Distinct subcellular autophagy impairments in induced neurons from patients with Huntington's disease.

Huntington's disease is a neurodegenerative disorder caused by CAG expansions in the huntingtin (HTT) gene. Modelling Huntington's disease is challenging, as rodent and cellular models poorly recapitulate the disease as seen in ageing humans. To address this, we generated induced neurons through direct reprogramming of human skin fibroblasts, which retain age-dependent epigenetic characteristics. Huntington's disease induced neurons (HD-iNs) displayed profound deficits in autophagy, characterized by reduced transport of late autophagic structures from the neurites to the soma. These neurite-specific alterations in autophagy resulted in shorter, thinner and fewer neurites specifically in HD-iNs. CRISPRi-mediated silencing of HTT did not rescue this phenotype but rather resulted in additional autophagy alterations in control induced neurons, highlighting the importance of wild-type HTT in normal neuronal autophagy. In summary, our work identifies a distinct subcellular autophagy impairment in adult patient derived Huntington's disease neurons and provides a new rationale for future development of autophagy activation therapies.

Portrait of blood-derived extracellular vesicles in patients with Parkinson's disease.

The production of extracellular vesicles (EV) is a ubiquitous feature of eukaryotic cells but pathological events can affect their formation and constituents. We sought to characterize the nature, profile and protein signature of EV in the plasma of Parkinson's disease (PD) patients and how they correlate to clinical measures of the disease. EV were initially collected from cohorts of PD (n = 60; Controls, n = 37) and Huntington's disease (HD) patients (Pre-manifest, n = 11; manifest, n = 52; Controls, n = 55) - for comparative purposes in individuals with another chronic neurodegenerative condition - and exhaustively analyzed using flow cytometry, electron microscopy and proteomics. We then collected 42 samples from an additional independent cohort of PD patients to confirm our initial results. Through a series of iterative steps, we optimized an approach for defining the EV signature in PD. We found that the number of EV derived specifically from erythrocytes segregated with UPDRS scores corresponding to different disease stages. Proteomic analysis further revealed that there is a specific signature of proteins that could reliably differentiate control subjects from mild and moderate PD patients. Taken together, we have developed/identified an EV blood-based assay that has the potential to be used as a biomarker for PD.

Peripheral adaptive immunity of the triple transgenic mouse model of Alzheimer's disease.

BACKGROUND: Immunologic abnormalities have been described in peripheral blood and central nervous system of patients suffering from Alzheimer's disease (AD), yet their role in the pathogenesis still remains poorly defined. AIM AND METHODS: We used the triple transgenic mouse model (3xTg-AD) to reproduce Aß (amyloid plaques) and tau (neurofibrillary tangles) neuropathologies. We analyzed important features of the adaptive immune system in serum, primary (bone marrow) as well as secondary (spleen) lymphoid organs of 12-month-old 3xTg-AD mice using flow cytometry and ELISPOT. We further investigated serum cytokines of 9- and 13-month-old 3xTg-AD mice using multiplex ELISA. Results were compared to age-matched non-transgenic controls (NTg). RESULTS: In the bone marrow of 12-month-old 3xTg-AD mice, we detected decreased proportions of short-term reconstituting hematopoietic stem cells (0.58-fold, P = 0.0116), while lymphocyte, granulocyte, and monocyte populations remained unchanged. Our results also point to increased activation of both B and T lymphocytes. Indeed, we report elevated levels of plasma cells in bone marrow (1.3-fold, P = 0.0405) along with a 5.4-fold rise in serum IgG concentration (P < 0.0001) in 3xTg-AD animals. Furthermore, higher levels of interleukin (IL)-2 were detected in serum of 9- and 13-month-old 3xTg-AD mice (P = 0.0018). Along with increased concentrations of IL-17 (P = 0.0115) and granulocyte-macrophage colony-stimulating factor (P = 0.0085), these data support helper T lymphocyte activation with Th17 polarization. CONCLUSION: Collectively, these results suggest that the 3xTg-AD model mimics modifications of the adaptive immunity changes previously observed in human AD patients and underscore the activation of both valuable and harmful pathways of immunity in AD.

Platelet abnormalities in Huntington's disease.

Huntington's disease (HD) is a hereditary disorder that typically manifests in adulthood with a combination of motor, cognitive and psychiatric problems. The pathology is caused by a mutation in the huntingtin gene which results in the production of an abnormal protein, mutant huntingtin (mHtt). This protein is ubiquitously expressed and known to confer toxicity to multiple cell types. We have recently reported that HD brains are also characterised by vascular abnormalities, which include changes in blood vessel density/diameter as well as increased blood-brain barrier (BBB) leakage. OBJECTIVES: Seeking to elucidate the origin of these vascular and BBB abnormalities, we studied platelets that are known to play a role in maintaining the integrity of the vasculature and thrombotic pathways linked to this, given they surprisingly contain the highest concentration of mHtt of all blood cells. METHODS: We assessed the functional status of platelets by performing ELISA, western blot and RNA sequencing in a cohort of 71 patients and 68 age- and sex-matched healthy control subjects. We further performed haemostasis and platelet depletion tests in the R6/2 HD mouse model. RESULTS: Our findings indicate that the platelets in HD are dysfunctional with respect to the release of angiogenic factors and functions including thrombosis, angiogenesis and vascular haemostasis. CONCLUSION: Taken together, our results provide a better understanding for the impact of mHtt on platelet function.

Co-occurrence of mixed proteinopathies in late-stage Huntington's disease.

Accumulating evidence highlights the potential role of mixed proteinopathies (i.e., abnormal protein aggregation) in the development of clinical manifestations of neurodegenerative diseases (NDD). Huntington's disease (HD) is an inherited NDD caused by autosomal-dominant expanded CAG trinucleotide repeat mutation in the gene coding for Huntingtin (Htt). Previous studies have suggested the coexistence of phosphorylated-Tau, α-synuclein (α-Syn) and TAR DNA-binding protein 43 (TDP-43) inclusions in HD. However, definite evidence that HD pathology in humans can be accompanied by other proteinopathies is still lacking. Using human post-mortem putamen samples from 31 controls and 56 HD individuals, we performed biochemical analyses of the expression, oligomerization and aggregation of Tau, α-Syn, TDP-43, and Amyloid precursor protein (APP)/Aß. In HD brain, we observed reduced soluble protein (but not mRNA) levels of Htt, α-Syn, and Tau. Our results also support abnormal phosphorylation of Tau in more advanced stages of disease. Aberrant splicing of Tau exons 2, 3 (exclusion) and 10 (inclusion) was also detected in HD patients, leading to higher 0N4R and lower 1N3R isoforms. Finally, following formic acid extraction, we observed increased aggregation of TDP-43, α-Syn, and phosphorylated-Tau during HD progression. Notably, we observed that 88% of HD patients with Vonsattel grade 4 neuropathology displayed at least one non-Htt proteinopathy compared to 29% in controls. Interestingly, α-Syn aggregation correlated with Htt, TDP-43 and phosphorylated-Tau in HD but not in controls. The impact of this work is twofold: (1) it provides compelling evidences that Tau, α-Syn and TDP-43 proteinopathies are increased in HD, and (2) it suggests the involvement of common mechanisms leading to abnormal accumulation of aggregation-prone proteins in NDD. Further studies will be needed to decipher the impact of these proteinopathies on clinical manifestation of HD.

Characterization of a 3xTg-AD mouse model of Alzheimer's disease with the senescence accelerated mouse prone 8 (SAMP8) background.

No model fully recapitulates the neuropathology of Alzheimer's disease (AD). Although the triple-transgenic mouse model of AD (3xTg-AD) expresses Aß plaques and tau-laden neurofibrillary tangles, as well as synaptic and behavioral deficits, it does not display frank neuronal loss. Because old age is the most important risk factor in AD, senescence-related interactions might be lacking to truly establish an AD-like environment. To investigate this hypothesis, we bred the 3xTg-AD mouse with the senescence-accelerated mouse prone 8 (SAMP8), a model of accelerated aging. We generated four groups of heterozygous mice with either the SAMP8 or SAMR1 (senescence-resistant-1) genotype, along with either the 3xTg-AD or non-transgenic (NonTg) genotype. Despite no differences among groups in total latency to escape the Barnes maze, a greater number of errors were noticed before entering the target hole in 19-month-old P8/3xTg-AD mice at day 5, compared to other groups. Postmortem analyses revealed increased cortical levels of phospho-tau (Thr231) in female P8/3xTg-AD mice (+277% vs. R1/3xTg-AD mice), without other tau-related changes. Female P8/3xTg-AD mice exhibited higher cortical soluble Aß40 and Aß42 concentrations (Aß40, +85%; Aß42, +35% vs. R1/3xTg-AD), whereas insoluble forms remained unchanged. Higher Aß42 load coincided with increased astroglial activation in female P8/3xTg-AD mice, as measured with glial fibrillary acidic protein (GFAP) (+57% vs. R1/3xTg-AD mice). To probe neuronal degeneration, concentrations of neuronal nuclei (NeuN) were measured, but no differences were detected between groups. Altogether, the SAMP8 genotype had deleterious effects on spatial memory and exerted female-specific aggravation of AD neuropathology without overt neurodegeneration in 3xTg-AD mice.

Cerebrovascular and blood-brain barrier impairments in Huntington's disease: Potential implications for its pathophysiology.

OBJECTIVE: Although the underlying cause of Huntington's disease (HD) is well established, the actual pathophysiological processes involved remain to be fully elucidated. In other proteinopathies such as Alzheimer's and Parkinson's diseases, there is evidence for impairments of the cerebral vasculature as well as the blood-brain barrier (BBB), which have been suggested to contribute to their pathophysiology. We investigated whether similar changes are also present in HD. METHODS: We used 3- and 7-Tesla magnetic resonance imaging as well as postmortem tissue analyses to assess blood vessel impairments in HD patients. Our findings were further investigated in the R6/2 mouse model using in situ cerebral perfusion, histological analysis, Western blotting, as well as transmission and scanning electron microscopy. RESULTS: We found mutant huntingtin protein (mHtt) aggregates to be present in all major components of the neurovascular unit of both R6/2 mice and HD patients. This was accompanied by an increase in blood vessel density, a reduction in blood vessel diameter, as well as BBB leakage in the striatum of R6/2 mice, which correlated with a reduced expression of tight junction-associated proteins and increased numbers of transcytotic vesicles, which occasionally contained mHtt aggregates. We confirmed the existence of similar vascular and BBB changes in HD patients. INTERPRETATION: Taken together, our results provide evidence for alterations in the cerebral vasculature in HD leading to BBB leakage, both in the R6/2 mouse model and in HD patients, a phenomenon that may, in turn, have important pathophysiological implications.

Immunotherapies in Alzheimer's disease: Too much, too little, too late or off-target?

Years of research have highlighted the importance of the immune system in Alzheimer's disease (AD), a system that, if manipulated during strategic time windows, could potentially be tackled to treat this disorder. However, to minimize adverse effects, it is essential to first grasp which exact aspect of it may be targeted. Several clues have been collected over the years regarding specific immune players strongly modulated during different stages of AD progression. However, the inherent complexity of the immune system as well as conflicting data make it quite challenging to pinpoint a specific immune target in AD. In this review, we discuss immune-related abnormalities observed in the periphery as well as in the brain of AD patients, in relation to known risk factors of AD such as genetics, type-2 diabetes or obesity, aging, physical inactivity and hypertension. Although not investigated yet in clinical trials, C5 complement system component, CD40/CD40L interactions and the CXCR2 pathway are altered in AD patients and may represent potential therapeutic targets. Immunotherapies tested in a clinical context, those aiming to attenuate the innate immune response and those used to facilitate the removal of pathological proteins, are further discussed to try and understand the causes of the limited success reached. The prevailing eagerness to move basic research data to clinic should not overshadow the fact that a careful preclinical characterization of a drug is still required to ultimately improve the chance of clinical success. Finally, specific elements to consider prior to initiate large-scale trials are highlighted and include the replication of preclinical data, the use of small-scale human studies, the sub-typing of AD patients and the determination of pharmacokinetic and pharmacodynamics parameters such as brain bioavailability and target engagement.

Age-dependent impairment of glucose tolerance in the 3xTg-AD mouse model of Alzheimer's disease.

Alzheimer's disease (AD) has been associated with type II diabetes (T2D) and obesity in several epidemiologic studies. To determine whether AD neuropathology can cause peripheral metabolic impairments, we investigated metabolic parameters in the triple-transgenic (3xTg)-AD mouse model of AD, compared with those in nontransgenic (non-Tg) controls, at 6, 8, and 14 mo of age. We found a more pronounced cortical Aß accumulation (2- and 3.5-fold increase in Aß42 in the soluble and insoluble protein fractions, respectively) in female 3xTg-AD mice than in the males. Furthermore, female 3xTg-AD mice displayed a significant deterioration in glucose tolerance (AUC, +118% vs. non-Tg mice at 14 mo). Fasting plasma insulin levels rose 2.5-fold from 6 to 14 mo of age in female 3xTg-AD mice. Glucose intolerance and cortical amyloid pathology worsened with age, and both were more pronounced in the females. Pancreatic amyloidopathy was revealed and could underlie the observed deficit in glycemic response in 3xTg-AD mice. The present results suggest that AD-like neuropathology extends to the pancreas in the 3xTg-AD mouse, leading to glucose intolerance and contributing to a pathologic self-amplifying loop between AD and T2D.

Mutant huntingtin is present in neuronal grafts in Huntington disease patients.

OBJECTIVE: Huntington disease (HD) is caused by a genetically encoded pathological protein (mutant huntingtin [mHtt]), which is thought to exert its effects in a cell-autonomous manner. Here, we tested the hypothesis that mHtt is capable of spreading within cerebral tissue by examining genetically unrelated fetal neural allografts within the brains of patients with advancing HD. METHODS: The presence of mHtt aggregates within the grafted tissue was confirmed using 3 different types of microscopy (bright-field, fluorescence, and electron), 2 additional techniques consisting of Western immunoblotting and infrared spectroscopy, and 4 distinct antibodies targeting different epitopes of mHtt aggregates. RESULTS: We describe the presence of mHtt aggregates within intracerebral allografts of striatal tissue in 3 HD patients who received their transplants approximately 1 decade earlier and then died secondary to the progression of their disease. The mHtt(+) aggregates were observed in the extracellular matrix of the transplanted tissue, whereas in the host brain they were seen in neurons, neuropil, extracellular matrix, and blood vessels. INTERPRETATION: This is the first demonstration of the presence of mHtt in genetically normal and unrelated allografted neural tissue transplanted into the brain of affected HD patients. These observations raise questions on protein spread in monogenic neurodegenerative disorders of the central nervous system characterized by the formation of mutant protein oligomers/aggregates.

IVIg protects the 3xTg-AD mouse model of Alzheimer's disease from memory deficit and Aß pathology.

BACKGROUND: Intravenous immunoglobulin (IVIg) is currently in clinical study for Alzheimer's disease (AD). However, preclinical investigations are required to better understand AD-relevant outcomes of IVIg treatment and develop replacement therapies in case of unsustainable supply. METHODS: We investigated the effects of IVIg in the 3xTg-AD mouse model, which reproduces both Aß and tau pathologies. Mice were injected twice weekly with 1.5 g/kg IVIg for 1 or 3 months. RESULTS: IVIg induced a modest but significant improvement in memory in the novel object recognition test and attenuated anxiety-like behavior in 3xTg-AD mice. We observed a correction of immunologic defects present in 3xTg-AD mice (-22% CD4/CD8 blood ratio; -17% IL-5/IL-10 ratio in the cortex) and a modulation of CX3CR1+ cell population (-13% in the bone marrow). IVIg treatment led to limited effects on tau pathology but resulted in a 22% reduction of the soluble Aß42/Aß40 ratio and a 60% decrease in concentrations of 56 kDa Aß oligomers (Aß*56). CONCLUSION: The memory-enhancing effect of IVIg reported here suggests that Aß oligomers, effector T cells and the fractalkine pathway are potential pharmacological targets of IVIg in AD.

The morphological and molecular changes of brain cells exposed to direct current electric field stimulation.

BACKGROUND: The application of low-intensity direct current electric fields has been experimentally used in the clinic to treat a number of brain disorders, predominantly using transcranial direct current stimulation approaches. However, the cellular and molecular changes induced by such treatment remain largely unknown. METHODS: Here, we tested various intensities of direct current electric fields (0, 25, 50, and 100V/m) in a well-controlled in vitro environment in order to investigate the responses of neurons, microglia, and astrocytes to this type of stimulation. This included morphological assessments of the cells, viability, as well as shape and fiber outgrowth relative to the orientation of the direct current electric field. We also undertook enzyme-linked immunosorbent assays and western immunoblotting to identify which molecular pathways were affected by direct current electric fields. RESULTS: In response to direct current electric field, neurons developed an elongated cell body shape with neurite outgrowth that was associated with a significant increase in growth associated protein-43. Fetal midbrain dopaminergic explants grown in a collagen gel matrix also showed a reorientation of their neurites towards the cathode. BV2 microglial cells adopted distinct morphological changes with an increase in cyclooxygenase-2 expression, but these were dependent on whether they had already been activated with lipopolysaccharide. Finally, astrocytes displayed elongated cell bodies with cellular filopodia that were oriented perpendicularly to the direct current electric field. CONCLUSION: We show that cells of the central nervous system can respond to direct current electric fields both in terms of their morphological shape and molecular expression of certain proteins, and this in turn can help us to begin understand the mechanisms underlying the clinical benefits of direct current electric field.

Toll-like receptor expression in the blood and brain of patients and a mouse model of Parkinson's disease.

BACKGROUND: Accumulating evidence supports a role for the immune system in the pathogenesis of Parkinson's disease. Importantly, recent preclinical studies are now suggesting a specific contribution of inflammation to the α-synuclein-induced pathology seen in this condition. METHODS: We used flow cytometry and western blots to detect toll-like receptor 2 and 4 expression in blood and brain samples of Parkinson's disease patients and mice overexpressing human α-synuclein. To further assess the effects of α-synuclein overexpression on the innate immune system, we performed a longitudinal study using Thy1.2-α-synuclein mice that expressed a bicistronic DNA construct (reporter genes luciferase and green fluorescent protein) under the transcriptional control of the murine toll-like receptor 2 promoter. RESULTS: Here, we report increases in toll-like receptors 2 and 4 expression in circulating monocytes and of toll-like receptor 4 in B cells and in the caudate/putamen of Parkinson's disease patients. Monthly bioluminescence imaging of Thy1.2-α-synuclein mice showed increasing toll-like receptor 2 expression from 10 months of age, although no change in toll-like receptor 2 and 4 expression was observed in the blood and brain of these mice at 12 months of age. Dexamethasone treatment starting at 5 months of age for 1 month significantly decreased the microglial response in the brain of these mice and promoted functional recovery as observed using a wheel-running activity test. CONCLUSION: Our results show that toll-like receptors 2 and 4 are modulated in the blood and brain of Parkinson's disease patients and that overexpression of α-synuclein leads to a progressive microglial response, the inhibition of which has a beneficial impact on some motor phenotypes of an animal model of α-synucleinopathy.

The different effects of LPS and poly I:C prenatal immune challenges on the behavior, development and inflammatory responses in pregnant mice and their offspring.

In recent years, in vivo animal models of prenatal infection have been developed in an attempt to recreate behavioral and neuropathological features associated to a number of neurological and neuropsychiatric disorders. However, these models are still in their emerging phase and a better understanding of how these types of infections relate to adult-onset of brain-related disorders is needed. Here, we undertook an extensive behavioral characterization of both pregnant females and their pups following late gestational exposure (from gestational days (GD) 15-17) to either lipopolysaccharide (LPS; 120µg/kg i.p.) or polyinosinic:polycytidylic acid (poly I:C; 5mg/kg i.v.). We observed that both LPS and poly I:C treatments produced anxiety-like behaviors in treated pregnant females, although to a lesser extent with LPS. LPS injections, but not poly I:C, led to reduced food intake and consequently decreased weight gain in pregnant dams. In pups, poly I:C treatments triggered a delay in growth and sensorimotor development, as evaluated by righting, geotaxis and grasping reflexes. At the cellular level, both toxins induced an initial inflammatory response while only LPS reduced the expression of brain cell markers in foetuses (GFAP and NeuN), which was no longer observable at postnatal day (PnD) 10. Higher levels of IL-2, IL-5 and IL-6 in plasma and an upregulation of the metabotropic receptor 5 (mGluR5) in foetal brains of 10-day-old offspring prenatally exposed to poly I:C was also observed. Interestingly, the increased mGluR5 expression correlated with impairments of the righting reflex. This study is the first to directly compare reflex development following LPS and poly I:C prenatal immune challenges in mice and sheds light onto the different patterns of behavior and pathology in dams and their offspring.

Beneficial effects of miR-132/212 deficiency in the zQ175 mouse model of Huntington's disease.

Huntington's disease (HD) is a rare genetic neurodegenerative disorder caused by an expansion of CAG repeats in the Huntingtin (HTT) gene. One hypothesis suggests that the mutant HTT gene contributes to HD neuropathology through transcriptional dysregulation involving microRNAs (miRNAs). In particular, the miR-132/212 cluster is strongly diminished in the HD brain. This study explores the effects of miR-132/212 deficiency specifically in adult HD zQ175 mice. The absence of miR-132/212 did not impact body weight, body temperature, or survival rates. Surprisingly, miR-132/212 loss seemed to alleviate, in part, the effects on endogenous Htt expression, HTT inclusions, and neuronal integrity in HD zQ175 mice. Additionally, miR-132/212 depletion led to age-dependent improvements in certain motor functions. Transcriptomic analysis revealed alterations in HD-related networks in WT- and HD zQ175-miR-132/212-deficient mice, including significant overlap in BDNF and Creb1 signaling pathways. Interestingly, however, a higher number of miR-132/212 gene targets was observed in HD zQ175 mice lacking the miR-132/212 cluster, especially in the striatum. These findings suggest a nuanced interplay between miR-132/212 expression and HD pathogenesis, providing potential insights into therapeutic interventions. Further investigation is needed to fully understand the underlying mechanisms and therapeutic potential of modulating miR-132/212 expression during HD progression.

Differential Regulation of Tau Exon 2 and 10 Isoforms in Huntington's Disease Brain.

Huntington's disease (HD) is an inherited neurodegenerative disorder caused by an expansion of CAG repeats in the Huntingtin (HTT) gene. Accumulating evidence suggests that the microtubule-associated tau protein participates in the pathogenesis of HD. Recently, we have identified changes in tau alternative splicing of exons 2, 3 and 10 in the putamen of HD patients (St-Amour et al, 2018). In this study, we sought to determine whether tau mis-splicing events were equally observed in other brain regions that are less prone to neurodegeneration. Using Western blot and PCR, we characterized the relationship between MAPT splicing of exons 2, 3 and 10, tauopathy and Htt pathologies, as well as neurodegeneration markers in matching putamen and cortical samples from HD (N = 48) and healthy control (N = 25) subjects. We first show that levels of 4R-tau (exon 10 inclusion) isoforms are higher in both the putamen and the cortex of individuals with HD, consistent with earlier findings. On the other hand, higher 0N-tau (exclusion of exons 2 and 3) and lower 1N-tau (exclusion of exon 3) isoforms were seen exclusively in the putamen of HD individuals. Interestingly, investigated splicing factors were deregulated in both regions whereas exon 2 differences coincided with increased tau hyperphosphorylation, aggregation and markers of neurodegeneration. Overall, these results imply a differential regulation of tau exon 2 and exon 10 alternative splicing in HD putamen that could provide a useful biomarker or therapeutic target.

Impact of intravenous immunoglobulin on the dopaminergic system and immune response in the acute MPTP mouse model of Parkinson's disease.

Intravenous immunoglobulin (IVIg) is a blood-derived product, used for the treatment of immunodeficiency and autoimmune diseases. Since a range of immunotherapies have recently been proposed as a therapeutic strategy for Parkinson's disease (PD), we investigated the effects of an IVIg treatment in a neurotoxin-induced animal model of PD. Mice received four injections of MPTP (15 mg/kg) at 2-hour intervals followed by a 14-day IVIg treatment, which induced key immune-related changes such as increased regulatory T-cell population and decreased CD4(+)/CD8(+) ratio. The MPTP treatment induced significant 80% and 84% decreases of striatal dopamine concentrations (P < 0.01), as well as 33% and 40% reductions in the number of nigral dopaminergic neurons (P < 0.001) in controls and IVIg-treated mice, respectively. Two-way analyses of variance further revealed lower striatal tyrosine hydroxylase protein levels, striatal homovanillic acid concentrations and nigral dopaminergic neurons (P < 0.05) in IVIg-treated animals. Collectively, our results fail to support a neurorestorative effect of IVIg on the nigrostriatal system in the MPTP-treated mice and even suggest a trend toward a detrimental effect of IVIg on the dopaminergic system. These preclinical data underscore the need to proceed with caution before initiating clinical trials of IVIg in PD patients.

Widespread alterations in microRNA biogenesis in human Huntington's disease putamen.

Altered microRNA (miRNA) expression is a common feature of Huntington's disease (HD) and could participate in disease onset and progression. However, little is known about the underlying causes of miRNA disruption in HD. We and others have previously shown that mutant Huntingtin binds to Ago2, a central component of miRNA biogenesis, and disrupts mature miRNA levels. In this study, we sought to determine if miRNA maturation per se was compromised in HD. Towards this end, we characterized major miRNA biogenesis pathway components and miRNA maturation products (pri-miRNA, pre-miRNA, and mature) in human HD (N = 41, Vonsattel grades HD2-4) and healthy control (N = 25) subjects. Notably, the striatum (putamen) and cortex (BA39) from the same individuals were analyzed in parallel. We show that Ago2, Drosha, and Dicer were strongly downregulated in human HD at the early stages of the disease. Using a panel of HD-related miRNAs (miR-10b, miR-196b, miR-132, miR-212, miR-127, miR-128), we uncovered various types of maturation defects in the HD brain, the most prominent occurring at the pre-miRNA to mature miRNA maturation step. Consistent with earlier findings, we provide evidence that alterations in autophagy could participate in miRNA maturation defects. Notably, most changes occurred in the striatum, which is more prone to HTT aggregation and neurodegeneration. Likewise, we observed no significant alterations in miRNA biogenesis in human HD cortex and blood, strengthening tissue-specific effects. Overall, these data provide important clues into the underlying mechanisms behind miRNA alterations in HD-susceptible tissues. Further investigations are now required to understand the biological, diagnostic, and therapeutic implications of miRNA/RNAi biogenesis defects in HD and related neurodegenerative disorders.

Retinal function anomalies in young offspring at genetic risk of schizophrenia and mood disorder: The meaning for the illness pathophysiology.

BACKGROUND: Visual defects are documented in psychiatric disorders such as schizophrenia, bipolar disorder and major depressive disorder. One of the most consistent alterations in patients is a change in cone and rod electroretinographic (ERG) responses. We previously showed a reduced rod b-wave amplitude in a small sample of young offspring born to an affected parent. A confirmation of the patients ERG anomalies in young offspring at high genetic risk would offer a new approach to the neurodevelopmental investigation of the illness. We thus investigated cone and rod responses in a larger sample of young healthy high-risk offspring. METHODS: The ERG was recorded in 99 offspring of patients having DMS-IV schizophrenia, bipolar or major depressive disorder (mean age 16.03; SD 6.14) and in 223 healthy controls balanced for sex and age. The a- and b-wave latency and amplitude of cones and rods were recorded. RESULTS: Cone b-wave latency was increased in offspring (ES = 0.31; P = 0.006) whereas rod b-wave amplitude was decreased (ES = -0.37; P = 0.001) and rod latency was increased (ES = 0.35; P = 0.002). CONCLUSIONS: The ERG rod and cone abnormal response previously reported in adult patients having schizophrenia, bipolar disorder or major depressive disorder are detectable in genetically high-risk offspring as early as in childhood and adolescence. Moreover, a gradient of effect sizes among offspring and the three adult diagnoses was found in the cone response. This suggests that ERG waveform as a risk endophenotype might become part of the definition of a "childhood risk syndrome".

Advances and Challenges in Understanding MicroRNA Function in Tauopathies: A Case Study of miR-132/212.

In the past decade, several groups have reported that microRNAs (miRNAs) can participate in the regulation of tau protein at different levels, including its expression, alternative splicing, phosphorylation, and aggregation. These observations are significant, since the abnormal regulation and deposition of tau is associated with nearly 30 neurodegenerative disorders. Interestingly, miRNA profiles go awry in tauopathies such as Alzheimer's disease, progressive supranuclear palsy, and frontotemporal dementia. Understanding the role and impact of miRNAs on tau biology could therefore provide important insights into disease risk, diagnostics, and perhaps therapeutics. In this Perspective article, we discuss recent advances in miRNA research related to tau. While proof-of-principle studies hold promise, physiological validation remains limited. To help fill this gap, we describe herein a pure tauopathy mouse model deficient for the miR-132/212 cluster. This miRNA family is strongly downregulated in human tauopathies and shown to regulate tau in vitro and in vivo. No significant differences in survival, motor deficits or body weight were observed in PS19 mice lacking miR-132/212. Age-specific effects were seen on tau expression and phosphorylation but not aggregation. Moreover, various miR-132/212 targets previously implicated in tau modulation were unaffected (GSK-3ß, Foxo3a, Mapk1, p300) or, unexpectedly, reduced (Mapk3, Foxo1, p300, Calpain 2) in miR-132/212-deficient PS19 mice. These observations highlight the challenges of miRNA research in living models, and current limitations of transgenic tau mouse models lacking functional miRNA binding sites. Based on these findings, we finally recommend different strategies to better understand the role of miRNAs in tau physiology and pathology.