bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature-sensitive mutations that arrest Arabidopsis shoot development
Authors: Pickett F. Bryan , Champagne Michele Marino , Meeks-Wagner D. Ry 
Published: April 2021

ABSTRACT
To identify genes involved in meristem function we have designed a screen for temperature-sensitive mutations that cause a conditional arrest of early shoot development in Arabidopsis. We describe the characterization of three mutations, arrested development (add) 1, 2 and 3. At the restrictive temperature the add1 and add2 mutations disrupt apical meristem function as assayed by leaf initiation. Furthermore, add1 and add2 plants exhibit defects in leaf morphogenesis following upshift from permissive to restrictive temperature. This result suggests that proximity to a functional meristem is required for the completion of normal leaf morphogenesis. The add3 mutation does not have a dramatic effect on the production of leaves by the apical meristem; however, add3 prevents the expansion of leaf blades at high temperature.
Thus, in this mutant the temperature-dependent arrest of epicotyl development is due to a failure of normal leaf development rather than new leaf initiation. While all add mutants have a reduced rate of root growth in comparison to wild-type plants, the mutants do not display a temperature-dependent arrest of root development. All add mutants display some developmental defects at low temperature, suggesting that these mutations affect genes involved in inherently temperature-sensitive developmental processes.
eFGF, Xcad3 and Hox genes form a molecular pathway that establishes the anteroposterior axis in Xenopus
Authors: Pownall Mary Elizabeth , Tucker Abigail S. , Slack Jonathan M. W. , Isaacs Harry V. 
Published: April 2021

ABSTRACT
Classical embryological experiments suggest that a posterior signal is required for patterning the developing anteroposterior axis. In this paper, we investigate a potential role for FGF signalling in this process. During normal development, embryonic fibroblast growth factor (eFGF) is expressed in the posterior of the Xenopus embryo. We have previously shown that overexpression of eFGF from the start of gastrulation results in a posteriorised phenotype of reduced head and enlarged proctodaeum. We have now determined the molecular basis of this phenotype and we propose a role for eFGF in normal anteroposterior patterning.
In this study, we show that the overexpression of eFGF causes the up-regulation of a number of posteriorly expressed genes, and prominent among these are Xcad3, a caudal homologue, and the Hox genes, in particular HoxA7. There is both an increase of expression within the normal domains and an extension of expression towards the anterior. Application of eFGF-loaded beads to specific regions of gastrulae reveals that anterior truncations arise from an effect on the developing dorsal axis. Similar anterior truncations are caused by the dorsal overexpression of Xcad3 or HoxA7. This suggests that this aspect of the eFGF overexpression phenotype is caused by the ectopic activation of posterior genes in anterior regions.
Further results using the dominant negative FGF receptor show that the normal expression of posterior Hox genes is dependent on FGF signalling and that this regulation is likely mediated by the activation of Xcad3. The biological activity of eFGF, together with its expression in the posterior of the embryo, make it a good candidate to fulfil the role of the ‘transforming’ activity proposed by Nieuwkoop in his ‘activation and transformation’ model for neural patterning.
Nitric oxide-sensitive guanylate cyclase activity is associated with the maturational phase of neuronal development in insects
Authors: Truman James W. , Vente Jan De , Ball Eldon E. 
Published: April 2021

ABSTRACT
Many developing insect neurones pass through a phase when they respond to nitric oxide (NO) by producing cyclic GMP. Studies on identified grasshopper motoneurones show that this NO sensitivity appears after the growth cone has arrived at its target but before it has started to send out branches. NO sensitivity typically ends as synaptogenesis is nearing completion. Data from interneurones and sensory neurones are also consistent with the hypothesis that NO sensitivity appears as a developing neurone changes from axonal outgrowth to maturation and synaptogenesis. Cyclic GMP likely constitutes part of a retro-grade signalling pathway between a neurone and its synaptic partner. NO sensitivity also appears in some mature neurones at times when they may be undergoing synaptic rearrangement. Comparative studies on other insects indicate that the association between an NO- sensitive guanylate cyclase and synaptogenesis is an ancient one, as evidenced by its presence in both ancient and more recently evolved insect groups.
Joint patterning defects caused by single and double mutations in members of the bone morphogenetic protein (BMP) family
Authors: Storm Elaine E. , Kingsley David M. 
Published: April 2021

ABSTRACT
The mouse brachypodism locus encodes a bone morphogenetic protein (BMP)-like molecule called growth/differentiation factor 5 (GDF5). Here we show that Gdf5 transcripts are expressed in a striking pattern of transverse stripes within many skeletal precursors in the developing limb. The number, location and time of appearance of these stripes corresponds to the sites where joints will later form between skeletal elements. Null mutations in Gdf5 disrupt the formation of more than 30% of the synovial joints in the limb, leading to complete or partial fusions between particular skeletal elements, and changes in the patterns of repeating structures in the digits, wrists and ankles. Mice carrying null mutations in both Gdf5 and another BMP family member, Bmp5, show additional abnormalities not observed in either of the single mutants. These defects include disruption of the sternebrae within the sternum and abnormal formation of the fibrocartilaginous joints between the sternebrae and ribs. Previous studies have shown that members of the BMP family are required for normal development of cartilage and bone. The current studies suggest that particular BMP family members may also play an essential role in the segmentation process that cleaves skeletal precursors into separate elements. This process helps determine the number of elements in repeating series in both limbs and sternum, and is required for normal generation of the functional articulations between many adjacent structures in the vertebrate skeleton.
Quantitative functional interrelations within the cis-regulatory system of the S. purpuratus Endo16 gene
Authors: Yuh Chiou-Hwa , Moore James G. , Davidson Eric H. 
Published: April 2021

ABSTRACT
Embryonic expression of the Endo16 gene of Strongylo-centrotus purpuratus is controlled by interactions with at least 13 different DNA-binding factors. These interactions occur within a cis-regulatory domain that extends about 2300 bp upstream from the transcription start site. A recent functional characterization of this domain reveals six different subregions, or cis-regulatory modules, each of which displays a specific regulatory subfunction when linked with the basal promoter and in some cases various other modules (C.-H. Yuh and E. Davidson (1996) Development 122, 1069-1082). In the present work, we analyzed quantitative time-course measurements of the CAT enzyme output of embryos bearing expression constructs controlled by various Endo16 regulatory modules, either singly or in combination. Three of these modules function positively in that, in isolation, each is capable of promoting expression in vegetal plate and adjacent cell lineages, though with different temporal profiles of activity. Models for the mode of interaction of the three positive modules with one another were tested by assuming mathematical relations that would generate, from the measured single module time courses, the experimentally observed profiles of activity obtained when the relevant modules are physically linked in the same construct. The generated and observed time functions were compared, and the differences were minimized by least squares adjustment of a scale parameter. When the modules were tested in context of the endogenous promoter region, one of the positive modules (A) was found to increase the output of the others (B and G), by a constant factor. In contrast, a solution in which the time-course data of modules A and B are multiplied by one another was required for the interrelations of the positive modules when a minimal SV40 promoter was used. One interpretation is that, in this construct, each module independently stimulates the basal transcription complex. We used a similar approach to analyze the repressive activity of the three Endo16 cis-regulatory modules that act negatively in controlling spatial expression. The evidence obtained confirms that the repressive modules act only by affecting the output of module A (C.-H. Yuh and E. Davidson (1996) Development 122, 1069-1082). A new hierarchical model of the cis-regulatory system was formulated in which module A plays a central integrating role, and which also implies specific functions for certain DNA-binding sites within the basal promoter fragment of the gene. Additional kinetic experiments were then carried out, and key aspects of the model were confirmed.
Gonadal sex reversal of the developing marsupial ovary in vivo and in vitro
Authors: Whitworth Deanne J. , Shaw Geoffrey , Renfree Marilyn B. 
Published: April 2021

ABSTRACT
Undifferentiated tammar wallaby ovaries were transplanted under the skin of male pouch young during the period of mitotic division of the XX germ cells. After 25 days, all the germ cells had disappeared and the ovaries contained seminiferous-like cords. Similarly, undifferentiated ovaries cultured for 4 days with recombinant human Müllerian-inhibiting substance (rhMIS) also contained well-differentiated seminiferous-like cords and few or no surviving germ cells. The majority of controls cultured without rhMIS developed as normal ovaries. However, in a few control ovaries seminiferous-like cords developed in those regions of the ovaries that were partially necrotic and contained few germ cells. These results strongly suggest that sex-reversal of the tammar ovary is the direct result of loss of mitotic germ cells, rather than an effect of MIS on female somatic cells. MIS is apparently toxic to these female germ cells in mitosis, but not to male germ cells in mitosis. Thus, in normal development in the tammar, the presence of XX germ cells in the ovary inhibits the formation of seminiferous cords so that the gonad develops as an ovary.
Spinal cord oligodendrocytes develop from ventrally derived progenitor cells that express PDGF alpha-receptors
Authors: Hall Anita , Giese Neill A. , Richardson William D. 
Published: April 2021

ABSTRACT
Platelet-derived growth factor alpha-receptors (PDGFRα) are expressed by a subset of neuroepithelial cells in the ventral half of the embryonic day 14 (E14) rat spinal cord. The progeny of these cells subsequently proliferate and migrate into the dorsal parts of the cord after E16. Here, we show that E14 ventral cells are able to generate oligodendrocytes in culture but that dorsal cells acquire this ability only after E16, coinciding with the appearance of PDGFRα-immunoreactive cells in the starting population. PDGFRα-positive cells in optic nerve and spinal cord cultures co-labelled with antibody markers of oligodendrocyte progenitors. When PDGFRα-positive cells were purified from embryonic rat spinal cords by immunoselection and cultured in defined medium, they all differentiated into oligodendrocytes. Very few oligodendrocytes developed in cultures of embryonic spinal cord cells that had been depleted of PDGFRα-expressing cells by antibody-mediated complement lysis. These data demonstrate that all PDGFRα-positive cells in the embryonic rat spinal cord are oligodendrocyte progenitors and that most or all early-developing oligodendrocytes are derived from these ventrally-derived precursors.
Conditioned medium from a rat ureteric bud cell line in combination with bFGF induces complete differentiation of isolated metanephric mesenchyme
Authors: Karavanova Irina D. , Dove Lee F. , Resau James H. , Perantoni Alan O. 
Published: April 2021

ABSTRACT
Differentiation of metanephric mesenchyme is triggered by an inductive signal(s) from the epithelial ureteric bud. As a result of this induction, most of the metanephric mesenchyme converts into epithelium of a nephron. We have developed and characterized an explant culture system, in which metanephric mesenchyme can grow and completely differentiate in vitro in the absence of an inductive tissue. When separated 13 dpc rat metanephric mesenchymes were cultured in serum-free conditioned medium from a rat ureteric bud cell line (RUB1) in the presence of bFGF and TGFα, they were induced to differentiate into nephron epithelia and glomeruli-like structures. The nephric type of differentiation was confirmed by both morphological and molecular criteria and paralleled the developmental changes of nephron differentiation in vivo. Expression patterns of brush-border antigen as well as molecular markers of kidney differentiation Wt1, Lim1, Hgf and c-met, c-ret, Shh, Wnt4, Wnt7b, and Wnt11 were analyzed in explants by whole mount and tissue section in situ hybridization following 1-9 days in culture. The expression of secreted patterning molecules Bmp7 and Wnt7b, but not Shh or Wnt11, were demonstrated by RT-PCR and northern blot hybridization with RNA from the RUB1 cells. Our culture system lends itself to examining the relevance of these and other signaling molecules required for nephron differentiation.
Cardiotrophin-1 displays early expression in the murine heart tube and promotes cardiac myocyte survivals
Authors: Sheng Zelin , Pennica Diane , Wood William I. , Chien Kenneth R. 
Published: April 2021

ABSTRACT
We have recently isolated a novel cytokine, cardiotrophin-1 (CT-1), from an in vitro embryonic stem cell system of cardiogenesis that can activate embryonic markers in neonatal rat cardiac myocytes. CT-1 is a new member of the interleukin 6 (IL-6)/leukemia inhibitory factor (LIF) cytokines, which activate downstream signals via gp130-dependent pathways. To define the developmental pattern of expression of CT-1 during murine embryogenesis, we have developed antibodies directed against a CT-1 fusion protein. As assessed by immunolocalization, CT-1 is pre-dominantly expressed in the early mouse embryonic heart tube (E8.5-10.5). In the heart, CT-1 is primarily expressed in myocardial cells, and not in endocardial cushion or outflow tract tissues. After E12.5, CT-1 expression is found in other tissues, including skeletal, liver and dorsal root ganglia. Given the effects of a related family member (ciliary neurotrophic factor, CNTF) on neuronal cell survival, we studied the ability of CT-1 to promote cardiac myocyte survival and proliferation in vitro. Both CT-1 and LIF, which share the same receptors, dramatically promote neonatal cardiac myocyte survival, while IL-6 and CNTF are without effect. A cell proliferation assay documents that CT-1 provokes an approximate 2-fold increase in embryonic cardiac myocyte proliferation. Thus, CT-1 may play an autocrine role during cardiac chamber growth and morphogenesis by promoting the survival and proliferation of immature myocytes, most likely via gp130-dependent signaling pathways.
Regulative interactions in zebrafish neural crest
Authors: Raible David W. , Eisen Judith S. 
Published: April 2021

ABSTRACT
Zebrafish trunk neural crest cells that migrate at different times have different fates: early-migrating crest cells produce dorsal root ganglion neurons as well as glia and pigment cells, while late-migrating crest cells produce only non-neuronal derivatives. When presumptive early-migrating crest cells were individually transplanted into hosts such that they migrated late, they retained the ability to generate neurons. In contrast, late-migrating crest cells transplanted under the same conditions never generated neurons. These results suggest that, prior to migration, neural crest cells have intrinsic biases in the types of derivatives they will produce. Transplantation of presumptive early-migrating crest cells does not result in production of dorsal root ganglion neurons under all conditions, suggesting that these cells require appropriate environmental factors to express these intrinsic biases. When earlymigrating crest cells are ablated, late-migrating crest cells gain the ability to produce neurons, even when they migrate on their normal schedule. Interactions among neural crest cells may thus regulate the types of derivatives neural crest cells produce, by establishing or maintaining intrinsic differences between individual cells.
A comparison of the properties of Sox-3 with Sry and two related genes, Sox-1 and Sox-2
Authors: Collignon Jérôme , Sockanathan Shanthini , Hacker Adam , Cohen-Tannoudji Michel , Norris Dominic , Rastan Sohaila , Stevanovic Milena , Goodfellow Peter N. , Lovell-Badge Robin 
Published: April 2021

ABSTRACT
The Sox gene family consists of a large number of embryonically expressed genes related via the possession of a 79-amino-acid DNA-binding domain known as the HMG box. Partial clones for the first three Sox genes (a1-a3) were isolated by homology to the HMG box of the testis-determining gene Sry and are now termed Sox-1, Sox-2 and Sox-3. Sox-3 is highly conserved amongst mammalian species and is located on the X chromosome. This has led to the proposal that Sry evolved from Sox-3. We present the cloning and sequencing of Sox-1, Sox-2 and Sox-3 from the mouse and show that Sox-3 is most closely related to Sry. We also confirm that mouse Sox-3 is located on the X chromosome between Hprt and Dmd. Analysis of the distribution of Sox-3 RNA shows that its main site of expression is in the developing central nervous system, suggesting a role for Sox-3 in neural development. Moreover, we demonstrate that Sox-3, as well as Sox-1 and Sox-2, are expressed in the urogenital ridge and that their protein products are able to bind the same DNA sequence motif as Sry in vitro, but with different affinities. These observations prompt discussion of an evolutionary link between the genes and support the model that Sry has evolved from Sox-3. However our findings imply that if this is true, then Sry has undergone concomitant changes resulting in loss of CNS expression and altered DNA-binding properties.
Origin of the c-kit-positive interstitial cells in the avian bowel
Authors: Lecoin Laure , Gabella Giorgio , Douarin Nicole Le 
Published: April 2021

ABSTRACT
Interstitial cells of Cajal (ICC) aroused much interest among neuroanatomists at the beginning of the century. These small cells, organized into networks, are intercalated between nerve fibers and muscle cells, and are now considered by many authors to be responsible for the pacemaker activity of the gut. Renewed interest in these cells arose recently when the receptor tyrosine kinase, ckit, was shown to be associated with their functional activity. The embryonic origin of interstitial cells has remained a controversial issue ever since their discovery. Some authors consider them to be of neural or glial nature and thus of neural crest origin. Others consider them to be of fibroblastic or muscular nature. We have applied the quail-chick marker system to solve this problem. ICC were identified by means of a chicken-c-kit nucleic probe which cross-reacts with the quail c-kit gene product. We constructed chimeric bowels by grafting isotopically quail vagal neural crest into chick embryos at embryonic day 2 (E2). The enteric innervation of the chimeras was then of quail origin. In situ hybridization on the chimeric bowels showed that all the c-kit-positive cells were of the chick type, and therefore belonged to the gut mesenchyme and were not neural crest-derived cells. This observation was confirmed by culturing aneural chick guts on the chorioallantoic membrane. Typical ICC, as defined at the EM level and by their expression of the c-kit receptor, developed in the gut wall in the complete absence of enteric innervation. One can conclude that ICC are of mesodermal origin and develop independently from enteric neurons with which they later establish anatomical and functional relations.
The initiation of basal disc formation in Dictyostelium discoideum is an early event in culmination
Authors: Jermyn Keith , Traynor David , Williams Jeffrey 
Published: April 2021

ABSTRACT
We have analysed expression of the ecmA and ecmB genes of Dictyostelium by enzymatic double staining using βgalactosidase and β-glucuronidase reporter gene constructs. Cells expressing the ecmA gene first appear as scattered cells at the mound stage of development and we show that this is also true for cells expressing the ecmB gene. During tip formation the ecmA-expressing cells move to the apex of the mound, while the ecmB-expressing cells accumulate in the base. The ecmB-expressing cells constitute part of the basal disc if the culminant is formed in situ but are discarded if a migratory slug is formed. During slug migration they are replaced by a band of ecmB-expressing cells, situated in the front half of the prespore zone and tightly apposed to the substratum. When culmination is triggered these cells rapidly move to the back half of the prestalk zone, possibly acting as a point of attachment to the subtratum. Ultimately, they are joined by cells at the back of the slug, the rearguard cells, to form the basal disc. Thus, contrary to previous belief, basal disc formation is initiated very early during culmination and occurs by the forward movement of cells located in the anterior of the prespore zone.
In vitro analysis of epiblast tissue potency for hematopoietic cell differentiation
Authors: Kanatsu Mito , Nishikawa Shin-Ichi 
Published: April 2021

ABSTRACT
In murine embryogenesis, all cells that will constitute the embryonic structures originate from the epiblast (primitive ectoderm) tissue, the epithelial cell sheet of the gastrulating embryo. The cells of this tissue are totipotent at the beginning of gastrulation, but at the end of this period are specified to particular cell lineages. Thus, it is likely that during murine gastrulation, the potency of epiblast cells that were originally totipotent becomes restricted as development progresses. However, the mechanisms of this process are unknown.
We have investigated this process in vitro, focusing on the hematopoietic cell lineage. To detect the hematogenic potency of the epiblast tissue, we established an in vitro culture system in which the hematopoietic cell differentiation of the epiblast tissue was supported by a stromal cell layer. With this culture system, we investigated the process by which this potency becomes spatially and temporally restricted during gastrulation. The results showed that hematogenic potency resides in the entire epiblast of the earlyto mid-gastrulating embryo, but becomes restricted to the posterior half of the epiblast at the headfold stage. Furthermore, we showed that this process is altered by exogenous bone morphogenetic protein-4 (BMP-4) or activin A, which may be mesoderm inducers in Xenopus embryogenesis.