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At least 595 records · Page 33Linked to original sources
PubMed2001

VHL induces renal cell differentiation and growth arrest through integration of cell-cell and cell-extracellular matrix signaling.

Mutations in the von Hippel-Lindau (VHL) gene are involved in the family cancer syndrome for which it is named and the development of sporadic renal cell cancer (RCC). Reintroduction of VHL into RCC cells lacking functional VHL [VHL(-)] can suppress their growth in nude mice, but not under standard tissue culture conditions. To examine the hypothesis that the tumor suppressor function of VHL requires signaling through contact with extracellular matrix (ECM), 786-O VHL(-) RCC cells and isogenic sublines stably expressing VHL gene products [VHL(+)] were grown on ECMs. Cell-cell and cell-ECM signalings were required to elicit VHL-dependent differences in growth and differentiation. VHL(+) cells differentiated into organized epithelial sheets, whereas VHL(-) cells were branched and disorganized. VHL(+) cells grown to high density on collagen I underwent growth arrest, whereas VHL(-) cells continued to proliferate. Integrin levels were up-regulated in VHL(-) cells, and cell adhesion was down-regulated in VHL(+) cells during growth at high cell density. Hepatocyte nuclear factor 1alpha, a transcription factor and global activator of proximal tubule-specific genes in the nephron, was markedly up-regulated in VHL(+) cells grown at high cell density. These data indicate that VHL can induce renal cell differentiation and mediate growth arrest through integration of cell-cell and cell-ECM signals.

Animals↗
PubMed2006

Mutations in the RETICULATA gene dramatically alter internal architecture but have little effect on overall organ shape in Arabidopsis leaves.

A number of mutants have been described in Arabidopsis, whose leaf vascular network can be clearly distinguished as a green reticulation on a paler lamina. One of these reticulate mutants was named reticulata (re) by Rédei in 1964 and has been used for years as a classical genetic marker for linkage analysis. Seven recessive alleles of the RE gene were studied, at least four of which seem to be null. Contrary to many other leaf mutants studied in Arabidopsis, very little pleiotropy was observed in the external morphology of the re mutants, whose only aberration obvious at first sight is the reticulation exhibited by cotyledons and leaves. The re alleles caused a marked reduction in the density of mesophyll cells in interveinal regions of the leaf, which does not result from perturbed plastid development in specific cells, but rather from a dramatic change in internal leaf architecture. Loss of function of the RE gene seems to specifically perturb mesophyll cell division in the early stages of leaf organogenesis. The leaves of re mutants were nearly normal in shape in spite of their extremely reduced mesophyll cell density, suggesting that the epidermis plays a major role in regulating leaf shape in Arabidopsis. The RE gene was positionally cloned and found to be expressed in all the major organs studied. RE encodes a protein of unknown function and is identical to the LCD1 gene, which was identified based on the increased sensitivity to ozone caused by its mutant allele lcd1-1. Double mutant analyses suggest that RE acts in a developmental pathway that involves CUE1 but does not include DOV1.

Arabidopsis↗
PubMed2001

Cytological characterization of apatitic calcium phosphate structures in bronchial epithelial tissue cultured from a child with cystic fibrosis (deltaF508).

Patients with cystic fibrosis homozygous for the AF508 mutation have marked disturbances in ion exchanges in a variety of tissues. Alterations in intra- or extracellular levels of Ca2+ and calcifications have been observed in numerous tissues from such patients, although the nature and origin of such calcifications have yet to be elucidated. In this study, we investigated the formation of calcifications in the respiratory tract of a AF508 homozygous child and attempted to establish their origin. Samples of bronchial epithelium from this patient were subjected to cytophysiological analysis ex vivo and in vitro. The defect of targeting of the cystic fibrosis transmembrane conductance regulator (CFTR) to the apical plasma membrane of epithelial cells was verified. Cytochemical and ultrastructural analysis revealed the presence of crystalline aggregates in fine needles in the respiratory tract. Cytochemical analysis, X-ray spectrometry, and electron diffraction showed that these aggregates corresponded to crystals of calcium phosphate in an apatite-like structure. Ultrastructural study of primary cultures of bronchial epithelium showed the presence of calcium phosphate crystals in granules from Golgi apparatus and in mitochondria. These observations indicated that modifications of ionic exchanges due to a defect in targeting of CFTR AF508 to the apical plasma membrane led to the formation of crystals of calcium phosphate in the cytoplasm of pulmonary cells. These crystals could enhance inflammation of the lung in patients with cystic fibrosis.

Apatites↗
PubMed1986

Effects of asbestos fibers on cell division, cell survival, and formation of thioguanine-resistant mutants in Chinese hamster ovary cells.

The ability of crocidolite fibers to induce point mutations and mitotic abnormalities in Chinese hamster ovary (CHO) cells was examined in cell cultures. The purpose has been to study the possibilities for establishing in vitro test methods to quantify genetic damage induced by asbestos and other mineral fibers. Results obtained with the CHO/hypoxanthine guanine phosphoribosyl transferase system indicated that crocidolite fibers per se do not significantly increase the number of thioguanine-resistant mutants. Crocidolite fibers also failed to potentiate the mutagenicity of benzo[a]pyrene. Time-lapse cinematography and microscopy showed that asbestos (crocidolite) fibers were markedly cytotoxic. Among surviving cells some underwent abnormal cell divisions which resulted in multi- and micronucleate cells. Many cells that contained a few asbestos fibers, however, underwent mitosis and successfully formed two mononucleate daughter cells capable of further divisions. Individual, fiber-containing cells were examined by time-lapse television recordings for 4-5 days. During this time period some cells underwent six divisions and generated an almost normal number of daughter cells. Cells which contained fibers that were longer or equivalent to the diameter of the mitotic cell (20 microns), showed different forms of mitotic abnormalities. The frequency of multinucleate cells was drastically increased following exposure to asbestos fibers. Only rarely, however, did these cells divide to produce viable daughter cells capable of continued cell multiplication. The frequency of multinucleate cells was dependent on the dose of exposure to asbestos fibers and could possibly be used as an index of the degree of mitotic disturbances induced by mineral fibers.

Animals↗
PubMed1993

Effect of lateral suppressor on petal initiation in tomato.

Flowers developing on tomato (Lycopersicon esculentum) plants homozygous for the lateral suppressor (ls) mutation lack petals. Scanning electron micrographs revealed that in ls plants no second whorl organs were initiated. The initiation of first, third, and fourth whorl organs were unaffected by this mutation. To investigate interactions between the cells in different layers of the floral meristem during organ initiation, a periclinal chimera between wild-type and ls tomato was generated. Flowers of the chimera having ls cells in the outer meristem layer (L1) and wild-type cells in internal layers (L2 and L3) developed normally, including the initiation of organ primordia that differentiated as petals in normal positions within the second whorl. L1 of the chimera developed in a non-autonomous manner during petal development. Thus, wild-type cells occupying the internal meristem layers provided developmental cues necessary for initiation of petal primordia at appropriate positions on the floral meristem. L1 cells carrying the lateral suppressor mutation were fully capable of responding to this information and differentiated appropriately.

Chimera↗
PubMed1997

Development of a lethal congenital heart defect in the splotch (Pax3) mutant mouse.

OBJECTIVE: The splotch (Sp2h) mutation disrupts the Pax3 gene and is lethal in homozygotes. The aim of the present study was to investigate the cause of lethality. METHODS AND RESULTS: Using the splotch (Sp2H) mouse mutant, we demonstrated that approximately 60% of Sp2H homozygotes die in utero at 13.5-14.5 days of gestation. All these embryos have cardiac malformations involving partial or complete failure of septation of the outflow tract. Although the cause of death in utero is unknown, the dying embryos are edematous, their superior caval veins are over-expanded, and the fetal liver is enlarged and engorged with blood, all signs of cardiac failure. The remaining Sp2H homozygotes die around the time of birth, and these embryos have grossly normal hearts. All Sp2H homozygotes have neural tube defects, either spina bifida, exencephaly, or both. Although these defects clearly do not cause death in utero, they are very likely responsible for the perinatal death of homozygotes that survive to late gestation. There is no correlation between the presence or absence of a cardiac defect and the type of neural tube defect. On the other hand, there is a striking correlation between presence of a cardiac defect and reduction or absence of dorsal root ganglia, which are derivatives of the neural crest. CONCLUSIONS: In this paper, we show that the lethality has a biphasic pattern, and the data strongly suggests that mid-gestation lethality is due to cardiac defects and not the associated neural tube defects. This finding supports the idea that 'conotruncal' cardiac defects involving the ventricular outflow tracts develop as a result of failure of the 'cardiac' neural crest to colonise the developing heart in the mid-gestation embryo, and that the resulting heart defects are solely responsible for the observed mortality.

Animals↗
PubMed1999

Potential of denaturing gradient gel electrophoresis for scanning of beta-thalassemia mutations in India.

Over the last few years, substantial progress has been made in developing strategies for the detection and characterization of various mutations causing beta-thalassemia. The Indian population comprises of numerous endogamous caste groups and beta-thalassemia is seen in almost all of them. Knowledge of the spectrum of beta-thalassemia mutations in the population is a prerequisite for successful implementation of a prevention programme. Among the different approaches available today, Denaturing Gradient Gel Electrophoresis (DGGE) offers a valid technical approach which is applicable for screening of known mutants and polymorphisms as well as in locating regions of DNA bearing unknown mutations. We analysed 356 unrelated beta-thalassemia heterozygotes by DGGE and detected 30 anomalous DGGE patterns. Fifteen mutations were characterized after sequencing 25 anomalous patterns. Of these, codon 10(GCC --> GCA) is a recently reported novel beta-thalassemia mutation while -28(A --> G) and codon 121(G --> T) are being reported for the first time in the Indian population. HbS and HbE also showed two anomalous DGGE patterns each. Framework (FW) linkage studies showed that four mutations were associated with different beta-globin gene frameworks. Linkage of IVSI-5(G --> C) and cap site +1(A --> C) to FW2 and 619-bp deletion to FW1 is being observed for the first time. Multiple DGGE patterns corresponding to the same mutation is one of the major drawbacks of this technique. In spite of this, if sufficient preliminary work has been carried out to compile a comprehensive catalogue of DGGE patterns; this is a powerful approach to characterize the mutation or to localize a small region of DNA in the case of rarer mutations.

Base Sequence↗
PubMed1996

Role of the ninaC proteins in photoreceptor cell structure: ultrastructure of ninaC deletion mutants and binding to actin filaments.

The ninaC proteins are found in Drosophila photoreceptor cells. Their primary sequences suggest they are kinase/myosin chimeras, but their myosin head-like domain is the most divergent amongst all the myosin-like proteins described to date. To investigate possible roles of the ninaC proteins in cell structure, we examined the ultrastructure of the photoreceptor cells in various ninaC mutants, and tested the ability of the proteins to interact with actin filaments in a myosin-like manner. In flies lacking the larger ninaC protein, p174, an ultrastructural phenotype was evident before eclosion. The axial actin cytoskeleton of the rhabdomeral microvilli appeared either fragmented or as an isolated structure, without linkage to the microvillar membrane. Deletion of the myosin head-like domain or the calmodulin-binding domain of p174 resulted in a similar abnormal cytoskeleton. Breakdown of the rhabdomeres followed, although at different rates depending on the deletion. Lack of the smaller protein, p132, per se did not result in photoreceptor degeneration, but in older flies there was an abnormal accumulation of multivesicular bodies. Moreover, the presence of p132 retarded the degeneration that occurs in the absence of p174, even though the p132 remained outside the rhabdomere. Biochemical studies showed that both ninaC proteins bind actin filaments and cosediment with actin filaments in an ATP-sensitive manner. These results outline structural roles for the ninaC proteins, and are consistent with the notion, suggested by their amino acid sequences, that the proteins are actin-based mechanoenzymes.

Actins↗
PubMed1999

Genetic analysis of the role of the drosophila fat facets gene in the ubiquitin pathway.

The Drosophila fat facets gene encodes a deubiquitinating enzyme required during eye development to limit the number of photoreceptors in each facet to eight. Ubiquitin is a small polypeptide that targets proteins for degradation by the proteasome. Deubiquitinating enzymes cleave ubiquitin-protein bonds. In order to investigate the role of FAT FACETS in the ubiquitin pathway, genetic interactions between fat facets and the Drosophila UbcD1 gene were assessed. In addition, three yeast deubiquitinating enzyme genes were tested for their ability to substitute for fat facets in the developing Drosophila eye and for their effects on eye morphology. The results of these experiments support the hypothesis that FAT FACETS activity antagonizes that of the proteolytic machinery. The implications of these results for the specificity of FAF and yeast UBPs are discussed as well.

Animals↗
PubMed1991

Extracellular matrix of the developing heart in normal and cardiac lethal mutant axolotls, Ambystoma mexicanum.

As part of an ongoing study of heart development in normal and cardiac lethal mutant axolotls (Mexican salamanders) we examined the extracellular matrix (ECM) by microscopical methods. With scanning electron microscopy we are unable to detect ECM on the apical surface of cells of the early cardiogenic mesoderm. During the period of lateral plate migration, which coincides with the period of cardiogenic induction of mesoderm by anterior endoderm, there is little ECM, aside from some microfibrils, on the basal surface of the endoderm or mesoderm of the pharyngeal region. Later, a basal lamina (BL) is found on the endoderm and along portions of the developing endocardial and myocardial tubes. By the time of heartbeat initiation the BLs are complete and invested with striated collagen-like fibrils that are sparsely distributed in the "cardiac jelly" of normal and mutant hearts. Striated fibril deposition, which increases with time, is generally random in orientation, with the exception of some regions where there is a preferred directionality. During the post-hatching period striated fibrils appear in the subepicardial space. In addition, branching fibers that are probably elastin appear in the bulbus arteriosus. In these later stages the density of fibrils in the cardiac lethal mutant heart is much less than normal. Indirect immunofluorescent microscopy reveals laminin and fibronectin in the basal laminae of the endocardial and myocardial tubes of both normal and cardiac lethal mutant hearts. In addition, punctate and fibrillar staining for fibronectin, and punctate staining for laminin are found in the cardiac jelly. These matrix proteins are not abundant at the apical (exterior) surface of the myocardium until the epicardium appears.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambystoma mexicanum↗
PubMed1981

Sensory control of dauer larva formation in Caenorhabditis elegans.

As a sensory response to starvation or overcrowding, Caenorhabditis elegans second-stage larvae may molt into a developmentally arrested state called the dauer larva. When environmental conditions become favorable for growth, dauer larvae mold and resume development. Some mutants unable to form dauer larvae are simultaneously affected in a number of sensory functions, including chemotaxis and mating. The behavior and sensory neuroanatomy of three such mutants, representing three distinct genetic loci, have been determined and compared with wild-type strain. Morphological abnormalities in afferent nerve endings were detected in each mutant. Both amphid and outer labial sensilla are affected in the mutant CB1377 (daf-6)X, while another mutant, CB1387 (daf-10)IV, is abnormal in amphidial cells and in the tips of the cephalic neurons. The most pleitropic mutant, CB1379 (che-3)I, exhibits gross abnormalities in the tips of virtually all anterior and posterior sensory neurons. The primary structural defect in CB1377 appears to be in the nonneuronal amphidial sheath cells. The disruption of neural organization in CB1377 is much greater in the adult than in the L2 stage. Of all the anterior sense organs examined, only the amphids are morphologically affected in all three mutants. Thus, one or more of the amphidial neurons may mediate the sensory signals for entry into the dauer larva stage in normal animals. Using temperature-sensitive mutants we determined that the same defects which block entry into the dauer stage also prevent recovery of dauer larvae.

Animals↗
PubMed2002

Expression of Peg1 (Mest) in the developing mouse heart: involvement in trabeculation.

Peg1 (Mest) is an imprinted gene of unknown function widely expressed in the mouse embryo, predominantly in cells of the mesodermal lineage. We have revealed a restricted expression pattern within the developing heart. Initial uniform expression throughout the linear heart tube subsequently becomes restricted, primarily to the developing myocardial trabeculae of both the atria and ventricles, where it persists into late development. Expression in the atrial appendage myocardium precedes the emergence of trabeculae (pectinate muscles), and occurs earlier and to a greater extent on the right than on the left, reflecting the spatial and temporal pattern of trabeculation. Analysis of myocardial morphology in mice lacking the Peg1 gene, which are viable and appear grossly normal, reveals a subtle alteration in the pattern of trabeculation: an increase in thickness and reduction in density of the compact myocardium, similar to that seen in the human cardiomyopathy ventricular noncompaction.

Alleles↗
PubMed2004

Senseless is required for pupal retinal development in Drosophila.

Drosophila sensory organs are specified by a family of proneural genes which induce the expression of several common targets. One such target is senseless, which encodes a zinc finger transcription factor. We analyzed the function of senseless during pupal retinal development and found that senseless is required for recruitment of both cone and pigment cells, the pupal-derived ommatidial support cells. We also found that Senseless is expressed in neural precursors shortly after the larval-pupal transition and is both necessary and sufficient for interommatidial bristle development. Furthermore, senseless is the primary target of achaete and scute during interommatidial bristle development. We also identified several differences between the development of interommatidial bristles and other macrochaete. In particular, EGFR signaling is not required for interommatidial bristle development, nor is positive feedback regulation of proneural genes by senseless. A model for interommatidial bristle specification is presented.

Animals↗
PubMed1992

Cell lineage-specific expression of modulo, a dose-dependent modifier of variegation in Drosophila.

Variegation in Drosophila is a manifest illustration of the important role played by chromatin structure in gene expression. We have isolated mutants of modulo (mod) and shown that this gene is a dominant suppressor of variegation. Null mutants are recessive lethal with a melanotic tumour phenotype. The mod protein directly binds DNA, which indicates that it may serve to anchor multimeric complexes promoting chromatin compaction and silencing. Using a specific monoclonal antibody we examined by immunocytochemistry the accumulation pattern of mod protein during embryogenesis. The protein is first detected before the blastoderm cellularization in all somatic nuclei, precisely when pericentromeric heterochromatin becomes visible. After the first cell division, mod protein is expressed in lineages of specific embryonic primordia. Based on its dominant phenotype, expression pattern and DNA-binding activity of its product, we propose that mod regulates chromatin structure and activity in specific cell lineages.

Animals↗
PubMed1993

asense, a member of the Drosophila achaete-scute complex, is a proneural and neural differentiation gene.

The asense (ase) gene of the achaete-scute complex (AS-C) is expressed in the precursors of all adult sensory organs (SOs), the sensory mother cells (SMCs) and in their immediate progeny. Its deletion causes the loss of some SOs and the abnormal differentiation of part of the remaining ones. These defects, which include malformations of the external part of the SOs, duplication of the innervating neuron etc, are enhanced by the haploid condition for the other AS-C genes and are corrected by an ase transgene. We conclude that ase participates, in combination with other members of the AS-C, in implementing the neural program of differentiation of the SMCs. ase also has a proneural function that participates in the singling out of the SMCs that give rise to the recurved bristles of the anterior wing margin. The proneural potential of ase is shown, in addition, by the generation of SOs induced by the generalized expression of an ase gene driven by a hsp70 promoter.

Animals↗
PubMed1976

The correlation of plasma membrane microvilli and intracellular cyclic AMP content in a rat epitheloid kidney cell line.

Modulation of the intracellular concentration of cyclic AMP has been associated with a regulatory role in cell division, cell morphology, and physical properties of the plasma membrane. Untransformed rat kidney cells in culture exhibit epitheloid morphology, high intracellular cyclic AMP levels, and contact inhibition of growth. Untransformed rat kidney cells transformed with the Kirsten murine sarcoma virus exhibit a low cyclic AMP content, rapid growth rate, and a loss of contact inhibition. Scanning electron microscopy reveals a distinctive difference in the surface structure of the two cell types during Gl of the cell cycle. The surface of the transformed cell is covered with microvilli while its untransformed counterpart is devoid of microvilli. The presence of microvilli can be controlled as a function of temperature by two temperature-sensitive mutants of the Kirsten sarcoma virus (ts6t6 and ts371 cl 5). In the ts6t6 mutant, growth at 32 degrees C results in a low cyclic AMP content and the presence of microville, while growth at 39 degrees C results in a high cyclic AMP content and a decrease in microvilli. The opposite effect is seen with the ts371 cl 5 mutant. Correlation of cyclic AMP content with the presence of microvilli suggests that this surface phenomenon is a function of cyclic AMP concentration.

Cell Division↗
PubMed2004

Geminin predicts adverse clinical outcome in breast cancer by reflecting cell-cycle progression.

Geminin inhibits DNA replication by preventing Cdt1 from loading minichromosome maintenance (MCM) proteins onto DNA. The present study has investigated whether the frequency of geminin expression predicts clinical outcome in breast cancer. Immunohistochemistry was used first to examine geminin expression in normal and malignant breast tissue (n = 67). Correlations with cell-cycle parameters, pathological features, and clinical outcome were then determined using an invasive breast carcinoma tissue microarray (n = 165). Breast carcinomas were scanned for mutations (n = 61) and copy number imbalances (n = 241) of the geminin gene. Finally, the cell cycle distribution of geminin in breast cancer cells was investigated in vivo and in vitro. Despite a putative tumour suppressor function, it was found that increased geminin expression is a powerful independent indicator of adverse prognosis in invasive breast cancer. Both poor overall survival (p = 0.0002) and the development of distant metastases (p = 0.005) are predicted by high geminin expression, which performs better in this patient cohort than traditional factors currently used to determine prognosis and appropriate therapy. No mutations or deletions of the geminin gene and no evidence that a high frequency of protein expression is related to gene amplification were found. It is shown that geminin is expressed from S to M phase in breast carcinoma tissue and cell lines, disappearing at the metaphase--anaphase transition. While MCM proteins identify all non-quiescent cells, geminin identifies the sub-fraction that have entered S phase, but not exited mitosis, thereby indicating the rate of cell-cycle progression. It is suggested that this explains its unexpected value as a prognostic marker in breast cancer.

Adult↗
PubMed1975

Surface defects in ventricular cells of brains of mouse embryos homozygous for the Loop-tail gene: scanning electron microscopic study.

Luminal surfaces in the mesencephalon and rhombencephalon in normal mouse embryos and those homozygous for Lopp-tail were studied by means of scanning electron microscopy. Ventricular cells in the ventrolateral regions of normal day-10 and -11 brains showed single apical cilia and microvilli, whereas those in ventromedial regions showed a dense network of microvilli and bulbous projections which tended to obscure the apical cilia and cellular outlines. Similar regional differences occurred in the Loop-tail brains, although there was a marked decrease in the number and density of microvilli and bulbous projections. At days 12-14 of gestation the latter brains also showed a flattening of cell surfaces, shallow depressions, and craterlike ruptures in the plasma membranes.

Animals↗