pinecone/core-2020-05-10-deduplication huggingface dataset:
Control of Cell Division in the Root Epidermis ofArabidopsis thaliana

AbstractThe formation of the root epidermis inArabidopsis thalianaprovides a simple model to study mechanisms underlying patterning in plants. In this paper we have analyzed the relationships between cell fate specification and the pattern of cell division that occur in the root epidermis. Using clonal analysis, the two cell types of the developing root epidermis, trichoblasts and atrichoblasts, were distinguished by different rates of cell division, highest in trichoblasts. This character appears to be dependent onTTGwhich controls epidermal cell fate specification. The ability of epidermal cells to undergo longitudinal divisions which are involved in the control of the radial symmetry was shown to be controlled in a cell-specific manner byTTG.The control of the rate and the orientation of cell division in the root meristem epidermal layer thus appear to be under the control of cell fate specification mechanisms
Late Specification of Veg1Lineages to Endodermal Fate in the Sea Urchin Embryo

AbstractSingle blastomeres of the sixth-cleavage veg1and veg2tiers ofStrongylocentrotus purpuratusembryos were labeled with DiI lineage tracer, and the disposition of the progeny was followed through the blastula and gastrula stages in order to determine their respective endodermal and ectodermal contributions. In the endoderm of postgastrula embryos, veg1-derived cells constituted nearly all of the prospective hindgut and about half of the prospective midgut, while veg2-derived cells made up the prospective foregut and half the midgut. Oral veg1clones consistently contributed more cells to endoderm than aboral veg1clones. Oral veg1clones extended along the archenteron up to the foregut region, while aboral veg1clones contributed only small numbers of hindgut cells but large patches of ectoderm cells that extended out to the prospective larval vertex. The oral/aboral asymmetry in veg1allocations was also demonstrated using chimeric embryos, the animal halves of which were labeled with a rhodamine-dextran. Lineages expressing the vegetal plate markerEndo16were more precisely determined by combining lineage tracer injection with whole-mountin situhybridization.Endo16expression was found in all cells that are going to participate in gastrulation. Recruitment of new cells to theEndo16domain occurs in advance of the actual invagination of those cells. During the blastula stagesEndo16expression expands radially until all cells in the veg2lineages express this gene. The first phase of gastrulation, including the normal buckling of the vegetal plate and primary invagination of the archenteron, involves only theEndo16-expressing cells of the veg2lineages. As the archenteron begins to elongate, marking the onset of the second phase of gastrulation, there is an asymmetric expansion ofEndo16into the veg1-derived cells that will contribute to the hindgut and midgut in accordance with lineage tracing observations. The results indicate a relatively late specification of veg1-derived cells, resulting in late recruitment to the periphery of the vegetal plate territory as gastrulation proceeds. Differential recruitment of veg1-derived cells on the oral side of the embryo introduces an oral bias to gastrulation by disproportionately increasing the number of cells on the oral side that are competent to participate in gastrulation
Requirement for Microtubules in New Membrane Formation during Cytokinesis ofXenopusEmbryos

AbstractIn cleavingXenopuseggs, exposure to nocodazole or cold shock prevents the addition of new plasma membrane to the cleavage plane and causes furrows to recede, suggesting a specific role for microtubules in cytokinesis. Whole-mount confocal immunocytochemistry reveals a ring of radially arranged, acetylated microtubule bundles at the base of all advancing cleavage furrows, from the first cleavage through the midblastula stage. We hypothesize that this novel microtubular structure is involved in transporting maternal stores of membrane in the subcortex to a site of membrane addition near the leading edge of the furrow
A Null Mutation in Basigin, an Immunoglobulin Superfamily Member, Indicates Its Important Roles in Peri-implantation Development and Spermatogenesis

AbstractBasigin is a highly glycosylated transmembrane protein with two immunoglobulin-like domains. We generated mutant mice lacking the basigin gene (Bsg) by gene targeting.Bsg(−/−) embryos developed normally during preimplantation stages. However, the majority ofBsg(−/−) embryos died around the time of implantation. At this time, basigin mRNA was strongly expressed in the trophectoderm, embryo proper, and uterine endometrium ofBsg(+/+) mice. These results suggest that basigin is involved in intercellular recognition during implantation. Embryos which survived the critical period yieldedBsg(−/−) mutant mice. Half of the mutant mice died before 1 month after birth, due to interstitial pneumonia. The surviving adult mutant mice were small and sterile. Spermatogenesis was arrested in the mutant mice. Most of the spermatocytes in theBsg(−/−) mouse were arrested and degenerated at the metaphase of the first meiosis, and only a small number differentiated to step 1 spermatids. In the female mutants, the ovaries and genital tract were morphologically normal, and the defect was probably in the capability of implantation of the uterus. In conclusion, basigin is an important cell-surface molecule involved in early embryogenesis and reproduction
Neural Crest Induction by Xwnt7B in Xenopus

AbstractNeural patterning occurs soon after neural induction during early development. In Xenopus, several caudalizing factors transform anterior neural to posterior neural tissue at the open neural plate stages, while other factors are responsible for setting up mediolateral polarity which becomes the dorsoventral (D–V) axis after neural tube closure. Many Wnt ligands are expressed in the neural tube in distinct anteroposterior (A–P) and D–V domains, implying a function in neural patterning. Here we report the cloning of a full-length Xenopus Wnt7B gene. Xwnt7B induces neural crest markers Xslug and Xtwist in ectodermal explants coinjected with neural inducer noggin and in ectodermal cells neuralized by dissociation.In vivo,Xwnt7B expands the Xtwist expression domain when injected in the animal pole. Our results suggest that Wnt members are involved in dorsoventral patterning of the neural tube
Mutations of α Spectrin andlabialBlock Cuprophilic Cell Differentiation and Acid Secretion in the Middle Midgut ofDrosophilaLarvae

AbstractMutations inDrosophilaα spectrin cause larval lethality and defects in cell shape and adhesion (J. Leeet al.,1993,J. Cell Biol.123, 1797–1809). Here we examined the effects of two lethal α spectrin alleles (α-specrg41and α-specrg35) on development and function of the larval midgut. Homozygous null α-specrg41-mutant larvae exhibited a striking defect in middle midgut acidification. In contrast, many homozygous α-specrg35mutants were capable of acidification, indicating partial function of the truncated α-specrg35product. Acidification was also blocked by a mutation in thelabialgene, which is required for differentiation of cuprophilic cells in the midgut, suggesting that these cells secrete acid. We found that two isoforms of spectrin (αβ and αβH) are segregated within the basolateral and apical domains of cuprophilic cells, respectively. The most conspicuous defect in cuprophilic cells fromlabialand α spectrin mutants was in morphogenesis of the invaginated apical domain, although basolateral defects may also contribute to the acidification phenotype. Acid secretion in vertebrate systems is thought to involve the polarized activities of apical proton pumps and basolateral anion exchangers, both of which interact with spectrin. We propose that the α-specrg41mutation inDrosophilainterferes with the polarized activities of homologous molecules that drive acid secretion in cuprophilic cells
Defective Development of the Embryonic Liver in N-myc-Deficient Mice

AbstractThe mechanisms involved in the formation and the differentiation of the liver remain unclear despite extensive studies. To investigate these events in mouse hepatic development, we have taken advantage of the N-mycmutant mouse line which exhibits abnormal liver development. N-mycmutant embryos die between 11.5 and 12.5 days postcoitum most probably from heart failure. In the present study, we report that at 11.5 days of gestation, extensive apoptosis restricted to the hepatocytes occurred in N-mycmutant liver when compared to wild-type samples. Moreover, the number of hematopoietic cells is reduced in the mutant liver. During early liver organogenesis, the N-mycgene is expressed in tissues involved in the induction and the differentiation of the hepatocytes. At 11.5 days postcoitum, both c-mycand N-mycgenes are expressed in the liver. While c-mycis expressed at a high level in the organ per se, N-mycexpression is mostly confined to the peripheral layer of the liver which will generate the Glisson's capsule. Taken together, the expression pattern of N-mycin the liver and the specific apoptosis of hepatocytes observed in N-mycmutants indicate that N-mycis required for hepatocyte survival and suggest that it is involved in the genetic cascade leading to normal liver development
Endogenous and Ectopic Expression ofnogginSuggests a Conserved Mechanism for Regulation of BMP Function during Limb and Somite Patterning

AbstractThe genenoggin,originally cloned inXenopus,encodes a secreted factor expressed in the Spemann organizer, where it functions to oppose the ventralizing influence of bone morphogenetic proteins (BMPs). Noggin protein acts by binding directly to BMPs, thereby preventing them from interacting with their receptors. Here we describe the pattern of expression of the chickennoggingene during somite and limb development, two tissues in which BMPs have been postulated to play essential patterning roles. We find thatnogginis expressed in dynamic restricted patterns consistent with an important role in the modulation of BMP signaling. Using a replication competent retrovirus we have ectopically expressednogginin developing somitic and limb bud mesoderm and observed phenotypes consistent with complete block of BMP activity. This includes suppression of lateral somite differentiation and, in the limb, complete inhibition of chondrogenesis and local suppression of programmed cell death. In addition, we find that ectopicnogginexpression in the limb has no effect on anteroposterior limb pattern, suggesting that BMPs are unlikely to play a significant role in this process. Taken together, our results indicate thatnogginis a key regulator of vertebrate limb and somite patterning and suggest that the antagonistic Noggin–BMP interaction is a widely used mechanism to modulate BMP signaling during multiple inductive events in vertebrate embryogenesis
Abrogation of Smad3 and Smad2 or of Smad4 Gene Expression Positively Regulates Murine Embryonic Lung Branching Morphogenesis in Culture

AbstractSmad genes are recently identified intracellular effectors for receptor signaling in the BMP/activin/TGF-β pathway. Since TGF-β ligands are known to inhibit embryonic lung branching morphogenesis, we tested the hypothesis that Smad genes negatively regulate lung organogenesis. Antisense oligodeoxynucleotides were designed to attenuate Smad3 and Smad2 gene expression in embryonic (E11) mouse lungs over 4 days in culture. Endogenous Smad3 and Smad2 mRNA levels were suppressed by 97 and 91%, respectively, in cultured embryonic lungs when antisense oligodeoxynucleotide (40 μM) to Smad was added, compared to scrambled and sense sequence controls. The corresponding Smad3 and Smad2 protein amounts were also decreased respectively by 86 and 90% in lungs treated with Smad3 and Smad2 antisense oligodeoxynucleotide. Phenotypically, Smad antisense oligodeoxynucleotides resulted in a concentration-dependent increase in lung branching: embryonic lung branching was stimulated by up to 53% in culture with 40 μM antisense oligodeoxynucleotide, whereas both scrambled and sense controls showed no stimulatory effect. Thus, inhibition of endogenous Smad3 and Smad2 gene expression resulted in stimulation of embryonic lung branching similar to that caused by inhibition of TGF-β type II receptor expression and signaling (J. Zhaoet al.,1996,Dev. Biol.180, 242–257). Abrogation of Smad4 (DPC4), the downstream mediator of Smad3 and Smad2 proteins, with antisense oligodeoxynucleotide, also resulted in increased branching morphogenesis. Furthermore, while TGF-β alone inhibited lung branching morphogenesis in culture, addition of exogenous TGF-β1 could not overcome the stimulatory effect on lung branching of Smad antisense oligodeoxynucleotide treatment. By immunohistochemistry, Smad proteins were localized mainly to the epithelial cells lining the branching distal airways, indicating that Smad genes could regulate lung morphogenesis through mesoderm–endoderm interaction. Our results demonstrate, for the first time, that abrogation of Smad2 and Smad3 or of Smad4 gene expression stimulated early mouse embryonic lung branching morphogenesis in culture, possibly through reversing the negative influence of endogenous TGF-β signaling upon lung branching morphogenesis
Ovotestes in B6-XXSxrSex-Reversed Mice

AbstractThe sex-reversed mutationSxrresults in XX males. In the absence of any other mutations, testis differentiation in XXSxrfetuses is essentially normal and only one report of an XXSxrfetus with ovotestes is in the literature. We report that 84% (21/25) of 13 days postcoitum XXSxrfetuses on the B6 inbred genomic background have ovotestes. Ovotestes were found in fetuses from bothSxraandSxrbvariants. Examination of fetuses older than 13 dpc suggests that the presence of ovotestes is transient in most fetuses. However, one overt hermaphrodite was identified after birth. The development of ovotestes is associated with the inbred background and is exacerbated by the dominant spotting oncogene alleleKitW-42J. We propose that spreading of X-inactivation into theSxrregion resulting in loss ofSryexpression is more extensive in B6-Sxrstrains
HoxGroup 3 Paralogs Regulate the Development and Migration of the Thymus, Thyroid, and Parathyroid Glands

AbstractThe thymus, thyroid, and parathyroid glands in vertebrates develop from the pharyngeal region, with contributions both from pharyngeal endoderm and from neural crest cells in the pharyngeal arches.Hoxa3mutant homozygotes have defects in the development of all three organs. Roles for theHoxa3paralogs,Hoxb3andHoxd3,were investigated by examining various mutant combinations. The thyroid defects seen inHoxa3single mutants are exacerbated in double mutants with either of its paralogs, although none of the double-mutant combinations resulted in thyroid agenesis. The results indicate that the primary role of these genes in thyroid development is their effect on the development and migration of the ultimobranchial bodies, which contribute the parafollicular or C-cells to the thyroid.Hoxb3,Hoxd3double mutants show no obvious defects in the thymus or parathyroids. However, the removal of one functional copy ofHoxa3from theHoxb3,Hoxd3double mutants (Hoxa3+/−,Hoxb3−/−,Hoxd3−/−) results in the failure of the thymus and parathyroid glands to migrate to their normal positions in the throat. Very little is known about the molecular mechanisms used to mediate the movement of tissues during development. These results indicate thatHoxa3, Hoxb3,andHoxd3have highly overlapping functions in mediating the migration of pharyngeal organ primordia. In addition,Hoxa3has a unique function with respect to its paralogs in thymus, parathyroid, and thyroid development. This unique function may be conferred by the expression ofHoxa3,but notHoxb3norHoxd3,in the pharyngeal pouch endoderm
Inductive Interactions Regulating Body Patterning in Planarian, Revealed by Analysis of Expression of Novel Genescarf

AbstractSubtractive hybridization was used to search for the early difference in gene expression between anteriorly and posteriorly regenerating tissues of the same region of the planarian body. A sequence (namedscarf) specific for posteriorly regenerating tissue was isolated, encoding a soluble C-type lectin consisting of two slightly different carbohydrate-recognition domains. Such an unusual bivalent structure allows attribution of the protein to a novel subfamily of C-type lectins.scarfexpression in intact planarian is rather abundant and follows a characteristic pattern not linked to any known morphological structure. We performed a series of experiments usingscarfas a molecular marker. Its expression was monitored during different types of regeneration by whole-mountin situhybridization and reverse-transcription polymerase chain reaction. The obtained data suggest thatscarfexpression is positively regulated by anterior tissues closely adjacent to thescarf-expressing region, so that their surgical removal results in rapidscarfswitch-off. In turn, tissues expressingscarfseem to inhibit its activation anteriorly. This indicates that at least some of the body patterning events in planarians are based on a system of reciprocal inductive interactions rather than on a global morphogen gradient
Different Spatial and Temporal Interactions betweenNotch, wingless,andvestigialSpecify Proximal and Distal Pattern Elements of the Wing inDrosophila

AbstractThe wing ofDrosophilais composed of a proximal element, the hinge, which attaches it to the thorax, and a distal one, the wing blade. The development of the wing is a complex process that requires the integration of cellular responses to two signaling systems centered along the anteroposterior and the dorsoventral axes. The genesNotch(N) andwingless(wg) play an important role in generating the information from the dorsoventral axis. Thevestigial(vg) gene is necessary for the development of the wing and is a target of these signaling systems during the growth of the wing. Here we examine the roles thatN, wg,andvgplay during the initial stages of wing development. Our results reveal thatvgis involved in the specification of the wing primordium under the combined control of Notch and wingless signaling. Furthermore, we show that once cells are assigned to the wing fate, their development relies on a sequence of regulatory loops that involveN, wg,andvg.During this process, cells that are exposed to the activity of bothwgandvgwill become wing blade and those that are continuously under the influence ofwgalone will develop as hinge. Our results also indicate that the growth of the cells in the wing blade results from a synergistic effect of the three genesN, wg,andvgon the cells that have been specified as wing blade
Absence of PS Integrins or Laminin A Affects Extracellular Adhesion, but Not Intracellular Assembly, of Hemiadherens and Neuromuscular Junctions inDrosophilaEmbryos

AbstractWe have examined the role of integrins in the formation of the cell junctions that connect muscles to epidermis (muscle attachments) and muscles to neurons (neuromuscular junctions). To this end we have analyzed muscle attachments and neuromuscular junctions ultrastructurally in single or double mutantDrosophilaembryos lacking PS1 integrin (αPS1βPS), PS2 integrin (αPS2βPS), and/or their potential extracellular ligand laminin A. At the muscle attachments PS integrins are essential for the adhesion of hemiadherens junctions (HAJs) to extracellular matrix, but not for their intracellular link to the cytoskeleton. The PS2 integrin is only expressed in the muscles, but it is essential for the adhesion of muscleandepidermal HAJs to electron dense extracellular matrix. It is also required for adhesion of muscle HAJs to a less electron dense form of extracellular matrix, the basement membrane. The PS1 integrin is expressed in epidermal cells and can mediate adhesion of the epidermal HAJs to the basement membrane. The ligands involved in adhesion mediated by both PS integrins seem distinct because adhesion mediated by PS1 appears to require the extracellular matrix component laminin A, while adhesion mediated by PS2 integrin does not. At neuromuscular junctions the formation of functional synapses occurs normally in embryos lacking PS integrins and/or laminin A, but the extent of contact between neuronal and muscle surfaces is altered significantly. We suggest that neuromuscular contact in part requires basement membrane adhesion to the general muscle surface, and this form of adhesion is completely abolished in the absence of laminin A
Coexpression of a Constitutively Active Plasma Membrane Calcium Pump with GFP Identifies Roles for Intracellular Calcium in Controlling Cell Sorting during Morphogenesis inDictyostelium

AbstractTo examine the potential role of calcium in regulatingDictyosteliumdevelopment, we reduced free cytosolic and total cell Ca2+inDictyosteliumcells by expressing a constitutively active form of a human erythrocyte plasma membrane calcium pump. The pump-expressing cells lacked a thapsigargin-mediated increase in cytoplasmic calcium, consistent with a reduced level of total cellular Ca2+. During aggregation, the cells initially formed a large number of aggregation centers, many of which coalesced to form mounds that were smaller than those of wild-type cells, and the cells did not exhibit the normal formation of elongated aggregation streams. The majority of the mounds either arrested at this stage with the formation of small protrusions or formed very aberrant finger-like structures, indicating an essential role for cellular calcium in morphogenesis. We used pump and wild-type cells differentially labeled by expressing different wavelength (green and blue) forms of green fluorescent protein and three-dimensional (3-D) reconstruction of serial fluorescent imaging to visualize the movement of pump and wild-type cells within the aggregate. The results showed that the pump cells exhibited very aberrant cell movement and sorting within the forming mound, suggesting that the reduced cytosolic calcium affects movement required for tip formation. When allowed to form chimeric organisms with wild-type cells, pump cells preferentially localized to two bands, one at the prestalk/prespore boundary and the other in the very posterior of the organism, suggesting that pump cells are unable to properly sort. Expression of the calcium pump had little effect on the induction of prestalk- or prespore-specific genes, whereas extended treatment with EGTA blocked induction of both classes of cell-type-specific genes. Our results suggest a role for intracellular Ca2+in controlling cell sorting and morphogenesis inDictyostelium