Notch1 and Jagged1 are expressed after CNS demyelination, but are not a major rate-determining factor during remyelination

The reasons for the eventual failure of repair mechanisms in multiple sclerosis are unknown. The presence of precursor and immature oligodendrocytes in some non-repairing lesions suggests a mechanism in which these cells either receive insufficient differentiation signals or are exposed to differentiation inhibitors. Jagged signalling via Notch receptors on oligodendrocyte precursor cells (OPCs) inhibits their differentiation during development and the finding that both notch and jagged are expressed in multiple sclerosis lesions has fostered the view that this signalling pathway may explain remyelination failure. In this study, we show that Notch1 is expressed on adult OPCs and that there are multiple cellular sources of its ligand Jagged1 in a rodent model of remyelination. However, despite their expression, the lesions undergo complete remyelination. To establish whether Notch-jagged signalling regulates the rate of remyelination we compared their expression profiles in young animals with those in older animals, where remyelination occurs more slowly, but could find no correlation between expression and remyelination rate. Finally we found that OPC-targeted Notch1 ablation in cuprizone-treated Plp-creER Notch1lox/lox transgenic mice yielded no significant differences in remyelination parameters between knock-out and control mice. Thus, in contrast to developmental myelination, adult expression of Notch1 and Jagged1 neither prevents nor plays a major rate-determining role in remyelination. More generally, the re-expression of developmentally expressed genes following injury in the adult does not per se imply similar functio

Besides Purkinje cells and granule neurons: an appraisal of the cell biology of the interneurons of the cerebellar cortex

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The rho GTPase Rac1 is required for proliferation and survival of progenitors in the developing forebrain

Progenitor cells in the ventricular zone (VZ) and subventricular zone (SVZ) of the developing forebrain give rise to neurons and glial cells, and are characterized by distinct morphologies and proliferative behaviors. The mechanisms that distinguish VZ and SVZ progenitors are not well understood, although the homeodomain transcription factor Cux2 and Cyclin D2, a core component of the cell cycle machinery, are specifically involved in controlling SVZ cell proliferation. Rho GTPases have been implicated in regulating the proliferation, differentiation and migration of many cell types, and one family member, Cdc42, affects the polarity and proliferation of radial glial cells in the VZ. Here we show that another family member, Rac1, is required for the normal proliferation and differentiation of SVZ progenitors and for survival of both VZ and SVZ progenitors. A forebrain-specific loss of Rac1 leads to an SVZ-specific reduction in proliferation, a concomitant increase in cell cycle exit, and premature differentiation. In Rac1 mutants the SVZ and VZ can no longer be delineated, but rather fuse to become a single compact zone of intermingled cells. Cyclin D2 expression, which is normally expressed by both VZ and SVZ progenitors, is reduced in Rac1 mutants, suggesting that the mutant cells differentiate precociously. Rac1-deficient mice can still generate SVZ-derived upper layer neurons, indicating that Rac1 is not required for the acquisition of upper layer neuronal fates, but instead is needed for the normal regulation of proliferation by progenitor cells in the SVZ

Notch1 and Jagged1 are expressed after CNS demyelination, but are not a major rate-determining factor during remyelination

ISSN:0006-8950ISSN:1460-215

Tamoxifen-inducible glia-specific Cre mice for somatic mutagenesis in oligodendrocytes and Schwann cells

Inducible transgenesis provides a valuable technique for the analysis of gene function in vivo. We report the generation and characterization of mouse lines carrying glia lineage-specific transgenes expressing an improved variant of the tamoxifen-inducible Cre recombinase, CreERT2, where the recombinase is fused to a mutated ligand binding domain of the human estrogen receptor. Using a PLP-CreERT2 transgene, we have generated mice that show specific inducible Cre function, as analyzed by cross-breeding experiments into the Rosa26 Cre-LacZ reporter line, in developing and adult Schwann cells, in mature myelinating oligodendrocytes, and in undifferentiated NG2-positive oligodendrocyte precursors in the adult. Using a P0Cx-CreERT2 transgene, we have also established mouse lines with inducible Cre function specifically in the Schwann cell lineage. These tamoxifen-inducible CreERT2 lines will allow detailed spatiotemporally controlled analysis of gene functions in loxP-based conditional mutant mice in both developing and adult Schwann cells and in the oligodendrocyte lineage

E-cadherin controls adherens junctions in the epidermis and the renewal of hair follicles

E-cadherin is thought to mediate intercellular adhesion in the mammalian epidermis and in hair follicles as the adhesive component of adherens junctions. We have tested this role of E-cadherin directly by conditional gene ablation in the mouse. We show that postnatal loss of E-cadherin in keratinocytes leads to a loss of adherens junctions and altered epidermal differentiation without accompanying signs of inflammation. Overall tissue integrity and desmosomal structures were maintained, but skin hair follicles were progressively lost. Tumors were not observed and β-catenin levels were not strongly altered in the mutant skin. We conclude that E-cadherin is required for maintaining the adhesive properties of adherens junctions in keratinocytes and proper skin differentiation. Furthermore, continuous hair follicle cycling is dependent on E-cadherin

A Guide to Single-Cell Transcriptomics in Adult Rodent Brain: The Medium Spiny Neuron Transcriptome Revisited

Recent advances in single-cell technologies are paving the way to a comprehensive understanding of the cellular complexity in the brain. Protocols for single-cell transcriptomics combine a variety of sophisticated methods for the purpose of isolating the heavily interconnected and heterogeneous neuronal cell types in a relatively intact and healthy state. The emphasis of single-cell transcriptome studies has thus far been on comparing library generation and sequencing techniques that enable measurement of the minute amounts of starting material from a single cell. However, in order for data to be comparable, standardized cell isolation techniques are essential. Here, we analyzed and simplified methods for the different steps critically involved in single-cell isolation from brain. These include enzymatic digestion, tissue trituration, improved methods for efficient fluorescence-activated cell sorting in samples containing high degree of debris from the neuropil, and finally, highly region-specific cellular labeling compatible with use of stereotaxic coordinates. The methods are exemplified using medium spiny neurons (MSN) from dorsomedial striatum, a cell type that is clinically relevant for disorders of the basal ganglia, including psychiatric and neurodegenerative diseases. We present single-cell RNA sequencing (scRNA-Seq) data from D1 and D2 dopamine receptor expressing MSN subtypes. We illustrate the need for single-cell resolution by comparing to available population-based gene expression data of striatal MSN subtypes. Our findings contribute toward standardizing important steps of single-cell isolation from adult brain tissue to increase comparability of data. Furthermore, our data redefine the transcriptome of MSNs at unprecedented resolution by confirming established marker genes, resolving inconsistencies from previous gene expression studies, and identifying novel subtype-specific marker genes in this important cell type