Development and application of a novel recombinase polymerase amplification-Pyrococcus furiosus argonaute system for rapid detection of goose parvovirus.

Rapid and accurate detection of goose parvovirus (GPV) is crucial for controlling outbreaks and mitigating their economic impact on the poultry industry. This study introduces recombinase polymerase amplification combined with the Pyrococcus furiosus argonaute (RPA-PfAgo) system, a novel diagnostic platform designed to address the limitations of traditional GPV detection methods. Capitalizing on the rapid DNA amplification of RPA and stringent nucleic acid cleavage by the PfAgo protein, the RPA-PfAgo system offers high specificity and sensitivity in detecting GPV. Our optimization efforts included primer and probe configurations, reaction parameters, and guided DNA selection, culminating in a detection threshold of 102 GPV DNA copies per microlitre. The specificity of the proposed method was rigorously validated against a spectrum of avian pathogens. Clinical application to lung tissues from GPV-infected geese yielded a detection concordance of 100%, surpassing that of qPCR and PCR in both rapidity and operational simplicity. The RPA-PfAgo system has emerged as a revolutionary diagnostic modality for managing this disease, as it is a promising rapid, economical, and onsite GPV detection method amenable to integration into broad-scale disease surveillance frameworks. Future explorations will extend the applicability of this method to diverse avian diseases and assess its field utility across various epidemiological landscapes.

Development of an optimized RPA-PfAgo detection system for MTHFR C677T polymorphism genotyping.

This study introduces an efficient RPA-PfAgo detection system for the MTHFR C677T polymorphism, proposing a potential strategy to simplify the genotyping process. By optimizing recombinase polymerase amplification (RPA) with Pyrococcus furiosus Argonaute (PfAgo) nucleases, we achieved DNA amplification at a constant temperature. The assay was fine-tuned through meticulous primer and guide DNA selection, with optimal conditions established at 2.0 µL of MgAc, a reaction temperature of 42 °C, and a 10-minute reaction time for RPA. Further optimization of the PfAgo cleavage assay revealed the ideal concentrations of MnCl2, guide DNA, molecular beacon probes, the PfAgo enzyme, and the RPA product to maximize sensitivity and specificity. Clinical validation of 20 samples showed 100% concordance with Sanger sequencing, confirming the method's precision. The RPA-PfAgo system is a promising tool for on-site genotyping, with broad applications in personalized medicine and disease prevention.

Deficiency in endocannabinoid synthase DAGLB contributes to early onset Parkinsonism and murine nigral dopaminergic neuron dysfunction.

Endocannabinoid (eCB), 2-arachidonoyl-glycerol (2-AG), the most abundant eCB in the brain, regulates diverse neural functions. Here we linked multiple homozygous loss-of-function mutations in 2-AG synthase diacylglycerol lipase ß (DAGLB) to an early onset autosomal recessive Parkinsonism. DAGLB is the main 2-AG synthase in human and mouse substantia nigra (SN) dopaminergic neurons (DANs). In mice, the SN 2-AG levels were markedly correlated with motor performance during locomotor skill acquisition. Genetic knockdown of Daglb in nigral DANs substantially reduced SN 2-AG levels and impaired locomotor skill learning, particularly the across-session learning. Conversely, pharmacological inhibition of 2-AG degradation increased nigral 2-AG levels, DAN activity and dopamine release and rescued the locomotor skill learning deficits. Together, we demonstrate that DAGLB-deficiency contributes to the pathogenesis of Parkinsonism, reveal the importance of DAGLB-mediated 2-AG biosynthesis in nigral DANs in regulating neuronal activity and dopamine release, and suggest potential benefits of 2-AG augmentation in alleviating Parkinsonism.

Correction to: Parkinson's disease-related Leucine-rich repeat kinase 2 modulates nuclear morphology and genomic stability in striatal projection neurons during aging.

The original article had mistakenly inverted co-author, Wang Zheng's name. This has since been corrected.

Parkinson's disease-related Leucine-rich repeat kinase 2 modulates nuclear morphology and genomic stability in striatal projection neurons during aging.

BACKGROUND: Multiple missense mutations in Leucine-rich repeat kinase 2 (LRRK2) are associated with familial forms of late onset Parkinson's disease (PD), the most common age-related movement disorder. The dysfunction of dopamine transmission contributes to PD-related motor symptoms. Interestingly, LRRK2 is more abundant in the dopaminoceptive striatal spiny projection neurons (SPNs) compared to the dopamine-producing nigrostriatal dopaminergic neurons. Aging is the most important risk factor for PD and other neurodegenerative diseases. However, whether LRRK2 modulates the aging of SPNs remains to be determined. METHODS: We conducted RNA-sequencing (RNA-seq) analyses of striatal tissues isolated from Lrrk2 knockout (Lrrk2-/-) and control (Lrrk2+/+) mice at 2 and 12 months of age. We examined SPN nuclear DNA damage and epigenetic modifications; SPN nuclear, cell body and dendritic morphology; and the locomotion and motor skill learning of Lrrk2+/+ and Lrrk2-/- mice from 2 to 24 months of age. Considering the strength of cell cultures for future mechanistic studies, we also performed preliminary studies in primary cultured SPNs derived from the Lrrk2+/+ and Lrrk2-/- mice as well as the PD-related Lrrk2 G2019S and R1441C mutant mice. RESULTS: Lrrk2-deficiency accelerated nuclear hypertrophy and induced dendritic atrophy, soma hypertrophy and nuclear invagination in SPNs during aging. Additionally, increased nuclear DNA damage and abnormal histone methylations were also observed in aged Lrrk2-/- striatal neurons, together with alterations of molecular pathways involved in regulating neuronal excitability, genome stability and protein homeostasis. Furthermore, both the PD-related Lrrk2 G2019S mutant and LRRK2 kinase inhibitors caused nuclear hypertrophy, while the Lrrk2 R1441C mutant and γ-Aminobutyric acid type A receptor (GABA-AR) inhibitors promoted nuclear invagination in the cultured SPNs. On the other hand, inhibition of neuron excitability prevented the formation of nuclear invagination in the cultured Lrrk2-/- and R1441C SPNs. CONCLUSIONS: Our findings support an important physiological function of LRRK2 in maintaining nuclear structure integrity and genomic stability during the normal aging process, suggesting that PD-related LRRK2 mutations may cause the deterioration of neuronal structures through accelerating the aging process.

Distinct Connectivity and Functionality of Aldehyde Dehydrogenase 1a1-Positive Nigrostriatal Dopaminergic Neurons in Motor Learning.

Parkinson's disease causes the most profound loss of the aldehyde dehydrogenase 1A1-positive (ALDH1A1+) nigrostriatal dopaminergic neuron (nDAN) subpopulation. The connectivity and functionality of ALDH1A1+ nDANs, however, remain poorly understood. Here, we show in rodent brains that ALDH1A1+ nDANs project predominantly to the rostral dorsal striatum, from which they also receive most monosynaptic inputs, indicating extensive reciprocal innervations with the striatal spiny projection neurons (SPNs). Functionally, genetic ablation of ALDH1A1+ nDANs causes severe impairments in motor skill learning, along with a reduction in high-speed walking. While dopamine replacement therapy accelerated walking speed, it failed to improve motor skill learning in ALDH1A1+ nDAN-ablated mice. Altogether, our study provides a comprehensive whole-brain connectivity map and reveals a key physiological function of ALDH1A1+ nDANs in motor skill acquisition, suggesting the motor learning processes require ALDH1A1+ nDANs to integrate diverse presynaptic inputs and supply dopamine with dynamic precision.

ALDH1A1 regulates postsynaptic µ-opioid receptor expression in dorsal striatal projection neurons and mitigates dyskinesia through transsynaptic retinoic acid signaling.

Aldehyde dehydrogenase 1A1 (ALDH1A1), a retinoic acid (RA) synthase, is selectively expressed by the nigrostriatal dopaminergic (nDA) neurons that preferentially degenerate in Parkinson's disease (PD). ALDH1A1-positive axons mainly project to the dorsal striatum. However, whether ALDH1A1 and its products regulate the activity of postsynaptic striatal neurons is unclear. Here we show that µ-type opioid receptor (MOR1) levels were severely decreased in the dorsal striatum of postnatal and adult Aldh1a1 knockout mice, whereas dietary supplement of RA restores its expression. Furthermore, RA treatment also upregulates striatal MOR1 levels and signaling and alleviates L-DOPA-induced dyskinetic movements in pituitary homeobox 3 (Pitx3)-deficient mice that lack of ALDH1A1-expressing nDA neurons. Therefore, our findings demonstrate that ALDH1A1-synthesized RA is required for postsynaptic MOR1 expression in the postnatal and adult dorsal striatum, supporting potential therapeutic benefits of RA supplementation in moderating L-DOPA-induced dyskinesia.

Genetic ablation of dynactin p150Glued in postnatal neurons causes preferential degeneration of spinal motor neurons in aged mice.

BACKGROUND: Dynactin p150Glued, the largest subunit of the dynactin macromolecular complex, binds to both microtubules and tubulin dimers through the N-terminal cytoskeleton-associated protein and glycine-rich (CAP-Gly) and basic domains, and serves as an anti-catastrophe factor in stabilizing microtubules in neurons. P150Glued also initiates dynein-mediated axonal retrograde transport. Multiple missense mutations at the CAP-Gly domain of p150Glued are associated with motor neuron diseases and other neurodegenerative disorders, further supporting the importance of microtubule domains (MTBDs) in p150Glued functions. However, most functional studies were performed in vitro. Whether p150Glued is required for neuronal function and survival in vivo is unknown. METHODS: Using Cre-loxP genetic manipulation, we first generated a line of p150Glued knock-in mice by inserting two LoxP sites flanking the MTBD-coding exons 2 to 4 of p150Glued-encoding Dctn1 gene (Dctn1LoxP/), and then crossbred the resulting Dctn1LoxP/ mice with Thy1-Cre mice to generate the bigenic p150Glued (Dctn1LoxP/LoxP; Thy1-Cre) conditional knockout (cKO) mice for the downstream motor behavioral and neuropathological studies. RESULTS: P150Glued expression was completely abolished in Cre-expressing postnatal neurons, including corticospinal motor neurons (CSMNs) and spinal motor neurons (SMNs), while the MTBD-truncated forms remained. P150Glued ablation did not affect the formation of dynein/dynactin complex in neurons. The p150Glued cKO mice did not show any obvious developmental phenotypes, but exhibited impairments in motor coordination and rearing after 12 months of age. Around 20% loss of SMNs was found in the lumbar spinal cord of 18-month-old cKO mice, in company with increased gliosis, neuromuscular junction (NMJ) disintegration and muscle atrophy. By contrast, no obvious degeneration of CSMNs, striatal neurons, midbrain dopaminergic neurons, cerebellar granule cells or Purkinje cells was observed. Abnormal accumulation of acetylated α-tubulin, and autophagosome/lysosome proteins was found in the SMNs of aged cKO mice. Additionally, the total and cell surface levels of glutamate receptors were also substantially elevated in the p150Glued-depleted spinal neurons, in correlation with increased vulnerability to excitotoxicity. CONCLUSION: Overall, our findings demonstrate that p150Glued is particularly required to maintain the function and survival of SMNs during aging. P150Glued may exert its protective function through regulating the transportation of autophagosomes, lysosomes, and postsynaptic glutamate receptors in neurons.

AGE-induced neuronal cell death is enhanced in G2019S LRRK2 mutation with increased RAGE expression.

BACKGROUND: Leucine-rich repeat kinase 2 (LRRK2) mutations represent the most common genetic cause of sporadic and familial Parkinson's disease (PD). Especially, LRRK2 G2019S missense mutation has been identified as the most prevalent genetic cause in the late-onset PD. Advanced glycation end products (AGEs) are produced in high amounts in diabetes and diverse aging-related disorders, such as cardiovascular disease, renal disease, and neurological disease. AGEs trigger intracellular signaling pathway associated with oxidative stress and inflammation as well as cell death. RAGE, receptor of AGEs, is activated by interaction with AGEs and mediates AGE-induced cytotoxicity. Whether AGE and RAGE are involved in the pathogenesis of mutant LRRK2 is unknown. METHODS: Using cell lines transfected with mutant LRRK2 as well as primary neuronal cultures derived from LRRK2 wild-type (WT) and G2019S transgenic mice, we compared the impact of AGE treatment on the survival of control and mutant cells by immunostaining. We also examined the levels of RAGE proteins in the brains of transgenic mice and PD patients by western blots. RESULTS: We show that LRRK2 G2019S mutant-expressing neurons were more sensitive to AGE-induced cell death compared to controls. Furthermore, we found that the levels of RAGE proteins were upregulated in LRRK2 G2019S mutant cells. CONCLUSIONS: These data suggest that enhanced AGE-RAGE interaction contributes to LRRK2 G2019S mutation-mediated progressive neuronal loss in PD.

Absence of DJ-1 causes age-related retinal abnormalities in association with increased oxidative stress.

Oxidative stress alters physiological function in most biological tissues and can lead to cell death. In the retina, oxidative stress initiates a cascade of events leading to focal loss of RPE and photoreceptors, which is thought to be a major contributing factor to geographic atrophy. Despite these implications, the molecular regulation of RPE oxidative stress under normal and pathological conditions remains largely unknown. A better understanding of the mechanisms involved in regulating RPE and photoreceptors oxidative stress response is greatly needed. To this end we evaluated photoreceptor and RPE changes in mice deficient in DJ-1, a protein that is thought to be important in protecting cells from oxidative stress. Young (3 months) and aged (18 months) DJ-1 knockout (DJ-1 KO) and age-matched wild-type mice were examined. In both group of aged mice, scanning laser ophthalmoscopy (SLO) showed the presence of a few autofluorescent foci. The 18 month-old DJ-1 KO retinas were also characterized by a noticeable increase in RPE fluorescence to wild-type. Optical coherence tomography (OCT) imaging demonstrated that all retinal layers were present in the eyes of both DJ-1 KO groups. ERG comparisons showed that older DJ-1 KO mice had reduced sensitivity under dark- and light-adapted conditions compared to age-matched control. Histologically, the RPE contained prominent vacuoles in young DJ-1 KO group with the appearance of enlarged irregularly shaped RPE cells in the older group. These were also evident in OCT and in whole mount RPE/choroid preparations labeled with phalloidin. Photoreceptors in the older DJ-1 KO mice displayed decreased immunoreactivity to rhodopsin and localized reduction in cone markers compared to the wild-type control group. Lower levels of activated Nrf2 were evident in retina/RPE lysates in both young and old DJ-1 KO mouse groups compared to wild-type control levels. Conversely, higher levels of protein carbonyl derivatives and iNOS immunoreactivity were detected in retina/RPE lysates from both young and old DJ-1 KO mice. These results demonstrate that DJ-1 KO mice display progressive signs of retinal/RPE degeneration in association with higher levels of oxidative stress markers. Collectively this analysis indicates that DJ-1 plays an important role in protecting photoreceptors and RPE from oxidative damage during aging.

LRRK2 modulates microglial activity through regulation of chemokine (C-X3-C) receptor 1 -mediated signalling pathways.

Multiple missense mutations in Leucine-rich repeat kinase 2 (LRRK2) have been linked to Parkinson's disease (PD), the most common degenerative movement disorder. LRRK2 is expressed by both neurons and microglia, the residential immune cells in the brain. Increasing evidence supports a role of LRRK2 in modulating microglial activity, of which Lrrk2-null rodent microglia display less inflammatory response to endotoxin lipopolysaccharide (LPS). The underlying molecular mechanism, however, remains elusive. Chemokine (C-X3-C) receptor 1 (CX3CR1), predominantly expressed by microglia, suppresses microglial inflammation while promotes migration. Using whole-genome microarray screening, we found that Cx3cr1 mRNA levels were substantially higher in microglia derived from Lrrk2 knockout (Lrrk2-/-) mice. The total and cell surface levels of CX3CR1 proteins were also remarkably increased. In correlation with the enhanced CX3CR1 expression, Lrrk2-null microglia migrated faster and travelled longer distance toward the source of fractalkine (CX3CL1), an endogenous ligand of CX3CR1. To investigate the impact of CX3CR1 elevation in vivo, we compared LPS-induced inflammation in the striatum of Lrrk2-/- knockout mice with Cx3cr1 heterozygous and homozygous knockout background. We found that a complete loss of Cx3cr1 restored the responsiveness of Lrrk2-/- microglia to LPS stimulation. In conclusion, our findings reveal a previously unknown regulatory role for LRRK2 in CX3CR1 signalling and suggest that an increase of CX3CR1 activity contributes to the attenuated inflammatory responses in Lrrk2-null microglia.

No apparent transmission of transgenic α-synuclein into nigrostriatal dopaminergic neurons in multiple mouse models.

BACKGROUND: α-synuclein (α-syn) is the main component of intracytoplasmic inclusions deposited in the brains of patients with Parkinson's disease (PD) and certain other neurodegenerative disorders. Recent studies have explored the ability of α-syn to propagate between or across neighboring neurons and supposedly "infect" them with a prion-like mechanism. However, much of this research has used stereotaxic injections of heterologous α-syn fibrils to induce the spreading of inclusions in the rodent brains. Whether α-syn is able to transmit from the host cells to their neighboring cells in vivo is unclear. METHODS: Using immunestaining, we examined the potential propagation of α-syn into nigrostriatal dopaminergic (DA) neurons in three lines of transgenic mice that overexpress human wild-type α-syn (hα-syn) in different neuron populations. RESULTS: After testing for three different routes by which hα-syn propagation might occur, we were unable to find any evidence that hα-syn behaved like a prion and could be transmitted overtime into the DA neurons initially lack of hα-syn expression. CONCLUSIONS: In transgenic mice hα-syn does not have the ability to propagate at pathologically significant levels between or across neurons. It must be noted that these observations do not disprove the studies that show its prion-like qualities, but rather that propagation is not detectable in transgenic models that do not use any injections of heterologous proteins or viral vectors to induce a spreading state.

Longitudinal Metabolomics Profiling of Parkinson's Disease-Related α-Synuclein A53T Transgenic Mice.

Metabolic homeostasis is critical for all biological processes in the brain. The metabolites are considered the best indicators of cell states and their rapid fluxes are extremely sensitive to cellular changes. While there are a few studies on the metabolomics of Parkinson's disease, it lacks longitudinal studies of the brain metabolic pathways affected by aging and the disease. Using ultra-high performance liquid chromatography and tandem mass spectroscopy (UPLC/MS), we generated the metabolomics profiling data from the brains of young and aged male PD-related α-synuclein A53T transgenic mice as well as the age- and gender-matched non-transgenic (nTg) controls. Principal component and unsupervised hierarchical clustering analyses identified distinctive metabolites influenced by aging and the A53T mutation. The following metabolite set enrichment classification revealed the alanine metabolism, redox and acetyl-CoA biosynthesis pathways were substantially disturbed in the aged mouse brains regardless of the genotypes, suggesting that aging plays a more prominent role in the alterations of brain metabolism. Further examination showed that the interaction effect of aging and genotype only disturbed the guanosine levels. The young A53T mice exhibited lower levels of guanosine compared to the age-matched nTg controls. The guanosine levels remained constant between the young and aged nTg mice, whereas the aged A53T mice showed substantially increased guanosine levels compared to the young mutant ones. In light of the neuroprotective function of guanosine, our findings suggest that the increase of guanosine metabolism in aged A53T mice likely represents a protective mechanism against neurodegeneration, while monitoring guanosine levels could be applicable to the early diagnosis of the disease.

Loss of DJ-1 elicits retinal abnormalities, visual dysfunction, and increased oxidative stress in mice.

DJ-1/PARK7 mutations or deletions cause autosomal recessive early onset Parkinson's disease (PD). Thus, DJ-1 protein has been extensively studied in brain and neurons. PD patients display visual symptoms; however, the visual symptoms specifically attributed to PD patients carrying DJ-1/PARK7 mutations are not known. In this study, we analyzed the structure and physiology of retinas of 3- and 6-month-old DJ-1 knockout (KO) mice to determine how loss of function of DJ-1 specifically contributes to the phenotypes observed in PD patients. As compared to controls, the DJ-1 KO mice displayed an increase in the amplitude of the scotopic ERG b-wave and cone ERG, while the amplitude of a subset of the dc-ERG components was decreased. The main structural changes in the DJ-1 KO retinas were found in the outer plexiform layer (OPL), photoreceptors and retinal pigment epithelium (RPE), which were observed at 3 months and progressively increased at 6 months. RPE thinning and structural changes within the OPL were observed in the retinas in DJ-1 KO mice. DJ-1 KO retinas also exhibited disorganized outer segments, central decrease in red/green cone opsin staining, decreased labeling of ezrin, broader distribution of ribeye labeling, decreased tyrosine hydroxylase in dopaminergic neurons, and increased 7,8-dihydro-8-oxoguanine-labeled DNA oxidation. Accelerated outer retinal atrophy was observed in DJ-1 KO mice after selective oxidative damage induced by a single tail vein injection of NaIO3, exposing increased susceptibility to oxidative stress. Our data indicate that DJ-1-deficient retinas exhibit signs of morphological abnormalities and physiological dysfunction in association with increased oxidative stress. Degeneration of RPE cells in association with oxidative stress is a key hallmark of age-related macular degeneration (AMD). Therefore, in addition to detailing the visual defects that occur as a result of the absence of DJ-1, our data is also relevant to AMD pathogenesis.

Toll-Like Receptors Promote Mitochondrial Translocation of Nuclear Transcription Factor Nuclear Factor of Activated T-Cells in Prolonged Microglial Activation.

Microglia are resident macrophages in the CNS that scavenge pathogens, dying cells, and molecules using pattern recognition Toll-like receptors (TLRs). Nuclear factor of activated T-cells (NFAT) family transcription factors also regulate inflammatory responses in microglia. However, whether there exists cross talk between TLR and NFAT signaling is unclear. Here we show that chronic activation of murine microglia by prolonged stimulation of Toll-like receptor 4 (TLR4) ligand lipopolysaccharides (LPSs) leads to unexpected translocation of NFAT1 into mitochondria. This mitochondrial import of NFAT1 is independent of calcium/calcineurin signaling. Instead, inhibition of Toll/interleukin 1 receptor domain-containing adapter-inducing interferon-ß (TRIF) pathway blocks the mitochondrial translocation of NFAT1. Functionally, inhibition of NFAT1 reduces the TRIF-mediated expression of interferon-ß and compromises the production of ATP and reactive oxygen species in LPS-treated microglia. Therefore, our findings reveal a new inflammatory signaling pathway that links TLR with NFAT in regulating cytokine production and mitochondrial activity during chronic microglial activation. SIGNIFICANCE STATEMENT: Nuclear factor of activated T-cells (NFAT) family transcription factors are known to undergo nuclear translocation in response to inflammatory stimulation. In this study, we uncovered a surprise transportation of NFATs into mitochondria in microglia after a prolonged treatment with bacteria endotoxin lipopolysaccharides (LPSs). LPSs activated Toll-like receptor 4 and its downstream Toll/interleukin 1 receptor-domain-containing adapter-inducing interferon-ß (TRIF) to regulate the mitochondrial translocation of NFAT in microglia, whereas genetic inhibition of NFAT1 compromised TRIF-mediated cytokine production and reduced ATP and reactive oxygen species generation. These findings reveal a previously undescribed mitochondrial translocation of NFAT in microglia responding to extended activation of Toll-like receptor-mediated signaling transduction pathways.

Selective expression of Parkinson's disease-related Leucine-rich repeat kinase 2 G2019S missense mutation in midbrain dopaminergic neurons impairs dopamine release and dopaminergic gene expression.

Preferential dysfunction/degeneration of midbrain substantia nigra pars compacta (SNpc) dopaminergic (DA) neurons contributes to the main movement symptoms manifested in Parkinson's disease (PD). Although the Leucine-rich repeat kinase 2 (LRRK2) G2019S missense mutation (LRRK2 G2019S) is the most common causative genetic factor linked to PD, the effects of LRRK2 G2019S on the function and survival of SNpc DA neurons are poorly understood. Using a binary gene expression system, we generated transgenic mice expressing either wild-type human LRRK2 (WT mice) or the LRRK2 G2019S mutation (G2019S mice) selectively in the midbrain DA neurons. Here we show that overexpression of LRRK2 G2019S did not induce overt motor abnormalities or substantial SNpc DA neuron loss. However, the LRRK2 G2019S mutation impaired dopamine homeostasis and release in aged mice. This reduction in dopamine content/release coincided with the degeneration of DA axon terminals and decreased expression of DA neuron-enriched genes tyrosine hydroxylase (TH), vesicular monoamine transporter 2, dopamine transporter and aldehyde dehydrogenase 1. These factors are responsible for dopamine synthesis, transport and degradation, and their expression is regulated by transcription factor paired-like homeodomain 3 (PITX3). Levels of Pitx3 mRNA and protein were similarly decreased in the SNpc DA neurons of aged G2019S mice. Together, these findings suggest that PITX3-dependent transcription regulation could be one of the many potential mechanisms by which LRRK2 G2019S acts in SNpc DA neurons, resulting in downregulation of its downstream target genes critical for dopamine homeostasis and release.

Leucine-Rich Repeat Kinase 2 (Lrrk2) Deficiency Diminishes the Development of Experimental Autoimmune Uveitis (EAU) and the Adaptive Immune Response.

BACKGROUND: Mutations in LRRK2 are related to certain forms of Parkinson's disease and, possibly, to the pathogenesis of Crohn's disease. In both these diseases inflammatory processes participate in the pathogenic process. LRRK2 is expressed in lymphoid cells and, interestingly, Lrrk2 (-/-) mice were reported to develop more severe experimental colitis than their wild type (WT) controls. Here, we examined the possible involvement of LRRK2 in the pathogenesis of experimental autoimmune uveitis (EAU), an animal model for human uveitis, by testing Lrrk2 (-/-) mice for their capacity to develop this experimental eye disease and related immune responses. METHODS: Lrrk2 (-/-) mice and their WT controls (C57Bl/6) were immunized with interphotoreceptor retinoid-binding protein (IRBP) and compared for their development of EAU, delayed type hypersensitivity (DTH) by skin tests, production of cytokines in culture, and expression of interferon (IFN)-γ, interleukin (IL)-17 and FoxP3 by spleen cells, using flow cytometry. Peritoneal macrophages were examined for their production of cytokines/chemokines in culture following stimulation with LPS or the oligodeoxynucleotide CpG. The Lrrk2 (-/-) and WT mice were also compared for their response to bovine serum albumin (BSA). RESULTS: The Lrrk2 (-/-) mice developed lower levels of EAU, DTH responses and cytokine production by lymphocytes than did their WT controls. Intracellular expression of IFN-γ and IL-17, by spleen cells, and secretion of cytokines/chemokines by activated peritoneal macrophages of Lrrk2 (-/-) mice trended toward diminished levels, although variabilities were noted. The expression levels of FoxP3 by Lrrk2 (-/-) spleen cells, however, were similar to those seen in WT controls. Consistent with their low response to IRBP, Lrrk2 (-/-) mice responded to BSA less vigorously than their WT controls. CONCLUSIONS: Lrrk2 deficiency in mice diminished the development of EAU and the related adaptive immune responses to IRBP as compared to the WT controls.

Leucine-rich repeat kinase 2 regulates Sec16A at ER exit sites to allow ER-Golgi export.

Leucine-rich repeat kinase 2 (LRRK2) has been associated with Parkinson's disease (PD) and other disorders. However, its normal physiological functions and pathogenic properties remain elusive. Here we show that LRRK2 regulates the anterograde ER-Golgi transport through anchoring Sec16A at the endoplasmic reticulum exit sites (ERES). LRRK2 interacted and co-localized with Sec16A, a key protein in the formation of ERES. Lrrk2 depletion caused a dispersion of Sec16A from ERES and impaired ER export. In neurons, LRRK2 and Sec16A showed extensive co-localization at the dendritic ERES (dERES) that locally regulate the transport of proteins to the dendritic spines. A loss of Lrrk2 affected the association of Sec16A with dERES and impaired the activity-dependent targeting of glutamate receptors onto the cell/synapse surface. Furthermore, the PD-related LRRK2 R1441C missense mutation in the GTPase domain interfered with the interaction of LRRK2 with Sec16A and also affected ER-Golgi transport, while LRRK2 kinase activity was not required for these functions. Therefore, our findings reveal a new physiological function of LRRK2 in ER-Golgi transport, suggesting ERES dysfunction may contribute to the pathogenesis of PD.

A calcineurin- and NFAT-dependent pathway is involved in α-synuclein-induced degeneration of midbrain dopaminergic neurons.

Parkinson's disease (PD), the most common degenerative movement disorder, is caused by a preferential loss of midbrain dopaminergic (mDA) neurons. Both α-synuclein (α-syn) missense and multiplication mutations have been linked to PD. However, the underlying intracellular signalling transduction pathways of α-syn-mediated mDA neurodegeneration remain elusive. Here, we show that transgenic expression of PD-related human α-syn A53T missense mutation promoted calcineurin (CN) activity and the subsequent nuclear translocation of nuclear factor of activated T cells (NFATs) in mDA neurons. α-syn enhanced the phosphatase activity of CN in both cell-free assays and cell lines transfected with either human wild-type or A53T α-syn. Furthermore, overexpression of α-syn A53T mutation significantly increased the CN-dependent nuclear import of NFATc3 in the mDA neurons of transgenic mice. More importantly, a pharmacological inhibition of CN by cyclosporine A (CsA) ameliorated the α-syn-induced loss of mDA neurons. These findings demonstrate an active involvement of CN- and NFAT-mediated signalling pathway in α-syn-mediated degeneration of mDA neurons in PD.

Aldehyde dehydrogenase 1 defines and protects a nigrostriatal dopaminergic neuron subpopulation.

Subpopulations of dopaminergic (DA) neurons within the substantia nigra pars compacta (SNpc) display a differential vulnerability to loss in Parkinson's disease (PD); however, it is not clear why these subsets are preferentially selected in PD-associated neurodegeneration. In rodent SNpc, DA neurons can be divided into two subpopulations based on the expression of aldehyde dehydrogenase 1 (ALDH1A1). Here, we have shown that, in α-synuclein transgenic mice, a murine model of PD-related disease, DA neurodegeneration occurs mainly in a dorsomedial ALDH1A1-negative subpopulation that is also prone to cytotoxic aggregation of α-synuclein. Notably, the topographic ALDH1A1 pattern observed in α-synuclein transgenic mice was conserved in human SNpc. Postmortem evaluation of brains of patients with PD revealed a severe reduction of ALDH1A1 expression and neurodegeneration in the ventral ALDH1A1-positive DA subpopulations. ALDH1A1 expression was also suppressed in α-synuclein transgenic mice. Deletion of Aldh1a1 exacerbated α-synuclein-mediated DA neurodegeneration and α-synuclein aggregation, whereas Aldh1a1-null and control DA neurons were comparably susceptible to 1-methyl-4-phenylpyridinium-, glutamate-, or camptothecin-induced cell death. ALDH1A1 overexpression appeared to preferentially protect against α-synuclein-mediated DA neurodegeneration but did not rescue α-synuclein-induced loss of cortical neurons. Together, our findings suggest that ALDH1A1 protects subpopulations of SNpc DA neurons by preventing the accumulation of dopamine aldehyde intermediates and formation of cytotoxic α-synuclein oligomers.