bluuebunny/crossref_metadata_2025_split huggingface dataset:
open brain, a new mouse mutant with severe neural tube defects, shows altered gene expression patterns in the developing spinal cord
Authors: Günther Thomas , Struwe Marina , Aguzzi Adriano , Schughart Klaus 
Published: April 2021

ABSTRACT
We describe a new mouse mutation, designated open brain (opb), which results in severe defects in the developing neural tube. Homozygous opb embryos exhibited an exen-cephalic malformation involving the forebrain, midbrain and hindbrain regions. The primary defect of the exen-cephaly could be traced back to a failure to initiate neural tube closure at the midbrain-forebrain boundary. Severe malformations in the spinal cord and dorsal root ganglia were observed in the thoracic region. The spinal cord of opb mutant embryos exhibited an abnormal circular to oval shape and showed defects in both ventral and dorsal regions. In severely affected spinal cord regions, a dor-salmost region of cells negative for Wnt-3a, Msx-2, Pax-3 and Pax-6 gene expression was detected and dorsal expression of Pax-6 was increased. In ventral regions, the area of Shh and HNF-3β expression was enlarged and the future motor neuron horns appeared to be reduced in size. These observations indicate that opb embryos exhibit defects in the specification of cells along the dorsoventral axis of the developing spinal cord. Although small dorsal root ganglia were formed in opb mutants, their metameric organization was lost. In addition, defects in eye development and malformations in the axial skeleton and developing limbs were observed. The implications of these findings are discussed in the context of dorsoventral patterning of the developing neural tube and compared with known mouse mutants exhibiting similar defects.
Role of leukemia inhibitory factor and its receptor in mouse primordial germ cell growth
Authors: Cheng Linzhao , Gearing David P. , White Lynn S. , Compton Debra L. , Schooley Ken , Donovan Peter J. 
Published: April 2021

ABSTRACT
The pleiotropic cytokine leukemia inhibitory factor (LIF) is able to promote the growth of mouse primordial germ cells (PGCs) in culture. It is unclear whether LIF acts directly on PGCs or indirectly via feeder cells or embryonic somatic cells. To understand the role of LIF in PGC growth, we have carried out molecular and cell culture analyses to investigate the role of both the LIF ligand and its receptor in PGC development. LIF is able to stimulate PGC growth independently of the presence of feeder cells supporting the hypothesis that LIF acts directly on PGCs to promote their growth. We show here that transcripts for the low-affinity LIF receptor (LIFR), an integral component of the functional LIF receptor complex, are expressed in the developing gonad. Fluorescence-activated cell sorter (FACS) analysis, using an anti-LIFR antiserum, demonstrates that LIFR is present on the surface of PGCs, suggesting that PGCs are likely to be a direct target of LIF action in culture. Signalling via LIFR is essential for PGC growth in culture since the anti-LIFR antiserum, which blocks LIF binding to its receptor, abolishes PGC survival in culture. Two LIF-related cytokines, namely oncostatin M and ciliary neurotrophic factor, can also promote PGC growth in culture in addition to LIF. Thus one or more of these LIFR-dependent cytokines may play an important role in PGC development in mice.
The Serrate locus of Drosophila and its role in morphogenesis of the wing imaginal discs: control of cell proliferation
Authors: Speicher Stephan A. , Thomas Ulrich , Hinz Uwe , Knust Elisabeth 
Published: April 2021

ABSTRACT
The Drosophila gene Serrate encodes a transmembrane protein with 14 EGF-like repeats in its extracellular domain. Here we show that loss-of-function mutations in this gene lead to larval lethality. Homozygous mutant larvae fail to differentiate the anterior spiracles, exhibit poorly developed mouth-hooks and show a severe reduction in the size of the wing and haltere primordia, which is not due to cell death. The few homozygous mutant escapers that pupariate develop into pharate adults that almost completely lack wings and halteres. Clonal analysis in the adult epidermis demonstrates a requirement for Serrate during wing and haltere development. Targeted ectopic expression of Serrate in the imaginal discs using the yeast transcriptional activator Gal4 results in regionally restricted induction of cell proliferation, e. g. the ventral tissues in the case of the wings and halteres. The results suggest that the wild-type function of Serrate is required for the control of position-specific cell proliferation during development of meso- and metathoracic dorsal discs, which in turn exerts a direct effect on morphogenesis.
Dual regulation of the glycogen phosphorylase 2 gene of Dictyostelium discoideum: the effects of DIF-1, cAMP, NH3 and adenosine
Authors: Yin Yizhong , Rogers Patricia V. , Rutherford Charles L. 
Published: April 2021

ABSTRACT
Cell differentiation in Dictyostelium results in the formation of two cell types, stalk and spore cells. The stalk cells undergo programmed cell death, whereas spore cells retain viability. The current evidence suggests that stalk cell differentiation is induced by Differentiation Inducing Factor (DIF), while spore cell differentiation occurs in response to cAMP. We have discovered the first developmentally regulated Dictyostelium gene, the glycogen phosphorylase gene 2 (gp2) gene, that can be induced by both DIF-1 and cAMP, suggesting the possibility of a new group of developmentally regulated genes that have DIF-1 and cAMP dual responsiveness. The gp2 gene was found to be expressed in both prestalk/stalk cells and prespore/spore cells. The DIF-1 competence of the gp2 gene required uninterrupted development, whereas the cAMP-competence for the gene required only starvation. Both DIF-1 and cAMP induction of the gene could be inhibited by NH3, a factor that is thought to act as a developmental signal in Dictyostelium. Another developmental signal, adenosine, was found to repress the DIF-1 induction of the gp2 gene. Two introns in the gp2 gene were examined for their involvement in the regulation of the gene, but no regulatory function was detected. A model for the regulation of the gp2 gene during the development is proposed.
Null mutations in the αPS2 and βPS integrin subunit genes have distinct phenotypes
Authors: Brown Nicholas H. 
Published: April 2021

ABSTRACT
The two Drosophila position-specific (PS) integrins are expressed on complementary sides of sites where different cell layers adhere to each other, such as the attachments of the embryonic muscles to the epidermis. While there is suggestive evidence that the PS integrin-mediated adhesion is via the extracellular matrix, it is also possible that it occurs through the direct interaction of the two integrins, αPS1βPS and αPS2βPS. To help distinguish between these possibilities a comparison between the phenotypes caused by the absence of the βPS subunit and the absence of one of the PS α subunits, αPS2, has been made. Two pieces of evidence are provided that prove that the αPS2 subunit is encoded by the locus inflated (if). Firstly, three new if alleles have been isolated, each of which is associated with a molecular lesion in the αPS2 gene, and each of which results in the complete loss of if activity. Secondly, a 39 kb fragment of genomic DNA that encompasses the αPS2 gene completely rescues if mutations when introduced into the germline by P-element-mediated transformation. A comparison of the null inflated phenotype with that of the locus that encodes the βPS subunit, myospheroid (mys), reveals that while the βPS subunit is required for the adhesion of the epidermis along the dorsal midline, the αPS2 subunit is not. In if mutant embryos, the muscles remain attached to the other cell layers significantly longer than in a mys mutant embryo. This shows that the αPS2βPS integrin only contributes part of the adhesive activity at the sites of PS integrin adhesion, and rules out a model where PS integrin function occurs solely by the direct interaction of the two PS integrins.
The mago nashi locus encodes an essential product required for germ plasm assembly in Drosophila
Authors: Newmark Phillip A. , Boswell Robert E. 
Published: April 2021

ABSTRACT
In Drosophila, the localization of maternal determinants to the posterior pole of the oocyte is required for abdominal segmentation and germ cell formation. These processes are disrupted by maternal effect mutations in ten genes that constitute the posterior group. Here, the molecular analysis of one posterior group gene, mago nashi, is presented. Restriction fragment length polymorphisms and transcript alterations associated with mago nashi mutations were used to identify the mago nashi locus within a chromosomal walk. The mago nashi locus was sequenced and found to encode a 147 amino acid protein with no similarity to proteins of known or suspected function. The identification of the mago nashi locus was confirmed by sequencing mutant alleles and by P element-mediated transformation. Nonsense mutations in mago nashi, as well as a deletion of the 5′ coding sequences, result in zygotic lethality. The original mago nashi allele disrupts the localization of oskar mRNA and staufen protein to the posterior pole of the oocyte during oogenesis; anterior localization of bicoid mRNA is unaffected by the mutation. These results demonstrate that mago nashi encodes an essential product necessary for the localization of germ plasm components to the posterior pole of the oocyte.
Embryonic expression and cloning of the murine GATA-3 gene
Authors: George Kathleen M. , Leonard Mark W. , Roth Matthew E. , Lieuw Ken H. , Kioussis Dimitris , Grosveld Frank , Engel James Douglas 
Published: April 2021

ABSTRACT
We describe the embryonic expression pattern as well as the cloning and initial transcriptional regulatory analysis of the murine (m) GATA-3 gene. In situ hybridization shows that mGATA-3 mRNA accumulation is temporally and spatially regulated during early development: although found most abundantly in the placenta prior to 10 days of embryogenesis, mGATA-3 expression becomes restricted to specific cells within the embryonic central nervous system (in the mesencephalon, diencephalon, pons and inner ear) later in gestation. GATA-3 also shows a restricted expression pattern in the peripheral nervous system, including terminally differentiating cells in the cranial and sympathetic ganglia. In addition to this distinct pattern in the nervous system, mGATA-3 is also expressed in the embryonic kidney and the thymic rudiment, and further analysis showed that it is expressed throughout T lymphocyte differentiation.
To begin to investigate how this complex gene expression pattern is elicited, cloning and transcriptional regulatory analyses of the mGATA-3 gene were initiated. At least two regulatory elements (one positive and one negative) appear to be required for appropriate tissue-restricted regulation after transfection of mGATA-3-directed reporter genes into cells that naturally express GATA-3 (T lymphocytes and neuroblastoma cells). Furthermore, this same region of the locus confers developmentally appropriate expression in transgenic mice, but only in a subset of the tissues that naturally express the gene.
Expression of the heparin-binding cytokines, midkine (MK) and HB-GAM (pleiotrophin) is associated with epithelial-mesenchymal interactions during fetal development and organogenesis
Authors: Mitsiadis Thimios A. , Salmivirta Markku , Muramatsu Takashi , Muramatsu Hisako , Rauvala Heikki , Lehtonen Eero , Jalkanen Markku , Thesleff Irma 
Published: April 2021

ABSTRACT
Midkine (MK) and heparin binding-growth associated molecule (HB-GAM or pleiotrophin), constitute a new family of heparin-binding proteins implicated in the regulation of growth and differentiation (T. Muramatsu (1993)Int. J. Dev. Biol. 37, 183-188). We used affinity-purified antibodies against MK and HB-GAM to analyze their distribution during mouse embryonic development. From 9 to 14.5 day post-coitum (dpc), both proteins were detected in central and peripheral nervous systems, facial processes, limb buds, sense organs, respiratory, digestive, urogenital, and skeletal systems. MK and HB-GAM were often localized on the surface of differentiating cells and in basement membranes of organs undergoing epithelial-mesenchymal interactions. The levels of MK protein decreased considerably in the 16.5 dpc embryo, whereas HB-GAM staining persisted in many tissues. Our in situ hybridization results revealed a widespread expression of MK transcripts that was not always consistent with the distribution of MK protein in developing tissues. In many epithelio-mesenchymal organs MK and HB-GAM were codistributed with syndecan-1, a cell surface proteoglycan. In limb buds and facial processes, MK, HB-GAM, and syndecan-1 were localized to the apical epithelium and the adjacent proliferating mesenchyme. Both MK and HB-GAM bound syndecan-1 in solid-phase assays in a heparan sulfate-dependent manner. The biological effects of MK and HB-GAM on limb and facial mesenchyme were studied in vitro by application of beads preloaded with the proteins. Neither MK nor HB-GAM stimulated mesenchymal cell proliferation or induced syndecan-1 expression. Taken together these results indicate that MK and HB-GAM may play regulatory roles in differentiation and morphogenesis of the vertebrate embryo, particularly in epithelio-mesenchymal organs, and suggest molecular interactions with syndecan-1.
cloche, an early acting zebrafish gene, is required by both the endothelial and hematopoietic lineages
Authors: Stainier Didier Y. R. , Weinstein Brant M. , Detrich H. William , Zon Leonard I. , Fishman Mark C. 
Published: April 2021

ABSTRACT
Endothelial and hematopoietic cells appear synchronously on the extra-embryonic membranes of amniotes in structures known as blood islands. This observation has led to the suggestion that these two ventral lineages share a common progenitor. Recently, we have shown in the zebrafish, Danio rerio, that a single cell in the ventral marginal zone of the early blastula can give rise to both endothelial and blood cells as well as to other mesodermal cells (Stainier, D. Y. R., Lee, R. K. and Fishman, M. C. (1993). Development 119, 31-40; Lee, R. K. K., Stainier, D. Y. R., Weinstein, B. M. and Fishman, M. C. (1994). Development 120, 3361-3366). Here we describe a zebrafish mutation, cloche, that affects both the endothelial and hematopoietic lineages at a very early stage. The endocardium, the endothelial lining of the heart, is missing in mutant embryos. This deletion is selective as evidenced by the presence of other endothelial cells, for example those lining the main vessels of the trunk. Early cardiac morphogenesis proceeds normally even in the absence of the endocardium. The myocardial cells form a tube that is demarcated into chambers, beats rhythmically, but exhibits a reduced contractility. This functional deficit is likely due to the absence of the endocardial cells, although it may be a direct effect of the mutation on the myocardial cells. Cell transplantation studies reveal that the endothelial defect, i.e. the endocardial deletion, is a cell-autonomous lesion, consistent with the possibility that cloche is part of a signal transduction pathway.
In addition, the number of blood cells is greatly reduced in cloche mutants and the hematopoietic tissues show no expression of GATA-1 or GATA-2, two key hematopoietic transcription factors that are first expressed during early embryogenesis. These results show that cloche is involved in the genesis and early diversification of the endothelial and blood lineages, possibly by affecting a common progenitor cell population.
Repetitive sperm-induced Ca2+ transients in mouse oocytes are cell cycle dependent
Authors: Jones Keith T. , Carroll John , Merriman Julie A. , Whittingham David G. , Kono Tomohiro 
Published: April 2021

ABSTRACT
Mature mouse oocytes are arrested at metaphase of the second meiotic division. Completion of meiosis and a block to polyspermy is caused by a series of repetitive Ca2+ tran-sients triggered by the sperm at fertilization. These Ca2+ transients have been widely reported to last for a number of hours but when, or why, they cease is not known. Here we show that Ca2+ transients cease during entry into inter-phase, at the time when pronuclei are forming. In fertilized oocytes arrested at metaphase using colcemid, Ca2+ tran-sients continued for as long as measurements were made, up to 18 hours after fertilization. Therefore sperm is able to induce Ca2+ transients during metaphase but not during interphase. In addition metaphase II oocytes, but not pronuclear stage 1-cell embryos showed highly repetitive Ca2+ oscillations in response to microinjection of inositol trisphosphate. This was explored further by treating in vitro maturing oocytes at metaphase I for 4-5 hours with cycloheximide, which induced nuclear progression to inter-phase (nucleus formation) and subsequent re-entry to metaphase (nuclear envelope breakdown). Fertilization of cycloheximide-treated oocytes revealed that continuous Ca2+ oscillations in response to sperm were observed after nuclear envelope breakdown but not during interphase. However interphase oocytes were able to generate Ca2+ transients in response to thimerosal. This data suggests that the ability of the sperm to trigger repetitive Ca2+ transients in oocytes is modulated in a cell cycle-dependent manner.
Induction of notochord cell intercalation behavior and differentiation by progressive signals in the gastrula of Xenopus laevis
Authors: Domingo Carmen , Keller Ray 
Published: April 2021

ABSTRACT
We show that notochord-inducing signals are present during Xenopus laevis gastrulation and that they are important for both inducing and organizing cell behavior and differentiation in the notochord. Previous work showed that convergent extension of prospective noto-chordal and somitic mesoderm occurs by mediolateral cell intercalation to produce a longer, narrower tissue. Medio-lateral cell intercalation is driven by bipolar, mediolater-ally directed protrusive activity that elongates cells and then pulls them between one another along the mediolat-eral axis. This cell behavior, and subsequent notochordal cell differentiation, begins anteriorly and spreads posteri- orly along the notochordal-somitic boundary, and from this lateral boundary progresses medially towards the center of the notochord field. To examine whether these progressions of cell behaviors and differentiation are induced and organized during gastrulation, we grafted labeled cells from the prospective notochordal, somitic and epidermal regions of the gastrula into the notochordal region and monitored their behavior by low light, fluorescence videomicroscopy. Prospective notochordal, epidermal and somitic cells expressed mediolateral cell intercalation behavior in an anterior-to-posterior and lateral-to-medial order established by the host notochord. Behavioral changes were induced first and most dramatically among cells grafted next to the notochordal-somitic boundary, particularly those in direct contact with the boundary, sug-gesting that the boundary may provide signals that both induce and organize notochordal cell behaviors. By physi-cally impeding normal convergent extension movements, notochordal cell behaviors and differentiation were restricted to the anteriormost notochordal region and to the lateral notochordal-somitic boundary. These results show that mediolateral cell intercalation behavior and notochordal differentiation can be induced in the gastrula stage, among cells not normally expressing these charac-teristics, and that these characteristics are induced pro-gressively, most likely by signals emanating from the noto-chordal-somitic boundary. In addition, they show that morphogenetic movements during gastrulation are necessary for complete notochord formation and that the prospective notochord region is not determined by the onset of gastrulation.
groucho and hedgehog regulate engrailed expression in the anterior compartment of the Drosophila wing
Authors: Celis Jose F. de , Ruiz-Gómez Mar 
Published: April 2021

ABSTRACT
Drosophila imaginal discs are divided into units called compartments. Cells belonging to the same compartment are related by lineage and express a characteristic set of ‘selector genes’. The borders between compartments act as organizing centres that influence cell growth within compartments. Thus, in the cells immediately anterior to the anterior-posterior compartment boundary the presence of the hedgehog product causes expression of decapentaplegic, which, in turn, influences the growth and patterning of the wing disc. The normal growth of the disc requires that posterior-specific genes, such as hedgehog and engrailed are not expressed in cells of the anterior compartment. Here we show that hedgehog can activate engrailed in the anterior compartment and that both hedgehog and engrailed are specifically repressed in anterior cells by the activity of the neurogenic gene groucho. In groucho mutant discs, hedgehog and engrailed are expressed at the dorsoventral boundary of the anterior compartment, leading to the ectopic activation of decapentaplegic and patched and to a localised increase in cell growth associated with pattern duplications. The presence of engrailed in the anterior compartment causes the transformation of anterior into posterior structures.
Integrin α2β1 mediates interactions between developing embryonic retinal cells and collagen
Authors: Bradshaw Amy D. , McNagny Kelly M. , Gervin Dennis B. , Cann Gordon M. , Graf Thomas , Clegg Dennis O. 
Published: April 2021

ABSTRACT
In the developing nervous system, the extracellular matrix provides a source of extrinsic cues to guide determination of cell fate, neuroblast migration, axon outgrowth and synapse formation. In the neural retina, undifferentiated neuroepithelial precursor cells contact extracellular matrix that contains multiple collagen types. Collagens have been shown to support retinal cell adhesion and neurite outgrowth, but the integrin receptors mediating neuronal responses are not understood. Here we provide evidence that integrin α2β1 acts as a collagen receptor in the developing avian retina and examine its expression pattern. Using a recently described monoclonal antibody, MEP-17, α2 protein was detected in the developing retina by immunofluorescence in tissue sections and dissociated cells, and by immunoprecipitation. At embryonic day 4 (E4), when the majority of retinal cells are undifferentiated neuroepithelial cells, α2 immunoreactivity in sections was widespread and about half of cells dissociated in culture were α2 positive. At E6, after the retinal ganglion cell layer had differentiated, immunoreactivity in sections decreased in the central, more developed portion of the retina and 25% of dissociated cells were α2 positive. E6 retinal ganglion cells, identified by neurofilament immunoreactivity, did not express detectable α2 immunoreactivity. Immunoprecipitation experiments using E6 extracts demonstrated that the α2 subunit was paired with the β1 integrin subunit. By E12, α2 immunoreactivity in sections was confined to the extreme peripheral retina, although the antigen may be masked since expression levels comparable to or slightly higher than E6 could be detected in dissociated cells and extracts. By employing function blocking antibodies, it was shown that α2β1 integrin is necessary for cell adhesion and process outgrowth by embryonic retinal cells on collagens I and IV. Although α2 expression continued through E12, α2 activity was down regulated with increasing embryonic age, since α2-dependent adhesion and outgrowth declined. These data suggest a role for α2β1 in neuroepithelial cell interactions with collagen rather than for axon extension by retinal ganglion cells.