Abstract:
     Microsatellite expansions cause a number of dominantly-inherited neurological diseases including myotonic dystrophy (DM1 and DM2), Huntington's disease (HD and HDL2) and several forms of spinocerebellar ataxia (SCA). Expansions located in coding-regions cause dominant protein gain-of-function effects and non-coding expansions (DM and DM2) produce toxic RNA gain-of-function effects that in muscle have been shown to alter RNA splicing activities of MBNL and CELF proteins. We previously reported that a (CTG)n expansion causes spinocerebellar ataxia type 8 (SCA8). Because the SCA8 expansion is transcribed, alternatively spliced, and polyadenylated in the CTG orientation we initially proposed that SCA8 is caused by an RNA gain-of-function mechanism similar to myotonic dystrophy. To elucidate the molecular events that cause SCA8, we developed a BAC transgenic mouse model in which the full length human SCA8 gene is expressed using its endogenous promoter. (CTG)116 expansion, but not (CTG)11 control lines, develop a progressive neurological phenotype and a loss of cerebellar cortical inhibition. Surprisingly, we found 1C2-intranuclear inclusions in Purkinje cells in SCA8 expansion mice and human SCA8 autopsy tissue result from translation of a nearly pure polyglutamine protein encoded on a previously unidentified anti-parallel transcript spanning the repeat in the CAG direction. The neurological phenotype found in the SCA8 BAC expansion lines but not BAC control lines demonstrates the pathogenicity of the (CTG•CAG)n expansion.
     We now present three lines of evidence that SCA8 CUGexp transcripts cause RNA gain of function effects in the CNS. First, we demonstrate SCA8 CUGexp transcripts form ribonuclear inclusions that co-localize with MBNL1. Second, we show that genetic loss of Mbnl1 enhances motor coordination deficits in SCA8 mice. Third we show the GABA-A transporter-4 (Gabt4) gene, which is dramatically upregulated in SCA8, is a misregulated MBNL/CELF splicing target. These data demonstrate for the first time that CUGexp transcripts dysregulate MBNL/CELF regulated pathways in the brain and provide mechanistic insight into the CNS effects of other CUGexp disorders (DM, HDL2). While functional evidence for RNA gain-of-function effects is presented here, the additional discovery of intranuclear polyglutamine inclusions in SCA8 suggests disease pathogenesis is mediated by toxic gain-of-function mechanisms at both the protein and RNA levels. Additionally, the growing number of bidirectionally-expressed genes in the genome suggests unrecognized CUGexp RNAs contribute to some of the polyglutamine CAG•CTG disorders.

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The lecture will begin at noon in 3-100 Mayo Auditorium. links for map and directions to the location: campus location / room location. The lecture will also be webcast live; to view online use link https://umconnect.umn.edu/lillehei/. Non-UofM affiliated viewers can log in as guests.

Refreshments will be provided

download lecture flyer

Abstract:
The transcriptional corepressor BCOR regulates gene expression in association with a complex of proteins capable of epigenetic chromatin modification. Mutations in human BCOR result in the X-linked Oculofaciocardiodental (OFCD) syndrome that involves developmental defects in multiple systems, including the ocular, skeletal, and cardiovascular systems. To determine the role of Bcor in mouse development, we have generated Bcor loss-of-function alleles in embryonic stem (ES) cells and in mice. In vitro differentiation of ES cells harboring Bcor loss-of-function alleles demonstrated a role for Bcor in the regulation of gene expression very early in ES cell differentiation into ectoderm, mesoderm, and downstream hematopoietic lineages. To unravel Bcor's complex role during early embryogenesis and specifically in cardiovascular development, we are currently generating ubiquitous and cardiac-specific Bcor knockout mice. Initial findings reveal that ubiquitous Bcor inactivation in mice results in male lethality prior to embryonic turning and late gestation lethality of heterozygous females. Meanwhile, Bcor inactivation in males in the neural crest cell lineage results in perinatal lethality possibly due to observed cardiovascular defects.

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The lecture will begin at noon in 3-100 Mayo Auditorium. links for map and directions to the location: campus location / room location. The lecture will also be webcast live; to view online use link https://umconnect.umn.edu/lillehei/. Non-UofM affiliated viewers can log in as guests.

A flyer for the lecture is attached; please feel free to print and distribute it to any who may be interested.

Refreshments will be provided.

Abstract:
We have discovered that ursodeoxycholic acid, an endogenous hydrophilic bile acid in humans, is a potent antiapoptotic agent. Over the last several years we have characterized the effects and mechanism by which ursodeoxycholic acid, as well as its taurine and glycine conjugates, functions to inhibit apoptosis. We have studied several animal models that are relatively accurate to their human counterparts. Specifically, we have used ursodeoxycholic acid as a therapeutic agent to treat chemical and transgenic models of Huntington’s disease, as well as head trauma, acute stroke and cell transplantation for Parkinson’s disease. The common characteristic shared by these disorders and many more human diseases is the role that apoptosis plays in disease progression. In each case, we have determined that the bile acid is a markedly potent antiapoptotic agent that significantly improves the neurologic status in each of these disorders. We have determined the common molecular mechanisms by which ursodeoxycholic acid acts to preserve cell survival and cell function. In fact, ursodeoxycholic acid stabilizes the mitochondrial membrane and prevents apoptosis by inhibiting the permeability transition, mitochondrial membrane depolarization and channel formation, production of reactive oxygen species, release of cytochrome c, caspase activation, and cleavage of the nuclear enzyme poly(ADP-ribose) polymerase. More recently, we have shown that ursodeoxycholic acid and its conjugates, inhibit the E2F-1/p53 apoptotic pathway and regulate NF-kB expression, thus modulating the expression of antiapoptotic Bcl-2 family members. As a therapeutic agent, ursodeoxycholic acid is unique in that it is associated with no significant toxicity, crosses the blood-brain barrier and can be delivered intravenously, orally, or intrathecally. There are, in fact, numerous disease states that could potentially benefit including acute myocardial infarction, certain autoimmune diseases, and the many acute and chronic neurodegenerative disorders for which there is little available treatment. My laboratory has studies going on in each of these areas, in addition to studying the basic mechanisms of function.

The lecture will begin at noon in 3-100 Mayo Auditorium. A map and directions to the location are available at http://www1.umn.edu/twincities/maps/MMA/index.html A flier for the lecture is posted above; please feel free to print and distribute it to any who may be interested.

Abstract:
Coronary blood flow is regulated in response to changing myocardial metabolic requirements on a beat to beat basis. The principle mechanism for metabolic vasoregulation in the coronary circulation involves ATP sensitive potassium channels which open in response to a decrease in energy state of the cell and thereby cause vasodilation with an increase in blood flow. Adenosine produced by the myocardium and nitric oxide (NO) generated by the endothelium provide redundant mechanisms for regulation of coronary vascular resistance. These redundant systems are not apparent in the normal coronary circulation, but become evident when ATP sensitive potassium channels are inhibited or when ischemia causes maximal activation of the ATP sensitive potassium channels. In the setting of heart failure secondary to cardiomyopathy, coronary blood flow is depressed in parallel with a decrease of myocardial oxygen consumption. The decreased oxygen consumption of the failing heart results, at least in part, from increased production of NO by inducible NO synthase (NOS). NO competes with oxygen at cytochrome C oxidase, thereby inhibiting myocardial oxygen uptake. NO produced by inducible NOS has greater potency for inhibiting mitochondrial respiration then does NO produced by endothelial NOS, likely because myoglobin scavenges NO entering the cardiac myocyte, thereby preventing the NO from reaching the mitochondria. Inhibition of respiration by NO causes cytosolic free ADP to increase in order to drive respiration, so that inhibition of NO synthase results in lower ADP levels at any given level of cardiac work.

A link to download a flier for the lecture is above; please feel free to print and distribute it to any who may be interested.

Refreshments will be provided.

Abstract:
Currently, 3 million Americans suffer from heart failure and 500,000 new cases are diagnosed annually. An even greater 5 million people have Alzheimer’s in the US. Some but not all of these conditions are viewed as common protein misfolding diseases, whose mechanism, pathophysiology and therapies remain elusive goals in the genomic era. Added to these are many tens of thousands of patients suffering from a variety of other neurodegenerative diseases that are characterized by misfolding and aggregation of particular proteins. These diseases inflict severe suffering on patients and their families and cost many hundreds of billions of dollars in treatment every year.

The foundation of this lecture rests on our recent demonstration that the R120G mutation in the small human heat shock protein αB-crystallin (CryAB, HSPB5) results in aggregation-induced cardiomyopathy in a transgenic mouse model published in Cell. The cardiomyopathy is dramatically reversed in animals with a hypomorphic mutation in glucose-6-phosphate dehydrogenase(G6PD). Since G6PD is the major generator of reduced NADPH in the cell, this provides direct evidence to support ‘reductive stress’ as a causative mechanism in hR120G induced cardiomyopathy. Reductive stress has been elegantly demonstrated in lower eukaryotes, but this has not been previously demonstrated in mammals and/or disease states. If successful, the work by Dr. Benjamin and collaborators seeks to address this unconventional hypothesis that might ultimately lead to new diagnostics and therapies, termed ‘antireductants’ for human diseases including heart failure.

Refreshments will be provided.

Abstract:
G protein-receptor kinases (GRKs) in the heart have been shown to be important not only in signal transduction pathways but also in cardiac function. For example, in chronic heart failure, increased GRK2 expression and activity has been shown to be involved in pathogenesis and is a novel target for heart failure therapy. The focus of our research over the last decade has been GRK2 in the heart, however other GRKs are present most notably GRK5 and it appears to play a distinct and novel role in cardiac biology. Our latest data regarding these two GRKs in cardiac pathology will be presented.

A flier for the lecture is posted above; please feel free to print and distribute it to any who may be interested.

Refreshments will be provided.

Objective:
Genomic approaches have yielded major insights into the pathogenesis of human cardiovascular disorders. This lecture will present examples of gene expression and SNP association studies that elucidate mechanisms of human cardiac remodeling and heart failure.

The lecture will begin at noon in 3-100 Mayo Auditorium. A map and directions to the location are available at http://www1.umn.edu/twincities/maps/MMA/index.html

A link to download a flyer for the lecture is posted above; please feel free to print and distribute it to any who may be interested.

Refreshments will be provided.

Summary:
    Ly-6Chi monocytes are key contributors to atherosclerosis in mice. However, how Ly-6Chi monocytes selectively accumulate in atherosclerotic lesions is largely unknown. Monocyte homing to sites of atherosclerosis is primarily initiated by rolling on P- and E-selectin expressed on endothelium. In our study, we found Ly-6Chi monocytes expressed a higher level of PSGL-1, and had enhanced binding to P- and E-selectin, compared to Ly-6Clo monocytes. In vivo, ApoE–/– mice lacking PSGL-1 had impaired Ly-6Chi monocyte recruitment to atherosclerotic lesions. Moreover, ApoE–/–/PSGL-1–/– mice exhibited significantly reduced monocyte infiltration in wire injury–induced neointima and in atherosclerotic lesions. Our study indicate that PSGL-1 is a new marker for Ly-6Chi monocytes and a major determinant for Ly-6Chi cell recruitment to sites of atherosclerosis in mice.

The lecture will begin at noon in 3-100 Mayo Auditorium. A map and directions to the location are available at http://www1.umn.edu/twincities/maps/MMA/index.html

Refreshments will be provided.

>> more info about Dr. Tapscott    >> lab website

Summary:
The expression of MyoD is sufficient to convert a fibroblast to a skeletal muscle cell. A combination of expression analysis and chromatin immunoprecipitation studies show that MyoD directly activates genes expressed both early and late during the program of cell differentiation. Temporal patterning of gene expression is achieved, at least in part, through a feed-forward mechanism: MyoD is sufficient to activate early genes, however, the activation of late genes requires both MyoD and additional transcription factors induced by MyoD. In the absence of MyoD, the other participating transcription factors are not sufficient to efficiently initiate expression of the target genes. This is due, at least in part, because these factors cannot bind to the promoters in the absence of MyoD, either because they cannot locate the promoters in chromatin or because they cannot recruit necessary chromatin remodeling proteins, or both. At a subset of promoters, the homeobox protein Pbx is necessary for MyoD to localize a gene within chromatin and initiate transcription. This demonstrates a specific mechanism of targeting MyoD to loci in inactive chromatin and reveals a critical role of homeodomain proteins in marking specific genes for activation in the muscle lineage. Gene suppression by Myod-induced myogenesis occurs largely through induction of micro-RNAs. Supported by NIAMS.

The lecture will begin at noon in 3-100 Mayo Auditorium. A map and directions to the location are available at http://www1.umn.edu/twincities/maps/MMA/index.html

Refreshments will be provided.