Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “morphogenesis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54Linked to original sources
PubMed2006

Tissue geometry determines sites of mammary branching morphogenesis in organotypic cultures.

The treelike structures of many organs, including the mammary gland, are generated by branching morphogenesis, a reiterative process of branch initiation and invasion from a preexisting epithelium. Using a micropatterning approach to control the initial three-dimensional structure of mouse mammary epithelial tubules in culture, combined with an algorithm to quantify the extent of branching, we found that the geometry of tubules dictates the position of branches. We predicted numerically and confirm experimentally that branches initiate at sites with a local minimum in the concentration of autocrine inhibitory morphogens, such as transforming growth factor-beta. These results reveal that tissue geometry can control organ morphogenesis by defining the local cellular microenvironment, a finding that has relevance to control of invasion and metastasis.

Algorithms↗
PubMed1967

Embryonic morphogenesis: role of fibrous lattice in the development of feathers and feather patterns.

In the morphogenesis of embryonic feather germs the formation of dermal cell groupings is associated with the development of a highly regular pattern of birefringence in the dermis. This birefringence is due to a lattice-like system of collagenous tracts along which dermal cells become progressively aligned and grouped in regularly spaced sites. The experimental results suggest that this fibrous lattice is of major significance in the morphogenesis of feather germs and in their characteristic pattern of distribution.

Animals↗
PubMed1997

Control of mouse cardiac morphogenesis and myogenesis by transcription factor MEF2C.

Members of the myocyte enhancer factor-2 (MEF2) family of MADS (MCM1, agamous, deficiens, serum response factor)-box transcription factors bind an A-T-rich DNA sequence associated with muscle-specific genes. The murine MEF2C gene is expressed in heart precursor cells before formation of the linear heart tube. In mice homozygous for a null mutation of MEF2C, the heart tube did not undergo looping morphogenesis, the future right ventricle did not form, and a subset of cardiac muscle genes was not expressed. The absence of the right ventricular region of the mutant heart correlated with down-regulation of the dHAND gene, which encodes a basic helix-loop-helix transcription factor required for cardiac morphogenesis. Thus, MEF2C is an essential regulator of cardiac myogenesis and right ventricular development.

Acyltransferases↗
PubMed1994

Global form and singularity: modeling the blind spot's role in lateral geniculate morphogenesis.

Optic nerve terminals segregate by functional class into distinct layers in the lateral geniculate nucleus, the thalamic relay nucleus of the visual system. In the rhesus monkey, the number of geniculate layers changes abruptly from six posteriorly (central vision) to four anteriorly (peripheral vision). The plane of transition between these patterns passes through small laminar gaps corresponding to the perceptual blind spot caused by the exit of the optic nerve from the eyeball. However, this plane of transition has no apparent functional link to the blind spot. A thermodynamic model of geniculate morphogenesis supports the hypothesis that the blind spot traps the transition in its stereotypic position by introducing a singularity in an otherwise smooth gradient in forces guiding the development of geniculate morphogenesis. This relation suggests that small-scale anomalies may be important in the determination of large-scale patterns in biological structure.

Animals↗
PubMed1992

Self-similar colony morphogenesis by gram-negative rods as the experimental model of fractal growth by a cell population.

The ability to form a fractal colony was shown to be common among several species of the family Enterobacteriaceae. Bacterial spreading growth in a two-dimensional field of nutrient concentration was indicated to be important for this experimental self-similar morphogenesis. As a basic analogy, the diffusion-limited aggregation model was suggested. Fractal dimensions of colonies were mostly in the range of values from 1.7 to 1.8, similar to those of the two-dimensional diffusion-limited aggregation model. Bacterial characteristics and culture conditions inducing changes in fractal patterns and growth rates were identified. The contribution of the bacterial multicellular nature to fractal morphogenesis is discussed.

Glucose↗
PubMed2006

Expression of the Candida albicans morphogenesis regulator gene CZF1 and its regulation by Efg1p and Czf1p.

The ability of Candida albicans to transit between different cellular morphologies is believed to be important for virulence. Morphological transitions occur in response to a variety of environmental signals. One such signal is encountered when cells are grown in a semisolid matrix. An important regulator of cellular morphology is the putative transcription factor CZF1. Here we demonstrate that transcription of CZF1 is responsive to growth parameters such as the temperature, carbon source, growth phase of cells, and the physical environment. In wild-type cells, a CZF1 transcript of about 4 kb was expressed when cells were grown embedded in semisolid agar medium, as well as in late exponential phase when cells were grown in liquid medium. Deletion of EFG1, a key regulator of morphogenesis, abolished CZF1 expression. Overexpression of CZF1 revealed that this gene also autoregulates its expression. Efg1p and Czf1p were shown by chromatin immunoprecipitation to act by binding to the promoter of CZF1. The coupling of environmental cues to the expression of a morphogenetic transcription factor may allow C. albicans to coordinate morphogenesis in response to specific conditions encountered in the human host.

5' Untranslated Regions↗
PubMed2006

A new GntR family transcriptional regulator in streptomyces coelicolor is required for morphogenesis and antibiotic production and controls transcription of an ABC transporter in response to carbon source.

We recently reported the isolation and initial characterization of a transposon-generated mutation that resulted in defects in both morphogenesis and antibiotic production in Streptomyces coelicolor. The insertion identified the SCO7168 open reading frame whose predicted product is a GntR family transcriptional regulator. Here, we show that this gene acts to repress transcription of itself as well as a series of genes immediately adjacent to it on the S. coelicolor chromosome that likely encode an ATP-binding cassette (ABC)-type transporter for carbohydrate uptake. Transcription of this transporter is strongly induced by growth on relatively poor carbon sources such as trehalose and melibiose and weakly induced by lactose and glycerol but not glucose, and induction is not repressed by the presence of glucose. Constructed deletions of the ABC transporter itself resulted in the suppression of the original transposon mutation, suggesting that inappropriate expression of the ABC transporter is responsible, at least in part, for the mutant phenotype. Because this transporter responds to the presence of alpha-glucosides and has similarity to two other carbohydrate transporters of this class, we have named the genes of the transporter agl3E, agl3F, and agl3G and the GntR-like protein that regulates transcription of the transporter agl3R in accordance with established nomenclature. We suggest that agl3R is one of a number of homologous proteins in Streptomyces (there are 57 putative GntR family regulators in the S. coelicolor genome) that respond to nutritional and/or environmental signals to control genes that affect morphogenesis and antibiotic production.

ATP-Binding Cassette Transporters↗
PubMed1973

Effects of ethylenediaminetetraacetate and chloramphenicol on mitochondrial activity and morphogenesis in Mucor rouxii.

The present study demonstrates the importance of mitochondrial activities in controlling Mucor rouxii morphogenesis. The respiratory capacity of the spores of this facultatively anaerobic, dimorphic fungus becomes repressed if germination and growth take place in the absence of oxygen. The level of activity of mitochondrial enzymes such as cytochrome oxidase and malate dehydrogenase is lower in the anaerobic yeastlike cells than it is in ungerminated spores and in aerobic hyphae, but the reverse is true for glycolytic enzymes such as pyruvate kinase and alcohol dehydrogenase. Following exposure to air, yeastlike cells convert into hyphae after a lag period corresponding to aerobic adaptation. Anaerobic cultures grown in the presence of ethylenediaminetetraacetate (EDTA) at a concentration of 10(-4) M exhibit hyphal morphology. These cells, which are fully adapted to anaerobic fermentation, nevertheless have potentially active mitochondria with the same levels of respiratory enzymes as ungerminated spores. These cells are able to grow immediately after aeration, without an adaptation lag. Evidence is presented which indicates that the morphogenetic effect of EDTA is not the result of elimination of free metals. Additional evidence proving mitochondrial control of morphogenesis in M. rouxii is that chloramphenicol (4 mg/ml) induced the formation of respiratory-deficient, yeastlike cells in aerobic cultures.

Aerobiosis↗
PubMed1977

Control of morphogenesis in Arthrobacter crystallopoiets: effect of cyclic adenosine 3',5'-monophosphate.

The intracellular levels of cyclic adenosine 3',5'-monophosphate (cyclic AMP) were measured at various intervals during growth and morphogenesis in Arthrobacter crystallopoietes. Cyclic AMP levels remained relatively constant throughout growth in spherical cells grown in glucose-based media. Immediately after inoculation of spheres from glucose- to succinate-containing media, a 30-fold increase in intracellular cyclic AMP was detected. This dramatic rise in cyclic AMP preceded the observed change in cellular morphology from spheres to rods. The cyclic AMP level in rod-shaped cells rapidly dropped to a relatively stable concentration during the exponential growth phase. At the onset of stationary phase and rod-to-sphere morphological transition, a second peak of cyclic AMP was observed. Neither of these two peaks was detectable in a morphogenetic mutant that grew only as spheres. The intracellular levels of cyclic AMP in this mutant remained constant throughout exponential growth and decreased slightly during stationary phase. Effects of exogenously added cyclic nucleotides and their derivatives to both parent and mutant cultures were investigated. The data presented indicate that dramatic changes in intracellular cyclic AMP levels occur just before the morphological transitions characteristic of the morphogenetic cycle in A. crystallopoietes. It is suggested that cyclic AMP is a contributing factor in the regulatory phenomenon associated with morphogenesis in this bacterium.

Arthrobacter↗
PubMed1977

Electron microscopic study of cell surface rings during cell division and morphogenesis of Arthrobacter crystallopoietes.

The whole cell ultrastructure during cell division and morphogenesis of Arthrobacter crystallopoietes was monitored using electron microscopic techniques. Glucose-grown spherical cells were inoculated into succinate-based medium. In this medium, the organism undergoes a morphogenetic cycle consisting of elongation of spheres to rods, exponential growth as rods, and fragmentation of rods to spherical cells. Raised bands or rings that encircled the cells were evident on the cell surface of both sphere- and rod-shaped cells. Many rod-shaped cells possessed two or more rings arranged adjacent to each other in a parallel orientation. At each cell division a new ring was formed on both siblings. However, as predicted by the proposed model of unidirectional cell growth and by maintaining a ring from the previous generation, unequal numbers of rings were observed on sibling cells. Only one ring was visible on most of the spherical inoculum cells, but in some cases a second ring perpendicular to the other ring was observed. Parallel rings were found on spherical cells resulting from fragmentation or reductive cell division of rods during the stationary growth phase. Thus, these spheres could be distinguished from inoculum spheres containing a single ring or perpendicular orientation of rings. The number of rings per cell and arrangement of rings on the cell surface of sibling cells after cell division, but before cell separation, are discussed with respect to cell age, cell division, and sphere-rod-sphere morphogenesis of A. crystallopoietes.

Arthrobacter↗
PubMed1979

Possible involvement of bacterial autolytic enzymes in flagellar morphogenesis.

Autolytic enzymes were found to be required for flagellar morphogenesis in Bacillus subtilis 168 and Bacillus licheniformis 6346. Two previously characterized, poorly lytic, chain-forming mutants of B. subtilis 168, strains FJ3 (temperature conditional) and FJ6, each 90 to 95% deficient in the production of N-acetylmuramyl-L-alanine amidase and endo-beta-N-acetylglucosaminidase, were observed to be nonmotile at 35 degrees C in a variety of liquid and semisolid meida. In contrast, cells of the isogenic wild-type strain were motile and fully separated. Electron microscopy revealed the complete absence of flagella on the mutant cells. Similar observations were made with another poorly lytic strain of B. subtilis 168 (Nil5) and with two poorly lytic, phosphoglucomutase-deficient mutants of B. licheniformis 6346 (MH-3, MH-5). In minimal media lacking galactose (restrictive conditions), the B. licheniformis mutants failed to form flagella, or had serious abnormalities in flagellar morphogenesis and motility. Under permissive conditions, mutants FJ3 (grown at 17 degrees C) and MH-5 (grown with addend galactose) showed increased autolytic activities, grew in the dechained form, and regained their capacities to synthesize functional flagella. Examination of several classes of spontaneous revertants derived from the various mutant strains further demonstrated a close relationship between autolysin acttivity and flagellation in the two Bacillus spp.

Acetylglucosaminidase↗
PubMed1980

Regulation of ornithine decarboxylase during morphogenesis of Mucor racemosus.

During the yeast-to-hyphae transition of the dimorphic phycomycete Mucor racemosus, there was a 30- to 50-fold increase in the activity of ornithine decarboxylase. Increased enzyme activity preceded the emergence of germ tubes and reached a maximum before conversion was completed. Subsequently, enzyme levels rapidly declined, despite the continuation of mycelial growth. Both putrescine and spermidine blocked the enzyme activity response. Protein synthesis was required for the increase in enzyme activity during morphogenesis. A combination of actinomycin D and netropsin inhibited ribonucleic acid synthesis but failed to inhibit the increase in ornithine decarboxylase activity. There was a twofold increase in the enzyme half-life during morphogenesis with either trichodermin or verrucarin to inhibit protein synthesis.

Carboxy-Lyases↗
PubMed1980

Strain variation and morphogenesis of yeast- and mycelial-phase Candida albicans in low-sulfate, synthetic medium.

A low-sulfate synthetic medium was developed in which pure cultures of yeast- and mycelial-phase Candida albicans could be cultivated for investigations of the molecular biology of dimorphism. The medium contained ammonium ions, phosphate buffer, salts, glucose, and biotin. Morphogenesis was found to be dependent upon the strain of C. albicans. Of six strains tested in the low-sulfate medium at 37 degrees C, three formed mixed cultures of yeasts, true mycelium and pseudomycelium, two formed pure cultures of true mycelium, and one maintained yeast growth. All six strains produced pure cultures of yeasts at 24 degrees C. The buffering capacity of the medium maintained the pH at 6.9 even at high-density cell growth. The low concentration of sulfate and the absence of amino acids in the medium provided conditions in which to radiolabel cellular constituents with [35S]sulfate. For molecular investigations, the use of two strains is suggested, one forming yeasts and one forming true mycelium in low-sulfate medium at 37 degrees C, thus providing controls for both strain variation and for molecular changes induced by environmental change but unrelated to morphogenesis.

Amino Acids↗
PubMed1980

Reproduction and morphogenesis of Rickettsiella chironomi, an unusual intracellular procaryotic parasite of midge larvae.

The reproduction and morphogenesis of Rickettsiella chironomi, an unusual procaryotic parasite of midge larvae, was studied with electron microscopy. The morphogenic cycle was similar to that found in chlamydia and consisted of four major cell types: (i) medium-sized spherical initial bodies (ca. 1 micrometers in diameter), (ii) large spherical initial bodies (1.5-2 micrometers), (iii) spherical intermediate bodies (600 to 700 nm), and (iv) disk-shaped elementary bodies (60 X 600 nm). The primary mode of reproduction involved binary fission of initial bodies to form other initial bodies or intermediate bodies. Each intermediate body condensed, forming an elementary body. The morphogenesis of R. chironomi is compared with that of several other organisms to which it is possibly related, including vertebrate chlamydia and invertebrate pathogens of the genera Rickettsiella and Porochlamydia, and its taxonomic position in regard to these is discussed. Additionally, a brief description of the pathology caused by the development of R. chironomi in larvae of Chironomus decorus and Chironomus frommeri is given.

Alphaproteobacteria↗
PubMed1988

Sequential regulation of developmental events during polar morphogenesis in Caulobacter crescentus: assembly of pili on swarmer cells requires cell separation.

Pili, along with the flagellum and DNA bacteriophage receptors, are structural markers for polar morphogenesis in Caulobacter crescentus. Pili act as primary receptors for a number of small, C. crescentus-specific DNA and RNA bacteriophages, and the timing of pilus-dependent adsorption of bacteriophage phiCb5 in synchronized cell populations has led to the general conclusion that pili are formed coordinately with the flagellum and other polar surface structures in the predivisional cell. The use of rotary platinum shadow casting and electron microscopy as a direct assay for formation of flagella and pili in synchronous cell cultures now shows, however, that when expressed as fractions of the swarmer cell cycle, flagella are assembled on the predivisional cells at approximately 0.8 and that pili are assembled on the new swarmer cells at approximately 0.1 of the next cell cycle. Adsorption of pilus-specific bacteriophage phiCb5 prevented the loss of pili from swarmer cells during development, which suggests that these structures are retracted at the time of stalk formation. Examination of temperature-sensitive cell division mutants showed that the assembly of pili depends on completion of cell separation. These results indicate that the stage-specific events required for polar morphogenesis in C. crescentus occur sequentially, rather than coordinately in the cell cycle, and that the timing of these events reflects the order of underlying cell cycle steps.

Bacteria↗
PubMed1991

Genetic regulation of morphogenesis in Bacillus subtilis: roles of sigma E and sigma F in prespore engulfment.

Electron microscopic examination of sporulating cultures of wild-type Bacillus subtilis revealed that the morphological events previously characterized as stages II and III can be divided into four substages, namely, stages IIi, IIii, IIiii, and III. The ultrastructural phenotypes of several stage II mutant strains indicate that each of the four substages has a biochemical and genetic basis. Two of the genes needed for the transition from stage II to stage III encode transcription factors sigma E and sigma F. Their roles during spore morphogenesis have been the subject of much speculation. We now show that sigma E controls genes involved in the morphological transition from stage IIi to stage IIii and then stage IIiii, while the transition to stage III may be determined by genes controlled by sigma F. The results also indicate the existence of at least two undiscovered sporulation genes involved in B. subtilis spore morphogenesis.

Bacillus subtilis↗
PubMed1997

Hook-length control of the export-switching machinery involves a double-locked gate in Salmonella typhimurium flagellar morphogenesis.

During flagellar morphogenesis in Salmonella typhimurium, the genes involved in filament assembly are expressed fully only after completion of hook-basal body assembly. This coupling of gene expression to morphogenesis is achieved by exporting the flagellum-specific anti-sigma factor, FlgM, out of the cell through the mature hook-basal body structure. Therefore, the flagellum-specific export apparatus must be able to sense the assembly state of the flagellar structure and to turn on FlgM export at a specific stage of hook assembly. It has been suggested that FlhB may act as the molecular switch which mediates this ordered export. Here, I report genetic evidence that in addition to FlhB, the product of a newly identified gene, rflH, is involved in the negative regulation of FlgM export. FlgM is released through the basal body structure lacking the hook and the filament only when the flhB and rflH genes are both defective. Therefore, the export gate for FlgM should be double locked by FlhB and RflH. The rflH gene is located at around 52 min, where no flagellum-related gene has been found. I propose a revised model of the export-switching machinery which consists of two systems, the hook-length signal transduction pathway and the double-locked gate for FlgM export.

Bacterial Proteins↗
PubMed2003

Identification of three new genes involved in morphogenesis and antibiotic production in Streptomyces coelicolor.

We report the isolation and partial characterization of three new mutants of Streptomyces coelicolor that are defective in morphogenesis and antibiotic production. The genes identified by the mutations were located and cloned by using a combination of Tn5 in vitro mutagenesis, cotransformation, and genetic complementation. Mutant SE69 produces lower amounts of antibiotics than the wild type produces, produces spores only after prolonged incubation on rich media, and identifies a gene whose predicted protein product is similar to the GntR family of transcriptional regulators; also, production of aerial mycelia on both rich and poor media is significantly delayed in this mutant. Mutant SE293 is defective in morphogenesis, overproduces antibiotics on rich media, fails to grow on minimal media, and identifies a gene whose predicted protein product is similar to the TetR family of transcriptional regulators. Preliminary evidence suggests that the SE293 gene product may control a molybdopterin binding protein located immediately adjacent to it. Mutant SJ175 sporulates sooner and more abundantly than the wild type and overproduces antibiotics on rich media, and it identifies a gene whose predicted protein product contains regions of predominantly hydrophobic residues similar to those of integral membrane proteins.

Amino Acid Sequence↗