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R Kageyama

Publications and source records attributed to R Kageyama.

At least 37 records · Page 2Linked to original sources
PubMed2000

Hes genes regulate sequential stages of neurogenesis in the olfactory epithelium.

We have characterised the functions of the bHLH transcriptional repressors HES1 and HES5 in neurogenesis, using the development of the olfactory placodes in mouse embryos as a model. Hes1 and Hes5 are expressed with distinct patterns in the olfactory placodes and are subject to different regulatory mechanisms. Hes1 is expressed in a broad placodal domain, which is maintained in absence of the neural determination gene Mash1. In contrast, expression of Hes5 is restricted to clusters of neural progenitor cells and requires Mash1 function. Mutations in Hes1 and Hes5 also have distinct consequences on olfactory placode neurogenesis. Loss of Hes1 function leads both to expression of Mash1 outside of the normal domain of neurogenesis and to increased density of MASH1-positive progenitors within this domain, and results in an excess of neurons after a delay. A mutation in Hes5 does not produce any apparent defect. However, olfactory placodes that are double mutant for Hes1 and Hes5 upregulate Ngn1, a neural bHLH gene activated downstream of Mash1, and show a strong and rapid increase in neuronal density. Together, our results suggest that Hes1 regulates Mash1 transcription in the olfactory placode in two different contexts, initially as a prepattern gene defining the placodal domain undergoing neurogenesis and, subsequently, as a neurogenic gene controlling the density of neural progenitors in this domain. Hes5 synergizes with Hes1 and regulates neurogenesis at the level of Ngn1 expression. Therefore, the olfactory sensory neuron lineage is regulated at several steps by negative signals acting through different Hes genes and targeting the expression of different proneural gene homologs.

Animals↗
PubMed2000

Glial cell fate specification modulated by the bHLH gene Hes5 in mouse retina.

Neurons and glial cells differentiate from common precursors. Whereas the gene glial cells missing (gcm) determines the glial fate in Drosophila, current data about the expression patterns suggest that, in mammals, gcm homologues are unlikely to regulate gliogenesis. Here, we found that, in mouse retina, the bHLH gene Hes5 was specifically expressed by differentiating Müller glial cells and that misexpression of Hes5 with recombinant retrovirus significantly increased the population of glial cells at the expense of neurons. Conversely, Hes5-deficient retina showed 30-40% decrease of Müller glial cell number without affecting cell survival. These results indicate that Hes5 modulates glial cell fate specification in mouse retina.

Animals↗
PubMed2000

The bHLH gene Hes6, an inhibitor of Hes1, promotes neuronal differentiation.

We have isolated the basic helix-loop-helix (bHLH) gene Hes6, a novel member of the family of mammalian homologues of Drosophila hairy and Enhancer of split. Hes6 is expressed by both undifferentiated and differentiated cells, unlike Hes1, which is expressed only by the former cells. Hes6 alone does not bind to the DNA but suppresses Hes1 from repressing transcription. In addition, Hes6 suppresses Hes1 from inhibiting Mash1-E47 heterodimer and thereby enables Mash1 and E47 to upregulate transcription in the presence of Hes1. Furthermore, misexpression of Hes6 with retrovirus in the developing retina promotes rod photoreceptor differentiation, like Mash1, in sharp contrast to Hes1, which inhibits cell differentiation. These results suggest that Hes6 is an inhibitor of Hes1, supports Mash1 activity and promotes cell differentiation. Mutation analysis revealed that Hes1- and Hes6-specific functions are, at least in part, interchangeable by alteration of the loop region, suggesting that the loop is not simply a nonfunctional spacer but plays an important role in the specific functions.

3T3 Cells↗
PubMed2000

Basic helix-loop-helix transcription factors regulate the neuroendocrine differentiation of fetal mouse pulmonary epithelium.

To clarify the mechanisms that regulate neuroendocrine differentiation of fetal lung epithelia, we have studied the expression of the mammalian homologs of achaete-scute complex (Mash1) (Ascl1 - Mouse Genome Informatics); hairy and enhancer of split1 (Hes1); and the expression of Notch/Notch-ligand system in the fetal and adult mouse lungs, and in the lungs of Mash1- or Hes1-deficient mice. Immunohistochemical studies revealed that Mash1-positive cells seemed to belong to pulmonary neuroendocrine cells (PNEC) and their precursors. In mice deficient for Mash1, no PNEC were detected. Hes1-positive cells belong to non-neuroendocrine cells. In the mice deficient in Hes1, in which Mash1 mRNA was upregulated, PNEC appeared precociously, and the number of PNEC was markedly increased. NeuroD (Neurod1 - Mouse Genome Informatics) expression in the lung was detected in the adult, and was enhanced in the fetal lungs of Hes1-null mice. Expression of Notch1, Notch2, Notch3 and Notch4 mRNAs in the mouse lung increased with age, and Notch1 mRNA was expressed in a Hes1-dependent manner. Notch1, Notch2 and Notch3 were immunohistochemically detected in non-neuroendocrine cells. Moreover, analyses of the lungs from the gene-targeted mice suggested that expression of Delta-like 1 (Dll1 - Mouse Genome Informatics) mRNA depends on Mash1. Thus, the neuroendocrine differentiation depends on basic helix-loop-helix factors, and Notch/Notch-ligand pathways may be involved in determining the cell differentiation fate in fetal airway epithelium.

Aging↗
PubMed2000

Hes1 is a negative regulator of inner ear hair cell differentiation.

Hair cell fate determination in the inner ear has been shown to be controlled by specific genes. Recent loss-of-function and gain-of-function experiments have demonstrated that Math1, a mouse homolog of the Drosophila gene atonal, is essential for the production of hair cells. To identify genes that may interact with Math1 and inhibit hair cell differentiation, we have focused on Hes1, a mammalian hairy and enhancer of split homolog, which is a negative regulator of neurogenesis. We report here that targeted deletion of Hes1 leads to formation of supernumerary hair cells in the cochlea and utricle of the inner ear. RT-PCR analysis shows that Hes1 is expressed in inner ear during hair cell differentiation and its expression is maintained in adulthood. In situ hybridization with late embryonic inner ear tissue reveals that Hes1 is expressed in supporting cells, but not hair cells, of the vestibular sensory epithelium. In the cochlea, Hes1 is selectively expressed in the greater epithelial ridge and lesser epithelial ridge regions which are adjacent to inner and outer hair cells. Co-transfection experiments in postnatal rat explant cultures show that overexpression of Hes1 prevents hair cell differentiation induced by Math1. Therefore Hes1 can negatively regulate hair cell differentiation by antagonizing Math1. These results suggest that a balance between Math1 and negative regulators such as Hes1 is crucial for the production of an appropriate number of inner ear hair cells.

Animals↗
PubMed2000

Goosecoid suppresses cell growth and enhances neuronal differentiation of PC12 cells.

In all vertebrate species, the homeobox gene goosecoid serves as a marker of the Spemann organizer tissue. One function of the organizer is the induction of neural tissue. To investigate the role of goosecoid in neuronal differentiation of mammalian cells, we have introduced goosecoid into PC12 cells. Expression of goosecoid resulted in reduced cell proliferation and enhanced neurite outgrowth in response to NGF. Expression of goosecoid led to a decrease in the percentage of S-phase cells and to upregulation of the expression of the neuron-specific markers MAP-1b and neurofilament-L. Analysis of goosecoid mutants revealed that these effects were independent of either DNA binding or homodimerization of Goosecoid. Coexpression of the N-terminal portion of the ets transcription factor PU.1, a protein that can bind to Goosecoid, repressed neurite outgrowth and rescued the proliferation of PC12 cultures. In contrast, expression of the bHLH transcription factor HES-1 repressed goosecoid-mediated neurite outgrowth without changing the proportion of S-phase cells. These results suggest that goosecoid is involved in neuronal differentiation in two ways, by slowing the cell cycle and stimulating neurite outgrowth, and that these two events are separately regulated.

Animals↗
PubMed1999

The bHLH gene Hes1 is essential for expansion of early T cell precursors.

Mice mutant for the bHLH gene Hes1, which is known to keep cells in a proliferative state, mostly lack thymus. Transfer of Hes1-null fetal liver cells into RAG2-null host mice normally reconstitutes B cells but fails to generate mature T cells in the thymus. In the reconstituted thymus, T cell differentiation is arrested at the CD4(-)CD8(-) double negative (DN) stage. Both the initial T cell receptor (TCR)-independent and the subsequent TCR-dependent selective expansion during the DN stage are severely affected. Thus, Hes1 is essential for the earliest thymocyte expansion in a cell-autonomous manner.

Animals↗
PubMed1999

Hes1 and Hes5 as notch effectors in mammalian neuronal differentiation.

While the transmembrane protein Notch plays an important role in various aspects of development, and diseases including tumors and neurological disorders, the intracellular pathway of mammalian Notch remains very elusive. To understand the intracellular pathway of mammalian Notch, the role of the bHLH genes Hes1 and Hes5 (mammalian hairy and Enhancer-of-split homologues) was examined by retrovirally misexpressing the constitutively active form of Notch (caNotch) in neural precursor cells prepared from wild-type, Hes1-null, Hes5-null and Hes1-Hes5 double-null mouse embryos. We found that caNotch, which induced the endogenous Hes1 and Hes5 expression, inhibited neuronal differentiation in the wild-type, Hes1-null and Hes5-null background, but not in the Hes1-Hes5 double-null background. These results demonstrate that Hes1 and Hes5 are essential Notch effectors in regulation of mammalian neuronal differentiation.

Animals↗
PubMed1999

The Notch-Hes pathway in mammalian neural development.

A wide variety of neurons and glial cells differentiate from common precursor cells in the developing nervous system. During this process, Notch-mediated cell-cell interaction is essential for maintenance of dividing cells and subsequent generation of cell type diversity. Activation of Notch inhibits cellular differentiation, and abnormality of the Notch pathway leads to premature neuronal differentiation, the lack of some cell types, and severe defects of tissue morphogenesis. Recent data demonstrate that Notch fails to inhibit cellular differentiation in the absence of the bHLH genes Hes1 and Hes5, which functionally antagonize the neuronal bHLH genes such as Mash1. These results indicate that the two Hes genes are essential effectors for the Notch pathway and that neuronal differentiation is controlled by the pathway "Notch-Hes1/Hes5-|Mash1".

Animals↗
PubMed1999

Ectopic expression of the bHLH gene Math1 disturbs neural development.

The basic helix-loop-helix gene Math1, a positive regulator of neuronal differentiation, is specifically expressed in the dorsal part of the developing nervous system. To determine the effects of ectopic expression of Math1, we generated two transgenic mouse lines; One carried the Cre recombinase gene under the control of the nestin promoter and enhancer, which direct expression in neural precursor cells, and the other carried the Math1 gene, the expression of which was regulated by the cytomegalovirus (CMV) promoter but interrupted by the stop cassette flanked by loxP sites. In F1 embryos that carried the two transgenes, the stop cassette was removed by Cre recombinase in the developing nervous system, and Math1 expression was ectopically directed from the CMV promoter. We found that these embryos exhibited abnormal morphology of the brain and extensive cell death in the nervous system. These results suggest that ectopic expression of Math1 is toxic to neurons and leads to apoptosis.

Animals↗
PubMed1999

Transcriptional regulation of mouse type 1 inositol 1,4,5-trisphosphate receptor gene by NeuroD-related factor.

The type 1 inositol 1,4,5-trisphosphate receptor (IP3R1) is a Ca2+ channel protein that is expressed abundantly in the CNS, such as in the cerebellar Purkinje cells and hippocampus. We previously demonstrated that the box-I element, which is located -334 relative to the transcription initiation site of the mouse IP3R1 gene and includes an E-box consensus sequence, is involved in the up-regulation of such IP3R1 gene expression. Furthermore, the previous study also indicated that some CNS-related basic helix-loop-helix (bHLH) factors bind to the box-I and activate IP3R1 gene expression. In this study, we demonstrated that one of the CNS-related bHLH factors, neuronal differentiation factor (NeuroD)-related factor (NDRF), specifically bound to the box-I sequence with a ubiquitously expressed bHLH protein, E47, and activated IP3R1 gene expression. In situ hybridization of adult mouse brain revealed that IP3R1 and NDRF mRNA were co-expressed in many subsets of neurons, highly in Purkinje cells and hippocampus and moderately in cerebral cortex, olfactory bulb, and caudate putamen. Furthermore, the spatiotemporal expression patterns of these two genes resembled one another throughout postnatal development of the mouse CNS. From these results, we suggest that NDRF is involved in the tissue-specific regulation of IP3R1 gene expression in the CNS.

Animals↗
PubMed1998

Structure, chromosomal locus, and promoter of mouse Hes2 gene, a homologue of Drosophila hairy and Enhancer of split.

Hes2 encodes a mammalian basic helix-loop-helix transcriptional repressor homologous to the products of Drosophila hairy and Enhancer of split. Here, we isolated and characterized the mouse Hes2 gene. This gene consists of four exons, and all the introns are located within the protein-coding region at positions homologous to those of other Hes genes. On the inter-specific backcross analyses, mouse Hes2 is mapped to the distal region of Chromosome 4 near the Hes3 and Hes5 loci, which are different from the Hes1 locus on Chromosome 16. Upstream of the transcription initiation site, there are GC-rich regions, but a typical TATA box is not present. Transient transfection analyses demonstrated that, while Hes1 and Hes5 promoter activities are significantly upregulated by the active form of Notch, a key regulator of cellular differentiation, Hes2 and Hes3 promoter activities are not. These results suggest that Hes genes are functionally classified into two groups: those that are regulated by Notch and those that are not.

Amino Acid Sequence↗
PubMed1998

Structure and promoter analysis of Math3 gene, a mouse homolog of Drosophila proneural gene atonal. Neural-specific expression by dual promoter elements.

ath3, a vertebrate basic helix-loop-helix gene homologous to Drosophila proneural gene atonal, can directly convert non-neural cells into neurons with the anterior features. In the mouse, ath3 expression initially occurs widely in the developing nervous system and then gradually becomes restricted to the neural retina. Here, we characterized the genomic organization and promoter activity of mouse ath3 (Math3). Math3 gene consists of two exons separated by an 8-kilobase intron, and the whole protein-coding region is located in the second exon. Transcription starts at two sites, which are 75 nucleotides apart from each other, and there is no typical TATA box in the upstream region of either start site. Transient transfection analysis showed that the 5'-region of Math3 can direct efficient expression in neuroblastoma cells but not in glioma or fibroblast cells. Deletion studies revealed that the proximal 193-base pair region, which contains the downstream transcription initiation site but not the upstream site, is essential for the Math3 promoter activity and can direct efficient expression in neuroblastoma cells. In contrast, retrovirus-mediated promoter analysis demonstrated that a region further upstream is additionally necessary for retinal expression. These results indicate that Math3 promoter contains two essential regulatory regions, the proximal 193-base pair region, which confers efficient neural-specific expression, and a region further upstream, required for retinal expression.

Animals↗
PubMed1998

Regulated expression of neurogenic basic helix-loop-helix transcription factors during differentiation of the immortalized neuronal progenitor cell line HC2S2 into neurons.

Expression of nine neurogenic basic helix-loop-helix (bHLH) transcription factors was examined in an immortalized neuronal progenitor cell line HC2S2, which differentiates into neurons after suppression of the v-myc expression with tetracycline. Expression of MASH-1, NeuroD, NeuroD-related factor (NDRF) and HES-1 was demonstrated in HC2S2 cells by Northern blot analysis using total RNA. Expression of MASH-1 mRNA was downregulated upon differentiation of HC2S2 cells into mature neurons. In contrast, NeuroD and NDRF mRNA expression was maintained all through the differentiation. The expression of HES-1, a negative regulator of the neuronal differentiation, was upregulated temporarily in accordance with the suppression of the v-myc expression and was downregulated upon the differentiation of HC2S2 cells into neurons. The reduced expression of HES-1 mRNA in undifferentiated HC2S2 cells may be explained by the transcriptional suppression of HES-1 by the myc oncoprotein. The above data imply that both HES-1 and MASH-1 need to be downregulated at the time of accomplishment of the terminal differentiation into mature neurons and that NeuroD and NDRF participate in the regulatory process of the terminal differentiation in combination.

Animals↗