bluuebunny/crossref_metadata_2025_split huggingface dataset:
Large-scale normal cell death in the developing rat kidney and its reduction by epidermal growth factor
Authors: Coles Harriet S. R. , Burne Julia F. , Raff Martin C. 
Published: April 2021

ABSTRACT
Although normal cell death is known to occur in many developing vertebrate organs, it has not been thought to play an important part in the development of the mammalian kidney. We show here that normal cell death is found in both the nephrogenic region and medullary papilla of the developing rat kidney and, in each of these areas, it follows a distinct developmental time course. As many as 3% of the cells in these areas have a typical apoptotic morphology and the dead cells seem to be cleared rapidly (within 1-2 hours) by phagocytosis by neighbouring parenchymal cells. These values are similar to those in vertebrate neural tissues where 50% or more of the cells die during normal development, suggesting that large-scale death is a normal feature of kidney development. We also show that in vivo treatment with epidermal growth factor inhibits cell death in the developing kidney, consistent with the possibility that the cells normally die because they lack sufficient survival factors. Our findings suggest that the extent of normal cell death in developing animals is still greatly underestimated and they raise the possibility that many of these cell deaths may reflect limiting amounts of survival factors.
EGF abrogation-induced fusilli-form dysmorphogenesis of Meckel’s cartilage during embryonic mouse mandibular morphogenesis in vitro
Authors: Shum Lillian , Sakakura Yasunori , Bringas Pablo , Luo Wen , Snead Malcolm L. , Mayo Mark , Crohin Constant , Millar Sharon , Werb Zena , Buckley Sue , Hall Fredrick L. , Warburton David , Slavkin Harold C. 
Published: April 2021

ABSTRACT
Mutations associated with genes of the EGF superfamily are implicated in facial malformations arising from abnormal development of the first branchial arch. EGF and EGF receptor (EGFr) transcripts are expressed in the mouse embryonic first branchial arch and derivatives from E9 through E15. EGF transcripts are localized to ectomesenchymal cells associated with precartilage, cartilage, bone and tooth-forming cells. EGF and EGFr proteins co-localize to the same cells suggesting an autocrine regulation. To test whether EGF effects the timing and positional information required for Meckel’s cartilage (MC) and tooth development, we cultured E10 mandibular explants in serumless, chemically defined medium with either antisense or sense EGF oligodeoxynucleotides. Antisense inhibition of EGF expression produces bilaterally symmetrical Fusilli form dysmorphogenesis of MC and decreases tooth bud size; these effects are reversed by the addition of exogenous EGF to the culture medium. Tyrphostin RG 50864, which inhibits EGF receptor kinase activity, inhibits EGF stimulation of tyrosine phosphorylation in a concentration-dependent manner and severely retards mandibular development yet increases tooth size. These findings support the hypothesis that endogenous EGF and EGF-like proteins provide signalling to regulate the size and shape both of cartilage and tooth formation during craniofacial morphogenesis.
Expression of relB transcripts during lymphoid organ development: specific expression in dendritic antigen-presenting cells
Authors: Carrasco Daniel , Ryseck Rolf-Peter , Bravo Rodrigo 
Published: April 2021

ABSTRACT
We have studied the expression of the relB gene during mouse development using in situ hybridization and immunocytochemical analysis. The results show that the expression of the relB gene is highly restricted to a sub-population of cells that colonize the lymphoid tissues and that appear very late during the process of hemapoietic diversification. RNA transcripts of relB are very low or undetectable in early and late embryos. Low relB expression is observed in the thymus at late stages of embryogenesis but rapidly increases after birth. In adult lymphoid tissues, relB is detected in the medullary region of the thymus, the periarterial lymphatic sheaths of the spleen, and the deep cortex of the lymph nodes, which correspond to the regions where T cells of mature phenotype and interdigitating dendritic cells are present. Using double immunofluorescent labeling of thymic cell suspensions, we have identified the interdigitating dendritic cells as the target of RelB expression. These cells are part of a system of antigen-presenting cells that function in the induction of several immune responses, such as, tolerance, sensitization of MHC-restricted T cells, rejection of organ transplants and formation of T-dependent antibodies. Our observations indicate that RelB may play a particular role in the signal transduction pathways that regulate dendritic cell differentiation and its cellular responses.
Cortical cytoplasm, which induces dorsal axis formation in Xenopus, is inactivated by UV irradiation of the oocyte
Authors: Holowacz Tamara , Elinson Richard P. 
Published: April 2021

ABSTRACT
Localized maternal determinants control the formation of dorsal axial structures in Xenopus embryos. To examine the spatial distribution of dorsal determinants, we injected cytoplasm from various regions of the egg and 16-cell embryo into the ventral vegetal cells of a 16-cell recipient embryo. Cortical cytoplasm from the egg vegetal surface induced the formation of a secondary dorsal axis in 53% of recipients. In contrast, animal cortical, equatorial cortical and vegetal deep cytoplasm never induced secondary axis formation. We also compared the axis-inducing ability of animal versus vegetal dorsal cortical cytoplasm from 16-cell embryos. Significantly more dorsalizing activity was found in vegetal dorsal cytoplasm compared to animal dorsal cytoplasm at this stage.
Previous work has shown that UV irradiation of the vegetal surface of either prophase I oocytes, or fertilized eggs, leads to the development of embryos that lack dorsal structures. Egg vegetal cortical cytoplasm was capable of restoring the dorsal axis of 16-cell recipient embryos derived from UV-irradiated oocytes or fertil-ized eggs. We also tested the axis inducing ability of cytoplasm obtained when UV-irradiated oocytes and eggs were treated as donors of cytoplasm. While vegetal cortical cytoplasm from UV-irradiated fertilized eggs retains its dorsalizing activity, cytoplasm obtained from eggs, UV irradiated as oocytes, does not.
The egg vegetal cortex provides a suitable source for the isolation of maternal dorsal determinants. In addition, since UV irradiation of the oocyte vegetal surface destroys the dorsalizing activity of transferred cytoplasm, UV can be used to further restrict possible candidates for such determinants.
FGF-4 regulates expression of Evx-1 in the developing mouse limb
Authors: Niswander Lee , Martin Gail R. 
Published: April 2021

ABSTRACT
We describe here the temporal and spatial pattern of expression of Evx-1, a murine homolog of the Drosophila even-skipped gene, in the developing limb bud. Evx-1 RNA is first detected in distal limb (progress zone) mes-enchyme shortly after the formation of the apical ecto-dermal ridge. The level of Evx-1 RNA increases during the next 24 hours of development, and then decreases in the subsequent 24 hours, such that by the time the ridge regresses Evx-1 RNA is undetectable. At all these stages, Evx-1 RNA is localized primarily to the posterior distal mesenchyme, in the region immediately underlying that portion of the ridge in which the Fgf-4 gene is expressed. Using an in vitro culture system, we show that the ridge is required for both the induction and maintenance of Evx-1 expression in the distal mesenchyme. We also demonstrate that in the absence of the ridge, FGF-4, as well as other FGF proteins, can induce Evx-1 expression in the limb bud. However, this effect appears to be indirect, since it can be blocked by an inhibitor of protein synthesis. Additional studies demonstrate that the effect of FGF-4 on Evx-1 expression is modulated by BMP-2. These data serve to identify Evx-1 as a downstream gene in the FGF signal transduction pathway in the limb.
Heterogeneity in the expression of fibroblast growth factor receptors during limb regeneration in newts (Notophthalmus viridescens)
Authors: Poulin Matthew L. , Patrie Kevin M. , Botelho Mary Jane , Tassava Roy A. , Chiu Ing-Ming 
Published: April 2021

ABSTRACT
Two closely related fibroblast growth factor receptors, FGFR1 and FGFR2, have been cloned from a newt (Notophthalmus viridescens) limb blastema cDNA library. Sequence analysis revealed that we have isolated both the bek and KGFR variants of FGFR2. These two variants differ only in the second half of the last of their three Ig-like domains. The expression patterns of FGFR1 and FGFR2 during limb regeneration have been determined by in situ hybridization. During the preblastema stages of regeneration, FGFR2 expression is observed in the basal layer of the wound epithelium and in the cells of the periosteum. As regeneration progresses to the blastema stages, FGFR2 expression continues to be observed in the basal layer of the wound epithelium with additional hybridization seen in the blastema mesenchyme closely associated with the bisected bones. From the early bud to the mid-bud blastema stage, FGFR1 expression is observed throughout the blastema mesenchyme but, unlike FGFR2, is distinctly absent from the wound epithelium. In the differentiation stages of regeneration, the mesenchymal expression of FGFR2 becomes restricted to the cells of the condensing cartilage and later to the perichondrium. During these later stages of regeneration, the wound epithelium hybridization to the FGFR2 probe is no longer observed. The expression patterns of these receptors suggest that FGFR1 and FGFR2 have distinct roles in limb regeneration, despite their sharing a number of the FGF ligands. Further investigation regarding the potential sources of the FGF ligands will help establish the role that FGFs and FGFRs play in limb regeneration.
CLAVATA1, a regulator of meristem and flower development in Arabidopsis
Authors: Clark Steven E. , Running Mark P. , Meyerowitz Elliot M. 
Published: April 2021

ABSTRACT
We have investigated the effects on plant development of mutations in the Arabidopsis thaliana CLAVATA1 gene. In clavata1 plants, vegetative, inflorescence and floral meristems are all enlarged relative to wild type. The apical meristem can fasciate in the more severe mutant alleles, and this fasciation can occur prior to the transition to flowering. Flowers of clavata1 plants can have increased numbers of organs in all four whorls, and can also have additional whorls not present in wild-type flowers. Double mutant combinations of clavata1 with agamous, apetala2, apetala3 and pistillata indicate that CLAVATA1 controls the underlying floral meristem structure upon which these homeotic genes act. Double mutant combinations of clavata1 with apetala1 and leafy indicate CLAVATA1 plays a role in establishing and maintaining floral meristem identity, in addition to its role in controlling meristem size. In support of this, RNA expression patterns of AGAMOUS and APETALA1 are altered in clavata1 flowers.
Ciliary neurotrophic factor maintains the pluripotentiality of embryonic stem cells
Authors: Conover Joanne C. , Ip Nancy Y. , Poueymirou William T. , Bates Brian , Goldfarb Mitchell P. , DeChiara Thomas M. , Yancopoulos George D. 
Published: April 2021

ABSTRACT
Ciliary neurotrophic factor was discovered based on its ability to support the survival of ciliary neurons, and is now known to act on a variety of neuronal and glial populations. Two distant relatives of ciliary neurotrophic factor, leukemia inhibitory factor and oncostatin M, mimic ciliary neurotrophic factor with respect to its actions on cells of the nervous system. In contrast to ciliary neurotrophic factor, leukemia inhibitory factor and oncostatin M also display a broad array of actions on cells outside of the nervous system. The overlapping activities of leukemia inhibitory factor, oncostatin M and ciliary neurotrophic factor can be attributed to shared receptor components. The specificity of ciliary neurotrophic factor for cells of the nervous system results from the restricted expression of the alpha component of the ciliary neurotrophic factor receptor complex, which is required to convert a functional leukemia inhibitory factor/oncostatin M receptor complex into a ciliary neurotrophic factor receptor complex. The recent observation that the alpha component of the ciliary neurotrophic factor receptor complex is expressed by very early neuronal precursors suggested that ciliary neurotrophic factor may act on even earlier precursors, particularly on cells previously thought to be targets for leukemia inhibitory factor action. Here we show the first example of ciliary neurotrophic factor responsiveness in cells residing outside of the nervous system by demonstrating that embryonic stem cells express a functional ciliary neurotrophic factor receptor complex, and that ciliary neurotrophic factor is similar to leukemia inhibitory factor in its ability to maintain the pluripotentiality of these cells.
Complex fiber-type-specific expression of fast skeletal muscle troponin I gene constructs in transgenic mice
Authors: Hallauer Patricia L. , Bradshaw Holly L. , Hastings Kenneth E. M. 
Published: April 2021

ABSTRACT
We analyzed, in transgenic mice, the cellular expression pattern of the quail fast skeletal muscle troponin I (TnIfast) gene and of a chimeric reporter construct in which quail TnIfast DNA sequences drive expression of E. coli beta-galactosidase ( -gal). Both constructs were actively expressed in skeletal muscle and specifically in fast, as opposed to slow, muscle fibers. Unexpectedly, both constructs showed a marked differential expression among the adult fast fiber subtypes according to the pattern IIB&gt;IIX&gt;IIA. This expression pattern was consistent in multiple lines and differed from the endogenous mouse TnIfast pattern, which shows approximately equal expression in all fast fibers. These observations indicate that distinct regulatory mechanisms contribute to high-level expression of TnIfast in the various fast fiber subtypes and suggest that the outwardly simple pattern of equal expression in all fast fiber types shown by the endogenous mouse TnIfast gene is based on an intricate system of counterbalancing mechanisms. The adult expression pattern of the TnIfast/β-gal construct emerged in a two-stage developmental process. Differential expression in fast versus slow fibers was evident in neonatal animals, although expression in fast fibers was relatively weak and homogeneous. During the first two weeks of postnatal life, expression in maturing IIB fibers was greatly increased whereas that in IIA /IIX fibers remained weak, giving rise to marked differential expression among fast fiber types. Thus at least two serially acting (pre- and post-natal) fiber-type-specific regulatory mechanisms contribute to high-level gene expression in adult fast muscle fibers. Unexpected similarities between TnIfast transgene expression and that of the myosin heavy chain gene family (which includes differentially expressed IIB-, IIX- and IIA-specific members) suggest that similar mechanisms may regulate adult fast muscle gene expression in a variety of unrelated muscle gene families.
Genetic analysis of the floral initiation process (FLIP) in Arabidopsis
Authors: Schultz Elizabeth A. , Haughn George W. 
Published: April 2021

ABSTRACT
Within the Arabidopsis inflorescence, two distinct developmental phases exist. The early inflorescence phase is characterized by nodes bearing coflorescences and leaves, and the late inflorescence phase by nodes bearing flowers. Four genes, TERMINAL FLOWER 1, LEAFY, APETALA1 and APETALA2 are necessary to initiate the switch from formation of early to formation of late inflorescence nodes at the appropriate time. We have investigated the relative roles of these genes in development by isolating and characterizing new alleles of TERMINAL FLOWER 1, LEAFY and APETALA1, and by constructing double mutants to test gene interactions. We suggest that the TERMINAL FLOWER 1 gene product is part of a mechanism that controls the timing of phase-switching in Arabidopsis. We propose that this mechanism involves factor(s) whose activity changes in response to shoot development and environmental variation. TERMINAL FLOWER 1 influences phase transitions in Arabidopsis, and appears to regulate the timing of expression of LEAFY, APETALA1 and APETALA2. LEAFY, APETALA1 and APETALA2 have partially redundant functions in initiating the floral program. In the absence of any one of the three genes, there is a gradual transition from coflorescence to flower-like lateral shoots. This suggests that (1) LEAFY, APETALA1 and APETALA2 are required in combination to ensure that the floral program is initiated rapidly and completely and (2) in the absence of one of the three genes, the others are activated slowly in response to the mechanism controlling timing of phase switching. Besides their role in establishing the floral program, phenotypes of flower-like lateral shoots in mutant inflorescences suggest that all three, LEAFY, APETALA1 and APETALA2, influence expression of whorl identity genes. Loss of LEAFY results in decreased Class B gene expression, as well as altered expression patterns of Class A and Class C genes. In the absence of either APETALA2 or APETALA1, reproductive organs develop in the perianth whorls, suggesting that both genes should be considered Class A organ identity genes, restricting Class C gene expression to inner whorls.
Sex-lethal, master and slave: a hierarchy of germ-line sex determination in Drosophila
Authors: Oliver Brian , Kim Young-Joon , Baker Bruce S. 
Published: April 2021

ABSTRACT
Female sex determination in the germ line of Drosophila melanogaster is regulated by genes functioning in the soma as well as genes that function within the germ line. Genes known or suspected to be involved in germ-line sex determination in Drosophila melanogaster have been examined to determine if they are required upstream or downstream of Sex-lethal+, a known germ-line sex determination gene. Seven genes required for female-specific splicing of germ-line Sex-lethal+ pre-mRNA are identified. These results together with information about the tissues in which these genes function and whether they control sex determination and viability or just sex determination in the germ line have been used to deduce the genetic hierarchy regulating female germ-line sex determination. This hierarchy includes the somatic sex determination genes transformer+, transformer-2+ and doublesex+ (and by inference Sex-lethal+), which control a somatic signal required for female germ-line sex determination, and the germ-line ovarian tumor genes fused+, ovarian tumor+, ovo+, sans fille+, and Sex-lethal+, which are involved in either the reception or interpretation of this somatic sex determination signal. The fused+, ovarian tumor+, ovo+ and sans fille+ genes function upstream of Sex-lethal+ in the germ line.
Ultraviolet irradiation impairs epiboly in zebrafish embryos: evidence for a microtubule-dependent mechanism of epiboly
Authors: Strähle Uwe , Jesuthasan Suresh 
Published: April 2021

ABSTRACT
Early morphogenesis of the teleost embryo is characterized by three orchestrated cell movements. Epiboly leads to spreading of the blastoderm over an uncleaved yolk cell while involution around the blastoderm margin and convergence movements towards the dorsal side generate the mesendodermal inner cell sheet and the axis rudiment, respectively. Irradiation of zebrafish zygotes with ultraviolet light selectively impairs epiboly resulting in embryos with open blastopores but well-formed anterior axes. Gastrulation movements are only marginally affected by ultraviolet irradiation. Involution of marginal cells in epiboly-retarded embryos takes place prior to 50% epiboly and thus appears independent of epiboly. Expression of dorsal and anterior marker genes is unaffected by ultraviolet irradiation.
The ultraviolet light effect is not restricted to the zygote stage as irradiation of later embryonic stages also impairs epiboly. The ultraviolet-sensitive targets may thus be maternally encoded components of the machinery driving epiboly. These targets appear to be microtubules: firstly, irradiated embryos show disorganized and less microtubules in the cytoplasmic layer of the yolk sphere; secondly, the ultraviolet light effect can be mimicked by the microtubule-depolymerising agent nocodazole. We suggest that epiboly is driven, at least partially, by motors that use microtubules radiating from the yolk syncytial layer into the yolk cytoplasmic layer. Together with an observed constrictive behaviour of the blastoderm margin, we propose a two-force model of epiboly: epiboly is initiated and driven by a pulling force dependent on microtubules in the yolk cytoplasmic layer; contraction at the margin operates in addition to aid closure of the blastopore.
Expression of a lacZ transgene reveals floor plate cell morphology and macromolecular transfer to commissural axons
Authors: Campbell Robert M. , Peterson Alan C. 
Published: April 2021

ABSTRACT
The floor plate is situated at the ventral midline of the neural tube and is an important intermediate target for commissural axons. During elongation, these axons converge bilaterally on the ventral midline neural tube and after crossing the floor plate make an abrupt rostral turn. Ample evidence indicates that the initial projection of commissural axons to the floor plate is guided by a chemotropic factor secreted by floor plate cells. However, the way in which the subsequent interaction of these axons with the floor plate leads them to make further trajectory changes remains undefined. In an effort to gain further understanding of the structure and function of floor plate cells, we have taken advantage of a line of transgenic mice in which these cells express galactosidase and thus can be stained by histochemical means. In this line, a genomic imprinting mechanism restricts the expression of the lacZ transgene to only a proportion of the floor plate cells, allowing their morphology to be appreciated with particular clarity. Our analysis revealed that the basal processes of floor plate cells are flattened in their rostrocaudal dimension and possess fine lateral branches which are aligned with commissural axons. Unexpectedly, -galactosidase activity was also detected within longer transverse linear profiles traversing the floor plate whose ultrastructural appearance was not that of floor plate cells but instead corresponded to that of commissural axons. Enzyme activity was not detected in more proximal axonal segments or in the neuronal cell bodies from which these axons originated. Therefore, we propose that the transgene product, and potentially other proteins synthesized by floor plate cells, can be transferred to decussating axons.
pannier, a negative regulator of achaete and scute in Drosophila, encodes a zinc finger protein with homology to the vertebrate transcription factor GATA-1
Authors: Ramain Philippe , Heitzler Pascal , Haenlin Marc , Simpson Pat 
Published: April 2021

ABSTRACT
The gene pannier acts as a repressor of achaete and scute, two transcription factors expressed in discrete subsets of cells at the sites where neural precursors develop. Molecular analysis of mutant alleles revealed the presence of two functional domains within the pannier protein: a zinc finger domain showing homology to the GATA-1 family of vertebrate transcription factors and a domain comprising two putative amphipathic helices. Mutants associated with lesions in the zinc finger domain display an overexpression of achaete and scute and the development of extra neural precursors. Mutant proteins in which the domain including the putative helices is deleted act as hyperactive repressor molecules causing a loss of achaete/scute expression and a loss of neural precursors. Other results suggest that the activity of pannier may be modulated by association with position-specific factors.