RESUMEN
The SWI/SNF-like chromatin remodeling complexes consist of two evolutionarily conserved subclasses, which are characterized by specific accessory components, the OSA/BAF250 and Polybromo proteins. These complexes regulate the expressions of distinct sets of target genes, with some overlap, and the regulatory components are thought to determine the target specificity for each complex. Here we isolated C. elegans mutants of the genes for the OSA/BAF250 homolog, LET-526, and the Polybromo homolog, PBRM-1, in a screen for the abnormal asymmetric cell division phenotype. In the asymmetric division of the T cell, both LET-526 and PBRM-1 regulated the asymmetric expression of psa-3/Meis between the T cell daughters, suggesting that the two subclasses share the same target. In the gonad, PBRM-1 regulated gonad primordium formation during embryogenesis, whereas LET-526 was required post-embryonically for distal tip cell (DTC) production from the gonad primordium, suggesting that these proteins have distinct targets for DTC development. Thus, the same cellular process is regulated by LET-526 and PBRM-1 in the asymmetric division of the T cell, but they regulate distinct cellular processes in the gonad morphogenesis. Although disruption of the core component PSA-1 or PSA-4 caused similar defects in the gonad and T cell, it also caused early embryonic arrest, which was not observed in the let-526, pbrm-1, or let-526 pbrm-1 double mutants, suggesting that some targets of SWI/SNF-like complexes do not require LET-526 or PBRM-1 for their transcription. Our results show that the target selection by SWI/SNF-like complexes during C. elegans development is intricately regulated by accessory components.
Asunto(s)
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/embriología , Caenorhabditis elegans/metabolismo , Ensamble y Desensamble de Cromatina , Animales , Caenorhabditis elegans/citología , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/genética , Linaje de la Célula , Proteínas Cromosómicas no Histona/metabolismo , Clonación Molecular , Desarrollo Embrionario/genética , Genes de Helminto/genética , Gónadas/citología , Gónadas/crecimiento & desarrollo , Gónadas/metabolismo , Mitosis/genética , Mutación/genética , Fenotipo , Transporte de Proteínas , Factores de Transcripción/metabolismo , Vía de Señalización Wnt/genéticaRESUMEN
During development, cell polarization is often coordinated to harmonize tissue patterning and morphogenesis. However, how extrinsic signals synchronize cell polarization is not understood. In Caenorhabditis elegans, most mitotic cells are polarized along the anterior-posterior axis and divide asymmetrically. Although this process is regulated by a Wnt-signaling pathway, Wnts functioning in cell polarity have been demonstrated in only a few cells. We analyzed how Wnts control cell polarity, using compound Wnt mutants, including animals with mutations in all five Wnt genes. We found that somatic gonadal precursor cells (SGPs) are properly polarized and oriented in quintuple Wnt mutants, suggesting Wnts are dispensable for the SGPs' polarity, which instead requires signals from the germ cells. Thus, signals from the germ cells organize the C. elegans somatic gonad. In contrast, in compound but not single Wnt mutants, most of the six seam cells, V1-V6 (which are epithelial stem cells), retain their polarization, but their polar orientation becomes random, indicating that it is redundantly regulated by multiple Wnt genes. In contrast, in animals in which the functions of three Wnt receptors (LIN-17, MOM-5, and CAM-1) are disrupted--the stem cells are not polarized and divide symmetrically--suggesting that the Wnt receptors are essential for generating polarity and that they function even in the absence of Wnts. All the seam cells except V5 were polarized properly by a single Wnt gene expressed at the cell's anterior or posterior. The ectopic expression of posteriorly expressed Wnts in an anterior region and vice versa rescued polarity defects in compound Wnt mutants, raising two possibilities: one, Wnts permissively control the orientation of polarity; or two, Wnt functions are instructive, but which orientation they specify is determined by the cells that express them. Our results provide a paradigm for understanding how cell polarity is coordinated by extrinsic signals.
Asunto(s)
Caenorhabditis elegans/citología , Polaridad Celular/genética , Células Epiteliales/fisiología , Células Madre/fisiología , Proteínas Wnt/metabolismo , Animales , Tipificación del Cuerpo/genética , Caenorhabditis elegans/genética , Caenorhabditis elegans/crecimiento & desarrollo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Polaridad Celular/fisiología , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Células Epiteliales/citología , Regulación del Desarrollo de la Expresión Génica , Células Germinativas/fisiología , Glicoproteínas/genética , Glicoproteínas/metabolismo , Gónadas/citología , Gónadas/metabolismo , Proteínas del Grupo de Alta Movilidad/genética , Proteínas del Grupo de Alta Movilidad/metabolismo , Morfogénesis , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Receptores Wnt/genética , Receptores Wnt/metabolismo , Células Madre/citología , Proteínas Wnt/genética , Vía de Señalización Wnt/genéticaRESUMEN
The maintenance of cell fate is important for normal development and tissue homeostasis. Epigenetic mechanisms, including histone modifications, are likely to play crucial roles in cell-fate maintenance. However, in contrast to the established functions of histone methylation, which are mediated by the polycomb proteins, the roles of histone acetylation in cell-fate maintenance are poorly understood. Here, we show that the C. elegans acetylated-histone-binding protein BET-1 is required for the establishment and maintenance of stable fate in various lineages. In most bet-1 mutants, cells adopted the correct fate initially, but at later stages they often transformed into a different cell type. By expressing BET-1 at various times in development and examining the rescue of the Bet-1 phenotype, we showed that BET-1 functions both at the time of fate acquisition, to establish a stable fate, and at later stages, to maintain the established fate. Furthermore, the disruption of the MYST HATs perturbed the subnuclear localization of BET-1 and caused bet-1-like phenotypes, suggesting that BET-1 is recruited to its targets through acetylated histones. Our results therefore indicate that histone acetylation plays a crucial role in cell-fate maintenance.
Asunto(s)
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/fisiología , Histona Acetiltransferasas/metabolismo , Proteínas Nucleares/metabolismo , Acetilación , Animales , Biomarcadores/metabolismo , Caenorhabditis elegans/citología , Proteínas de Caenorhabditis elegans/genética , División Celular , Linaje de la Célula , Cromosomas/metabolismo , Epigénesis Genética , Histona Acetiltransferasas/genética , Histonas/metabolismo , Mosaicismo , Proteínas Nucleares/genética , Fenotipo , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismoRESUMEN
PURPOSE: We performed genetic association studies using a native Japanese population to examine the reproducibility of results of lysyl oxidase-like 1 (LOXL1) genetic association studies for exfoliation glaucoma (XFG) beyond the differences of ethnicity. We also quantified LOXL1 mRNA expression in the human lens capsule to examine the possible correlation between LOXL1 expression and XFG pathogenesis. METHODS: We performed a case-control study using 95 Japanese XFG patients and 190 controls. Real-time polymerase chain reaction (PCR) analysis was performed using lens capsules obtained during surgery. RESULTS: The TT genotype in the single nucleotide polymorphism (SNP) rs1048661 and the GG genotype in the SNP rs3825942 in exon 1 of LOXL1 were significantly associated with an increased risk of XFG under recessive models (chi(2) test, p=5.34 x 10(-34) and p=2.1 x 10(-8), respectively). Quantification of LOXL1 mRNA expression demonstrated no significant difference between XFG and senile cataract samples. CONCLUSIONS: Although the functional effects of the LOXL1 SNP appear to be qualitative rather than quantitative, the amino acid substitution (R141L) caused by SNP rs1048661 is not a simple decisive factor for XFG due to the inverted allele frequency between Japanese XFG and Caucasian XFG patients. Further genetic and functional studies are essential for clarifying XFG pathogenesis.
Asunto(s)
Aminoácido Oxidorreductasas/genética , Pueblo Asiatico/genética , Síndrome de Exfoliación/complicaciones , Síndrome de Exfoliación/genética , Predisposición Genética a la Enfermedad , Glaucoma/genética , Polimorfismo de Nucleótido Simple/genética , Anciano , Anciano de 80 o más Años , Estudios de Casos y Controles , Regulación de la Expresión Génica , Glaucoma/complicaciones , Haplotipos , Humanos , Cápsula del Cristalino/metabolismo , Persona de Mediana Edad , ARN Mensajero/genética , ARN Mensajero/metabolismoRESUMEN
Coordination between cell proliferation and differentiation is important in normal development and oncogenesis. These processes usually have an antagonistic relationship, in that differentiation is blocked in proliferative cells, and terminally differentiated cells do not divide. In some instances, cyclins, cyclin-dependent kinases (CDKs) and their inhibitors (CKIs) play important roles in this antagonistic regulation. However, it is unknown whether CKIs and cyclin/CDKs regulate the uncommitted state in quiescent cells where CDK activities are likely to be low. Here, we show in C. elegans that cye-1/cyclin E and cdk-2/CDK2 repress terminal differentiation in quiescent cells. In cye-1 mutants and cdk-2(RNAi) animals, after asymmetric division, certain quiescent cells adopted their sister cells' phenotype and differentiated at some frequency. In contrast, in cki-1(RNAi) animals, these cells underwent extra divisions, while, in cki-1(RNAi); cdk-2(RNAi) or cki-1(RNAi); cye-1 animals, they remained quiescent or differentiated. Therefore, in wild-type animals, CKI-1/CKI in these cells maintained quiescence by inhibiting CYE-1/CDK-2, while sufficient CYE-1/CDK-2 remained to repress the terminal differentiation. The difference between sister cells is regulated by the Wnt/MAP kinase pathway, which causes asymmetric expression of CYE-1 and CKI-1. Our results suggest that the balance between the levels of CKI and cyclin E determines three distinct cell states: terminally differentiated, quiescent and uncommitted, and proliferating.
Asunto(s)
Caenorhabditis elegans/citología , Diferenciación Celular/fisiología , División Celular , Ciclina E/fisiología , Quinasa 2 Dependiente de la Ciclina/fisiología , Animales , Secuencia de Bases , Caenorhabditis elegans/enzimología , Caenorhabditis elegans/genética , Ciclina E/genética , Cartilla de ADN , Sistema de Señalización de MAP Quinasas , Mutación , Interferencia de ARNRESUMEN
Wnt signaling plays important roles in cell polarization in diverse organisms, and loss of cell polarity is an early event in tumorigenesis caused by mutations in Wnt pathway genes. Despite this, the precise roles of Wnt proteins in cell polarization have remained elusive. In no organism has it been shown that the asymmetric position of a Wnt signal is essential to establishing a cell's polarity. Attempts to test this by ubiquitous expression of Wnt genes have suggested that Wnt signals might act only as permissive factors in cell polarization. Here we find, by using cell manipulations and ectopic gene expression in C. elegans, that the position from which Wnt signals are presented can determine the polarity of both embryonic and postembryonic cells. Furthermore, the position from which a Wnt signal is presented can determine the polarity of Frizzled receptor localization, suggesting that the polarizing effect of Wnt is likely to be direct. These results demonstrate that Wnt proteins can function as positional cues in establishing cell polarity.
Asunto(s)
Caenorhabditis elegans , Polaridad Celular , Transducción de Señal/fisiología , Proteínas Wnt/metabolismo , Animales , Caenorhabditis elegans/anatomía & histología , Caenorhabditis elegans/embriología , Caenorhabditis elegans/crecimiento & desarrollo , Caenorhabditis elegans/fisiología , Linaje de la Célula , Receptores Frizzled/genética , Receptores Frizzled/metabolismo , Morfogénesis , Huso Acromático/metabolismo , Proteínas Wnt/genéticaRESUMEN
beta-Catenin can promote adhesion at the cell cortex and mediate Wnt signaling in the nucleus. We show that, in Caenorhabditis elegans, both WRM-1/beta-catenin and LIT-1 kinase localize to the anterior cell cortex during asymmetric cell division but to the nucleus of the posterior daughter afterward. Both the cortical and nuclear localizations are regulated by Wnts and are apparently coupled. We also found that the daughters show different nuclear export rates for LIT-1. Our results indicate that Wnt signals release cortical WRM-1 from the posterior cortex to generate cortical asymmetry that may control WRM-1 asymmetric nuclear localization by regulating cell polarity.
Asunto(s)
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/metabolismo , Núcleo Celular/metabolismo , Proteínas del Citoesqueleto/metabolismo , Transactivadores/metabolismo , Animales , Caenorhabditis elegans/citología , División Celular , Polaridad Celular , beta CateninaRESUMEN
Chronic inflammation contributes to the pathogenesis of several complications of hemodialysis therapy. It is thought that backfiltration of bacteria-derived contaminations during dialysis may induce a chronic inflammatory state. High-sensitivity C-reactive protein (hs-CRP) is one of the tools which can take a hold on such a chronic inflammatory condition. We examined the effect of ultrapure dialysate which contributes to chronic inflammation with hs-CRP and tried to reduce endotoxin (ET) levels at the end of the dialysate from 70 EU/l to <1.0 EU/l (ultrapure dialysate). Other dialysis conditions, except ET level, were fixed. We investigated the hs-CRP of 23 patients receiving regular dialysis before the use of ultrapure dialysate and 1 year after use of it prospectively. The data showed a significant decrease in the median value of the hs-CRP from 0.16 to 0.07 mg/dl (p < 0.05). The value of serum beta(2)-microglobulin decreased from 33.2 to 28.4 mg/dl (p < 0.01) and the hemoglobin level increased from 10.0 to 11.0 g/dl (p < 0.05). These results indicate that even a dialysate containing 70 EU/l of ET level may induce a chronic inflammatory state. hs-CRP is a very useful marker of chronic inflammation and the use of ultrapure dialysate is necessary to improve a chronic inflammatory state. The targeted ET level at the end of the dialysate should be set at < or = 1.0 EU/l.