bluuebunny/crossref_metadata_2025_split huggingface dataset:
The presence of hepatocyte growth factor in the developing rat
Authors: Defrances Marie C. , Wolf Helmut K. , Michalopoulos George K. , Zarnegar Reza 
Published: April 2021

ABSTRACT
Hepatocyte growth factor (HGF), a heparin-binding polypeptide mitogen, stimulates DNA synthesis in adult rat and human hepatocytes and in several other cells of epithelial origin. Recently, it was determined that scatter factor (SF), a protein that has been shown to cause the dispersion and migration of epithelial cells in culture, is identical to HGF. Moreover, the receptor for HGF was identified as the product of the proto-onco-gene, c-MET, a tyrosine kinase-containing transmem-brane protein. c-MET expression has been reported in a variety of adult and embryonic mouse tissues. Simi-larly, we and others have demonstrated that HGF is expressed in various adult rat and human tissues. In the present study, the tissue distribution of HGF during rat development was determined by immunohistochemistry using an HGF-specific polyclonal antiserum. Between day 12 and day 19, immunoreactivity for HGF was present in various locations such as hematopoietic cells, somites, squamous epithelium of the esophagus and skin, periventricular germinal matrix of the brain, bronchial epithelium, renal collecting tubules and chon-drocytes. After day 19, HGF immunoreactivity was also present in the pancreas, submaxillary glands and neural tissues. In addition to immunolocalizing HGF in tissue sections, bioreactive and immunoreactive HGF was extracted and purified from rat fetuses. Other studies demonstrated the presence of HGF and c-MET mRNA in total fetal rat, and in fetal and neonatal rat liver. Addition of purified HGF to fetal and neonatal rat liver cultures enriched for hepatocytes stimulated DNA syn-thesis up to six-fold over controls. These findings strongly suggest a pivotal role for this potent regulator of growth and development.
Ultrabithorax is a regulator of β3 tubulin expression in the Drosophila visceral mesoderm
Authors: Hinz Uwe , Wolk Andrea , Renkawitz-Pohl Renate 
Published: April 2021

ABSTRACT
β3 tubulin expression accompanies the specification and differentiation of the Drosophila mesoderm. The genetic programs involved in these processes are largely unknown. Our previous studies on the regulation of the β3 tubulin gene have shown that upstream sequences guide the expression in the somatic musculature, while regulatory elements in the first intron are necessary for expression in the visceral musculature. To further analyse this mode of regulation, which reflects an early embryonic specification program, we undertook a more detailed analysis of the regulatory capabilities of the intron. The results reveal not only a certain degree of redundancy in the cis-acting elements, which act at different developmental stages in the same mesodermal derivatives, but they also demonstrate in the visceral mesoderm, which forms a continuous epithelium along the body axis of the embryo, an early action of regulators guiding gene expression along the anterior-posterior axis of the embryo: an enhancer element in the intron leads to expression in a subdomain restricted along the anterior-posterior axis. This pattern is altered in mutants in the homeotic gene Ultrabithorax (Ubx), whereas ectopic Ubx expression leads to activity of the enhancer in the entire visceral mesoderm. So this element is likely to be a target of homeotic genes, which would define the 3 tubulin gene as a realisator gene under the control of selector genes.
Expression of the genes for TGF α, EGF and the EGF receptor during early pig development
Authors: Vaughan Tristan J. , James Peter S. , Pascall John C. , Brown Kenneth D. 
Published: April 2021

ABSTRACT
Expression of mRNA for transforming growth factoralpha (TGF-α), epidermal growth factor (EGF) and the epidermal growth factor receptor (EGF-R) during early pig development was evaluated by reverse transcription-PCR. In the unfertilised pig oocyte, maternal transcripts for EGF, but not for TGF α or the EGF-R, were detected. Pig conceptuses were analysed at days 7, 8, 10, 12, 15, 17, 18 and 22 of pregnancy. EGF-R mRNA was detected at all stages of conceptus development analysed. Interestingly, TGF α mRNA was expressed by the developing blastocyst only at days 8, 10 and 12 of pregnancy, with the highest levels apparent at day 10. In contrast, EGF mRNA was first expressed by the postelongation conceptus at around day 15 of pregnancy with levels continuing to increase up to day 22. In the day-18 and day-22 conceptuses, this EGF message was shown to be primarily a product of the embryo-amnion and not the placental membranes. Furthermore, EGF was immunolocalised in the day-22 embryo to the developing lung bud, gut loop and amnion. In summary, the expression pattern of TGF α mRNA during early pig development is coincident with the onset of blastocyst elongation and suggests a possible role for TGF α during this period of cellular remodelling. The temporal and spatial expression of EGF mRNA and protein suggests a possible involvement for EGF in the establishment of the early organ systems.
An X-linked human collagen transgene escapes X inactivation in a subset of cells
Authors: Wu Hong , Fässler Reinhard , Schnieke Angelika , Barker Douglas , Lee Kwang-Ho , Chapman Verne , Francke Uta , Jaenisch Rudolf 
Published: April 2021

ABSTRACT
Transgenic mice carrying one complete copy of the human 1(I) collagen gene on the X chromosome (HucII mice) were used to study the effect of X inactivation on transgene expression. By chromosomal in situ hybridization, the transgene was mapped to the D/E region close to the Xce locus, which is the controlling element. Quantitative RNA analyses indicated that transgene expression in homozygous and heterozygous females was about 125% and 62%, respectively, of the level found in hemizygous males. Also, females with Searle’s translocation carrying the transgene on the inactive X chromosome (Xi) expressed about 18% transgene RNA when compared to hemizygous males. These results were consistent with the transgene being subject to but partially escaping from X inactivation. Two lines of evidence indicated that the transgene escaped X inactivation or was reactivated in a small subset of cells rather than being expressed at a lower level from the Xi in all cells, (i) None of nine single cell clones carrying the transgene on the Xi transcribed transgene RNA. In these clones the transgene was highly methylated in contrast to clones carrying the transgene on the Xa. (ii) In situ hybridization to RNA of cultured cells revealed that about 3% of uncloned cells with the transgene on the Xi expressed transgene RNA at a level comparable to that on the Xa. Our results indicate that the autosomal human collagen gene integrated on the mouse X chromosome is susceptible to X inactivation. Inactivation is, however, not complete as a subset of cells carrying the transgene on Xi expresses the transgene at a level comparable to that when carried on Xa.
A receptor protein tyrosine kinase implicated in the segmental patterning of the hindbrain and mesoderm
Authors: Nieto M. Angela , Gilardi-Hebenstreit Pascale , Charnay Patrick , Wilkinson David G. 
Published: April 2021

ABSTRACT
Pattern formation in the hindbrain and paraxial mesoderm of vertebrates occurs by the formation of a series of repeated segments. These processes of segmentation appear different at the morphological level, since hindbrain segments, the rhombomeres, form by the subdivision of the neural epithelium into compartments, whereas the mesodermal somites form by the sequential aggregation of mesenchymal cells into epithelial balls. Previous studies have implicated genes encoding transcription factors in the development of hindbrain segments, but nothing is known of genes involved in the formation of somites. Cellular interactions and signal transduction must be an important aspect of hindbrain segmentation, so we have screened for tyrosine kinases expressed in rhombomere-restricted patterns in the developing mouse embryo. We have identified a receptor protein tyrosine kinase, Sek, that has high relative levels of expression in rhombomeres 3 and 5. This alternating pattern is established coincidentally, both spatially and temporally, with the expression of Krox-20, a zinc-finger gene expressed prior to the morphological formation of rhombomeres. In addition, Sek expression occurs in several other developing tissues, including a dynamic regulation in the developing forebrain, spinal cord, early mesoderm and anterior presomitic mesoderm (segmental plate). The latter expression occurs in two stripes that correlate with, and presage, the formation of somites. Sek expression initially occurs throughout the presumptive somite, then becomes restricted anteriorly, and finally is down-regulated as the definitive somite is formed. These data suggest that despite the morphological differences in the segmentation of the hindbrain and mesoderm, Sek is involved in the segmental patterning of both of these tissues.
Notch2: a second mammalian Notch gene
Authors: Weinmaster Gerry , Roberts Veronica J. , Lemke Greg 
Published: April 2021

ABSTRACT
Notch is a cell surface receptor that mediates a wide variety of cellular interactions that specify cell fate during Drosophila development. Recently, homologs of Drosophila Notch have been isolated from Xenopus, human and rat, and the expression patterns of these ver- tebrate proteins suggest that they may be functionally analogous to their Drosophila counterpart. We have now identified a second rat gene that exhibits substantial nucleic and amino acid sequence identity to Drosophila Notch. This gene, designated Notch2, encodes a protein that contains all the structural motifs characteristic of a Notch protein. Thus, mammals differ from Drosophila in having more than one Notch gene. Northern and in situ hybridisation analyses in the developing and adult rat identify distinct spatial and temporal patterns of expression for Notch1 and Notch2, indicating that these genes are not redundant. These results suggest that the great diversity of cell-fate decisions regulated by Notch in Drosophila may be further expanded in vertebrates by the activation of distinct Notch proteins.
Xenopus Hox-2 genes are expressed sequentially after the onset of gastrulation and are differentially inducible by retinoic acid
Authors: Dekker Erik-Jan , Pannese Maria , Houtzager Erwin , Timmermans Ans , Boncinelli Edoardo , Durston Antony 
Published: April 2021

ABSTRACT
In this paper, we review experiments to characterise the developmental expression and the responses to all-trans retinoic acid (RA) of six members of the Hox-2 complex of homeobox-containing genes, during the early development of Xenopus laevis. We showed that the six genes are expressed in a spatial sequence which is colinear with their putative 3′ to 5′ chromosomal sequence and that five of them are also expressed rapidly after the beginning of gastrulation, in a 3′ to 5′ colinear temporal sequence. The sixth gene (Xhox2.9) has an exceptional spatial and temporal expression pattern. The six genes all respond to RA by showing altered spatiotemporal expression patterns, and are also RA-inducible, the sequence of the magnitudes of their RA responses being colinear with their 3′ to 5′ chromosomal sequence, and with their spatial and temporal expression sequences. Our data also reveal that there is a pre-existing anteroposterior polarity in the embryo’s competence for a response to RA. These results complement and extend previous findings made using murine and avian embryos and mammalian cell lines. They suggest that an endogenous retinoid could contribute to positional information in the early Xenopus embryo.
Gastrulation and the evolution of development
Authors: Wolpert L. 
Published: April 2021

ABSTRACT
The original eukaryotic cell may have possessed the key processes necessary for metazoan development -cell differentiation, patterning and motility - and these are present in the cell cycle. Protozoa also possess key patterning processes. It remains a problem as to why there should be two main modes of development -one based on asymmetric cell division and the other on cellular interactions. The latter may be related to asexual reproduction.
The morphogenetic movements of gastrulation -as distinct from specifying the body plan -are highly conserved in a wide variety of organisms. This may reflect the requirement for patterning being specified in two dimensions, sheets of cells, and a third dimension being created by cell infolding.
The origin of the gastrula can be accounted for in terms of Haeckel’s gastrea theory -an early metazoan resembling the gastrula. Gastrulation in Cnidaria may resemble the primitive condition but there is nevertheless considerable diversity. While this may reflect, for example, yolkiness, it seems that there is little selection on developmental processes other than for reliability.
Thus it is possible that the embryo is privileged with respect to selection and this may help account for the evolution of novel processes like the origin of the neural crest.
Reliability is the key demand made on development This may be provided by apparent redundancy. Since many developmental processes involve switches and spatial patterning reliability is provided by parallel buffering mechanisms and not by negative feedback.
Lighting the fuse at fertilization
Authors: Whitaker Michael , Swann Karl 
Published: April 2021

ABSTRACT
In most deuterostome eggs, fertilization is marked by an abrupt and transient increase in intracellular calcium concentration The transient takes the form of a propagating wave and is the signal for the onset of development For those interested in cell signalling, the two obvious questions to ask are how the wave is initiated and how it propagates through the egg cytoplasm Answers have come largely from experiments in frog, hamster, mouse and sea urchin eggs One explanation of signal transduction at fertilization makes an analogy with transmembrane signalling in somatic cells, where a family of G-protein-linked receptors pass activating signals across the plasma membrane Another, older idea is that it is the fusion of sperm and egg that is responsible for detonating the calcium explosion at fertilization We discuss the relative merits of the two ideas Both are plausible; the creative tension between them has led to experiments that broaden our view of signal transduction at fertilization
Mice homozygous for a targeted disruption of the proto-oncogene int-2 have developmental defects in the tail and inner ear
Authors: Mansour Suzanne L. , Goddard Judy M. , Capecchi Mario R. 
Published: April 2021

ABSTRACT
We derived mice that carry a targeted insertion of a neor gene in the int-2 (Fgf-3) proto-oncogene coding sequences. The mutation was found to be recessive and mice that were homozygous for the insertion did not often survive to adulthood. The mutant mice had defects in the development of the tail and inner ear that could be correlated with disruption of int-2 expression in the posterior primitive streak and hindbrain or otic vesicle. While the tail phenotype was 100% penetrant, we found that the inner ear phenotype had reduced penetrance and variable expressivity. The variable expressivity could not be attributed to variability in the genetic background of the mutant allele or to leaky expression from the mutant allele. Thus, we conclude that even in a uniform genetic background, stochastic variation in the expression of a developmental circuit can result in dramatic differences in phenotypic consequences.
Regulation of wingless transcription in the Drososphila embryo
Authors: Ingham P. W. , Hidalgo A. 
Published: April 2021

ABSTRACT
The segment polarity gene wingless (wg) is expressed in a complex pattern during embryogenesis suggesting that it plays multiple roles in the development of the embryo. The best characterized of these is its role in cell pattening in each parasegment, a process that requires the activity of other segment polarity genes including patched (ptc) and hedgehog (hh). Here we present further evidence that ptc and hh encode components of a signal transduction pathway that regulate the expression of wg transcription following its activation by pair-rule genes. We also show that most other aspects of wg expression are independent of this regulatory network.
A different type of amphibian mesoderm morphogenesis in Ceratophrys ornata
Authors: Purcell Susan M. , Keller Ray 
Published: April 2021

ABSTRACT
Ceratophrys ornata, the Argentinean horned frog, has a significantly different pattern of early morphogenesis than does the most studied amphibian, Xenopus laevis. Time-lapse videomicroscopy, scanning electron microscopy, histological sections and lineage tracers have shown that, in C. ornata, some prospective noto-chord, somite and tailbud mesoderm cells leave the sur-face epithelium of the archenteron by ingression. After gastrulation, SEM reveals cells with constricted apices and a bottle shape in three zones on the archenteron roof and in a fourth zone around the blastopore. Prospective somitic tissue ingresses first from two lateral zones, followed by ingression of prospective notochord from the medial zone and tailbud mesoderm from the circumblastoporal zone. This is unlike X. laevis, in which no cells with constricted apices are present on the dorsal surface of the archenteron, nor do any cells ingress into the deep mesodermal layers from the surface layer.
Ultrastructural analysis of Drosophila ovarian follicles differing in yolk polypeptide (yps) composition
Authors: Giorgi F. , Lucchesi P. , Morelli A. , Bownes M. 
Published: April 2021

ABSTRACT
Drosophila ovarian follicles were examined ultrastructurally to study the vesicular traffic in the cortical ooplasm. The endocytic pathway leading to the production of yolk spheres was visualized following in vivo or in vitro exposure to peroxidase. The Golgi apparatus and the yolk spheres of wild-type ovarian follicles were preferentially labelled by fixation with osmium zinc iodide (OZI). Labelling of wild-type ovarian follicles was compared to that of several mutant follicles-L186/Basc, fs(2)A17 and ap4-which are defective in vitellogenesis. In these mutants, the Golgi apparatus and the vesicles nearby were either scantly labelled or not labelled at all. In oocytes from flies homozygous for the gene fs(1)1163, the Golgi apparatus was labelled as in the controls, but no yolk spheres appeared to be labelled with OZI at any of the developmental stages.
In several Drosophila strains, the pattern of OZI label in the cortical ooplasm was seen to vary in relation to the number of yp structural genes. In starved Drosophila females, OZI labelling of the cortical ooplasm appeared restricted to the Golgi apparatus and to an extended tubular network. A similar labelling pattern was also detected in in vitro cultured vitellogenic follicles. Refeeding, topical application of juvenile hormone analogue to starved females or hormone addition to the culture medium, all caused the yolk spheres to become labelled with OZI and to incorporate peroxidase. These observations prove that impairing endocytic uptake by either mutation or lack of juvenile hormone prevents fusion of coated vesicles and tubules with the yolk spheres and leads them instead to form an intermediate cell compartment with Golgi-derived vesicles.
The in situ localization of tenascin splice variants and thrombospondin 2 mRNA in the avian embryo
Authors: Tucker Richard P. 
Published: April 2021

ABSTRACT
Tenascin and thrombospondin belong to the growing family of extracellular matrix glycoproteins believed to have an anti-adhesive function during development. Immunohistochemistry has been used to identify these proteins in the developing central nervous system, in the matrix surrounding peripheral neurons, and in connective tissue. The antibodies used in most of these studies, however, could not distinguish between different splice variants (tenascin) nor different genetic forms (thrombospondin). For this reason, we used the reverse transcriptase polymerase chain reaction to generate DNA probes that are specific to the transcripts of high Mr tenascin and thrombospondin 2. These probes were then used for an in situ hybridization study to determine the cellular origins of specific tenascin and thrombospondin forms throughout the development of the chick. The mRNA encoding high Mr tenascin was found associated with motile cells and in tissues undergoing dynamic modeling: migrating glia, epithelial glia used as a substratum for migrating neurons, the growing tips of lung buds, and during osteogenesis. In contrast, the mRNAs of low Mr tenascin were concentrated in areas of cartilage deposition and chondrocyte proliferation. Thrombospondin 2 mRNA was not detected in the developing central nervous system at any time during development by in situ hybridization. In contrast, it was found in embryonic mesenchyme, perichondrium, epimysium, and endothelial cells. Thrombospondin 2 mRNA was detected in poly(A) RNA isolated from embryonic spinal cord and cerebellum by polymerase chain reaction, though it was not detected in poly(A) RNA from the avascular retina. Thus, thrombospondin 2 mRNA may be present in the developing brain at low levels in endothelial cells or blood cells. These data support the notion that tenascin splice variants have distinct roles during development, and that thrombospondin 2 is more likely to be playing a role associated with the morphogenesis of connective tissue than neuronal development.
Postembryonic patterns of expression of cut, a locus regulating sensory organ identity in Drosophila
Authors: Blochlinger Karen , Jan Lily Yeh , Jan Yuh Nung 
Published: April 2021

ABSTRACT
The cut locus is both necessary and sufficient to specify the identity of a class of sensory organs in Drosophila embryos. It is also expressed in and required for the development of a number of other embryonic tissues, such as the central nervous system, the Malpighian tubules and the tracheal system. We here describe the expression of cut in the precursors of adult sensory organs. We also show that cut is expressed in cells of the prospective wing margin and correlate the wing margin phenotype caused by two cut mutations with altered cut expression patterns. Finally, we observe cut-expressing cells in other adult tissues, including Malpighian tubules, muscles, the central nervous system and ovarian follicle cells.
Non-overlapping expression of CRBP I and CRABP I during pattern formation of limbs and craniofacial structures in the early mouse embryo
Authors: Gustafson Anne-Lee , Dencker Lennart , Eriksson Ulf 
Published: April 2021

ABSTRACT
Retinoic acid (RA), a physiological metabolite of retinol (vitamin A), is thought to be of importance for pattern formation in the developing embryo. However, the mechanism by which RA is generated, as well as the site of its formation in the developing embryo, is still unknown. In this paper, we show that radiolabelled retinol, administered to pregnant mice, is accumulated in specific locations in the embryos. As revealed by immunohistochemistry using antibodies to cellular retinol-binding protein I (CRBP I), retinol accumulates in regions of the embryo expressing CRBP I. In limbs and craniofacial structures, CRBP I expression and retinol accumulation was seen in endoderm and surface ectoderm. Most mesenchymal cells of the limbs and craniofacial structures did not express detectable levels of CRBP I but instead expressed cellular retinoic acid-binding protein I (CRABP I). Previous results have demonstrated that CRABP I is involved in accumulation of RA in the embryo. Thus, the spatially closely related but non-overlapping domains of expression of CRBP I and CRABP I suggests a role of a retinol/RA pathway in epithelial-mesenchymal interactions during pattern formation of limbs and of craniofacial structures.