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Results for “Developmental programming”

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At least 289 records · Page 16Linked to original sources

PubMed1991

Cells from Hertwig's epithelial root sheath do not transcribe amelogenin.

Recent experimental evidence has led to the interpretation that "enamel-like" material is deposited along the forming mouse molar root surface by cells of Hertwig's epithelial root sheath (HERS cells) and that this material is integral to the developmental program for cementogenesis. The experimental strategy described in this study was to examine selected developmental stages of root formation for mouse first and second mandibular molars in order to localize the cellular sites of amelogenin gene transcripts using high resolution in situ hybridization. Amelogenin is the major structural protein of coronal enamel and is highly conserved among mammalian species at the DNA and amino acid sequence level. Within the limits of sensitivity for in situ hybridization and utilizing either cRNAs or oligodeoxynucleotide probes, we were unable to localize amelogenin transcripts within HERS cells from selected developmental stages associated with mouse molar root formation. In contrast, previous studies using antipeptide antibodies have provided immuno-histochemical localization of amelogenin domains in HERS cell-derived products. For these HERS cell-derived proteins to contain both amelogenin epitopes and yet fail to yield nucleic acid hybridization signals suggests that either gene rearrangement and/or alternative processing of messenger RNAs from the structural gene locus operate to produce immunologically related motifs sharing insufficient complementarity at the nucleotide level to permit efficient detection by hybridization. It is postulated that HERS cells synthesize proteins which contain amelogenin domains and that these proteins participate during cementogenesis. However, these enamel-related proteins are neither identical to, nor collinear with coronal canonical amelogenin transcripts.

Ameloblasts↗

PubMed2003

EphA family gene expression in the developing mouse neocortex: regional patterns reveal intrinsic programs and extrinsic influence.

Parcellation of the mammalian cerebral cortex into distinct areas is essential for proper cortical function; however, the developmental program that results in the genesis of distinct areas is not fully understood. We examined the expression of members of the EphA family-the EphA receptor tyrosine kinases and the ephrin-A ligands-within the developing mouse cerebral cortex, with the aim of characterizing this component of the molecular landscape during cortical parcellation. We found that specific embryonic zones, such as the ventricular, subventricular, intermediate, subplate, and marginal zones, as well as the cortical plate, were positive for particular EphA genes early in corticogenesis (E12-E15). Along with this zone-selective expression, several genes (EphA3, EphA4, EphA5) were evenly expressed along the axes of the developing cortex, whereas one family member (EphA7) was expressed in a distinct anteroposterior pattern. Later in corticogenesis (E16-E18), other EphA family members became selectively expressed, but only within the cortical plate: EphA6 was present posteriorly, and ephrin-A5 was expressed within a middle region. At birth, patterning of EphA gene expression was striking. Thus, we found that the expression of a single EphA gene or a combination of family members can define distinct embryonic zones and anteroposterior regions of the neocortex during development. To examine whether cellular context affects the patterning of EphA expression, we examined gene expression in embryonic cortical cells grown in vitro, such that all cellular contacts are lacking, and in Mash-1 mutant mice, in which thalamocortical connections do not form. We found that the expression patterns of most EphA family members remained stable in these scenarios, whereas the pattern of ephrin-A5 was altered. Taken together, this work provides a comprehensive picture of EphA family expression during mouse corticogenesis and demonstrates that most EphA expression profiles are cell intrinsically based, whereas ephrin-A5 is plastically regulated.

Afferent Pathways↗

PubMed1987

Cancer genes, proto-oncogenes, and development.

The retroviral cancer genes have in a number of observations been shown to interfere with the developmental program of target cells. Here we are concerned with the interface between cancer genes/proto-oncogenes and developmental processes. Research in this field serves two purposes; to delineate key developmental controls and to identify these as targets for oncogenic agents.

Animals↗

PubMed2003

Temporal regulation of microRNA expression in Drosophila melanogaster mediated by hormonal signals and broad-Complex gene activity.

lin-4 and let-7 are founding members of an extensive family of genes that produce small transcripts, termed microRNAs (miRNAs). In Caenorhabditis elegans, lin-4 and let-7 control the timing of postembryonic events by translational repression of target genes, permitting progression from early to late developmental programs. To identify Drosophila melanogaster miRNAs that could play similar roles in the control of developmental timing, we characterized the developmental expression profile of 24 miRNAs in Drosophila, and found 7 miRNAs that are either upregulated or downregulated in conjunction with metamorphosis. The upregulation of three of these miRNAs (mir-100, mir-125, and let-7), and the downregulation of a fourth (mir-34) requires the hormone ecdysone (Ecd) and the activity of the Ecd-inducible gene Broad-Complex. Interestingly, mir-125 is a putative homologue of lin-4. mir-100, -125, and let-7 are clustered within an 800-bp region on chromosome 2L, suggesting that these three miRNAs may be coordinately regulated via common cis-acting elements during metamorphosis. In S2 cells, Ecd and the juvenile hormone analog methoprene exert opposite effects on the expression of these four miRNAs, indicating the participation of both these hormones in the temporal regulation of mir-34, -100, -125, and let-7 expression in vivo.

Animals↗

PubMed2002

Plant development meets cell proliferation in Madrid.

Cell division is intimately intertwined with plant development, and the mechanisms that link the control of cell proliferation and differentiation with the processes of organogenesis, morphogenesis, and growth are starting to be understood. A recent Juan March meeting explored this interface, and revealed a rich seam of exciting work that is leading toward an integrated view of the role of cell proliferation in the unfolding of developmental programs.

Cell Division↗

PubMedDate not supplied

Deuterostome evolution: early development in the enteropneust hemichordate, Ptychodera flava.

Molecular and morphological comparisons indicate that the Echinodermata and Hemichordata represent closely related sister-phyla within the Deuterostomia. Much less is known about the development of the hemichordates compared to other deuterostomes. For the first time, cell lineage analyses have been carried out for an indirect-developing representative of the enteropneust hemichordates, Ptychodera flava. Single blastomeres were iontophoretically labeled with Dil at the 2- through 16-cell stages, and their fates followed through development to the tornaria larval stage. The early cleavage pattern of P. flava is similar to that of the direct-developing hemichordate, Saccoglossus kowalevskii, as well as that displayed by indirect-developing echinoids. The 16-celled embryo contains eight animal "mesomeres," four slightly larger "macromeres," and four somewhat smaller vegetal "micromeres." The first cleavage plane was not found to bear one specific relationship relative to the larval dorsoventral axis. Although individual blastomeres generate discrete clones of cells, the appearance and exact locations of these clones are variable with respect to the embryonic dorsoventral and bilateral axes. The eight animal mesomeres generate anterior (animal) ectoderm of the larva, which includes the apical organ; however, contributions to the apical organ were found to be variable as only a subset of the animal blastomeres end up contributing to its formation and this varies from embryo to embryo. The macromeres generate posterior larval ectoderm, and the vegetal micromeres form all the internal, endomesodermal tissues. These blastomere contributions are similar to those found during development of the only other hemichordate studied, the direct-developing enteropneust, S. kowalevskii. Finally, isolated blastomeres prepared at either the two- or the four-cell stage are capable of forming normal-appearing, miniature tornaria larvae. These findings indicate that the fates of these cells and embryonic dorsoventral axial properties are not committed at these early stages of development. Comparisons with the developmental programs of other deuterostome phyla allow one to speculate on the conservation of some key developmental events/mechanisms and propose basal character states shared by the ancestor of echinoderms and hemichordates.

Animals↗

PubMed1994

DET1, a negative regulator of light-mediated development and gene expression in arabidopsis, encodes a novel nuclear-localized protein.

The mechanisms by which plants integrate light signals to modify endogenous developmental programs are largely unknown. One candidate for a signal transduction component that may integrate light with developmental pathways is the Arabidopsis DET1 gene product. Here we report the positional cloning of the DET1 locus and show that DET1 is a unique nuclear-localized protein. An analysis of a number of det1 mutants indicates that mutants with partial DET1 activity develop as light-grown plants in the dark. det1 null mutants share this phenotype, but also display severe defects in temporal and spatial regulation of gene expression. These results suggest that DET1 acts in the nucleus to control the cell type-specific expression of light-regulated promoters.

Amino Acid Sequence↗

PubMed2003

Molecular genetics of leaf senescence in Arabidopsis.

Leaf senescence is a developmentally programmed degeneration process that constitutes the final step of leaf development and is controlled by multiple developmental and environmental signals. In addition to the information obtained from other plants, Arabidopsis has, as a model system, contributed to our understanding of this complex phenomenon in molecular genetic terms. Recent discoveries have identified several genetic mutants and potential regulatory components in Arabidopsis. Identifying further mutants that exploit novel biological resources, screening Scheme and a global functional analysis of senescence-associated genes in Arabidopsis should increase our understanding of the complex regulatory networks.

Aging↗

PubMed2002

To die or not to die, does it change the function? Behavior of transgenic mice reveals a role for developmental cell death.

In humans, perturbations in the developmental neuronal death leading to an excess of neurons could be associated with developmental neuropsychiatric disorders. Hu-bcl-2 transgenic mice appear to be a valuable tool to study the functional role of developmental programmed cell death. Indeed, the over-expression of the anti-apoptotic gene bcl-2 decreases developmental neuronal death and Hu-bcl-2 mice present supernumerary neurons in several brain regions. A detailed behavioral analysis of these mice revealed selective deficits. Hu-bcl-2 mice have normal vision, general activity and motor skills. Only the most complex behavior like anxiety and learning abilities are impaired in these mice.

Animals↗

PubMed1999

Short communication: developmental control of Xa21-mediated disease resistance in rice.

The rice resistance gene Xa21 confers resistance against the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo). The molecular genetic mechanism controlling the integration of the Xa21-mediated disease resistance response with the developmental program in rice is under study in this model system. Reproducible means of infecting plants at certain developmental stages were designed based on the timing of full expansion of the leaf. Xa21-resistance progressively increases from the susceptible juvenile leaf 2 stage through later stages, with 100% resistance at the adult leaf 9/10 stage. We found that Xa21 expression is independent of plant developmental stage, infection with Xoo, or wounding. Expression of the Xa21 gene transcript is not correlated with expression of Xa21 disease resistance indicating that the developmental regulation of Xa21-resistance is either controlled post-transcriptionally or by other factors.

Gene Expression↗

PubMedDate not supplied

Use of biological markers in occupational health research and practice.

The promise of biological markers in occupational health research and practice has been described in the scientific literature. The current generation of biological markers has the potential to allow for the earlier detection of disease, for the reduction of misclassification of exposure and outcome, for heightened understanding of mechanisms and etiologic pathways, and for the designation of groups at risk. What is necessary now is a strategy for realizing this potential. The elements of such as a strategy may include the following: (1) a program to validate biomarkers, (2) increased utilization of valid biomarkers in etiologic and prevention research, and (3) developmental programs to encourage interdisciplinary collaboration and train molecular epidemiologists. A framework for linking biomarkers and epidemiologic study designs has evolved during the past 5 yr. For this progress to continue, it is important that discussion about biomarkers reflect a specificity with regard to both the type of marker and the use for which it is intended.

Biomarkers↗

PubMed1998

Developmental regulation of a cyclin-dependent kinase inhibitor controls postembryonic cell cycle progression in Caenorhabditis elegans.

C. elegans cki-1 encodes a member of the CIP/KIP family of cyclin-dependent kinase inhibitors, and functions to link postembryonic developmental programs to cell cycle progression. The expression pattern of cki-1::GFP suggests that cki-1 is developmentally regulated in blast cells coincident with G1, and in differentiating cells. Ectopic expression of CKI-1 can prematurely arrest cells in G1, while reducing cki-1 activity by RNA-mediated interference (RNAi) causes extra larval cell divisions, suggesting a role for cki-1 in the developmental control of G1/S. cki-1 activity is required for the suspension of cell cycling that occurs in dauer larvae and starved L1 larvae in response to environmental signals. In vulva precursor cells (VPCs), a pathway of heterochronic genes acts via cki-1 to maintain VPCs in G1 during the L2 stage.

Animals↗

PubMed1991

Heat shock and thermotolerance in plant and animal embryogenesis.

Although the strategies of early embryogenesis differ greatly among multicellular eukaryotes, there are certain parallels in structure, form, and function that cross even kingdom lines: the extreme heat sensitivity of zygotes and very early embryos, followed by the acquisition of thermotolerance during subsequent development, is one such parallel. The heat sensitivity may be so extreme that even moderate increases in temperature result in lethality (generally associated with the earliest phases of embryogenesis), or the effects may be less severe, resulting in defects in development but not in lethality. Mechanistically, and molecularly, these two forms of thermosensitivity appear to have different origins. On the one hand, outright lethality appears to result from an inability to induce heat shock genes and proteins; on the other hand, heat-induced developmental defects appear to result from an alteration in expression of non-heat shock genes and from a delay in the overall developmental program that generally accompanies the cell's response to heat shock. This review is focused on the developmental regulation of the heat shock response during early embryogenesis and on the impact of this regulation on the development of both animal and plant embryos. The two basic issues that we address here are (i) the expression of heat shock genes in the absence of heat shock during embryogenesis and (ii) the expression (or lack of expression) of heat shock genes after deliberate exposure of the embryos to heat shock and the consequences of this expression on its subsequent survival and development.

Animals↗

PubMed1990

Tissue-specific distribution and developmental regulation of M and B creatine kinase mRNAs.

To characterize the tissue-specific distribution and developmentally regulated expression of M and B creatine kinase mRNA in rats, total cellular RNA was isolated from adult rat tissues and from skeletal muscle, heart, brain and intestine at selected stages of development. Northern blots were prepared and hybridized with M and B subunit-specific probes derived from the 3'-untranslated region. M creatine kinase mRNA was expressed abundantly in heart and skeletal muscle, and less abundantly in lung. B creatine kinase mRNA was found in all tissues examined except liver and was abundant in brain, heart and intestine. The developmentally regulated expression of M and B creatine kinase mRNA was determined in skeletal muscle, heart, brain and intestine. The developmental program of B creatine kinase mRNA was different for each tissue examined. During development, M creatine kinase mRNA was up-regulated in both heart and skeletal muscle with a different regulatory program. This resulted in replacement of B mRNA by M mRNA as the predominant species at an earlier developmental stage in heart when compared to skeletal muscle.

Animals↗

PubMed1987

Superinduction of the Dictyostelium discoideum cell surface cAMP receptor by pulses of cAMP.

Extracellular cAMP plays a crucial role in regulating the developmental program of Dictyostelium discoideum, functioning as a chemotactic agent, as well as a signal that regulates expression of developmentally expressed genes. These activities appear to be mediated by a cell-surface receptor for cAMP. We have studied the regulation of this receptor in cells developed in starved suspension cultures exposed to 50 nM pulses of cAMP every 6 min. cAMP-pulsed cells display roughly 10-fold higher cAMP receptor levels than cells that developed on filters or that were starved in suspension without cAMP pulses. Based on saturation binding analysis, the superinduced binding activity represents an increase in receptor number, while receptor affinity for cAMP is unaffected. Photoaffinity labeling of superinduced cells results in specific labeling of the same molecules that are labeled in starved cells. This increased cAMP binding activity was also detected in membrane preparations from cAMP-pulsed cells. These results provide evidence for an unusual mode of receptor regulation: autogenous induction of the receptor by its ligand.

Affinity Labels↗

PubMed1993

Two transmembrane signaling mechanisms control expression of the cAMP receptor gene CAR1 during Dictyostelium development.

Dictyostelium discoideum is among the best characterized organisms for the study of receptor/guanine nucleotide binding protein-mediated control of differentiation. Dictyostelium grow unicellularly but form fully differentiated multicellular organisms through a developmental program regulated by secreted cAMP activating specific cell-surface receptors. Dictyostelium respond differentially to cAMP at different developmental stages. During early development, expression of certain genes is induced by low-level oscillations of extracellular cAMP. Later, continuous, high cAMP concentrations will promote expression of specific genes in multicellular structures. Here, we show that the cAMP receptor gene CAR1, which is essential for development, utilizes two promoters that are activated at distinct stages of development and respond to different extracellular cAMP conditions. One promoter is active with low-level oscillations of cAMP; exposure to high cAMP concentrations will repress this promoter and induce a second promoter. The CAR1 mRNAs are alternatively spliced but encode identical proteins. Thus, through differential sensitivity to its own ligand, cAMP, two promoters and alternative splicing regulate CAR1 expression during Dictyostelium development.

Alternative Splicing↗

PubMed1994

Pre- and postnatal ontogeny of aromatase cytochrome P450 messenger ribonucleic acid expression in the male rat brain studied by in situ hybridization.

A central step in the development and sexual differentiation of the brain is the intraneuronal conversion of testosterone to estrogen. This conversion is catalyzed by an enzyme complex comprised of cytochrome P450 aromatase and the ubiquitous NADPH-dependent cytochrome P450 reductase. Brain aromatase activity is developmentally regulated and expressed only in specific hypothalamic and limbic structures. To determine whether developmental change in aromatase activity are the result of differential regulation of aromatase gene expression, we designed two specific oligonucleotides complementary to a 5'-region or to the heme-binding region of the rat aromatase complementary DNA. Relative amounts of messenger RNA (mRNA) encoding aromatase cytochrome P450 were examined on cryostat sections from male fetuses and offspring of time-pregnant Long-Evans rats using the in situ hybridization technique. On gestational day (GD) 16 (GD 1 = 24 h after mating), aromatase-specific mRNA was detected in the preoptic/hypothalamic area. On GD18 and GD20, aromatase mRNA expression was more abundant and more widespread. High levels of mRNA were detected in the medical preoptic nucleus, the sexually dimorphic nucleus of the preoptic area, the bed nucleus of stria terminalis, and the medial amygdala. Lower levels were found in the periventricular preoptic nucleus and the ventromedial hypothalamic nucleus. On postnatal day (PN) 2 and throughout further development (PN6, PN15, and adult), aromatase mRNA decreased to much lower levels in the preoptic area, but remained high in the bed nucleus of stria terminalis and amygdala. An intermediate situation, i.e. transient expression with a peak around birth, was observed for aromatase mRNA levels in the ventromedial hypothalamic nucleus. Interestingly, during early postnatal development, specific aromatase mRNA was also detected in the hippocampal formation as well as in the subfornical organ. In summary, these results demonstrate that the low quantities of aromatase transcripts in the developing rat brain can be detected by means of in situ hybridization. Depending on the particular region examined, aromatase expression appears to be subjected to different developmental programs. As the expression of aromatase mRNA parallels the results obtained from activity assays, it is likely that developmental changes in aromatase activity are the result of regulation of aromatase gene expression.

Animals↗

PubMed2003

Development gene networks and evolution.

Animal development relies on complex programs of gene regulation that are likely to account for a significant fraction of the information carried in genomes. The evolution of these regulatory programs is a major contributor to the diversity of animal forms, yet the architecture of the transcriptional networks that comprise developmental programs is only beginning to come into focus. The sea urchin offers an uncomplicated system in which to study transcriptional regulation and the networks that direct embryogenesis. This review describes the approaches that we are taking towards this problem using the sea urchin embryo and some comparative methods that will eventually lead to a deeper understanding of the evolution of developmental networks.

Animals↗