Home About us Contact
|
Home About us Contact | ||
|
|
||
Developmental Control (developmental + control)
Selected AbstractsDevelopmental control via GATA factor interplay at chromatin domainsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2005Emery H. Bresnick Despite the extraordinary task of packaging mammalian DNA within the constraints of a cell nucleus, individual genes assemble into cell type-specific chromatin structures with high fidelity. This chromatin architecture is a crucial determinant of gene expression signatures that distinguish specific cell types. Whereas extensive progress has been made on defining biochemical and molecular mechanisms of chromatin modification and remodeling, many questions remain unanswered about how cell type-specific chromatin domains assemble and are regulated. This mini-review will discuss emerging studies on how interplay among members of the GATA family of transcription factors establishes and regulates chromatin domains. Dissecting mechanisms underlying the function of hematopoietic GATA factors has revealed fundamental insights into the control of blood cell development from hematopoietic stem cells and the etiology of pathological states in which hematopoiesis is perturbed. © 2005 Wiley-Liss, Inc. [source] Developmental control of inositol phosphate biosynthesis is altered in the brain of both curly and phenotypically normal straight tail mutant mice,BIRTH DEFECTS RESEARCH, Issue 10 2009Hana Dawood Ali Alebous Abstract BACKGROUND: Altered levels of inositol phosphate in the central nervous system (CNS) are hypothesized to produce distorted brain signaling and lead to numerous neurologic maladies. Little is known of mechanisms controlling the complex metabolic flux of inositol phosphate. Less is known of controls that regulate inositol-phosphate biosynthesis in the mammalian brain. The expression of 1L-myo-inositol,1 phosphate synthase (MIP), the only enzyme known to synthesize inositol phosphate, was studied in the brain of normal (CBA) and curly tail (CT) mutant mice. The CT strain exhibits a neural tube defect, spina bifida, responsive to inositol supplementation, but not to folic acid treatment. METHODS: Utilizing enzyme assays to determine the specific activity of MIP, Western blotting to detect expression, gas chromatography/mass spectrometry to measure inositol concentration, and statistical analyses to evaluate quantitative data, MIP expression was analyzed in newborn, young, and adult brains of CBA and CT (curly tail [ct-CT] and straight tail [st-CT]) mutant mice. RESULTS: Data analyses suggest there is a significant difference in MIP activity in the brain of CBA mice as compared to that of CT mutant mice and that temporal and spatial control of MIP expression and inositol concentrations are altered in the brain of both the ct-CT and phenotypically normal st-CT mutant. Moreover, two differentially expressed forms of MIP were identified in the adult mouse brain. CONCLUSIONS: These findings implicate a role for MIP in the maturation of the CNS and evoke a hypothesis regarding the regulation of inositol phosphate biosynthesis in brain development. Birth Defects Research (Part A), 2009. © 2009 Wiley-Liss, Inc. [source] Regulation of miRNA expression during neural cell specificationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2005Lena Smirnova Abstract MicroRNA (miRNA) are a newly recognized class of small, noncoding RNA molecules that participate in the developmental control of gene expression. We have studied the regulation of a set of highly expressed neural miRNA during mouse brain development. Temporal control is a characteristic of miRNA regulation in C. elegans and Drosophila, and is also prominent in the embryonic brain. We observed significant differences in the onset and magnitude of induction for individual miRNAs. Comparing expression in cultures of embryonic neurons and astrocytes we found marked lineage specificity for each of the miRNA in our study. Two of the most highly expressed miRNA in adult brain were preferentially expressed in neurons (mir-124, mir-128). In contrast, mir-23, a miRNA previously implicated in neural specification, was restricted to astrocytes. mir-26 and mir-29 were more strongly expressed in astrocytes than neurons, others were more evenly distributed (mir-9, mir-125). Lineage specificity was further explored using reporter constructs for two miRNA of particular interest (mir-125 and mir-128). miRNA-mediated suppression of both reporters was observed after transfection of the reporters into neurons but not astrocytes. miRNA were strongly induced during neural differentiation of embryonic stem cells, suggesting the validity of the stem cell model for studying miRNA regulation in neural development. [source] Duplicated P5CS genes of Arabidopsis play distinct roles in stress regulation and developmental control of proline biosynthesisTHE PLANT JOURNAL, Issue 1 2008Gyöngyi Székely Summary ,-1-pyrroline-5-carboxylate synthetase enzymes, which catalyse the rate-limiting step of proline biosynthesis, are encoded by two closely related P5CS genes in Arabidopsis. Transcription of the P5CS genes is differentially regulated by drought, salinity and abscisic acid, suggesting that these genes play specific roles in the control of proline biosynthesis. Here we describe the genetic characterization of p5cs insertion mutants, which indicates that P5CS1 is required for proline accumulation under osmotic stress. Knockout mutations of P5CS1 result in the reduction of stress-induced proline synthesis, hypersensitivity to salt stress, and accumulation of reactive oxygen species. By contrast, p5cs2 mutations cause embryo abortion during late stages of seed development. The desiccation sensitivity of p5cs2 embryos does not reflect differential control of transcription, as both P5CS mRNAs are detectable throughout embryonic development. Cellular localization studies with P5CS,GFP gene fusions indicate that P5CS1 is sequestered into subcellular bodies in embryonic cells, where P5CS2 is dominantly cytoplasmic. Although proline feeding rescues the viability of mutant embryos, p5cs2 seedlings undergo aberrant development and fail to produce fertile plants even when grown on proline. In seedlings, specific expression of P5CS2,GFP is seen in leaf primordia where P5CS1,GFP levels are very low, and P5CS2,GFP also shows a distinct cell-type-specific and subcellular localization pattern compared to P5CS1,GFP in root tips, leaves and flower organs. These data demonstrate that the Arabidopsis P5CS enzymes perform non-redundant functions, and that P5CS1 is insufficient for compensation of developmental defects caused by inactivation of P5CS2. [source] The modulator is a constitutive enhancer of a developmentally regulated sea urchin histone H2A geneBIOESSAYS, Issue 9 2002Giovanni Spinelli Going back to the late 1970s and early 1980s, we trace the Xenopus oocyte microinjection experiments that led to the emergence of the concept of "modulator". The finding that the modulator could transactivate transcription from far upstream and in either orientation suggested that a new genetic element, different from the classical prokaryotic promoter sequences, had been discovered. This particular enhancer transactivates transcription of the sea urchin early (,) histone H2A gene which is regulated in early sea urchin development. We summarise the data from sea urchin microinjection experiments that confirm and extend the results obtained with Xenopus oocytes. We conclude that the H2A enhancer is bipartite, is located approx. 100 bp upstream of the TATAAATA box in the H2A gene of two sea urchin species and enhances transcription when placed at a position far upstream or far downstream of the gene unless an insulator intervenes between enhancer and promoter. Evidence from microinjection experiments with sea urchin embryos suggests that the developmental control of H2A expression resides not with the enhancer, which is constitutively active, but with a striking chromatin structure with two positioned nucleosomes near the 3, end of the gene. Within this structure, there is an insulator element. BioEssays 24:850,857, 2002. © 2002 Wiley Periodicals, Inc. [source] Environmental and developmental controls on specific leaf area are little modified by leaf allometryFUNCTIONAL ECOLOGY, Issue 4 2008R. Milla Summary 1Recent work shows that large leaves tend to require higher biomass investments per unit leaf area than small leaves. As a consequence, specific leaf area (SLA), which is a focus trait for a bulk of physiological and ecological research programs, is dependent on leaf size variation. Here, we address whether size dependency alters the outcome of research dealing with SLA responses to environmental or developmental change. 2We compiled lamina mass (M) and surface area (A) data for 2158 leaves of 26 species, coming from studies investigating the reaction of SLA to variation in rainfall, growth,season length, light intensity, atmospheric CO2, fire frequency, type of branch and leaf and plant age. We fitted the function M = a Ab to the data of each experimental situation separately, and implemented a method to split SLA response as measured in the original study (SLADm) into response due to leaf size dependency (SLADa), and response due to treatment effects, after controlling for leaf size dependency (SLADt). 3The sign of the reaction did not differ between SLADm and SLADt. However, the magnitude of that response changed for most contrasts, though in variable ways. 4Conclusions of past experiments hold, for the most part, after re-analysis including size dependency. However, given the large heterogeneity found here, we advise that future work investigating SLA be prepared to account for leaf size dependency when the factors under focus are suspected to alter leaf size. [source] Carbon limitation in treesJOURNAL OF ECOLOGY, Issue 1 2003Christian Körner Summary 1The ongoing enrichment of the atmosphere with CO2 raises the question of whether growth of forest trees, which represent close to 90% of the global biomass carbon, is still carbon limited at current concentrations of close to 370 p.p.m. As photosynthesis of C3 plants is not CO2 -saturated at such concentrations, enhanced ,source activity' of leaves could stimulate ,sink activity' (i.e. growth) of plants, provided other resources and developmental controls permit. I explore current levels of non-structural carbon in trees in natural forests in order to estimate the potential for a carbon-driven stimulation of growth. 2The concentration of non-structural carbohydrates (NSC) in tree tissues is considered a measure of carbon shortage or surplus for growth. A periodic reduction of NSC pools indicates either that carbon demand exceeds con-current supply, or that both source and sink activity are low. A steady, very high NSC concentration is likely to indicate that photosynthesis fully meets, or even exeeds, that needed for growth (surplus assimilates accumulate). 3The analysis presented here considers data for mature trees in four climatic zones: the high elevation treeline (in Mexico, the Alps and Northern Sweden), a temperate lowland forest of central Europe, Mediterranean sclerophyllous woodland and a semideciduous tropical forest in Panama. 4In all four climatic regions, periods of reduced or zero growth show maximum C-loading of trees (source activity exceeding demand), except for dry midsummer in the Mediterranean. NSC pools are generally high throughout the year, and are not significantly affected by mass fruiting episodes. 5It is concluded that, irrespective of the reason for its periodic cessation, growth does not seem to be limited by carbon supply. Instead, in all the cases examined, sink activity and its direct control by the environment or developmental constraints, restricts biomass production of trees under current ambient CO2 concentrations. 6The current carbohydrate charging of mature wild trees from the tropics to the cold limit of tree growth suggests that little (if any) leeway exists for further CO2 -fertilization effects on growth. [source] Placoderm fishes, pharyngeal denticles, and the vertebrate dentitionJOURNAL OF MORPHOLOGY, Issue 3 2003Zerina Johanson Abstract The correlation of the origin of teeth with jaws in vertebrate history has recently been challenged with an alternative to the canonical view of teeth deriving from separate skin denticles. This alternative proposes that organized denticle whorls on the pharyngeal (gill) arches in the fossil jawless fish Loganellia are precursors to tooth families developing from a dental lamina along the jaw, such as those occurring in sharks, acanthodians, and bony fishes. This not only indicates that homologs of tooth families were present, but also illustrates that they possessed the relevant developmental controls, prior to the evolution of jaws. However, in the Placodermi, a phylogenetically basal group of jawed fishes, the state of pharyngeal denticles is poorly known, tooth whorls are absent, and the presence of teeth homologous to those in extant jawed fishes (Chondrichthyes + Osteichthyes) is controversial. Thus, placoderms would seem to provide little evidence for the early evolution of dentitions, or of denticle whorls, or tooth families, at the base of the clade of jawed fishes. However, organized denticles do occur at the rear of the placoderm gill chamber, but are associated with the postbranchial lamina of the anterior trunkshield, assumed to be part of the dermal cover. Significantly, these denticles have a different organization and morphology relative to the external dermal trunkshield tubercles. We propose that they represent a denticulate part of the visceral skeleton, under the influence of pharyngeal patterning controls comparable to those for pharyngeal denticles in other jawed vertebrates and Loganellia. J. Morphol. 257:289,307, 2003. © 2003 Wiley-Liss, Inc. [source] | ||||||||||