bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell-extracellular matrix interactions under in vivo conditions during interstitial cell migration in Hydra vulgaris
Authors: Zhang Xiaoming , Sarras Michael P. 
Published: April 2021

ABSTRACT
Interstitial cell (I-cell) migration in hydra is essential for establishment of the regional cell differentiation pattern in the organism. All previous in vivo studies have indicated that cell migration in hydra is a result of cell-cell interactions and chemotaxic gradients. Recently, in vitro cell adhesion studies indicated that isolated nematocytes could bind to substrata coated with isolated hydra mesoglea, fibronectin and type IV collagen. Under these conditions, nematocytes could be observed to migrate on some of these extracellular matrix components. By modifying previously described hydra grafting techniques, two procedures were developed to test specifically the role of extracellular matrix components during in vivo I-cell migration in hydra. In one approach, the extracellular matrix structure of the apical half of the hydra graft was perturbed using β-aminopropi-onitrile and β-xyloside. In the second approach, grafts were treated with fibronectin, RGDS synthetic peptide and antibody to fibronectin after grafting was performed. In both cases, I-cell migration from the basal half to the apical half of the grafts was quantitatively analyzed. Statistical analysis indicated that β-aminopropionitrile, fibronectin, RGDS synthetic peptide and antibody to fibronectin all were inhibitory to I-cell migration as compared to their respective controls.
β-xyloside treatment had no effect on interstitial cell migration. These results indicate the potential importance of cell-extracellular matrix interactions during in vivo I-cell migration in hydra.
An increase in intracellular pH during neural induction in Xenopus
Authors: Sater Amy K. , Alderton Janet M. , Steinhardt Richard A. 
Published: April 2021

ABSTRACT
In this paper, we show that an intracellular alkalinization of the dorsal ectoderm cells is among the earliest responses to neural induction in Xenopus. Planar explants of the dorsal marginal zone were prepared from embryos that had been microinjected during cleavage stages with the fluorescent pH indicator bis-carboxyethyl-carboxyfluores-cein-dextran (BCECF-dextran), and intracellular pH (pHi) was monitored continuously by emission ratio microfluo-rimetry. During stage 10.5, the dorsal ectoderm cells undergo a sustained intracellular alkalinization of approximately 0.1 pH units in response to neural induction; in the absence of the inductive signal, the pH of the dorsal ectoderm cells decreases slightly. Ectoderm cells within planar explants of the ventral marginal zone show little change in pH during a similar period. This increase in intracellular pH is inhibited by 4, 4′-dihydrodiisothio-cyanatostilbene-2, 2′-disulfonate (H2DIDS) or a low Na+/high Cl− medium, treatments that presumably affect anion transport. Under these conditions, expression of the anterior neural-specific homeobox gene engrailed is not detected, while the notochord-specific epitope recognized by the Tor-70 antibody is expressed in the presence of H2DIDS. This characteristic alkalinization is not evoked by pharmacological agents that reportedly alter ectodermal developmental pathways in Xenopus embryos, such as NH4Cl, phorbol esters, or cAMP-dependent protein kinase agonists. Our results suggest that an ionic regulatory event may participate in the regulation of gene expression in response to neural induction.
Activin-mediated mesoderm induction requires FGF
Authors: Cornell Robert A. , Kimelman David 
Published: April 2021

ABSTRACT
The early patterning of mesoderm in the Xenopus embryo requires signals from several intercellular factors, including mesoderm-inducing agents that belong to the fibroblast growth factor (FGF) and TGF-β families. In animal hemisphere explants (animal caps), basic FGF and the TGF-β family member activin are capable of converting pre-ectodermal cells to a mesodermal fate, although activin is much more effective at inducing dorsal and anterior mesoderm than is basic FGF. Using a dominant-negative form of the Xenopus type 1 FGF receptor, we show that an FGF signal is required for the full induction of mesoderm by activin. Animal caps isolated from embryos that have been injected with the truncated FGF receptor and cultured with activin do not extend and the induction of some genes, including cardiac actin and Xbra, is greatly diminished, while the induction of other genes, including the head organizer-specific genes gsc and Xlim-1, is less sensitive. These results are consistent with the phenotype of the truncated FGF receptor-injected embryo and imply that the activin induction of mesoderm depends on FGF, with some genes requiring a higher level of FGF signaling than others.
The Drosophila maternal-effect mutation grapes causes a metaphase arrest at nuclear cycle 13
Authors: Fogarty Patrick , Kalpin Robert F. , Sullivan William 
Published: April 2021

ABSTRACT
grapes (grp) is a second chromosome (36A-B) maternal-effect lethal mutation in Drosophila melanogaster. We demonstrate that the syncytial nuclear divisions of grp-derived embryos are normal through metaphase of nuclear cycle 12. However, as the embryos progress into telophase of cycle 12, the microtubule structures rapidly deteriorate and midbodies never form. Immediately following the failure of midbody formation, sister telophase products collide and form large tetraploid nuclei. These observations suggest that the function of the midbody in the syncytial embryo is to maintain separation of sister nuclei during telophase of the cortical divisions. After an abbreviated nuclear cycle 13 interphase, these polyploid nuclei progress through prophase and arrest in metaphase. The spindles associated with the arrested nuclei are stable for hours even though the microtubules are rapidly turning over. The nuclear cycle 13 anaphase separation of sister chromatids never occurs and the chromosomes, still encompassed by spindles, assume a telophase conformation. Eventually neighboring arrested spindles begin to associate and form large clusters of spindles and nuclei. To determine whether this arrest was the result of a disruption in normal developmental events that occur at this time, both grp-derived and wild-type embryos were exposed to X-irradiation. Syncytial wild-type embryos exhibit a high division error rate, but not a nuclear-cycle arrest after exposure to low doses of X-irradiation. In contrast, grp-derived embryos exhibit a metaphase arrest in response to equivalent doses of X-irradiation. This arrest can be induced even in the early syncytial divisions prior to nuclear migration. These results suggest that the nuclear cycle 13 metaphase arrest of unexposed grp-derived embryos is independent of the division-cycle transitions that also occur at this stage. Instead, it may be the result of a previously unidentified feedback mechanism.
The relationship between ovarian and embryonic dorsoventral patterning in Drosophila
Authors: Roth Siegfried , Schüpbach Trudi 
Published: April 2021

ABSTRACT
In Drosophila, the dorsoventral asymmetry of the egg chamber depends on a dorsalizing signal that emanates from the oocyte. This signal is supplied by the TGFα-like gurken protein whose RNA is localized to the dorsal-anterior corner of the oocyte. gurken protein is the potential ligand of the Drosophila EGF receptor homolog (torpedo), which is expressed in the follicular epithelium surrounding the oocyte. Here, we describe how changes in the dorsalizing germ-line signal affect the embryonic dorsoventral pattern. A reduction in strength of the germ-line signal as produced by mutations in gurken or torpedo does not change the slope of the embryonic dorsoventral morphogen gradient, but causes a splitting of the gradient ventrally. This leads to embryos with two partial dorsoven-tral axes. A change in distribution of the germ-line signal as caused by fs(1)K10, squid and orb mutations leads to a shift in the orientation of the embryonic dorsoventral axis relative to the anterior-posterior axis. In extreme cases, this results in embryos with a dorsoventral axis almost parallel to the anterior-posterior axis. These results imply that gurken, unlike other localized cytoplasmic determinants, is not directly responsible for the establishment of cell fates along a body axis, but that it restricts and orients an active axis-forming process which occurs later in the follicular epithelium or in the early embryo.
New functions of the Drosophila rhomboid gene during embryonic and adult development are revealed by a novel genetic method, enhancer piracy
Authors: Noll Rebekka , Sturtevant Mark A. , Gollapudi Raghava R. , Bier Ethan 
Published: April 2021

ABSTRACT
Localized expression of the Drosophila rhomboid (rho) gene has been proposed to hyperactivate EGF-Receptor signaling in specific cells during development of the embryo and adult. In this report we use a novel transposon based genetic method, enhancer piracy, to drive ectopic expression of a rho cDNA transgene by endogenous genomic enhancers. Many enhancer piracy transposon-rho insertions cause dominant phenotypes, over half of which cannot be duplicated by ubiquitous expression of rho. Genetic interactions between various dominant enhancer piracy alleles and mutations in the EGF-R/RAS signaling pathway indicate that many of these novel phenotypes result from ectopic activation of EGF-R signaling.
Patterned mis-expression of the rho cDNA transgene cor- relates in several cases with localized dominant enhancer piracy phenotypes. Enhancer piracy lines reveal an unan- ticipated role for rho in imaginal disc formation and provide the first evidence that mis-expression of rho is suf- ficient for converting entire intervein sectors into veins. Enhancer piracy may prove to be a general strategy for obtaining dominant alleles of a gene of interest in diverse insects, worms, plants, and potentially in vertebrates such as mice and fish.
Timing of neuronal death in trkA, trkB and trkC mutant embryos reveals developmental changes in sensory neuron dependence on Trk signalling
Authors: Piñón Luzia G. P. , Minichiello Liliana , Klein Rüdiger , Davies Alun M. 
Published: April 2021

ABSTRACT
The sensory neurons of the embryonic mouse trigeminal ganglion are supported in culture by different neurotrophins at successive stages of development. Initially the neurons survive in response to BDNF and NT3 and later switch to becoming NGF-dependent (Buchman, V. I. and Davies, A. M. (1993), Development 118, 989-1001). To determine if this in vitro switch in neurotrophin responsiveness is physiologically relevant, we studied the timing of neuronal death in the trigeminal ganglia of embryos that are homozygous for null mutations in the trkA, trkB and trkC genes, which encode receptor tyrosine kinases for NGF, BDNF and NT3, respectively. In wild-type embryos, the number of pyknotic nuclei increased from E11 to peak between E13 and E14, and decreased gradually at later ages, becoming negligible by birth. Neuronal death in the trigeminal ganglia of trkA−/− embryos also peaked between E13 and E14, but was almost threefold greater than in wild-type embryos at this stage. Whereas there was no significant difference between the number of pyknotic nuclei in trkA−/− and wild-type embryos at E11 and E12, there was a substantial increase in the number of pyknotic nuclei in the trigeminal ganglia of trkB−/− at these earlier stages. Counts of the total number of neurons in E13 trigeminal ganglia revealed a marked decrease in trkB−/− but not trkA−/− or trkC−/− embryos. Consistent with the later onset of excessive neuronal death in trkA−/− embryos, there was a marked decrease in the neuronal complement of the trigeminal ganglia of trkA−/− embryos at E15. These results demonstrate that TrkB signalling is required for the in vivo survival of many trigeminal neurons during the early stages of target field innervation before they become NGF-dependent.
Distinct spatial and temporal functions for PS integrins during Drosophila wing morphogenesis
Authors: Brabant Marc C. , Fristrom Dianne , Bunch Thomas A. , Brower Danny L. 
Published: April 2021

ABSTRACT
At the onset of pupariation in the Drosophila wing, the PS1 and PS2 integrins are expressed preferentially on the dorsal and ventral wing epithelia, respectively. Clonal analysis experiments have indicated that integrins are required to maintain the tight association of the wing surfaces. Surprisingly, we find that even in clones of cells lacking integrins the wing layers become apposed early in metamorphosis. However, following the normal period of wing separation, large integrin mutant clones do not become re-apposed in the pupa, and integrins are not organized in basal plaques in cells opposite a mutant clone. Paradoxically, our experiments indicate that at least one integrin function requires different integrins on the dorsal and ventral wing surfaces, however in some cases both αPS subunits can function to some degree on each wing surface. Finally, overexpression of an αPS subunit throughout the wing leads to a dominant wing blister phenotype, and the critical period for this phenotype is the beginning of pupariation. These data indicate that integrin requirements in wing morphogenesis can be separated into early (prepupal) and late (pupal) functions. The late function seems to reflect the traditional view of integrins as cell-matrix adhesion proteins. The early requirement, which probably requires dorsoventral segregation of PS1 and PS2, suggests functions for PS1 and PS2 in signaling events that regulate morphogenesis.
BMP signaling during bone pattern determination in the developing limb
Authors: Kawakami Yasuhiko , Ishikawa Tetsuya , Shimabara Masakiyo , Tanda Nobuya , Enomoto-Iwamoto Motomi , Iwamoto Masahiro , Kuwana Takashi , Ueki Ayako , Noji Sumihare , Nohno Tsutomu 
Published: April 2021

ABSTRACT
To examine the role of BMP signaling during limb pattern formation, we isolated chicken cDNAs encoding type I (BRK-1 and BRK-2) and type II (BRK-3) receptors for bone morphogenetic proteins. BRK-2 and BRK-3, which constitute dual-affinity signaling receptor complexes for BMPs, are co-expressed in condensing precartilaginous cells, while BRK-1 is weakly expressed in the limb mesenchyme. BRK-3 is also expressed in the apical ectodermal ridge and interdigital limb mesenchyme. BRK-2 is intensely expressed in the posterior-distal region of the limb bud. During digit duplication by implanting Sonic hedgehog-producing cells, BRK-2 expression is induced anteriorly in the new digit forming region as observed for BMP-2 and BMP-7 expression in the limb bud. Dominant-negative effects on BMP signaling were obtained by over-expressing kinase domain-deficient forms of the receptors. Chondrogenesis of limb mesenchymal cells is markedly inhibited by dominant-negative BRK-2 and BRK-3, but not by BRK-1. Although the bone pattern was not disturbed by expressing individual dominant-negative BRK independently, preferential distal and posterior limb truncations resulted from co-expressing the dominant-negative forms of BRK-2 and BRK-3 in the whole limb bud, thus providing evidence that BMPs are essential morphogenetic signals for limb bone patterning.
Role of Bicaudal-D in patterning the Drosophila egg chamber in mid-oogenesis
Authors: Swan Andrew , Suter Beat 
Published: April 2021

ABSTRACT
The Bicaudal-D (Bic-D) gene is required early in Drosophila oogenesis for the differentiation of an oocyte from one of a cluster of 16 interconnected germarial cells. To analyze the role of Bic-D later in oogenesis, we have con-structed Drosophila lines in which Bic-D expression is under the control of the hsp70 promoter. In these flies, Bic-D activity can be induced early in oogenesis, allowing an oocyte to be made. Then, by shifting females to non-inducing conditions, Bic-D levels are depleted for the remainder of oogenesis. Using this system, we find that Bic-D is indeed required in the later stages of oogenesis. In ovaries from mutant females, oocyte growth is reduced, apparently due to defects in nurse-cell-to-oocyte transport. Smaller oocyte size results in the misalignment of follicle cells and the underlying germ line, leading to ventralization of dorsal follicle cells and to defects in centripetal cell migration. In addition, we show that Bic-D is required for the localization of specific mRNAs at both the anterior and posterior of the oocyte.
The role of bone morphogenetic proteins in vertebral development
Authors: Monsoro-Burq Anne-Hélène , Duprez Delphine , Watanabe Yuji , Bontoux Martine , Vincent Christine , Brickell Paul , Douarin Nicole Le 
Published: April 2021

ABSTRACT
This study first shows a striking parallel between the expression patterns of the Bmp4, Msx1 and Msx2 genes in the lateral ridges of the neural plate before neural tube closure and later on, in the dorsal neural tube and superficial midline ectoderm. We have previously shown that the spinous process of the vertebra is formed from Msx1- and 2-expressing mesenchyme and that the dorsal neural tube can induce the differentiation of subcutaneous cartilage from the somitic mesenchyme. We show here that mouse BMP4- or human BMP2-producing cells grafted dorsally to the neural tube at E2 or E3 increase considerably the amount of Msx-expressing mesenchymal cells which are normally recruited from the somite to form the spinous process of the vertebra. Later on, the dorsal part of the vertebra is enlarged, resulting in vertebral fusion and, in some cases (e.g. grafts made at E3), in the formation of a ‘giant’ spinous process-like structure dorsally. In strong contrast, BMP-producing cells grafted laterally to the neural tube at E2 exerted a negative effect on the expression of Pax1 and Pax3 genes in the somitic mesenchyme, which then turned on Msx genes. Moreover, scle-rotomal cell growth and differentiation into cartilage were then inhibited. Dorsalization of the neural tube, manifested by expression of Msx and Pax3 genes in the basal plate contacting the BMP-producing cells, was also observed.
In conclusion, this study demonstrates that differentiation of the ventrolateral and dorsal parts of the vertebral cartilage is controlled by different molecular mechanisms. The former develops under the influence of signals arising from the floor plate-notochord complex. These signals inhibit the development of dorsal subcutaneous cartilage forming the spinous process, which requires the influence of BMP4 to differentiate.
Extracellular Ca2+ entry and Ca2+ release from inositol 1,4,5-trisphosphate-sensitive stores function at fertilization in oocytes of the marine bivalve Mytilus edulis
Authors: Deguchi Ryusaku , Osanai Kenzi , Morisawa Masaaki 
Published: April 2021

ABSTRACT
An oocyte of the marine bivalve Mytilus edulis, which is arrested at metaphase I, reinitiates meiosis at fertilization. The fertilized oocyte shows increases in intracellular Ca2+ ([Ca2+]i) comprising three different phases: an initial large [Ca2+]i transient, a subsequent low but sustained [Ca2+]i elevation, and repetitive small [Ca2+]i transients. In this study, we have investigated the sources and mechanisms of the sperm-induced [Ca2+]i increases. Application of methoxyverapamil (D-600), an inhibitor of voltage-dependent Ca2+ influx, suppressed the initial [Ca2+]i transient but did not affect the following two phases of [Ca2+]i changes. Injection of heparin, an antagonist of the inositol 1,4,5-trisphosphate (IP3) receptor, inhibited the later two phases without much affecting the initial transient. Combined application of D-600 and heparin almost completely abolished the three phases of the sperm-induced [Ca2+]i changes. Furthermore, Ca2+ influx caused by seawater containing excess K+ was blocked by D-600 but not by heparin, and IP3-induced Ca2+ release caused by photolysis of injected ‘caged’ derivatives of IP3 was blocked by heparin but not by D-600. These results strongly suggest that two types of Ca2+ mobilization systems, the extracellular Ca2+ entry responsible for an initial [Ca2+]i transient and the IP3 receptor-mediated Ca2+ release responsible for the following two phases of [Ca2+]i changes, function at fertilization of Mytilus oocytes.
VEGF-C receptor binding and pattern of expression with VEGFR-3 suggests a role in lymphatic vascular development
Authors: Kukk Eola , Lymboussaki Athina , Taira Suvi , Kaipainen Arja , Jeltsch Michael , Joukov Vladimir , Alitalo Kari 
Published: April 2021

ABSTRACT
The vascular endothelial growth factor family has recently been expanded by the isolation of two new VEGF-related factors, VEGF-B and VEGF-C. The physiological functions of these factors are largely unknown. Here we report the cloning and characterization of mouse VEGF-C, which is produced as a disulfide-linked dimer of 415 amino acid residue polypeptides, sharing an 85% identity with the human VEGF-C amino acid sequence. The recombinant mouse VEGF-C protein was secreted from transfected cells as VEGFR-3 (Flt4) binding polypeptides of 30-32×103Mr and 22-23×103Mr which preferentially stimulated the autophosphorylation of VEGFR-3 in comparison with VEGFR-2 (KDR). In in situ hybridization, mouse VEGF-C mRNA expression was detected in mesenchymal cells of postimplantation mouse embryos, particularly in the regions where the lymphatic vessels undergo sprouting from embryonic veins, such as the perimetanephric, axillary and jugular regions. In addition, the developing mesenterium, which is rich in lymphatic vessels, showed strong VEGF-C expression. VEGF-C was also highly expressed in adult mouse lung, heart and kidney, where VEGFR-3 was also prominent. The pattern of expression of VEGF-C in relation to its major receptor VEGFR-3 during the sprouting of the lymphatic endothelium in embryos suggests a paracrine mode of action and that one of the functions of VEGF-C may be in the regulation of angiogenesis of the lymphatic vasculature.