Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph Disease, is a progressive neurodegenerative disorder characterized by loss of neuronal matter due to the expansion of the CAG repeat ...in the
gene and subsequent ataxin-3 protein. Although the underlying pathogenic protein expansion has been known for more than 20 years, the complexity of its effects is still under exploration. The ataxin-3 protein in its expanded form is known to aggregate and disrupt cellular processes in neuronal tissue but the role of the protein on populations of immune cells is unknown. Recently, mast cells have emerged as potential key players in neuroinflammation and neurodegeneration. Here, we examined the mast cell-related effects of ataxin-3 expansion in the brain tissues of 304Q ataxin-3 knock-in mice and SCA3 patients. We also established cultures of mast cells from the 304Q knock-in mice and examined the effects of 304Q ataxin-3 knock-in on the immune responses of these cells and on markers involved in mast cell growth, development and function. Specifically, our results point to a role for expanded ataxin-3 in suppression of mast cell marker CD117/c-Kit, pro-inflammatory cytokine TNF-α and NF-κB inhibitor IκBα along with an increased expression of the granulocyte-attracting chemokine CXCL1. These results are the beginning of a more holistic understanding of ataxin-3 and could point to the development of novel therapeutic targets which act on inflammation to mitigate symptoms of SCA3.
Dysfunctional mitochondria are linked to several neurodegenerative diseases. Metabolic defects, a symptom which can result from dysfunctional mitochondria, are also present in spinocerebellar ataxia ...type 3 (SCA3), also known as Machado-Joseph disease, the most frequent, dominantly inherited neurodegenerative ataxia worldwide. Mitochondrial dysfunction has been reported for several neurodegenerative disorders and ataxin-3 is known to deubiquitinylate parkin, a key protein required for canonical mitophagy. In this study, we analyzed mitochondrial function and mitophagy in a patient-derived SCA3 cell model. Human fibroblast lines isolated from SCA3 patients were immortalized and characterized. SCA3 patient fibroblasts revealed circular, ring-shaped mitochondria and featured reduced OXPHOS complexes, ATP production and cell viability. We show that wildtype ataxin-3 deubiquitinates VDAC1 (voltage-dependent anion channel 1), a member of the mitochondrial permeability transition pore and a parkin substrate. In SCA3 patients, VDAC1 deubiquitination and parkin recruitment to the depolarized mitochondria is inhibited. Increased p62-linked mitophagy, autophagosome formation and autophagy is observed under disease conditions, which is in line with mitochondrial fission. SCA3 fibroblast lines demonstrated a mitochondrial phenotype and dysregulation of parkin-VDAC1-mediated mitophagy, thereby promoting mitochondrial quality control via alternative pathways.
Crown rust, caused by
Puccinia coronata
f. sp.
avenae
(
Pca
), is a significant impediment to global oat production. Some 98 alleles at 92 loci conferring resistance to
Pca
in
Avena
have been ...designated; however, allelic relationships and chromosomal locations of many of these are unknown. Long-term monitoring of
Pca
in Australia, North America and elsewhere has shown that it is highly variable even in the absence of sexual recombination, likely due to large pathogen populations that cycle between wild oat communities and oat crops. Efforts to develop cultivars with genetic resistance to
Pca
began in the 1950s. Based almost solely on all all-stage resistance, this has had temporary benefits but very limited success. The inability to eradicate wild oats, and their common occurrence in many oat growing regions, means that future strategies to control
Pca
must be based on the assumption of a large and variable prevailing pathogen population with high evolutionary potential, even if cultivars with durable resistance are deployed and grown widely. The presence of minor gene, additive APR to
Pca
in hexaploid oat germplasm opens the possibility of pyramiding several such genes to give high levels of resistance. The recent availability of reference genomes for diploid and hexaploid oat will undoubtedly accelerate efforts to discover, characterise and develop high throughput diagnostic markers to introgress and pyramid resistance to
Pca
in high yielding adapted oat germplasm.
Bacterial global post-transcriptional regulators execute hundreds of interactions with targets that display varying molecular features while retaining specificity. Herein, we develop, validate, and ...apply a biophysical, statistical thermodynamic model of canonical target mRNA interactions with the CsrA global post-transcriptional regulator to understand the molecular features that contribute to target regulation. Altogether, we model interactions of CsrA with a pool of 236 mRNA: 107 are experimentally regulated by CsrA and 129 are suspected interaction partners. Guided by current understanding of CsrA-mRNA interactions, we incorporate (i) mRNA nucleotide sequence, (ii) cooperativity of CsrA-mRNA binding, and (iii) minimization of mRNA structural changes to identify an ensemble of likely binding sites and their free energies. The regulatory impact of bound CsrA on mRNA translation is determined with the RBS calculator. Predicted regulation of 66 experimentally regulated mRNAs adheres to the principles of canonical CsrA-mRNA interactions; the remainder implies that other, diverse mechanisms may underlie CsrA-mRNA interaction and regulation. Importantly, results suggest that this global regulator may bind targets in multiple conformations, via flexible stretches of overlapping predicted binding sites. This novel observation expands the notion that CsrA always binds to its targets at specific consensus sequences.
Spinocerebellar ataxia type 3 (SCA3) is a rare neurodegenerative disorder resulting from an aberrant expansion of a polyglutamine stretch in the ataxin-3 protein and subsequent neuronal death. The ...underlying intracellular signaling pathways are currently unknown. We applied the Reverse-phase Protein MicroArray (RPMA) technology to assess the levels of 50 signaling proteins (in phosphorylated and total forms) using three in vitro and in vivo models expressing expanded ataxin-3: (i) human embryonic kidney (HEK293T) cells stably transfected with human ataxin-3 constructs, (ii) mouse embryonic fibroblasts (MEF) from SCA3 transgenic mice, and (iii) whole brains from SCA3 transgenic mice. All three models demonstrated a high degree of similarity sharing a subset of phosphorylated proteins involved in the PI3K/AKT/GSK3/mTOR pathway. Expanded ataxin-3 strongly interfered (by stimulation or suppression) with normal ataxin-3 signaling consistent with the pathogenic role of the polyglutamine expansion. In comparison with normal ataxin-3, expanded ataxin-3 caused a pro-survival stimulation of the ERK pathway along with reduced pro-apoptotic and transcriptional responses.
Summary
Background & Aims
Spinocerebellar ataxia type 3 (SCA3), also known as Machado‐Joseph disease (MJD), is an autosomal dominantly inherited neurodegenerative disorder and the most common form of ...SCA worldwide. It is caused by the expansion of a polyglutamine (polyQ) tract in the ataxin‐3 protein. Nuclear localization of the affected protein is a key event in the pathology of SCA3 via affecting nuclear organization, transcriptional dysfunction, and seeding aggregations, finally causing neurodegeneration and cell death. So far, there is no effective therapy to prevent or slow the progression of SCA3.
Methods
In this study, we explored the effect of divalproex sodium as an HDACi in SCA3 cell models and explored how divalproex sodium interferes with pathogenetic processes causing SCA3.
Results
We found that divalproex sodium rescues the hypoacetylation levels of histone H3 and attenuates cellular cytotoxicity induced by expanded ataxin‐3 partly via preventing nuclear transport of ataxin‐3 (particularly heat shock‐dependent).
Conclusion
Our study provides novel insights into the mechanisms of action of divalproex sodium as a possible treatment for SCA3, beyond the known regulation of transcription.
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•Splat-cooled U–6at.% Mo, U–5at.% Pd, U–5at.% Pt alloys become superconducting below 1K.•U–5at.% Pd and U–5at.% Pt reveal only one resistivity jump at Tc.•Two distinguishable ...resistivity drops were observed for U–6at.% Mo.•A broad maximum was observed at Tc in the specific heat.•Those splats consist of two phases having orthorhombic α- and cubic γ-U structure.
U–T (T=Mo, Pd, Pt) alloys were prepared by splat cooling technique and characterized by X-ray diffraction. The resistivity and specific heat measurements were performed down to 0.3K to study their superconductivity. The superconducting transition in the alloy with 6at.% Mo (U–6%Mo) revealed by a smooth decrease below 1.5K and a sharp drop at 0.6K in the resistivity, while a single sharp drop was revealed at Tc≈0.8K for those with 5at.% Pd and Pt doping (U–5%Pd and U–5%Pt). With applying magnetic fields, the resistivity drops move to lower temperatures. The superconductivity transitions were revealed by only one broad peak at Tc in the C(T) curves.
U-Nb alloys with Nb concentration in the range of 0–20 at. % were prepared using a splat-cooling technique with a cooling rate of 106 K/s. Structure analysis by X-ray diffraction revealed a ...stabilization of the γ-U phase in alloys with ≥15 at. % Nb concentration. The investigated materials become superconducting below Tc = 1.90 K and the critical field μ0Hc2(0) can reach 5.4 T. The hydrogen absorption in U-15 at.% Nb (U0.85Nb0.15) at high hydrogen pressures exceeding 4 bar leads to a formation of the hydride (UH3)0.85Nb0.15. It is a ferromagnet with TC ≈ 195 K and a magnetic moment of 0.80 μB/U.
U-Ti and U-Ru alloys with various Ti, Ru concentrations were prepared using an ultrafast-cooling technique (splat cooling). A phase analysis by X-ray diffraction revealed the presence of the bcc γ-U ...phase developing with increasing concentration of alloying elements, while the concentration of orthorhombic α-U structure decreases. The tetragonally distorted γ° phase, (existing for 8–10at. % Ru) is followed by pure cubic γ-U phase (for 12, 15% Ru). For Ti, more than 20at. % is needed to yield pure γ-U phase. The occurrence of superconductivity was investigated by resistivity and specific heat measurements down to 0.4K in various magnetic fields. All U-T splats studied become superconducting with Tc not exceeding 2.0K.
The γ-U phase alloys can be retained down to low temperatures with less required alloying concentration by using the splat-cooling technique with a cooling rate better than 10^6 K/s. Doping with 15 ...at.% Mo, Pt, Pd, Nb leads to a stabilization of the cubic γ-U phase, while it requires much higher Zr concentrations （≥30 at.% Zr）. All U-T splats become superconducting with Tc in the range of 0.61-2.11 K. A good agreement of the experimentally observed specific-heat jump at Tc with that from BCS theory prediction was obtained for U-15 at.% Mo consisting of the γ-U phase with an ideal bcc A2 structure.
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