Search result for : author:hong lin

Total 11 result(s) found

CACHD1 is an α2δ-like protein that modulates Ca3 voltage-gated calcium channel activity.

The putative cache (Ca channel and chemotaxis receptor) domain containing 1 (CACHD1) protein has predicted structural similarities to members of the α2δ voltage-gated Ca channel (VGCC) auxiliary subunit family. CACHD1 mRNA and protein were highly expressed in the male mammalian CNS, in particular in the thalamus, hippocampus and cerebellum, with a broadly similar tissue distribution to Ca3 subunits, in particular, Ca3.1. In expression studies, CACHD1 increased cell-surface localization of Ca3.1 and these proteins were in close proximity at the cell surface consistent with the formation of CACHD1-Ca3.1 complexes. In functional electrophysiological studies, co-expression of human CACHD1 with Ca3.1, Ca3.2 and Ca3.3 caused a significant increase in peak current density and corresponding increases in maximal conductance. By contrast, α2δ-1 had no effect on peak current density or maximal conductance in either Ca3.1, Ca3.2 or Ca3.3. Comparison of CACHD1-mediated increases in Ca3.1 current density and gating currents revealed an increase in channel open probability. In hippocampal neurons from male and female E19 rats, CACHD1 overexpression increased Ca3-mediated action potential (AP) firing frequency and neuronal excitability. These data suggest that CACHD1 is structurally an α2δ-like protein that functionally modulates Ca3 voltage-gated calcium channel activity.This is the first study to characterise the CACHD1 protein. CACHD1 is widely expressed in the CNS, in particular in the thalamus, hippocampus and cerebellum. CACHD1 distribution is similar to that of low-voltage-activated (Ca3, T-type) calcium channels, in particular to Ca3.1, a protein which regulates neuronal excitability and is a potential therapeutic target in conditions such as epilepsy and pain. CACHD1 is structurally a α2δ-like protein that functionally increases Ca3 calcium current. CACHD1 increases the presence of Ca3.1 at the cell surface, forms complexes with Ca3.1 at the cell-surface and causes an increase in channel open probability. In hippocampal neurons, CACHD1 causes increases in neuronal firing. Thus, CACHD1 represents a novel protein that modulates Ca3 activity.

Graeme S Cottrell, Camille H Soubrane, James A Hounshell, Hong Lin, Venetia Owenson, Michael Rigby, Peter J Cox, Bryan S Barker, Matteo Ottolini, Selvi Ince, Claudia C Bauer, Edward Perez-Reyes, Manoj K Patel, Edward B Stevens, Gary J Stephens

Neuron-derived FGF9 is essential for scaffold formation of Bergmann radial fibers and migration of granule neurons in the cerebellum.

Although fibroblast growth factor 9 (FGF9) is widely expressed in the central nervous system (CNS), the function of FGF9 in neural development remains undefined. To address this question, we deleted the Fgf9 gene specifically in the neural tube and demonstrated that FGF9 plays a key role in the postnatal migration of cerebellar granule neurons. Fgf9-null mice showed severe ataxia associated with disrupted Bergmann fiber scaffold formation, impaired granule neuron migration, and upset Purkinje cell maturation. Ex vivo cultured wildtype or Fgf9-null glia displayed a stellate morphology. Coculture with wildtype neurons, but not Fgf9-deficient neurons, or treating with FGF1 or FGF9 induced the cells to adopt a radial glial morphology. In situ hybridization showed that Fgf9 was expressed in neurons and immunostaining revealed that FGF9 was broadly distributed in both neurons and Bergmann glial radial fibers. Genetic analyses revealed that the FGF9 activities in cerebellar development are primarily transduced by FGF receptors 1 and 2. Furthermore, inhibition of the MAP kinase pathway, but not the PI3K/AKT pathway, abrogated the FGF activity to induce glial morphological changes, suggesting that the activity is mediated by the MAP kinase pathway. This work demonstrates that granule neurons secrete FGF9 to control formation of the Bergmann fiber scaffold, which in turn, guides their own inward migration and maturation of Purkinje cells.

Yongshun Lin, Lijie Chen, Chunhong Lin, Yongde Luo, Robert Y L Tsai, Fen Wang

Activation of JNK by vanadate induces a Fas-associated death domain (FADD)-dependent death of cerebellar granule progenitors in vitro.

Apoptosis is a highly regulated process that plays a critical role in neuronal development as well as the homeostasis of the adult nervous system. Vanadate, an environmental toxicant, causes developmental defects in the central nervous system. Here, we demonstrated that vanadate induced apoptosis in cultured cerebellar granule progenitors (CGPs). Treatment of cultured CGPs with vanadate activated ERKs and JNKs but not p38 MAPK and also induced c-Jun phosphorylation. In addition, vanadate induced FasL production, Fas (CD95) aggregation, and its association with the Fas-associated death domain (FADD), as well as the activation of caspase-8. Furthermore, vanadate generated reactive oxygen species (ROS) in CGPs; however, ROS was not involved in vanadate-mediated MAPK activation. Vanadate-induced FasL expression was ROS-dependent but JNK-independent. In contrast, vanadate-elicited Fas aggregation and Fas-FADD association, as well as caspase-8 activation, were dependent on JNK activation but were minimally regulated by ROS generation. The hydrogen peroxide scavenger, catalase, blocked vanadate-induced FasL expression and partially mitigated vanadate-induced cell death. On the other hand, dominant negative FADD and caspase-8 inhibitor completely eliminated vanadate-induced apoptosis. Thus, JNK signaling plays a major role in vanadate-mediated activation of the Fas-FADD-caspase-8 pathway that accounts for vanadate-induced apoptosis of CGPs.

Jia Luo, Yanbo Sun, Hong Lin, Yong Qian, Zheng Li, Stephen S Leonard, Chuanshu Huang, Xianglin Shi

Horizontal eyeball akinesia as an initial manifestation of CLIPPERS: Case report and review of literature.

Chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) is a rare chronic inflammatory disorder in the central nervous system (CNS), which is characterized by magnetic resonance imaging (MRI) appearance with punctate and curvilinear gadolinium enhancement "peppering" the pons. Lesions of CLIPPERS mainly involve the pons and the cerebellum. Adjacent structures such as the medulla and the midbrain may also be involved. It is proposed that CLIPPERS is an immune-mediated inflammatory condition characteristic of T-cell-predominant infiltrates and good responsiveness to corticosteroids. We report a 46-year-old woman who presented with horizontal eyeball akinesia and gait ataxia with characteristic MRI features of CLIPPERS. The possible pathogenesis, clinical manifestations, imaging features, treatment, and prognosis of this peculiar disorder are summarized. This report contributes to the clinical understanding of CLIPPERS which may present with horizontal eyeball akinesia as an initial manifestation. The characteristic presentation of a subacute cerebellar and brainstem syndrome and pepper-like gadolinium enhancement was confirmed in this report. Long-term immunosuppressive treatment seems to be mandatory to sustain improvement. Azathioprine alone may be capable of maintaining remission.

Xiaohe Hou, Xiaoke Wang, Bo Xie, Weihong Lin, Jun Liu, Dihui Ma, Hong-Liang Zhang

Genetic mapping of ASIC4 and contrasting phenotype to ASIC1a in modulating innate fear and anxiety.

Although ASIC4 is a member of the acid-sensing ion channel (ASIC) family, we have limited knowledge of its expression and physiological function in vivo. To trace the expression of this ion channel, we generated the ASIC4-knockout/CreERT(2)-knockin (Asic4(Cre) (ERT) (2)) mouse line. After tamoxifen induction in the Asic4(Cre) (ERT)(2)::CAG-STOP(floxed)-Td-tomato double transgenic mice, we mapped the expression of ASIC4 at the cellular level in the central nervous system (CNS). ASIC4 was expressed in many brain regions, including the olfactory bulb, cerebral cortex, striatum, hippocampus, amygdala, thalamus, hypothalamus, brain stem, cerebellum, spinal cord and pituitary gland. Colocalisation studies further revealed that ASIC4 was expressed mainly in three types of cells in the CNS: (i) calretinin (CR)-positive and/or vasoactive intestine peptide (VIP)-positive interneurons; (ii) neural/glial antigen 2 (NG2)-positive glia, also known as oligodendrocyte precursor cells; and (iii) cerebellar granule cells. To probe the possible role of ASIC4, we hypothesised that ASIC4 could modulate the membrane expression of ASIC1a and thus ASIC1a signaling in vivo. We conducted behavioral phenotyping of Asic4(Cre) (ERT)(2) mice by screening many of the known behavioral phenotypes found in Asic1a knockouts and found ASIC4 not involved in shock-evoked fear learning and memory, seizure termination or psychostimulant-induced locomotion/rewarding effects. In contrast, ASIC4 might play an important role in modulating the innate fear response to predator odor and anxious state because ASIC4-mutant mice showed increased freezing response to 2,4,5-trimethylthiazoline and elevated anxiety-like behavior in both the open-field and elevated-plus maze. ASIC4 may modulate fear and anxiety by counteracting ASIC1a activity in the brain.

Shing-Hong Lin, Ya-Chih Chien, Wei-Wei Chiang, Yan-Zhen Liu, Cheng-Chang Lien, Chih-Cheng Chen

The Role of Intermittent Hypoxia on the Proliferative Inhibition of Rat Cerebellar Astrocytes.

Sleep apnea syndrome, characterized by intermittent hypoxia (IH), is linked with increased oxidative stress. This study investigates the mechanisms underlying IH and the effects of IH-induced oxidative stress on cerebellar astrocytes. Rat primary cerebellar astrocytes were kept in an incubator with an oscillating O2 concentration between 20% and 5% every 30 min for 1-4 days. Although the cell loss increased with the duration, the IH incubation didn't induce apoptosis or necrosis, but rather a G0/G1 cell cycle arrest of cerebellar astrocytes was noted. ROS accumulation was associated with cell loss during IH. PARP activation, resulting in p21 activation and cyclin D1 degradation was associated with cell cycle G0/G1 arrest of IH-treated cerebellar astrocytes. Our results suggest that IH induces cell loss by enhancing oxidative stress, PARP activation and cell cycle G0/G1 arrest in rat primary cerebellar astrocytes.

Sheng-Chun Chiu, Yu-Jou Lin, Sung-Ying Huang, Chih-Feng Lien, Shee-Ping Chen, Cheng-Yoong Pang, Jian-Hong Lin, Kun-Ta Yang

Mitigation of cerebellar neuropathy in globoid cell leukodystrophy mice by AAV-mediated gene therapy.

Globoid cell leukodystrophy (GLD) is an autosomal recessive, lysosomal storage disease caused by deficiency of the enzyme galactocerebrosidase (GALC). The absence of GALC activity leads to the accumulation of the toxic substance psychosine and the preferential loss of myelinating cells in the central and peripheral nervous systems. Profound demyelination, astrogliosis and axonopathy are the hallmarks of the pathogenesis of GLD, and cerebellar ataxia is one of the dominant manifestations in adolescents and adults affected with GLD. To date, studies regarding cerebellar degeneration in GLD are limited. In this study, the efficacy of cerebellum-targeted gene therapy on the cerebellar neuropathology in twitcher mice (a murine model of GLD) has been validated. We observed degeneration of Purkinje cells, Bergmann glia, and granule cells in addition to astrocytosis and demyelination in the cerebellum of the twitcher mice. Ultrastructural analysis revealed dark cell degeneration and disintegration of the cellular composition of Purkinje cells in untreated twitcher mice. In addition, the expressions of neurotrophic factors CNTF, GDNF and IGF-I were up-regulated and the expression of BDNF was down-regulated. Intracerebellar-mediated gene therapy efficiently corrected enzymatic deficiency by direct transduction to Purkinje cells and cross-correction in other cell types in the cerebellum, leading to the amelioration of both neuroinflammation and demyelination. The population, dendritic territory, and axonal processes of Purkinje cells remained normal in the cerebellum of treated twitcher mice, where radial fibers of Bergmann glia spanned the molecular layer and collateral branches ensheathed the dendritic processes of Purkinje cells. Moreover, the aberrant expressions of neurotrophic factors were mitigated in the cerebellum of treated twitcher mice, indicating the preservation of cellular function in addition to maintaining the neuronal architecture. The life span of the treated twitcher mice was significantly prolonged and their neurobehavioral performance was improved. Taken together, our findings underscore the complexity of cerebellar neurodegeneration in GLD and highlight the potential effectiveness of gene therapy in mitigating neuropathological deficits in GLD and other neurodegenerative disorders in which Purkinje cells are involved.

Dar-Shong Lin, Chung-Der Hsiao, Allan Yueh-Luen Lee, Che-Sheng Ho, Hsuan-Liang Liu, Tuen-Jen Wang, Yuan-Ren Jian, Jui-Cheng Hsu, Zon-Darr Huang, Tsung-Han Lee, Ming-Fu Chiang

Adaptive modulation of adult brain gray and white matter to high altitude: structural MRI studies.

The aim of this study was to investigate brain structural alterations in adult immigrants who adapted to high altitude (HA). Voxel-based morphometry analysis of gray matter (GM) volumes, surface-based analysis of cortical thickness, and Tract-Based Spatial Statistics analysis of white matter fractional anisotropy (FA) based on MRI images were conducted on 16 adults (20-22 years) who immigrated to the Qinghai-Tibet Plateau (2300-4400 m) for 2 years. They had no chronic mountain sickness. Control group consisted of 16 matched sea level subjects. A battery of neuropsychological tests was also conducted. HA immigrants showed significantly decreased GM volumes in the right postcentral gyrus and right superior frontal gyrus, and increased GM volumes in the right middle frontal gyrus, right parahippocampal gyrus, right inferior and middle temporal gyri, bilateral inferior ventral pons, and right cerebellum crus1. While there was some divergence in the left hemisphere, surface-based patterns of GM changes in the right hemisphere resembled those seen for VBM analysis. FA changes were observed in multiple WM tracts. HA immigrants showed significant impairment in pulmonary function, increase in reaction time, and deficit in mental rotation. Parahippocampal and middle frontal GM volumes correlated with vital capacity. Superior frontal GM volume correlated with mental rotation and postcentral GM correlated with reaction time. Paracentral lobule and frontal FA correlated with mental rotation reaction time. There might be structural modifications occurred in the adult immigrants during adaptation to HA. The changes in GM may be related to impaired respiratory function and psychological deficits.

Jiaxing Zhang, Haiyan Zhang, Jinqiang Li, Ji Chen, Qiaoqing Han, Jianzhong Lin, Tianhe Yang, Ming Fan

CNS-targeted AAV5 gene transfer results in global dispersal of vector and prevention of morphological and function deterioration in CNS of globoid cell leukodystrophy mouse model.

Globoid cell leukodystrophy (GLD) is a devastating lysosomal storage disease caused by deficiency of the enzyme galactocerebrosidase (GALC). Currently, there is no definite cure for GLD. Several attempts with CNS-directed gene therapy in twitcher mice (a murine model of GLD) demonstrated restricted expression of GALC activity in CNS and failure of therapeutic efficacy in cerebellum and spinal cord, resulting in various degrees of correction of biochemical, pathological and clinical phenotype. More recently, twitcher mice receiving a combination of hematopoietic and viral vector gene transfer therapies were not protected from neurodegeneration and axonopathy in both cerebellum and spinal cord. This evidence indicates the requirement of sufficient and widespread GALC expression in CNS and rescue of cerebellum and spinal cord in the therapeutic intervention of murine model of GLD. In this study, we have optimized intracranial delivery of AAV2/5-GALC to the neocortex, hippocampus and cerebellum, instead of the thalamus as was previously conducted, of twitcher mice. The CNS-targeted AAV2/5 gene transfer effectively dispersed GALC transgene along the neuraxis of CNS as far as the lumbar spinal cord, and reduced the accumulation of psychosine in the CNS of twitcher mice. Most importantly, the treated twitcher mice were protected from loss of oligodendrocytes and Purkinje cells, axonopathy and marked gliosis, and had significantly improved neuromotor function and prolonged lifespan. These preclinical findings with our approach are encouraging, although a more robust response in the spinal cord would be desirable. Collectively, the information in this study validates the efficacy of this gene delivery approach to correct enzymatic deficiency, psychosine accumulation and neuropathy in CNS of GLD. Combining cell therapy such as bone marrow transplantation with treatment with the aim of reducing inflammation, replacing dead or dying oligodendrocytes and targeting PNS may provide a synergistic and more complete correction of this disease.

Dar-Shong Lin, Chung-Der Hsiao, Ian Liau, Shuan-Pei Lin, Ming-Fu Chiang, Chih-Kuang Chuang, Tuen-Jen Wang, Tsu-Yen Wu, Yuan-Ren Jian, Sung-Fa Huang, Hsuan-Liang Liu

Early VGLUT1-specific parallel fiber synaptic deficits and dysregulated cerebellar circuit in the KIKO mouse model of Friedreich ataxia.

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder with progressive ataxia that affects both the peripheral and central nervous system (CNS). While later CNS neuropathology involves loss of large principal neurons and glutamatergic and GABAergic synaptic terminals in the cerebellar dentate nucleus, early pathological changes in FRDA cerebellum remain largely uncharacterized. Here, we report early cerebellar VGLUT1 (SLC17A7)-specific parallel fiber (PF) synaptic deficits and dysregulated cerebellar circuit in the frataxin knock-in/knockout (KIKO) FRDA mouse model. At asymptomatic ages, VGLUT1 levels in cerebellar homogenates are significantly decreased, whereas VGLUT2 (SLC17A6) levels are significantly increased, in KIKO mice compared with age-matched controls. Additionally, GAD65 (GAD2) levels are significantly increased, while GAD67 (GAD1) levels remain unaltered. This suggests early VGLUT1-specific synaptic input deficits, and dysregulation of VGLUT2 and GAD65 synaptic inputs, in the cerebellum of asymptomatic KIKO mice. Immunohistochemistry and electron microscopy further show specific reductions of VGLUT1-containing PF presynaptic terminals in the cerebellar molecular layer, demonstrating PF synaptic input deficiency in asymptomatic and symptomatic KIKO mice. Moreover, the parvalbumin levels in cerebellar homogenates and Purkinje neurons are significantly reduced, but preserved in other interneurons of the cerebellar molecular layer, suggesting specific parvalbumin dysregulation in Purkinje neurons of these mice. Furthermore, a moderate loss of large principal neurons is observed in the dentate nucleus of asymptomatic KIKO mice, mimicking that of FRDA patients. Our findings thus identify early VGLUT1-specific PF synaptic input deficits and dysregulated cerebellar circuit as potential mediators of cerebellar dysfunction in KIKO mice, reflecting developmental features of FRDA in this mouse model.

Hong Lin, Jordi Magrane, Elisia M Clark, Sarah M Halawani, Nathan Warren, Amy Rattelle, David R Lynch

Early cerebellar deficits in mitochondrial biogenesis and respiratory chain complexes in the KIKO mouse model of Friedreich ataxia.

Friedreich ataxia (FRDA), the most common recessive inherited ataxia, results from deficiency of frataxin, a small mitochondrial protein crucial for iron-sulphur cluster formation and ATP production. Frataxin deficiency is associated with mitochondrial dysfunction in FRDA patients and animal models; however, early mitochondrial pathology in FRDA cerebellum remains elusive. Using frataxin knock-in/knockout (KIKO) mice and KIKO mice carrying the mitoDendra transgene, we show early cerebellar deficits in mitochondrial biogenesis and respiratory chain complexes in this FRDA model. At asymptomatic stages, the levels of PGC-1α (PPARGC1A), the mitochondrial biogenesis master regulator, are significantly decreased in cerebellar homogenates of KIKO mice compared with age-matched controls. Similarly, the levels of the PGC-1α downstream effectors, NRF1 and Tfam, are significantly decreased, suggesting early impaired cerebellar mitochondrial biogenesis pathways. Early mitochondrial deficiency is further supported by significant reduction of the mitochondrial markers GRP75 (HSPA9) and mitofusin-1 in the cerebellar cortex. Moreover, the numbers of Dendra-labeled mitochondria are significantly decreased in cerebellar cortex, confirming asymptomatic cerebellar mitochondrial biogenesis deficits. Functionally, complex I and II enzyme activities are significantly reduced in isolated mitochondria and tissue homogenates from asymptomatic KIKO cerebella. Structurally, levels of the complex I core subunit NUDFB8 and complex II subunits SDHA and SDHB are significantly lower than those in age-matched controls. These results demonstrate complex I and II deficiency in KIKO cerebellum, consistent with defects identified in FRDA patient tissues. Thus, our findings identify early cerebellar mitochondrial biogenesis deficits as a potential mediator of cerebellar dysfunction and ataxia, thereby providing a potential therapeutic target for early intervention of FRDA.

Hong Lin, Jordi Magrane, Amy Rattelle, Anna Stepanova, Alexander Galkin, Elisia M Clark, Yi Na Dong, Sarah M Halawani, David R Lynch