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Down regulation by p60v-src of genes specifically expressed and developmentally regulated in postmitotic quail neuroretina cells.

The avian neuroretina (NR) is composed of photoreceptors and different neurons that are derived from proliferating precursor cells. Neuronal differentiation takes place after terminal mitosis. We have previously shown that differentiating NR cells can be induced to proliferate by infection with Rous sarcoma virus (RSV) and that cell multiplication requires expression of a functional v-src gene. We speculated that the quiescence of NR cells could be determined by specific genes. Cell proliferation could then result from the negative regulation of these genes by the v-src protein. By differential hybridization of a cDNA library, we isolated eight clones corresponding to genes expressed in postmitotic NR cells from 13-day-old quail embryos, transcriptional levels of which are significantly reduced in NR cells induced to proliferate by tsNY68, an RSV mutant with temperature-sensitive mitogenic activity. Partial sequencing analysis indicated that one RNA encoded the calmodulin gene, whereas the other seven showed no similarity to known sequences. By using v-src mutants that induce NR cell proliferation in the absence of transformation, we showed that transcription of six genes was negatively regulated by the v-src protein and that of four genes was correlated with NR cell quiescence. We also report that a subset of genes are specifically transcribed in neural cells and developmentally regulated in the NR. These results indicate that the v-src protein regulates expression of genes likely to play a role in the control of neural cell growth or differentiation.

Animals↗

A homeodomain protein binds to gamma-globin gene regulatory sequences.

Developmental regulation of gamma-globin gene expression probably occurs through developmental-stage-specific trans-acting factors able to promote the interaction of enhancer elements located in the far upstream locus control region with regulatory elements in the gamma gene promoters and 3' A gamma enhancer located in close proximity to the genes. We have detected a nuclear protein in K562 and baboon fetal bone marrow nuclear extracts capable of binding to A+T-rich sequences in the locus control region, gamma gene promoter, and 3' A gamma enhancer. SDS/polyacrylamide gel analysis of the purified K562 binding activity revealed a single protein of 87 kDa. A K562 cDNA clone was isolated encoding a beta-galactosidase fusion protein with a DNA binding specificity identical to that of the K562/fetal bone marrow nuclear protein. The cDNA clone encodes a homeodomain homologous to the Drosophila antennapedia protein.

Animals↗

Comparison of the tissue-specific expression and developmental regulation of two closely linked rodent genes encoding cytosolic retinol-binding proteins.

Cellular retinol-binding protein (CRBP) and cellular retinol-binding protein II (CRBP II) are two highly homologous cytoplasmic proteins that bind all-trans-retinol. We have recently demonstrated that the mouse genes encoding CRBP and CRBP II are closely linked on chromosome 9 and that both human genes are located on chromosome 3 (Demmer, L.A., Birkenmeier, E.H., Sweetser, D.A., Levin, M.S., Zollman, S., Sparkes, R.S., Mohandas, T., Lusis, A.J., and Gordon, J.I. (1987) J. Biol. Chem. 262, 2458-2467). We have now used RNA blot hybridization analysis to assess the degree to which these genes are coordinately expressed in fetal, suckling, weaning, and adult rat tissues. Both genes exhibit different developmental patterns of expression in liver, intestine, lung, kidney, testes, and placenta. In the intestine, CRBP mRNA was detected during the 16th day of gestation--prior to the development of a well-differentiated absorptive epithelium--and remained essentially unchanged throughout the peri- and postpartum periods. By contrast, the pattern of intestinal CRBP II mRNA accumulation closely parallels the times of first appearance, and subsequent proliferation, of the intestinal absorptive columnar epithelium, supporting the hypothesis that CRBP II is involved in the intestinal uptake or intracellular trafficking of this hydrophobic vitamin. In the fetal liver, both genes were expressed by gestational day 16. Whereas the concentration of hepatic CRBP mRNA increased markedly during the suckling and early weaning periods, CRBP II mRNA levels fell abruptly immediately after birth. These peripartum changes were not paralleled by remarkable alterations in the steady state levels of hepatic retinol. Marked changes in the expression of CRBP in the liver and of CRBP II in the intestine were also documented in pregnant and lactating female rats. These differences in CRBP/CRBP II gene expression strongly suggest that their proteins serve different physiological functions. The peripartum liver may provide a useful model for dissecting the relative roles played by these homologous proteins in retinoid metabolism as well as the factors which modulate activation and repression their genes.

Animals↗

Characterization of mutants in Arabidopsis showing increased sugar-specific gene expression, growth, and developmental responses.

Sugars such as sucrose serve dual functions as transported carbohydrates in vascular plants and as signal molecules that regulate gene expression and plant development. Sugar-mediated signals indicate carbohydrate availability and regulate metabolism by co-coordinating sugar production and mobilization with sugar usage and storage. Analysis of mutants with altered responses to sucrose and glucose has shown that signaling pathways mediated by sugars and abscisic acid interact to regulate seedling development and gene expression. Using a novel screen for sugar-response mutants based on the activity of a luciferase reporter gene under the control of the sugar-inducible promoter of the ApL3 gene, we have isolated high sugar-response (hsr) mutants that exhibit elevated luciferase activity and ApL3 expression in response to low sugar concentrations. Our characterization of these hsr mutants suggests that they affect the regulation of sugar-induced and sugar-repressed processes controlling gene expression, growth, and development in Arabidopsis. In contrast to some other sugar-response mutants, they do not exhibit altered responses to ethylene or abscisic acid, suggesting that the hsr mutants may have a specifically increased sensitivity to sugars. Further characterization of the hsr mutants will lead to greater understanding of regulatory pathways involved in metabolite signaling.

Abscisic Acid↗

Alternative RNA processing events as a critical developmental regulatory strategy in neuroendocrine gene expression.

Alternative RNA processing events, consequential to alternative poly(A) site selection, represent the critical developmental strategy dictating the tissue-specific pattern of the polypeptide product production in calcitonin gene expression. The consequence of these events is the production of an mRNA encoding the precursor of a novel neuropeptide, referred to as CGRP, in the brain and an mRNA encoding the precursor to calcitonin in the thyroidal C cells. A trans-acting mechanism appears to adjudicate the critical choice of poly(A) site. It is suggested that this type of RNA processing regulation is a commonly used mechanism, of particular importance in expression of genes modulating neural developmental events.

Amino Acid Sequence↗

Differential expression of a lipid transfer protein gene in cotton fiber.

A full-length cDNA clone, GH3, has been isolated from a cotton fiber cDNA library using a differential screening method. The nucleotide and derived amino acid sequence data show that GH3 encodes a lipid transfer protein (LTP) of 120 amino acids. The presence of a transmembrane signal peptide at the N-terminal of the protein would suggest its possible outer cellular location in fiber cells. Northern analysis indicates that the GH3 gene is developmentally regulated.

Amino Acid Sequence↗

Formation of an active tissue-specific chromatin domain initiated by epigenetic marking at the embryonic stem cell stage.

The differentiation potential of stem cells is determined by the ability of these cells to establish and maintain developmentally regulated gene expression programs that are specific to different lineages. Although transcriptionally potentiated epigenetic states of genes have been described for haematopoietic progenitors, the developmental stage at which the formation of lineage-specific gene expression domains is initiated remains unclear. In this study, we show that an intergenic cis-acting element in the mouse lambda5-VpreB1 locus is marked by histone H3 acetylation and histone H3 lysine 4 methylation at a discrete site in embryonic stem (ES) cells. The epigenetic modifications spread from this site toward the VpreB1 and lambda5 genes at later stages of B-cell development, and a large, active chromatin domain is established in pre-B cells when the genes are fully expressed. In early B-cell progenitors, the binding of haematopoietic factor PU.1 coincides with the expansion of the marked region, and the region becomes a center for the recruitment of general transcription factors and RNA polymerase II. In pre-B cells, E2A also binds to the locus, and general transcription factors are distributed across the active domain, including the gene promoters and the intergenic region. These results suggest that localized epigenetic marking is important for establishing the transcriptional competence of the lambda5 and VpreB1 genes as early as the pluripotent ES cell stage.

Acetylation↗

Light and developmental regulation of the gene con-10 of Neurospora crassa.

The gene con-10 of Neurospora crassa is expressed preferentially during conidiation and following illumination of vegetative mycelia with blue light. In this study we have examined the segmental locations of the genetic elements associated with con-10 that are responsible for light and developmental expression. A translational fusion was prepared between the initial segment of con-10 and Escherichia coli lacZ. Deletions were then introduced into the con-10 upstream region associated with this translational fusion. Each construct was integrated at the his-3 locus of N. crassa by transformation and homologous recombination. Photoinduction of mycelia containing the translational fusion with the intact upstream region revealed a two phase stimulus-response curve. Exposure to light for as little as 5 sec induced a transcriptional response. Following this initial induction, a period of 15 min in the dark or light was required for appearance of a second phase response. Only a brief light treatment was necessary for induction of the second phase response. Deletions within the upstream region altered normal light and developmental expression of constructs containing the con-10-lacZ translational fusion. The deleted segments appear to contain a mycelial repression site, two conidiation activation sites, and two dark repression sites. A repeated 17-bp sequence acted as a transcriptional enhancer. One copy of this enhancer is in the upstream region. The second copy, with the opposite orientation, is located in the first con-10 intron. The enhancer was required for proper mycelial and conidial expression of the con-10-lacZ fusion. The initial 10 bp of this enhancer sequence were sufficient to restore conidial expression to a deletion construct lacking both copies of the 17-bp repeat. Proteins were detected in extracts of mycelia and conidia that specifically bound to the enhancer sequence in vitro. Our findings suggest that conidiation-specific and mycelial-specific expression of con-10 requires the action of several factors acting independently and/or in concert at distinct sites located in the regulatory regions for con-10.

Base Sequence↗

The H19 TATA-less promoter is efficiently repressed by wild-type tumor suppressor gene product p53.

The developmentally regulated H19 gene displays several remarkable properties: expression of an apparently non-translated mRNA, genomic imprinting (maternal allele only expressed), relaxation of the imprinting and/or epigenetic lesions demonstrated in some tumors. Despite several observations after relaxation of imprinting status of the gene, data on trans and cis-acting factors required for the human H19 gene expression are still missing. As a first approach to address identification of factors involved in the regulation of the gene, we found that cells from a p53 antisense-transfected HeLa clone displayed increased amounts of H19 transcripts when compared to the non-transfected cells. Moreover, a HeLa clone stably transfected with a temperature sensitive (ts) 143 Ala p53 mutant exhibited temperature-dependent regulation of H19 expression. This preliminary indication of the repressing effect of the p53 protein on H19 expression has been confirmed by transient cotransfection experiments in HeLa cells, using luciferase surrogate constructs under the control of the 823 bp sequence immediately upstream of the transcription start point of the H19 gene, and different constructs containing sense, antisense or a ts 143 Ala mutant p53 cDNA. We observed an increase of H19 promoter-driven activity in transient cotransfections with the antisense p53 cDNA and the temperature sensitive mutant p53 at the non-permissive temperature, but a decrease with sense wild-type p53 cDNA. Furthermore, the cotransfection experiments were repeated in a cell line lacking endogenous p53. (Calu 6 cells) and the results provided additional evidence for a down regulation of the expression of the H19 gene by the p53 protein.

Gene Expression Regulation, Neoplastic↗

Regulation of the rat cardiac troponin I gene by the transcription factor GATA-4.

Troponin I is a thin-filament contractile protein expressed in striated muscle. There are three known troponin I genes which are expressed in a muscle-fibre-type-specific manner in mature animals. Although the slow skeletal troponin I isoform is expressed in fetal and neonatal heart, the cardiac isoform is restricted in its expression to the myocardium at all developmental stages. To study the regulation of this cardiac-specific and developmentally regulated gene in vitro, the rat cardiac troponin I gene was cloned. Transient transfection assays were performed with troponin I-luciferase fusion plasmids to characterize the regulatory regions of the gene. Proximal regions of the upstream sequence were sufficient to support high levels of expression of the reporter gene in cardiocytes and relatively low levels in other cell types. The highest luciferase activity in the cardiocytes was noted with a plasmid that included the region spanning -896 to +45 of the troponin I genomic sequence. Co-transfection of GATA-4, a recently identified cardiac transcription factor, with troponin I-luciferase constructs permitted high levels of luciferase expression in non-cardiac cells. Electrophoretic mobility-shift assays demonstrated specific binding of GATA-4 to oligonucleotides representative of multiple sites of the troponin I sequence. Mutation of a proximal GATA-4 DNA-binding site decreased transcriptional activation in transfected cardiocytes. These results indicate that the proximal cardiac troponin I sequence is sufficient to support high levels of cardiac-specific gene expression and that the GATA-4 transcription factor regulates troponin I-luciferase expression in vitro.

3T3 Cells↗

The Bacillus subtilis sin gene, a regulator of alternate developmental processes, codes for a DNA-binding protein.

The sin gene of Bacillus subtilis encodes a dual-function regulatory protein, Sin, which is a negative as well as a positive regulator of alternate developmental processes that are induced at the end of vegetative growth in response to nutrient depletion. Sin has been purified to homogeneity by using a simple two-step procedure. It was found to bind to the developmentally regulated aprE (alkaline protease) gene at two sites in vitro. The stronger Sin-binding site (SBS-1) is located more than 200 bp upstream from the transcription start site. It is required for Sin repression of aprE expression in vivo, as strains bearing SBS-1 deletions were not affected by the sin gene. The second, weaker Sin-binding site lies on a DNA fragment that contains the aprE promoter. Results of DNase I, exonuclease III, and dimethyl sulfate footprinting analysis of SBS-1 suggested that Sin binding involves two adjacent binding sites which appear to contain two different partial dyad symmetries. An analysis of the predicted amino acid sequence of Sin revealed a potential leucine zipper protein dimerization motif which is flanked by two helix-turn-helix motifs that could be involved in recognizing two different dyad symmetries.

Amino Acid Sequence↗

Comparative transcriptome analysis reveals significant differences in gene expression and signalling pathways between developmental and dark/starvation-induced senescence in Arabidopsis.

An analysis of changes in global gene expression patterns during developmental leaf senescence in Arabidopsis has identified more than 800 genes that show a reproducible increase in transcript abundance. This extensive change illustrates the dramatic alterations in cell metabolism that underpin the developmental transition from a photosynthetically active leaf to a senescing organ which functions as a source of mobilizable nutrients. Comparison of changes in gene expression patterns during natural leaf senescence with those identified, when senescence is artificially induced in leaves induced to senesce by darkness or during sucrose starvation-induced senescence in cell suspension cultures, has shown not only similarities but also considerable differences. The data suggest that alternative pathways for essential metabolic processes such as nitrogen mobilization are used in different senescent systems. Gene expression patterns in the senescent cell suspension cultures are more similar to those for dark-induced senescence and this may be a consequence of sugar starvation in both tissues. Gene expression analysis in senescing leaves of plant lines defective in signalling pathways involving salicylic acid (SA), jasmonic acid (JA) and ethylene has shown that these three pathways are all required for expression of many genes during developmental senescence. The JA/ethylene pathways also appear to operate in regulating gene expression in dark-induced and cell suspension senescence whereas the SA pathway is not involved. The importance of the SA pathway in the senescence process is illustrated by the discovery that developmental leaf senescence, but not dark-induced senescence, is delayed in plants defective in the SA pathway.

Arabidopsis↗

Analysis of gene transcription in bovine nuclear transfer embryos reconstructed with granulosa cell nuclei.

The low efficiency of animal production using somatic cell nuclear transfer procedures is considered to be the result of an incomplete reprogramming of the donor somatic cell nucleus, which leads to a lack of, or abnormal expression of developmentally important genes. However, our current understanding of the process of somatic cell nuclear reprogramming and its effect on gene expression is limited. In this study, we compare the transcription patterns of six developmentally important genes, Oct4, IL6, FGF2, FGF4, FGFr2, and gp130 in single in vitro fertilized (IVF) and nuclear transfer embryos reconstructed using granulosa cells for the donor nuclei. Similar patterns of transcription were detected for Oct4, FGF2, and gp130 in IVF and nuclear transfer embryos during the preimplantation stages of development. However, a number of morula- and blastocyst-stage embryos derived from nuclear transfer procedures showed abnormal transcription of IL6, FGF4, and FGFr2. Previous studies have demonstrated that these three genes play an important role in implantation, early postimplantation development, or both in the mouse. Therefore, the aberrant transcription patterns detected in nuclear transfer embryos may lead to a reduction in embryo viability.

Animals↗

cDNA cloning, heat shock regulation and developmental expression of the hsp83 gene in the Mediterranean fruit fly Ceratitis capitata.

This report presents the cDNA cloning, heat shock regulation and developmental expression of the hsp90 gene homologue of the Mediterranean fruit fly Ceratitis capitata (medfly). The isolated cDNA contained the coding region, the 3'UTR and most of the 5'UTR of the medfly hsp90 homologue, which was named Cchsp83. The deduced CcHSP83 polypeptide contained all the highly conserved amino acid segments that characterize the cytosolic members of the HSP90 family. Genomic analysis showed that the Cchsp83 gene is unique and was mapped at the 94C division of the sixth polytene chromosome. The size of the Cchsp83 mRNA was found to be approximately 2.7 kb. The predicted molecular mass of the CcHSP83 protein was 81.4 kDa, while the apparent molecular weight estimated by SDS-PAGE was approximately 90 kDa. Phylogenetic analysis based on 14 insect HSP90 amino acid sequences was consistent with the known phylogeny at low taxonomic level. The Cchsp83 gene is constitutively expressed in all stages of medfly development and is induced from a low level to several-fold by heat, depending on the developmental stage. Heat shock induction begins at 30 degrees C, reaching a maximum between 35 and 41 degrees C. Cchsp83 RNA expression is highly regulated during embryonic development; however, the temporal fluctuations in RNA levels during embryogenesis were not followed by similar fluctuations in the levels of the protein.

Animals↗

Developmental expression of interstitial collagen genes in fetal bladders.

Bovine bladders at 3 stages during fetal development were examined for expression of collagens by immunohistochemistry as well as by measurement of steady state mRNA levels. Expression of type I and type III collagens during the fetal period was compared with that of adult cows as well as a young animal (heifer). Each bladder was separated into a detrusor and a urothelial-lamina propria sample which were then analyzed separately. Distribution and fiber arrangement of types I and III collagens were different depending upon the region of the bladder wall examined. Type III collagen, in particular, has a "coiled" appearance which is especially prominent within the lamina propria. Collagen gene expression showed a distinctive pattern which was different for both type I and type III collagen. While type I collagen gene expression peaked during the late second to early third trimester, type III collagen expression progressively decreased throughout the fetal period. In addition, expression of both collagens was greater in the urothelial-lamina propria fractions. These data demonstrate that the pattern of collagen gene expression in the developing bladder is developmentally regulated and is unique to each of the two major structural layers.

Animals↗

Identification and developmental expression of the ets gene family in the sea urchin (Strongylocentrotus purpuratus).

A systematic search in the available scaffolds of the Strongylocentrotus purpuratus genome has revealed that this sea urchin has 11 members of the ets gene family. A phylogenetic analysis of these genes showed that almost all vertebrate ets subfamilies, with the exception of one, so far found only in mammals, are each represented by one orthologous sea urchin gene. The temporal and spatial expression of the identified ETS factors was also analyzed during embryogenesis. Five ets genes (Sp-Ets1/2, Sp-Tel, Sp-Pea, Sp-Ets4, Sp-Erf) are also maternally expressed. Three genes (Sp-Elk, Sp-Elf, Sp-Erf) are ubiquitously expressed during embryogenesis, while two others (Sp-Gabp, Sp-Pu.1) are not transcribed until late larval stages. Remarkably, five of the nine sea urchin ets genes expressed during embryogenesis are exclusively (Sp-Ets1/2, Sp-Erg, Sp-Ese) or additionally (Sp-Tel, Sp-Pea) expressed in mesenchyme cells and/or their progenitors. Functional analysis of Sp-Ets1/2 has previously demonstrated an essential role of this gene in the specification of the skeletogenic mesenchyme lineage. The dynamic, and in some cases overlapping and/or unique, developmental expression pattern of the latter five genes suggests a complex, non-redundant function for ETS factors in sea urchin mesenchyme formation and differentiation.

Animals↗

Developmentally controlled selection of antibody genes: characterization of individual VH7183 genes and evidence for stage-specific somatic diversification.

Nucleotide sequence analysis of a large number of rearranged immunoglobulin heavy chain V region genes allowed the identification of six new members of the VH7183 gene family. These six new genes plus the eight previously defined genes agrees with the previously estimated complexity of this gene family. Twelve of these genes were represented among the isolated clones. A comparison of the clones, derived from 1-day- and 14-week-old BALB/c mice, suggested a biased and developmentally controlled VH7183 gene utilization. Furthermore, a developmentally controlled, non-random distribution of the functional vs. non-functional VHDJH rearrangements was observed among clones utilizing genes of this family, suggesting unsuspected regulatory aspects of Ig rearrangements in the process of B cell differentiation. Finally, a limited junctional diversity was revealed among the neonatal clones as the result of a low frequency of N-sequence addition. A similar discrepancy was also observed between neonatal and adult VHJ558 clones. In conclusion, these data suggest a programmed generation of B cell diversity similar to what has been observed for the establishment of gamma/delta T cell repertoires.

Animals↗

Role of trophic factors in muscle differentiation.

Muscle genes are developmentally regulated. In vivo, the differential expression of muscle structural genes during myogenesis is controlled in complex ways by extrinsic factors and by a pre-determined genetic program. Terminal differentiation, which is achieved when differentiated myoblasts fuse to form multi-nucleated myotubes, appears mainly regulated by intrinsic factors. Environmental components, on the other hand, play a significant role in the developmental regulation of genes during the course of muscle fiber maturation. In culture, the differential expression of muscle genes is assumed to be solely controlled by intrinsic genetic factors, in the sense that, once precursors cease to proliferate and are committed to become myoblasts, they inevitably progress through terminal differentiation, whatever the environment. The system lacks the necessary elements to proceed towards fiber maturation. Consequently, muscle culture models have, until recently, been limited in studies dealing with the roles played both by genetic and environmental factors in the regulation of muscle gene expression. The accumulating data, however, suggest that under given culture conditions, it is becoming possible to make cells mature beyond embryonic stages and express specific phenotypes in response to extrinsic factors. This paper reviews some of the progress in the development of culture systems which will be useful in studies of muscle plasticity.

Animals↗