Maciej Figiel

Mouse Models of Polyglutamine Diseases: Review and Data Table. Part I

Polyglutamine (polyQ) disorders share many similarities, such as a common mutation type in unrelated human causative genes, neurological character, and certain aspects of pathogenesis, including morphological and physiological neuronal alterations. The similarities in pathogenesis have been confirmed by findings that some experimental in vivo therapy approaches are effective in multiple models of polyQ disorders. Additionally, mouse models of polyQ diseases are often highly similar between diseases with respect to behavior and the features of the disease. The common features shared by polyQ mouse models may facilitate the investigation of polyQ disorders and may help researchers explore the mechanisms of these diseases in a broader context. To provide this context and to promote the understanding of polyQ disorders, we have collected and analyzed research data about the characterization and treatment of mouse models of polyQ diseases and organized them into two complementary Excel data tables. The data table that is presented in this review (Part I) covers the behavioral, molecular, cellular, and anatomic characteristics of polyQ mice and contains the most current knowledge about polyQ mouse models. The structure of this data table is designed in such a way that it can be filtered to allow for the immediate retrieval of the data corresponding to a single mouse model or to compare the shared and unique aspects of many polyQ models. The second data table, which is presented in another publication (Part II), covers therapeutic research in mouse models by summarizing all of the therapeutic strategies employed in the treatment of polyQ disorders, phenotypes that are used to examine the effects of the therapy, and therapeutic outcomes.

Mouse Models of Polyglutamine Diseases in Therapeutic Approaches: Review and Data Table. Part II

Mouse models of human diseases are created both to understand the pathogenesis of the disorders and to find successful therapies for them. This work is the second part in a series of reviews of mouse models of polyglutamine (polyQ) hereditary disorders and focuses on in vivo experimental therapeutic approaches. Like part I of the polyQ mouse model review, this work is supplemented with a table that contains data from experimental studies of therapeutic approaches in polyQ mouse models. The aim of this review was to characterize the benefits and outcomes of various therapeutic strategies in mouse models. We examine whether the therapeutic strategies are specific to a single disease or are applicable to more than one polyQ disorder in mouse models. In addition, we discuss the suitability of mouse models in therapeutic approaches. Although the majority of therapeutic studies were performed in mouse models of Huntington disease, similar strategies were also used in other disease models.

Huntington disease iPSCs show early molecular changes in intracellular signaling, the expression of oxidative stress proteins and the p53 pathway

ABSTRACT Huntington disease (HD) is a brain disorder characterized by the late onset of motor and cognitive symptoms, even though the neurons in the brain begin to suffer dysfunction and degeneration long before symptoms appear. There is currently no cure. Several molecular and developmental effects of HD have been identified using neural stem cells (NSCs) and differentiated cells, such as neurons and astrocytes. Still, little is known regarding the molecular pathogenesis of HD in pluripotent cells, such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). Therefore, we examined putative signaling pathways and processes involved in HD pathogenesis in pluripotent cells. We tested naïve mouse HD YAC128 iPSCs and two types of human HD iPSC that were generated from HD and juvenile-HD patients. Surprisingly, we found that a number of changes affecting cellular processes in HD were also present in undifferentiated pluripotent HD iPSCs, including the dysregulation of the MAPK and Wnt signaling pathways and the dysregulation of the expression of genes related to oxidative stress, such as Sod1. Interestingly, a common protein interactor of the huntingtin protein and the proteins in the above pathways is p53, and the expression of p53 was dysregulated in HD YAC128 iPSCs and human HD iPSCs. In summary, our findings demonstrate that multiple molecular pathways that are characteristically dysregulated in HD are already altered in undifferentiated pluripotent cells and that the pathogenesis of HD might begin during the early stages of life. Summary: This research demonstrates that dysregulation of signaling pathways is a very early event in the pathogenesis of Huntington disease and that these pathways are already dysregulated in cells at the stage of pluripotency.

A new humanized ataxin-3 knock-in mouse model combines the genetic features, pathogenesis of neurons and glia and late disease onset of SCA3/MJD.

Spinocerebellar ataxia type 3 (SCA3/MJD) is a neurodegenerative disease triggered by the expansion of CAG repeats in the ATXN3 gene. Here, we report the generation of the first humanized ataxin-3 knock-in mouse model (Ki91), which provides insights into the neuronal and glial pathology of SCA3/MJD. First, mutant ataxin-3 accumulated in cell nuclei across the Ki91 brain, showing diffused immunostaining and forming intranuclear inclusions. The humanized allele revealed expansion and contraction of CAG repeats in intergenerational transmissions. CAG mutation also exhibited age-dependent tissue-specific expansion, which was most prominent in the cerebellum, pons and testes of Ki91 animals. Moreover, Ki91 mice displayed neuroinflammatory processes, showing astrogliosis in the cerebellar white matter and the substantia nigra that paralleled the transcriptional deregulation of Serpina3n, a molecular sign of neurodegeneration and brain damage. Simultaneously, the cerebellar Purkinje cells in Ki91 mice showed neurodegeneration, a pronounced decrease in Calbindin D-28k immunoreactivity and a mild decrease in cell number, thereby modeling the degeneration of the cerebellum observed in SCA3. Moreover, these molecular and cellular neuropathologies were accompanied by late behavioral deficits in motor coordination observed in rotarod and static rod tests in heterozygous Ki91 animals. In summary, we created an ataxin-3 knock-in mouse model that combines the molecular and behavioral disease phenotypes with the genetic features of SCA3. This model will be very useful for studying the pathogenesis and responses to therapy of SCA3/MJD and other polyQ disorders.

Huntington Disease as a Neurodevelopmental Disorder and Early Signs of the Disease in Stem Cells

Huntington disease (HD) is a dominantly inherited disorder caused by a CAG expansion mutation in the huntingtin (HTT) gene, which results in the HTT protein that contains an expanded polyglutamine tract. The adult form of HD exhibits a late onset of the fully symptomatic phase. However, there is also a long presymptomatic phase, which has been increasingly investigated and recognized as important for the disease development. Moreover, the juvenile form of HD, evoked by a higher number of CAG repeats, resembles a neurodevelopmental disorder and has recently been the focus of additional interest. Multiple lines of data, such as the developmental necessity of HTT, its role in the cell cycle and neurogenesis, and findings from pluripotent stem cells, suggest the existence of a neurodevelopmental component in HD pathogenesis. Therefore, we discuss the early molecular pathogenesis of HD in pluripotent and neural stem cells, with respect to the neurodevelopmental aspects of HD.

Mouse polyQ database: a new online resource for research using mouse models of neurodegenerative diseases.

BackgroundThe polyglutamine (polyQ) family of disorders comprises 9 genetic diseases, including several types of ataxia and Huntington disease. Approximately two decades of investigation and the creation of more than 130 mouse models of polyQ disorders have revealed many similarities between these diseases. The disorders share common mutation types, neurological characteristics and certain aspects of pathogenesis, including morphological and physiological neuronal alterations. All of the diseases still remain incurable.DescriptionThe large volume of information collected as a result of the investigation of polyQ models currently represents a great potential for searching, comparing and translating pathogenesis and therapeutic information between diseases. Therefore, we generated a public database comprising the polyQ mouse models, phenotypes and therapeutic interventions tested in vivo. The database is available at http://conyza.man.poznan.pl/.ConclusionThe use of the database in the field of polyQ diseases may accelerate research on these and other neurodegenerative diseases and provide new perspectives for future investigation.

A novel cross‐talk between endothelin and ErbB receptors controlling glutamate transporter expression in astrocytes

J. Neurochem. (2012) 122, 844–855.

The Generation of Mouse and Human Huntington Disease iPS Cells Suitable for In vitro Studies on Huntingtin Function

Huntington disease (HD) is an incurable neurodegenerative disorder caused by expansion of CAG repeats in huntingtin (HTT) gene, resulting in expanded polyglutamine tract in HTT protein. Although, HD has its common onset in adulthood, subtle symptoms in patients may occur decades before diagnosis, and molecular and cellular changes begin much earlier, even in cells that are not yet lineage committed such as stem cells. Studies in induced pluripotent stem cell (iPSC) HD models have demonstrated that multiple molecular processes are altered by the mutant HTT protein and suggested its silencing as a promising therapeutic strategy. Therefore, we aimed to generate HD iPS cells with stable silencing of HTT and further to investigate the effects of HTT knock-down on deregulations of signaling pathways e.g., p53 downregulation, present in cells already in pluripotent state. We designed a gene silencing strategy based on RNAi cassette in piggyBAC vector for constant shRNA expression. Using such system we delivered and tested several shRNA targeting huntingtin in mouse HD YAC128 iPSC and human HD109, HD71, and Control iPSC. The most effective shRNA (shHTT2) reagent stably silenced HTT in all HD iPS cells and remained active upon differentiation to neural stem cells (NSC). When investigating the effects of HTT silencing on signaling pathways, we found that in mouse HD iPSC lines expressing shRNA the level of mutant HTT inversely correlated with p53 levels, resulting in p53 level normalization upon silencing of mutant HTT. We also found that p53 deregulation continues into the NSC developmental stage and it was reversed upon HTT silencing. In addition, we observed subtle effects of silencing on proteins of Wnt/β-catenin and ERK1/2 signaling pathways. In summary, we successfully created the first mouse and human shRNA-expressing HD iPS cells with stable and continuous HTT silencing. Moreover, we demonstrated reversal of HD p53 phenotype in mouse HD iPSC, therefore, the stable knockdown of HTT is well-suited for investigation on HD cellular pathways, and is potentially useful as a stand-alone therapy or component of cell therapy. In addition, the total HTT knock-down in our human cells has further implications for mutant allele selective approach in iPSC.

Chapter 64 – Mouse Models of SCA3 and Other Polyglutamine Repeat Ataxias

Polyglutamine (polyQ) hereditary ataxias comprise six disorders, including spinocerebellar ataxia type 1, type 2, Machado–Joseph disease, type 6, type 7, type 17, and dentatorubral-pallidoluysian atrophy. PolyQ ataxias are all neurological disorders, and their pathology is mainly related to dysfunction or loss of neurons in the central nervous system. The mechanisms of the disease are not fully understood and may include a gain and/or loss of function in the mutant protein, which becomes toxic to cells. Transgenic mouse models are very powerful tools for exploring polyQ ataxias. These models are created to study the following two aspects: the disease process and potential therapies for hereditary ataxias that are currently incurable. Therefore, in this chapter, we review the variety of mouse models of polyQ ataxias and discuss the aspects of ataxia pathogenesis that have been discovered via mouse models of particular diseases. Moreover, we review studies that test the feasibility of particular therapeutic strategies in mouse models of polyQ ataxia. This chapter complements our other reviews and databases and has been intensively updated with new models and therapeutic approaches.