Association between physical exercise, executive function, and cerebellar cortex: A cross-sectional study among the elderly in Chinese communities

Background

Previous studies have confirmed that physical exercise may be beneficial for brain health, but there is little data on this among older Chinese.

Objective

The purpose of this study was to explore the relationship between physical exercise and cognitive impairment, and to explore the possible mechanism by which physical exercise prevents cognitive decline.

Materials and methods

192 older adults with dementia, 610 older adults with mild cognitive impairment (MCI), and 2,218 healthy older adults were included in the study. Through standardized questionnaires, we obtained their general demographic information (such as gender, age, education, etc.), disease-related information (hypertension and diabetes) and physical exercise information (such as whether they did physical exercise and the frequency of physical exercise, etc.). The mini-mental state examination (MMSE) and Montreal Cognitive Assessment (MoCA) were used to assess their overall cognitive function, while the Wechsler block diagram was used to assess their executive function. Moreover, 164 healthy, randomly selected older adults also underwent brain MRI scans at the same time, and the target brain regions included hippocampus, gray matter, and cerebellar cortex.

Results

By using stepwise multiple logistics regression analysis, we found that physical exercise was associated with both MCI (p = 0.001*, OR = 0.689, 95%CI: 0.553–0.859) and dementia (p < 0.001*, OR = 0.501, 95%CI: 0.354–0.709), independent of gender, age, education, and other factors. The results of ROC curve showed that the area under the curve of physical exercise in predicting MCI and dementia was 0.551 (p < 0.001*, 95%CI: 0.525–0.577) and 0.628 (p = 0.001*, 95%CI: 0.585–0.671), respectively. The results of partial correlation analysis showed that physical exercise was associated with left cerebellar cortex (r = 0.163, p = 0.023), right cerebellar cortex (r = 0.175, p = 0.015) and Wechsler block diagram score (r = 0.235, p = 0.011). Moreover, the results of linear regression analysis mediation model showed that physical exercise may affect Wechsler block diagram score through influencing the thickness of right cerebellum cortex, and the latter may play a partial mediation effect (indirect B = 0.001, p = 0.045).

Conclusion

Physical exercise might be a protective factor for mild cognitive impairment and dementia among the Chinese elderly, and there might be an association among physical exercise, executive function, and the thickness of the cerebellar cortex.

Pretecto- and ponto-cerebellar pathways to the pigeon oculomotor cerebellum follow a zonal organization

Both birds and mammals have relatively large forebrains and cerebella. In mammals, there are extensive sensory-motor projections to the cerebellum through the pontine nuclei originating from several parts of the cerebral cortex. Similar forebrain-to-cerebellum pathways exist in birds, but the organization of this circuitry has not been studied extensively. Birds have two nuclei at the base of the brainstem that are thought to be homologous to the pontine nuclei of mammals, the medial and lateral pontine nuclei (PM, PL). Additionally, birds are unique in that they have a pretectal nucleus called the medial spiriform nucleus (SpM) that, like the pontine nuclei, also receives projections from the forebrain and projects to the oculomotor cerebellum (OCb; folia VI to VIII). The OCb also receives input from the pretectal nucleus lentiformis mesencephali (LM), which analyzes visual optic flow information resulting from self-movement. In this study, we used single or double injections of fluorescent tracers to study the organization of these inputs from PM, PL, SpM and LM to the OCb in pigeons. We found that these inputs follow a zonal organization. The most medial zone in the OCb, zone A1, receives bilateral inputs from the lateral SpM, PL and LM. Zones A2 and C receive a bilateral projection from the medial SpM, and a mostly contralateral projection from PM and LM. We discuss how the pathway to zone A1 processes mainly visuo-motor information to spinal premotor areas, whereas the pathways to zone A2/C processes somato-motor and visuo-motor information and may have a feedback/modulatory role.

Differential spatiotemporal development of Purkinje cell populations and cerebellum-dependent sensorimotor behaviors

Distinct populations of Purkinje cells (PCs) with unique molecular and connectivity features are at the core of the modular organization of the cerebellum. Previously, we showed that firing activity of PCs differs between ZebrinII-positive and ZebrinII-negative cerebellar modules (Zhou et al., 2014; Wu et al., 2019). Here, we investigate the timing and extent of PC differentiation during development in mice. We found that several features of PCs, including activity levels, dendritic arborization, axonal shape and climbing fiber input, develop differentially between nodular and anterior PC populations. Although all PCs show a particularly rapid development in the second postnatal week, anterior PCs typically have a prolonged physiological and dendritic maturation. In line herewith, younger mice exhibit attenuated anterior-dependent eyeblink conditioning, but faster nodular-dependent compensatory eye movement adaptation. Our results indicate that specific cerebellar regions have unique developmental timelines which match with their related, specific forms of cerebellum-dependent behaviors.

Purkinje cell neurotransmission patterns cerebellar basket cells into zonal modules defined by distinct pinceau sizes

Ramón y Cajal proclaimed the neuron doctrine based on circuit features he exemplified using cerebellar basket cell projections. Basket cells form dense inhibitory plexuses that wrap Purkinje cell somata and terminate as pinceaux at the initial segment of axons. Here, we demonstrate that HCN1, Kv1.1, PSD95 and GAD67 unexpectedly mark patterns of basket cell pinceaux that map onto Purkinje cell functional zones. Using cell-specific genetic tracing with an Ascl1^CreERT2 mouse conditional allele, we reveal that basket cell zones comprise different sizes of pinceaux. We tested whether Purkinje cells instruct the assembly of inhibitory projections into zones, as they do for excitatory afferents. Genetically silencing Purkinje cell neurotransmission blocks the formation of sharp Purkinje cell zones and disrupts excitatory axon patterning. The distribution of pinceaux into size-specific zones is eliminated without Purkinje cell GABAergic output. Our data uncover the cellular and molecular diversity of a foundational synapse that revolutionized neuroscience.

Zebrin Expression in the Cerebellum of Two Crocodilian Species

While in birds and mammals the cerebellum is a highly convoluted structure that consists of numerous transverse lobules, in most amphibians and reptiles it consists of only a single unfolded sheet. Orthogonal to the lobules, the cerebellum is comprised of sagittal zones that are revealed in the pattern of afferent inputs, the projection patterns of Purkinje cells, and Purkinje cell response properties, among other features. The expression of several molecular markers, such as aldolase C, is also parasagittally organized. Aldolase C, also known as zebrin II (ZII), is a glycolytic enzyme expressed in the cerebellar Purkinje cells of the vertebrate cerebellum. In birds, mammals, and some lizards (Ctenophoresspp.), ZII is expressed in a heterogenous fashion of alternating sagittal bands of high (ZII+) and low (ZII-) expression Purkinje cells. In contrast, turtles and snakes express ZII homogenously (ZII+) in their cerebella, but the pattern in crocodilians is unknown. Here, we examined the expression of ZII in two crocodilian species (Crocodylus niloticus and Alligator mississippiensis) to help determine the evolutionary origin of striped ZII expression in vertebrates. We expected crocodilians to express ZII in a striped (ZII+/ZII-) manner because of their close phylogenetic relationship to birds and their larger and more folded cerebellum compared to that of snakes and turtles. Contrary to our prediction, all Purkinje cells in the crocodilian cerebellum had a generally homogenous expression of ZII (ZII+) rather than clear ZII+/- stripes. Our results suggest that either ZII stripes were lost in three groups (snakes, turtles, and crocodilians) or ZII stripes evolved independently three times (lizards, birds, and mammals).

Identification of Novel Pathways Associated with Patterned Cerebellar Purkinje Neuron Degeneration in Niemann-Pick Disease, Type C1

Niemann-Pick disease, type C1 (NPC1) is a lysosomal disease characterized by progressive cerebellar ataxia. In NPC1, a defect in cholesterol transport leads to endolysosomal storage of cholesterol and decreased cholesterol bioavailability. Purkinje neurons are sensitive to the loss of NPC1 function. However, degeneration of Purkinje neurons is not uniform. They are typically lost in an anterior-to-posterior gradient with neurons in lobule X being resistant to neurodegeneration. To gain mechanistic insight into factors that protect or potentiate Purkinje neuron loss, we compared RNA expression in cerebellar lobules III, VI, and X from control and mutant mice. An unexpected finding was that the gene expression differences between lobules III/VI and X were more pronounced than those observed between mutant and control mice. Functional analysis of genes with anterior to posterior gene expression differences revealed an enrichment of genes related to neuronal cell survival within the posterior cerebellum. This finding is consistent with the observation, in multiple diseases, that posterior Purkinje neurons are, in general, resistant to neurodegeneration. To our knowledge, this is the first study to evaluate anterior to posterior transcriptome-wide changes in gene expression in the cerebellum. Our data can be used to not only explore potential pathological mechanisms in NPC1, but also to further understand cerebellar biology.

Functional Outcomes of Cerebellar Malformations

The cerebellum is well-established as a primary center for controlling sensorimotor functions. However, recent experiments have demonstrated additional roles for the cerebellum in higher-order cognitive functions such as language, emotion, reward, social behavior, and working memory. Based on the diversity of behaviors that it can influence, it is therefore not surprising that cerebellar dysfunction is linked to motor diseases such as ataxia, dystonia, tremor, and Parkinson's disease as well to non-motor disorders including autism spectrum disorders (ASD), schizophrenia, depression, and anxiety. Regardless of the condition, there is a growing consensus that developmental disturbances of the cerebellum may be a central culprit in triggering a number of distinct pathophysiological processes. Here, we consider how cerebellar malformations and neuronal circuit wiring impact brain function and behavior during development. We use the cerebellum as a model to discuss the expanding view that local integrated brain circuits function within the context of distributed global networks to communicate the computations that drive complex behavior. We highlight growing concerns that neurological and neuropsychiatric diseases with severe behavioral outcomes originate from developmental insults to the cerebellum.

Cerebellar Modules and Their Role as Operational Cerebellar Processing Units: A Consensus paper [corrected]

The compartmentalization of the cerebellum into modules is often used to discuss its function. What, exactly, can be considered a module, how do they operate, can they be subdivided and do they act individually or in concert are only some of the key questions discussed in this consensus paper. Experts studying cerebellar compartmentalization give their insights on the structure and function of cerebellar modules, with the aim of providing an up-to-date review of the extensive literature on this subject. Starting with an historical perspective indicating that the basis of the modular organization is formed by matching olivocorticonuclear connectivity, this is followed by consideration of anatomical and chemical modular boundaries, revealing a relation between anatomical, chemical, and physiological borders. In addition, the question is asked what the smallest operational unit of the cerebellum might be. Furthermore, it has become clear that chemical diversity of Purkinje cells also results in diversity of information processing between cerebellar modules. An additional important consideration is the relation between modular compartmentalization and the organization of the mossy fiber system, resulting in the concept of modular plasticity. Finally, examination of cerebellar output patterns suggesting cooperation between modules and recent work on modular aspects of emotional behavior are discussed. Despite the general consensus that the cerebellum has a modular organization, many questions remain. The authors hope that this joint review will inspire future cerebellar research so that we are better able to understand how this brain structure makes its vital contribution to behavior in its most general form.

Unique degeneration signatures in the cerebellar cortex for spinocerebellar ataxias 2, 3, and 7

Spinocerebellar ataxias (SCAs) are a heterogeneous group of neurodegenerative diseases that selectively affect vulnerable neuronal populations in the cerebellum and other subcortical regions. While previous studies have reported subtype differences in the absolute amount of degeneration in specific regions of interest, they failed to account for two important factors. First, they did not control for overall differences in the severity of the degeneration pattern, and second, they did not fully characterize the spatial pattern of degeneration for each SCA subtype. Here, we provide a systematic characterization of the spatial degeneration patterns for three polyQ SCAs (55 patients, either SCA2, SCA3, or SCA7) while controlling for the severity of the degeneration pattern. After this correction, the cerebellar degeneration pattern can successfully classify between the three different SCA subtypes with high cross-validated accuracy. Specifically, degeneration in SCA3 disproportionally affects motor regions of the cerebellar cortex, which explains the relatively severe motor symptoms observed in this subtype. Our results demonstrate that each of the three studied SCA subtypes has a unique cerebellar degeneration signature, hinting at differences in the disease process. Clinically, these differentiable patterns of cerebellar degeneration can be used to reliably discern subtypes, even at relatively early stages of the disease.

Bergmann Glia are Patterned into Topographic Molecular Zones in the Developing and Adult Mouse Cerebellum

Cerebellar circuits are patterned into an array of topographic parasagittal domains called zones. Zones are best revealed by gene expression, circuit anatomy, and cellular degeneration patterns. Thus far, the study of zones has been focused heavily on how neurons are organized. Because of this, detailed neuronal patterning maps have been established for Purkinje cells, granule cells, Golgi cells, unipolar brush cells, and also for the terminal field organization of climbing fiber and mossy fiber afferents. In comparison, however, it remains poorly understood if glial cells are also organized into zones. We have identified an Npy-Gfp BAC transgenic mouse line (Tau-Sapphire Green fluorescent protein (Gfp) is under the control of the neuropeptide Y (Npy) gene regulatory elements) that can be used to label Bergmann glial cells with Golgi-like resolution. In these adult transgenic mice, we found that Npy-Gfp expression was localized to Bergmann glia mainly in lobules VI/VII and IX/X. Using double immunofluorescence, we show that in these lobules, Npy-Gfp expression in the Bergmann glia overlaps with the pattern of the small heat shock protein HSP25, a Purkinje cell marker for zones located in lobules VI/VII and IX/X. Developmental analysis starting from the day of birth showed that HSP25 and Npy-Gfp expression follow a similar program of spatial and temporal patterning. However, loss of Npy signaling did not alter the patterning of Purkinje cell zones. We conclude that Bergmann glial cells are zonally organized and their patterns are restricted by boundaries that also confine cerebellar neurons into a topographic circuit map.

The modular architecture and neurochemical patterns in the cerebellar cortex

The review deals with topical issues of the neuronal arrangement underlying basic cerebellar functions. The cerebellum and its auxiliary structures contain several hundreds of modules (so called "microzones"). Each module receives the corticopetal input specific for the lobule it belongs to and forms the topographic projection. The precision of the major input-output signal flow in the cerebellar cortex is provided by a pronounced stratification of its synaptic zones of a various origin and regular topography of its afferent connections, interneurons, and efferent neurons. There is a nice match between the anatomical and functional coordinates of the modules, whose spatial boundaries are determined by the spread of afferent excitation and local interneuron connections. The dynamic characteristics of the modules are analyzed by the example of the formation of the nitrergic neuron ensembles and cerebellar projections of corticopetal fibers. The authors discuss the cerebellar blood flow and its relation to the activity of NO/GABAergic Lugaro cells and other interneurons in the cerebellar cortex. A generalized scheme of intra- and intermodular communication is proposed.

Insights into cerebellar development and connectivity

The cerebellum has a well-established role in controlling motor functions such coordination, balance, posture, and skilled learning. There is mounting evidence that it might also play a critical role in non-motor functions such as cognition and emotion. It is therefore not surprising that cerebellar defects are associated with a wide array of diseases including ataxia, dystonia, tremor, schizophrenia, dyslexia, and autism spectrum disorder. What is intriguing is that a seemingly uniform circuit that is often described as being "simple" should carry out all of these behaviors. Analyses of how cerebellar circuits develop have revealed that such descriptions massively underestimate the complexity of the cerebellum. The cerebellum is in fact highly patterned and organized around a series of parasagittal stripes and transverse zones. This topographic architecture partitions all cerebellar circuits into functional modules that are thought to enhance processing power during cerebellar dependent behaviors. What are arguably the most remarkable features of cerebellar topography are the developmental processes that produce them. This review is concerned with the genetic and cellular mechanisms that orchestrate cerebellar patterning. We place a major focus on how Purkinje cells control multiple aspects of cerebellar circuit assembly. Using this model, we discuss evidence for how "zebra-like" patterns in Purkinje cells sculpt the cerebellum, how specific genetic cues mediate the process, and how activity refines the patterns into an adult map that is capable of executing various functions. We also discuss how defective Purkinje cell patterning might impact the pathogenesis of neurological conditions.

Topographic Organization of Inferior Olive Projections to the Zebrin II Stripes in the Pigeon Cerebellar Uvula

This study was aimed at mapping the organization of the projections from the inferior olive (IO) to the ventral uvula in pigeons. The uvula is part of the vestibulocerebellum (VbC), which is involved in the processing of optic flow resulting from self-motion. As in other areas of the cerebellum, the uvula is organized into sagittal zones, which is apparent with respect to afferent inputs, the projection patterns of Purkinje cell (PC) efferents, the response properties of PCs and the expression of molecular markers such as zebrin II (ZII). ZII is heterogeneously expressed such that there are sagittal stripes of PCs with high ZII expression (ZII+), alternating with sagittal stripes of PCs with little to no ZII expression (ZII−). We have previously demonstrated that a ZII+/− stripe pair in the uvula constitutes a functional unit, insofar as the complex spike activity (CSA) of all PCs within a ZII+/− stripe pair respond to the same type of optic flow stimuli. In the present study we sought to map the climbing fiber (CF) inputs from the IO to the ZII+ and ZII− stripes in the uvula. We injected fluorescent Cholera Toxin B (CTB) of different colors (red and green) into ZII+ and ZII− bands of functional stripe pair. Injections in the ZII+ and ZII− bands resulted in retrograde labeling of spatially separate, but adjacent regions in the IO. Thus, although a ZII+/− stripe pair represents a functional unit in the pigeon uvula, CF inputs to the ZII+ and ZII− stripes of a unit arise from separate regions of the IO.

Inferior olivary projection to the zebrin II stripes in lobule IXcd of the pigeon flocculus: A retrograde tracing study

Zebrin II (ZII; a.k.a. aldolase C) is expressed heterogeneously in Purkinje cells (PCs) such that there are sagittal stripes of high expression (ZII+) interdigitated with stripes of little or no expression (ZII-). The pigeon flocculus receives visual-optokinetic information and is important for generating compensatory eye movements. It consists of 4 sagittal zones based on PC complex spike activity (CSA) in response to rotational optokinetic stimuli. There are two zones where CSA responds best to rotation about the vertical axis (VA), interdigitated with two zones where CSA responds best to rotation about an horizontal axis (HA). These optokinetic zones relate to the ZII stripes in folium IXcd of the flocculus, such that an optokinetic zone spans a ZII+/- pair: the HA zones span the P5+/- and P7+/- ZII stripe pairs, whereas the VA zones correspond to ZII stripe pairs P4+/- and P6+/-. In the present study, we used fluorescent retrograde tracing to determine the olivary inputs to the ZII+ and ZII- stripes within the functional pairs. We found that separate but adjacent areas of the medial column of the inferior olive (mcIO) project to the ZII+ and ZII- stripes within each of the functional pairs. Thus, although a ZII+/- stripe pair represents a functional unit in the pigeon flocculus insofar as the CSA of all PCs in the stripe pair encodes similar sensory information, the olivary inputs to the ZII+ and ZII- stripes arise from different, although adjacent, regions of the mcIO.

Overexpression of Human SOD1 Leads to Discrete Defects in the Cerebellar Architecture in the Mouse

The human superoxide dismutase 1 (SOD1) gene is responsible for neutralizing supercharged oxygen radicals within the cell. Mutation in SOD1 gene causes amyotrophic lateral sclerosis (ALS). Recent studies have shown involvement of the cerebellum in ALS, although the cerebellar contribution in SOD1 transgenic mice remains unclear. Using immunohistopathology, we investigated the Purkinje cell phenotype in the vermis of the SOD1 transgenic mice cerebellum. Calbindin 1 (Calb1) and three well-known zone and stripe markers, zebrin II, HSP25, and PLCβ4 have been used to explore possible alteration in zone and stripe. Here we show that Calb1 expression is significantly reduced in a subset of the Purkinje cells that is almost aligned with the cerebellar zones and stripes pattern. The Purkinje cells of SOD1 transgenic mice display a pattern of Calb1 down-regulation, which seems to proceed to Purkinje cell degeneration as the mice age. The onset of Calb1 down-regulation in Purkinje cells begins from the central zone and continues into the nodular zone, however it has not been observed in the anterior and posterior zones. In a subgroup of SOD1 transgenic mice in which gait unsteadiness was apparent, down-regulation of Calb1 is seen in a subset of PLCβ4⁺ Purkinje cells in the anterior zone. These observations suggest that the Calb1^- subset of Purkinje cells in the anterior zone, which receives somatosensory input, causes unsteady gait. Our data suggest that human SOD1 overexpression leads to Calb1 down-regulation in the zone and strip pattern and raise the question of whether SOD1 overexpression leads to Purkinje cells degeneration.

Consensus Paper: Cerebellar Development

The development of the mammalian cerebellum is orchestrated by both cell-autonomous programs and inductive environmental influences. Here, we describe the main processes of cerebellar ontogenesis, highlighting the neurogenic strategies used by developing progenitors, the genetic programs involved in cell fate specification, the progressive changes of structural organization, and some of the better-known abnormalities associated with developmental disorders of the cerebellum.

Differential timing of granule cell production during cerebellum development underlies generation of the foliation pattern

Background

The mouse cerebellum (Cb) has a remarkably complex foliated three-dimensional (3D) structure, but a stereotypical cytoarchitecture and local circuitry. Little is known of the cellular behaviors and genes that function during development to determine the foliation pattern. In the anteroposterior axis the mammalian cerebellum is divided by lobules with distinct sizes, and the foliation pattern differs along the mediolateral axis defining a medial vermis and two lateral hemispheres. In the vermis, lobules are further grouped into four anteroposterior zones (anterior, central, posterior and nodular zones) based on genetic criteria, and each has distinct lobules. Since each cerebellar afferent group projects to particular lobules and zones, it is critical to understand how the 3D structure of the Cb is acquired. During cerebellar development, the production of granule cells (gcs), the most numerous cell type in the brain, is required for foliation. We hypothesized that the timing of gc accumulation is different in the four vermal zones during development and contributes to the distinct lobule morphologies.

Methods and Results

In order to test this idea, we used genetic inducible fate mapping to quantify accumulation of gcs in each lobule during the first two postnatal weeks in mice. The timing of gc production was found to be particular to each lobule, and delayed in the central zone lobules relative to the other zones. Quantification of gc proliferation and differentiation at three time-points in lobules representing different zones, revealed the delay involves a later onset of maximum differentiation and prolonged proliferation of gc progenitors in the central zone. Similar experiments in Engrailed mutants (En1^−/+;En2^−/−), which have a smaller Cb and altered foliation pattern preferentially outside the central zone, showed that gc production, proliferation and differentiation are altered such that the differences between zones are attenuated compared to wild-type mice.

Conclusions

Our results reveal that gc production is differentially regulated in each zone of the cerebellar vermis, and our mutant analysis indicates that the dynamics of gc production plays a role in determining the 3D structure of the Cb.

Electronic supplementary material

The online version of this article (doi:10.1186/s13064-016-0072-z) contains supplementary material, which is available to authorized users.

Maternal immune activation produces cerebellar hyperplasia and alterations in motor and social behaviors in male and female mice

There have been suggestions that maternal immune activation is associated with alterations in motor behavior in offspring. To explore this further, we treated pregnant mice with polyinosinic:polycytidylic acid (poly(I:C)), a viral mimetic that activates the innate immune system, or saline on embryonic days 13-15. At postnatal day (P) 18, offspring cerebella were collected from perfused brains and immunostained as whole-mounts for zebrin II. Measurements of zebrin II+/- stripes in both sexes indicated that prenatal poly(I:C)-exposed offspring had significantly wider stripes; this difference was also seen in similarly treated offspring in adulthood (~P120). When sagittal sections of the cerebellum were immunostained for calbindin and Purkinje cell numbers were counted, we observed greater numbers of Purkinje cells in poly(I:C) offspring at both P18 and ~ P120. In adolescence (~P40), both male and female prenatal poly(I:C)-exposed offspring exhibited poorer performance on the rotarod and ladder rung tests; deficits in performance on the latter test persisted into adulthood. Offspring of both sexes from poly(I:C) dams also exhibited impaired social interaction in adolescence, but this difference was no longer apparent in adulthood. Our results suggest that maternal immune exposure at a critical time of cerebellum development can enhance neuronal survival or impair normal programmed cell death of Purkinje cells, with lasting consequences on cerebellar morphology and a variety of motor and non-motor behaviors.

Pathogenesis of severe ataxia and tremor without the typical signs of neurodegeneration

Neurological diseases are especially devastating when they involve neurodegeneration. Neuronal destruction is widespread in cognitive disorders such as Alzheimer's and regionally localized in motor disorders such as Parkinson's, Huntington's, and ataxia. But, surprisingly, the onset and progression of these diseases can occur without neurodegeneration. To understand the origins of diseases that do not have an obvious neuropathology, we tested how loss of CAR8, a regulator of IP3R1-mediated Ca(2+)-signaling, influences cerebellar circuit formation and neural function as movement deteriorates. We found that faulty molecular patterning, which shapes functional circuits called zones, leads to alterations in cerebellar wiring and Purkinje cell activity, but not to degeneration. Rescuing Purkinje cell function improved movement and reducing their Ca(2+) influx eliminated ectopic zones. Our findings in Car8(wdl) mutant mice unveil a pathophysiological mechanism that may operate broadly to impact motor and non-motor conditions that do not involve degeneration.

The Neuroplastin adhesion molecules: key regulators of neuronal plasticity and synaptic function

The Neuroplastins Np65 and Np55 are neuronal and synapse-enriched immunoglobulin superfamily molecules that play important roles in a number of key neuronal and synaptic functions including, for Np65, cell adhesion. In this review we focus on the physiological roles of the Neuroplastins in promoting neurite outgrowth, regulating the structure and function of both inhibitory and excitatory synapses in brain, and in neuronal and synaptic plasticity. We discuss the underlying molecular and cellular mechanisms by which the Neuroplastins exert their physiological effects and how these are dependent upon the structural features of Np65 and Np55, which enable them to bind to a diverse range of protein partners. In turn this enables the Neuroplastins to interact with a number of key neuronal signalling cascades. These include: binding to and activation of the fibroblast growth factor receptor; Np65 trans-homophilic binding leading to activation of p38 MAPK and internalization of glutamate (GluR1) receptor subunits; acting as accessory proteins for monocarboxylate transporters, thus affecting neuronal energy supply, and binding to GABAA α1, 2 and 5 subunits, thus regulating the composition and localization of GABAA receptors. An emerging theme is the role of the Neuroplastins in regulating the trafficking and subcellular localization of specific binding partners. We also discuss the involvement of Neuroplastins in a number of pathophysiological conditions, including ischaemia, schizophrenia and breast cancer and the role of a single nucleotide polymorphism in the human Neuroplastin (NPTN) gene locus in impairment of cortical development and cognitive functions. Neuroplastins are neuronal cell adhesion molecules, which induce neurite outgrowth and play important roles in synaptic maturation and plasticity. This review summarizes the functional implications of Neuroplastins for correct synaptic membrane protein localization, neuronal energy supply, expression of LTP and LTD, animal and human behaviour, and pathophysiology and disease. It focuses particularly on Neuroplastin binding partners and signalling mechanisms, and proposes perspectives for future research on these important immunoglobulin superfamily members.

Enhanced heat shock protein 25 immunoreactivity in cranial nerve motoneurons and their related fiber tracts in rats prenatally-exposed to X-irradiation

Alterations in histoarchitecture of the brainstem were examined immunohistochemically in 4-week-old rats with a single whole body X-irradiation at a dose of 0.5, 1.0, or 1.5 Gy on embryonic day (ED) 15 using anti-heat shock protein 25 (HSP25). HSP25 immunostaining was seen in the neuronal perikarya of cranial nerve motoneurons, that is, the motor and mesencephalic nuclei of the trigeminal nerve, facial nucleus, abducens nucleus and accessory facial nucleus in the pons, and the ambiguous nucleus, dorsal nucleus of vagus nerve and hypoglossus nucleus in the medulla oblongata of intact controls. In 0.5 to 1.5 Gy-irradiated rats, HSP25 immunostaining in those neurons was more intense than in controls, while the most intense immunostaining was marked in 1.5 Gy-irradiated rats. HSP25 immunostaining was also apparent in the spinal tract of the trigeminal nerve and facial nerve tracts in 0.5 to 1.5 Gy-irradiated rats, but was faint in controls. Interestingly, HSP25 immunostaining was aberrantly enhanced in dendritic arbors in the magnocellular region of medial vestibular nucleus of 0.5-1.5 Gy-irradiated rats. Those arbors were identified as excitatory secondary vestibulo-ocular neurons by double immunofluorescence for HSP25 and SMI-32. The results suggest an increase of HSP25 expression in cranial nerve motoneurons and their related fiber tracts from prenatal exposure to ionizing irradiation. This may be an adaptive response to chronic hypoxia due to malformed brain arteries caused by prenatal ionizing irradiation.

Purkinje cell stripes and long-term depression at the parallel fiber-Purkinje cell synapse

The cerebellar cortex comprises a stereotyped array of transverse zones and parasagittal stripes, built around multiple Purkinje cell subtypes, which is highly conserved across birds and mammals. This architecture is revealed in the restricted expression patterns of numerous molecules, in the terminal fields of the afferent projections, in the distribution of interneurons, and in the functional organization. This review provides an overview of cerebellar architecture with an emphasis on attempts to relate molecular architecture to the expression of long-term depression (LTD) at the parallel fiber-Purkinje cell (pf-PC) synapse.

Mouse model reveals the role of RERE in cerebellar foliation and the migration and maturation of Purkinje cells

Nuclear receptors and their coregulators play a critical role in brain development by regulating the spatiotemporal expression of their target genes. The arginine-glutamic acid dipeptide repeats gene (Rere) encodes a nuclear receptor coregulator previously known as Atrophin 2. In the developing cerebellum, RERE is expressed in the molecular layer, the Purkinje cell layer and the granule cell layer but not in granule cell precursors. To study RERE's role in cerebellar development, we used RERE-deficient embryos bearing a null allele (om) and a hypomorphic allele (eyes3) of Rere (Rere^om/eyes3). In contrast to wild-type embryos, formation of the principal fissures in these RERE-deficient embryos was delayed and the proliferative activity of granule cell precursors (GCPs) was reduced at E18.5. This reduction in proliferation was accompanied by a decrease in the expression of sonic hedgehog (SHH), which is secreted from Purkinje cells and is required for normal GCP proliferation. The maturation and migration of Purkinje cells in Rere^om/eyes3 embryos was also delayed with decreased numbers of post-migratory Purkinje cells in the cerebellum. During the postnatal period, RERE depletion caused incomplete division of lobules I/II and III due to truncated development of the precentral fissure in the cerebellar vermis, abnormal development of lobule crus I and lobule crus II in the cerebellar hemispheres due to attenuation of the intercrural fissure, and decreased levels of Purkinje cell dendritic branching. We conclude that RERE-deficiency leads to delayed development of the principal fissures and delayed maturation and migration of Purkinje cells during prenatal cerebellar development and abnormal cerebellar foliation and Purkinje cell maturation during postnatal cerebellar development.

The neuroplastins: multifunctional neuronal adhesion molecules--involvement in behaviour and disease

The neuroplastins np65 and np55 are neuronal and synapse-enriched immunoglobulin (Ig) superfamily cell adhesion molecules that contain 3 and 2 Ig domains, respectively. Np65 is neuron specific whereas np55 is expressed in many tissues. They are multifunctional proteins whose physiological roles are defined by the partner proteins they bind to and the signalling pathways they activate. The neuroplastins are implicated in activity-dependent long-term synaptic plasticity. Thus neuroplastin-specific antibodies and a recombinant peptide inhibit long-term potentiation in hippocampal neurones. This is mediated by activation of the p38MAP kinase signalling pathway, resulting in the downregulation of the surface expression of GluR1 receptors. Np65, but not np55, exhibits trans-homophilic binding. Both np65 and np55 induce neurite outgrowth and both activate the FGF receptor and associated downstream signalling pathways. Np65 binds to and colocalises with GABA(A) receptor subtypes and may play a role in anchoring them to specific synaptic and extrasynaptic sites. Most recently the neuroplastins have been shown to chaperone and support the monocarboxylate transporter MCT2 in transporting lactate across the neuronal plasma membrane. Thus the neuroplastins are multifunctional adhesion molecules which support neurite outgrowth, modulate long-term activity-dependent synaptic plasticity, regulate surface expression of GluR1 receptors, modulate GABA(A) receptor localisation, and play a key role in delivery of monocarboxylate energy substrates both to the synapse and to extrasynaptic sites. The diverse functions and range of signalling pathways activated by the neuroplastins suggest that they are important in modulating behaviour and in relation to human disease.

The neuroplastin adhesion molecules are accessory proteins that chaperone the monocarboxylate transporter MCT2 to the neuronal cell surface

BACKGROUND

The neuroplastins np65 and np55 are two synapse-enriched immunoglobulin (Ig) superfamily adhesion molecules that contain 3 and 2 Ig domains respectively. Np65 is implicated in long term, activity dependent synaptic plasticity, including LTP. Np65 regulates the surface expression of GluR1 receptor subunits and the localisation of GABA(A) receptor subtypes in hippocampal neurones. The brain is dependent not only on glucose but on monocarboxylates as sources of energy. The. monocarboxylate transporters (MCTs) 1-4 are responsible for the rapid proton-linked translocation of monocarboxylates including pyruvate and lactate across the plasma membrane and require association with either embigin or basigin, proteins closely related to neuroplastin, for plasma membrane expression and activity. MCT2 plays a key role in providing lactate as an energy source to neurons.

METHODOLOGY/FINDINGS

Here we use co-transfection of neuroplastins and monocarboxylate transporters into COS-7 cells to demonstrate that neuroplastins can act as ancillary proteins for MCT2. We also show that Xenopus laevis oocytes contain endogenous neuroplastin and its knockdown with antisense RNA reduces the surface expression of MCT2 and associated lactate transport. Immunocytochemical studies show that MCT2 and the neuroplastins are co-localised in rat cerebellum. Strikingly neuroplastin and MCT2 are enriched in the same parasagittal zebrin II-negative stripes.

CONCLUSIONS

These data strongly suggest that neuroplastins act as key ancillary proteins for MCT2 cell surface localisation and activity in some neuronal populations, thus playing an important role in facilitating the uptake of lactate for use as a respiratory fuel.

Heterogeneity of calretinin expression in the avian cerebellar cortex of pigeons and relationship with zebrin II

The cerebellar cortex has a fundamental parasagittal organization that is reflected in the physiological responses of Purkinje cells, projections of Purkinje cells, afferent inputs from climbing and mossy fibres and the expression of several molecular markers. The most thoroughly studied of these molecular markers is zebrin II (ZII; a.k.a. aldolase C). ZII is differentially expressed in Purkinje cells, resulting in a pattern of sagittal stripes of high expression (ZII+ve) interdigitated with stripes of little or no expression (ZII-ve). The calcium binding protein calretinin (CR) is expressed heavily in mossy fibres terminating throughout the cerebellar cortex, but whether CR is heterogeneously expressed in parasagittal stripes, like ZII, is unknown. In this study, we examined CR expression in the cerebellum of pigeons and compared it to that of ZII. CR was expressed heavily in the granule layer in mossy fibres and their terminal rosettes. Moreover, CR is expressed heterogeneously in the granule layer such that there are sagittal stripes of heavy CR labelling (CR+ve) alternating with stripes of weaker labelling (CR-ve). The CR heterogeneity is most notable in folium IXcd and folia II-IV in the anterior lobe. In the anterior lobe, the central CR+ve stripe spanning the midline is aligned with the central ZII+ve stripe, whereas the other CR+ve stripes are aligned with the ZII-ve stripes. In IXcd, the CR+ve stripes are aligned with the ZII+ve stripes. This combination of aligned and unaligned CR+ve stripes, relative to ZII+ve stripes, differs from that of parvalbumin and other neurochemical markers, but the functional consequences of this is unclear. With respect to the posterior lobe, we suggest that the CR+ve mossy fibres to IXcd originate in two retinal recipient nuclei that are involved in the processing of optic flow.

Purkinje cell compartmentalization in the cerebellum of the spontaneous mutant mouse dreher

The cerebellar morphological phenotype of the spontaneous neurological mutant mouse dreher (Lmx1a(dr-J)) results from cell fate changes in dorsal midline patterning involving the roof plate and rhombic lip. Positional cloning revealed that the gene Lmx1a, which encodes a LIM homeodomain protein, is mutated in dreher, and is expressed in the developing roof plate and rhombic lip. Loss of Lmx1a causes reduction of the roof plate, an important embryonic signaling center, and abnormal cell fate specification within the embryonic cerebellar rhombic lip. In adult animals, these defects result in variable, medial fusion of the cerebellar vermis and posterior cerebellar vermis hypoplasia. It is unknown whether deleting Lmx1a results in displacement or loss of specific lobules in the vermis. To distinguish between an ectopic and absent vermis, the expression patterns of two Purkinje cell-specific compartmentation antigens, zebrin II/aldolase C and the small heat shock protein HSP25 were analyzed in dreher cerebella. The data reveal that despite the reduction in volume and abnormal foliation of the cerebellum, the transverse zones and parasagittal stripe arrays characteristic of the normal vermis are present in dreher, but may be highly distorted. In dreher mutants with a severe phenotype, zebrin II stripes are fragmented and distributed non-symmetrically about the cerebellar midline. We conclude that although Purkinje cell agenesis or selective Purkinje cell death may contribute to the dreher phenotype, our data suggest that aberrant anlage patterning and granule cell development lead to Purkinje cell ectopia, which ultimately causes abnormal cerebellar architecture in dreher.

Heterochronic protein expression patterns in the developing embryonic chick cerebellum

The advantages of the embryonic chick as a model for studying neural development range from the relatively low cost of fertilized eggs to the rapid rate of development. We investigated in ovo cerebellar development in the chick, which has a nearly identical embryonic period as the mouse (19-22 days). We focused on three antigens: Calbindin (CB), Zebrin II (ZII), and Calretinin (CR), and our results demonstrate asynchronous expression patterns during cerebellar development. Presumptive CB+ Purkinje cells are first observed at embryonic day (E)10 in clusters in posterior cerebellum. At E12, corresponding with global expression of CB across the cerebellum, Purkinje cells began to express ZII. By E14-E16, Purkinje cells disperse into a monolayer and develop a pattern of alternating immunopositive and immunonegative ZII stripes. CR is initially expressed by clusters of presumptive Purkinje cells in the nodular zone at E8. However, this expression is transient and at later stages, CR is largely confined to the granule and molecular layers. Before hatch (E18-E20), Purkinje cells adopt a morphologically mature phenotype with complex dendritic arborizations. Comparing this data to that seen in mice, we found that the sequence of Purkinje cell formation, protein expression, and development is similar in both species, but these events consistently begin ∼5-7 days earlier in the precocial chick cerebellum, suggesting an important role for heterochrony in neurodevelopment.

On the architecture of the posterior zone of the cerebellum

The mammalian cerebellum is histologically uniform. However, underlying the simple laminar architecture is a complex arrangement of parasagittal stripes and transverse zones that can be revealed by the expression of many molecules, in particular, zebrin II/aldolase C. By using a combination of Purkinje cell antigenic markers and afferent tracing, four transverse zones have been identified: in mouse, these are the anterior zone (∼lobules I-V), the central zone (∼lobules VI-VII), the posterior zone (PZ: ∼lobules VIII-dorsal IX), and the nodular zone (∼ventral lobule IX + lobule X). A fifth transverse zone-the lingular zone (∼lobule I)-is found in birds and bats. Within the anterior and posterior zones, parasagittal stripes of Purkinje cells expressing zebrin II alternate with those that do not. To explore this model further and to broaden our understanding of the evolution of cerebellar patterning, stripes in the PZ have been compared in multiple mammalian species. We conclude that a posterior zone with a conserved stripe organization is a common feature of the mammalian and avian cerebellar vermis and that zonal boundaries are independent of cerebellar lobulation.

Neurofilament heavy chain expression reveals a unique parasagittal stripe topography in the mouse cerebellum

Despite the general uniformity in cellular composition of the adult cerebellum (Cb), the expression of proteins such as ZebrinII/AldolaseC and the small heat shock protein HSP25 reveal striking patterns of parasagittal Purkinje cell (PC) stripes. Based on differences in the stripe configuration within subsets of lobules, the Cb can be further divided into four anterior-posterior transverse zones: anterior zone (AZ) = lobules I-V, central zone (CZ) = lobules VI-VII, posterior zone (PZ) = lobules VIII and anterior IX, and the nodular zone (NZ) = lobules posterior IX-X. Here we used whole-mount and tissue section immunohistochemistry to show that neurofilament heavy chain (NFH) expression alone divides all lobules of the mouse Cb into a complex series of parasagittal stripes of PCs. We revealed that the striped pattern of NFH in the vermis of the AZ and PZ was complementary to ZebrinII and phospholipase C ß3 (PLCß3), and corresponded to phospholipase C ß4 (PLCß4). In the CZ and NZ the stripe pattern of NFH was complementary to HSP25 and corresponded to PLCß3. The boundaries of the NFH stripes were not always sharply delineated. Instead, a gradual decrease in NFH expression was observed toward the edges of particular stripes, resulting in domains comprised of overlapping expression patterns. Furthermore, the terminal field distributions of mossy and climbing fibers had a complex but consistent topographical alignment with NFH stripes. In summary, NFH expression reveals an exquisite level of Cb stripe complexity that respects the transverse zone divisions and delineates an intricately patterned target field for Cb afferents.

Loss of intrinsic organization of cerebellar networks in spinocerebellar ataxia type 1: correlates with disease severity and duration

The spinocerebellar ataxias (SCAs) are a genetically heterogeneous group of cerebellar degenerative disorders, characterized by progressive gait unsteadiness, hand incoordination, and dysarthria. The mutational mechanism in SCA1, a dominantly inherited form of SCA, consists of an expanded trinucleotide CAG repeat. In SCA1, there is loss of Purkinje cells, neuronal loss in dentate nucleus, olives, and pontine nuclei. In the present study, we sought to apply intrinsic functional connectivity analysis combined with diffusion tensor imaging to define the state of cerebellar connectivity in SCA1. Our results on the intrinsic functional connectivity in lateral cerebellum and thalamus showed progressive organizational changes in SCA1 noted as a progressive increase in the absolute value of the correlation coefficients. In the lateral cerebellum, the anatomical organization of functional clusters seen as parasagittal bands in controls is lost, changing to a patchy appearance in SCA1. Lastly, only fractional anisotropy in the superior peduncle and changes in functional organization in thalamus showed a linear dependence to duration and severity of disease. The present pilot work represents an initial effort describing connectivity biomarkers of disease progression in SCA1. The functional changes detected with intrinsic functional analysis and diffusion tensor imaging suggest that disease progression can be analyzed as a disconnection syndrome.

Postnatal growth velocity modulates alterations of proteins involved in metabolism and neuronal plasticity in neonatal hypothalamus in rats born with intrauterine growth restriction

Intrauterine growth restriction (IUGR) due to maternal protein restriction is associated in rats with an alteration in hypothalamic centers involved in feeding behaviour. In order to gain insight into the mechanism of perinatal maternal undernutrition in the brain, we used proteomics approach to identify hypothalamic proteins that are altered in their expression following protein restriction in utero. We used an animal model in which restriction of the protein intake of pregnant rats (8% vs. 20%) produces IUGR pups which were randomized to a nursing regimen leading to either rapid or slow catch-up growth. We identified several proteins which allowed, by multivariate analysis, a very good discrimination of the three groups according to their perinatal nutrition. These proteins were related to energy-sensing pathways (Eno 1, E(2)PDH, Acot 1 and Fabp5), redox status (Bcs 1L, PrdX3 and 14-3-3 protein) or amino acid pathway (Acy1) as well as neurodevelopment (DRPs, MAP2, Snca). In addition, the differential expressions of several key proteins suggested possible shunts towards ketone-body metabolism and lipid oxidation, providing the energy and carbon skeletons necessary to lipogenesis. Our results show that maternal protein deprivation during pregnancy only (IUGR with rapid catch-up growth) or pregnancy and lactation (IUGR with slow postnatal growth) modulates numerous metabolic pathways resulting in alterations of hypothalamic energy supply. As several of these pathways are involved in signalling, it remains to be determined whether hypothalamic proteome adaptation of IUGR rats in response to different postnatal growth rates could also interfere with cerebral plasticity or neuronal maturation.

Apoptosis inducing factor deficiency causes reduced mitofusion 1 expression and patterned Purkinje cell degeneration

Alteration in mitochondrial dynamics has been implicated in many neurodegenerative diseases. Mitochondrial apoptosis inducing factor (AIF) plays a key role in multiple cellular and disease processes. Using immunoblotting and flow cytometry analysis with Harlequin mutant mice that have a proviral insertion in the AIF gene, we first revealed that mitofusion 1 (Mfn1), a key mitochondrial fusion protein, is significantly diminished in Purkinje cells of the Harlequin cerebellum. Next, we investigated the cerebellar pathology of Harlequin mice in an age-dependent fashion, and identified a striking process of progressive and patterned Purkinje cell degeneration. Using immunohistochemistry with zebrin II, the most studied compartmentalization marker in the cerebellum, we found that zebrin II-negative Purkinje cells first started to degenerate at 7 months of age. By 11 months of age, almost half of the Purkinje cells were degenerated. Subsequently, most of the Purkinje cells disappeared in the Harlequin cerebellum. The surviving Purkinje cells were concentrated in cerebellar lobules IX and X, where these cells were positive for heat shock protein 25 and resistant to degeneration. We further showed that the patterned Purkinje cell degeneration was dependent on caspase but not poly(ADP-ribose) polymerase-1 (PARP-1) activation, and confirmed the marked decrease of Mfn1 in the Harlequin cerebellum. Our results identified a previously unrecognized role of AIF in Purkinje cell degeneration, and revealed that AIF deficiency leads to altered mitochondrial fusion and caspase-dependent cerebellar Purkinje cell loss in Harlequin mice. This study is the first to link AIF and mitochondrial fusion, both of which might play important roles in neurodegeneration.

Expression of the IP3R1 promoter-driven nls-lacZ transgene in Purkinje cell parasagittal arrays of developing mouse cerebellum

The cerebellar Purkinje cell monolayer is organized into heterogeneous Purkinje cell compartments that have different molecular compositions. Here we describe a transgenic mouse line, 1NM13, that shows heterogeneous transgene expression in parasagittal Purkinje cell arrays. The transgene consists of a nuclear localization signal (nls) fused to the beta-galactosidase (lacZ) composite gene driven by the type 1 inositol 1,4,5-trisphosphate receptor (IP(3)R1) gene promoter. IP(3)R1-nls-lacZ transgene expression was detected at a single Purkinje cell level over the surface of a whole-mount X-gal-stained cerebellum because of nuclear accumulation of the nls-lacZ activity. Developing cerebella of 1NM13 mice showed stripe-like X-gal staining patterns of parasagittal Purkinje cell subsets. The X-gal stripe pattern was likely determined by an intrinsic property as early as E15 and showed increasing complexity with cerebellar development. The X-gal stripe pattern was reminiscent of, but not identical to, the stripe pattern of zebrin II immunoreactivity. We designated the symmetrical X-gal-positive (transgene-positive, Tg(+)) Purkinje cell stripes about the midline as vermal Tg1(+), Tg2(a, b)(+) and Tg3(a, b)(+) stripes and hemispheric Tg4(a, b)(+), Tg5(a, b)(+), Tg6(a, b, c)(+), and Tg7(a, b)(+) stripes, where a, b, and c indicate substripes. We also assigned three parafloccular substripes Tg8(a, b, c)(+). The boundaries of X-gal stripes at P5 were consistent with raphes in the Purkinje cell layer through which granule cells migrate, suggesting a possible association of the X-gal stripes with raphe formation. Our results indicate that 1NM13 is a good mouse model with a reproducible and clear marker for the compartmentalization of Purkinje cell arrays.

A mutation in the saposin C domain of the sphingolipid activator protein (Prosaposin) gene causes neurodegenerative disease in mice

Saposins A, B, C, and D are small amphiphatic glycoproteins that are encoded in tandem within a precursor protein (prosaposin, PSAP), and are required for in vivo degradation of sphingolipids. Humans with saposin C deficiency exhibit the clinical presentation of Gaucher-like disease. We generated two types of saposin C mutant mice, one carrying a homozygous missense mutation (C384S) in the saposin C domain of prosaposin (Sap-C(-/-)) and the other carrying the compound heterozygous mutation with a second null Psap allele (Psap(-/C384S)). During early life stages, both Sap-C(-/-) and Psap(-/C384S) mice grew normally; however, they developed progressive motor and behavioral deficits after 3 months of age and the majority of affected mice could scarcely move by about 15 months. They showed no signs of hepatosplenomegaly throughout their lives. No accumulation of glucosylceramide and glucosylsphingosine was detected in the brain or liver of both Sap-C(-/-) and Psap(-/C384S) mice. Neuropathological analyses revealed patterned loss of cerebellar Purkinje cells, widespread axonal spheroids filled with membrane-derived concentric or lamellar electron-dense bodies, and lipofuscin-like deposition in the neurons. Soap-bubble-like inclusion bodies were detected in the trigeminal ganglion cells and the vascular endothelial cells. Compound heterozygous Psap(-/C384S) mice showed qualitatively identical but faster progression of the neurological phenotypes than Sap-C(-/-) mice. These results suggest the in vivo role of saposin C in axonal membrane homeostasis, the disruption of which leads to neurodegeneration in lysosomal storage disease.

Antigenic compartmentation of the cerebellar cortex in the chicken (Gallus domesticus)

The chick is a well-understood developmental model of cerebellar pattern formation,but we know much less about the patterning of the adult chicken cerebellum. Therefore an expression study of two Purkinje cell stripe antigens-zebrin II/aldolase C and phospholipase Cbeta4 (PLCbeta4)-has been carried out in the adult chicken (Gallus domesticus). The mammalian cerebellar cortex is built around transverse expression domains ("transverse zones"), each of which is further subdivided into parasagittally oriented stripes. The results from the adult chicken reveal a similar pattern. Five distinct transverse domains were identified. In the anterior lobe a uniformly zebrin II-immunopositive/PLCbeta4-immunonegative lingular zone (LZ; lobule I) and a striped anterior zone (AZ; lobules II-VIa) were distinguished. A central zone (CZ; approximately lobules VIa-VIIIa,b) and a posterior zone (PZ; approximately lobules VIIIa,b-IXc,d) were distinguished in the posterior lobe. Finally, the nodular zone (NZ; lobule X) is uniformly zebrin II-immunoreactive and is innervated by vestibular mossy fibers. Lobule IXc,d is considered as a transitional region between the PZ and the NZ, because the vestibular mossy fiber projection extends into these lobules and because they receive optokinetic mossy and climbing fiber input. It is proposed that the zebrin II-immunonegative P3- stripe corresponds to the lateral vermal B zone of the mammalian cerebellum and that the border between the avian homologs of the mammalian vermis and hemispheres is located immediately lateral to P3-. Thus, there seem to be transverse zones in chicken that are plausible homologs of those identified in mammals, together with an LZ that is characteristic of birds.

Differential expression of FABP 3, 5, 7 in infantile and adult monkey cerebellum

To clarify the involvement of fatty acid binding proteins (FABPs) in cerebellar development and function, we explored the distribution of three brain-expressed FABPs, FABP 3, 5 and 7, by comparing three animal groups--infantile, normal and postischemic adult monkeys. Immunoblotting analysis revealed intense expression of FABP 3 and 7, but not of FABP5, in the control and postischemic adult cerebellum. The protein levels of FABP7, but not of FABP 3 or 5, gradually increased until 2 weeks after the insult. Immunohistochemical analysis showed that cerebellar FABP3-positive cells were Purkinje cells and Bergmann glia. FABP5-positive cells were found only in the postischemic cerebellum, and were identified as activated microglia. Interestingly, in the infantile cerebellum, both the granule cell progenitors in the external granular layer (EGL) and the oligodendrocyte progenitors in the internal granular layer (IGL) expressed FABP5. In the adult cerebellum, FABP7 was expressed in Purkinje cells and basket interneurons, while in the infantile cerebellum it was also found in Bergmann glia. These results showed differential expression of FABPs in cerebellar neuronal and glial cell types; FABP 3 and 7 were predominantly expressed in normal cerebellum, FABP5 after ischemic injury, while FABP 3, 5 and 7 were expressed during cerebellar development.

Alternating array of tyrosine hydroxylase and heat shock protein 25 immunopositive Purkinje cell stripes in zebrin II-defined transverse zone of the cerebellum of rolling mouse Nagoya

The present study examined the spatial organization of tyrosine hydroxylase (TH) immunopositive Purkinje cells in the cerebellum of rolling mouse Nagoya with reference to the distribution pattern of the cerebellar compartmentation antigen, heat shock protein 25 (HSP25). Whole-mount immunostaining revealed a striking pattern of parasagittal stripes of TH staining in the rolling mouse cerebellum but not in the control cerebellum. Although the TH stripes resembled the zebrin II stripes in the rolling cerebellum, these two distributions did not completely overlap. The TH stripes were present in the lobules VI and VII (central zone), the lobule X (nodular zone), and the paraflocculus, where zebrin II immunostaining was uniformly expressed. Double immunostaining revealed that TH stripes were aligned in an alternative fashion with HSP25 stripes within the caudal half of lobule VIb, lobules IXb and X, and paraflocculus. Some, but not all, TH stripes shared boundaries with HSP25 stripes. These results revealed an alternating array of TH immunopositive Purkinje cell subsets with HSP25 immunopositive Purkinje cells in the zebrin II-defined transverse zone of the rolling mouse cerebellum. The constitutive expression of HSP25 may prevent the ectopic expression of TH in zebrin II immunopositive Purkinje cell subsets.

TBR2-immunopsitive unipolar brush cells are associated with ectopic zebrin II-immunoreactive Purkinje cell clusters in the cerebellum of scrambler mice

Unipolar brush cells (UBCs) are excitatory interneurons with their somata located in the granular layer. Recently, T-brain factor 2 (Tbr2) was shown to be expressed in a subset of UBCs in mouse cerebellum. Scrambler mice exhibit severe cerebellum abnormalities, including the failure of embryonic Purkinje cell dispersal and a complete absence of foliation due to a mutation in the disabled-1 adaptor protein. Since most UBC markers are expressed postnatally, it has proven difficult to identify the relationship between developing Purkinje cell clusters and migrating UBCs. Because scrambler mice closely mimic normal embryonic day 18 cerebellum, we examined whether Tbr2-positive UBCs are associated with Purkinje cell cluster markers such as zebrin II, which is the most studied compartmentation marker in the cerebellum. We investigated the distribution of Tbr2-positive UBCs in this mutant by using anti-Tbr2 immunocytochemistry. The data revealed that Tbr2 immunoreactivity was exclusively present in the nucleus of UBCs in scrambler cerebellum. Based on expression data, a Tbr2-positive UBC map was constructed. In addition, Tbr2-positive UBCs are found associated with ectopic zebrin II-immunoreactive Purkinje cell clusters in scrambler cerebellum. These data suggest that UBCs use Purkinje cell compartmentation to migrate into their final position through interactions with the embryonic array of specific Purkinje cell subtypes.

A novel somatostatin-immunoreactive mossy fiber pathway associated with HSP25-immunoreactive purkinje cell stripes in the mouse cerebellum

Somatostatin 28 immunoreactivity (Sst28-ir) identifies a specific subset of mossy fiber terminals in the adult mouse cerebellum. By using double-labeling immunohistochemistry, we determined that Sst28-ir is associated with presynaptic mossy fiber terminal rosettes, and not Purkinje cells, Golgi cells, or unipolar brush cells. Sst28-ir mossy fibers are restricted to the central zone (lobules VI/VII) and nodular zone (lobules IX, X) of the vermis, and the paraflocculus and flocculus. Within each transverse zone the mossy fiber terminal fields form a reproducible array of parasagittal stripes. The boundaries of Sst28-ir stripes align with a specific array of Purkinje cell stripes revealed by using immunocytochemistry for the small heat shock protein HSP25. In the cerebellum of the homozygous weaver mouse, in which a subpopulation of HSP25-ir Purkinje cells are located ectopically, the corresponding Sst28-ir mossy fiber projection is also ectopic, suggesting a role for a specific Purkinje cell subset in afferent pattern formation. Likewise, in the scrambler mutant mouse, Sst28-ir mossy fibers show a very close association with HSP25-ir Purkinje cell clusters. HSP25 itself does not appear to be critical for normal patterning, however: in the KJR mouse, which does not express cerebellar HSP25, Sst28 expression appears to be normal. Likewise, the Purkinje cell patterning antigens zebrin II and HSP25 are expressed normally in both Sst- and Sst-receptor knockout mice, suggesting that somatostatinergic transmission is not necessary for Purkinje cell stripe formation.

Compartmentation of GABA B receptor2 expression in the mouse cerebellar cortex

Despite the apparent uniformity in cellular composition of the adult mammalian cerebellar cortex, it is actually highly compartmentalized into transverse zones, and within each zone the cortex is further subdivided into a reproducible array of parasagittal stripes. The most extensively studied compartmentation antigen is zebrin II/aldolase c, which is expressed by a subset of Purkinje cells forming parasagittal stripes. Gamma-aminobutyric acid B receptors (GABABRs) are G-protein-coupled receptors that mediate a slow, prolonged form of inhibition in many brain areas. This study examines the localization of GABABR2 in the mouse cerebellum by using whole mount and section immunohistochemistry. The data reveal that GABABR2 immunoreactivity is expressed strongly in the dendrites of a subset of Purkinje cells that form a reproducible array of transverse zones and parasagittal stripes. By using double immunostaining, the striped pattern of GABABR2 expression was shown to be identical to that revealed by anti-zebrin II and complementary to that of phospholipase Cbeta4. This finding supports previous functional studies showing that inhibitory neurotransmission is highly patterned in the cerebellar cortex.

Compartmentation of the cerebellar nuclei of the mouse

The cerebellar nuclei integrate inhibitory input from Purkinje cells with excitatory input from mossy and climbing fiber collaterals and are the sole cerebellar output. Numerous studies have shown that the cerebellar cortex is highly compartmentalized into hundreds of genetically determined, reproducible topographic units--transverse zones and parasagittal stripes--that can be identified through the expression patterns of numerous molecules. The Purkinje cell stripes project to the cerebellar nuclei. However, there is no known commensurate topographic complexity in the cerebellar nuclei. Rather, conventional anatomical descriptions identify four major subdivisions--the medial, anterior and posterior interposed, and lateral nuclei--together with a few intranuclear subdivisions. To begin to address the apparent complexity gap, we have used a panel of antigens and transgenes to reveal a reproducible molecular heterogeneity in the mouse cerebellar nuclei. Based on the differential expression patterns, singly and in combination, a new cerebellar nuclear topographic map has been constructed. This reveals the subdivision of the cerebellar nuclei into at least 12 reproducible expression domains. We hypothesize that such heterogeneity is the counterpart of the zones and stripes of the cerebellar cortex.