Diabetic neuropathy is one of the most serious complications of diabetes, and its increase shows no sign of stopping. Furthermore, current clinical treatments do not yet approach the best ...effectiveness. Thus, the development of better strategies for treating diabetic neuropathy is an urgent matter. In this review, we first discuss the advantages and disadvantages of some major mouse models of diabetic neuropathy and then address the targets for mechanism-based treatment that have been studied. We also introduce our studies on each part. Using stem cells as a source of neurotrophic factors to target extrinsic factors of diabetic neuropathy, we found that they present a promising treatment.
Establishment of the corpus callosum involves coordination between callosal projection neurons and multiple midline structures, including the glial wedge (GW) rostrally and hippocampal commissure ...caudally. GW defects have been associated with agenesis of the corpus callosum (ACC). Here we show that conditional Lhx2 inactivation in cortical radial glia using Emx1-Cre or Nestin-Cre drivers results in ACC. The ACC phenotype was characterized by aberrant ventrally projecting callosal axons rather than Probst bundles, and was 100% penetrant on 2 different mouse strain backgrounds. Lhx2 inactivation in postmitotic cortical neurons using Nex-Cre mice did not result in ACC, suggesting that the mutant phenotype was not autonomous to the callosal projection neurons. Instead, ACC was associated with an absent hippocampal commissure and a markedly reduced to absent GW. Expression studies demonstrated strong Lhx2 expression in the normal GW and in its radial glial progenitors, with absence of Lhx2 resulting in normal Emx1 and Sox2 expression, but premature exit from the cell cycle based on EdU-Ki67 double labeling. These studies define essential roles for Lhx2 in GW, hippocampal commissure, and corpus callosum formation, and suggest that defects in radial GW progenitors can give rise to ACC.
By altering their morphology, astrocytes, including those involved in the maintenance and plasticity of neurons and in clearance of transmitter, play important roles in synaptic transmission; ...however, the mechanism that regulates the morphological plasticity of astrocytes remains unclear. Recently, we reported that T1, a subtype of TrkB (a family of BDNF‐specific receptors), altered astrocytic morphology through the control of Rho GTPases in primary astrocyte cultures. In this study, we extended this observation to investigate acute neocortical slices from adult rats. T1 siRNA‐expression vectors were electroporated into astrocytes in neocortical layer I of living rats. In both normal slices and control vector‐electroporated slices, BDNF induced the elongation of the astrocytic processes and increased the branching of processes in slices after 1 h incubation. In contrast, in T1 siRNA‐electroporated slices, no such significant morphological changes were observed in the astrocytes. In addition, the number of synaptophysin+ sites in contact with GFAP+ processes increased in a BDNF–T1‐dependent manner without the increase in the total synaptophysin+ sites. Therefore, the present study provides evidence of the regulation of layer I astrocytic morphology by the BDNF–T1 signal in adult rat neocortical slices.
The mammalian neocortex develops layer organizations with regional differences represented by expression of multiple genes at embryonic stages. These genes could play important roles in the formation ...of areal cyto-architecture, yet, the number of genes identified so far is not sufficient to explain such intricate processes. Here we collected five regions — the medial, dorsal, lateral, rostral and occipital — from the dissected E16.5 mouse cerebral cortex and performed extensive gene expression analysis using the Affymetrix U74Av2 array with probes for 12 500 genes. After relative quantitative analysis, 34, 33 and 15 genes were selected as highly expressed genes in the medial, dorsal and lateral regions, respectively. The combination of GeneChip system, real-time quantitative reverse transcription polymerase chain reaction and in situ hybridization analyses allowed the successful identification of seven genes from the dorsal region (Neuropeptide Y, Wnt7b, TGF-β RI, Nrf3, Bcl-6, MT4-MMP and Rptpκ), three genes from the medial region (Hop-pending, HtrA and Crystallin), and three genes from the lateral region (Somatostatin, Ngef and Fxyd7). Particularly, all seven genes identified in the dorsal region demarcated the future somatosensory and auditory areas in the cortical plate with high rostrolateral–low caudomedial gradation. Their expression patterns were not uniform, but delineated either the superficial or the deep layer in the cortical plate. Furthermore, the regional expression pattern of Neuropeptide Y was shifted rostrally and the layer specificity was disorganized in the Pax6-deficient mice. Our results provide new information about a subclass of regionally expressed genes in the cortical plate at the late embryonic stage, which may help understand the molecular mechanisms of neocortical arealization.
The transcription factor Pax6 is essential for the development of the central nervous system and it exerts its multiple functions by regulating the expression of downstream target molecules. To ...screen for genes downstream of Pax6, we performed comprehensive transcriptome profiling analyses in the early hindbrain of Pax6 homozygous mutant and wild-type rats using microarrays.
Comparison of quadruplicate microarray experiments using two computational methods allowed us to identify differentially expressed genes that have relatively small fold changes or low expression levels. Gene ontology analyses of the differentially expressed molecules demonstrated that Pax6 is involved in various signal transduction pathways where it regulates the expression of many receptors, signaling molecules, transporters and transcription factors. The up- or down-regulation of these genes was further confirmed by quantitative RT-PCR. In situ staining of Fabp7, Dbx1, Unc5h1 and Cyp26b1 mRNAs showed that expression of these transcripts not only overlapped with that of Pax6 in the hindbrain of wild-type and Pax6 heterozygous mutants, but also was clearly reduced in the hindbrain of the Pax6 homozygous mutant. In addition, the Pax6 homozygous mutant hindbrain showed that Cyp26b1 expression was lacked in the dorsal and ventrolateral regions of rhombomeres 5 and 6, and that the size of rhombomere 5 expanded rostrocaudally.
These results indicate that Unc5h1 and Cyp26b1 are novel candidates for target genes transactivated by Pax6. Furthermore, our results suggest the interesting possibility that Pax6 regulates anterior-posterior patterning of the hindbrain via activation of Cyp26b1, an enzyme that metabolizes retinoic acid.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A membrane microdomain called raft has been under extensive study since the assembly of various signal-transducing molecules into this region has been envisaged. This domain is isolated as a low ...buoyant membrane fraction after the extraction with a nonionic detergent such as Triton X-100. The characteristic low density of this fraction is ascribed to the enrichment of several lipids including cholesterol. To clear the molecular mechanism of raft formation, several extraction methods were applied to solubilize raft components. Cholesterol extraction using methyl-β-cyclodextrin was found to be effective to solubilize NAP-22, a neuron-enriched Ca2+-dependent calmodulin-binding protein as well as one of the main protein components of brain raft. Purified NAP-22 bound to the liposomes that were made from phosphatidylcholine and cholesterol. This binding was dependent on the amount of cholesterol in liposomes. Calmodulin inhibited this binding in a dose-dependent manner. These results suggest that the presence of a calcium-dependent regulatory mechanism works on the assembly of raft within the neuron.
In the central nervous system, many cell adhesion molecules are known to participate in the establishment and remodeling of
the neural circuit. Some of the cell adhesion molecules are known to be ...anchored to the membrane by the glycosylphosphatidylinositol
(GPI) inserted to their C termini, and many GPI-anchored proteins are known to be localized in a Triton-insoluble membrane
fraction of low density or so-called âraft.â In this study, we surveyed the GPI-anchored proteins in the Triton-insoluble
low density fraction from 2-week-old rat brain by solubilization with phosphatidylinositol-specific phospholipase C. By Western
blotting and partial peptide sequencing after the deglycosylation with peptide N -glycosidase F, the presence of Thy-1, F3/contactin, and T-cadherin was shown. In addition, one of the major proteins, having
an apparent molecular mass of 36 kDa after the peptide N -glycosidase F digestion, was found to be a novel protein. The result of cDNA cloning showed that the protein is an immunoglobulin
superfamily member with three C2 domains and has six putative glycosylation sites. Since this protein shows high sequence
similarity to IgLON family members including LAMP, OBCAM, neurotrimin, CEPU-1, AvGP50, and GP55, we termed this protein Kilon
(a ki ndred of Ig LON ). Kilon-specific monoclonal antibodies were produced, and Western blotting analysis showed that expression of Kilon is restricted
to brain, and Kilon has an apparent molecular mass of 46 kDa in SDS-polyacrylamide gel electrophoresis in its expressed form.
In brain, the expression of Kilon is already detected in E16 stage, and its level gradually increases during development.
Kilon immunostaining was observed in the cerebral cortex and hippocampus, in which the strongly stained puncta were observed
on dendrites and soma of pyramidal neurons.
Adult mammalian neurogenesis occurs in the hippocampus and the olfactory bulb, whereas neocortical adult neurogenesis remains controversial. Several occurrences of neocortical adult neurogenesis in ...injured neocortex were recently reported, suggesting that neural stem cells (NSCs) or neuronal progenitor cells (NPCs) that can be activated by injury are maintained in the adult brain. However, it is not clear whether or where neocortical NSCs/NPCs exist in the brain. We found NPCs in the neocortical layer 1 of adult rats and observed that their proliferation was highly activated by global forebrain ischemia. Using retrovirus-mediated labeling of layer 1 proliferating cells with membrane-targeted green fluorescent protein, we found that the newly generated neurons were GABAergic and that the neurons were functionally integrated into the neuronal circuitry. Our results suggest that layer 1 NPCs are a source of adult neurogenesis under ischemic conditions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Little is known about the architecture of cellular microenvironments that support stem and precursor cells during tissue development. Although adult stem cell niches are organized by specialized ...supporting cells, in the developing cerebral cortex, neural stem/precursor cells reside in a neurogenic niche lacking distinct supporting cells. Here, we find that neural precursors themselves comprise the niche and regulate their own development. Precursor-precursor contact regulates β-catenin signaling and cell fate. In vivo knockdown of N-cadherin reduces β-catenin signaling, migration from the niche, and neuronal differentiation in vivo. N-cadherin engagement activates β-catenin signaling via Akt, suggesting a mechanism through which cells in tissues can regulate their development. These results suggest that neural precursor cell interactions can generate a self-supportive niche to regulate their own number.
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► Cortical ventricular zone neural precursors exhibit β-catenin signaling ► N-cadherin maintains β-catenin signaling in cortical precursors ► N-cadherin regulates neuronal differentiation and cell cycle exit via β-catenin ► N-cadherin signals through Akt and phosphor-Ser552 of β-catenin
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