polyQ Stretch Research Articles

TR-FRET assays of Huntingtin protein fragments reveal temperature and polyQ length-dependent conformational changes.

Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) technology is a widely used immunoassay that enables high-throughput quantitative measurements of proteins of interest. One of the well established examples is the TR-FRET assay for mutant huntingtin protein (HTT), which is the major cause of the neurodegenerative Huntington's disease (HD). To measure the mutant HTT protein, the published assays utilize a polyQ antibody, MW1, paired with HTT N-terminal antibodies. MW1 has much higher apparent affinity to mutant HTT with expanded polyQ stretch than to wild-type HTT with shorter polyQ, and thus the assays detect mutant HTT preferentially. Here we report a reversible temperature dependent change of TR-FRET signals for HTT N-terminal fragments: the signals become higher when the temperature is lowered from room temperature to 4°C. Interestingly, the temperature sensitivity of the TR-FRET signals is much higher for the Q25 (wild-type) than for the Q72 (mutant) protein. We further revealed that it is likely due to a temperature and polyQ length-dependent structural or spatial change of HTT, which is potentially useful for understanding polyQ structure and toxicity.

Large-Scale RNA Interference Screening in Mammalian Cells Identifies Novel Regulators of Mutant Huntingtin Aggregation

In polyglutamine (polyQ) diseases including Huntington's disease (HD), mutant proteins containing expanded polyQ stretch form aggregates in neurons. Genetic or RNAi screenings in yeast, C. elegans or Drosophila have identified multiple genes modifying polyQ aggregation, a few of which are confirmed effective in mammals. However, the overall molecular mechanism underlying polyQ protein aggregation in mammalian cells still remains obscure. We here perform RNAi screening in mouse neuro2a cells to identify mammalian modifiers for aggregation of mutant huntingtin, a causative protein of HD. By systematic cell transfection and automated cell image analysis, we screen ∼12000 shRNA clones and identify 111 shRNAs that either suppress or enhance mutant huntingtin aggregation, without altering its gene expression. Classification of the shRNA-targets suggests that genes with various cellular functions such as gene transcription and protein phosphorylation are involved in modifying the aggregation. Subsequent analysis suggests that, in addition to the aggregation-modifiers sensitive to proteasome inhibition, some of them, such as a transcription factor Tcf20, and kinases Csnk1d and Pik3c2a, are insensitive to it. As for Tcf20, which contains polyQ stretches at N-terminus, its binding to mutant huntingtin aggregates is observed in neuro2a cells and in HD model mouse neurons. Notably, except Pik3c2a, the rest of the modifiers identified here are novel. Thus, our first large-scale RNAi screening in mammalian system identifies previously undescribed genetic players that regulate mutant huntingtin aggregation by several, possibly mammalian-specific mechanisms.

Interactions of ataxin-3 with its molecular partners in the protein machinery that sorts protein aggregates to the aggresome

Ataxin-3 (AT3) is the protein that triggers the inherited neurodegenerative disorder spinocerebellar ataxia type 3 when its polyglutamine (polyQ) stretch close to the C-terminus exceeds a critical length. AT3 consists of the N-terminal globular Josephin domain (JD) and the C-terminal disordered one. It cleaves isopeptide bonds between ubiquitin monomers, an event involved in protein quality control mechanisms. AT3 has been implicated in the pathway that sorts aggregated protein to aggresomes via microtubules, in which dynein and histone deacetylase 6 (HDAC6) also seem to be involved. By taking advantage of small angle X-ray scattering (SAXS) and surface plasmon resonance (SPR), we have investigated the interaction of AT3 with tubulin and HDAC6. Based on SAXS results, the AT3 oligomer, consisting of 6–7 subunits, tightly binds to the tubulin hexameric oligomer in a “parallel” fashion. By SPR analysis we have demonstrated that AT3 binds to tubulin dimer with a 50nM affinity. Binding fits with a Langmuir 1:1 model and involves a single binding interface. Nevertheless, the interaction surface consists of three distinct, discontinuous tubulin-binding regions (TBR), one located in the JD, and the two others in the disordered domain, upstream and downstream of the polyQ stretch. In the absence of any of the three TBRs, the affinity is drastically reduced. By SPR we have also provided the first evidence of direct binding of AT3 to HDAC6, with affinity in the range 0.1–1μM. These results shed light on the interactions among the components of the transport machinery that sorts aggregate protein to the aggresome, and pave the way to in vivo studies aimed at further clarifying their roles.

Peptide-Based Therapeutic Approaches for Treatment of the Polyglutamine Diseases

The polyglutamine (polyQ) diseases including Huntington's disease and spinocerebellar ataxias are a group of inherited neurodegenerative diseases that are caused by an abnormal expansion of the polyQ stretch in disease-causative proteins. The expanded polyQ stretches are intrinsically unstable and are prone to form insoluble aggregates and inclusion bodies. Recent studies have revealed that the expanded polyQ proteins gain cytotoxicity during the aggregation process, which may possibly cause detrimental effects on a wide range of essential cellular functions leading to eventual neuronal degeneration. Based on the pathogenic mechanism of the polyQ diseases, several therapeutic approaches have been proposed to date. Among them, here we focus on peptide-based approaches that target either aggregate formation of the polyQ proteins or abnormal cellular processes induced by the expanded polyQ proteins. Although both approaches are effective in suppressing cytotoxicity of the abnormal polyQ proteins and the disease phenotypes of animal models, the former approach is more attractive since it targets the most upstream change occurring in the polyQ diseases, and is therefore expected to be effective against various downstream functional abnormalities in a broad range of polyQ diseases. One of the major current problems that must be overcome for development of peptide-based therapies of the polyQ diseases is the issue of brain delivery, which is also discussed in this article. We hope that in the near future effective therapies are developed, and bring hope to many patients suffering from the currently untreatable polyQ diseases.

Expanded Polyglutamine-containing N-terminal Huntingtin Fragments Are Entirely Degraded by Mammalian Proteasomes

Huntington disease is a neurodegenerative disorder caused by an expanded polyglutamine (polyQ) repeat within the protein huntingtin (Htt). N-terminal fragments of the mutant Htt (mHtt) proteins containing the polyQ repeat are aggregation-prone and form intracellular inclusion bodies. Improving the clearance of mHtt fragments by intracellular degradation pathways is relevant to obviate toxic mHtt species and subsequent neurodegeneration. Because the proteasomal degradation pathway has been the subject of controversy regarding the processing of expanded polyQ repeats, we examined whether the proteasome can efficiently degrade Htt-exon1 with an expanded polyQ stretch both in neuronal cells and in vitro. Upon targeting mHtt-exon1 to the proteasome, rapid and complete clearance of mHtt-exon1 was observed. Proteasomal degradation of mHtt-exon1 was devoid of polyQ peptides as partial cleavage products by incomplete proteolysis, indicating that mammalian proteasomes are capable of efficiently degrading expanded polyQ sequences without an inhibitory effect on the proteasomal activity.

DNAJB6 is a peptide-binding chaperone which can suppress amyloid fibrillation of polyglutamine peptides at substoichiometric molar ratios

Expanded polyglutamine (polyQ) stretches lead to protein aggregation and severe neurodegenerative diseases. A highly efficient suppressor of polyQ aggregation was identified, the DNAJB6, when molecular chaperones from the HSPH, HSPA, and DNAJ families were screened for huntingtin exon 1 aggregation in cells (Hageman et al. in Mol Cell 37(3):355–369, 2010). Furthermore, also aggregation of polyQ peptides expressed in cells was recently found to be efficiently suppressed by co-expression of DNAJB6 (Gillis et al. in J Biol Chem 288:17225–17237, 2013). These suppression effects can be due to an indirect effect of DNAJB6 on other cellular components or to a direct interaction between DNAJB6 and polyQ peptides that may depend on other cellular components. Here, we have purified the DNAJB6 protein to investigate the suppression mechanism. The purified DNAJB6 protein formed large heterogeneous oligomers, in contrast to the more canonical family member DNAJB1 which is dimeric. Purified DNAJB6 protein, at substoichiometric molar ratios, efficiently suppressed fibrillation of polyQ peptides with 45°Q in a thioflavin T fibrillation. No suppression was obtained with DNAJB1, but with the closest homologue to DNAJB6, DNAJB8. The suppression effect was independent of HSPA1 and ATP. These data, based on purified proteins and controlled fibrillation in vitro, strongly suggest that the fibrillation suppression is due to a direct protein–protein interaction between the polyQ peptides and DNAJB6 and that the DNAJB6 has unique fibrillation suppression properties lacking in DNAJB1. Together, the data obtained in cells and in vitro support the view that DNAJB6 is a peptide-binding chaperone that can interact with polyQ peptides that are incompletely degraded by and released from the proteasome.Electronic supplementary materialThe online version of this article (doi:10.1007/s12192-013-0448-5) contains supplementary material, which is available to authorized users.

Pharmacological Activation of Sirt1 Ameliorates Polyglutamine-Induced Toxicity through the Regulation of Autophagy

Intracellular accumulation of polyglutamine (polyQ)-expanded Huntingtin (Htt) protein is a hallmark of Huntington’s disease (HD). This study evaluated whether activation of Sirt1 by the anti-cancer agent, β-lapachone (β-lap), induces autophagy in human neuroblastoma SH-SY5Y cells, thereby reducing intracellular levels of polyQ aggregates and their concomitant cytotoxicity. Treatment of cells with β-lap markedly diminished the cytotoxicity induced by forced expression of Htt exon 1 containing a pathogenic polyQ stretch fused to green fluorescent protein (HttEx1(97Q)-GFP). β-lap increased autophagy in SH-SY5Y cells, as evidenced by the increased formation of LC3-II and autolysosomes. Furthermore, β-lap reduced HttEx1(97Q)-GFP aggregation, which was significantly prevented by co-incubation with 3-methyladenine, an inhibitor of autophagy. β-lap increased Sirt1 activity, as shown by the increased deacetylation of the Sirt1 substrates, PARP-1 and Atg5, and the nuclear translocation of FOXO1. Both the induction of autophagy and attenuation of HttEx1(97Q)-GFP aggregation by β-lap were significantly prevented by co-incubation with sirtinol, a general sirtuin inhibitor or by co-transfection with shRNA against Sirt1. The pro-autophagic actions of β-lap were further investigated in a transgenic Caenorhabditis elegans (C. elegans) line that expressed Q67 fused to cyanine fluorescent protein (Q67). Notably, β-lap reduced the number of Q67 puncta and restored Q67-induced defects in motility, which were largely prevented by pre-treatment with RNAi against sir-2.1, the C. elegans orthologue of Sirt1. Collectively, these data suggest that β-lap induces autophagy through activation of Sirt1, which in turn leads to a reduction in polyQ aggregation and cellular toxicity. Thus, β-lap provides a novel therapeutic opportunity for the treatment of HD.

RNA toxicity in polyglutamine disorders: concepts, models, and progress of research.

In Huntington's disease and other polyglutamine (polyQ) disorders, mutant proteins containing a long polyQ stretch are well documented as the trigger of numerous aberrant cellular processes that primarily lead to degeneration and, ultimately, the death of neuronal cells. However, mutant transcripts containing expanded CAG repeats may also be toxic and contribute to cellular dysfunction. The exact nature and importance of RNA toxicity in polyQ diseases are only beginning to be recognized, and the first insights have mainly resulted from studies using simple model systems. In this review, we briefly present the basic mechanisms of protein toxicity in polyQ disorders and RNA toxicity in myotonic dystrophy type 1 and discuss recent results suggesting that the pathogenesis of polyQ diseases may also be mediated by mutant transcripts. This review is focused on the experimental systems used thus far to demonstrate RNA toxicity in polyQ disorders and the design of new systems that will be more relevant to the human disease situation and capable of separating RNA toxicity from protein toxicity.

Inhibition of protein misfolding/aggregation using polyglutamine binding peptide QBP1 as a therapy for the polyglutamine diseases.

Protein misfolding and aggregation in the brain have been recognized to be crucial in the pathogenesis of various neurodegenerative diseases, including Alzheimer's, Parkinson's, and the polyglutamine (polyQ) diseases, which are collectively called the "protein misfolding diseases". In the polyQ diseases, an abnormally expanded polyQ stretch in the responsible proteins causes the proteins to misfold and aggregate, eventually resulting in neurodegeneration. Hypothesizing that polyQ protein misfolding and aggregation could be inhibited by molecules specifically binding to the expanded polyQ stretch, we identified polyQ binding peptide 1 (QBP1). We show that QBP1 does, indeed, inhibit misfolding and aggregation of the expanded polyQ protein in vitro. Furthermore overexpression of QBP1 by the crossing of transgenic animals inhibits neurodegeneration in Drosophila models of the polyQ diseases. We also introduce our attempts to deliver QBP1 into the brain by administration using viral vectors and protein transduction domains. Interestingly, recent data suggest that QBP1 can also inhibit the misfolding/aggregation of proteins responsible for other protein misfolding diseases, highlighting the potential of QBP1 as a general therapeutic molecule for a wide range of neurodegenerative diseases. We hope that in the near future, aggregation inhibitor-based drugs will be developed and bring relief to patients suffering from these currently intractable protein misfolding diseases.

Length and Sequence Dependence in the Association of Htt Protein with Lipid Bilayers

There is a fundamental gap in our understanding of how aggregates formed by mutant Huntington (htt) protein with varying polyQ repeats gain toxic properties causing Huntington's disease (HD). From experimental studies, it has been known that the central and the most important step associated with toxicity is the binding of mutant htt and its aggregates to lipids. It is also known that flanking amino acid sequences around the polyglutamine stretch directly affects the interaction with the lipid bilayer. The exact nature of these interactions and the key steps of how these flanking sequences and polyglutamate length affect structure of lipid bilayers are not known. In this study, we use atomistic molecular dynamics simulations to study the nature of interaction between the various mutant htt protein with the associated flanking sequences around the polyQ stretch and we explore the changes in these interactions with lipid bilayers by varying the length of the polyQ stretch as well. We also study the effect of lipid compositions on these interactions. Initial results from adsorption simulations of polyQ peptides show membrane thinning and changes in the area of lipid head groups where the protein adsorbs. Although we do not observe complete disruption of membrane structure, we see significant compensation effects in the bottom leaflet of the membrane. We compare these effects across the different flanking sequences and various lengths of polyQ stretches and observe varying degrees of changes in the structure of the lipid bilayer.

Small non-coding RNAs add complexity to the RNA pathogenic mechanisms in trinucleotide repeat expansion diseases

Trinucleotide-repeat expansion diseases (TREDs) are a group of inherited human genetic disorders normally involving late-onset neurological/neurodegenerative affectation. Trinucleotide-repeat expansions occur in coding and non-coding regions of unique genes that typically result in protein and RNA toxic gain of function, respectively. In polyglutamine (polyQ) disorders caused by an expanded CAG repeat in the coding region of specific genes, neuronal dysfunction has been traditionally linked to the long polyQ stretch. However, a number of evidences suggest a detrimental role of the expanded/mutant mRNA, which may contribute to cell function impairment. In this review we describe the mechanisms of RNA-induced toxicity in TREDs with special focus in small-non-coding RNA pathogenic mechanisms and we summarize and comment on translational approaches targeting the expanded trinucleotide-repeat for disease modifying therapies.

The Relationship between Aggregation and Toxicity of Polyglutamine-Containing Ataxin-3 in the Intracellular Environment of Escherichia coli

Several neurodegenerative diseases are triggered by proteins containing a polyglutamine (polyQ) stretch expanded beyond a critical threshold. Among these, ataxin-3 (AT3) is the causative agent of spinocerebellar ataxia type-3. We expressed three authentic AT3 variants in Escherichia coli: one normal (AT3-Q24), one expanded (AT3-Q55) and one truncated immediately upstream of the polyQ (AT3-291Δ). Then, based on growth rate reduction, we quantified protein toxicity. We show that AT3-Q55 and -291Δ strongly reduced the growth rate in the early stages (2–4 h), unlike AT3-Q24. This correlated well with the appearance of soluble cytosolic oligomers, but not with the amount of insoluble protein in inclusion bodies (IBs). The impact of AT3-291Δ on cell growth suggests an intrinsic toxicity of the AT3 fragment. Besides the typical Fourier Transform Infrared Spectroscopy (FTIR) signal for intermolecular β-sheets, the expanded form displayed an additional infrared signature, which was assigned to glutamine side-chain hydrogen bonding and associated with SDS-insoluble fibrils. The elongation of the latter was monitored by Atomic Force Microscopy (AFM). This mirrors the well-known in vitro two-step aggregation pattern of expanded AT3. We also demonstrated that final aggregates of strains expressing expanded or truncated AT3 play a protective role against toxicity. Furthermore, our findings suggest that the mechanisms of toxicity are evolutionarily conserved.

Aneuploidy causes proteotoxic stress in yeast

Gains or losses of entire chromosomes lead to aneuploidy, a condition tolerated poorly in all eukaryotes analyzed to date. How aneuploidy affects organismal and cellular physiology is poorly understood. We found that aneuploid budding yeast cells are under proteotoxic stress. Aneuploid strains are prone to aggregation of endogenous proteins as well as of ectopically expressed hard-to-fold proteins such as those containing polyglutamine (polyQ) stretches. Protein aggregate formation in aneuploid yeast strains is likely due to limiting protein quality-control systems, since the proteasome and at least one chaperone family, Hsp90, are compromised in many aneuploid strains. The link between aneuploidy and the formation and persistence of protein aggregates could have important implications for diseases such as cancer and neurodegeneration.

Hsp40 Gene Therapy Exerts Therapeutic Effects on Polyglutamine Disease Mice via a Non-Cell Autonomous Mechanism

The polyglutamine (polyQ) diseases such as Huntington’s disease (HD), are neurodegenerative diseases caused by proteins with an expanded polyQ stretch, which misfold and aggregate, and eventually accumulate as inclusion bodies within neurons. Molecules that inhibit polyQ protein misfolding/aggregation, such as Polyglutamine Binding Peptide 1 (QBP1) and molecular chaperones, have been shown to exert therapeutic effects in vivo by crossing of transgenic animals. Towards developing a therapy using these aggregation inhibitors, we here investigated the effect of viral vector-mediated gene therapy using QBP1 and molecular chaperones on polyQ disease model mice. We found that injection of adeno-associated virus type 5 (AAV5) expressing QBP1 or Hsp40 into the striatum both dramatically suppresses inclusion body formation in the HD mouse R6/2. AAV5-Hsp40 injection also ameliorated the motor impairment and extended the lifespan of R6/2 mice. Unexpectedly, we found even in virus non-infected cells that AAV5-Hsp40 appreciably suppresses inclusion body formation, suggesting a non-cell autonomous therapeutic effect. We further show that Hsp40 inhibits secretion of the polyQ protein from cultured cells, implying that it inhibits the recently suggested cell-cell transmission of the polyQ protein. Our results demonstrate for the first time the therapeutic effect of Hsp40 gene therapy on the neurological phenotypes of polyQ disease mice.

Role of androgen receptor polyQ chain elongation in Kennedy's disease and use of natural osmolytes as potential therapeutic targets

Instability of CAG triplet repeat encoding polyglutamine (polyQ) stretches in the gene for target protein has been implicated as a putative mechanism in several inherited neurodegenerative diseases. Expansion of polyQ chain length in the androgen receptor (AR) causes spinal and bulbar muscular atrophy (SBMA) or Kennedy's disease. Although the mechanisms underlying gain-of-neurotoxic function are not completely understood, suggested pathological mechanisms of SBMA involve the formation of AR nuclear and cytoplasmic aggregates, a characteristic feature of patients with SBMA. The fact that certain AR coactivators are sequestered into the nuclear inclusions in SBMA possibly through protein-protein interactions supports the notion that AR transcriptional dysregulation may be a potential pathological mechanism leading to SBMA. AR conformational states associated with aberrant polyQ tract also modulate the interaction of AR with several coactivators. In many cases, such diseases can be treated through protein replacement therapy; however, because recombinant proteins do not cross the blood-brain barrier, the effectiveness of such therapies is limited in case of neurodegenerative diseases that warrant alternative therapeutic approaches. Among different approaches, inhibiting protein aggregation with small molecules that can stimulate protein folding and reverse aggregation are the most promising ones. Thus, naturally occurring osmolytes or "chemical chaperones" that can easily cross the blood-brain barrier and stabilize the functional form of a mutated protein by shifting the folding equilibrium away from degradation and/or aggregation is a useful therapeutic approach. In this review, we discuss the role of polyQ chain length extension in the pathophysiology of SBMA and the use of osmolytes as potential therapeutic tool.

P02 In vivo efficacy of (CUG)n oligonucleotides to treat HD

BackgroundHuntington's disease (HD) is caused by an expanded (CAG)n tract in the Huntingtin gene (HTT) that is translated into an expanded polyglutamine (polyQ) stretch in the protein. The polyQ stretch...

A10 Huntingtin, from 800 million years ago to the day after tomorrow

Huntingtin (htt) is the ancient protein product of the Huntington9s disease (HD) gene. The gene contains a polymorphic tri-nucleotide CAG repeat that is translated into polyglutamine amino acid (polyQ) residues in the protein. When this polyQ stretch at the 18 aminoacid (aa) position of the protein expands to over 39 residues, HD occurs, a fatal, genetically dominant, neurodegenerative disease. The CAG repeats are well conserved in deuterostomes, which suggests that they are an ancestral feature retained during the evolution of the protein. Htt carries a number of specific activities in the adult brain; for instance, it promotes transcription of neuronal genes among which is the BDNF, a neurotrophin critical for the survival and activity of cortical and striatal neurons that degenerate in HD. This presentation will highlight the power of combining evolutionary and developmental approaches to the study of the biology of disease-genes and will review the more recent discovery of a function for htt in neuroepithelial stem cells and its implication in HD pathogenesis.

F12 Abnormal regulation of macrophage-derived transforming growth factor: β 1 (TGF-β1) production in Huntington disease

<h3>Background</h3> Huntington9s Disease (HD) is a neurodegenerative disorder caused by a trinucleotide repeat (CAG) expansion within Huntingtin gene (HTT) that results in a polyglutamine (polyQ) stretch in N-terminal region of huntingtin (Htt). Mutant Htt (mHtt) interfers with several molecular pathways, including cell signalling, transcriptional regulation, axonal transport and neurotrophins production and release. Emerging evidence indicates that reduced levels of neurotrophic factors, including brain derived neurotrophic factor and transforming growth factor-β 1 (TGF-β1) are linked to the pathogenesis of HD. Previous study from our lab and collaborators, demonstrated that TGF-β1 levels varied throughout disease course in both central and peripheral tissues with a significant reduction at early stage of the disease. <h3>Aim</h3> Our aim was to clarify the contribution of each whole blood cell subset at producing TGF-β1 in the periphery and to determine whether TGF-β1 may have potential utility as a marker of disease progression. <h3>Methods</h3> Monocytes-derived macrophages from 81 HD individuals and age-matched healthy controls (n=30) were analysed by flow cytometry for the determination of TGF-β1 production. Immunohistochemical analyses were carried out for the examination of TGF-β1 expression in HD post mortem brain tissues. <h3>Results</h3> Our results indicated that the frequency of TGF-β1 expressing macrophages was significantly reduced in presymptomatic and I stage HD subjects compared to controls and increased with disease progression. Similar results were observed in HD brain tissues. <h3>Conclusion</h3> Here we demonstrated that macrophages showed variable TGF-β1 production profile during disease progression. These data correlated well with TGF-β1 immunoreactivity in HD brain tissues. Collectively we described an interesting link between production of TGF-β1 in the periphery and central defect and highlighted the potential of TGF-β1 as a possible novel marker for disease progression.

C01 TRACK-TGHD MINIPIG—introduction of a longitudinal tgHD minipig phenotyping study using MRI, motor and cognitive endpoints

<h3>Background</h3> In 2009 a tgHD Minipig was created, driven by a human huntintin promoter carrying a truncated human N-terminal part of htt (548aa) with 124 Q. This model was especially designed to fit the needs of future pre-clinical translational studies in Huntington9s disease. Meanwhile, it is known that the F0, F1 and F2 generations express uniform genetic characteristics (copy number of insert, localisation of transgene, length of polyQ stretch) and expression levels of mutant human htt. <h3>Aim</h3> Our aim is to assess the potential of this model for pre-clinical translational studies by investigating the development of a phenotype and identifying the most suitable and reliable endpoints for proof-of-concept studies. <h3>Methods and Techniques</h3> A battery of tests has been developed with five control animals (male, castrated). Based on the human UHDRS-TMS a “Large Animal UHDRS-TMS” was created. It explores a wide range of motor and cognitive functions. For example, physically and mentally challenging tasks performed in an obstacle course. Quantitative motor assessments will deliver objective measurements of motor dysfunction, for example, using automated gait analysis (GAITRite). A colour differentiation test is applied to assess cognition. Furthermore a protocol for MR Imaging has been developed and tested. <h3>Outcome</h3> Preliminary data of the GAITRite carpet has been collected in n=25 Libechov Minipigs (m-wt=5, m-tg=10, f-wt=5, f-tg=5) at a baseline and a 6 months follow-up assessment showing feasibility to perform the tests. In order to verify these results and further investigate feasibility the same group of animals will be assessed under the same conditions at future 6 months intervals. So far 16 MRI scans have been performed in 10 different animals. 5 wt Minipigs have been scanned once (age: 5, 6, 8, 12 and 25 months), 1 wt has been scanned twice (age: 12 and 24 m.), 1 wt has been scanned four times (age: 5, 18, 28 and 28 m.), 1 tg has been scanned once (age: 25 m.) and 2 tgs have been scanned twice (both age: 12 and 24 m.). All animals survived the procedure which lasted up to 4 h. VBM Volumetry, DTI/Fiber tracking and NMR Spectroscopy were applied. <h3>Conclusions</h3> Feasibility to repeatedly perform all assessments with the Libechov Minipig and to obtain reproducible data were shown. Future investigations of an increased number of Minipigs will be performed.

Assessing Polyglutamine Conformation in the Nucleating Event by Molecular Dynamics Simulations

Polyglutamine (polyQ) diseases comprise a group of dominantly inherited pathology caused by an expansion of an unstable polyQ stretch which is presumed to form β-sheets. Similar to other amyloid pathologies, polyQ amyloidogenesis occurs via a nucleated polymerization mechanism, and proceeds through energetically unfavorable nucleus whose existence and structure are difficult to detect. Here, we use atomistic molecular dynamics simulations in explicit solvent to assess the conformation of the polyQ stretch in the nucleus that initiates polyQ fibrillization. Comparison of the kinetic stability of various structures of polyQ peptide with a Q-length in the pathological range (Q40) revealed that steric zipper or nanotube-like structures (β-nanotube or β-pseudohelix) are not kinetically stable enough to serve as a template to initiate polyQ fibrillization as opposed to β-hairpin-based (β-sheet and β-sheetstack) or α-helical conformations. The selection of different structures of the polyQ stretch in the aggregation-initiating event may provide an alternative explanation for polyQ aggregate polymorphism.