bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clonal analysis of epiblast fate during germ layer formation in the mouse embryo
Authors: Lawson Kirstie A. , Meneses Juanito J. , Pedersen Roger A. 
Published: April 2021

ABSTRACTThe fate of cells in the epiblast at prestreak and early primitive streak stages has been studied by injecting horseradish peroxidase (HRP) into single cells in situ of 6.7-day mouse embryos and identifying the labelled descendants at midstreak to neural plate stages after one day of culture.Ectoderm was composed of descendants of epiblast progenitors that had been located in the embryonic axis anterior to the primitive streak. Embryonic mesoderm was derived from all areas of the epiblast except the distal tip and the adjacent region anterior to it: the most anterior mesoderm cells originated posteriorly, traversing the primitive streak early; labelled cells in the posterior part of the streak at the neural plate stage were derived from extreme anterior axial and paraxial epiblast progenitors; head process cells were derived from epiblast at or near the anterior end of the primitive streak. Endoderm descendants were most frequently derived from a region that included, but extended beyond, the region producing the head process: descendants of epiblast were present in endoderm by the midstreak stage, as well as at later stages. Yolk sac and amnion mesoderm developed from posterolateral and posterior epiblast. The resulting fate map is essentially the same as those of the chick and urodele and indicates that, despite geometrical differences, topological fate relationships are conserved among these vertebrates. Clonal descendants were not necessarily confined to a single germ layer or to extraembryonic mesoderm, indicating that these lineages are not separated at the beginning of gastrulation.The embryonic axis lengthened up to the neural plate stage by (1) elongation of the primitive streak through progressive incorporation of the expanding lateral and initially more anterior regions of epiblast and, (2) expansion of the region of epiblast immediately cranial to the anterior end of the primitive streak. The population doubling time of labelled cells was 7.5 h; a calculated 43 % were in, or had completed, a 4th cell cycle, and no statistically significant regional differences in the number of descendants were found. This clonal analysis also showed that (1) growth in the epiblast was noncoherent and in most regions anisotropic and directed towards the primitive streak and (2) the midline did not act as a barrier to clonal spread, either in the epiblast in the anterior half of the axis or in the primitive streak. These results taken together with the fate map indicate that, while individual cells in the epiblast sheet behave independently with respect to their neighbours, morphogenetic movement during germ layer formation is coordinated in the population as a whole.
Blastocoel expansion in the preimplantation mouse embryo: stimulatory effect of TGF-a and EGF
Authors: Dardik Alan , Schultz Richard M. 
Published: April 2021

ABSTRACT
The factors that promote blastocoel expansion in the preimplantation mouse embryo are not well understood. Since cAMP stimulates the rate of blastocoel expansion and, in other systems, EGF can elevate intracellular cAMP levels, we investigated the ability of either TGF-α or EGF to stimulate the rate of blastocoel expansion in the mouse. Picomolar concentrations of either TGF-α or EGF stimulate the rate of blastocoel expansion in a concentration-dependent manner, and the continual presence of the growth factor is required to observe the stimulatory effect. Neutralizing antibodies to either TGF-α or EGF inhibit the TGF-α or EGF stimulatory effect, respectively. An antibody to the extracellular domain of the EGF receptor stimulates the rate of blastocoel expansion in a concentration-dependent manner, whereas an antibody to the cytoplasmic domain of the receptor does not. Tyrphostin RG 50864, which inhibits the EGF receptor kinase activity, inhibits the TGF-α stimulation of the rate of blastocoel expansion in a concentration-dependent manner; the less active tyrphostin, RG 50862, has no inhibitory effect. In addition, TGF-α does not stimulate a precocious onset of cavitation. The stimulatory effect on the rate of blastocoel expansion elicited by TGF-α or EGF is observed in 70 % of the embryos (responders). Responders and nonresponders have similar intracellular ATP levels and cell numbers. Whereas TGF-α stimulates the uptake of [35S]methionine into the acid-soluble and acid-insoluble pools in the responders, TGF-α has no stimulatory effect in the nonresponders. Results of these experiments suggest that an initial differentiative function of the first mammalian epithelium -fluid transport -is sensitive to peptide growth factor modulation.
Laser microsurgery demonstrates that cytoplasmic strands anchoring the nucleus across the vacuole of premitotic plant cells are under tension. Implications for division plane alignment
Authors: Goodbody Kim C. , Venverloo Catharina J. , Lloyd Clive W. 
Published: April 2021

ABSTRACT
In epidermal cells of the plant Nautilocalyx lynchii, induced to divide by explantation, the nucleus undergoes a series of movements, on cytoplasmic strands, leading to construction of a division plane across the vacuole. In the early stage, the nucleus separates from the cortex, occupying an eccentric position in the cell, suspended across the vacuole by few thin strands. In the central stage, the nucleus occupies a central position anchored to the cortex by more numerous, thicker strands. Finally, the phragmosome forms as a coalescence of cytoplasmic strands across the cell, constituting the division plane within which mitosis and cytokinesis take place. The behaviour and alignment of these strands is therefore important since some are precursors of the division plane.
In a previous paper (Flanders et al (1990)J. Cell Biol. 110,1111 – 1122), it was pointed out that the alignment of cytoplasmic strands showed features common to a variety of elements under tension. That is, provided they are free to move relative to the cortex, strands radiating from the nucleus should tend to seek short rather than long routes to the cortex. In this way, strands under tension would move away from distant cell corners where two of the cell’s edges make a three-way junction with a neighbouring wall. This provides a basis for the avoidance of four-way junctions and the maintenance of three-way junctions which are a characteristic feature of most plant tissues. In addition, tensile elements such as soap bubble walls contact rigid surfaces perpendicularly. Perpendicular attachment of the cell plate to the side wall is embodied in Sachs’ rule of cell division and the existence of the premitotic strands in a state of tension would provide a basis for this rule.
In this study, laser microsurgery has been used to confirm that strands connecting the premitotic nucleus to the cortex are under tension since the severed ends retract immediately upon severance. However,. the response of the nucleus to the breaking of a cytoplasmic strand by laser depends upon the particular stage. The nucleus is most likely to move during the early stage when it is eccentrically placed and has few cytoplasmic strands. In the middle and phragmosomal stages the nucleus is more resistant. Computer-aided image reconstruction of anti-tubulin-labelled confocal sections indicates that the middle stage is characterised by thick microtubule (MT) bundles, which radiate from the nucleus and which seem to account for. the increasing stabilization of the nucleus. Although such strands are more difficult to sever with the laser, their ends still display elastic properties when cut. It is proposed that tension is likely to influence the alignment of strands as well as the position of the nucleus during division plane formation in vacuolated cells.
Developmental potential of parthenogenetic cells: role of genotype-specific modifiers
Authors: Fundele Reinald , Howlett Sarah K. , Kothary Rashmi , Norris Michael L. , Mills Walter E. , Surani M. Azim 
Published: April 2021

ABSTRACT
The developmental potential of parthenogenetic cells derived from different mouse strains was investigated by examining their distribution in various tissues of adult aggregation chimeras. Using GPI-1 allozymes as marker, no striking differences were observed between chimeras whose parthenogenetic cells were derived from activated oocytes isolated from females of different genetic backgrounds, (C57BL/6 × CBA/J) F1, CFLP, 129, and SWR. In all the combinations tested, parthenogenetic cells were consistently absent from skeletal muscle, but there were varying contributions to most other tissues. These results suggest that the maternal duplication of chromosomes containing imprinted gene(s) responsible for the systematic elimination of parthenogenetic cells from skeletal muscle, are not subject to a pronounced influence of genotype-specific modifiers. However, the contribution of parthenogenetic cells to the brain does appear to be influenced by strain background, since a marked improvement in the survival of CFLP, 129 and perhaps SWR parthenogenetic cells in chimeric brains was observed compared with F2 cells.
Establishment of rostrocaudal polarity in tectal primordium: engrailed expression and subsequent tectal polarity
Authors: Itasaki Nobue , Ichijo Hiroyuki , Hama Chihiro , Matsuno Toru , Nakamura Harukazu 
Published: April 2021

ABSTRACT
In the E4 (embryonic day 4) chick tectal primordium, engrailed expression is strong at the caudal end and gradually weakens toward the rostral end. We used quail-chick chimeric tecta to investigate how the caudorostral gradient of engrailed expression is established and whether it is correlated with the subsequent rostrocaudal polarity of tectal development.
To examine the positional value of the tectal primordium, we produced ectopic tecta in the diencephalon by transplanting a part of the mesencephalic alar plate heterotopically. In the ectopic tectum, the gradient of the engrailed expression reversed and the strength of the expression was dependent on the distance from the mes-diencephalon junction; the nearer the ectopic tectum was to the junction, the weaker the expression was. Consequently, the pattern of the engrailed expression in the host and ectopic tecta was nearly a mirror image, suggesting the existence of a repressive influence around the mes-diencephalon junction on the engrailed expression.
We examined cytoarchitectonie development in the ectopic tecta, which normally proceeds in a gradient along the rostrocaudal axis; the rostral shows more advanced lamination than the caudal. In contrast, the caudal part of the ectopic tecta (near to the mesdiencephalon junction) showed more advanced lamination than the rostral. In both the host and ectopic tecta, advanced lamination was observed where the engrailed expression was repressed, and vice versa.
Next we studied the correlation between engrailed expression and retinotectal projection from a view of plasticity and rigidity of rostrocaudal polarity in the tectum. We produced ectopic tecta by anisochronal transplantations between E3 host and E2 donor, and showed that there is little repressive influence at E3 around the mes-diencephalon junction. We then made chimeric double-rostral tectum (caudal half of it was replaced by rostral half of the donor tectum) or double-caudal tectum at E3. The transplants kept their original staining pattern in hosts. Consequently, the chimeric tecta showed wholly negative or positive staining of engrailed protein on the grafted side. In such tecta retinotectal projection pattern was disturbed as if the transplants retained their original position-specific characters.
We propose from these heterotopic and anisochronal experiments that the engrailed expression can be a marker for subsequent rostrocaudal polarity in the tectum, both as regards cytoarchitectonie development and retinotectal projection.
A G-string positive cis-regulatory element in the LpS1 promoter binds two distinct nuclear factors distributed non-uniformly in Lytechinus pictus embryos
Authors: Xiang Mengqing , Lu Szu-Yao , Musso Marco , Karsenty Gerard , Klein William H. 
Published: April 2021

ABSTRACT
The LpS1 α and β genes of Lytechinus pictus are activated at the late cleavage stage of embryogenesis, with LpS1 mRNAs accumulating only in lineages contributing to aboral ectoderm. We had shown previously that 762 bp of 5’ flanking DNA from the LpS1/β gene was sufficient for proper temporal and aboral ectoderm specific expression. In the present study, we identified a strong positive cis-regulatory element at −70 bp to −75 bp in the LpS1/β promoter with the sequence (G)6 and a similar, more distal cis-element at −721 bp to −726 bp. The proximal ‘G-string’ element interacted with two nuclear factors, one specific to ectoderm and one to endoderm/mesoderm nuclear extracts, whereas the distal G-string element interacted only with the ectoderm factor. The ectoderm and endoderm/mesoderm G-string factors were distinct based on their migratory behavior in electrophoretic mobility shift assays, binding site specificities, salt optima and EDTA sensitivity. The proximal G-string element shared homology with a binding site for the mammalian transcription factor IF1, a protein that binds to negative cis-regulatory elements in the mouse al(I) and a2(I) collagen gene promoters. Competition experiments using wild-type and mutant oligonucleotides indicated that the ectoderm G-string factor and IF1 have similar recognition sites. Partially purified IF1 specifically bound to an oligonucleotide containing the proximal G-string of LpS1/β. From our results, we suggest that the ectoderm G-string factor, a member of the G-rich DNA-binding protein family, activates the LpS1 gene in aboral ectoderm cells by binding to the LpS1 promoter at the proximal G-string site.
Specification of cell fate in the developing eye of Drosophila
Authors: Hafen Ernst , Basler Konrad 
Published: April 2021

Abstract
Determination of cell fate in the developing eye of Drosophila depends on cellular interactions. In the eye imaginai disc, an initially unpatterned epithelial sheath of cells, single cells are specified in regular intervals to become the R8 photoreceptor cells. Genes such as Notch and scabrous participate in this process suggesting that specification of ommatidial founder cells and the formation of bristles in the adult epidermis involve a similar mechanism known as lateral inhibition. The subsequent steps of ommatidial assembly involve a different mechanism: undetermined cells read their position based on the contacts they make with neighbors that have already begun to differentiate. The development of the R7 photoreceptor cell is best understood. The key role seems to be played by sevenless, a receptor tyrosine kinase on the surface of the R7 precursor. It transmits the positional information - most likely encoded by boss on the neighboring R8 cell membrane - into the cell via its tyrosine kinase that activates a signal transduction cascade. Two components of this cascade - Sos and sina - have been identified genetically, sina encodes a nuclear protein whose expression is not limited to R7. Constitutive activation of the sevenless kinase by overexpression results in the diversion of other ommatidial cells into the R7 pathway, suggesting that activation of the sevenless signalling pathway is sufficient to specify R7 development.
The regulation of motoneuron survival and differentiation by putative muscle-derived neurotrophic agents: neuromuscular activity and innervation
Authors: Houenou Lucien J. , Haverkamp Lanny J. , McManaman James L. , Oppenheim Ronald W. 
Published: April 2021

Abstract
The chronic blockade of neuromuscular activity is known to promote the survival of developing motoneurons in vivo in the chick, mouse and rat embryo. Increased survival in this situation may reflect an activity-dependent mechanism for the regulation of trophic factor production by target cells. To test this notion, we have examined motoneuron survival in vivo and choline acetyltransferase (ChAT) development in vitro following treatment of chick embryos and rat spinal cord cultures with partially purified skeletal muscle extracts derived from normally active, chronically paralyzed and aneural embryos, and from denervated postnatal chickens. Extracts from active and paralyzed chick embryos were equally effective in promoting motoneuron survival and ChAT activity. Aneural embryonic muscle extracts were slightly less effective in promoting motoneuron survival in vivo, but were not significantly different from control extracts in the in vitro ChAT assay. Denervated postnatal muscle extracts, however, were more effective in enhancing both motoneuron survival and ChAT activity. These data indicate that: (1) the promotion of motoneuron survival in vivo by activity blockade may not be mediated by an up-regulation of trophic factor synthesis in target cells; (2) postnatal innervation may regulate the production of putative muscle-derived neurotrophic factors; and (3) the synthesis or availability of trophic agents may be regulated differently in embryonic and postnatal muscle.
Origin of segmental identity in the development of the leech nervous system
Authors: Shankland Marty , Martindale Mark Q. , Nardelli-Haefliger Denise , Baxter Euan , Price David J. 
Published: April 2021

Abstract
The leech embryo develops its segmental body plan by means of a stereotyped cell lineage. Each hemilateral segment arises from a small set of embryonic blast cells via a comparable sequence of formative cell divisions, and for the most part, lineally homologous cells manifest similar patterns of differentiation in the various hemisegments. Nonetheless, some identified central neurons undergo segment-specific or laterally asymmetric patterns of neuropeptide expression and/or cell death. Certain aspects of this regional diversification result from competitive cell interactions which occur at the level of the postmitotic neuron. However, the neuron’s segmental identity is lineally determined, being inherited from its blast cell progenitor over several intervening rounds of mitosis. To learn more about the molecular basis of this phenomenon, we have isolated and begun to characterize leech homeobox genes which are related to the genes that govern segmental identity in other organisms.
Alternating patterns of cell surface properties and neural crest cell migration during segmentation of the chick hindbrain
Authors: Lumsden Andrew , Guthrie Sarah 
Published: April 2021

Abstract
The developing chick hindbrain is transiently divided into a series of repeating units or rhombomeres. Recent work has shown that an alternating periodicity exists both in the cell surface properties of rhombomeres and in the segmental origin of hindbrain neural crest cells. Experiments in which rhombomeres from different axial levels were confronted in the absence of an inter-rhombomere boundary showed that odd-numbered segments 3 and 5 combined without generating a boundary, as did even-numbered segments 2, 4 and 6. When rhombomeres originating from adjacent positions, or three rhombomeres distant from one another were combined, a new boundary was regenerated.
Mapping of the migration pathways of neural crest cells showed that odd-numbered and even-numbered rhombomeres share properties with respect to the production of neural crest cells. In the hindbrain region the neural crest is segregated into streams. Neural crest cells migrating from rhombomeres 1 and 2, rhombomere 4 and rhombomere 6 respectively populate distinct cranial nerve ganglia and branchial arches. In contrast, rhombomeres 3 and 5 are free of neural crest cells.
A nude mouse xenograft model of fetal intestine development and differentiation
Authors: Buono Raffaele Del , Fleming Kenneth A. , Morey Adrienne L. , Hall Peter A. , Wright Nicholas A. 
Published: April 2021

ABSTRACT
This report describes a novel in vivo model of intestinal differentiation. Fourteen day, undifferentiated fetal rat small intestine, stripped of the major part of its mesenchyme, suspended in a type I collagen gel and then xenografted into a nude mouse, undergoes small intestinal morphogenesis and cytodifferentiation. All four major epithelial lineages, namely Paneth, goblet, columnar and endocrine are present. Double-label nonisotopic in situ hybridization, employing biotinylated and digoxigenin-labelled whole rat DNA and whole mouse DNA probes, was performed to distinguish donor cells from host cell types. The outer longitudinal smooth muscle layer, and the major part of the lamina propria, including pericryptal fibroblasts, are of host mouse origin; the inner circular smooth muscle layer is of donor rat origin. Cells of the muscularis propria and lamina propria acquired smooth muscle α-actin, presumably under the influence of the donor endoderm. Furthermore, this xenograft develops a host vascular network, and cells with the morphological appearance of lymphocytes are present within the intestinal epithelium. The production of chemotactic factors by the endoderm is postulated because grafting of collagen gel alone results in a minimal invasion by stromal cells which do not express smooth muscle α-actin.
Disruption of pioneer growth cone guidance in vivo by removal of glycosyl phosphatidylinositol-anchored cell surface proteins
Authors: Chang Wesley S. , Serikawa Kyle , Allen Karen , Bentley David 
Published: April 2021

ABSTRACT
Cell surface proteins anchored to membranes via covalently attached glycosyl-phosphatidylinositol (GPI) have been implicated in neuronal adhesion, promotion of neurite outgrowth and directed cell migration. Treatment of grasshopper embryos with bacterial phosphatidylinositol-specific phospholipase C (PI-PLC), an enzyme that cleaves the GPI anchor, often induced disruptions in the highly stereotyped migrations of peripheral pioneer growth cones and afferent neuron cell bodies. In distal limb regions of embryos treated with PI-PLC at early stages of pioneer axon outgrowth, growth cones lost their proximal orientation toward the central nervous system (CNS) and turned distally. Pioneer growth cones in treated limbs also failed to make a characteristic ventral turn along the trochanter-coxa (Tr-Cx) segment boundary, and instead continued to grow proximally across the boundary. Treatment at an earlier stage of development caused pre-axonogenesis Cxi neurons to abandon their normal circumferential migration and reorient toward the CNS. None of these abnormal phenotypes were observed in limbs of untreated embryos or embryos exposed to other phospholipases that do not release GPI-anchored proteins. Incubation of embryos with PI-PLC effectively removed immunoreactivity for fasciclin I, a GPI-anchored protein expressed on a subset of neuronal surfaces. These results suggest that cell surface GPI-anchored proteins are involved in pioneer growth cone guidance and in pre-axonogenesis migration of neurons in the grasshopper limb bud in vivo.
Molecular analysis of the deletion mutants in the E homeotic complex of the silkworm Bombyx mori
Authors: Ueno Kohji , Hui Chi-Chung , Fukuta Masakazu , Suzuki Yoshiaki 
Published: April 2021

ABSTRACT
The E loci in Bombyx mori are expected to contain a homeotic gene complex specifying the identities of the larval abdominal segments. However, the molecular structure of this complex remains to be determined. We have started to analyze the structural changes in the E complex mutations. We used three newly isolated Bombyx homeobox genes as probes. These genes are probably homologues of the Ultrabiihorax (Ubx), ab-dominal-A (abd-A) and Abdominal-B (Abd-B) in the Drosophila bithorax complex, because the amino-acid sequences of the homeobox regions in these Bombyx genes are almost identical to those of Drosophila genes. We found that the Bombyx Ubx and abd-A genes are deleted in the Eca chromosome, and the Bombyx abd-A gene is deleted in the chromosome. From these results, we conclude that the Bombyx E complex consists of the Ubx, abd-A and possibly Abd-B genes, which may play similar roles to their homologues in the Drosophila bithorax complex.