RESUMO
The Mi-2 protein is the central component of the recently isolated NuRD nucleosome remodelling and histone deacetylase complex. Although the NuRD complex has been the subject of extensive biochemical analyses, little is known about its biological function. Here we show that the two C. elegans Mi-2 homologues, LET-418 and CHD-3, play essential roles during development. The two proteins possess both shared and unique functions during vulval cell fate determination, including antagonism of the Ras signalling pathway required for vulval cell fate induction and the proper execution of the 2 degrees cell fate of vulval precursor cells, a process under the control of LIN-12 Notch signalling.
Assuntos
Adenosina Trifosfatases , Autoantígenos/fisiologia , Proteínas de Caenorhabditis elegans , Caenorhabditis elegans/crescimento & desenvolvimento , DNA Helicases , Vulva/crescimento & desenvolvimento , Animais , Animais Geneticamente Modificados , Autoantígenos/genética , Sequência de Bases , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Diferenciação Celular , Primers do DNA/genética , Feminino , Genes de Helmintos , Proteínas de Helminto/fisiologia , Proteínas de Membrana/fisiologia , Complexo Mi-2 de Remodelação de Nucleossomo e Desacetilase , Fenótipo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores Notch , Transdução de Sinais , Células-Tronco/citologia , Células-Tronco/metabolismo , Vulva/citologiaRESUMO
To contribute to the development of the transcription map of human chromosome 21 (HC21), we isolated a new transcript, C21orf5 (chromosome 21 open reading frame 5), encoding a predicted 2298-amino-acid protein. Analysis of the genomic DNA sequence revealed that C21orf5 consists of 37 exons that extend over 130 kb and maps between the CBR3 (carbonyl reductase 3) and the KIAA0136 genes. Northern blot analyses showed a ubiquitously expressed RNA species of 8.5 kb. RNA in situ hybridization on brain sections of normal human embryos revealed a strong labeling in restricted areas of the cerebral cortex. In silico analysis of the deduced C21orf5 protein revealed several highly probable transmembrane segments but no known protein domains or homology with known proteins. However, there were significant homologies to several hypothetical Caenorhabditis elegans proteins and Drosophila melanogaster genomic sequences. To investigate the function of C21orf5, we isolated the cDNA of the C. elegans ortholog and performed double-stranded RNA-mediated genetic interference experiments. The major phenotype observed in the progeny of injected animals was embryonic lethality. Most of the tissues of the embryo failed to undergo proper patterning during gastrulation, and morphogenesis did not occur; thus we termed the ortholog pad-1, for patterning defective 1. These results indicated that pad-1 is essential for the development and the survival of C. elegans. This study provides the first example of the use of C. elegans as a model to study the function of genes on human chromosome 21 that might be involved in Down syndrome.
Assuntos
Padronização Corporal/genética , Caenorhabditis elegans/genética , Cromossomos Humanos Par 21/genética , Proteínas de Membrana/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Northern Blotting , Padronização Corporal/efeitos dos fármacos , Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/embriologia , Proteínas de Caenorhabditis elegans , DNA Complementar/química , DNA Complementar/genética , Embrião de Mamíferos/metabolismo , Embrião não Mamífero/efeitos dos fármacos , Embrião não Mamífero/metabolismo , Éxons , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Genes/genética , Humanos , Hibridização In Situ , Íntrons , Masculino , Dados de Sequência Molecular , RNA de Cadeia Dupla/administração & dosagem , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Alinhamento de Sequência , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Distribuição Tecidual , Proteínas de Transporte VesicularRESUMO
The Caenorhabditis elegans lin-39, mab-5 and egl-5 Hox genes specify cell fates along the anterior-posterior body axis of the nematode during postembryonic development, but little is known about Hox gene functions during embryogenesis. Here, we show that the C. elegans labial-like gene ceh-13 is expressed in cells of many different tissues and lineages and that the rostral boundary of its expression domain is anterior to those of the other Hox genes. By transposon-mediated mutagenesis, we isolated a zygotic recessive ceh-13 loss-of-function allele, sw1, that exhibits an embryonic sublethal phenotype. Lineage analyses and immunostainings revealed defects in the organization of the anterior lateral epidermis and anterior body wall muscle cells. The epidermal and mesodermal identity of these cells, however, is correctly specified. ceh-13(sw1) mutant embryos also show fusion and adhesion defects in ectodermal cells. This suggests that ceh-13 plays a role in the anterior organization of the C. elegans embryo and is involved in the regulation of cell affinities.
Assuntos
Proteínas de Caenorhabditis elegans , Caenorhabditis elegans/embriologia , Regulação da Expressão Gênica no Desenvolvimento/genética , Genes de Helmintos , Genes Homeobox/genética , Proteínas de Homeodomínio/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Clonagem Molecular , Embrião não Mamífero , Genes Letais/genética , Proteínas de Homeodomínio/química , Imuno-Histoquímica , Dados de Sequência Molecular , Morfogênese , Fenótipo , Deleção de Sequência/genéticaRESUMO
Clusters of homeobox-containing HOM-C/hox genes determine the morphology of animal body plans and body parts and are thought to mediate positional information. Here, we describe the onset of embryonic expression of ceh-13, the Caenorhabditis elegans orthologue of the Drosophila labial gene, which is the earliest gene of the C. elegans Hox gene cluster to be activated in C. elegans development. At the beginning of gastrulation, ceh-13 is asymmetrically expressed in posterior daughters of anteroposterior divisions, first in the posterior daughter of the intestinal precursor cell E and then in all posterior daughters of the AB descendants ABxxx. In this paper, we present evidence that supports position-independent activation of ceh-13 during early C. elegans embryogenesis, which integrates cell fate determinants and cell polarity cues. Our findings imply that mechanisms other than cell-extrinsic anteroposterior positional signals play an important role in the activation and regulation of the C. elegans Hox gene ceh-13.