At the optic chiasm choice point, ipsilateral retinal ganglion cells (RGCs) are repelled away from the midline by guidance cues, including Ephrin-B2 and Sonic Hedgehog (Shh). Although guidance cues ...are normally produced by cells residing at the choice point, the mRNA for Shh is not found at the optic chiasm. Here we show that Shh protein is instead produced by contralateral RGCs at the retina, transported anterogradely along the axon, and accumulates at the optic chiasm to repel ipsilateral RGCs. In vitro, contralateral RGC axons, which secrete Shh, repel ipsilateral RGCs in a Boc- and Smo-dependent manner. Finally, knockdown of Shh in the contralateral retina causes a decrease in the proportion of ipsilateral RGCs in a non-cell-autonomous manner. These findings reveal a role for axon-axon interactions in ipsilateral RGC guidance, and they establish that remotely produced cues can act at axon guidance midline choice points.
•Shh protein is produced by RGCs in the retina and transported to the optic chiasm•Shh is secreted by contralateral RGCs at the chiasm to repel ipsilateral RGCs•The repulsive effect of Shh requires the receptor Boc and signaling mediator Smo•Remotely produced cues and axon-axon interactions are important in chiasm guidance
Although axon guidance cues are typically produced locally at the choice point, Peng et al. show that Shh is transported by RGCs from the retina to the optic chiasm to repel ipsilateral RGC axons trans-axonally.
In contrast to stage-specific transcription factors, the role of ubiquitous transcription factors in neuronal development remains a matter of scrutiny. Here, we demonstrated that a ubiquitous factor ...NF-Y is essential for neural progenitor maintenance during brain morphogenesis. Deletion of the NF-YA subunit in neural progenitors by using nestin-cre transgene in mice resulted in significant abnormalities in brain morphology, including a thinner cerebral cortex and loss of striatum during embryogenesis. Detailed analyses revealed a progressive decline in multiple neural progenitors in the cerebral cortex and ganglionic eminences, accompanied by induced apoptotic cell death and reduced cell proliferation. In neural progenitors, the NF-YA short isoform lacking exon 3 is dominant and co-expressed with cell cycle genes. ChIP-seq analysis from the cortex during early corticogenesis revealed preferential binding of NF-Y to the cell cycle genes, some of which were confirmed to be downregulated following NF-YA deletion. Notably, the NF-YA short isoform disappears and is replaced by its long isoform during neuronal differentiation. Forced expression of the NF-YA long isoform in neural progenitors resulted in a significant decline in neuronal count, possibly due to the suppression of cell proliferation. Collectively, we elucidated a critical role of the NF-YA short isoform in maintaining neural progenitors, possibly by regulating cell proliferation and apoptosis. Moreover, we identified an isoform switch in NF-YA within the neuronal lineage in vivo, which may explain the stage-specific role of NF-Y during neuronal development.
Golli–myelin basic proteins, encoded by the myelin basic protein gene, are widely expressed in neurons and oligodendrocytes in the central nervous system. Further, prior research has shown that ...Golli–myelin basic protein is necessary for myelination and neuronal maturation during central nervous system development. In this study, we established Golli–myelin basic protein-floxed mice to elucidate the cell-type-specific effects of Golli–myelin basic protein knockout through the generation of conditional knockout mice (
Golli
–
myelin basic proteins
fl/fl
; E3CreN
), in which Golli–myelin basic proteins were specifically deleted in cerebellar granule neurons, where Golli–myelin basic proteins are expressed abundantly in wild-type mice. To investigate the role of Golli–myelin basic proteins in cerebellar granule neurons, we further performed histopathological analyses of these mice, with results indicating no morphological changes or degeneration of the major cellular components of the cerebellum. Furthermore, behavioral analysis showed that
Golli
–
myelin basic proteins
fl/fl
; E3CreN
mice were healthy and did not display any abnormal behavior. These results suggest that the loss of Golli–myelin basic proteins in cerebellar granule neurons does not lead to cerebellar perturbations or behavioral abnormalities. This mouse model could therefore be employed to analyze the effect of Golli–myelin basic protein deletion in specific cell types of the central nervous system, such as other neuronal cells and oligodendrocytes, or in lymphocytes of the immune system.
The diversity of neural stem cells is a hallmark of the cerebral cortex development in gyrencephalic mammals, such as Primates and Carnivora. Among them, ferrets are a good model for mechanistic ...studies. However, information on their neural progenitor cells (NPC), termed radial glia (RG), is limited. Here, we surveyed the temporal series of single-cell transcriptomes of progenitors regarding ferret corticogenesis and found a conserved diversity and temporal trajectory between human and ferret NPC, despite the large timescale difference. We found truncated RG (tRG) in ferret cortical development, a progenitor subtype previously described in humans. The combination of in silico and in vivo analyses identified that tRG differentiate into both ependymal and astrogenic cells. Via transcriptomic comparison, we predict that this is also the case in humans. Our findings suggest that tRG plays a role in the formation of adult ventricles, thereby providing the architectural bases for brain expansion.
Abstract
We previously identified quantitative trait loci (QTL) for prepulse inhibition (PPI), an endophenotype of schizophrenia, on mouse chromosome 10 and reported Fabp7 as a candidate gene from an ...analysis of F2 mice from inbred strains with high (C57BL/6N; B6) and low (C3H/HeN; C3H) PPI levels. Here, we reanalyzed the previously reported QTLs with increased marker density. The highest logarithm of odds score (26.66) peaked at a synonymous coding and splice-site variant, c.753G>A (rs257098870), in the Cdh23 gene on chromosome 10; the c.753G (C3H) allele showed a PPI-lowering effect. Bayesian multiple QTL mapping also supported the same variant with a posterior probability of 1. Thus, we engineered the c.753G (C3H) allele into the B6 genetic background, which led to dampened PPI. We also revealed an e-QTL (expression QTL) effect imparted by the c.753G>A variant for the Cdh23 expression in the brain. In a human study, a homologous variant (c.753G>A; rs769896655) in CDH23 showed a nominally significant enrichment in individuals with schizophrenia. We also identified multiple potentially deleterious CDH23 variants in individuals with schizophrenia. Collectively, the present study reveals a PPI-regulating Cdh23 variant and a possible contribution of CDH23 to schizophrenia susceptibility.
Bone morphogenic protein-4 (BMP4) and fibroblast growth factor-8 (FGF8) are thought to have opposite roles in defining epithelial versus neurogenic fate in the developing olfactory/vomeronasal ...system. In particular, FGF8 has been implicated in specification of olfactory and gonadotropin releasing hormone-1 (GnRH) neurons, as well as in controlling olfactory stem cell survival. Using different knock-in mouse lines and Cre-lox-mediated lineage tracing, Fgf8 expression and cell lineage was analyzed in the developing nose in relation to the expression of Bmp4 and its antagonist Noggin (Nog). FGF8 is expressed by cells that acquire an epidermal, respiratory cell fate and not by stem cells that acquire neuronal olfactory or vomeronasal cell fate. Ectodermal and mesenchymal sources of BMP4 control the expression of BMP/TGFβ antagonist Nog, whereas mesenchymal sources of Nog define the neurogenic borders of the olfactory pit. Fgf8 hypomorph mouse models, Fgf8(neo/neo) and Fgf8(neo/null), displayed severe craniofacial defects together with overlapping defects in the olfactory pit including (1) lack of neuronal formation ventrally, where GnRH neurons normally form, and (2) altered expression of Bmp4 and Nog, with Nog ectopically expressed in the nasal mesenchyme and no longer defining the GnRH and vomeronasal neurogenic border. Together our data show that (1) FGF8 is not sufficient to induce ectodermal progenitors of the olfactory pit to acquire neural fate and (2) altered neurogenesis and lack of GnRH neuron specification after chronically reduced Fgf8 expression reflected dysgenesis of the nasal region and loss of a specific neurogenic permissive milieu that was defined by mesenchymal signals.
Anti-tumor activity of antizyme which targets the ornithine decarboxylase (ODC) required for cell growth and transformation Cell proliferation and transformation induced by growth factor stimulation ...or by carcinogens, viruses, or oncogenes are characterized by an associated increase in polyamine levels, which is mediated by increased polyamine biosynthesis and enhanced uptake of polyamines. Polyamine biosynthesis is catalyzed particularly, in the level of ornithine decarboxylase (ODC). The elevation of cellular polyamine levels on the other hand accelerates the induction of ornithine decarboxylase antizyme (antizyme), which is involved not only in ODC-degradation, but in the negative regulation of polyamine transport. Taking advantage of these characteristics of antizyme, the potential of antizyme as a factor having anti-cell growth and anti-tumor activity was investigated. We show that antizyme can induce cell death associated with a rapid decline of intracellular polyamine contents. The possible anti-tumor activities of ectopically expressed antizyme were tested in p21H-ras (Val 12)-transformed NIH3T3 cells and several human malignant cell lines including a line with loss of p53 expression, and they were shown to be as sensitive as nontransformed NIH3T3 cells in vitro. The in vivo anti-tumor activity was also tested using nude mice inoculated with H-ras transformed NIH3T3 cells that had been transfected with inducible antizyme expression vector and the results showed that antizyme expression in vivo blocks tumor formation in these mice. These results suggest that ectopic antizyme expression is of possible therapeutic benefit in the treatment of cancer, which is mediated by ODC inactivation and intracellular polyamine depletion.
The upstream transcription factors (USFs) USF1 and USF2 are ubiquitously expressed transcription factors that are characterized by a conserved basic helix‐loop‐helix/leucine zipper DNA‐binding ...domain. They form homo‐ or heterodimers, and recognize E‐box motifs to modulate gene expression. They are known to regulate diverse cellular functions, including the cell cycle, immune responses and glucose/lipid metabolism, but their roles in neuronal cells remain to be clarified. Here, we performed chromatin immunoprecipitation of USF1 from mouse brain cortex. Subsequent promoter array analysis (ChIP‐chip) indicated that USF1 exclusively bound to the CACGTG E‐box motifs in the proximal promoter regions. Importantly, functional annotation of the USF1‐binding targets revealed an enrichment of genes related to lysosomal functions. Gene expression array analysis using a neuronal cell line subsequently revealed that knockdown of USFs de‐regulated lysosomal gene expression. Altered expression was validated by quantitative RT‐PCR, supporting the conclusion that USFs regulate lysosomal gene expression. Furthermore, USF knockdown slightly increased LysoTracker Red staining, implying a role for USFs in modulating lysosomal homeostasis. Together, our comprehensive genome‐scale analyses identified lysosomal genes as targets of USFs in neuronal cells, suggesting a potential additional pathway of lysosomal regulation.
Database
The data for the gene expression array and ChIP‐chip have been submitted to the Gene Expression Omnibus (GEO) under accession numbers GSE76615 and GSE76616, respectively.
Upstream stimulating factors, USF1/2, are ubiquitous transcription factors binding to E‐box motifs. To clarify their neuronal functions, we performed ChIP‐chip and gene expression array analyses using neuronal cells. Functional annotation revealed high enrichment of lysosomal genes in both analyses, and their altered expressions were confirmed by qRT‐PCR. Our observations suggest USF1/2 as novel modulators of lysosomal genes in neuronal cells.
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