bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental analysis of the control of expression of the homeobox-gene Msx-1 in the developing limb and face
Authors: Brown J. M. , Wedden S. E. , Millburn G. H. , Robson L. G. , Hill R. E. , Davidson D. R. , Tickle C. 
Published: April 2021

ABSTRACT
Mouse mesenchyme was grafted into chick embryos to investigate the control of mesenchymal expression of Msx-1 in the developing limb and face. In situ hybridization, using species-specific probes, allows a comparison between Msx-1 expression in the graft and the host tissue. The results show that Msx-1 expression in both limb-to-limb and face-to-face grafts corresponds closely with the level of Msx-1 expression in the surrounding chick mesenchyme. Cells in grafts that end up within the host domain of Msx-1 express the gene irrespective of whether they were from normally expressing, or non-expressing, regions. Therefore Msx-1 expression in both the developing limb and the developing face appears to be position-dependent. Mesenchyme from each of the three major facial primordia behaved in the same way when grafted to the chick maxillary primordium. Reciprocal grafts between face and limb gave a different result: Msx-1 expression was activated when facial mesenchyme was grafted to the limb but not when limb mesenchyme was grafted to the face. This suggests either that there are quantitative or qualitative differences in two local signalling systems or that additional factors determine the responsiveness of the mesenchyme cells.
A GATA family transcription factor is expressed along the embryonic dorsoventral axis in Drosophila melanogaster
Authors: Winick Jeffrey , Abel Ted , Leonard Mark W. , M. Michelson Alan , Chardon-Loriaux Isabelle , Holmgren Robert A. , Maniatis Tom , Engel James Douglas 
Published: April 2021

ABSTRACT
The GATA transcription factors are a family of C4 zinc finger-motif DNA-binding proteins that play defined roles in hematopoiesis as well as presumptive roles in other tissues where they are expressed (e.g., testis, neuronal and placental trophoblast cells) during vertebrate development. To investigate the possibility that GATA proteins may also be involved in Drosophila development, we have isolated and characterized a gene (dGATAa) encoding a factor that is quite similar to mammalian GATA factors. The dGATAa protein sequence contains the two zinc finger DNA-binding domain of the GATA class but bears no additional sequence similarity to any of the vertebrate GATA factors. Analysis of dGATAa gene transcription during Drosophila development revealed that its mRNA is expressed at high levels during early embryogenesis, with transcripts first appearing in the dorsal portion of the embryo just after cellularization. As development progresses, dGATAa mRNA is present at high levels in the dorsal epidermis, suggesting that dGATAa may be involved in determining dorsal cell fate. The pattern of expression in a variety of dorsoventral polarity mutants indicates that dGATAa lies downstream of the zygotic patterning genes decapentaplegic and zerknüllt.
Embryonic mesodermal defects in α5 integrin-deficient mice
Authors: Yang Joy T. , Rayburn Helen , Hynes Richard O. 
Published: April 2021

ABSTRACT
A loss of function mutation of the murineα5 integrin gene generated by gene targeting in embryonic stem cells is a recessive embryonic lethal. The mutant embryos start to show observable defects by day 9 of gestation and die around day 10-11. Theα5-null embryos have pronounced defects in posterior trunk and yolk sac mesodermal structures, suggesting a role forα5 β1 integrin in mesoderm formation, movement or function. However, the embryos progress significantly further than embryos null for fibronectin, for whichα5 β1 integrin is a receptor, suggesting the involvement of other fibronectin receptors. In vitro studies on cells derived from theα5-null embryos confirm that theα5 β1 integrin is not expressed on mutant cells and show that the mutant cells are able to assemble fibronectin matrix, form focal contacts, and migrate on fibronectin despite the complete absence of theα5 β1 fibronectin receptor integrin. All these functions have previously been thought to involve or requireα5 β1. The results presented show that these cellular functions involving fibronectin can proceed using other receptors.
A role for the mesoderm in endodermal migration and morphogenesis in Drosophila
Authors: Reuter Rolf , Grunewald Barbara , Leptin Maria 
Published: April 2021

ABSTRACT
The endodermal midgut arises from two primordia, the anterior midgut (AMG) primordium and the posterior midgut (PMG) primordium, which are separated by almost the entire length of the Drosophila embryo. To form the midgut, these two parts have to extend towards each other and to fuse laterally on both sides of the yolk. Shortly before and during that movement, AMG and PMG are arranged as mesenchymal cell masses, but later the midgut cells form an epithelium. We show that these two aspects of midgut development, migration of AMG and PMG and transition to an epithelium, depend on the mesoderm. The extension of the midgut primordia is achieved by cell migration along the visceral mesoderm which forms a continuous layer of cells within the germ band. In mutant embryos lacking the entire mesoderm or failing to differentiate the visceral mesoderm, AMG and PMG are formed but do not migrate properly. In addition, they fail to form an epithelium and instead either remain as compact cell masses anterior and posterior to the yolk (in twist and snail mutant embryos) or only occasionally wrap around the yolk before embryogenesis is completed (in tinmandeficient embryos). We conclude that the visceral mesoderm serves as a substratum for the migrating endodermal cells and that the contact between visceral mesoderm and endoderm is required for the latter to become an epithelium.
Cwnt-8C: a novel Wnt gene with a potential role in primitive streak formation and hindbrain organization
Authors: Hume Clifford R. , Dodd Jane 
Published: April 2021

ABSTRACT
To begin to examine the possibility that Wnt proteins act as cell signalling molecules during chick embryogenesis, PCR was used to identify Wnt genes expressed in Hensen’s node. We have identified a novel member of the Wnt gene family, Cwnt-8C, which is expressed prior to gastrulation in the posterior marginal zone, the primitive streak and Hensen’s node. Injection of Cwnt-8C mRNA into Xenopus embryos caused axis duplication and dorsalization of mesodermal tissues. During neurulation, Cwnt-8C is expressed transiently in a restricted domain of the prospective hindbrain neurectoderm that will give rise to rhombomere 4. This domain is defined prior to the formation of rhombomere boundaries and also precedes the up-regulation and restriction of expression of Hox B1 in the same region. Thus, Cwnt-8C is potentially involved in the regulation of axis formation and hindbrain patterning.
Developmental regulation of integrin expression at the time of implantation in the mouse embryo
Authors: Sutherland A. E. , Calarco P. G. , Damsky C. H. 
Published: April 2021

ABSTRACT
The trophectoderm layer of the mouse blastocyst differentiates at the late blastocyst stage to form the invasive trophoblast that mediates implantation of the embryo into the uterine wall. The first sign that trophoblast cells have developed an invasion-specific cell behavior appears about 10-15 hours after the embryo hatches from the zona pellucida, when the quiescent, nonadherent trophectoderm cells initiate protrusive activity and become adhesive to extracellular matrix. Our previous findings that trophoblast outgrowth on extracellular-matrix-coated substrata involves the integrin family of adhesion receptors (Sutherland, A. E., Calarco, P. G. and Damsky, C. H., 1988, J. Cell Biol. 106, 13311348), suggested that the onset of trophoblast adhesive and migratory behavior at the time of implantation may be due to changes in expression or distribution of integrin receptors. We have thus examined the mRNA and protein expression of individual integrin subunits during preand periimplantation development (E0E7.5). A basic repertoire of integrins, including receptors for fibronectin ( 5 1), laminin ( 6B 1) and vitronectin ( v 3), was expressed continuously throughout this period, whereas the expression of five other integrin subunits was developmentally regulated. The mRNA for three of these ( 2, 6A and 7) was first detected in the late blastocyst, coincident with endoderm differentiation and development of attachment competence. The mRNA for another ( 1) was not detected until after trophoblast outgrowth had begun, suggesting that its expression may be induced by contact with matrix. At E7.5, three of the temporally regulated integrins (α1, α6A, α7), all of which can form receptors for laminin, were detected only in the ectoplacental cone (differentiating trophoblast), and may thus play specific roles in trophoblast adhesion and/or differentiation.
Because laminin expression is upregulated in decidualized uterine stroma in response to the implanting embryo, we examined trophoblast-laminin interactions, using laminin fragments and integrin antibodies to determine which integrin receptors were involved. Trophoblast cells attached and spread on both the E8 and P1 fragments of laminin; however, the P1 binding site was cryptic in intact laminin. Interaction with P1 was RGDand αvβ3-dependent, whereas outgrowth on E8 was RGD-independent and not inhibited by antibodies to the laminin receptor α6β1, suggesting that α7β1 is the major trophoblast integrin E8 receptor. In contrast, migration of parietal endoderm cells on laminin was blocked by antibodies to α6, demonstrating that these two contemporaneous migratory cell populations have different modes of interaction with laminin. We conclude that developmental regulation of integrin expression appears to have functional significance for trophoblast invasion of the laminin-rich uterine stroma.
Structure of the zebrafish snail1 gene and its expression in wild-type, spadetail and no tail mutant embryos
Authors: Thisse C. , Thisse B. , Schilling T. F. , Postlethwait J. H. 
Published: April 2021

ABSTRACT
Mesoderm formation is critical for the establishment of the animal body plan and in Drosophila requires the snail gene. This report concerns the cloning and expression pattern of the structurally similar gene snail1 from zebrafish. In situ hybridization shows that the quantity of snail1 RNA increases at the margin of the blastoderm in cells that involute during gastrulation. As gastrulation begins, snail1 RNA disappears from the dorsal axial mesoderm and becomes restricted to the paraxial mesoderm and the tail bud. snail1 RNA increases in cells that define the posterior border of each somite and then disappears when somitic cells differentiate. Later in development, expression appears in cephalic neural crest derivatives. Many snail1-expressing cells were missing from mutant spadetail embryos and the quantity of snail1 RNA was greatly reduced in mutant no tail embryos. The work presented here suggests that snail1 is involved in morphogenetic events during gastrulation, somitogenesis and development of the cephalic neural crest, and that no tail may act as a positive regulator of snail1.
The ventral and posterior expression of the zebrafish homeobox gene eve1 is perturbed in dorsalized and mutant embryos
Authors: Joly Jean-Stéphane , Joly Claire , Schulte-Merker Stefan , Boulekbache Habib , Condamine Hubert 
Published: April 2021

ABSTRACT
We have identified and characterized zebrafish eve1, a novel member of the Drosophila even-skipped (eve) gene family. eve1 RNAs are expressed initially in late blastulae with a peak during the gastrula stage, at which time expression is confined to ventral and lateral cells of the marginal zone of the zebrafish embryo. Later, eve1 transcripts are located in the most posterior part of the extending tail tip. We show that LiCl, known to dorsalize Xenopus embryos, has the same effect in zebrafish, resulting in embryos with exaggerated dorsoanterior structures. In LiCl-treated embryos, eve1 transcripts are completely absent. eve1 is therefore a marker of ventral and posterior cells.
In the light of its ventroposterior expression domain, the localization of eve1 transcripts was analysed in spadetail (spt) and no tail (ntl), two mutants with abnormal caudal development. In sptb140 homozygous mutants, there is an accumulation of cells in the tail region, resulting from inadequate migratory behaviour of precursors to the trunk somites. These cells, in their abnormal environment, express eve1, emphasizing the correlation between ventroposterior position and eve1 expression. In homozygous mutant embryos for the gene ntl (the homologue of mouse Brachyury, originally called Zf-T), posterior structures are missing (M. E. Halpern, C. B. Kimmel, R. K. Ho and C. Walker, 1993; Cell In press). While mutant and wild-type embryos do not differ in their eve1 transcript distribution during gastrulation, eve1 expression is absent in the caudal region of mutant ntl embryos during early somitogenesis, indicating a requirement for ntl in the maintenance of eve1 expression during tail extension.
Our findings suggest that eve1 expression is correlated with a ventral and posterior cell fate, and provide first insights into its regulation.
Autosomal P[ovo
D1
] dominant female-sterile insertions in Drosophila and their use in generating germ-line chimeras
Authors: Chou Tze-Bin , Noll Elizabeth , Perrimon Norbert 
Published: April 2021

ABSTRACT
The ‘dominant female-sterile’ technique used to generate germ-line mosaics in Drosophila is a powerful tool to determine the tissue specificity (germ line versus somatic) of recessive female-sterile mutations as well as to analyze the maternal effect of recessive zygotic lethal mutations. This technique requires the availability of germ-line-dependent, dominant female-sterile (DFS) mutations that block egg laying but do not affect viability. To date only one X-linked mutation, ovoD1 has been isolated that completely fulfills these criteria. Thus the ‘DFS technique’ has been largely limited to the Xchromosome. To extend this technique to the autosomes, we have cloned the ovoD1 mutation into a P-element vector and recovered fully expressed P[ovoD1] insertions on each autosomal arm. We describe the generation of these P[ovoD1] strains as well as demonstrate their use in generating germ-line chimeras. Specifically, we show that the Gap1 gene, which encodes a Drosophila homologue of mammalian GTPase-activating protein, is required in somatic follicle cells for embryonic dorsoventral polarity determination.
A model system for cell adhesion and signal transduction in Drosophila
Authors: Peifer Mark , Orsulic Sandra , Pai Li-Mei , Loureiro Joseph 
Published: April 2021

ABSTRACT
Cells must cooperate and communicate to form a multicellular animal. Information about the molecules required for these processes have come from a variety of sources; the convergence between the studies of particular molecules by vertebrate cell biologists and the genes identified by scientists investigating development in Drosophila has been especially fruitful. We are interested in the connection between cadherin proteins that regulate cell-cell adhesion and the wingless/wnt-1 cell-cell signaling molecules controlling pattern formation during development. The Drosophila segment polarity gene armadillo, homolog of the vertebrate adherens junction protein |3-catenin, is required for both cell adhesion and wg signaling. We review what is known about wingless signaling in Drosophila, and discuss the role of cell-cell junctions in both cell adhesion and cell communication. We then describe the results of our preliminary structure-function analysis of Armadillo protein in both cell adhesion and wingless signaling. Finally, we discuss evidence supporting a direct role for Armadillo and adherens junction in transduction of wingless signal.
Cell fate specification in the developing Drosophila retina
Authors: Cagan Ross 
Published: April 2021

ABSTRACT
The developing Drosophila retina provides an excellent experimental system in which to address questions of cell fate choice and patterning. By focusing first on a detailed morphological description of eye development and more recently on the genes required for its development, the first steps have been taken toward understanding how these two aspects combine to direct cell fate in the retinal neuroepithelium. In addition, developing cell types emerge within the ommatidium in stereotyped patterns; these patterns may provide further chics regarding the mechanisms involved in cell fate choice. Previous reviews have focused on the detailed morphological description of, and molecules involved with, retinal development. This review focuses on current progress in understanding the role of several genes that play critical roles in retinal development, with special emphasis on how they define symmetric groups of cells within each ommatidium. In addition, the role of local cell interactions in directing cell fate is assessed.
The Src family of protein tyrosine kinases: regulation and functions
Authors: Courtneidge Sara A. , Fumagalli Stefano , Koegl Manfred , Superti-Furga Giulio , Twamley-Stein Geraldine M. 
Published: April 2021

ABSTRACT
Most of the nine members of the Src family of tyrosine kinases are restricted in their expression, often to cells of the haematopoietic lineage, while some, particularly Src, Fyn and Yes, are more ubiquitously expressed. We have been studying the functions of Src, Fyn and Yes in fibroblasts. We have shown that stimulation of quiescent fibroblasts with platelet-derived growth factor (I’DGF) causes Src, Fyn and Yes to become activated, and to associate transiently with the I’DGF receptor. To address the role of Src, Fyn and Yes in the response to I’DGF, we have used a dominant negative approach, in which cells were engineered to express catalytically inactive forms of Src kinases. These cells were unable to enter S phase in response to I’DGF, and we therefore conclude that Src family tyrosine kinases are required in order for the I’DGF receptor to transmit a mitogenic signal.
It has previously been shown that the kinase activity of Src is negatively regulated by phosphorylation of tyr 527 in its carboxy-terminal tail. A kinase, Csk, that phosphorylates tyr 527 has recently been identified. We expressed Src in yeast to test the model that phosphorylation of tyr 527 represses activity by promoting intramolecular association between the tail and the SH2 domain. Inducible expression of Src in .S’. pombe caused cell death. Co-expression of Csk counteracted this effect. Src proteins mutated in the SH2 domain were as lethal as wild-type Src, but were insensitive to Csk. We interpret these results in favour of an SH2 domain : phosphorylated tail interaction repressing Src activity. However, we have also found that Src molecules containing mutations in the SH3 domain are not regulated by Csk. suggesting that the SH3 domain also functions in the intramolecular regulation of Src activity.
The Drosophila EGF receptor homologue (DER) is required for Malpighian tubule development
Authors: Baumann Peter , Skaer Helen 
Published: April 2021

ABSTRACT
Defects in the locus Egfr, encoding the Drosophila EG F receptor homologue (DER), affect the development of the Malpighian tubules. They form as much shorter structures than in wild-type embryos, containing a reduced number of cells. The severity of this phenotype in seven alleles that we have analysed correlates with other embryonic defects caused by Egfr mutations. Interestingly the two pairs of tubules arc affected with different severity, with a greater reduction in cell number in the posterior pair than in the anterior. Temperature shift experiments indicate a role for this receptor in the regulation of tubule cell division. We also suggest that an additional role for DER in the allocation of cells to the tubule primordio is possible.
Molecular genetics of cell interactions in Arabidopsis
Authors: Pruitt Robert E. , Hülskamp Martin , Kopczak Steven D. , Ploense Sara E. , Schneitz Kay 
Published: April 2021

ABSTRACT
Many events in plant development are regulated by the interactions of neighboring cells. We are interested in determining what sorts of molecules act as signals and/or receptors in these interactions and how these mechanisms relate to those used in animals and fungi. We are presently working on two different types of systems to try to address this question. In one case we are starting at the molecular level and characterizing a family of receptor protein kinase genes which seem natural candidates for mediating cellular interactions. By analyzing the expression patterns of these genes as well as the phenotypes of transgenic plants bearing altered genes we hope to determine what roles these proteins play in plant development. In the second case we are starting from the organismic level and using genetics to identify genes essential to a whole range of cellular interactions which are required for proper male gametophyte development during reproduction. These interactions involve both recognition of the pollen grain to verify that it is from the correct species and also a transfer of positional information from the female to the male which first allows the pollen tube to determine the polarity of the stigmatic cell on which it has germinated and later provides ‘guidance* for the elongating tube to find the ovule.
The initial synthesis of haemoglobin in de-embryonated chick blastoderms.
Authors: Hell Anna 
Published: April 2021

ABSTRACT
Enormous progress has been made in the last few years towards the elucidation of the mechanism of protein synthesis, and great interest is centred on the steps leading to cellular differentiation and specific protein synthesis. We know that genetic information is passed on from one generation of cells to the next by deoxyribonucleic acid (DNA), and that this material directs all protein synthesis by the intermediary of the different types of ribonucleic acid (RNA).
The initial synthesis of haemoglobin in de-embryonated chick blastoderms.
Authors: Hell Anna 
Published: April 2021

ABSTRACT
The effects of fluorophenylalanine, bromodeoxyuridine, azaguanine, Actinomycin D and X-rays on the initial synthesis of haemoglobin in the de-embryonated chick blastoderm have been studied. Morphological observations were made in sections of treated tissues. Determinations of haemoglobin, total protein, RNA and DNA in the vascular area were made. None of these agents proved to inhibit haemoglobin synthesis specifically. With fluorophenylalanine, X-rays and Actinomycin D, the inhibition of haemo-globin production was the same whether treatment was begun at 1 or 10 somites, while with bromodeoxyuridine and azaguanine the inhibition was greater the earlier the substance was applied. Inhibition of haemoglobin, total protein and RNA synthesis were parallel in all cases. The results are discussed in relation to the time of synthesis of ‘messenger’ RNA for haemoglobin production, the time of appearance of globin and haemoglobin, and the probable effective life of the ‘messenger’ RNA.