tao,
Hao Wu,
Quan Lin,
Weizheng Wei,
Xiao-Hong Lu,
Jeffrey P Cantle,
Yan Ao,
Richard W Olsen, X William Yang,
Istvan Mody,
Michael V Sofroniew,
Yi E Sun
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ABSTRACT: The endoribonuclease, Dicer, is indispensable for generating the majority of mature microRNAs (miRNAs), which are posttranscriptional regulators of gene expression involved in a wide range of developmental and pathological processes in the mammalian CNS. Although functions of Dicer-dependent miRNA pathways in neurons and oligodendrocytes have been extensively investigated, little is known about the role of Dicer in astrocytes. Here, we report the effect of Cre-loxP-mediated conditional deletion of Dicer selectively from postnatal astroglia on brain development. Dicer-deficient mice exhibited normal motor development and neurological morphology before postnatal week 5. Thereafter, mutant mice invariably developed a rapidly fulminant neurological decline characterized by ataxia, severe progressive cerebellar degeneration, seizures, uncontrollable movements, and premature death by postnatal week 9-10. Integrated transcription profiling, histological, and functional analyses of cerebella showed that deletion of Dicer in cerebellar astrocytes altered the transcriptome of astrocytes to be more similar to an immature or reactive-like state before the onset of neurological symptoms or morphological changes. As a result, critical and mature astrocytic functions including glutamate uptake and antioxidant pathways were substantially impaired, leading to massive apoptosis of cerebellar granule cells and degeneration of Purkinje cells. Collectively, our study demonstrates the critical involvement of Dicer in normal astrocyte maturation and maintenance. Our findings also reveal non-cell-autonomous roles of astrocytic Dicer-dependent pathways in regulating proper neuronal functions and implicate that loss of or dysregulation of astrocytic Dicer-dependent pathways may be involved in neurodegeneration and other neurological disorders.
Journal of Neuroscience 06/2011; 31(22):8306-19. · 7.11 Impact Factor
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Brian Wilburn,
Dobrila D Rudnicki,
Jing Zhao,
Tara Murphy Weitz,
Yin Cheng,
Xiaofeng Gu,
Erin Greiner,
Chang Sin Park,
Nan Wang,
Bryce L Sopher,
Albert R La Spada,
Alex Osmand,
Russell L Margolis,
Yi E Sun, X William Yang
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ABSTRACT: Huntington's disease-like-2 (HDL2) is a phenocopy of Huntington's disease caused by CTG/CAG repeat expansion at the Junctophilin-3 (JPH3) locus. The mechanisms underlying HDL2 pathogenesis remain unclear. Here we developed a BAC transgenic mouse model of HDL2 (BAC-HDL2) that exhibits progressive motor deficits, selective neurodegenerative pathology, and ubiquitin-positive nuclear inclusions (NIs). Molecular analyses reveal a promoter at the transgene locus driving the expression of a CAG repeat transcript (HDL2-CAG) from the strand antisense to JPH3, which encodes an expanded polyglutamine (polyQ) protein. Importantly, BAC-HDL2 mice, but not control BAC mice, accumulate polyQ-containing NIs in a pattern strikingly similar to those in the patients. Furthermore, BAC mice with genetic silencing of the expanded CUG transcript still express HDL2-CAG transcript and manifest polyQ pathogenesis. Finally, studies of HDL2 mice and patients revealed CBP sequestration into NIs and evidence for interference of CBP-mediated transcriptional activation. These results suggest overlapping polyQ-mediated pathogenic mechanisms in HD and HDL2.
Neuron 05/2011; 70(3):427-40. · 14.74 Impact Factor
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ABSTRACT: This article reviews recent literature describing novel mouse genetic models of obsessive-compulsive disorder-like behaviors and neurobiological insights gained from analyses of such models.
Obsessive-compulsive disorder is a common neuropsychiatric disorder characterized by recurrent intrusive thoughts (obsessions) and ritualistic (compulsive) behaviors. Although the cause of this disorder remains unclear, recent studies of novel mouse genetic models with excessive grooming behaviors have begun to shed light on the molecular and cellular mechanisms underlying the pathogenesis of 'obsessive-compulsive disorder-like' behaviors. Genetic deletion of three genes in mice, Hoxb8, Sapap3, and Slitrk5, leads to pathological behaviors including adult-onset excessive grooming with mild-to-severe hair loss and self-injury. In two of the models, the Sapap3-deficient and the Slitrk5-deficient mice, the abnormal grooming behaviors are associated with enhanced anxiety and these pathological behaviors can be curtailed with subchronic administration of a selective serotonin reuptake inhibitor, suggesting the predictive validity of such models. Molecular, pathophysiological, and genetic analyses of these models reveal several insights on the etiological basis of abnormal behaviors in these mice, including abnormal cortico-striatal synapse formation and function in Sapap3 mice, impaired development and function of bone marrow-derived microglia in Hoxb8 mice, and abnormal striatal neuronal differentiation and neurotransmission in Slitrk5 mice.
Novel animal models provide powerful tools to investigate the molecular, cellular, and circuitry mechanisms of obsessive-compulsive disorder-like behaviors. Detailed analyses of these models may provide candidate molecules and mechanisms for the investigation of cause and therapy of obsessive-compulsive disorder.
Current opinion in neurology 04/2011; 24(2):114-8. · 5.43 Impact Factor
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ABSTRACT: There is considerable evidence that alterations in striatal medium-sized spiny neurons (MSSNs) giving rise to the direct (D1 receptor-expressing) and indirect (D2 receptor-expressing) pathways differentially contribute to the phenotype of Huntington's disease (HD). To determine how each subpopulation of MSSN is functionally affected, we examined spontaneous excitatory postsynaptic currents (sEPSCs) and dopamine (DA) modulation in two HD mouse models, the YAC128 and the BACHD (a bacterial-artificial chromosome). These mice also expressed enhanced green fluorescent protein (EGFP) under the control of the promoter for either DA D1 or D2 receptors to identify neurons. In early symptomatic YAC128 and BACHD mice, glutamate transmission was increased in both D1 and D2 MSSNs, but in different ways. D1 cells displayed increased sEPSC frequencies and decreased paired-pulse ratios (PPRs) while D2 cells displayed larger evoked glutamate currents but no change in sEPSC frequencies or PPRs. D1 receptor modulation of sEPSCs was absent in D1-YAC128 cells at the early symptomatic stage but was restored by treating the slices with tetrabenazine. In contrast, in fully symptomatic YAC128 mice, glutamate transmission was decreased specifically in D1 cells, and D1 receptor modulation was normal in D1-YAC128 cells. Behaviorally, early symptomatic mice showed increased stereotypies that were decreased by tetrabenazine treatment. Together, these studies support differential imbalances in glutamate and DA transmission in direct and indirect pathway MSSNs. Stereotypic behavior at an early stage could be explained by increased glutamate activity and DA tone in direct pathway neurons, whereas hypokinesia at later stages could result from reduced input onto these neurons.
Journal of Neuroscience 01/2011; 31(4):1170-82. · 7.11 Impact Factor
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Nature Chemical Biology 01/2011; 7(7):412-4. · 14.69 Impact Factor
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Rona K Graham,
Yu Deng,
Jeffery Carroll,
Kuljeet Vaid,
Catherine Cowan,
Mahmoud A Pouladi,
Martina Metzler,
Nagat Bissada,
Lili Wang,
Richard L M Faull,
Michelle Gray, X William Yang,
Lynn A Raymond,
Michael R Hayden
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ABSTRACT: Caspase cleavage of huntingtin (htt) and nuclear htt accumulation represent early neuropathological changes in brains of patients with Huntington's disease (HD). However, the relationship between caspase cleavage of htt and caspase activation patterns in the pathogenesis of HD remains poorly understood. The lack of a phenotype in YAC mice expressing caspase-6-resistant (C6R) mutant htt (mhtt) highlights proteolysis of htt at the 586 aa caspase-6 (casp6) site as a key mechanism in the pathology of HD. The goal of this study was to investigate how proteolysis of htt at residue 586 plays a role in the pathogenesis of HD and determine whether inhibiting casp6 cleavage of mhtt alters cell-death pathways in vivo. Here we demonstrate that activation of casp6, and not caspase-3, is observed before onset of motor abnormalities in human and murine HD brain. Active casp6 levels correlate directly with CAG size and inversely with age of onset. In contrast, in vivo expression of C6R mhtt attenuates caspase activation. Increased casp6 activity and apoptotic cell death is evident in primary striatal neurons expressing caspase-cleavable, but not C6R, mhtt after NMDA application. Pretreatment with a casp6 inhibitor rescues the apoptotic cell death observed in this paradigm. These data demonstrate that activation of casp6 is an early marker of disease in HD. Furthermore, these data provide a clear link between excitotoxic pathways and proteolysis and suggest that C6R mhtt protects against neurodegeneration by influencing the activation of neuronal cell-death and excitotoxic pathways operative in HD.
Journal of Neuroscience 11/2010; 30(45):15019-29. · 7.11 Impact Factor
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Mahmoud A Pouladi,
Yuanyun Xie,
Niels Henning Skotte,
Dagmar E Ehrnhoefer,
Rona K Graham,
Jeong Eun Kim,
Nagat Bissada, X William Yang,
Paolo Paganetti,
Robert M Friedlander,
Blair R Leavitt,
Michael R Hayden
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ABSTRACT: Levels of full-length huntingtin (FL htt) influence organ and body weight, independent of polyglutamine length. The growth hormone-insulin like growth factor-1 (GH-IGF-1) axis is well established as a regulator of organ growth and body weight. In this study, we investigate the involvement of the IGF-1 pathway in mediating the effect of htt on body weight. IGF-1 expression was examined in transgenic mouse lines expressing different levels of FL wild-type (WT) htt (YAC18 mice), FL mutant htt (YAC128 and BACHD mice) and truncated mutant htt (shortstop mice). We demonstrate that htt influences body weight by modulating the IGF-1 pathway. Plasma IGF-1 levels correlate with body weight and htt levels in the transgenic YAC mice expressing human htt. The effect of htt on IGF-1 expression is independent of CAG size. No effect on body weight is observed in transgenic YAC mice expressing a truncated N-terminal htt fragment (shortstop), indicating that FL htt is required for the modulation of IGF-1 expression. Treatment with 17beta-estradiol (17beta-ED) lowers the levels of circulating IGF-1 in mammals. Treatment of YAC128 with 17beta-ED, but not placebo, reduces plasma IGF-1 levels and decreases the body weight of YAC128 animals to WT levels. Furthermore, given the ubiquitous expression of IGF-1 within the central nervous system, we also examined the impact of FL htt levels on IGF-1 expression in different regions of the brain, including the striatum, cerebellum of YAC18, YAC128 and littermate WT mice. We demonstrate that the levels of FL htt influence IGF-1 expression in striatal tissues. Our data identify a novel function for FL htt in influencing IGF-1 expression.
Human Molecular Genetics 04/2010; 19(8):1528-38. · 7.64 Impact Factor
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ABSTRACT: Striatal medium-sized spiny neurons (MSSNs) receive glutamatergic inputs modulated presynaptically and postsynaptically by dopamine. Mice expressing the gene for enhanced green fluorescent protein as a reporter gene to identify MSSNs containing D1 or D2 receptor subtypes were used to examine dopamine modulation of spontaneous excitatory postsynaptic currents (sEPSCs) in slices and postsynaptic N-methyl-d-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) currents in acutely isolated cells. The results demonstrated dopamine receptor-specific modulation of sEPSCs. Dopamine and D1 agonists increased sEPSC frequency in D1 receptor-expressing MSSNs (D1 cells), whereas dopamine and D2 agonists decreased sEPSC frequency in D2 receptor-expressing MSSNs (D2 cells). These effects were fully (D1 cells) or partially (D2 cells) mediated through retrograde signaling via endocannabinoids. A cannabinoid 1 receptor (CB1R) agonist and a blocker of anandamide transporter prevented the D1 receptor-mediated increase in sEPSC frequency in D1 cells, whereas a CB1R antagonist partially blocked the decrease in sEPSC frequency in D2 cells. At the postsynaptic level, low concentrations of a D1 receptor agonist consistently increased NMDA and AMPA currents in acutely isolated D1 cells, whereas a D2 receptor agonist decreased these currents in acutely isolated D2 cells. These results show that both glutamate release and postsynaptic excitatory currents are regulated in opposite directions by activation of D1 or D2 receptors. The direction of this regulation is also specific to D1 and D2 cells. We suggest that activation of postsynaptic dopamine receptors controls endocannabinoid mobilization, acting on presynaptic CB1Rs, thus modulating glutamate release differently in glutamate terminals projecting to D1 and D2 cells.
European Journal of Neuroscience 01/2010; 31(1):14-28. · 3.63 Impact Factor
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ABSTRACT: The N-terminal 17 amino acids of huntingtin (NT17) can be phosphorylated on serines 13 and 16; however, the significance of these modifications in Huntington's disease pathogenesis remains unknown. In this study, we developed BAC transgenic mice expressing full-length mutant huntingtin (fl-mhtt) with serines 13 and 16 mutated to either aspartate (phosphomimetic or SD) or alanine (phosphoresistant or SA). Both mutant proteins preserve the essential function of huntingtin in rescuing knockout mouse phenotypes. However, fl-mhtt-induced disease pathogenesis, including motor and psychiatric-like behavioral deficits, mhtt aggregation, and selective neurodegeneration are abolished in SD but preserved in SA mice. Moreover, modification of these serines in expanded repeat huntingtin peptides modulates aggregation and amyloid fibril formation in vitro. Together, our findings demonstrate that serines 13 and 16 are critical determinants of fl-mhtt-induced disease pathogenesis in vivo, supporting the targeting of huntingtin NT17 domain and its modifications in HD therapy.
Neuron 12/2009; 64(6):828-40. · 14.74 Impact Factor
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ABSTRACT: DNA methylation is a major epigenetic factor regulating genome reprogramming, cell differentiation and developmental gene expression. To understand the role of DNA methylation in central nervous system (CNS) neurons, we generated conditional Dnmt1 mutant mice that possess approximately 90% hypomethylated cortical and hippocampal cells in the dorsal forebrain from E13.5 on. The mutant mice were viable with a normal lifespan, but displayed severe neuronal cell death between E14.5 and three weeks postnatally. Accompanied with the striking cortical and hippocampal degeneration, adult mutant mice exhibited neurobehavioral defects in learning and memory in adulthood. Unexpectedly, a fraction of Dnmt1(-/-) cortical neurons survived throughout postnatal development, so that the residual cortex in mutant mice contained 20-30% of hypomethylated neurons across the lifespan. Hypomethylated excitatory neurons exhibited multiple defects in postnatal maturation including abnormal dendritic arborization and impaired neuronal excitability. The mutant phenotypes are coupled with deregulation of those genes involved in neuronal layer-specification, cell death and the function of ion channels. Our results suggest that DNA methylation, through its role in modulating neuronal gene expression, plays multiple roles in regulating cell survival and neuronal maturation in the CNS.
Human Molecular Genetics 06/2009; 18(15):2875-88. · 7.64 Impact Factor
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Xiao-Hong Lu,
Sheila M Fleming,
Bernhard Meurers,
Larry C Ackerson,
Farzad Mortazavi,
Victor Lo,
Daniela Hernandez,
David Sulzer,
George R Jackson,
Nigel T Maidment,
Marie-Francoise Chesselet, X William Yang
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ABSTRACT: Recessive mutations in parkin are the most common cause of familial early-onset Parkinson's disease (PD). Recent studies suggest that certain parkin mutants may exert dominant toxic effects to cultured cells and such dominant toxicity can lead to progressive dopaminergic (DA) neuron degeneration in Drosophila. To explore whether mutant parkin could exert similar pathogenic effects to mammalian DA neurons in vivo, we developed a BAC (bacterial artificial chromosome) transgenic mouse model expressing a C-terminal truncated human mutant parkin (Parkin-Q311X) in DA neurons driven by a dopamine transporter promoter. Parkin-Q311X mice exhibit multiple late-onset and progressive hypokinetic motor deficits. Stereological analyses reveal that the mutant mice develop age-dependent DA neuron degeneration in substantia nigra accompanied by a significant loss of DA neuron terminals in the striatum. Neurochemical analyses reveal a significant reduction of the striatal dopamine level in mutant mice, which is significantly correlated with their hypokinetic motor deficits. Finally, mutant Parkin-Q311X mice, but not wild-type controls, exhibit age-dependent accumulation of proteinase K-resistant endogenous alpha-synuclein in substantia nigra and colocalized with 3-nitrotyrosine, a marker for oxidative protein damage. Hence, our study provides the first mammalian genetic evidence that dominant toxicity of a parkin mutant is sufficient to elicit age-dependent hypokinetic motor deficits and DA neuron loss in vivo, and uncovers a causal relationship between dominant parkin toxicity and progressive alpha-synuclein accumulation in DA neurons. Our study underscores the need to further explore the putative link between parkin dominant toxicity and PD.
Journal of Neuroscience 03/2009; 29(7):1962-76. · 7.11 Impact Factor
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ABSTRACT: The mammalian striatum plays a critical function in motor control, motor and reward learning, and cognition. Dysfunction and degeneration of the striatal neurons are implicated in major neurological and psychiatric disorders. The vast majority of striatal neurons are medium spiny neurons (MSNs). MSNs can be further subdivided into distinct subtypes based on their physical localization in the striatal patch vs. matrix compartments and based on their axonal projections and marker gene expression (i.e., striatonigral MSNs vs. striatopallidal MSNs). Despite our extensive knowledge on the striatal cytoarchitecture and circuitry, little is known about the molecular mechanisms controlling the development of the MSN subtypes in the striatum. Early B-cell factor 1 (Ebf1) is a critical transcription factor implicated in striatal MSN development. One study shows that Ebf1 is critical for the differentiation of MSNs in the matrix, and our separate study demonstrates that Ebf1 is selectively expressed in the striatonigral MSNs and is essential for their postnatal differentiation. In the present study, we further validate the striatonigral MSN deficits in Ebf1(-/-) mice using multiple striatonigral MSN reporter mice. Moreover, we demonstrate that the striatonigral MSN deficits in these mice are restricted to those in the matrix, with relative sparing of those in the patch. Finally, we demonstrate that Ebf1 deficiency also results in reduced expression of another striatonigral-specific transcription factor, zinc finger binding protein 521 (Zfp521), which is a known Ebf1 functional partner. Overall, our study reveals that Ebf1 may play an essential role in controlling the differentiation of the striatonigral MSNs in the matrix compartment.
Journal of Neuroscience Research 09/2008; 86(10):2134-46. · 2.74 Impact Factor
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Michelle Gray,
Dyna I Shirasaki,
Carlos Cepeda,
Véronique M André,
Brian Wilburn,
Xiao-Hong Lu,
Jifang Tao,
Irene Yamazaki,
Shi-Hua Li,
Yi E Sun,
Xiao-Jiang Li,
Michael S Levine, X William Yang
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ABSTRACT: To elucidate the pathogenic mechanisms in Huntington's disease (HD) elicited by expression of full-length human mutant huntingtin (fl-mhtt), a bacterial artificial chromosome (BAC)-mediated transgenic mouse model (BACHD) was developed expressing fl-mhtt with 97 glutamine repeats under the control of endogenous htt regulatory machinery on the BAC. BACHD mice exhibit progressive motor deficits, neuronal synaptic dysfunction, and late-onset selective neuropathology, which includes significant cortical and striatal atrophy and striatal dark neuron degeneration. Power analyses reveal the robustness of the behavioral and neuropathological phenotypes, suggesting BACHD as a suitable fl-mhtt mouse model for preclinical studies. Additional analyses of BACHD mice provide novel insights into how mhtt may elicit neuropathogenesis. First, unlike previous fl-mhtt mouse models, BACHD mice reveal that the slowly progressive and selective pathogenic process in HD mouse brains can occur without early and diffuse nuclear accumulation of aggregated mhtt (i.e., as detected by immunostaining with the EM48 antibody). Instead, a relatively steady-state level of predominantly full-length mhtt and a small amount of mhtt N-terminal fragments are sufficient to elicit the disease process. Second, the polyglutamine repeat within fl-mhtt in BACHD mice is encoded by a mixed CAA-CAG repeat, which is stable in both the germline and somatic tissues including the cortex and striatum at the onset of neuropathology. Therefore, our results suggest that somatic repeat instability does not play a necessary role in selective neuropathogenesis in BACHD mice. In summary, the BACHD model constitutes a novel and robust in vivo paradigm for the investigation of HD pathogenesis and treatment.
Journal of Neuroscience 07/2008; 28(24):6182-95. · 7.11 Impact Factor
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ABSTRACT: Instrumental conditioning allows animals to learn about the consequences of their own actions, but the underpinning molecular mechanisms remain elusive. Here we show that the sphingosine-1-phosphate (S1P) receptor Gpr6 is selectively expressed in the striatopallidal neurons in the striatum. Gpr6-deficient mice showed reduced striatal cyclic AMP production in vitro and selective alterations in instrumental conditioning in vivo. Thus, Gpr6 is the first striatopallidal neuron-specific genetic regulator of instrumental conditioning in a mammal.
Nature Neuroscience 12/2007; 10(11):1395-7. · 15.53 Impact Factor
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ABSTRACT: A critical issue in understanding Huntington's disease (HD) pathogenesis is how the ubiquitously expressed mutant huntingtin (mhtt) with an expanded polyglutamine repeat can cause selective toxicity of striatal and cortical neurons. Two potential cellular models may contribute to such specificity: expression of mhtt in these vulnerable neurons alone may be sufficient to result in their dysfunction and/or degeneration (cell-autonomous model); or mhtt in other cell types can elicit pathological cell-cell interactions to cause the vulnerable neurons to become dysfunctional and be at risk for degeneration (cell-cell interaction model). To distinguish between these two models, we have selectively expressed a neuropathogenic fragment of mhtt-exon1 in striatal medium spiny neurons (MSNs) by crossing a conditional mouse model of HD with a striatal-specific Cre mouse line. In this striatal model of HD, we observed progressive and cell-autonomous nuclear accumulation of mhtt aggregates in MSNs. Surprisingly, unlike the mouse model expressing mhtt-exon1 in all the neurons in the brain, the striatal model lacks significant locomotor deficits and striatal neuropathology including gliosis and dark degenerating neurons. Electrophysiological findings from acutely dissociated MSNs revealed a cell-autonomous deficit in N-methyl-d-aspartate (NMDA) receptor sensitivity to Mg2+, a deficit also present in other mouse models of HD. In conclusion, this study provides the first in vivo genetic evidence that pathological cell-cell interactions are necessary for striatal pathogenesis in a conditional mouse model of HD, and suggests a ''two-hit'' hypothesis in which both cell-autonomous toxicity and pathological cell-cell interactions are critical to HD pathogenesis.
Molecular Neurodegeneration 02/2007; 2:8. · 4.28 Impact Factor
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ABSTRACT: A major challenge in systems neuroscience is to perform precise molecular genetic analyses of a single neuronal population in the context of the complex mammalian brain. Existing technologies for profiling cell type-specific gene expression are largely limited to immature or morphologically identifiable neurons. In this study, we developed a simple method using fluorescent activated cell sorting (FACS) to purify genetically labeled neurons from juvenile and adult mouse brains for gene expression profiling. We identify and verify a new set of differentially expressed genes in the striatonigral and striatopallidal neurons, two functionally and clinically important projection neuron subtypes in the basal ganglia. We further demonstrate that Ebf1 is a lineage-specific transcription factor essential to the differentiation of striatonigral neurons. Our study provides a general approach for profiling cell type-specific gene expression in the mature mammalian brain and identifies a set of genes critical to the function and dysfunction of the striatal projection neuron circuit.
Nature Neuroscience 04/2006; 9(3):443-52. · 15.53 Impact Factor
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ABSTRACT: This unit provides a comprehensive overview on the generation of transgenic mice using bacterial artificial chromosomes (BACs), and the application of BAC transgenic mice in neuroscience research. In the first section, advantages of the BAC transgenic approach compared to the conventional transgenic approach are summarized. In the second section, important considerations in designing BAC transgenic constructs are outlined. Four commonly used BAC transgenic construct designs are also outlined. Concepts of modifying BACs by homologous recombination in E. coli to introduce a variety of mutations into BACs, and important steps to characterize a modified BAC prior to the generation of transgenic mice are also presented. In the final section, some of the important applications of BAC transgenic mice in neuroscience research, including studying gene expression, gene function, mapping neuronal circuitry, and modeling human diseases, are described.
Current protocols in neuroscience / editorial board, Jacqueline N. Crawley ... [et al.] 06/2005; Chapter 5:Unit 5.20.
