Design of Modified Polymer Membranes Using Machine Learning.

Surface modification is an attractive strategy to adjust the properties of polymer membranes. Unfortunately, predictive structure-processing-property relationships between the modification strategies and membrane performance are often unknown. One possibility to tackle this challenge is the application of data-driven methods such as machine learning. In this study, we applied machine learning methods to data sets containing the performance parameters of modified membranes. The resulting machine learning models were used to predict performance parameters, such as the pure water permeability and the zeta potential of membranes modified with new substances. The predictions had low prediction errors, which allowed us to generalize them to similar membrane modifications and processing conditions. Additionally, machine learning methods were able to identify the impact of substance properties and process parameters on the resulting membrane properties. Our results demonstrate that small data sets, as they are common in materials science, can be used as training data for predictive machine learning models. Therefore, machine learning shows great potential as a tool to expedite the development of high-performance membranes while reducing the time and costs associated with the development process at the same time.

Immobilization of Bi2WO6 on Polymer Membranes for Photocatalytic Removal of Micropollutants from Water - A Stable and Visible Light Active Alternative.

In this work, bismuth tungstate Bi2WO6 is immobilized on polymer membranes to photocatalytically remove micropollutants from water as an alternative to titanium dioxide TiO2. A synthesis method for Bi2WO6 preparation and its immobilization on a polymer membrane is developed. Bi2WO6 is characterized using X-ray diffraction and UV-vis reflectance spectroscopy, while the membrane undergoes analysis through scanning electron microscopy, X-ray photoelectron spectroscopy, and degradation experiments. The density of states calculations for TiO2 and Bi2WO6, along with PVDF reactions with potential reactive species, are investigated by density functional theory. The generation of hydroxyl radicals OH• is investigated via the reaction of coumarin to umbelliferone via fluorescence probe detection and electron paramagnetic resonance. Increasing reactant concentration enhances Bi2WO6 crystallinity. Under UV light at pH 7 and 11, the Bi2WO6 membrane completely degrades propranolol in 3 and 1 h, respectively, remaining stable and reusable for over 10 cycles (30 h). Active under visible light with a bandgap of 2.91 eV, the Bi2WO6 membrane demonstrates superior stability compared to a TiO2 membrane during a 7-day exposure to UV light as Bi2WO6 does not generate OH• radicals. The Bi2WO6 membrane is an alternative for water pollutant degradation due to its visible light activity and long-term stability.

Poly(vinylidene fluoride) membrane with immobilized TiO2 for degradation of steroid hormone micropollutants in a photocatalytic membrane reactor.

The lack of effective technologies to remove steroid hormones (SHs) from aquatic systems is a critical issue for both environment and public health. The performance of a flow-through photocatalytic membrane reactor (PMR) with TiO2 immobilized on a photostable poly(vinylidene fluoride) membrane (PVDF-TiO2) was evaluated in the context of SHs degradation at concentrations from 0.05 to 1000 µg/L under UV exposure (365 nm). A comprehensive investigation into the membrane preparation approach, including varying the surface Ti content and distribution, and membrane pore size, was conducted to gain insights on the rate-limiting steps for the SHs degradation. Increasing surface Ti content from 4 % to 6.5 % enhanced the 17ß-estradiol (E2) degradation from 46 ± 12-81 ± 6 %. Apparent degradation kinetics were independent of both TiO2 homogeneity and membrane pore size (0.1-0.45 µm). With optimized conditions, E2 removal was higher than 96 % at environmentally relevant feed concentration (100 ng/L), a flux of 60 L/m2h, 25 mW/cm2, and 6.5 % Ti. These results indicated that the E2 degradation on the PVDF-TiO2 membrane was limited by the catalyst content and light penetration depth. Further exploration of novel TiO2 immobilization approach that can offer a larger catalyst content and light penetration is required to improve the micropollutant removal efficiency in PMR.

Photocatalytic degradation of steroid hormone micropollutants by TiO2-coated polyethersulfone membranes in a continuous flow-through process.

Micropollutants in the aquatic environment pose a high risk to both environmental and human health. The photocatalytic degradation of steroid hormones in a flow-through photocatalytic membrane reactor under UV light (365 nm) at environmentally relevant concentrations (50 ng l-1 to 1 mg l-1) was examined using a polyethersulfone-titanium dioxide (PES-TiO2) membrane. The TiO2 nanoparticles (10-30 nm) were immobilized both on the surface and in the nanopores (220 nm) of the membrane. Water quality and operational parameters were evaluated to elucidate the limiting factors in the degradation of steroid hormones. Flow through the photocatalytic membrane increased contact between the micropollutants and ·OH in the pores. Notably, 80% of both oestradiol and oestrone was removed from a 200 ng l-1 feed (at 25 mW cm-2 and 300 l m-2 h-1). Progesterone and testosterone removal was lower at 44% and 33%, respectively. Increasing the oestradiol concentration to 1 mg l-1 resulted in 20% removal, whereas with a 100 ng l-1 solution, a maximum removal of 94% was achieved at 44 mW cm-2 and 60 l m-2 h-1. The effectiveness of the relatively well-known PES-TiO2 membrane for micropollutant removal has been demonstrated; this effectiveness is due to the nanoscale size of the membrane, which provides a high surface area and facilitates close contact of the radicals with the very small (0.8 nm) micropollutant at an extremely low, environmentally relevant concentration (100 ng l-1).

Photosensitivity and cGAS-Dependent IFN-1 Activation in Patients with Lupus and TREX1 Deficiency.

The exonuclease TREX1 safeguards the cells against DNA accumulation in the cytosol and thereby prevents innate immune activation and autoimmunity. TREX1 mutations lead to chronic DNA damage and cell-intrinsic IFN-1 response. Associated disease phenotypes include Aicardi‒Goutières syndrome, familial chilblain lupus, and systemic lupus erythematosus. Given the role of UV light in lupus pathogenesis, we assessed sensitivity to UV light in patients with lupus and TREX1 mutation by phototesting, which revealed enhanced photosensitivity. TREX1-deficient fibroblasts and keratinocytes generated increased levels of ROS in response to UV irradiation as well as increased levels of 8-oxo-guanine lesions after oxidative stress. Likewise, the primary UV-induced DNA lesions cyclobutane pyrimidine dimers were induced more strongly in TREX1-deficient cells. Further analysis revealed that single-stranded DNA regions, frequently formed during DNA replication and repair, promote cyclobutane pyrimidine dimer formation. Together, this resulted in a strong UV-induced DNA damage response that was associated with a cGAS-dependent IFN-1 activation. In conclusion, these findings link chronic DNA damage to photosensitivity and IFN-1 production in TREX1 deficiency and explain the induction of disease flares on UV exposure in patients with lupus and TREX1 mutation.

Enhanced Removal and Toxicity Declineof Diclofenac by Combining UVA Treatmentand Adsorption of Photoproductsto Polyvinylidene Difluoride.

The occurrence of micropollutants in the environment is an emerging issue. Diclofenac, a non-steroidal anti-inflammatory drug, is one of the most frequently detected pharmaceuticals in the environment worldwide. Diclofenac is transformed by UVA light into different products with higher toxicity. The absorbance of the transformation products overlaps with the absorbance of diclofenac itself and inhibits the ongoing photoreaction. By adding polyvinylidene difluoride (PVDF), the products adsorb to the surface of PVDF. Therefore, phototransformation of diclofenac and total organic carbon (TOC) removal is enhanced and the toxicity decreased. At 15 min and 18 h of UVA treatment, removal of diclofenac and TOC increases from 56% to 65% and 18% to 54%, respectively, when PVDF is present. The toxicity of a UVA treated (18 h) diclofenac solution doubles (from 5 to 10, expressed in toxicity units, TU), while no toxicity was detectable when PVDF is present during UVA treatment (TU = 0). PVDF does not need to be irradiated itself but must be present during photoreaction. The adsorbent can be reused by washing with water or ethanol. Diclofenac (25 mg L-1) UVA light irradiation was monitored with high performance liquid chromatography (HPLC), UV-Vis spectroscopy and by analysing the decrease of TOC. The toxicity towards Vibrio fischeri was examined according to DIN EN ISO 11348-1: 2009-05. Density functional theory (DFT) was used to simulate the phototransformation products known in literature as well as further products identified via gas chromatography-mass spectrometry (GC-MS). The absorption spectra, reaction enthalpies (ΔH) and Gibbs free energy of reactions (ΔG) were calculated. The combination of UVA irradiation of diclofenac with adsorption of photoproducts to PVDF is unique and opens up new possibilities to enhance removal of pollutants from water.

Bio-Inspired Polymer Membrane Surface Cleaning.

To generate polyethersulfone membranes with a biocatalytically active surface, pancreatin was covalently immobilized. Pancreatin is a mixture of digestive enzymes such as protease, lipase, and amylase. The resulting membranes exhibit self-cleaning properties after "switching on" the respective enzyme by adjusting pH and temperature. Thus, the membrane surface can actively degrade a fouling layer on its surface and regain initial permeability. Fouling tests with solutions of protein, oil, and mixtures of both, were performed, and the membrane's ability to self-clean the fouled surface was characterized. Membrane characterization was conducted by investigation of the immobilized enzyme concentration, enzyme activity, water permeation flux, fouling tests, porosimetry, X-ray photoelectron spectroscopy, and scanning electron microscopy.

In Vivo Evaluation of 11C-DASB for Quantitative SERT Imaging in Rats and Mice.

UNLABELLED: Serotonin, or 5-hydroxytryptamine (5-HT), plays a key role in the central nervous system and is involved in many essential neurologic processes such as mood, social behavior, and sleep. The serotonin transporter ligand (11)C-3-amino-4(2-dimethylaminomethyl-phenylsufanyl)-benzonitrile ((11)C-DASB) has been used to determine nondisplaceable binding potential (BPND), which is defined as the quotient of the available receptor density (Bavail) and the apparent equilibrium dissociation rate constant (1/appKD) under in vivo conditions. Because of the increasing number of animal models of human diseases, there is a pressing need to evaluate the applicability of (11)C-DASB to rats and mice. Here, we assessed the feasibility of using (11)C-DASB for quantification of serotonin transporter (SERT) density and affinity in vivo in rats and mice. METHODS: Rats and mice underwent 4 PET scans with increasing doses of the unlabeled ligand to calculate Bavail and appKD using the multiple-ligand concentration transporter assay. An additional PET scan was performed to calculate test-retest reproducibility and reliability. BPND was calculated using the simplified reference tissue model, and the results for different reference regions were compared. RESULTS: Displaceable binding of (11)C-DASB was found in all brain regions of both rats and mice, with the highest binding being in the thalamus and the lowest in the cerebellum. In rats, displaceable binding was largely reduced in the cerebellar cortex, which in mice was spatially indistinguishable from cerebellar white matter. Use of the cerebellum with fully saturated binding sites as the reference region did not lead to reliable results. Test-retest reproducibility in the thalamus was more than 90% in both mice and rats. In rats, Bavail, appKD, and ED50 were 3.9 ± 0.4 pmol/mL, 2.2 ± 0.4 nM, and 12.0 ± 2.6 nmol/kg, respectively, whereas analysis of the mouse measurements resulted in inaccurate fits due to the high injected tracer mass. CONCLUSION: Our data showed that in rats, (11)C-DASB can be used to quantify SERT density with good reproducibility. BPND agreed with the distribution of SERT in the rat brain. It remains difficult to estimate quantitative parameters accurately from mouse measurements because of the high injected tracer mass and underestimation of the binding parameters due to high displaceable binding in the reference region.

A data driven method for estimation of B(avail) and appK(D) using a single injection protocol with [¹¹C]raclopride in the mouse.

PURPOSE: The partial saturation approach (PSA) is a simple, single injection experimental protocol that will estimate both B(avail) and appK(D) without the use of blood sampling. This makes it ideal for use in longitudinal studies of neurodegenerative diseases in the rodent. The aim of this study was to increase the range and applicability of the PSA by developing a data driven strategy for determining reliable regional estimates of receptor density (B(avail)) and in vivo affinity (1/appK(D)), and validate the strategy using a simulation model. METHODS: The data driven method uses a time window guided by the dynamic equilibrium state of the system as opposed to using a static time window. To test the method, simulations of partial saturation experiments were generated and validated against experimental data. The experimental conditions simulated included a range of receptor occupancy levels and three different B(avail) and appK(D) values to mimic diseases states. Also the effect of using a reference region and typical PET noise on the stability and accuracy of the estimates was investigated. RESULTS: The investigations showed that the parameter estimates in a simulated healthy mouse, using the data driven method were within 10±30% of the simulated input for the range of occupancy levels simulated. Throughout all experimental conditions simulated, the accuracy and robustness of the estimates using the data driven method were much improved upon the typical method of using a static time window, especially at low receptor occupancy levels. Introducing a reference region caused a bias of approximately 10% over the range of occupancy levels. CONCLUSIONS: Based on extensive simulated experimental conditions, it was shown the data driven method provides accurate and precise estimates of B(avail) and appK(D) for a broader range of conditions compared to the original method.

Simulation-based optimisation of the PET data processing for partial saturation approach protocols.

Positron emission tomography (PET) with [(11)C]Raclopride is an important tool for studying dopamine D2 receptor expression in vivo. [(11)C]Raclopride PET binding experiments conducted using the Partial Saturation Approach (PSA) allow the estimation of receptor density (B(avail)) and the in vivo affinity appK(D). The PSA is a simple, single injection, single scan experimental protocol that does not require blood sampling, making it ideal for use in longitudinal studies. In this work, we generated a complete Monte Carlo simulated PET study involving two groups of scans, in between which a biological phenomenon was inferred (a 30% decrease of B(avail)), and used it in order to design an optimal data processing chain for the parameter estimation from PSA data. The impact of spatial smoothing, noise removal and image resolution recovery technique on the statistical detection was investigated in depth. We found that image resolution recovery using iterative deconvolution of the image with the system point spread function associated with temporal data denoising greatly improves the accuracy and the statistical reliability of detecting the imposed phenomenon. Before optimisation, the inferred B(avail) variation between the two groups was underestimated by 42% and detected in 66% of cases, while a false decrease of appK(D) by 13% was detected in more than 11% of cases. After optimisation, the calculated B(avail) variation was underestimated by only 3.7% and detected in 89% of cases, while a false slight increase of appK(D) by 3.7% was detected in only 2% of cases. We found during this investigation that it was essential to adjust a factor that accounts for difference in magnitude between the non-displaceable ligand concentrations measured in the target and in the reference regions, for different data processing pathways as this ratio was affected by different image resolutions.

Integrated X-ray photoelectron spectroscopy and DFT characterization of benzene adsorption on Pt(111), Pt(355) and Pt(322) surfaces.

We systematically investigate the adsorption of benzene on Pt(111), Pt(355) and Pt(322) surfaces by high-resolution X-ray photoelectron spectroscopy (XPS) and first-principle calculations based on density functional theory (DFT), including van der Waals corrections. By comparing the adsorption energies at 1/9, 1/16 and 1/25 ML on Pt(111), we find significant lateral interactions exist between the benzene molecules at 1/9 ML. The adsorption behavior on Pt(355) and Pt(322) is very different. While on Pt(355) a step species is clearly identified in the C 1s spectra at low coverages followed by occupation of a terrace species at high coverages, no evidence for a step species is found on Pt(322). These different adsorption sites are confirmed by extensive DFT calculations, where the most favorable adsorption configurations on Pt(355) and Pt(322) are also found to vary: a highly distorted across the step molecule is found on Pt(355) while a less distorted configuration adjacent to the step molecule is deduced for Pt(322). The theoretically proposed C 1s core level binding energy shifts between these most favorable configurations and the terrace species are found to correlate well with experiment: for Pt(355), two adsorbate states are found, separated by ~0.4 eV in XPS and 0.3 eV in the calculations, in contrast to only one state on Pt(322).

Imaging DA release in a rat model of L-DOPA-induced dyskinesias: a longitudinal in vivo PET investigation of the antidyskinetic effect of MDMA.

In the context of Parkinson's disease, motor symptoms result from the degeneration of nigrostriatal neurons. Dopamine (DA) replacement using l-3,4-dihydroxyphenylalanine (L-DOPA) has been the treatment of choice in the early stages of the disease. However, with disease progression, patients suffer from motor complications, which have been suggested to arise from DA released from serotonergic terminals according to the false neurotransmitter hypothesis. The synthetic amphetamine derivative (±) 3,4-methylenedioxymethamphetamine (MDMA) has been shown to significantly inhibit dyskinesia in humans and in animal models of PD. In this study, we examined the effect of MDMA on L-DOPA-induced DA release by using [(11)C]raclopride kinetic modeling to assess alterations in DA neurotransmission in a rat model of L-DOPA-induced dyskinesia (LID) in a longitudinal in vivo PET study. Rats were submitted to 6-OHDA lesions, and the lesions were confirmed to be sufficiently severe based on the performance during stepping tests and [(11)C]methylphenidate PET scans. The rats underwent two [(11)C]raclopride PET sessions before (baseline) and after two weeks of chronic L-DOPA treatment (priming). L-DOPA priming led to strong abnormal involuntary movements (AIMs). In group 1, L-DOPA priming reduced L-DOPA-induced DA release in the lesioned striatum with no effect on the healthy side, while the concomitant administration of L-DOPA and MDMA (group 2) increased the DA levels in the lesioned and healthy striatum. In addition, behavioral analysis, which was performed two weeks after the second PET session, confirmed the antidyskinetic effect of MDMA. Our data show that L-DOPA-induced DA release is attenuated in the Parkinsonian striatum after chronic L-DOPA pretreatment and that the antidyskinetic mechanism of MDMA does not depend primarily on dopaminergic neurotransmission.

In vivo dopamine transporter imaging in a unilateral 6-hydroxydopamine rat model of Parkinson disease using 11C-methylphenidate PET.

UNLABELLED: Dopamine transporter (DAT) function is altered by many neurodegenerative diseases. For instance, in Parkinson disease DAT density has been shown to decrease in early disease and to play a role in the occurrence of motor complications. DAT is thus an important imaging target with potential therapeutic relevance in humans and animal models of disease. The PET DAT marker (11)C-methylphenidate is commonly used to quantify DAT function. Here we investigate the characteristics of the (11)C-methylphenidate-derived quantification of DAT in rodents using the 6-hydroxydopamine Parkinson disease rat model. METHODS: Seven unilaterally 6-hydroxydopamine-lesioned rats (dopaminergic denervation [DD] range, 36%-94%) were injected with 3.7 MBq/100 g of body weight and tracer masses ranging from 93.8 to 0.0041 µg/100 g of body weight. We evaluated the maximum available transporter density and the in vivo (apparent) ligand-transporter dissociation constant (B(max) and K app d, respectively) with an in vivo Scatchard method using several modeling approaches and estimated the transporter occupancy as a function of the amount of tracer injected and tracer specific activity (SA). RESULTS: Strong evidence of different nonspecific binding in the striatal region, compared with the reference region, leading to bias in the estimate of DD severity was found. One percent transporter occupancy was reached with 0.14 µg of tracer/100 g of body weight, corresponding to an SA of 5.7 kBq/pmol for the given radioactivity dose, and 10% occupancy was reached at 1.5 µg of tracer/100 g of body weight, corresponding to an SA of 0.57 kBq/pmol. The 6-hydroxydopamine lesion affected B(max) (control, 402 ± 94 pmol/mL; lesioned, 117 ± 120 pmol/mL; P = 0.003) but not K app d (control, 331 ± 63 pmol/mL; lesioned, 362 ± 119 pmol/mL; P = 0.63). CONCLUSION: Although DAT imaging can be performed at a relatively high mass of (11)C-methylphenidate (low SA), the additional nonspecific binding found in the striatum can introduce a DD severity-dependent bias in the estimate of tissue-derived binding potential and care must be taken in comparing (11)C-methylphenidate-derived assessment of DD with that obtained using other dopaminergic tracers.

In vivo quantification of dopamine transporters in mice with unilateral 6-OHDA lesions using [11C]methylphenidate and PET.

UNLABELLED: Quantification of the binding of [11C]methylphenidate to the dopamine transporter (DAT) using positron emission tomography (PET) is often used to evaluate the integrity of dopaminergic neurons in the striatal regions of the brain. Over the past decade, many genetically engineered mouse models of human disease have been developed and have become particularly useful for the study of disease onset and progression over time. Quantitative imaging of small structures such as the mouse brain is especially challenging. Thus, the aims of this study were (1) to evaluate the accuracy of quantifying DAT binding using in vivo PET and (2) to examine the impact of different methodologies. METHODS: Eight mice were scanned with [11C]methylphenidate under true or transient equilibrium conditions using a bolus and constant infusion protocol or a bolus injection protocol to evaluate the accuracy of the Logan graphical approach for [11C]methylphenidate imaging in mice. Displacement with unlabeled methylphenidate (0.1, 3 and 10 mg/kg) was used to verify specific binding. In a second experiment, 30 mice were lesioned by injection of 6-hydroxydopamine (6-OHDA) at doses of 0, 2 or 4 µg (n=10) into the right striatum to assess the dose-dependent correlation between the PET signal and dopaminergic degeneration. In addition, we performed test-retest experiments and used ex vivo autoradiography (AR) to validate the effect of partial volume on the accuracy of the [11C]methylphenidate PET quantification in the mouse striatum. RESULTS: The binding potentials (BPND) calculated from the Logan graphical analysis under transient equilibrium conditions (1.03±0.1) were in excellent agreement with those calculated at true equilibrium (1.07±0.1). Displacement of specific binding with 0.1, 3 and 10mg/kg methylphenidate resulted in 38%, 77% and 81% transporter occupancy in the striatum. Intra-striatal injections of 6-OHDA caused a dose-dependent decrease in the specific binding of [11C]methylphenidate to the DAT in the striatum. The BPND was reduced by 49% and 61% after injection with 2 and 4 µg of 6-OHDA, respectively. The test-retest reproducibility was 6% in the healthy striatum and 27% in the lesioned striatum. In addition, only a small (15%) difference was found between the [11C]methylphenidate DVR-1 values determined by PET and AR on the healthy side, and no differences were observed on the lesioned side. CONCLUSION: The present work demonstrates for the first time that [11C]methylphenidate PET is useful for the quantification of striatal dopamine transporters at the dopaminergic nerve terminals in the mouse striatum; therefore, this marker may be used as a biomarker in genetically engineered mouse models of neurodegenerative disorders. However, only changes resulting in greater than 10% differences in BPND values can reliably be detected in vivo.

Noninvasive nuclear imaging enables the in vivo quantification of striatal dopamine receptor expression and raclopride affinity in mice.

UNLABELLED: The increasing use of genetically engineered mice as animal models of human disease in biomedical research, latest advances in imaging technologies, and development of novel, highly specific radiolabeled biomarkers provide great potential to study receptor expression and gene function in vivo in mice. (11)C-raclopride is a widely used PET tracer to measure striatal D(2) receptor binding and was used to test the feasibility of the multiple-ligand-concentration receptor assay for D(2) receptor quantification. METHODS: Mice underwent a total of 4 scans with decreasing specific activities from 141 to 0.4 GBq/µmol, corresponding to (11)C-raclopride injected doses of 2.4 to 1,274 nmol/kg, using either a standard bolus injection protocol (n = 12) or a bolus-plus-constant infusion protocol to attain true equilibrium conditions (n = 7). Receptor occupancy was plotted as a function of raclopride dose, and D(2) receptor density and raclopride affinity were calculated using linear and nonlinear regression analysis, respectively. In addition, we used ex vivo autoradiography, a more spatially accurate imaging technology, to validate the in vivo PET measurements, and we performed test-retest experiments to determine the reproducibility and reliability of the PET-derived measures. RESULTS: The receptor occupancy curves showed that an injected tracer dose of 4.5 nmol/kg induces approximately 10% receptor occupancy, whereas 1% receptor occupancy will be achieved at tracer doses of approximately 0.45 nmol/kg. Using the bolus injection protocol and nonlinear regression analysis, we determined that the average D(2) receptor density was 9.6 ± 1.1 pmol/mL, and the apparent raclopride affinity was 5.0 ± 0.6 pmol/mL. These values agreed well with those obtained at true equilibrium conditions. In contrast, linear Scatchard analysis did not lead to the expected linear relationship because nonsaturable binding was observed at high raclopride concentrations, and thus, it seems to be unsuitable for quantitative (11)C-raclopride analysis in mice. CONCLUSION: Our data showed that the tracer mass, if higher than 4 nmol/kg, can strongly affect binding parameter estimations and must be considered when performing kinetic analysis, specifically in mice. We also demonstrated that the in vivo determination of D(2) receptor density and raclopride affinity is feasible in mice using multiple-injection protocols and nonlinear regression analysis.

A point mutation in the dynein heavy chain gene leads to striatal atrophy and compromises neurite outgrowth of striatal neurons.

The molecular motor dynein and its associated regulatory subunit dynactin have been implicated in several neurodegenerative conditions of the basal ganglia, such as Huntington's disease (HD) and Perry syndrome, an atypical Parkinson-like disease. This pathogenic role has been largely postulated from the existence of mutations in the dynactin subunit p150(Glued). However, dynactin is also able to act independently of dynein, and there is currently no direct evidence linking dynein to basal ganglia degeneration. To provide such evidence, we used here a mouse strain carrying a point mutation in the dynein heavy chain gene that impairs retrograde axonal transport. These mice exhibited motor and behavioural abnormalities including hindlimb clasping, early muscle weakness, incoordination and hyperactivity. In vivo brain imaging using magnetic resonance imaging showed striatal atrophy and lateral ventricle enlargement. In the striatum, altered dopamine signalling, decreased dopamine D1 and D2 receptor binding in positron emission tomography SCAN and prominent astrocytosis were observed, although there was no neuronal loss either in the striatum or substantia nigra. In vitro, dynein mutant striatal neurons displayed strongly impaired neuritic morphology. Altogether, these findings provide a direct genetic evidence for the requirement of dynein for the morphology and function of striatal neurons. Our study supports a role for dynein dysfunction in the pathogenesis of neurodegenerative disorders of the basal ganglia, such as Perry syndrome and HD.

Transgenic overexpression of the alpha-synuclein interacting protein synphilin-1 leads to behavioral and neuropathological alterations in mice.

Synphilin-1 has been identified as an interacting protein of alpha-synuclein, Parkin, and LRRK2, proteins which are mutated in familial forms of Parkinson disease (PD). Subsequently, synphilin-1 has also been shown to be an intrinsic component of Lewy bodies in sporadic PD. In order to elucidate the role of synphilin-1 in the pathogenesis of PD, we generated transgenic mice overexpressing wild-type and mutant (R621C) synphilin-1 driven by a mouse prion protein promoter. Transgenic expression of both wild-type and the R621C variant synphilin-1 resulted in increased dopamine levels of the nigrostriatal system in 3-month-old mice. Furthermore, we found pathological ubiquitin-positive inclusions in cerebellar sections and dark-cell degeneration of Purkinje cells. Both transgenic mouse lines showed significant reduction of motor skill learning and motor performance. These findings suggest a pathological role of overexpressed synphilin-1 in vivo and will help to further elucidate the mechanisms of protein aggregation and neuronal cell death.