Differential distribution of MAP1a and aldolase c in adult mouse cerebellum

Redefining the cerebellar cortex as an assembly of non-uniform Purkinje cell microcircuits

The adult mammalian cerebellar cortex is generally assumed to have a uniform cytoarchitecture. Differences in cerebellar function are thought to arise primarily through distinct patterns of input and output connectivity rather than as a result of variations in cortical microcircuitry. However, evidence from anatomical, physiological and genetic studies is increasingly challenging this orthodoxy, and there are now various lines of evidence indicating that the cerebellar cortex is not uniform. Here, we develop the hypothesis that regional differences in properties of cerebellar cortical microcircuits lead to important differences in information processing.

Reversal of the expression pattern of Aldolase C mRNA in Purkinje cells and Ube 1x mRNA in Golgi cells by a dopamine D1 receptor agonist injections in the methamphetamine sensitized-rat cerebellum

The cerebellum has a parasagittal modular structure, in which Zebrin (Aldolase) positive and negative bands expressed in Purkinje cell layers alternate, and is involved in amphetamine psychosis. Administration of SKF38393, a D1 receptor agonist, reversed the behavioral sensitization of methamphetamine. In the vermis, there were the binding sites of SKF38393. In methamphetamine-sensitized rats the expression of the Aldolase mRNA positive bands move laterally in the rat vermis. We provide here the evidence that the D1 agonist injections also reversed the expression pattern of both the Aldolase mRNA in Purkinje cells and Ube (ubiquitin activating enzyme) 1x mRNA in Golgi interneurons of the sensitized rats. Thus the reverse changes in gene expression pattern in the vermis may be involved in the mechanisms of the behavioral plasticity and suggests the new treatment of drug abuse.

Activity-driven dendritic remodeling requires microtubule-associated protein 1A

Activity-prompted dendritic remodeling leads to calcium-influx-dependent activation of signaling pathways within minutes and gene transcription within hours. However, dendrite growth continues for days and requires extension and stabilization of the cytoskeleton in nascent processes. In addition to binding microtubules, microtubule-associated proteins (MAPs) associate with the actin cytoskeleton, anchor ion channels and signaling complexes, and modulate synaptic growth. MAP2 is predominantly dendritic. MAP1B is at postsynaptic densities (PSD) and modulates ion channel activity, in addition to affecting axon growth. Less is known about MAP1A, but it is also enriched in dendrites at input locations, including PSDs where MAP1A associates with channel complexes and the calcium sensor caldendrin. MAP1A rescued hearing loss in tubby mice. Here we show that MAP1A becomes enriched in dendrites concurrently with dendritic branching and synapse formation in the developing brain; that synaptic activity is required for establishing mature MAP1A expression levels; and that MAP1A expression is required for activity-dependent growth, branching, and stabilization of the dendritic arbor.

Overexpression of heat shock proteins in pallido-nigral axonal spheroids of nonhuman aged primates

The occurrence of spheroids has been described in the globus pallidus (GP) and substantia nigra pars reticulata (SNr) of aged rhesus monkeys. Opinions vary as to the origin of spheroids. Ultrastructural and immunohistochemical analysis suggested that spheroids originate from degenerating axons or astroglia. In the present study, we have investigated the GP and SNr of aged monkeys (Macaca fascicularis and Macaca mulatta). Although immunoreactive for microtubule-associated protein (MAP) 1A, tau, amyloid precursor protein, synaptophysin and phosphorylated neurofilament, spheroids were not immunoreactive for MAP1B and MAP2. We confirmed the axonal nature of pallido-nigral spheroids in aged rhesus monkeys. Pallido-nigral spheroids have been reported to overexpress stress proteins, such as ubiquitin, alphaB-crystallin, and heat shock protein (Hsp) 27. We further evaluated the expression of Hsps in pallido-nigral spheroids. As well as being intensely immunoreactive for ubiquitin, alphaB-crystallin, Hsp27, and Hsp70, spheroids were immunoreactive for Hsp32 (heme oxygenase-1), Hsp40, Hsp60, and Hsp90. On the basis of these findings, we speculate that Hsp32-immunoreactive spheroids might be expressed as an oxidative stress response. Induction of other Hsps might play a role in protection of axons from the aggregation of neurofilament, MAPs and other proteins, and failure to protect degenerating axons might result in their proteolysis by the ubiquitin-proteasome system.

Differential distribution of MAP1A isoforms in the adult mouse barrel cortex and comparison with the serotonin 5-HT2A receptor

Microtubule-associated protein 1A (MAP1A) is essential during the late differentiation phase of neuronal development. Here, we demonstrated the presence of two MAP1A isoforms with a differential spatial distribution in the adult mouse barrel cortex. Antibody A stained MAP1A in pyramidal and stellate cells, including dendrites that crossed layer IV in the septa between barrels. The other antibody, BW6 recognized a MAP1A isoform that was mainly confined to the barrel hollow and identified smaller caliber dendrites. Previously, an interaction of MAP1A and the serotonin 5-hydroxytryptamine 2A (5-HT(2A)) receptor was shown in the rat cortex. Here, we identified, by double-immunofluorescent labeling, MAP1A isoform and serotonin 5-HT(2A) receptor distribution. MAP1A co-localized mainly with 5-HT(2A) receptor in larger apical dendrites situated in septa. This differential staining of MAP1A and a serotonin receptor in defined barrel compartments may be due to changes in the expression or processing of MAP1A during dendritic transport as a consequence of functional differences in processing of whisker-related sensory input.

Selective changes in the shapes of parasagittal bands of Aldoc (Zebrin) mRNA in the rat vermis of the cerebellum after repeated methamphetamine injections

In the cerebellum the mossy and climbing projections, which excite Purkinje cells, display a parasagittal and striped organization. These projections also excite Zebrin (aldolase C: Aldoc) parasagittally. To evaluate the possibility that external stimuli can change the organization of the bands of Aldoc mRNA, we compared the effects of repeated methamphetamine administration on the Aldoc mRNA stripes in the four transverse (anterior, central, posterior and nodular) regions of the vermis with the effects on the glutamate transporter EAAT4 (SCL1A 6) mRNA stripes. In the posterior region the injections four times daily increased the fragmentation of the Aldoc mRNA stripes. The presence of a large amount of fragmentation (forty/cerebellum slice), was accompanied with large lateral dislocations of the Aldoc mRNA stripes. In the central and nodular regions, where the size of the stripe areas decreased significantly the stripes were dislocated laterally. The dislocations of the Aldoc mRNA bands did not occur after a single methamphetamine injection and thus repeated injections were necessary to change the distributions of the lateral bands. In contrast, the distributions of the SCL1A 6 mRNA stripes did not change, even though there was mild fragmentation (six/slice) of the SLC1A 6 mRNA stripes in the anterior region and decreases in the numbers (twelve/slice) in the nodular region. We concluded that excess dopamine selectively changes the location of the Aldoc mRNA compartments in the vermis while the SLC1A 6 mRNA stripes could be changed by other inputs and thus the specific transmitter system might change the specific compartment of the cerebellum.

Expression of the immunoglobulin superfamily neuroplastin adhesion molecules in adult and developing mouse cerebellum and their localisation to parasagittal stripes

Neuroplastin (np) 55 and 65 are immunoglobulin superfamily members that arise by alternative splicing of the same gene and have been implicated in long-term activity-dependent synaptic plasticity. Both biochemical and immunocytochemical data suggest that np55 is the predominant isoform (>95% of total neuroplastin) in cerebellum. Neuroplastin immunoreactivity is concentrated in the molecular layer and synaptic glomeruli in the granule cell layer. Expression in the molecular layer appears to be postsynaptic. First, neuroplastin is associated with Purkinje cell dendrites in two mouse granuloprival cerebellar mutants, disabled and cerebellar deficient folia. Second, in an acid sphingomyelinase knockout mouse with widespread protein trafficking defects, neuroplastin accumulates in the Purkinje cell somata. Finally, primary cerebellar cultures show neuroplastin expression in Purkinje cell dendrites and somata lacking normal histotypic organization and synaptic connections, and high-magnification views indicate a preferential association with dendritic spines. In the molecular layer, differences in neuroplastin expression levels present as a parasagittal array of stripes that alternates with that revealed by the expression of another compartmentation antigen, zebrin II/aldolase c. Neuroplastin immunoreactivity is first detected weakly at postnatal day 3 (P3) in the anterior lobe vermis. By P5, parasagittal stripes are already apparent in the immature molecular layer. At this stage, punctate deposits are also localised at the perimeter of the Purkinje cell perikarya; these are no longer detected by P15. The data suggest a role for neuroplastins in the development and maintenance of normal synaptic connections in the cerebellum.

Selective changes in the neurofilament and microtubule cytoskeleton of NF-H/LacZ mice

This study focused mainly on changes in the microtubule cytoskeleton in a transgenic mouse where beta-galactosidase fused to a truncated neurofilament subunit led to a decrease in neurofilament triplet protein expression and a loss in neurofilament assembly and abolished transport into neuronal processes in spinal cord and brain. Although all neurofilament subunits accumulated in neuronal cell bodies, our data suggest an increased solubility of all three subunits, rather than increased precipitation, and point to a perturbed filament assembly. In addition, reduced neurofilament phosphorylation may favor an increased filament degradation. The function of microtubules seemed largely unaffected, in that tubulin and microtubule-associated proteins (MAP) expression and their distribution were largely unchanged in transgenic animals. MAP1A was the only MAP with a reduced signal in spinal cord tissue, and differences in immunostaining in various brain regions corroborate a relationship between MAP1A and neurofilaments.

Pattern formation in the cerebellar cortex

The cerebellar cortex is subdivided rostrocaudally and mediolaterally into a reproducible array of zones and stripes. This makes the cerebellum a valuable model for studying pattern formation in the vertebrate central nervous system. The structure of the adult mouse cerebellar cortex and the series of embryological events that generate the topography are reviewed.Key words: zebrin, Hsp25, Purkinje cells.

Different dystrophin-like complexes are expressed in neurons and glia

Duchenne muscular dystrophy is a fatal muscle disease that is often associated with cognitive impairment. Accordingly, dystrophin is found at the muscle sarcolemma and at postsynaptic sites in neurons. In muscle, dystrophin forms part of a membrane-spanning complex, the dystrophin-associated protein complex (DPC). Whereas the composition of the DPC in muscle is well documented, the existence of a similar complex in brain remains largely unknown. To determine the composition of DPC-like complexes in brain, we have examined the molecular associations and distribution of the dystrobrevins, a widely expressed family of dystrophin-associated proteins, some of which are components of the muscle DPC. beta-Dystrobrevin is found in neurons and is highly enriched in postsynaptic densities (PSDs). Furthermore, beta-dystrobrevin forms a specific complex with dystrophin and syntrophin. By contrast, alpha-dystrobrevin-1 is found in perivascular astrocytes and Bergmann glia, and is not PSD-enriched. alpha-Dystrobrevin-1 is associated with Dp71, utrophin, and syntrophin. In the brains of mice that lack dystrophin and Dp71, the dystrobrevin-syntrophin complexes are still formed, whereas in dystrophin-deficient muscle, the assembly of the DPC is disrupted. Thus, despite the similarity in primary sequence, alpha- and beta-dystrobrevin are differentially distributed in the brain where they form separate DPC-like complexes.

Microtubule-associated protein 1a is involved in the early development of the rat spinal cord

The expression of microtubule-associated protein 1a (MAP1a) in the developing rat spinal cord was studied using the monoclonal antibody BW6. Immunoblots of microtubule preparations revealed the presence of MAP1a in spinal cord tissue of rats aged embryonal day 16 and postnatal day 0. The spinal cord matrix layer, between embryonal days 12-17, displayed a pattern of MAP1a-positive processes, horizontally oriented in between the membrane limitans interna and externa. The mantle layer stained intensely for MAP1a between embryonal day 12 and postnatal day 2. MAP1a was found in neuronal cell bodies, axons and dendrites, located mainly in the ventral and intermediate mantle layer. In the marginal layer, MAP1a-positive axons could be observed between embryonal days 14-18. During further development, the intensity of the MAP1a staining in the spinal columns gradually decreased. These expression patterns indicate an involvement of MAP1a in the proliferation and differentiation of neuroblasts, and the maturation of the long spinal fiber systems, i.e. early events in spinal cord development

Aldolase C/zebrin II and the regionalization of the cerebellum

The cerebellum is comprised of multiple bands of cells, each with characteristic afferent and efferent projections, and patterns of gene expression. The most studied example of a striped pattern of expression is the antigen recognized by monoclonal antibody antizebrin II. Zebrin II is expressed by subsets of Purkinje cells that form an array of parasagittal bands that extend rostrocaudally throughout the cerebellar cortex, separated by similar bands of Purkinje cells that do not express zebrin II. Recent cloning studies have revealed that the zebrin II antigen is the respiratory isoenzyme aldolase C. This article reviews the cellular and molecular compartmentation of the cerebellum together with the molecular biology of the aldolase C gene, and speculates on possible reasons for a striped pattern of expression.