Early and selective localization of tau filaments to glutamatergic subcellular domains within the human anterodorsal thalamus.

Widespread cortical accumulation of misfolded pathological tau proteins (ptau) in the form of paired helical filaments is a major hallmark of Alzheimer's disease. Subcellular localization of ptau at various stages of disease progression is likely to be informative of the cellular mechanisms involving its spread. Here, we found that the density of ptau within several distinct rostral thalamic nuclei in post-mortem human tissue (n = 25 cases) increased with the disease stage, with the anterodorsal nucleus (ADn) consistently being the most affected. In the ADn, ptau-positive elements were present already in the pre-cortical (Braak 0) stage. Tau pathology preferentially affected the calretinin-expressing subpopulation of glutamatergic neurons in the ADn. At the subcellular level, we detected ptau immunoreactivity in ADn cell bodies, dendrites, and in a specialized type of presynaptic terminal that expresses vesicular glutamate transporter 2 (vGLUT2) and likely originates from the mammillary body. The ptau-containing terminals displayed signs of degeneration, including endosomal/lysosomal organelles. In contrast, corticothalamic axon terminals lacked ptau. The data demonstrate the involvement of a specific cell population in ADn at the onset of the disease. The presence of ptau in subcortical glutamatergic presynaptic terminals supports hypotheses about the transsynaptic spread of tau selectively affecting specialized axonal pathways.

Neuropathologic Validation and Diagnostic Accuracy of Presynaptic Dopaminergic Imaging in the Diagnosis of Parkinsonism.

BACKGROUND AND OBJECTIVES: Degeneration of the presynaptic nigrostriatal dopaminergic system is one of the main biological features of Parkinson disease (PD), multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD), which can be measured using single-photon emission CT imaging for diagnostic purposes. Despite its widespread use in clinical practice and research, the diagnostic properties of presynaptic nigrostriatal dopaminergic (DAT) imaging in parkinsonism have never been evaluated against the diagnostic gold standard of neuropathology. The aim of this study was to evaluate the diagnostic parameters of DAT imaging compared with pathologic diagnosis in patients with parkinsonism. METHODS: Retrospective cohort study of patients with DAT imaging for the investigation of a clinically uncertain parkinsonism with brain donation between 2010 and 2021 to the Queen Square Brain Bank (London). Patients with DAT imaging for investigation of pure ataxia or dementia syndromes without parkinsonism were excluded. Those with a pathologic diagnosis of PD, MSA, PSP, or CBD were considered presynaptic dopaminergic parkinsonism, and other pathologies were considered postsynaptic for the analysis. DAT imaging was performed in routine clinical practice and visually classified by hospital nuclear medicine specialists as normal or abnormal. The results were correlated with neuropathologic diagnosis to calculate diagnostic accuracy parameters for the diagnosis of presynaptic dopaminergic parkinsonism. RESULTS: All of 47 patients with PD, 41 of 42 with MSA, 68 of 73 with PSP, and 6 of 10 with CBD (sensitivity 100%, 97.6%, 93.2%, and 60%, respectively) had abnormal presynaptic dopaminergic imaging. Eight of 17 patients with presumed postsynaptic parkinsonism had abnormal scans (specificity 52.9%). DISCUSSION: DAT imaging has very high sensitivity and negative predictive value for the diagnosis of presynaptic dopaminergic parkinsonism, particularly for PD. However, patients with CBD, and to a lesser extent PSP (of various phenotypes) and MSA (with predominant ataxia), can show normal DAT imaging. A range of other neurodegenerative disorders may have abnormal DAT scans with low specificity in the differential diagnosis of parkinsonism. DAT imaging is a useful diagnostic tool in the differential diagnosis of parkinsonism, although clinicians should be aware of its diagnostic properties and limitations. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that DAT imaging does not accurately distinguish between presynaptic dopaminergic parkinsonism and non-presynaptic dopaminergic parkinsonism.

Synaptopathy: presynaptic convergence in frontotemporal dementia and amyotrophic lateral sclerosis.

Frontotemporal dementia and amyotrophic lateral sclerosis are common forms of neurodegenerative disease that share overlapping genetics and pathologies. Crucially, no significantly disease-modifying treatments are available for either disease. Identifying the earliest changes that initiate neuronal dysfunction is important for designing effective intervention therapeutics. The genes mutated in genetic forms of frontotemporal dementia and amyotrophic lateral sclerosis have diverse cellular functions, and multiple disease mechanisms have been proposed for both. Identification of a convergent disease mechanism in frontotemporal dementia and amyotrophic lateral sclerosis would focus research for a targetable pathway, which could potentially effectively treat all forms of frontotemporal dementia and amyotrophic lateral sclerosis (both familial and sporadic). Synaptopathies are diseases resulting from physiological dysfunction of synapses, and define the earliest stages in multiple neuronal diseases, with synapse loss a key feature in dementia. At the presynapse, the process of synaptic vesicle recruitment, fusion and recycling is necessary for activity-dependent neurotransmitter release. The unique distal location of the presynaptic terminal means the tight spatio-temporal control of presynaptic homeostasis is dependent on efficient local protein translation and degradation. Recently, numerous publications have shown that mutations associated with frontotemporal dementia and amyotrophic lateral sclerosis present with synaptopathy characterized by presynaptic dysfunction. This review will describe the complex local signalling and membrane trafficking events that occur at the presynapse to facilitate neurotransmission and will summarize recent publications linking frontotemporal dementia/amyotrophic lateral sclerosis genetic mutations to presynaptic function. This evidence indicates that presynaptic synaptopathy is an early and convergent event in frontotemporal dementia and amyotrophic lateral sclerosis and illustrates the need for further research in this area, to identify potential therapeutic targets with the ability to impact this convergent pathomechanism.

Actualización en la patofisiología de la esquizofrenia desde la perspectiva de la neurociencia de sistemas / Update on the pathophysiology of schizophrenia from the systems neuroscience point of view

La patofisiología de la esquizofrenia (EQZ) sólo podrá entenderse en una aproximación integrativa, basada en la neurociencia de sistemas, para tratar de explicar cómo múltiples genes y neurotransmisores pueden actuar de manera sinérgica para producir el trastorno. En este trabajo se analizarán por separado los diversos endofenotipos de esta enfermedad para tratar de explicar, sobre la base de aproximaciones sistémicas, cómo ocurren los cambios en las interneuronas GABAérgicas en la EQZ, comenzando con la hipofunción GABAérgica y sus consecuencias sobre las neuronas piramidales corticales y la disfunción dopaminérgica a punto de origen hipocampal, lo que permite conciliar eventos neurobiológicos con sus consecuencias conductuales (consilience). Los circuitos involucrados por Lisman, Grace, Coyle, Green y otros autores en esta revisión integran las neurotransmisiones glutamatérgica, GABAérgica, dopaminérgica y colinérgica en un marco sistémico en que también se involucran factores de riesgo genético, para intentar demostrar sus acciones sinérgicas dentro del circuito y generar una aproximación desde la neurociencia de sistemas. Se intentará desarrollar estrategias de distinto orden para comprender la EQZ como enfermedad que produce sus consecuencias devastadoras a través de la acción sinérgica de genes y diversos neurotransmisores integrados en circuitos de procesamiento que operan en complejas dinámicas de tipo no-lineal.

Understanding the pathophysiology of schizophrenia (SZ) entails adopting a holistic approach based on systems neuroscience that allows to explain how multiple genes and neurotransmitters can act synergistically to trigger the disorder. In this article, the different endophenotypes of schizophrenia are analysed separaately, with the aim of explaining, by means of systemic approaches, how changes take place in GABAergic interneurons in SZ, starting from the GABAergic hypofunction and ists effects on cortical pyramidal neurons, as well as on the dopaminergic dysfunction at he pont of origin of the hippocampus, which enables to reconcile neurobiological events with their behavioural consequences ("consilience"). The circuits proposed by Lisman, Grace, Coyle, Green and other authors, that make up glutamatergic, GABAerci, dopaminergic and cholinergic neurotransmissions embedded in a systemic framework in whic genetic risk factors are also involved, are included in this review to demonstrate their synergistic actions within the circuit, as well as to develop an approach based on systems neuroscience. The present article will also provide different types of strategies intended to understand SZ as a disease that causes its devastating effects through the synergistic action of genes and the different neurotransmitters organized in processing circuits that operte in complex non-linear dynamics.

Actualización en la patofisiología de la esquizofrenia desde la perspectiva de la neurociencia de sistemas / Update on the pathophysiology of schizophrenia from the systems neuroscience point of view

La patofisiología de la esquizofrenia (EQZ) sólo podrá entenderse en una aproximación integrativa, basada en la neurociencia de sistemas, para tratar de explicar cómo múltiples genes y neurotransmisores pueden actuar de manera sinérgica para producir el trastorno. En este trabajo se analizarán por separado los diversos endofenotipos de esta enfermedad para tratar de explicar, sobre la base de aproximaciones sistémicas, cómo ocurren los cambios en las interneuronas GABAérgicas en la EQZ, comenzando con la hipofunción GABAérgica y sus consecuencias sobre las neuronas piramidales corticales y la disfunción dopaminérgica a punto de origen hipocampal, lo que permite conciliar eventos neurobiológicos con sus consecuencias conductuales (consilience). Los circuitos involucrados por Lisman, Grace, Coyle, Green y otros autores en esta revisión integran las neurotransmisiones glutamatérgica, GABAérgica, dopaminérgica y colinérgica en un marco sistémico en que también se involucran factores de riesgo genético, para intentar demostrar sus acciones sinérgicas dentro del circuito y generar una aproximación desde la neurociencia de sistemas. Se intentará desarrollar estrategias de distinto orden para comprender la EQZ como enfermedad que produce sus consecuencias devastadoras a través de la acción sinérgica de genes y diversos neurotransmisores integrados en circuitos de procesamiento que operan en complejas dinámicas de tipo no-lineal.(AU)

Understanding the pathophysiology of schizophrenia (SZ) entails adopting a holistic approach based on systems neuroscience that allows to explain how multiple genes and neurotransmitters can act synergistically to trigger the disorder. In this article, the different endophenotypes of schizophrenia are analysed separaately, with the aim of explaining, by means of systemic approaches, how changes take place in GABAergic interneurons in SZ, starting from the GABAergic hypofunction and ists effects on cortical pyramidal neurons, as well as on the dopaminergic dysfunction at he pont of origin of the hippocampus, which enables to reconcile neurobiological events with their behavioural consequences ("consilience"). The circuits proposed by Lisman, Grace, Coyle, Green and other authors, that make up glutamatergic, GABAerci, dopaminergic and cholinergic neurotransmissions embedded in a systemic framework in whic genetic risk factors are also involved, are included in this review to demonstrate their synergistic actions within the circuit, as well as to develop an approach based on systems neuroscience. The present article will also provide different types of strategies intended to understand SZ as a disease that causes its devastating effects through the synergistic action of genes and the different neurotransmitters organized in processing circuits that operte in complex non-linear dynamics.(AU)