bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell lineage analysis of the avian neural crest
Authors: Bronner-Fraser Marianne , Fraser Scott E. 
Published: April 2021

Abstract
Neural crest cells migrate extensively and give rise to diverse cell types, including cells of the sensory and autonomic nervous systems. A major unanswered question concerning the neural crest is when and how the neural crest cells become determined to adopt a particular fate. We have explored the developmental potential of trunk neural crest cells in avian embryos by microinjecting a vital dye, lysinated rhodamine dextran (LRD), into individual cells within the dorsal neural tube. We find that premigratory and emigrating neural crest cells give rise to descendants with distinct phenotypes in multiple neural crest derivatives. These results are consistent with the idea that neural crest cells are multipotent prior to their emigration from the neural tube and become restricted in phenotype after emigration from the neural tube either during their migration or at their sites of localization. To determine whether neural crest cells become restricted during their migration, we have microinjected individual trunk neural crest cells with dye shortly after they leave the neural tube or as they migrate through the somite. We find that a majority of the clones derived from migrating neural crest cells appear to be multipotent; individual migrating neural crest cells gave rise to both sensory and sympathetic neurons, as well as cells with the morphological characteristics of Schwann cells, and other nonneuronal cells. Even those clones contributing to only one neural crest derivative often contained both neurofilament-positive and neurofilament-negative cells. These data demonstrate that migrating trunk neural crest cells, like their premigratory progenitors, can be multipotent. They give rise to cells in multiple neural crest derivatives and contribute to both neuronal and non-neuronal elements within a given derivative. Thus, restriction of neural crest cell fate must occur relatively late in migration or at the final destinations.
Cell commitment and cell interactions in the ectoderm of Drosophila melanogaster
Authors: Stüttem Isabella , Campos-Ortega José A. 
Published: April 2021

Abstract
The separation of neural from epidermal progenitor cells in the ventral neuroectoderm of Drosophila is thought to be mediated by cellular interactions. In order to verify the occurrence of regulatory signals and to test the neurogenic capabilities of cells from various regions of the ectoderm, we have carried out homotopic and heterotopic transplantations of single ectodermal cells. We found that cells from any of the tested regions, with the exception of the proctodeal anlage, are capable of developing as neuroblasts following their transplantation into the ventral neuroectoderm. These neurogenic capabilities are gradually distributed. Cells from the procephalic and ventral neurogenic regions exhibit maximal capabilities, as shown by their behavior in heterotopic transplantations. However, the two neurogenic regions differ from each other in that no epidermalising signals can be demonstrated to occur within the procephalic neuroectoderm, whereas such signals are strong within the ventral neuroectoderm; in addition, neuralising signals from neighbouring cells seem to be necessary for neuroectodermal cells to develop as neuroblasts. Other ectodermal regions whose cells exhibit weaker neurogenic capabilities are, in decreasing order of capability, the dorsal epidermal anlage, the anterolateral region of the procephalic lobe, comprising the anlage of the pharynx, and the anterior pole of the embryo, corresponding to the anlagen of the stomodeum and ectodermal anterior midgut. We assume that, during development in situ, the neurogenic capabilities of all these cells are suppressed by inhibitory signals, which are released upon heterotopic transplantation into the neuroectoderm. A community effect which prevents groups of dorsal epidermal cells from taking on a neural fate upon their transplantation into the ventral neuroectoderm, is shown. Finally, we hypothesize that the lack of neurogenic capability in the cells from the proctodeal anlage is due to the absence of products of the proneural genes.
The involvement of retinoic acid in the development of the vertebrate central nervous system
Authors: Maden Malcolm , Holder Nigel 
Published: April 2021

Abstract
We discuss here both previously published data and our current experiments which suggest that the vitamin A derivative, retinoic acid (RA), may play a role in the development of the vertebrate central nervous system (CNS). This evidence comes from the following: both an excess and a deficiency of vitamin A causes embryonic defects of the CNS; RA has been detected endogenously in the CNS; RA stimulates neurite outgrowth; the retinoic acid receptors have been detected with interesting distributions in the CNS; the binding protein for retinol, namely cellular retinol binding protein (CRBP) is found in the radial glia of the ventral floor plate; the binding protein for RA, namely, cellular retinoic acid binding protein (CRABP) is found in particular sets of axons in the developing spinal cord, in particular rhombomeres in the developing hindbrain and in the neural crest. Some hypotheses for the possible role of RA in various aspects of CNS development are discussed.
Zygotic expression of the pebble locus is required for cytokinesis during the postblastoderm mitoses of Drosophila
Authors: Hime Gary , Saint Robert 
Published: April 2021

ABSTRACT
Mutations at the pebble locus of Drosophila melanogaster result in embryonic lethality. Examination of homo-zygous mutant embryos at the end of embryogenesis revealed the presence of fewer and larger cells which contained enlarged nuclei. Characterization of the embryonic cell cycles using DAPI, propidium iodide, anti-tubulin and anti-spectrin staining showed that the first thirteen rapid syncytial nuclear divisions proceeded normally in pebble mutant embryos. Following cellular-ization, the postblastoderm nuclear divisions occurred (mitoses 14, 15 and 16), but cytokinesis was never observed. Multinucleate cells and duplicate mitotic figures were seen within single cells at the time of the cycle 15 mitoses. We conclude that zygotic expression of the pebble gene is required for cytokinesis following cellularization during Drosophila embryogenesis. We postulate that developmental regulation of zygotic transcription of the pebble gene is a consequence of the transition from syncytial to cellular mitoses during cycle 14 of embryogenesis.
Transforming Growth Factor- β1, β2 and - β3 in cartilage and bone cells during endochondral ossification in the chick
Authors: Thorp Barry H. , Anderson Irene , Jakowlew Sonia B. 
Published: April 2021

Abstract
The localization of TGF- β1, - β2 and - β3 was studied in the growth plate, epiphysis and metaphysis of the tibiotarsus of three-week-old chicks. The different TGF- β isoforms were localized to hypertrophic chondrocytes, chondroclasts, osteoblasts and osteoclasts using immunohistochemical staining analysis with specific TGF- β antibodies. TGF- βs in osteoclasts and chondroclasts were restricted to those cells located on the respective matrices. TGF-β3 localization was mainly cytoplasmic in the transitional (early hypertrophic) chondrocytes, but nuclear staining was also detected in some proliferating chondrocytes. The cell-specific localization of these TGF- β isoforms supports the hypothesis that TGF- β has a role in the coupling of new bone formation to bone and cartilage matrix resorption during osteochondral development and suggests that TGF- β may be a marker of chondrocyte differentiation. TGF- β localization preceded a marked increase in type II collagen mRNA expression in transitional chondrocytes, suggesting a role for TGF- β in the induction of synthesis of extracellular matrix.
The formation of commissures in the Drosophila CNS depends on the midline cells and on the Notch gene
Authors: Menne Thomas V. , Klämbt Christian 
Published: April 2021

ABSTRACT
The commissures of the Drosophila central nervous system (CNS) are formed in close relation to the ventral midline cells, a morphologically distinct set of cells located at the midline of the developing CNS. To analyze the function of these cells during commissure formation, we looked for mutations that result in the absence of commissures. One example of a gene that can give rise to such a phenotype is the neurogenic gene Notch. Here we show that mutant Notch embryos are devoid of commissural connections and have an abnormal midline. The midline cells of the embryonic Drosophila CNS are specified during the blastoderm stage about two hours before the first neuroblasts start to delaminate from the neurogenic region. To analyze Notch function for commissure development further, we took advantage of the Notchts1 allele. Temperature-shift experiments demonstrated that the lack of commissures in mutant Notch embryos results from defects in the anlage of the CNS midline cells. Here maternal as well as zygotic Notch function are required for the correct activation of the gene single-minded, since mutant Notch embryos derived from germ-line clones lack most of the single-minded-positive midline cells.
Functions of the cytoplasmic domain of the βPS integrin subunit during Drosophila development
Authors: Grinblat Yevgenya , Zusman Susan , Yee Gene , Hynes Richard O. , Kafatos Fotis C. 
Published: April 2021

ABSTRACT
Integrins constitute a family of membrane-spanning, heterodimeric proteins that mediate adhesive interactions between cells and surrounding extracellular matrices (or other cells) and participate in signal transduction. We are interested in assessing integrin functions in the context of developing Drosophila melanogaster. This report, using mutants of the βPS subunit encoded by the myospheroid (mys) locus, analyzes the relationships between integrin protein structure and developmental functions in an intact organism.
As a first step in this analysis, we demonstrated the ability of a fragment of wild-type mys genomic DNA, introduced into the germ line in a P-element vector P[my+], to rescue phenotypes attributed to lack of (or defects in) the endogenous βPS during several discrete morphogenetic events. We then produced in vitro a series of modifications of the wild-type P[mys+] transposon, which encode βPS derivatives with mutations within the small and highly conserved cytoplasmic domain. In vivo analysis of these mutant transposons led to the following conclusions. The cytoplasmic tail of βPS is essential for all developmental functions of the protein that were assayed.An intron at a conserved position in the DNA sequence encoding the cytoplasmic tail is thought to participate in important alternative splicing events in vertebrate β integrin subunit genes, but is not required for the developmental functions of the mys gene assayed here.Phosphorylation on two conserved tyrosines found in the C terminus of the βPS cytoplasmic tail is not necessary for the tested developmental functions.Four highly conserved amino acid residues found in the N-terminal portion of the cytoplasmic tail are important but not critical for the developmental functions of βPS; furthermore, the efficiencies with which these mutant proteins function during different morphogenetic processes vary greatly, strongly suggesting that the cytoplasmic interactions involving PS integrins are developmentally modulated.
diaphanous is required for cytokinesis in Drosophila and shares domains of similarity with the products of the limb deformity gene
Authors: Castrillon Diego H. , Wasserman Steven A. 
Published: April 2021

ABSTRACT
We show that the Drosophila gene diaphanous is required for cytokinesis. Males homozygous for the dia1 mutation are sterile due to a defect in cytokinesis in the germline. Females trans-heterozygous for dia1 and a deficiency are sterile and lay eggs with defective eggshells; failure of cytokinesis is observed in the follicle cell layer. Null alleles are lethal. Death occurs at the onset of pupation due to the absence of imaginal discs. Mitotic figures in larval neuroblasts were found to be polyploid, apparently due to a defect in cytokinesis. The predicted 123×103Mr protein contains two domains shared by the formin proteins, encoded by the limb deformity gene in the mouse. These formin homology domains, which we have termed FH1 and FH2, are also found in Bni1p, the product of a Saccharomyces cerevisiae gene required for normal cytokinesis in diploid yeast cells.
Ectopic induction and reorganization of Wnt-1 expression in quail/chick chimeras
Authors: Bally-Cuif Laure , Wassef Marion 
Published: April 2021

ABSTRACT
When grafted ectopically into the diencephalon of a chick host embryo, a portion of met-mesencephalon straddling the met-mesencephalic constriction has the capacity to induce En-2 expression in the surrounding host tissue. Subsequently, tectal and cerebellar structures, composed of both host and grafted cells, are reconstructed in this ectopic location at the expense of the host diencephalon. Previous experiments indicated that the induction of En-2 was correlated with Wnt-1 expression within the graft. The aim of the present study was: (i) to determine whether Wnt-1 expression was spatially regulated within the graft, (ii) to investigate whether host Wnt-1-expressing cells were also involved in the ectopic met-mesencephalic development and, if so, (iii) to localize these Wnt-1-positive domains in relation to the patterning of the ectopically developing met-mesencephalic territory. We studied the expression profile of Wnt-1, in relation with that of other positional markers, in quail/chick chimeras where various portions of met-mesencephalon had been grafted into the diencephalon. We found that Wnt-1 expression was reorganized within the graft, and that it was also induced in the host in contact with the graft. Moreover, these ectopic expressions of Wnt-1, in both the grafted and the surrounding host tissues, were organized in concert to form a continuous positive line at the host/graft junction, the location of which depended on the precise origin of the graft. Finally, we found that this line was frequently located at the limit between territories expressing different positional markers. We propose that Wnt-1 expression is turned on at the junction between domains of different phenotypes, and may be used as a border to stabilize these adjacent differently committed territories.
A developmental analysis of oligodendroglial integrins in primary cells: changes in αv-associated β subunits during differentiation
Authors: Milner Richard , ffrench-Constant Charles 
Published: April 2021

ABSTRACT
We have examined the expression of integrins on primary oligodendroglial cells during the differentiation of the pro- liferative oligodendrocyte precursor (O-2A progenitor) cell to the postmitotic oligodendrocyte. Cells of the oligoden- drocyte lineage expressed a limited repertoire of integrins: α6β1 and αv integrins including αvβ1, αvβ3 and αvβ5, as well as a potentially novel integrin αvβ80kDa. Integrin expression was developmentally regulated; during differen- tiation αvβ1 was reduced and αvβ5 upregulated. These results suggest that laminin and vitronectin are important extracellular matrix ligands for oligodendrocytes, and provide a rational explanation for previous observations that RGD peptides inhibit the expression of myelin-specific genes. They also suggest a simple model by which switching of integrin β subunits might regulate differentiation. As chimeric β1 integrins with a β5 cytoplasmic domain support proliferation less well than normal β1 integrins (Pasqualini and Hemler (1994), J. Cell Biol. 125, 447-460) the switch from αvβ1 to αvβ5 might play a key instructive role in the cessation of proliferation and subsequent differentiation.
Spatiotemporal dynamics of intracellular [Ca2+]i oscillations during the growth and meiotic maturation of mouse oocytes
Authors: Carroll John , Swann Karl , Whittingham David , Whitaker Michael 
Published: April 2021

ABSTRACT
Calcium oscillations occur during meiotic maturation of mouse oocytes. They also trigger activation at fertilization. We have monitored [Ca2+]i in oocytes at different stages of growth and maturation to examine how the calcium release mechanisms alter during oogenesis. Spontaneous calcium oscillations occur every 2-3 minutes in the majority of fully grown (but immature) mouse oocytes released from antral follicles and resuming meiosis. The oscillations last for 2-4 hours after release from the follicle and take the form of global synchronous [Ca2+]i increases throughout the cell. Rapid image acquisition or cooling the bath temperature from 28°C to 16°C did not reveal any wave-like spatial heterogeneity in the [Ca2+]i signal. Calcium appears to reach highest levels in the germinal vesicle but this apparent difference of [Ca2+] in nucleus and cytoplasm is an artifact of dye loading. Smaller, growing immature oocytes are less competent: about 40% are able to resume meiosis and a similar proportion of these oocytes show spontaneous calcium oscillations. [Ca2+]i transients are not seen in oocytes that do not resume meiosis spontaneously in vitro. Nonetheless, these oocytes are capable of [Ca2+]i oscillations since they show them in response to the addition of carbachol or thimerosal. To examine how the properties of calcium release change during meiotic maturation, a calcium-releasing factor from sperm was microinjected into fully grown immature and mature oocytes. The sperm-factor-induced oscillations were about two-fold larger and longer in mature oocytes compared to immature oocytes. Calcium waves travelling at 40-60 µm/second were generated in mature oocytes, but not in immature oocytes. In some mature oocytes, successive calcium waves had different sites of origin. The modifications in the size and spatial organization of calcium transients during oocyte maturation may be a necessary prerequisite for normal fertilization.
Quantitative RT-PCR assays show Xist RNA levels are low in mouse female adult tissue, embryos and embryoid bodies
Authors: Buzin Carolyn H. , Mann Jeffrey R. , Singer-Sam Judith 
Published: April 2021

ABSTRACT
We have investigated expression of the Xist gene in mouse female adult kidney, embryos and embryonic stem (ES) cells undergoing in vitro differentiation as embryoid bodies. Using the quantitative RT-PCR single nucleotide primer extension (SNuPE) assay, we found that the amount of Xist RNA in adult kidney of three mouse strains was less than ∼2000 transcripts per cell, with only modest differences between strains carrying different Xce alleles. Female embryos 7.5 days post coitum had the same number of Xist transcripts per cell as isogenic adult tissue. Using quantitative oligonucleotide hybridization assays after RT-PCR, we investigated Xist expression in ES lines heterozygous at the Pgk-1 and Xist loci. We found that, while in most (XX) ES lines Xist RNA levels increased during embryoid body formation, the levels seen were less than 10% those found in adult female kidney. In addition, we found that the allelic ratio of Xist transcripts from reciprocal (XX) ES cell lines differentiating in vitro was identical to that of isogenic 10.5 to 11.5 day female embryos. These latter results suggest that there is no pattern of preferential paternal imprinting during days 1 to 9 of in vitro differentiation of ES cells. However, the influence of the Xce locus on the randomness of X-inactivation in embyros seems to operate also in ES cell lines. Our overall conclusion is that the low levels of Xist RNA in female kidney, embryos and differentiating (XX) ES cells are compatible only with models that do not require Xist RNA to cover the entire inactive X chromosome.
Hypoblastic tissue and fibroblast growth factor induce blood tissue (haemoglobin) in the early chick embryo
Authors: Gordon-Thomson C. , Fabian B. C. 
Published: April 2021

ABSTRACT
We have investigated the temporal and the causal basis of blood tissue specification in the chick embryo. Earlier workers have shown that the prospective blood-forming area is specified in a horseshoe-shaped area at the posterior side of the embryo. We found that cultured explants from the posterior marginal zone at stages XI to XIII (consisting of the posterior marginal zone and part of Koller’s sickle) have a high propensity to form haemoglobin (Hb), which could be inhibited at stage XI by adding antibody against basic fibroblast growth factor (bFGF) to the neutral culture medium; this treatment had no effect from stage XII onwards. The same result was found when whole embryos were cultured with an antiserum raised against bFGF, or with heparin.
In another series of experiments, we found that cultured pieces from the inner-core of stage XIII epiblasts (with or without hypoblast tissue) were able to form Hb, whereas inner-core pieces from the pre-hypoblast stages, namely stages X and XI, did not form Hb. The capacity to form Hb, however, could be conferred upon the inner-core pieces from stage X epiblasts if bFGF at a concentration of 75-150 ng/ml was added to the culture medium. Furthermore, and most pertinently, the capacity to form Hb could be conferred on stage X inner-core pieces when they were co-cultured with hypoblast from a stage XIII embryo in a sandwich explant. Thus the inductive role of the hypoblast appears to be mediated via bFGF. This conclusion was confirmed by our finding that the antibody to bFGF inhibited the formation of Hb in these hypoblast sandwich explants.
We propose that the erythropoietic cell lineage, i.e. blood tissue, is determined in the chick embryo before stage XII by a bFGF-type of inductive signal from the emerging hypoblast adjacent to Koller’s sickle, in the area encompassing the posterior marginal zone. The morphogenetic changes that take place in the epiblast and hypoblast between stages X and XIII are considered in the discussion, especially with respect to how the posterior horseshoe of blood-forming tissue arises in response to the inductive signal.
Integrin switching regulates normal trophoblast invasion
Authors: Damsky Caroline H. , Librach Clifford , Lim Kee-Hak , Fitzgerald Marilyn L. , McMaster Michael T. , Janatpour Mary , Zhou Yan , Logan Susan K. , Fisher Susan J. 
Published: April 2021

ABSTRACT
Cells invade extracellular matrices in a regulated manner at specific times and places during normal development. A dramatic example is trophoblast invasion of the uterine wall. Previous studies have shown that differentiation of trophoblasts to an invasive phenotype is accompanied by temporally and spatially regulated switching of their integrin repertoire. In the first trimester human placenta, α6 integrins are restricted to cytotrophoblast (CTB) stem cells and downregulated in invasive CTBs, whereas α5β1 and α1β1 integrins are upregulated in differentiating and invasive CTBs. The goal of the present study was to determine whether these changes have functional consequences for CTB invasiveness. Using an in vitro invasion model, we determined first that aggregates of invading first trimester CTBs in vitro undergo the same pattern of integrin switching as was observed in situ, thereby validating the utility of the model. We then showed that antibody perturbation of interactions involving laminin or collagen type IV and their integrin α1/β1 receptor inhibited invasion by CTBs, whereas perturbing interactions between fibronectin and the α5/β1 fibronectin receptor accelerated invasion. Finally, we report that later gestation CTBs, which display greatly decreased invasive capacity, are also unable to upregulate α1β1 complexes, providing further evidence that this integrin is critical for CTB invasion. This gestational regulation is transcriptional. These data indicate that integrin switching observed during differentiation in situ has significant functional consequences for CTB invasion. The data suggest further that differentiating CTBs upregulate counterbalancing invasion-accelerating and invasion-restraining adhesion mechanisms. We propose that this contributes to regulating the depth of CTB invasion during normal implantation.