Nam-Seob Lee

Differential alterations in expressions of ryanodine receptor subtypes in cerebellar cortical neurons of an ataxic mutant, rolling mouse Nagoya

This study aimed to clarify changes in the spatial expressions of types 1, 2 and 3 ryanodine receptors (RyR1, RyR2 and RyR3) in the cerebellum of a Ca(2+) channel alpha(1A) subunit mutant, rolling mouse Nagoya. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed that the mRNA signal levels of RyR1 and RyR3 were altered in the rolling cerebellum, which exhibited lower densities of RyR1 bands and higher densities of RyR3 bands than in the control cerebellum. Quite consistent with the RT-PCR results, the staining intensity of RyR1 and RyR3 was altered in the rolling cerebellum. RyR1 immunostaining appeared in somata and the proximal dendrites of Purkinje cells, and the staining intensity of both subcellular regions was equally lower in all cerebellar lobules of rolling mice than in those of controls. Although RyR3 immunostaining appeared in the dendrites of granule cells, more intense RyR3 staining in rolling mice than in controls was uniformly observed throughout all cerebellar lobules. The present study further examined co-localizations of ryanodine receptor subtypes and voltage-gated Ca(2+) channel alpha(1) subunits in the rolling cerebellum. Somatodendritic RyR1 immunostaining in Purkinje cells overlapped with either a mutated Ca(2+) channel alpha(1A) subunit (P/Q-type), or a Ca(2+) channel alpha(1C) subunit (L-type; dihydropyridine receptor) immunostaining. Immunostaining of these alpha(1) subunits also emerged in granule cells. Those results suggest non-region-related alterations in RyR1 and RyR3 expressions in the rolling mouse cerebellum. Such expressional changes in ryanodine receptor subtypes may be involved in Ca(2+) channel alpha(1A) subunit gene mutation, and may alter regulation of intracellular Ca(2+) concentrations in cerebellar cortical neurons.

Early cerebellar granule cell migration in the mouse embryonic development

Pax6, a paired homeobox DNA binding protein, has been found to be expressed in the cerebellum in both granule cells and their precursors in the external granular layer (EGL). In this study we have traced Pax6 expression through embryonic development in mice by using a polyclonal antibody against Pax6 and used it to study the cellular dispersal pattern of the EGL. During dispersal the EGL was thicker and Pax6 expression was more intense on the rostral side of the lateral corners of the cerebellum. Pax6 immunoreactive cells were found to be migrating from the EGL during the early stage of EGL dispersal, which suggested the early inward migration of granule cells. Double staining with various markers confirmed that the early-migrating cells are not Purkinje cells, interneurons or glia. Although the Pax6 immunoreactive cells within the cerebellum were not apparently proliferating, NeuN, a marker for postmitotic granule cells, was not expressed in these cells until E16. Furthermore, granule cells were observed migrating inwards from the EGL both during and after EGL dispersal. These early migrating granule cells populated the whole cerebellum. These findings offer novel views on specific stages of granule cell dispersal and migration.

Corticotropin-releasing factor immunoreactivity increases in the cerebellar climbing fibers in the novel ataxic mutant mouse, Pogo

The ataxic pogo mouse (pogo/pogo) is a novel neurological mutant, which was derived as an inbred strain (KJR/MsKist) from a Korean wild mouse. The pathological manifestations include a difficulty in maintaining a normal posture, the failure of inter‐limb coordination and an inability to walk straight. In this study, we examined the distribution of corticotropin‐releasing factor (CRF) immunoreactive cerebellar climbing fibres and their projections to tyrosine hydroxylase (TH) immunoreactive Purkinje cells in the cerebellum of the pogo mutant mouse using immunohistochemistry. In the pogo/pogo mouse, a subset of climbing fibres was stained more intensely for CRF than in the control. Moreover, ataxic pogo mouse, neurons of the inferior olivary nucleus projecting climbing fibres were also more intensely stained for CRF than in the control. In the pogo/pogo mouse, TH immunoreactivity was located in the Purkinje cells, whereas no TH expression was found in the control. Double immunostaining for CRF and TH in the pogo/pogo cerebellum revealed that the distribution of TH‐immunoreactive Purkinje cells corresponded to terminal fields of CRF‐immunoreactive climbing fibres but not to the CRF‐immunoreactive mossy fibres. Therefore, we suggest that an increase of CRF level may alter the function of targeted Purkinje cells and that it is related to the ataxic phenotype in the pogo mutant mouse.

Altered Purkinje cell responses and calmodulin expression in the spontaneously ataxic mouse, Pogo

Ataxia is often associated with altered cerebellar motor control, a process in which Purkinje cells (PCs) play a principal role. Pogo mice display severe motor deficits characterized by an ataxic gait accompanying hindlimb hyperextension. Here, using whole‐cell patch‐clamp recordings, we show that parallel fiber (PF)‐excitatory post‐synaptic currents (PF‐EPSCs) are reduced, paired‐pulse facilitation (PPF) is increased and PF‐PC long‐term depression (LTD) is impaired in Pogo mice; in contrast, climbing‐fiber EPSCs are preserved. In control mice, treatment with the calmodulin antagonist calmidazolium (5 μm) impaired PPF and LTD. Notably, cerebellar calmodulin expression was significantly reduced in Pogo mice compared with control mice. Control PCs predominantly exhibited a tonic firing pattern, whereas the firing pattern in Pogo PCs was mainly a complex burst type. These results implicate alterations in PC responses and calmodulin content in the abnormal cerebellar function of Pogo mice.

Pogo: A Novel Spontaneous Ataxic Mutant Mouse

The Pogo (pogo/pogo) mouse is a naturally occurring neurological mutant from a Korean wild-type mouse characterized by loss of balance and motor coordination due to dysfunction of the cerebellum. The Pogo mutation is believed to be an allele of P/Q-type calcium channel mutants such as tottering, leaner, and rolling mouse Nagoya. These mutants have been served as mouse models for a group of neurodegenerative diseases. The overall aim of this minireview is to summarize our current understanding of the ataxic Pogo mouse. To address this issue, we first describe the discovery of Pogo mouse and its morphological and behavioral defects. Then, we focus on the abnormal expression of several molecules in the Pogo cerebellum, including tyrosine hydroxylase, glutamate, corticotrophin-releasing factor, and 5-hydroxytryptamine. Much of this review is concerned with the functional implications of these ectopic molecules in the Pogo cerebellum.

Morphological characteristics of C1 and C2 adrenergic neurone groups in marmoset monkey brainstem by using antibody against phenylethanolamine-N-methyltransferase.

This work describes a mapping study of phenylethanolamine‐N‐methyltransferase (PNMT) immunoreactive neurones and fibres in the medulla oblongata of the marmoset monkey, Callithrix jacchus. Two groups of PNMT‐immunoreactive neurones were found in the marmoset monkey medulla oblongata: a ventrolateral (C1 group) and a dorsomedial PNMT‐immunoreactive cells group (C2 group). The PNMT‐immunoreactive cells in the ventrolateral group C1 were found to be located around the lateral reticular nucleus. The PNMT‐immunoreactive somata within the ventrolateral medulla are round to oval, and mostly multipolar with branched processes. In the dorsomedial group C2, PNMT‐immunoreactive cell bodies appeared near the obex. The majority of the dorsomedial PNMT‐immunoreactive neurones were observed in the nucleus tractus solitarius; although some were present in the dorsal motor nucleus of the vagus. The PNMT‐immunoreactive somata in the dorsomedial medulla were small and round or ovoid. These results provide information upon the adrenergic system in the medulla oblongata of a species that presents a useful model of a small primate brain, the marmoset monkey.

The absence of phosphorylated tyrosine hydroxylase expression in the purkinje cells of the ataxic mutant pogo mouse

The pogo mouse is a new ataxic autosomal recessive mutant that arose in Korean wild mice (KJR/Mskist). Its ataxic phenotype includes difficulty in maintaining a normal posture and the inability to walk in a straight line. Several studies have reported that tyrosine hydroxylase (TH) is persistently ectopically expressed in particular subsets of Purkinje cells in a parasagittal banding pattern in several ataxic mutant mice, e.g. tottering alleles and pogo mice. In this present study, we examined the expression of an enzymatically active form of TH and phosphorylated TH at Ser40 (phospho‐TH) by using immunohistochemistry and double immunofluorescence in the cerebellum of pogo mice. TH immunostaining appeared in some Purkinje cells in pogo, but in only a few of Purkinje cells of their heterozygous littermate controls. In all groups of mice, no phospho‐TH immunoreactive Purkinje cells were observed in the cerebellum, although subsets of TH immunoreactive Purkinje cells were found in adjacent sections. This study suggests that TH expression in the Purkinje cells of pogo abnormally increases without activation of this enzyme by phosphorylation. This may mean that TH in the Purkinje cells of these mutants does not catalyse the conversion of tyrosine to l‐DOPA, and is not related to catecholamine synthesis.

The effect of prenatal X-irradiation on the developing cerebral cortex of rats. II: A quantitative assessment of glial cells in the somatosensory cortex

The developing central nervous system is known to be highly vulnerable to X‐irradiation. Although glial cells are involved in various brain functions, knowledge on the effects of X‐irradiation on glial cells is limited. Therefore, the purpose of the present study was to evaluate the effects of prenatal X‐irradiation on glial cells. Pregnant Wistar rats were exposed to X‐irradiation at a dose of 1.0 Gy on day 15 of gestation. Their offspring were examined at 7 weeks of age. The forebrain weight of X‐irradiated rats was significantly lower than that of the age‐matched controls. Histological quantification with stereology of the somatosensory cortex (SC) revealed no significant difference in the numerical density of glial cells between the X‐irradiated and control rats. However, the glial cells in the X‐irradiated animals had significantly larger nuclear size. We had previously reported that a similar X‐irradiation paradigm resulted in no significant change in the numerical density of neurons in the SC. According to the results of the present study, there were no significant differences in the glial cell‐to‐neuron ratios between the X‐irradiated and control animals. Taken together, it is speculated that prenatal X‐irradiation has an equal effects on the numerical densities of glial cells and neurons.

Rhus verniciflua Stokes attenuates cholestatic liver cirrhosis-induced interstitial fibrosis via Smad3 down-regulation and Smad7 up-regulation

Cholestatic liver cirrhosis (CLC) eventually proceeds to end-stage liver failure by mediating overwhelming deposition of collagen, which is produced by activated interstitial myofibroblasts. Although the beneficial effects of Rhus verniciflua Stokes (RVS) on various diseases are well-known, its therapeutic effect and possible underlying mechanism on interstitial fibrosis associated with CLC are not elucidated. This study was designed to assess the protective effects of RVS and its possible underlying mechanisms in rat models of CLC established by bile duct ligation (BDL). We demonstrated that BDL markedly elevated the serological parameters such as aspartate aminotransferase, alanine transaminase, total bilirubin, and direct bilirubin, all of which were significantly attenuated by the daily uptake of RVS (2 mg/kg/day) for 28 days (14 days before and after operation) via intragastric route. We observed that BDL drastically induced the deterioration of liver histoarchitecture and excessive deposition of extracellular matrix (ECM), both of which were significantly attenuated by RVS. In addition, we revealed that RVS inhibited BDL-induced proliferation and activation of interstitial myofibroblasts, a highly suggestive cell type for ECM production, as shown by immunohistochemical and semi-quantitative detection of α-smooth muscle actin and vimentin. Finally, we demonstrated that the anti-fibrotic effect of RVS was associated with the inactivation of Smad3, the key downstream target of a major fibrogenic cytokine, i.e., transforming growth factor β (TGF-β). Simultaneously, we also found that RVS reciprocally increased the expression of Smad7, a negative regulatory protein of the TGF-β/Smad3 pathway. Taken together, these results suggested that RVS has a therapeutic effect on CLC, and these effects are, at least partly, due to the inhibition of liver fibrosis by the downregulation of Smad3 and upregulation of Smad7.

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.