Spinocerebellar Ataxia Type 1 protein Ataxin-1 is signaled to DNA damage by ataxia-telangiectasia mutated kinase.

Spinocerebellar Ataxia Type 1 (SCA1) is an autosomal dominant neurodegenerative disorder caused by a polyglutamine expansion in the ataxin-1 protein. Recent genetic correlational studies have implicated DNA damage repair pathways in modifying the age at onset of disease symptoms in SCA1 and Huntington's Disease, another polyglutamine expansion disease. We demonstrate that both endogenous and transfected ataxin-1 localizes to sites of DNA damage, which is impaired by polyglutamine expansion. This response is dependent on ataxia-telangiectasia mutated (ATM) kinase activity. Further, we characterize an ATM phosphorylation motif within ataxin-1 at serine 188. We show reduction of the Drosophila ATM homolog levels in a ATXN1[82Q] Drosophila model through shRNA or genetic cross ameliorates motor symptoms. These findings offer a possible explanation as to why DNA repair was implicated in SCA1 pathogenesis by past studies. The similarities between the ataxin-1 and the huntingtin responses to DNA damage provide further support for a shared pathogenic mechanism for polyglutamine expansion diseases.

Shedding a new light on Huntington's disease: how blood can both propagate and ameliorate disease pathology.

Huntington's disease (HD) is a monogenic neurodegenerative disorder resulting from a mutation in the huntingtin gene. This leads to the expression of the mutant huntingtin protein (mHTT) which provokes pathological changes in both the central nervous system (CNS) and periphery. Accumulating evidence suggests that mHTT can spread between cells of the CNS but here, we explored the possibility that mHTT could also propagate and cause pathology via the bloodstream. For this, we used a parabiosis approach to join the circulatory systems of wild-type (WT) and zQ175 mice. After surgery, we observed mHTT in the plasma and circulating blood cells of WT mice and post-mortem analyses revealed the presence of mHTT aggregates in several organs including the liver, kidney, muscle and brain. The presence of mHTT in the brain was accompanied by vascular abnormalities, such as a reduction of Collagen IV signal intensity and altered vessel diameter in the striatum, and changes in expression of Glutamic acid decarboxylase 65/67 (GAD65-67) in the cortex. Conversely, we measured reduced pathology in zQ175 mice by decreased mitochondrial impairments in peripheral organs, restored vessel diameter in the cortex and improved expression of Dopamine- and cAMP-regulated phosphoprotein 32 (DARPP32) in striatal neurons. Collectively, these results demonstrate that circulating mHTT can disseminate disease, but importantly, that healthy blood can dilute pathology. These findings have significant implications for the development of therapies in HD.

N6-Furfuryladenine is protective in Huntington's disease models by signaling huntingtin phosphorylation.

The huntingtin N17 domain is a modulator of mutant huntingtin toxicity and is hypophosphorylated in Huntington's disease (HD). We conducted high-content analysis to find compounds that could restore N17 phosphorylation. One lead compound from this screen was N6-furfuryladenine (N6FFA). N6FFA was protective in HD model neurons, and N6FFA treatment of an HD mouse model corrects HD phenotypes and eliminates cortical mutant huntingtin inclusions. We show that N6FFA restores N17 phosphorylation levels by being salvaged to a triphosphate form by adenine phosphoribosyltransferase (APRT) and used as a phosphate donor by casein kinase 2 (CK2). N6FFA is a naturally occurring product of oxidative DNA damage. Phosphorylated huntingtin functionally redistributes and colocalizes with CK2, APRT, and N6FFA DNA adducts at sites of induced DNA damage. We present a model in which this natural product compound is salvaged to provide a triphosphate substrate to signal huntingtin phosphorylation via CK2 during low-ATP stress under conditions of DNA damage, with protective effects in HD model systems.

High-mobility group box 1 links sensing of reactive oxygen species by huntingtin to its nuclear entry.

Huntington's disease (HD) is a neurodegenerative, age-onset disorder caused by a CAG DNA expansion in exon 1 of the HTT gene, resulting in a polyglutamine expansion in the huntingtin protein. Nuclear accumulation of mutant huntingtin is a hallmark of HD, resulting in elevated mutant huntingtin levels in cell nuclei. Huntingtin is normally retained at the endoplasmic reticulum via its N17 amphipathic α-helix domain but is released by oxidation of Met-8 during reactive oxygen species (ROS) stress. Huntingtin enters the nucleus via an importin ß1- and 2-dependent proline-tyrosine nuclear localization signal (PY-NLS), which has a unique intervening sequence in huntingtin. Here, we have identified the high-mobility group box 1 (HMGB1) protein as an interactor of the intervening sequence within the PY-NLS. Nuclear levels of HMGB1 positively correlated with varying levels of nuclear huntingtin in both HD and normal human fibroblasts. We also found that HMGB1 interacts with the huntingtin N17 region and that this interaction is enhanced by the presence of ROS and phosphorylation of critical serine residues in the N17 region. We conclude that HMGB1 is a huntingtin N17/PY-NLS ROS-dependent interactor, and this protein bridging is essential for relaying ROS sensing by huntingtin to its nuclear entry during ROS stress. ROS may therefore be a critical age-onset stress that triggers nuclear accumulation of mutant huntington in Huntington's disease.

Huntingtin is a scaffolding protein in the ATM oxidative DNA damage response complex.

Huntington's disease (HD) is an age-dependent neurodegenerative disease. DNA repair pathways have recently been implicated as the most predominant modifiers of age of onset in HD patients. We report that endogenous huntingtin protein directly participates in oxidative DNA damage repair. Using novel chromobodies to detect endogenous human huntingtin in live cells, we show that localization of huntingtin to DNA damage sites is dependent on the kinase activity of ataxia telangiectasia mutated (ATM) protein. Super-resolution microscopy and biochemical assays revealed that huntingtin co-localizes with and scaffolds proteins of the DNA damage response pathway in response to oxidative stress. In HD patient fibroblasts bearing typical clinical HD allele lengths, we demonstrate that there is deficient oxidative DNA damage repair. We propose that DNA damage in HD is caused by dysfunction of the mutant huntingtin protein in DNA repair, and accumulation of DNA oxidative lesions due to elevated reactive oxygen species may contribute to the onset of HD.

Atraumatic versus conventional lumbar puncture needles: a systematic review and meta-analysis.

BACKGROUND: Atraumatic needles have been proposed to lower complication rates after lumbar puncture. However, several surveys indicate that clinical adoption of these needles remains poor. We did a systematic review and meta-analysis to compare patient outcomes after lumbar puncture with atraumatic needles and conventional needles. METHODS: In this systematic review and meta-analysis, we independently searched 13 databases with no language restrictions from inception to Aug 15, 2017, for randomised controlled trials comparing the use of atraumatic needles and conventional needles for any lumbar puncture indication. Randomised trials comparing atraumatic and conventional needles in which no dural puncture was done (epidural injections) or without a conventional needle control group were excluded. We screened studies and extracted data from published reports independently. The primary outcome of postdural-puncture headache incidence and additional safety and efficacy outcomes were assessed by random-effects and fixed-effects meta-analysis. This study is registered with the International Prospective Register of Systematic Reviews, number CRD42016047546. FINDINGS: We identified 20 241 reports; after exclusions, 110 trials done between 1989 and 2017 from 29 countries, including a total of 31 412 participants, were eligible for analysis. The incidence of postdural-puncture headache was significantly reduced from 11·0% (95% CI 9·1-13·3) in the conventional needle group to 4·2% (3·3-5·2) in the atraumatic group (relative risk 0·40, 95% CI 0·34-0·47, p<0·0001; I2=45·4%). Atraumatic needles were also associated with significant reductions in the need for intravenous fluid or controlled analgesia (0·44, 95% CI 0·29-0·64; p<0·0001), need for epidural blood patch (0·50, 0·33-0·75; p=0·001), any headache (0·50, 0·43-0·57; p<0·0001), mild headache (0·52, 0·38-0·70; p<0·0001), severe headache (0·41, 0·28-0·59; p<0·0001), nerve root irritation (0·71, 0·54-0·92; p=0·011), and hearing disturbance (0·25, 0·11-0·60; p=0·002). Success of lumbar puncture on first attempt, failure rate, mean number of attempts, and the incidence of traumatic tap and backache did not differ significantly between the two needle groups. Prespecified subgroup analyses of postdural-puncture headache revealed no interactions between needle type and patient age, sex, use of prophylactic intravenous fluid, needle gauge, patient position, indication for lumbar puncture, bed rest after puncture, or clinician specialty. These results were rated high-quality evidence as examined using the grading of recommendations assessment, development, and evaluation. INTERPRETATION: Among patients who had lumbar puncture, atraumatic needles were associated with a decrease in the incidence of postdural-puncture headache and in the need for patients to return to hospital for additional therapy, and had similar efficacy to conventional needles. These findings offer clinicians and stakeholders a comprehensive assessment and high-quality evidence for the safety and efficacy of atraumatic needles as a superior option for patients who require lumbar puncture. FUNDING: None.

Huntingtin N17 domain is a reactive oxygen species sensor regulating huntingtin phosphorylation and localization.

The N17 domain of the huntingtin protein is post-translationally modified and is the master regulator of huntingtin intracellular localization. In Huntington's disease (HD), mutant huntingtin is hypo-phosphorylated at serines 13 and 16 within N17, and increasing N17 phosphorylation has been shown to be protective in HD mouse models. Thus, N17 phosphorylation is defined as a sub-target of huntingtin for potential therapeutic intervention. We have previously shown that cellular stress can affect huntingtin nuclear entry and phosphorylation. Here, we demonstrate that huntingtin localization can be specifically affected by reactive oxygen species (ROS) stress. We have located the sensor of this stress to the N17 domain, specifically to a highly conserved methionine at position 8. In vitro, we show by circular dichroism spectroscopy structural studies that the alpha-helical structure of N17 changes in response to redox conditions and show that the consequence of this change is enhanced N17 phosphorylation and nuclear targeting of endogenous huntingtin. Using N17 substitution point mutants, we demonstrate that N17 sulphoxidation enhances N17 dissociation from the endoplasmic reticulum (ER) membrane. This enhanced solubility makes N17 a better substrate for phosphorylation and subsequent nuclear retention. This ability of huntingtin to sense ROS levels at the ER, with phosphorylation and nuclear localization as a response, suggests that ROS stress due to aging could be a critical molecular trigger of huntingtin functions and dysfunctions in HD and may explain the age-onset nature of the disorder.

A huntingtin-mediated fast stress response halting endosomal trafficking is defective in Huntington's disease.

Cellular stress is a normal part of the aging process and is especially relevant in neurodegenerative disease. Canonical stress responses, such as the heat shock response, activate following exposure to stress and restore proteostasis through the action of isomerases and chaperones within the cytosol. Through live-cell imaging, we demonstrate involvement of the Huntington's disease (HD) protein, huntingtin, in a rapid cell stress response that lies temporally upstream of canonical stress responses. This response is characterized by the formation of distinct cytosolic puncta and reversible localization of huntingtin to early endosomes. The formation of these puncta, which we have termed huntingtin stress bodies (HSBs), is associated with arrest of early-to-recycling and early-to-late endosomal trafficking. The critical domains for this response have been mapped to two regions of huntingtin flanking the polyglutamine tract, and we observe polyglutamine-expanded huntingtin-expressing cells to be defective in their ability to recover from this stress response. We propose that HSB formation rapidly diverts high ATP use from vesicular trafficking during stress, thus mobilizing canonical stress responses without relying on increased energy metabolism, and that restoration from this response is defective in HD.

Live cell imaging and biophotonic methods reveal two types of mutant huntingtin inclusions.

Huntington's disease (HD) is an autosomal dominant, neurodegenerative disorder that can be characterized by the presence of protein inclusions containing mutant huntingtin within a subset of neurons in the brain. Since their discovery, the relevance of inclusions to disease pathology has been controversial. We show using super-resolution fluorescence imaging and Förster resonance energy transfer (FRET) in live cells, that mutant huntingtin fragments can form two morphologically and conformationally distinct inclusion types. Using fluorescence recovery after photobleaching (FRAP), we demonstrate that the two huntingtin inclusion types have unique dynamic properties. The ability to form one or the other type of inclusion can be influenced by the phosphorylation state of serine residues at amino acid positions 13 and 16 within the huntingtin protein. We can define two types of inclusions: fibrillar, which are tightly packed, do not exchange protein with the soluble phase, and result from phospho-modification at serines 13 and 16 of the N17 domain, and globular, which are loosely packed, can readily exchange with the soluble phase, and are not phosphorylated in N17. We hypothesize that the protective effect of N17 phosphorylation or phospho-mimicry seen in animal models, at the level of protein inclusions with elevated huntingtin levels, is to induce a conformation of the huntingtin amino-terminus that causes fragments to form tightly packed inclusions that do not exit the insoluble phase, and hence exert less toxicity. The identification of these sub-types of huntingtin inclusions could allow for drug discovery to promote protective inclusions of mutant huntingtin protein in HD.

Polyglutamine domain flexibility mediates the proximity between flanking sequences in huntingtin.

Huntington disease (HD) is a neurodegenerative disorder caused by a CAG expansion within the huntingtin gene that encodes a polymorphic glutamine tract at the amino terminus of the huntingtin protein. HD is one of nine polyglutamine expansion diseases. The clinical threshold of polyglutamine expansion for HD is near 37 repeats, but the mechanism of this pathogenic length is poorly understood. Using Förster resonance energy transfer, we describe an intramolecular proximity between the N17 domain and the downstream polyproline region that flanks the polyglutamine tract of huntingtin. Our data support the hypothesis that the polyglutamine tract can act as a flexible domain, allowing the flanking domains to come into close spatial proximity. This flexibility is impaired with expanded polyglutamine tracts, and we can detect changes in huntingtin conformation at the pathogenic threshold for HD. Altering the structure of N17, either via phosphomimicry or with small molecules, also affects the proximity between the flanking domains. The structural capacity of N17 to fold back toward distal regions within huntingtin requires an interacting protein, protein kinase C and casein kinase 2 substrate in neurons 1 (PACSIN1). This protein has the ability to bind both N17 and the polyproline region, stabilizing the interaction between these two domains. We also developed an antibody-based FRET assay that can detect conformational changes within endogenous huntingtin in wild-type versus HD fibroblasts. Therefore, we hypothesize that wild-type length polyglutamine tracts within huntingtin can form a flexible domain that is essential for proper functional intramolecular proximity, conformations, and dynamics.

Ganglioside GM1 induces phosphorylation of mutant huntingtin and restores normal motor behavior in Huntington disease mice.

Huntington disease (HD) is a progressive neurodegenerative monogenic disorder caused by expansion of a polyglutamine stretch in the huntingtin (Htt) protein. Mutant huntingtin triggers neural dysfunction and death, mainly in the corpus striatum and cerebral cortex, resulting in pathognomonic motor symptoms, as well as cognitive and psychiatric decline. Currently, there is no effective treatment for HD. We report that intraventricular infusion of ganglioside GM1 induces phosphorylation of mutant huntingtin at specific serine amino acid residues that attenuate huntingtin toxicity, and restores normal motor function in already symptomatic HD mice. Thus, our studies have identified a potential therapy for HD that targets a posttranslational modification of mutant huntingtin with critical effects on disease pathogenesis.

Cofilin nuclear-cytoplasmic shuttling affects cofilin-actin rod formation during stress.

Cofilin protein is involved in regulating the actin cytoskeleton during typical steady state conditions, as well as during cell stress conditions where cofilin saturates F-actin, forming cofilin-actin rods. Cofilin can enter the nucleus through an active nuclear localization signal (NLS), accumulating in nuclear actin rods during stress. Here, we characterize the active nuclear export of cofilin through a leptomycin-B-sensitive, CRM1-dependent, nuclear export signal (NES). We also redefine the NLS of cofilin as a bipartite NLS, with an additional basic epitope required for nuclear localization. Using fluorescence lifetime imaging microscopy (FLIM) and Förster resonant energy transfer (FRET) between cofilin moieties and actin, as well as automated image analysis in live cells, we have defined subtle mutations in the cofilin NLS that allow cofilin to bind actin in vivo and affect cofilin dynamics during stress. We further define the requirement of cofilin-actin rod formation in a system of cell stress by temporal live-cell imaging. We propose that cofilin nuclear shuttling is critical for the cofilin-actin rod stress response with cofilin dynamically communicating between the nucleus and cytoplasm during cell stress.

Identification of a karyopherin ß1/ß2 proline-tyrosine nuclear localization signal in huntingtin protein.

Among the known pathways of protein nuclear import, the karyopherin ß2/transportin pathway is only the second to have a defined nuclear localization signal (NLS) consensus. Huntingtin, a 350-kDa protein, has defined roles in the nucleus, as well as a CRM1/exportin-dependent nuclear export signal; however, the NLS and exact pathway of import have remained elusive. Here, using a live cell assay and affinity chromatography, we show that huntingtin has a karyopherin ß2-dependent proline-tyrosine (PY)-NLS in the amino terminus of the protein. This NLS comprises three consensus components: a basic charged sequence, a downstream conserved arginine, and a PY sequence. Unlike the classic PY-NLS, which has an unstructured intervening sequence between the consensus components, we show that a ß sheet structured region separating the consensus elements is critical for huntingtin NLS function. The huntingtin PY-NLS is also capable of import through the importin/karyopherin ß1 pathway but was not functional in all cell types tested. We propose that this huntingtin PY-NLS may comprise a new class of multiple import factor-dependent NLSs with an internal structural component that may regulate NLS activity.

Mutant huntingtin causes defective actin remodeling during stress: defining a new role for transglutaminase 2 in neurodegenerative disease.

Huntington's disease (HD) is caused by an expanded CAG tract in the Interesting transcript 15 (IT15) gene encoding the 350 kDa huntingtin protein. Cellular stresses can trigger the release of huntingtin from the endoplasmic reticulum, allowing huntingtin nuclear entry. Here, we show that endogenous, full-length huntingtin localizes to nuclear cofilin-actin rods during stress and is required for the proper stress response involving actin remodeling. Mutant huntingtin induces a dominant, persistent nuclear rod phenotype similar to that described in Alzheimer's disease for cytoplasmic cofilin-actin rods. Using live cell temporal studies, we show that this stress response is similarly impaired when mutant huntingtin is present, or when normal huntingtin levels are reduced. In clinical lymphocyte samples from HD patients, we have quantitatively detected cross-linked complexes of actin and cofilin with complex formation varying in correlation with disease progression. By live cell fluorescence lifetime imaging measurement-Förster resonant energy transfer studies and western blot assays, we quantitatively observed that stress-activated tissue transglutaminase 2 (TG2) is responsible for the actin-cofilin covalent cross-linking observed in HD. These data support a direct role for huntingtin in nuclear actin re-organization, and describe a new pathogenic mechanism for aberrant TG2 enzymatic hyperactivity in neurodegenerative diseases.

Kinase inhibitors modulate huntingtin cell localization and toxicity.

Two serine residues within the first 17 amino acid residues of huntingtin (N17) are crucial for modulation of mutant huntingtin toxicity in cell and mouse genetic models of Huntington's disease. Here we show that the stress-dependent phosphorylation of huntingtin at Ser13 and Ser16 affects N17 conformation and targets full-length huntingtin to chromatin-dependent subregions of the nucleus, the mitotic spindle and cleavage furrow during cell division. Polyglutamine-expanded mutant huntingtin is hypophosphorylated in N17 in both homozygous and heterozygous cell contexts. By high-content screening in live cells, we identified kinase inhibitors that modulated N17 phosphorylation and hence huntingtin subcellular localization. N17 phosphorylation was reduced by casein kinase-2 inhibitors. Paradoxically, IKKß kinase inhibition increased N17 phosphorylation, affecting huntingtin nuclear and subnuclear localization. These data indicate that huntingtin phosphorylation at Ser13 and Ser16 can be modulated by small-molecule drugs, which may have therapeutic potential in Huntington's disease.

PAM-Flexible Genome Editing with an Engineered Chimeric Cas9.

CRISPR enzymes require a defined protospacer adjacent motif (PAM) flanking a guide RNA-programmed target site, limiting their sequence accessibility for robust genome editing applications. In this study, we recombine the PAM-interacting domain of SpRY, a broad-targeting Cas9 possessing an NRN > NYN PAM preference, with the N-terminus of Sc++, a Cas9 with simultaneously broad, efficient, and accurate NNG editing capabilities, to generate a chimeric enzyme with highly flexible PAM preference: SpRYc. We demonstrate that SpRYc leverages properties of both enzymes to specifically edit diverse NNN PAMs and disease-related loci for potential therapeutic applications. In total, the unique approaches to generate SpRYc, coupled with its robust flexibility, highlight the power of integrative protein design for Cas9 engineering and motivate downstream editing applications that require precise genomic positioning.

PAM-flexible genome editing with an engineered chimeric Cas9.

CRISPR enzymes require a defined protospacer adjacent motif (PAM) flanking a guide RNA-programmed target site, limiting their sequence accessibility for robust genome editing applications. In this study, we recombine the PAM-interacting domain of SpRY, a broad-targeting Cas9 possessing an NRN > NYN (R = A or G, Y = C or T) PAM preference, with the N-terminus of Sc + +, a Cas9 with simultaneously broad, efficient, and accurate NNG editing capabilities, to generate a chimeric enzyme with highly flexible PAM preference: SpRYc. We demonstrate that SpRYc leverages properties of both enzymes to specifically edit diverse PAMs and disease-related loci for potential therapeutic applications. In total, the approaches to generate SpRYc, coupled with its robust flexibility, highlight the power of integrative protein design for Cas9 engineering and motivate downstream editing applications that require precise genomic positioning.

The impact of the COVID-19 pandemic on perceived publication pressure among academic researchers in Canada.

The phenomenon of "publish-or-perish" in academia, spurred on by limited funding and academic positions, has led to increased competition and pressure on academics to publish. Publication pressure has been linked with multiple negative outcomes, including increased academic misconduct and researcher burnout. COVID-19 has disrupted research worldwide, leading to lost research time and increased anxiety amongst researchers. The objective of this study was to examine how COVID-19 has impacted perceived publication pressure amongst academic researchers in Canada. We used the revised Publication Pressure Questionnaire, in addition to Likert-type questions to discern respondents' beliefs and concerns about the impact of COVID-19 on academic publishing. We found that publication pressure increased across academic researchers in Canada following the pandemic, with respondents reporting increased stress, increased pessimism, and decreased access to support related to publishing. Doctoral students reported the highest levels of stress and pessimism, while principal investigators had the most access to publication support. There were no significant differences in publication pressure reported between different research disciplines. Women and non-binary or genderfluid respondents reported higher stress and pessimism than men. We also identified differences in perceived publication pressure based on respondents' publication frequency and other demographic factors, including disability and citizenship status. Overall, we document a snapshot of perceived publication pressure in Canada across researchers of different academic career stages and disciplines. This information can be used to guide the creation of researcher supports, as well as identify groups of researchers who may benefit from targeted resources.