bluuebunny/crossref_metadata_2025_split huggingface dataset:
Localized and inducible expression of Xenopus-posterior (Xpo), a novel gene active in early frog embryos, encoding a protein with a ‘CCHC’ finger domain
Authors: Sato Sheryl M. , Sargent Thomas D. 
Published: April 2021

ABSTRACT
Xenopus-posterior (Xpo) is a gene that is activated at or shortly after the midblastula transition (MBT). The RNA accumulates to a relatively low level, which remains constant until gastrulation, then rapidly and transiently increases in posterior ectoderm and mesoderm. A single copy of a putative finger motif, of the ‘CCHC’ type, is located near the carboxyl terminus. One or two copies of similar sequence motifs are found in the nucleocapsid protein of retroviruses where they are involved in protein-RNA interactions, and in cellular nucleic acid binding protein (CNBP), a protein that binds to the sterol regulatory element. Xpo expression is induced in ectodermal expiants by treatment with basic fibroblast growth factor (bFGF) and with polypeptide growth factors found in medium conditioned by the Xenopus XTC cell line (XTC-CM). Taken together, these properties suggest a possible role for Xpo in the organization of the anteroposterior axis during development.
Gastrulation in Drosophila: the formation of the ventral furrow and posterior midgut invaginations
Authors: Sweeton Dari , Parks Suki , Costa Michael , Wieschaus Eric 
Published: April 2021

ABSTRACT
The ventral furrow and posterior midgut invaginations bring mesodermal and endodermal precursor cells into the interior of the Drosophila embryo during gastrulation. Both invaginations proceed through a similar sequence of rapid cell shape changes, which include apical flattening, constriction of the apical diameter, cell elongation and subsequent shortening. Based on the time course of apical constriction in the ventral furrow and posterior midgut, we identify two phases in this process: first, a slow stochastic phase in which some individual cells begin to constrict and, second, a rapid phase in which the remaining unconstricted cells constrict. Mutations in the concertina or folded gastrulation genes appear to block the transition to the second phase in both the ventral furrow and the posterior midgut invaginations.
The L5 epitope: an early marker for neural induction in the chick embryo and its involvement in inductive interactions
Authors: Roberts Catherine , Platt Nicholas , Streit Andrea , Schachner Melitta , Stern Claudio D. 
Published: April 2021

ABSTRACT
The pattern of expression of the carbohydrate epitope L5 was studied during early development of the chick neuroepithelium. Immunoreactivity first appears during gastrulation, at mid-primitive streak stage, and persists until at least 3.5 days of development. The epitope is expressed on all the components of the developing nervous system, both central and peripheral. In immunoblots, the antibody recognises a major component of about Mr 500000 and several more minor components of lower molecular mass.
If a Hensen’s node from a donor embryo is transplanted into the area opaca of a host embryo, L5 immunoreactivity appears in the epiblast surrounding the graft. If hybridoma cells secreting the antibody are grafted together with Hensen’s node into a host chick embryo, the induction of a supernumerary nervous system is inhibited. We suggest that the L5 epitope is an early and general marker for neural induction and that it may be involved directly in inductive interactions.
Pleiotropic effect of okadaic acid on maturing mouse oocytes
Authors: Alexandre H. , Van Cauwenberge A. , Tsukitani Y. , Mulnard J. 
Published: April 2021

ABSTRACT
Okadaic acid (OA), a potent inhibitor of types 1 and 2A protein phosphatases, was shown recently to induce chromatin condensation and germinal vesicle breakdown (GVBD) in mouse oocytes arrested at the dictyate stage by dibutyryl cAMP (dbcAMP), isobutyl methylxanthine (IBMX) and 12,13-phorbol dibutyrate (PDBu). We confirm these results using IBMX and another phorbol diester, 12-O-tetradecanoylphorbol-13-acetate (TPA) and show that OA also bypasses the inhibitory effect of 6-dimethylaminopurine (6-DMAP). It has been concluded that protein phosphatases 1 and/or 2A (PP1, 2A), involved in the negative control of MPF activation, are thus operating downstream from both the protein kinase A and protein kinase C catalysed phosphorylation steps that prevent the breakdown of GV. Similar enzymatic activities are also able to counteract the general inhibition of protein phosphorylation.
However, PP1 and/or PP2A are positively involved in the activation of pericentriolar material (PCM) into microtubule organizing centres (MTOCs). This explains the inhibitory effect of OA on spindle assembly.
Finally, OA interferes with the integrity and/or function of actomyosin filaments. This results in a dramatic ruffling of the plasma membrane leading to the internalization of large vacuoles, the inhibition of chromosome centrifugal displacement and, consequently, the prevention of polar body extrusion.
Patterns of E74A RNA and protein expression at the onset of metamorphosis in Drosophila
Authors: Boyd Lynn , O’Toole Erin , Thummel Carl S. 
Published: April 2021

ABSTRACT
Metamorphosis in Drosophila is triggered by a pulse of the steroid hormone ecdysone at the end of larval development. Ecdysone initiates a genetic hierarchy that can be visualized as a series of puffs in the larval salivary gland polytene chromosomes. The E74 gene is responsible for the early ecdysone-inducible puff at position 74EF and encodes two related DNA-binding proteins which appear to play a regulatory role in the hierarchy. Here we describe the spatial and temporal patterns of E74A RNA and protein expression at the onset of metamorphosis. We use in situ hybridization, antibody stains, and western and northern blot analyses to follow E74A expression from its initial appearance as nascent transcripts on the polytene chromosomes, to spliced mRNA, to post-translationally modified nuclear E74A protein. E74A is expressed in a wide variety of late-third instar tissues, suggesting that it plays a broad pleiotropic role in response to the hormone. In early prepupae, when the overall levels of E74A mRNA are decreasing, relatively high levels of E74A RNA persist in the gut, peripodial membranes of the imaginai discs, and proliferation centers of the brain. The spatial distribution of nuclear E74A protein correlates with the RNA distribution with the single exception that no E74A protein can be detected in the proliferation centers of the brain. There is also a temporal discrepancy between E74A mRNA and protein accumulation. The peak of E74A protein induced by the late larval ecdysone pulse follows the peak of E74A mRNA by ∼2h. This delay is not seen in 10 h prepupae, when the next pulse of ecdysone induces the simultaneous expression of E74A mRNA and protein. We discuss possible mechanisms for post-transcriptional regulation of E74A expression and suggest that the unusually long and complex 5′ leader in the E74A mRNA may regulate its translation.
‘Promoter trapping’ in Caenorhabditis elegans
Authors: Hope I. A. 
Published: April 2021

ABSTRACT
A screen of gene expression patterns has been developed for the nematode Caenorhabditis elegans. Promoterreporter gene fusions were constructed in vitro by ligating C.elegans genomic DNA fragments upstream of a lacZ gene. Patterns of β-galactosidase expression were examined by histochemical staining of C. elegans lines transformed with the constructs, β-galactosidase expression depended on translational fusion, so constructs were assayed in large pools to expedite detection of the low proportion that were active. Expression in a variety of cell types and temporal patterns was observed with different construct pools. The most striking expression patterns were obtained when the β-galactosidase activity was localized to subcellular structures by the C. elegans portion of the fusion protein. The active constructs of three selected pools were identified subsequently by an efficient combinatorial procedure. The genomic locations of the DNA fragments from the active constructs were determined and appear to define previously uncharacterized genetic loci.
Fate maps of the first quartet micromeres in the gastropod llyanassa obsoleta
Authors: Render Joann 
Published: April 2021

ABSTRACT
Cell fate specification in the gastropod mollusc Ilyanassa obsoleta involves both cell autonomous and inductive mechanisms, which depend on determinants localized first in the polar lobe and then in the D quadrant of the embryo. A complete cell lineage is lacking for this embryo and is essential for a critical interpretation of previous experimental results and an analysis of the mechanisms at the molecular level.
Lineages of the first quartet micromeres were followed using Lucifer Yellow dextran as a tracer. The tracer was injected into individual first quartet micromeres using iontophoresis and patterns of fluorescence were analyzed in the larva after 8 days of development. Fluorescence was limited to head structures, including eyes, tentacles and velum. Structures on the left side were derived from 1a and 1d micromeres; la gave rise to the left eye, including the lens. Right side structures were derived from the 1c micromere and 1b contributed to the apical plate between the eyes and symmetrically to both sides of the velum. First quartet lineage data are compared with results from previous cell ablation experiments and with lineage data from other species.
Production of antisense RNA leads to effective and specific inhibition of gene expression in C. elegans muscle
Authors: Fire Andrew , Albertson Donna , Harrison Susan White , Moerman Donald G. 
Published: April 2021

ABSTRACT
We have used an antisense strategy to effectively disrupt the expression of two genes encoding myofilament proteins present in C. elegans body wall muscles. DNA segments from the unc-22 and unc-54 genes have been placed in reverse orientation in vectors designed to produce RNA in body wall muscles. When the resulting plasmids are injected into oocytes, progeny with defects in muscle function are produced. These animals have phenotypes consistent with reduction and/or elimination of function of the gene to which antisense RNA has been produced: twitching and disorganization of muscle filaments for the unc-22 antisense constructs and lack of muscle tone, slow movement, and egg laying defects for the unc-54 antisense constructs. A fraction of the affected animals transmit the defective-muscle trait to subsequent generations. In these cases the transforming DNA is present at high copy number and cosegregates with the observed muscle defects. We have examined several of the unc-22 antisense plasmid transformed lines to determine the mechanistic basis for the observed phenotypes. The RNA product of the endogenous unc-22 locus is present at normal levels and this RNA is properly spliced in the region homologous to the antisense RNA. No evidence for modification of this RNA by deamination of adenosine to inosine was found. In affected animals the level of protein product from the endogenous unc-22 locus is greatly reduced. Antisense RNA produced from the transforming DNA was detected and was much more abundant than ‘sense’ RNA from the endogenous locus. These data suggest that the observed phenotypes result from interference with a late step in gene expression, such as transport into the cytoplasm or translation.
Binding of a factor to an enhancer element responsible for the tissue specific expression of the chicken αA-crystallin gene
Authors: Matsuo Isao , Kitamura Masahi , Okazaki Kenji , Yasuda Kunio 
Published: April 2021

ABSTRACT
We have characterized a regulatory region of the chicken αA-crystallin gene using transfection assays, which revealed that a 84 base pair element (–162 to –79) in the 5’ flanking sequence is necessary and sufficient for lens-specific expression. A multimer of this element functions as lens-specific enhancer and synergistically activates transcription from chicken αA-crystallin or β-actin basal promoters fused to the CAT gene. In vivo competition experiments demonstrated that DNA sequences containing the 84 bp element reduced αA-crystallin–CAT fusion gene expression. A nuclear factor present exclusively in lens cells binds to the 84 bp element in the region between positions –165 and –140. Southwestern blot analysis showed that 61000 Mr (61×103Mr) lens nuclear protein exhibited DNA-binding activity specific to the 84 bp element. Our data suggested that the 61×103Mr nuclear protein, and the 84 bp element that it interacts with, may be involved in regulating the αA-crystallin gene expression in vivo.
Generation of pigmented stripes in albino mice by retroviral marking of neural crest melanoblasts
Authors: Huszar Dennis , Sharpe Arlene , Hashmi Sofie , Bouchard Brigitte , Houghton Alan , Jaenisch Rudolf 
Published: April 2021

ABSTRACT
The pigment cells of the skin are derived from melanoblasts which originate in the neural crest. The dorsoventral migration of melanoblasts has been visualized in pigment stripes seen in aggregation chimeras, and the width of these bands has suggested that the entire pigmentation of the coat is derived from a small number of founder cells. We have generated mosaic mice by marking single melanoblasts in utero to gain information on the clonal history of pigment-forming cells. A retroviral vector carrying the human tyrosinase gene was constructed and microinjected into neurulating albino mouse embryos. Albino mice are devoid of pigmentation due to deficiency of tyrosinase. Thus, transduction of the wild-type gene into the otherwise normal melanoblasts should rescue the mutant phenotype, giving rise to patches of pigmentation, which correspond to the area colonized by the mitotic progeny of a marked clone. Mosaic animals derived from the injected embryos indeed showed pigmented bands with a width strikingly similar to the ‘standard’ stripes seen in aggregation chimeras. These results are consistent with the notion that the unit width bands seen in aggregation chimeras represent the clonal progeny of a single melanoblast and verify Mintz’s (1967) conclusion that a few founder melanoblasts give rise to coat pigmentation. The pigment cells of the eye are of dual origin: the melanocytes in choroid and outer layer of the iris are derived from the neural crest and those in the pigment layer of the retina from the neuroepithelium of the optic cup. Marked clones in both lineages were observed in the eyes of many mosaic animals.
The nature of the mesoderm-inducing signal in Xenopus: a transfilter induction study
Authors: Slack J. M. W. 
Published: April 2021

ABSTRACT
A transfilter apparatus is described, which is suitable for neutralization experiments on embryonic induction, and it is used to investigate the sensitivity of the Xenopus mesoderm-inducing signal to various inhibitors. The vegetal (inducing) tissue is placed on one side of a membrane sandwich and the animal (responding) tissue on the other side. The sandwich consists of a nylon gauze in between two Nucleopore filters and enables inhibitors in the solution to have effective access to the gap between the tissues. Control experiments show a high proportion of positive inductions of a ventral character.
Using this apparatus, it is shown that the protein follistatin, which effectively inhibits activin A and B in vitro, has little or no effect on the natural signal. Likewise, antibodies to basic fibroblast growth factor, which inhibit in vitro, do not inhibit the natural signal. The two inhibitors together have a slight effect. It is concluded that neither activin nor bFGF are major components of the signal emitted by the vegetal cells of the Xenopus blastula and transmitted across the liquid gap, although they might have some other role to play in the process.
Two agents of lower specificity do inhibit the transfilter induction: heparin and suramin. Suramin will also inhibit induction in animal-vegetal combinations with no intervening membranes while heparin does not. This suggests that the heparin inhibition can only occur when there is a liquid gap between the tissues, presumably because it can neutralize the signal in solution but cannot penetrate the explants themselves. The endogenous mesoderm-inducing factor(s) should therefore be sensitive to heparin in vitro.
The Mus musculus domesticus Tdy allele acts later than the Mus musculus musculus Tdy allele: a basis for XY sex-reversal in C57BL/6-YPOS mice
Authors: Palmer Stephen J. , Burgoyne Paul S. 
Published: April 2021

ABSTRACT
Consomic C57BL/6 males, carrying either the Mus musculus musculus-derived C57BL/6 Y chromosome or the Mus musculus domesticus-derived Poschiavinus Y chromosome, were outcrossed to females of the inbred strains C3H/Bi and CXBH/By and to females of the random bred strain MF1/Ola. In a study at 12.5 days post coitum, gonads of XYCS7 and XYPOS fetuses were assessed for the presence of testicular cords. It was found that XYPOS fetuses had a later onset of testicular development than XY57 fetuses. Limb development, which was monitored as a measure of overall development, was unaffected by the strain of Y present. These data were supported by a longitudinal study in which the increased growth rate of the testes relative to undifferentiated gonads, was also shown to be delayed in XYPOS fetuses. The extent of the delay was estimated to be approximately 14 h. It is concluded that this delay in the onset of testicular differentiation must be caused by differences between the two Y-chromosome types, most probably allelic differences in the testis determinant Tdy.
Developmental analysis of the eye lens obsolescence (Elo) gene in the mouse: cell proliferation and Elo gene expression in the aggregation chimera
Authors: Yoshiki Atsushi , Hanazono Makoto , Oda Sen-Ichi , Wakasugi Noboru , Sakakura Teruyo , Kusakabe Moriaki 
Published: April 2021

ABSTRACT
This study investigates the primary effect of the eye lens obsolescence (Elo) gene of the mouse. Morphological features of the Elo lens were defined as follows: (1) deficient elongation of lens fiber cells, (2) morphological abnormality of nuclei of lens fiber cells, (3) lack of eosinophilic granules in the central fiber cells and (4) rupture of lens capsule in the posterior region. We have immunohistologically examined, by means of an in vivo BrdU incorporation system, whether or not the Elo gene regulates cell proliferation during lens development. The lens fiber cells were morphologically abnormal in day 13 embryonic Elo lens. However, there were no significant differences in morphology or cell proliferation between normal and Elo lens epithelium until day 14 of gestation. After day 15, the total cell number in the Elo lens epithelium was significantly less than that in the normal, but the total numbers of S-phase cells in the two genotypes were not significantly different. The ratio of the total S-phase cell number to the total number of lens epithelial cells may be affected by the developmental stage, but not directly by the genotype. The genotype, however, may be having a direct influence at later ages because malformation of Elo lens fiber cells must cause reduction of the total number of lens epithelial cells in older embryos. Although, at 30 days old, Elo lens cells were externally extruded through the ruptured capsule into the vitreous cavity, BrdU-labelled lens epithelial cells were detectable. To investigate whether the Elo lens phenotype is determined by its own genotype or by its cellular environment, we produced aggregation chimeras between C3H-Elo/+(C/C) and BALB/c (c/c). Most lenses of BALB/c dominant chimeras were oval in shape without the ruptured lens capsule. However, they were opaque in the center and slightly smaller in size than normal. The lenses of C3H-E/o/ + dominant chimeras were morphologically similar to the Elo lens. Although normal nuclei were regularly arranged in the anterior region, Elo-type nuclei were located in the posterior region. Immunohistological staining by using anti-C3H strain-specific antibody demonstrated that the lens fiber cells with abnormal nuclei were derived only from C3H-Elo/+, not from BALB/c. These observations suggest that the primary effect of the Elo gene in the developing lens may be specific to the fiber cell differentiation rather than to the cell proliferation. Moreover, the Elo gene may be autonomously expressed in the differentiating lens fiber cells, and intracellularly inhibit fiber cell elongation.
Evidence that hypophysis and hypothalamus constitute a single entity from the primary stage of histogenesis
Authors: Kawamura Kosuke , Kikuyama Sakae 
Published: April 2021

Abstract
To identify the origin of the primordial pituitary cells in early stages of amphibian embryos before the formation of Rathke’s pouch or its equivalent, transplantation experiments were carried out on Bufo. Wild-type embryos at the open neurula stage were employed as donors and albino embryos at the corresponding stage as recipients. Since brain and pituitary cells of wild-type animalscontain a great number of melanin granules, whereas albino cells are devoid of them, the melanin granules enabled the fate of transplants to be traced.
The anterior part of the neural ridge (ANR) was found to be the almost exclusive source of the secretory cells in the epithelial pituitary gland (pars distalis, pars intermedia and pars tuberalis). Transplantation of either the central part of the anterior neural plate (NP) or the ANR revealed that the pituitary primordium and the anlage of the posterior hypothalamus (infundibulum) are closely apposed at the open neurula stage. As morphogenetic movement proceeds, each of the two entities takes a separate migration route. The former part (NP) takes a ventrocaudal route to become the diencephalic floor, and the latter part (ANR) takes a rostroventral route to acquire morphological contact with the anterodorsal wall of the foregut before differentiating into the epithelial hypophysis. At the end of the tail-bud stage, they meet again beneath the diencephalic floor and establish a hypothalamo-hypophyseal connection. Some of the ANR cells are incorporated into the preoptic region of the anterior hypothalamus. None of the NP cells develop into epithelial pituitary cells.
We conclude that the epithelial pituitary gland is not stomodeal, but placodal, in origin and that the hypothalamo-hypophyseal complex may be regarded as a single entity from an ontogenetic viewpoint.
Developmentally regulated expression ofα6 integrin in avian embryos
Authors: Bronner-Fraser Marianne , Artinger Michael , Muschler Iohn , Horwitz Alan F. 
Published: April 2021

AbstractThe distribution pattern of the avian α6 integrin subunit was examined during early stages of development. The results show that this subunit is prevalent in cells of the developing nervous system and muscle. α6 is first observed on neuroepithelial cells of the cranial neural plate and trunk neural tube. With time, immunoreactivity becomes prominent near the lumen and ventrolateral portions of the neural tube, co-distributing with neurons and axons, particularly notable on commissural neurons. The α6 expression pattern is dynamic in the nenral tube, with immunoreactivity peaking by embryonic day 6 (stage 30) and decreasing thereafter. The ventral roots and retina exhibit high levels of immnno-reactivity throughout development. In the peripheral nervous system, α6 immunoreactivity first appears on a subpopulation of sympathoadrenal cells around the dorsal aorta and later in the dorsal root ganglia shortly after gangliogenesis. Immunoreactivity appears on pro-spective myotomal cells as the somites delaminate into the dermomyotome and sclerotome, remaining prominent on myoblasts and differentiated muscle at all stages. The mesonephros also has intense immunoreactivity. In the periphery, α6 immunoreactive regions often in proximity to laminin, which is thought to be the ligand of α6β1 integrin.