Deep Cerebellar Neurons Research Articles

The cerebellum computes frequency dynamics for motions with numerical precision and cross-individual uniformity.

Cross-individual variability is considered the essence of biology, preventing precise mathematical descriptions of biological motion1-7 like the physics law of motion. Here we report that the cerebellum shapes motor kinematics by encoding dynamic motor frequencies with remarkable numerical precision and cross-individual uniformity. Using in-vivo electrophysiology and optogenetics in mice, we confirmed that deep cerebellar neurons encoded frequencies via populational tuning of neuronal firing probabilities, creating cerebellar oscillations and motions with matched frequencies. The mechanism was consistently presented in self-generated rhythmic and non-rhythmic motions triggered by a vibrational platform, or skilled tongue movements of licking in all tested mice with cross-individual uniformity. The precision and uniformity allowed us to engineer complex motor kinematics with designed frequencies. We further validated the frequency-coding function of the human cerebellum using cerebellar electroencephalography recordings and alternating-current stimulation during voluntary tapping tasks. Our findings reveal a cerebellar algorithm for motor kinematics with precision and uniformity, the mathematical foundation for brain-computer interface for motor control.

Electrophysiological alterations of the Purkinje cells and deep cerebellar neurons in a mouse model of Alzheimer disease (electrophysiology on cerebellum of AD mice).

Alzheimer's disease is histopathologically well defined by the presence of amyloid deposits and tau-related neurofibrillary tangles in crucial regions of the brain. Interest is growing in revealing and determining possible pathological markers also in the cerebellum as its involvement in cognitive functions is now well supported. Despite the central position of the Purkinje cell in the cerebellum, its electrophysiological behaviour in mouse models of Alzheimer's disease is scarce in the literature. Our first aim was here to focus on the electrophysiological behaviour of the cerebellum in awake mouse model of Alzheimer's disease (APPswe/PSEN1dE9) and the related performance on the water-maze test classically used in behavioural studies. We found prevalent signs of electrophysiological alterations in both Purkinje cells and deep cerebellar nuclei neurons which might explain the behavioural deficits reported during the water-maze test. The alterations of neurons firing were accompanied by a dual (~16 and ~228 Hz) local field potential's oscillation in the Purkinje cell layer of Alzheimer's disease mice which was concomitant to an important increase of both the simple and the complex spikes. In addition, β-amyloid deposits were present in the molecular layer of the cerebellum. These results highlight the importance of the output firing modification of the AD cerebellum that may indirectly impact the activity of its subcortical and cortical targets.

Is essential tremor a disorder of GABA dysfunction? No.

Although essential tremor is common, its underlying pathophysiology remains uncertain, and several hypotheses seek to explain the tremor mechanism. The GABA hypothesis states that disinhibition of deep cerebellar neurons due to reduced GABAergic input from Purkinje cells results in increased pacemaker activity, leading to rhythmic output to the thalamo-cortical circuit and resulting in tremor. However, some neuroimaging, spectroscopy, and pathology studies have not shown a clear or consistent GABA deficiency in essential tremor, and animal models have indicated that large reductions of Purkinje cell inhibition may improve tremor. Instead, tremor is increasingly attributable to dysfunction in oscillating networks, where altered (but not necessarily reduced) inhibitory signaling can result in tremor. Hypersynchrony of Purkinje cell activity may account for excessive oscillatory cerebellar output, with potential contributions along multiple sites of the olivocerebellar loop. Although older animal tremor models, such as harmaline tremor, have explored contributions from the inferior olivary body, increasing evidence has pointed to the role of aberrant climbing fiber synaptic organization in oscillatory cerebellar activity and tremor generation. New animal models such as hotfoot17j mice, which exhibit abnormal climbing fiber organization due to mutations in Grid2, have recapitulated many features of ET. Similar abnormal climbing fiber architecture and excessive cerebellar oscillations as measured by EEG have been found in humans with essential tremor. Further understanding of hypersynchrony and excessive oscillatory activity in ET phenotypes may lead to more targeted and effective treatment options.

Transcranial direct current stimulation of cerebellum alters spiking precision in cerebellar cortex: A modeling study of cellular responses.

Transcranial direct current stimulation (tDCS) of the cerebellum has rapidly raised interest but the effects of tDCS on cerebellar neurons remain unclear. Assessing the cellular response to tDCS is challenging because of the uneven, highly stratified cytoarchitecture of the cerebellum, within which cellular morphologies, physiological properties, and function vary largely across several types of neurons. In this study, we combine MRI-based segmentation of the cerebellum and a finite element model of the tDCS-induced electric field (EF) inside the cerebellum to determine the field imposed on the cerebellar neurons throughout the region. We then pair the EF with multicompartment models of the Purkinje cell (PC), deep cerebellar neuron (DCN), and granule cell (GrC) and quantify the acute response of these neurons under various orientations, physiological conditions, and sequences of presynaptic stimuli. We show that cerebellar tDCS significantly modulates the postsynaptic spiking precision of the PC, which is expressed as a change in the spike count and timing in response to presynaptic stimuli. tDCS has modest effects, instead, on the PC tonic firing at rest and on the postsynaptic activity of DCN and GrC. In Purkinje cells, anodal tDCS shortens the repolarization phase following complex spikes (-14.7 ± 6.5% of baseline value, mean ± S.D.; max: -22.7%) and promotes burstiness with longer bursts compared to resting conditions. Cathodal tDCS, instead, promotes irregular spiking by enhancing somatic excitability and significantly prolongs the repolarization after complex spikes compared to baseline (+37.0 ± 28.9%, mean ± S.D.; max: +84.3%). tDCS-induced changes to the repolarization phase and firing pattern exceed 10% of the baseline values in Purkinje cells covering up to 20% of the cerebellar cortex, with the effects being distributed along the EF direction and concentrated in the area under the electrode over the cerebellum. Altogether, the acute effects of tDCS on cerebellum mainly focus on Purkinje cells and modulate the precision of the response to synaptic stimuli, thus having the largest impact when the cerebellar cortex is active. Since the spatiotemporal precision of the PC spiking is critical to learning and coordination, our results suggest cerebellar tDCS as a viable therapeutic option for disorders involving cerebellar hyperactivity such as ataxia.

Mapping mesoscale axonal projections in the mouse brain using a 3D convolutional network

The projection targets of a neuronal population are a key feature of its anatomical characteristics. Historically, tissue sectioning, confocal microscopy, and manual scoring of specific regions of interest have been used to generate coarse summaries of mesoscale projectomes. We present here TrailMap, a three-dimensional (3D) convolutional network for extracting axonal projections from intact cleared mouse brains imaged by light-sheet microscopy. TrailMap allows region-based quantification of total axon content in large and complex 3D structures after registration to a standard reference atlas. The identification of axonal structures as thin as one voxel benefits from data augmentation but also requires a loss function that tolerates errors in annotation. A network trained with volumes of serotonergic axons in all major brain regions can be generalized to map and quantify axons from thalamocortical, deep cerebellar, and cortical projection neurons, validating transfer learning as a tool to adapt the model to novel categories of axonal morphology. Speed of training, ease of use, and accuracy improve over existing tools without a need for specialized computing hardware. Given the recent emphasis on genetically and functionally defining cell types in neural circuit analysis, TrailMap will facilitate automated extraction and quantification of axons from these specific cell types at the scale of the entire mouse brain, an essential component of deciphering their connectivity.

Maturation of Human Pluripotent Stem Cell-Derived Cerebellar Neurons in the Absence of Co-culture

The cerebellum plays a critical role in all vertebrates, and many neurological disorders are associated with cerebellum dysfunction. A major limitation in cerebellar research has been the lack of adequate disease models. As an alternative to animal models, cerebellar neurons differentiated from pluripotent stem cells have been used. However, previous studies only produced limited amounts of Purkinje cells. Moreover, in vitro generation of Purkinje cells required co-culture systems, which may introduce unknown components to the system. Here we describe a novel differentiation strategy that uses defined medium to generate Purkinje cells, granule cells, interneurons, and deep cerebellar nuclei projection neurons, that self-formed and differentiated into electrically active cells. Using a defined basal medium optimized for neuronal cell culture, we successfully promoted the differentiation of cerebellar precursors without the need for co-culturing. We anticipate that our findings may help developing better models for the study of cerebellar dysfunctions, while providing an advance toward the development of autologous replacement strategies for treating cerebellar degenerative diseases.

Beta-gamma burst stimulations of the inferior olive induce high-frequency oscillations in the deep cerebellar nuclei.

The cerebellum displays various sorts of rhythmic activities covering both low- and high-frequency oscillations. These cerebellar high-frequency oscillations were observed in the cerebellar cortex. Here, we hypothesised that not only is the cerebellar cortex a generator of high-frequency oscillations but also that the deep cerebellar nuclei may also play a similar role. Thus, we analysed local field potentials and single-unit activities in the deep cerebellar nuclei before, during and after electric stimulation in the inferior olive of awake mice. A high-frequency oscillation of 350Hz triggered by the stimulation of the inferior olive, within the beta-gamma range, was observed in the deep cerebellar nuclei. The amplitude and frequency of the oscillation were independent of the frequency of stimulation. This oscillation emerged during the period of stimulation and persisted after the end of the stimulation. The oscillation coincided with the inhibition of deep cerebellar neurons. As the inhibition of the deep cerebellar nuclei is related to inhibitory inputs from Purkinje cells, we speculate that the oscillation represents the unmasking of the synchronous activation of another subtype of deep cerebellar neuronal subtype, devoid of GABA receptors and under the direct control of the climbing fibres from the inferior olive. Still, the mechanism sustaining this oscillation remains to be deciphered. Our study sheds new light on the role of the olivo-cerebellar loop as the final output control of the intercerebellar circuitry.

Role of Rostral Fastigial Neurons in Encoding a Body-Centered Representation of Translation in Three Dimensions.

Many daily behaviors rely critically on estimates of our body motion. Such estimates must be computed by combining neck proprioceptive signals with vestibular signals that have been transformed from a head- to a body-centered reference frame. Recent studies showed that deep cerebellar neurons in the rostral fastigial nucleus (rFN) reflect these computations, but whether they explicitly encode estimates of body motion remains unclear. A key limitation in addressing this question is that, to date, cell tuning properties have only been characterized for a restricted set of motions across head-re-body orientations in the horizontal plane. Here we examined, for the first time, how 3D spatiotemporal tuning for translational motion varies with head-re-body orientation in both horizontal and vertical planes in the rFN of male macaques. While vestibular coding was profoundly influenced by head-re-body position in both planes, neurons typically reflected at most a partial transformation. However, their tuning shifts were not random but followed the specific spatial trajectories predicted for a 3D transformation. We show that these properties facilitate the linear decoding of fully body-centered motion representations in 3D with a broad range of temporal characteristics from small groups of 5-7 cells. These results demonstrate that the vestibular reference frame transformation required to compute body motion is indeed encoded by cerebellar neurons. We propose that maintaining partially transformed rFN responses with different spatiotemporal properties facilitates the creation of downstream body motion representations with a range of dynamic characteristics, consistent with the functional requirements for tasks such as postural control and reaching.SIGNIFICANCE STATEMENT Estimates of body motion are essential for many daily activities. Vestibular signals are important contributors to such estimates but must be transformed from a head- to a body-centered reference frame. Here, we provide the first direct demonstration that the cerebellum computes this transformation fully in 3D. We show that the output of these computations is reflected in the tuning properties of deep cerebellar rostral fastigial nucleus neurons in a specific distributed fashion that facilitates the efficient creation of body-centered translation estimates with a broad range of temporal properties (i.e., from acceleration to position). These findings support an important role for the rostral fastigial nucleus as a source of body translation estimates functionally relevant for behaviors ranging from postural control to perception.

The Temporal Contribution of the Gbx2 Lineage to Cerebellar Neurons.

The cerebellum (Cb) is an exquisite structure that controls elaborate motor behaviors and is essential for sensory-motor learning. During development, the Cb is derived from rhombomere 1 (r1). Within this embryonic compartment, precursors in r1 are patterned by signaling cues originating from the isthmus organizer (IsO) and subsequently undergo complex morphogenic movements to establish their final position in the mature Cb. The transcription factor Gbx2 is expressed in the developing Cb and is intimately involved in organizing and patterning the Cb. Nevertheless, how precursors expressing Gbx2 at specific embryonic time points contribute to distinct cell types in the adult Cb is unresolved. In this study, we used Genetic Inducible Fate Mapping (GIFM) to mark Gbx2-expressing precursors with fine temporal resolution and to subsequently track this lineage through embryogenesis. We then determined the terminal neuronal fate of the Gbx2 lineage in the adult Cb. Our analysis demonstrates that the Gbx2 lineage contributes to the Cb with marking over the course of five stages: Embryonic day 7.5 (E7.5) through E11.5. The Gbx2 lineage gives rise to Purkinje cells, granule neurons, and deep cerebellar neurons across these marking stages. Notably, the contribution of the Gbx2 lineage shifts as development proceeds with each marking stage producing a distinct profile of mature neurons in the adult Cb. These findings demonstrate the relationship between the temporal expression of Gbx2 and the terminal cell fate of neurons in the Cb. Based on these results, Gbx2 is critical to Cb development, not only for its well-defined role in positioning and maintaining the IsO, but also for guiding the development of Cb precursors and determining the identity of Cb neurons.

The cerebellum on cocaine: plasticity and metaplasticity

Despite the fact that several data have supported the involvement of the cerebellum in the functional alterations observed after prolonged cocaine use, this brain structure has been traditionally ignored and excluded from the circuitry affected by addictive drugs. In the present study, we investigated the effects of a chronic cocaine treatment on molecular and structural plasticity in the cerebellum, including BDNF, D3 dopamine receptors, ΔFosB, the Glu2 AMPA receptor subunit, structural modifications in Purkinje neurons and, finally, the evaluation of perineuronal nets (PNNs) in the projection neurons of the medial nucleus, the output of the cerebellar vermis. In the current experimental conditions in which repeated cocaine treatment was followed by a 1-week withdrawal period and a new cocaine challenge, our results showed that cocaine induced a large increase in cerebellar proBDNF levels and its expression in Purkinje neurons, with the mature BDNF expression remaining unchanged. Together with this, cocaine-treated mice exhibited a substantial enhancement of D3 receptor levels. Both ΔFosB and AMPA receptor Glu2 subunit expressions were enhanced in cocaine-treated animals. Significant pruning in Purkinje dendrite arborization and reduction in the size and density of Purkinje boutons contacting deep cerebellar projection neurons accompanied cocaine-dependent increase in proBDNF. Cocaine-associated effects point to the inhibitory Purkinje function impairment, as was evidenced by lower activity in these cells. Moreover, the probability of any remodelling in Purkinje synapses appears to be decreased due to an upregulation of extracellular matrix components in the PNNs surrounding the medial nuclear neurons.

The GABA Hypothesis in Essential Tremor: Lights and Shadows.

BackgroundThe gamma-aminobutyric acid (GABA) hypothesis in essential tremor (ET) implies a disturbance of the GABAergic system, especially involving the cerebellum. This review examines the evidence of the GABA hypothesis.MethodsThe review is based on published data about GABA dysfunction in ET, taking into account studies on cerebrospinal fluid, pathology, electrophysiology, genetics, neuroimaging, experimental animal models, and human drug therapies.ResultsFindings from several studies support the GABA hypothesis in ET. The hypothesis follows four steps: 1) cerebellar neurodegeneration with Purkinje cell loss; 2) a decrease in GABA system activity in deep cerebellar neurons; 3) disinhibition in output deep cerebellar neurons with pacemaker activity; and 4) an increase in rhythmic activity of the thalamus and thalamo-cortical circuit, contributing to the generation of tremor. Doubts have been cast on this hypothesis, however, by the fact that it is based on relatively few works, controversial post-mortem findings, and negative genetic studies on the GABA system. Furthermore, GABAergic drug efficacy is low and some GABAergic drugs do not have antitremoric efficacy.DiscussionThe GABA hypothesis continues to be the most robust pathophysiological hypothesis to explain ET. There is light in all GABA hypothesis steps, but a number of shadows cannot be overlooked. We need more studies to clarify the neurodegenerative nature of the disease, to confirm the decrease of GABA activity in the cerebellum, and to test more therapies that enhance the GABA transmission specifically in the cerebellum area.

Corrigenda

The Journal of PhysiologyVolume 591, Issue 13 p. 3451-3451 Free Access Corrigenda This article corrects the following: Distinct roles for IT and IH in controlling the frequency and timing of rebound spike responses Jordan D. T. Engbers, Dustin Anderson, Reza Tadayonnejad, W. Hamish Mehaffey, Michael L. Molineux, Ray W. Turner, Volume 589Issue 22The Journal of Physiology pages: 5391-5413 First Published online: November 14, 2011 First published: 08 May 2013 https://doi.org/10.1113/jphysiol.2013.257030AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat In the article by Engbers et al. (2011), there were typographical errors in one equation and two parameters used in a model of deep cerebellar neurons. In the Methods section entitled Modelling, the equation should read: Slow K+ activation Finally, the correct values for gKd and gCa are: gKd= 25 mS cm-2 and gCa= 4.25 mS cm-2. Reference Engbers JDT , Anderson D , Tadayonnejad R , Mehaffey WH , Molineux ML & Turner RW ( 2011 ). Distinct roles for IT and IH in controlling the frequency and timing of rebound spike responses . J Physiol 589 , 5391 – 5413 . Volume591, Issue13July 2013Pages 3451-3451 ReferencesRelatedInformation

Monitoring Performance Degradation of Cerebellar Functions Using Computational Neuroscience Methods: Implications on Neurological Diseases

Neurodegeneration is a major cause of human disease. Within the cerebellum, neuronal degeneration and/or dysfunction has been associated with many diseases, including several forms of cerebellar ataxia, since normal cerebellar function is paramount for proper motor coordination, balance, and motor learning. The cerebellum represents a well-established neural circuit. Determining the effects of neuronal loss is of great importance for understanding the fundamental workings of the cerebellum and disease-associated dysfunctions. This paper presents computational modeling of cerebellar function in relation to neurodegeneration either affecting a specific cerebellar cell type, such as granule cells or Purkinje cells, or more generally affecting cerebellar cells and the implications on effects in relation to performance degradation throughout the progression of cell death. The results of the models show that the overall number of cells, as a percentage of the total cell number in the model, of a particular type and, primarily, their proximity to the circuit output, and not the neuronal convergence due to the relative number of cells of a particular type, is the main indicator of the gravity of the functional deficit caused by the degradation of that cell type. Specifically, the greater the percentage loss of neurons of a specific type and the closer proximity of those cells to the deep cerebellar neurons, the greater the deficit caused by the neuronal cell loss. These findings contribute to the understanding of the functional consequences of neurodegeneration and the functional importance of specific connectivity within a neuronal circuit.

Spatio-temporal expression pattern of the NatB complex, Nat5/Mdm20 in the developing mouse brain: Implications for co-operative versus non-co-operative actions of Mdm20 and Nat5

The NatB complex, Nat5/Mdm20 acetyltransferase mediates N-acetylation to control cell cycle progression and actin dynamics in yeast. As yet, little is known about the expression pattern of Mdm20 and Nat5 in multi-cellular organisms. Here we show that Mdm20 is highly expressed in mouse embryonic brain. At E11.5, Mdm20 was widely expressed in both neural progenitors and early differentiating neurons, whereas Nat5 was expressed in Sox1/3+/Mdm20+ neural progenitors. By E14.5, both Mdm20 and Nat5 were downregulated in most ventricular zone neural progenitors, whereas both proteins were found in differentiating neurons and co-expression was maintained at E18.5 in derivatives of these cells, such as midbrain dopaminergic (DA) neurons and septal neurons. These data suggest that Nat5/Mdm20 complex-mediated acetylation may play a role in the proliferation and differentiation of neural progenitors. Intriguingly, our data also showed that Mdm20 is not always co-expressed with Nat5 in all differentiated neurons, for example deep cerebellar neurons. Moreover, detailed examination of the subcellular localization of Mdm20 and Nat5 in cultured Nat5+/Mdm20+ midbrain DA neurons revealed that Mdm20 is also not necessarily co-localized with Nat5 within neurons. Given that Nat5 is only a known member of Nat family protein that interacts with Mdm20, our data imply that Mdm20 may function either with an unidentified Nat protein partner(s) or possibly in a Nat-independent manner.

Genes expressed in Atoh1 neuronal lineages arising from the r1/isthmus rhombic lip

During embryogenesis, the rhombic lip of the fourth ventricle is the germinal origin of a diverse collection of neuronal populations that ultimately reside in the brainstem and cerebellum. Rhombic lip neurogenesis requires the bHLH transcription factor Atoh1 (Math1), and commences shortly after neural tube closure (E9.5). Within the rhombomere 1 – isthmus region, the rhombic lip first produces brainstem and deep cerebellar neurons (E9.5–E12), followed by granule cell precursors after E12. While Atoh1 function is essential for all of these populations to be specified, the downstream genetic programs that confer specific properties to early and late born Atoh1 lineages are not well characterized. We have performed a comparative microarray analysis of gene expression within early and later born cohorts of Atoh1 expressing neural precursors purified from E14.5 embryos using a transgenic labeling strategy. We identify novel transcription factors, cell surface molecules, and cell cycle regulators within each pool of Atoh1 lineages that likely contribute to their distinct developmental trajectories and cell fates. In particular, our analysis reveals new insights into the genetic programs that regulate the specification and proliferation of granule cell precursors, the putative cell of origin for the majority of medulloblastomas.

The Ca2+ Channel β4c Subunit Interacts with Heterochromatin Protein 1 via a PXVXL Binding Motif

The β subunits of voltage-gated Ca(2+) channels are best known for their roles in regulating surface expression and gating of voltage-gated Ca(2+) channel α(1) subunits. Recent evidence, however, indicates that these proteins have a variety of Ca(2+) channel-independent functions. For example, on the molecular level, they regulate gene expression, and on the whole animal level, they regulate early cell movements in zebrafish development. In the present study, an alternatively spliced, truncated β4 subunit (β4c) is identified in the human brain and shown to be highly expressed in nuclei of vestibular neurons. Pull-down assays, nuclear magnetic resonance, and isothermal titration calorimetry demonstrate that the protein interacts with the chromo shadow domain (CSD) of heterochromatin protein 1γ. Site-directed mutagenesis reveals that the primary CSD interaction occurs through a β4c C-terminal PXVXL consensus motif, adding the β4c subunit to a growing PXVXL protein family with epigenetic responsibilities. These proteins have multiple nuclear functions, including transcription regulation (TIF1α) and nucleosome assembly (CAF1). An NMR-based two-site docking model of β4c in complex with dimerized CSD is presented. Possible roles for the interaction are discussed.

The UNC5C Netrin Receptor Regulates Dorsal Guidance of Mouse Hindbrain Axons

The cerebellum receives its input from multiple precerebellar nuclei located in the brainstem and sends processed information to other brain structures via the deep cerebellar neurons. Guidance molecules that regulate the complex migrations of precerebellar neurons and the initial guidance of their leading processes have been identified. However, the molecules necessary for dorsal guidance of precerebellar axons to the developing cerebellum or for guidance of decussating axons of the deep nuclei are not known. To determine whether Unc5c plays a role in the dorsal guidance of precerebellar and deep cerebellar axons, we studied axonal trajectories of these neurons in Unc5c(-/-) mice. Our results show that Unc5c is expressed broadly in the precerebellar and deep cerebellar neurons. Unc5c deletion disrupted long-range dorsal guidance of inferior olivary and pontine axons after crossing the midline. In addition, dorsal guidance of the axons from the medial deep cerebellar and external cuneate neurons was affected in Unc5c(-/-) mice, as were anterior migrations of pontine neurons. Coincident with the guidance defects of their axons, degeneration of neurons in the external cuneate nucleus and subdivisions of the inferior olivary nucleus was observed in Unc5c(-/-) mice. Lastly, transgenic expression of Unc5c in deep neurons and pontine neurons by the Atoh1 promoter rescued defects of the medial deep cerebellar and pontine axons observed in Unc5c(-/-) embryos, demonstrating that Unc5c acts cell autonomously in the guidance of these axons. Our results suggest that Unc5c plays a broad role in dorsal guidance of axons in the developing hindbrain.

Antineuronal autoantibodies in paraneoplastic cerebellar degeneration associated with adenocarcinoma of the prostate

Paraneoplastic neurological syndromes are unusual in prostatic cancer, and paraneoplastic cerebellar degeneration associated with adenocarcinoma of the prostate is rare. Here we report a 68 year old man who developed progressive ataxia in the setting of stage D2 adenocarcinoma of the prostate and whose MRI showed cerebellar atrophy. The patient's serum produced a previously undescribed pattern of immunoreactivity, binding to nuclei and cytoplasm of Purkinje cells, deep cerebellar neurons, scattered cells in the molecular and granule cell layers, and neuronal populations in thalamus, cerebral cortex, and hippocampus but not with liver or kidney. The patient's IgG also labeled a 65 kDa protein, discrete from Yo antigen, in Western blots of Purkinje cell lysates and did not react with blotted recombinant HuD, Ri, Yo, or amphiphysin proteins. Sera from neurologically normal patients with adenocarcinoma of the prostate did not contain this antibody, and the patient's serum did not react with normal prostate or with prostatic adenocarcinomas from other individuals. Prostatic adenocarcinoma may occasionally be accompanied by development of anticerebellar antibodies. Adenocarcinoma of the prostate should be considered as a possible underlying malignancy in older males with unexplained progressive cerebellar degeneration.

Purkinje cells originate from cerebellar ventricular zone progenitors positive for Neph3 and E-cadherin

GABAergic Purkinje cells (PCs) provide the primary output from the cerebellar cortex, which controls movement and posture. Although the mechanisms of PC differentiation have been well studied, the precise origin and initial specification mechanism of PCs remain to be clarified. Here, we identified a cerebellar and spinal cord GABAergic progenitor-selective cell surface marker, Neph3, which is a direct downstream target gene of Ptf1a, an essential regulator of GABAergic neuron development. Using FACS, Neph3(+) GABAergic progenitors were sorted from the embryonic cerebellum, and the cell fate of this population was mapped by culturing in vitro. We found that most of the Neph3(+) populations sorted from the mouse E12.5 cerebellum were fated to differentiate into PCs while the remaining small fraction of Neph3(+) cells were progenitors for Pax2(+) interneurons, which are likely to be deep cerebellar nuclei GABAergic neurons. These results were confirmed by short-term in vivo lineage-tracing experiments using transgenic mice expressing Neph3 promoter-driven GFP. In addition, we identified E-cadherin as a marker selectively expressed by a dorsally localized subset of cerebellar Neph3(+) cells. Sorting experiments revealed that the Neph3(+) E-cadherin(high) population in the embryonic cerebellum defined PC progenitors while progenitors for Pax2(+) interneurons were enriched in the Neph3(+) E-cadherin(low) population. Taken together, our results identify two spatially demarcated subregions that generate distinct cerebellar GABAergic subtypes and reveal the origin of PCs in the ventricular zone of the cerebellar primordium.

Reliability of triggering postinhibitory rebound bursts in deep cerebellar neurons

Deep cerebellar nuclear (DCN) neurons exhibit distinct phenotypes of rebound discharge following current-evoked membrane hyperpolarizations that arise from specific CaV3 T-type Ca2+ channel isoforms and Ca2+-activated K+ channels. The probability of evoking rebound bursts following a brief train of GABAergic inhibitory synaptic input from cerebellar Purkinje cells was recently questioned for stimulus intensities adjusted to evoke a long post-stimulus pause in spike firing. We revisited this issue to examine the potential for generating rebound bursts in DCN cells in response to synaptic inputs in vitro. Both a Transient and Weak Burst phenotype could be distinguished in on-cell extracellular recordings or whole-cell recordings in response to inhibitory synaptic input. We found that the rebound burst response was a sensitive function of stimulus intensity, such that increasing stimulus intensity significantly raised the probability for evoking bursts while decreasing pause duration. The threshold for reliably generating rebound bursts was ~40 percent of maximum intensity, a level that evokes an IPSC corresponding to only a small number of the inhibitory terminals known to impinge on DCN cells. The probability for evoking rebound bursts is thus very high for moderate levels of stimulation in vitro, leaving the potential role for rebound discharge to contribute to signal processing in vivo an open question.