The scaffold protein JSAP1 regulates proliferation and differentiation of cerebellar granule cell precursors by modulating JNK signaling

金沢大学がん研究所がん分子細胞制御Cerebellar granule cell precursors (GCPs) proliferate in the outer part of the external granular layer (EGL). They begin their differentiation by exiting the cell cycle and migrating into the inner part of the EGL. Here we report that JSAP1, a scaffold protein for JNK signaling pathways, is expressed predominantly in the post-mitotic GCPs of the inner EGL. JSAP1 knockdown or treatment with a JNK inhibitor enhances the proliferation of cultured GCPs, but the overexpression of wild-type JSAP1 leads to increased proportions of p27Kip1- and NeuN-positive cells, even with saturating concentrations of Sonic hedgehog (Shh), a potent GCP mitogen. However, these differentiation-promoting effects on GCPs are attenuated significantly in cells overexpressing a mutant JSAP1 that lacks the JNK-binding domain. Together, these data suggest that JSAP1 antagonizes the mitogenic effect of Shh on GCPs and promotes their exit from the cell cycle and differentiation, by modulating JNK activity. © 2008 Elsevier Inc. All rights reserved

Hand-assisted laparoscopic subtotal colectomy with cecorectal anastomosis for chronic idiopathic colonic pseudo-obstruction: report of a case

Chronic idiopathic colonic pseudo-obstruction (CICP) is characterized by the chronic disturbance of colonic motility without mechanical obstruction, any underlying disease or medication. Currently, there are no established medical treatments for CICP. A 62-year-old female who had undergone right hemicolectomy for splenic flexure syndrome caused by idiopathic megacolon was referred to our hospital with relapse, experiencing palpitation and abdominal fullness. She was diagnosed with CICP according to findings of marked dilation of the colon without mechanical obstruction, dilation of other parts of the gastrointestinal tract, or underlying disease. The dilated colon was surgically removed by hand-assisted laparoscopic subtotal colectomy, followed by cecorectal anastomosis. Histopathologically, there was no degeneration or lack of ganglion cells in Auerbach\u27s plexus. The patient has experienced no severe symptoms after undergoing the present operation

A hot spot for hotfoot mutations in the gene encoding the δ2 glutamate receptor

The orphan glutamate receptor δ2 is selectively expressed in Purkinje cells and plays a crucial role in cerebellar functions. Recently, ataxia in the hotfoot mouse ho4J was demonstrated to be caused by a deletion in the δ2 receptor gene ( Grid2 ) removing the N-terminal 170 amino acids of the δ2 receptor. To understand how δ2 receptors function, we characterized mutations in eight additional spontaneously occurring hotfoot alleles of Grid2 . The mouse Grid2 gene consists of 16 exons, spanning approximately 1.4 Mb. Genomic DNA analysis showed that seven hotfoot mutants had a deletion of one or more exons encoding the N-terminal domain of δ2 receptors. The exception is ho5J , which has a point mutation in exon 12. Deletions in ho7J, ho9J , ho11J and ho12J mice result in the in-frame deletion of between 40 and 95 amino acids. Expression of constructs containing these deletions in HEK293 cells resulted in protein retention in the endoplasmic reticulum or cis -Golgi without transport to the cell surface. Coimmunoprecipitation assays indicated that these deletions also reduce the intermolecular interaction between individual δ2 receptors. These results indicate that the deleted N-terminal regions are crucial for oligomerization of δ2 receptors and their subsequent transport to the cell surface of Purkinje cells. The relatively large size of the Grid2 gene may be one of the reasons why many spontaneous mutations occur in this gene. In addition, the frequent occurrence of in-frame deletions within the N-terminal domain in hotfoot mutants suggests the importance of this domain in the function of δ2 receptors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71747/1/j.1460-9568.2003.02595.x.pd

Lentivector-mediated rescue from cerebellar ataxia in a mouse model of spinocerebellar ataxia

Polyglutamine disorders are inherited neurodegenerative diseases caused by the accumulation of expanded polyglutamine protein (polyQ). Previously, we identified a new guanosine triphosphatase, CRAG, which facilitates the degradation of polyQ aggregates through the ubiquitin–proteasome pathway in cultured cells. Because expression of CRAG decreases in the adult brain, a reduced level of CRAG could underlie the onset of polyglutamine diseases. To examine the potential of CRAG expression for treating polyglutamine diseases, we generated model mice expressing polyQ predominantly in Purkinje cells. The model mice showed poor dendritic arborization of Purkinje cells, a markedly atrophied cerebellum and severe ataxia. Lentivector-mediated expression of CRAG in Purkinje cells of model mice extensively cleared polyQ aggregates and re-activated dendritic differentiation, resulting in a striking rescue from ataxia. Our in vivo data substantiate previous cell-culture-based results and extend further the usefulness of targeted delivery of CRAG as a gene therapy for polyglutamine diseases

CD3 and Immunoglobulin G Fc Receptor Regulate Cerebellar Functions▿

The immune and nervous systems display considerable overlap in their molecular repertoire. Molecules originally shown to be critical for immune responses also serve neuronal functions that include normal brain development, neuronal differentiation, synaptic plasticity, and behavior. We show here that FcγRIIB, a low-affinity immunoglobulin G Fc receptor, and CD3 are involved in cerebellar functions. Although membranous CD3 and FcγRIIB are crucial regulators on different cells in the immune system, both CD3ɛ and FcγRIIB are expressed on Purkinje cells in the cerebellum. Both CD3ɛ-deficient mice and FcγRIIB-deficient mice showed an impaired development of Purkinje neurons. In the adult, rotarod performance of these mutant mice was impaired at high speed. In the two knockout mice, enhanced paired-pulse facilitation of parallel fiber-Purkinje cell synapses was shared. These results indicate that diverse immune molecules play critical roles in the functional establishment in the cerebellum