Differential expression of calretinin, calbindin D28K and parvalbumin in the developing human cerebellum

Time course and expression pattern of the neuronal markers in the developing human spinal cord

The aim of this study was to examine the spatio-temporal appearance of different neuronal cell subtypes by analyzing expression patterns of several neuronal markers (calretinin, neurofilament 200 (NF200), vanilloid receptor 1(VR1) and calcitonin gene-related peptide (CGRP)) of the embryonic human spinal cord (SC). Developing human SCs from 11 human conceptuses beetwen 5-10 developmental weeks (DW) were examined by light and electron microscopy and immunofluorescence. Light and electron microscopy revealed different embryonic stages of recognizable structure of the SC. NF200, CGRP and VR1 positive cells were observed in SCs during 5th-6th DW. NF200 was predominantly expressed in the ventral part, indicating presence of motoneurons. As development advanced, NF200 was mainly expressed in the marginal zone. Expression of CGRP was intense during all of the investigated periods, predominantly during the 5th-6th DW pointing to neural sensory differentiation, as opposed to the last DW when reduced expression of CGRP in the marginal layer indicated the terminations of the sensory afferents. Expression of VR1 was highest in the intermediate zone, at the beginning and at the end of the investigated periods, pointing to VR1 spatial pattern in the visceral afferents in the grey matter, while the first signs of calretinin were found in the 9th-10th DW ventrally. Delineating the relationships between factors involved in processes of neuronal differentiation as well as spatial and temporal arrangement of SC interrelated neurons can provide a useful information about normal SC development as well as the insight in possible causes of anomalies and disorders during embryonic life.

Antioxidant supplementation upregulates calbindin expression in cerebellar Purkinje cells of rat pups subjected to post natal exposure to sodium arsenite

Optimal cytoplasmic calcium (Ca²⁺) levels have been associated with adequate cell functioning and neuronal survival. Altered intracellular Ca²⁺ levels following impaired Ca²⁺ homeostasis could induce neuronal degeneration or even cell death. There are reports of arsenite induced oxidative stress and the associated disturbances in intracellular calcium homeostasis. The present study focused on determining the strategies that would modulate tissue redox status and calcium binding protein (CaBP) (Calbindin D28k-CB) expression affected adversely by sodium arsenite (NaAsO₂) exposure (postnatal) of rat pups. NaAsO₂ alone or along with antioxidants (AOXs) (alpha lipoic acid or curcumin) was administered by intraperitoneal (i.p.) route from postnatal day (PND) 1-21 (covering rapid brain growth period - RBGP) to experimental groups and animals receiving sterile water by the same route served as the controls. At the end of the experimental period, the animals were subjected to euthanasia and the cerebellar tissue obtained therefrom was processed for immunohistochemical localization and western blot analysis of CB protein. CB was diffusely expressed in cell body as well as dendritic processes of Purkinje cells (PCs) along the PC Layer (PCL) in all cerebellar folia of the control and the experimental animals. The multilayered pattern of CB +ve cells along with their downregulated expression and low packing density was significantly evident in the arsenic (iAs) alone exposed group as against the controls and AOX supplemented groups. The observations are suggestive of AOX induced restoration of CaBP expression in rat cerebellum following early postnatal exposure to NaAsO₂.

Normal Development of the Perineuronal Net in Humans; In Patients with and without Epilepsy

The perineuronal net (PN), a highly organized extracellular matrix structure, is believed to play an important role in synaptic function, including maturation and stabilization. In addition to its role in restricting plasticity, alterations in the PN are implicated in disorders such as epilepsy and schizophrenia. However, the time course of PN development is not known in humans. Therefore we set out to document the developmental timeline of the PN formation in humans in 14 frontal and hippocampal specimens from donors aged 27 days to 31 years old. Using immunohistochemistry and western blotting, we demonstrate that the PN begins to form as early as the second month of life but does not reach its robust, mature appearance until around 8 years of age, though aggrecan cleavage products are observed prior to this. A similar developmental time course was observed in specimens from epilepsy patients. Our data suggest that aggrecan is present early in development but the structured PN develops throughout early childhood, similar to what has been observed in rodents. This timeline provides information for future pathological studies on the role of the PN in disease and an additional parallel between human and rodent development.

Cerebellar networks and neuropathology of cerebellar developmental disorders

The cerebellar system is a series of axonal projections and synaptic circuits as networks, similar to those of the limbic system and those subserving the propagation and spread of seizures. Three principal cerebellar networks are identified and cerebellar disease often affects components of the networks other than just the cerebellar cortex. Contemporary developmental neuropathology of the cerebellum is best considered in the context of alterations of developmental processes: embryonic segmentation and genetic gradients along the three axes of the neural tube, individual neuronal and glial cell differentiation, migration, synaptogenesis, and myelination. Precisely timed developmental processes may be delayed or precocious rhombencephalosynapsis and pontocerebellar hypoplasia exemplify opposite gradients in the horizontal axis. Chiari II malformation may be reconsidered as a disorder of segmentation rather than simply due to mechanical forces upon normally developing hindbrain structures. Cellular nodules in the roof of the fourth ventricle are heterotopia of histologically differentiated but architecturally disoriented and disorganized neurons and glial cells; they often are less mature immunocytochemically than similar cells in adjacent normal folia. Cell rests are nodules of undifferentiated neuroepithelial cells. Both are frequent in human fetuses and neonates. Axonal projections from heterotopia to adjacent cerebellar folia or nuclei are few or absent, hence these nodules are clinically silent despite neuronal differentiation.

The distribution of calbindin-D28k, parvalbumin, and calretinin immunoreactivity in the inferior colliculus of circling mouse

The circling mice with tmie gene mutation are known as an animal deafness model, which showed hyperactive circling movement. Recently, the reinvestigation of circling mouse was performed to check the inner ear pathology as a main lesion of early hearing loss. In this trial, the inner ear organs were not so damaged to cause the hearing deficit of circling (cir/cir) mouse at 18 postnatal day (P18) though auditory brainstem response data indicated hearing loss of cir/cir mice at P18. Thus, another mechanism may be correlated with the early hearing loss of cir/cir mice at P18. Hearing loss in the early life can disrupt the ascending and descending information to inferior colliculus (IC) as integration site. There were many reports that hearing loss could result in the changes in Ca²⁺ concentration by either cochlear ablation or genetic defect. However, little was known to be reported about the correlation between the pathology of IC and Ca²⁺ changes in circling mice. Therefore, the present study investigated the distribution of calcium-binding proteins (CaBPs), calbindin-D28k, parvalbumin, and calretinin immunoreactivity (IR) in the IC to compare among wild-type (+/+), heterozygous (+/cir), and homozygous (cir/cir) mice by immunohistochemistry. The decreases of CaBPs IR in cir/cir were statistically significant in the neurons as well as neuropil of IC. Thus, this study proposed overall distributional alteration of CaBPs IR in the IC caused by early hearing defect and might be helpful to elucidate the pathology of central auditory disorder related with Ca²⁺ metabolism.

Immunoreactivity pattern of calretinin in the developing human cerebellar cortex

The immunohistochemical expression of the calcium-binding protein calretinin during human cerebellar development has been investigated in this study. Human cerebellum samples, obtained from 7 fetuses and newborns ranging from 11 to 38 weeks of gestation, were 10% formalin-fixed, routinely processed and paraffin-embedded. 3μm-tick sections were immunostained with an anti-calretinin antibody. Our study evidenced a different immunoreactivity for calretinin in Purkinje cells and in several cerebellar interneurons at different intrauterine developmental stages. Whereas at 11 weeks of gestation calretinin immunoreactivity was not detected in the developing cerebellum, from the 18th to the 24th week, calretinin expression was found in Purkinje cells migrating from the ventricular neuroepithelium and in migrating cerebellar interneurons. From the 30th to the 38th week, calretinin was expressed by most of Purkinje cells and by migrating cerebellar interneurons. Furthermore, granule cells in the internal granular layer were also immunoreactive for calretinin. Our data show that calretinin, other than for developing Purkinje cells, is a useful marker also for migrating cerebellar interneurons and for some neuronal elements related to the granular layer. Moreover, given the critical role of calcium in a great variety of neuronal processes in the central nervous system, our findings suggest that calretinin may play a pivotal role in the regulation of neuronal excitability during intrauterine cerebellar development.

Embryonic and postnatal development of calcium-binding proteins immunoreactivity in the anterior thalamus of the guinea pig

Our recent studies have shown that the distribution of calretinin (CR) in the anterior thalamic nuclei (ATN) changes significantly during the development of the guinea pig. The present study was designed to reveal the distribution pattern of calcium-binding proteins, i.e. calbindin (CB) and parvalbumin (PV), as well as the colocalization pattern of all three proteins, including CR, in the ATN of guinea pigs ranging from the 40th embryonic day (E40) to the 80th postnatal day (P80). According to these patterns, CB appears exclusively in the perikarya of the anteromedial nucleus (AM) not before P20 and always colocalizes with CR. Moreover, CB and CR colocalize in fibers of thin bundles traversing the anteroventral nucleus (AV) since E50. The ATN also display CB-positive neuropil in all studied stages, especially a strong one in the ventral part of the AV. PV was not observed in the perikarya of the ATN in all the stages, but was abundantly present in the neuropil of the anterodorsal nucleus (AD). No colocalizations exist between PV and the rest of the studied proteins. In conclusion, our study reveals that the distribution of the studied proteins differs greatly. Nevertheless, the postnatal coexistence of CB and CR in the AM perikarya may indicate the cooperation of both of the proteins in some functions of the nucleus. Parvalbumin is limited mostly to the neuropil of the AD, suggesting different functions in comparison to CB and CR.

Clinical neuropathology practice guide 5-2013: markers of neuronal maturation

This review surveys immunocytochemical and histochemical markers of neuronal lineage for application to tissue sections of fetal and neonatal brain. They determine maturation of individual nerve cells as the tissue progresses to mature architecture. From a developmental perspective, neuronal markers are all about timing. These diverse cellular labels may be classified in two ways: 1) time of onset of expression (early; intermediate; late); 2) labeling of subcellular structures or metabolic functions (nucleoproteins; synaptic vesicle proteins; enolases; cytoskeletal elements; calcium-binding; nucleic acids; mitochondria). Apart from these positive markers of maturation, other negative markers are expressed in primitive neuroepithelial cells and early stages of neuroblast maturation, but no longer are demonstrated after initial stages of maturation. These examinations are relevant for studies of normal neuroembryology at the cellular level. In fetal and perinatal neuropathology they provide control criteria for application to malformations of the brain, inborn metabolic disorders and acquired fetal insults in which neuroblastic maturation may be altered. Disorders, in which cells differentiate abnormally, as in tuberous sclerosis and hemimegalencephaly, pose another yet aspect of mixed cellular lineage. The measurement in living patients, especially neonates, of serum and CSF levels of enolases, chromogranins and S-100 proteins as biomarkers of brain damage may potentially be correlated with their corresponding tissue markers at autopsy in infants who do not survive. The neuropathological markers here described can be performed in ordinary hospital laboratories, not just research facilities, and offer another dimension of diagnostic precision in interpreting abnormally developed fetal and postnatal brains.

Neuroprotective effect of ginseng against alteration of calcium binding proteins immunoreactivity in the mice hippocampus after radiofrequency exposure

Calcium binding proteins (CaBPs) such as calbindin D28-k, parvalbumin, and calretinin are able to bind Ca²⁺ with high affinity. Changes in Ca²⁺ concentrations via CaBPs can disturb Ca²⁺ homeostasis. Brain damage can be induced by the prolonged electromagnetic field (EMF) exposure with loss of interacellular Ca²⁺ balance. The present study investigated the radioprotective effect of ginseng in regard to CaBPs immunoreactivity (IR) in the hippocampus through immunohistochemistry after one-month exposure at 1.6 SAR value by comparing sham control with exposed and ginseng-treated exposed groups separately. Loss of dendritic arborization was noted with the CaBPs in the Cornu Ammonis areas as well as a decrease of staining intensity of the granule cells in the dentate gyrus after exposure while no loss was observed in the ginseng-treated group. A significant difference in the relative mean density was noted between control and exposed groups but was nonsignificant in the ginseng-treated group. Decrease in CaBP IR with changes in the neuronal staining as observed in the exposed group would affect the hippocampal trisynaptic circuit by alteration of the Ca²⁺ concentration which could be prevented by ginseng. Hence, ginseng could contribute as a radioprotective agent against EMF exposure, contributing to the maintenance of Ca²⁺ homeostasis by preventing impairment of intracellular Ca²⁺ levels in the hippocampus.

Pattern of calbindin-D28k and calretinin immunoreactivity in the brain of Xenopus laevis during embryonic and larval development

The present study represents a detailed spatiotemporal analysis of the localization of calbindin-D28k (CB) and calretinin (CR) immunoreactive structures in the brain of Xenopus laevis throughout development, conducted with the aim to correlate the onset of the immunoreactivity with the development of compartmentalization of distinct subdivisions recently identified in the brain of adult amphibians and primarily highlighted when analyzed within a segmental paradigm. CR and CB are expressed early in the brain and showed a progressively increasing expression throughout development, although transient expression in some neuronal subpopulations was also noted. Common and distinct characteristics in Xenopus, as compared with reported features during development in the brain of mammals, were observed. The development of specific regions in the forebrain such as the olfactory bulbs, the components of the basal ganglia and the amygdaloid complex, the alar and basal hypothalamic regions, and the distinct diencephalic neuromeres could be analyzed on the basis of the distinct expression of CB and CR in subregions. Similarly, the compartments of the mesencephalon and the main rhombencephalic regions, including the cerebellum, were differently highlighted by their specific content in CB and CR throughout development. Our results show the usefulness of the analysis of the distribution of these proteins as a tool in neuroanatomy to interpret developmental aspects of many brain regions.

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.

Evidence for tangential migration disturbances in human lissencephaly resulting from a defect in LIS1, DCX and ARX genes

During corticogenesis, neurons adopt different migration pathways to reach their final position. The precursors of pyramidal neurons migrate radially, whereas most of the GABA-containing interneurons are generated in the ventral telencephalon and migrate tangentially into the neocortex. Then, they use a radial migration mode to establish themselves in an inside-out manner in the neocortex, similarly to pyramidal neurons. In humans, the most severe defects in radial migration result in lissencephaly. Lately, a few studies suggested that lissencephaly was also associated with tangential neuronal migration deficits. In the present report, we investigated potential anomalies of this migration mode in three agyric/pachygyric syndromes due to defects in the LIS1, DCX and ARX genes. Immunohistochemistry was performed on paraffin-embedded supra- and infratentorial structures using calretinin, calbindin and parvalbumin antisera. The results were compared with age-matched control brain tissue. In the Miller-Dieker syndrome, GABAergic neurons were found both in upper layers of the cortex and in heterotopic positions in the intermediate zone and in ganglionic eminences. In the DCX mutant brain, few interneurons were dispersed in the cortical plate, with a massive accumulation in the intermediate zone and subventricular zone as well as in the ganglionic eminences. In the ARX-mutated brain, the cortical plate contained almost exclusively pyramidal cells and was devoid of interneurons. The ganglionic eminences and basal ganglia were poorly cellular, suggesting an interneuron production and/or differentiation defect. These data argue for different mechanisms of telencephalic tangential migration impairment in these three agyric/pachygyric syndromes.

Hemimegalencephaly: a fetal case with neuropathological confirmation and review of the literature

Hemimegalencephaly (HME) is a developmental abnormality of the central nervous system, identified by an abnormal increase in the size of one cerebral hemisphere. HME may present as either a syndromic or isolated case. To date the literature on HME has focused primarily on non-fetal pediatric patients, largely related to surgical resection specimens of the HME hemisphere. We present the case of a male fetus at 22 weeks gestation with intracranial abnormalities identified on a follow-up ultrasound. Gross examination of the fetal brain confirmed the increased size of the right cerebral hemisphere. The ipsilateral brain stem and cerebellum were not involved. Light microscopy demonstrated the presence of accelerated cortical differentiation along with several migrational anomalies in the HME hemisphere. Based on the gross and microscopic findings, a diagnosis of fetal hemimegalencephaly was made. The periventricular proliferative zone of the abnormal hemisphere contained a normal population of neuroepithelial precursor cells. An exhaustive immunohistochemical study found immunoreactivity for calretinin and synaptophysin, while the Ki-67 proliferation labeling was not increased in the HME hemisphere. Our case is the first autopsied report on fetal hemimegalencephaly and confirms that the key pathogenic changes may present as early as 20-22 weeks gestation. The major pathological features of our case are in keeping with a disturbance in accelerated neuronal differentiation and migrational abnormalities.

Calbindin D28k expression and the absence of apoptosis in the cerebellum of Solanum bonariense L-intoxicated bovines

Solanum bonariense intoxication is characterized by cerebellar neuronal vacuolation, degeneration, and necrosis. Cerebellar Purkinje cells seem especially susceptible, but more research is needed to determine the pathogenesis of neuronal necrosis and the mechanism of Purkinje cell susceptibility. Calbindin D28k (CbD28k) is highly expressed in Purkinje cells and has been used as a marker for normal and degenerative Purkinje cells. The goal of this study was to describe S bonariense-induced disease by ascertaining Purkinje cell-specific degenerative changes using CbD28k expression and to correlate this with apoptosis in Purkinje cells, as determined using TUNEL (transferase-mediated dUTP-biotin nick end-labeling) and ultrastructural changes. In all cases, an increase in both dose and duration of S bonariense intoxication resulted in a decrease in the number of Purkinje cells. CbD28k immunohistochemistry was an excellent marker for Purkinje cells because immunoreactivity did not change in normal or degenerative tissues. This finding suggests that excessive calcium excitatory stimulation does not induce rapid neuronal degeneration and death. As found in previous studies, TUNEL tests and electron microscopy suggest that Purkinje cell degeneration and death are not occurring via an apoptotic process. These findings suggest that S bonariense poisoning induces progressive Purkinje cell death that is not mediated by excitotoxicity or apoptotic activation.

Origin of adenohypophysial lobes and cells from Rathke's pouch in Swiss albino mice. Proliferation and expression of Pitx 2 and Calbindin D28K in corticotropic and somatotropic cell differentiation

A developmental study of the adenohypophysis of the mouse was carried out in response to several as yet unanswered questions about its organogenesis and differentiation. The main objectives were to establish the origin of adenohypophysial lobes and cells from the Rathke's pouch (RP) and elucidate the mechanisms of development and functional differentiation of the gland. Using diverse techniques, the morphological development, proliferation and differentiation were studied in order to delimit different proliferative regions in the RP, and provide a satisfactory explanation for the distribution of each cell type in the adult gland. Combining the proliferation and differentiation studies, corticotropic and somatotropic cells appear to mainly originate from undifferentiated precursors located within each of these proliferative regions. The involvement of transcription factor Pitx 2 and calcium-binding protein Calbindin D 28K in the differentiation of corticotropic and somatotropic cells is further clarified.

Origin of adenohypophysial lobes and cells from Rathke's pouch in chicken (Gallus gallus) and Japanese quail (Coturniz coturniz japonica). Expression of calcium-binding proteins

A histological and immunochemical study of adenohypophysis development in two bird species: chicken (Gallus gallus) and Japanese quail (Coturnix coturnix japonica) was carried out, focussing firstly morphologically on the origin of its different lobes, then secondly on the differentiation of hormone-producing cells from the adenohypophysial anlage and their involvement in the differentiation of three calcium-binding proteins. The results of the morphological development study show how the origin of the adenohypophysis in chicken is totally ectodermic, whilst in Japanese quail the endoderm, in the form of Sessel's pouch, participates in forming the rostral zone of the anterior lobe. After studying the organogenesis and spatio/temporal differentiation of the hormone-producing cells proceeding from the adenohypophysial anlage, a regionalization model is proposed for the origin of the different lobes and cell types as well as time sequence, fundamentally the origin of cell regionalization in the adult adenohypophysis. In this process, at least in the two bird species studied, the results obtained from expressing the calcium-binding proteins, calbindin D 28K, calretinin and parvalbumin show a characteristic distribution pattern for each, suggesting distinct functions.

Cyto- and Chemoarchitecture of the Cerebellum of the Short-Beaked Echidna (Tachyglossus aculeatus)

The monotremes (echidnas and platypus) have been claimed by some authors to show 'avian' or 'reptilian' features in the gross morphology and microscopic anatomy of the cerebellum. We have used Nissl staining in conjunction with enzyme histochemistry to acetylcholinesterase and cytochrome oxidase and immunohistochemistry to non-phosphorylated neurofilament protein (SMI-32 antibody), calcium binding proteins (parvalbumin, calbindin and calretinin) and tyrosine hydroxylase to examine the cyto- and chemoarchitecture of the cerebellar cortex and deep cerebellar nuclei in the short-beaked echidna. Immunoreactivity for non-phosphorylated neurofilament (SMI-32 antibody) was found in the deep cerebellar nuclei and in Purkinje cells of most regions except the nodule. Purkinje cells identified with SMI-32 immunoreactivity were clearly mammalian in morphology. Parvalbumin and calbindin immunoreactivity was found in Purkinje cells with some regional variation in staining intensity and in Purkinje cell axons traversing cerebellar white matter or terminating on Lugaro cells. Calbindin immunoreactivity was also present in inferior olivary complex neurons. Calretinin immunoreactivity was found in pontocerebellar fibers and small cells in the deep granule cell layer of the ansiform lobule. We found that, although the deep cerebellar nuclei were much less clearly demarcated than in the rodent cerebellum, it was possible to distinguish medial, interposed and lateral nuclear components in the echidna. As far as we can determine from our techniques, the cerebellum of the echidna shows all the gross and cytological features familiar from the cerebellum of therian mammals.

Calretinin‐immunoreactive unipolar brush cells in the developing human cerebellum

We have studied the temporal and spatial characteristics of the development of unipolar brush cells (UBCs) in the human cerebellar vermis. Consistently with previous studies in rodents and cat, we have found that unipolar brush cells appear at a relatively late phase of cerebellar development and their development continues up to and beyond the first postnatal year. A series of 23 normal human brains, including 5 adult and 18 fetal or infant brains (between the 24th gestational week and the 11th postnatal month) were used. In order to visualize unipolar brush cells, calretinin-immunocytochemistry was performed on formaldehyde-fixed, paraffin-embedded blocks of the cerebellar vermis. Our results show that calretinin-immunoreactive unipolar brush cells are not yet present in the cerebellar vermis at the 28th gestational week. At birth, they are present in a relatively small number, mostly in the vestibular lobules. At the 3rd, 5th, 8.5th and 11th postnatal months the number of calretinin-immunoreactive unipolar brush cells gradually increase, first appearing in the vestibular lobules, followed by the invasion of the later developing vermal lobules, spreading in a rostro-caudal and proximo-distal direction. Although at the 11th postnatal month unipolar brush cells exhibited adult-like morphological and distributional features, their number appeared to be lower than in the adult cerebellum. The late maturation of unipolar brush cells implies that the cytoarchitectonical development of the human cerebellum is not completed by the end of the first postnatal year.

Expression of MATH1, a marker of cerebellar granule cell progenitors, identifies different medulloblastoma sub-types

In order to look for genetic markers helpful for the biological risk stratification of medulloblastomas (MBs) we assayed by real-time PCR expression levels of the following genes: MATH1, encoding a critical transcription factor for the differentiation of cerebellar granular cells (CGCs); PEDF, that encodes a trophic factor for CGCs and is located in a region of frequent allelic imbalance in MBs; and BIRC5, encoding the antiapoptotic protein survivin, usually overexpressed in malignancies. Expression levels of TRKC, higher in MBs with a more favorable prognosis, were also studied. Twenty-three patients were considered: MATH1 expression was strong in 14/23 and undetectable in the others. PEDF was up-regulated in 8/23, TRKC in 9/23, and BIRC5 in 23/23. MATH1 expression was significantly correlated with adult age (p < 0.0001), tumor location in hemispheres rather than the vermis (p < 0.0004), and PEDF and TRKC up-regulation (p < 0.008 and p < 0.04, respectively). During development MATH1 is selectively expressed in the external germinal layer (EGL) of the cerebellum. Thus, MATH1 expression identifies a subgroup of MBs that derive from the EGL and arise during adult age into cerebellar hemispheres. MATH1 mRNA-positive MBs express high levels of PEDF and show a trend towards longer survival, in agreement with increased expression of TRKC. BIRC5 expression, which is strong in all MBs and absent in normal cerebellum, lacks any prognostic value but could be explored for selective targeting of therapeutic factors to MBs.

Ontogeny of two calcium-binding proteins (calbindin D-28K and parvalbumin) in the human inferior olivary complex and their distribution in the adults

The inferior olivary complex (IOC) is a prominent nuclear relay system of the medulla oblongata. Anatomically, it is connected to the cerebellum for coordination of motor activities. Calbindin D-28K (CALB) and parvalbumin (PV) are cytosolic calcium-binding proteins (CBP) that play a role in Ca2+ homeostasis. We examined their ontogeny and distribution in the fetal, postnatal and adult human IOC by immunohistochemistry. At 11-12 weeks of gestation (wg), calbindin immunoreactivity was present in the principal olive and the medial accessory olive, it was absent in the dorsal olive. Parvalbumin immunoreactivity developed at 16-17 wg in the ventral lamella and the lateral bulge of the principal olive only. Calbindin expression gradually increased from 20 to 37 wg, whilst by contrast, parvalbumin expression was moderate. By 37 wg, all three IOC subnuclei were immunopositive for both proteins. In a 3-month-old infant, parvalbumin was intensely developed in the olivary axons. In the adults (40- to 59-year-old), calbindin was distributed in most neurons, and olivocerebellar fibres, whereas parvalbumin was present in some neurons and few fibres. Parvalbumin expressed till 51 years, and disappeared by 59 years of age. Calbindin immunoreactivity in the olivary axons was declined at 70 years of age. The data suggest a differential distribution and requirement of these proteins in the human IOC maturation. It may be that the IOC utilizes mainly calbindin for Ca2+ buffering. The loss of parvalbumin with ageing might influence the excitability of the spared IOC neurons.

The contributions of excitotoxicity, glutathione depletion and DNA repair in chemically induced injury to neurones: exemplified with toxic effects on cerebellar granule cells

Six chemicals, 2-halopropionic acids, thiophene, methylhalides, methylmercury, methylazoxymethanol (MAM) and trichlorfon (Fig. 1), that cause selective necrosis to the cerebellum, in particular to cerebellar granule cells, have been reviewed. The basis for the selective toxicity to these neurones is not fully understood, but mechanisms known to contribute to the neuronal cell death are discussed. All six compounds decrease cerebral glutathione (GSH), due to conjugation with the xenobiotic, thereby reducing cellular antioxidant status and making the cells more vulnerable to reactive oxygen species. 2-Halopropionic acids and methylmercury appear to also act via an excitotoxic mechanism leading to elevated intracellular Ca2+, increased reactive oxygen species and ultimately impaired mitochondrial function. In contrast, the methylhalides, trichlorfon and MAM all methylate DNA and inhibit O6-guanine-DNA methyltransferase (OGMT), an important DNA repair enzyme. We propose that a combination of reduced antioxidant status plus excitotoxicity or DNA damage is required to cause cerebellar neuronal cell death with these chemicals. The small size of cerebellar granule cells, the unique subunit composition of their N-methyl-d-aspartate (NMDA) receptors, their low DNA repair ability, low levels of calcium-binding proteins and vulnerability during postnatal brain development and distribution of glutathione and its conjugating and metabolizing enzymes are all important factors in determining the sensitivity of cerebellar granule cells to toxic compounds.

Differential expression of S100 proteins in the developing human hippocampus and temporal cortex

S100 calcium binding proteins have long been known to express in the adult nervous system, but their distribution in the developing brain, especially the human fetal brain, is largely unknown. We used an immunohistochemical method to determine the expression of three S100 proteins, namely S100A4, S100A5, and S100A13, in the human fetal hippocampus and temporal cortex from 12 to 33 weeks of gestation. At 12 weeks, S100A5 was strongly expressed in the cells and fibers of the polymorphic, pyramidal, and molecular layers of the hippocampus. Thereafter, its expression decreased with age. In the temporal cortex, S100A5 expression was detected from 12 weeks onwards, peaked at 20 to 24 weeks, and then decreased with age. The horizontal fibers of the marginal zone were immunoreactive at all stages examined. S100A13 immunoreactivity was also detected in both cells and fibers of the hippocampus at 12 weeks, became slightly stronger at 20 weeks, and then decreased with age. In the temporal cortex, S100A13 immunoreactivity was also strong in all cellular layers at 12 to 24 weeks before it declined with age from 28 weeks onwards. Among the three proteins examined, S100A4 showed the weakest expression, which was detected in the cells and fibers of the hippocampus and the temporal cortex at all stages examined. Our results have demonstrated for the first time, in the human fetal hippocampus and temporal cortex, specific spatio-temporal patterns of expression of these proteins, all of which are likely to have different roles to play during development despite their pronounced sequence homology.

Distribution of calcium-binding proteins in the cerebellum

Calcium plays a fundamental role in the cell as second messenger and is principally regulated by calcium-binding proteins. Although these proteins share in common their ability to bind calcium, they belong to different subfamilies. They present, in general, specific developmental and distribution patterns. Most Purkinje cells express the fast and slow calcium buffer proteins calbindin-D28k and parvalbumin, whereas basket, stellate and Golgi cells the slow buffer parvalbumin only. They are, almost all, calretinin negative. Granule, Lugaro and unipolar brush cells present an opposite immunoreactivity profile, most of them being calretinin positive while lacking calbindin-D28k and parvalbumin. The developmental pattern of appearance of these proteins seems to follow the maturation of neurons. Calbindin-D28k appears early, shortly after cessation of mitosis when neurons become ready to start migration and differentiation while parvalbumin is expressed later in parallel with an increase in neuronal activity. The other proteins are generally detected later. During development, some of these proteins, like calretinin, are transiently expressed in specific cellular subpopulations. The function of these proteins is not fully understood, although strong evidence supports a prominent role in physiological settings with altered calcium concentrations. These proteins regulate and are regulated by intracellular calcium level. For example, they may directly or indirectly enable sensitization or desensitization of calcium channels, and may further block calcium entry into the cells, like the calcium-sensor proteins, that have been shown to be potent and specific modulators of ion channels, which may allow for feedback control of current function and hence signaling. The absence of calcium buffer proteins results in marked abnormalities in cell firing; with alterations in simple and complex spikes or transformation of depressing synapses into facilitating synapses. Calcium-binding protein implication in resistance to degeneration is still a controversial issue. Neurons rich in calcium-binding proteins, especially calbindin-D28k and parvalbumin, seem to be relatively resistant to degeneration in a variety of acute and chronic disorders. However other data support that an absence of calcium-binding proteins may also have a neuroprotective effect. It is not unlikely that neurons may face a dual action mechanism where a decrease in calcium-binding proteins has a first short-term beneficial effect while it becomes detrimental for the cell over the long term.

Calbindin-d(28k): a marker of recurrence for medulloblastomas

BACKGROUND

The expression of the Ca(2+)-binding protein calbindin-D(28k) was analyzed in medulloblastomas in relation to clinical features and other biologic markers related to cell proliferation, differentiation, p53, and cerebellar developmental regulated gene expression.

METHODS

Immunohistochemistry was carried out on histologic slides from a first retrospective series of 29 nonmetastatic and 10 metastatic medulloblastoma formalin-fixed, paraffin-embedded tissues, using specific antibodies against calbindin-D(28k), calretinin, alpha-parvalbumin and beta-parvalbumin, and S100 proteins. Informed consent was obtained from the subjects and/or guardians. Other biologic markers for differentiation, cell proliferation, the expression of the p53 tumor suppressor gene protein, and cerebellar developmental regulated genes were similarly investigated. A second series of 16 medulloblastomas from young patients (younger than 15 years) was added in order to validate the results obtained in the first series.

RESULTS

Of all the markers investigated, only calbindin-D(28k) was significantly associated with prognosis. Survival and remission (i.e. recurrence free) time analysis performed on all the cases (n = 55) confirmed a high risk of death (P = 0.004) and recurrence (P = 0.003) associated with calbindin-positivity. As calbindin-positivity was predominantly observed in tumors from young patients, the authors confirmed its prognostic value in the subgroup of patients younger than 15 years (n = 37). Cox regression analysis showed a significant and independent prognostic value for calbindin expression and, to a lesser extent, the type of surgery (total or subtotal). Three risk groups were thus identified, distinguishing among the cases characterized by a total resection and calbindin-negativity (good prognosis), by a subtotal resection and calbindin-negativity (intermediary), and by calbindin-positivity (bad prognosis).

CONCLUSIONS

The current study suggests that calbindin-positive medulloblastomas represent a subclass of aggressive tumors more frequently seen in younger patients.

Neuropathologic research strategies in holoprosencephaly

Hypotheses are presented to explain the pathogenesis of several clinical features of holoprosencephaly, and neuropathologic approaches to testing these hypotheses are suggested. The traditional morphologic classification of holoprosencephaly into alobar, semilobar, and lobar forms is grades of severity, and each occurs in all of the genetic mutations known. Of the four defective genes identified as primary in human holoprosencephaly, three exhibit a ventrodorsal gradient of expression (SHH, SIX3, and TGIF) and one a dorsoventral gradient (ZIC2). But, in addition to the vertical axis, genes expressed in the neural tube also may have rostrocaudal and mediolateral gradients in the other axes. These other gradients may be equally as important as the vertical. If the rostrocaudal gradient extends as far as the mesencephalic neuromere, it may interfere with the formation, migration, or apoptosis of the mesencephalic neural crest, which forms membranous bones of the face, orbits, nose, and parts of the eyes, and may explain the midfacial hypoplasia seen in many, but not all, children with holoprosencephaly. This rostrocaudal gradient also causes noncleavage of the caudate nucleus, thalamus, and hypothalamus and contributes to the formation of the dorsal cyst of holoprosencephaly, which is probably derived from an expanded suprapineal recess of the 3rd ventricle with secondary dilation of the telencephalic monoventricle and at times may produce a unique transfontanellar encephalocele. The extent of the mediolateral gradient may explain the severe disorganization of cerebral cortical architecture in medial parts of the forebrain and normal cortex in lateral parts, including the radial glial fibers. This preserved lateral cortex may explain why some children with holoprosencephaly have better intellectual function than expected and may also be important in the pathogenesis of epilepsy, by contrast with malformations such as lissencephaly, in which the entire cerebral cortex is involved. Epilepsy in some, but not all, cases also may be related to the sequential maturation of axonal terminals in relation to the neurons they innervate. Diabetes insipidus is a complication in a majority of patients; other neuroendocrinopathies occur less frequently. Secondary down-regulation of the OTP gene or of downstream genes such as BRN2 or SIM1 may result in failure of terminal differentiation of magnocellular neurons of the supraoptic and paraventricular hypothalamic nuclei. Disoriented radial glial fibers or abnormal ependyma may allow aberrant migration of neuroepithelial cells into the ventricle. A new classification of holoprosencephaly is needed to integrate morphologic and genetic criteria.

Cerebellar long-term depression: characterization, signal transduction, and functional roles

Cerebellar Purkinje cells exhibit a unique type of synaptic plasticity, namely, long-term depression (LTD). When two inputs to a Purkinje cell, one from a climbing fiber and the other from a set of granule cell axons, are repeatedly associated, the input efficacy of the granule cell axons in exciting the Purkinje cell is persistently depressed. Section I of this review briefly describes the history of research around LTD, and section II specifies physiological characteristics of LTD. Sections III and IV then review the massive data accumulated during the past two decades, which have revealed complex networks of signal transduction underlying LTD. Section III deals with a variety of first messengers, receptors, ion channels, transporters, G proteins, and phospholipases. Section IV covers second messengers, protein kinases, phosphatases and other elements, eventually leading to inactivation of DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazolone-propionate-selective glutamate receptors that mediate granule cell-to-Purkinje cell transmission. Section V defines roles of LTD in the light of the microcomplex concept of the cerebellum as functionally eliminating those synaptic connections associated with errors during repeated exercises, while preserving other connections leading to the successful execution of movements. Section VI examines the validity of this microcomplex concept based on the data collected from recent numerous studies of various forms of motor learning in ocular reflexes, eye-blink conditioning, posture, locomotion, and hand/arm movements. Section VII emphasizes the importance of integrating studies on LTD and learning and raises future possibilities of extending cerebellar research to reveal memory mechanisms of implicit learning in general.

Expression of calbindin-D28k and parvalbumin during development of rat's basolateral amygdaloid complex

Parvalbumin and calbindin-D28k are calcium-binding proteins, which are considered to be markers for certain populations of GABAergic neurons. Their correct development in the basolateral amygdaloid complex is critical for the proper emotional functioning in adult live of human and animals. Therefore, in this paper we describe the pattern of the morphological differentiation and distribution of immunoreactive elements of the parvalbumin and calbindin-D28k in this complex on the basis of immunohistochemically stained material obtained from embryonic (E20) and postnatal (P0-P90) rat brains. Calbindin-D28k appeared early in the development, already in the prenatal life. At this time immunopositive reaction was visible only in cell bodies. However, during development the population of immunopositive neurons was divided into four types: (1) polygonal; (2) piriform-like; (3) bipolar; and (4) pyramidal-like. Two weeks after birth calbindin-D28k immunoreactivity also appeared in neuropil. First, there were visible calbindin-D28k positive fibers and granules that encircled unstained cell bodies and formed basket-like structures. Subsequently, these granules appeared along proximal parts of unstained dendrites forming, so called 'cartridges'. The distribution of calbindin-D28k positive cells during postnatal life was rather homogenous throughout whole basolateral complex. Intensity of calbindin-D28k immunoreactivity reached mature level on the 21st day after birth.The maturation pattern of parvalbumin immunopositive elements followed the same sequence as calbindin-D28k, but it started much later - since the 17th day after birth and reached mature appearance on the 30th day of life. Contrary to calbindin-D28k, parvalbumin was not homogeneously distributed in the basolateral complex. Originally, parvalbumin was restricted to the magnocellular part of basolateral nucleus but it was finally expressed also in the parvicellular part of basolateral nucleus and the dorsolateral part of lateral nucleus. The differences in development of these two calcium-binding proteins indicate that parvalbumin and calbindin-D28k play diverse roles during development and maturation of the basolateral amygdala.

Neurotransmitters, neuropeptides and calcium binding proteins in developing human cerebellum: a review

Many endogenous neurochemicals that are known to have important functions in the mature central nervous system have also been found in the developing human cerebellum. Cholinergic neurons, as revealed by immunoreactivities towards choline acetyltransferase or acetylcholinesterase, appear early at 23 weeks of gestation in the cerebellar cortex and deep nuclei. Immunoreactivities gradually increase until the first postnatal month. Enkephalin is localized in the developing cerebellum, initially in the fibers of the cortex and deep nuclei at 16-20 weeks and then also in the Purkinje cells, granule cells, basket cells and Golgi cells at 23 weeks onward. Another neuropeptide, substance P, is localized mainly in the fibers of the dentate nucleus from 9 to 24 weeks but substance P immunoreactivity declines thereafter. GABA, an inhibitory neurotransmitter of the central nervous system, starts to appear at 16 weeks in the Purkinje cells, stellate cells, basket cells, mossy fibers and neurons of deep nuclei. GABA expression is gradually upregulated toward term forming networks of GABA-positive fibers and neurons. Catecholaminergic fibers and neurons are also detected in the cortex and deep nuclei at as early as 16 weeks. Calcium binding proteins, calbindin D28K and parvalbumin, make their first appearance in the cortex and deep nuclei at 14 weeks and then their expression decreases toward term, while calretinin appears later at 21 weeks but its expression increases with fetal age. The above findings suggest that many neurotransmitters, neuropeptides and calcium binding proteins (1) appear early during development of the cerebellum; (2) have specific temporal and spatial expression patterns; (3) may have functions other than those found in the mature neural systems; and (4) may be able to interact with each other during early development.

Calbindin immunoreactivity in the developing and adult human cerebellum

Calbindin (CALB), a calcium-binding protein, is known to be expressed in the embryonic nervous system. In this study, we have examined its distribution in the cerebellum of human fetuses (11-25 weeks of gestation) and adult by immunohistochemistry. At the gestational age of 11-12 weeks. CALB immunoreactivity was present in granule and Purkinje cells throughout the cerebellum. By 16-21 weeks of gestation, immunoreactive Purkinje cells were well-differentiated in the vermis and flocculus, and their axons ran towards the deep cerebellar nuclei area, while the axon collaterals were seen to be distributed into adjacent folia. At the gestational period of 24-25 weeks, most Purkinje cells of the flocculus and vermis were arranged in one to two rows, while those of the hemispheres were still undifferentiated. A few Golgi cells of the vermis showed immunoreactivity. The neurons of the deep nuclei were immunonegative right from the gestational age of 11 weeks although a fine stippled staining of fibers was present throughout the body of all nuclei. The fibers lying close to the hilum of the dentate nucleus were strongly CALB-positive. The vestibulocerebellar fibers, being traced at the level of lower pons and upper medulla oblongata were stained as early as 11 weeks of gestation, whereas the olivocerebellar fibers were stained from 16 weeks onward. In the adult cerebellum, Purkinje cells were moderately immunopositive while granule cells were faintly stained; no other cells, including those of the deep nuclei were stained. In the medulla oblongata, the inferior olivary nucleus and olivocerebellar fibers were strongly CALB-positive. Our results indicate that CALB is expressed in early migratory Purkinje cells, and their maturation occurs in a vermal-to-hemisphere gradient. It is likely that CALB plays a significant role in the regulation of Ca2+-dependent activities in the developing cerebellum.