pinecone/core-2020-05-10-deduplication huggingface dataset:
Ectodermal Patterning in Vertebrate Embryos

AbstractRecent molecular insights on how the ectodermal layer is patterned in vertebrates are reviewed. Studies on the induction of the central nervous system (CNS) by Spemann's Organizer led to the isolation of noggin and chordin. These secretory proteins function by binding to, and inhibiting, ventral BMPs, in particular BMP-4. Neural induction can be considered as the dorsalization of ectoderm, in which low levels of BMP-signaling result in CNS formation. At high levels of BMP signaling the ectoderm adopts a ventral fate and skin is formed. InXenopusthe forming neural plate already has extensive dorsal-ventral (D-V) patterning, and neural induction and D-V patterning may share common molecular mechanisms. At later stages sonic hedgehog (shh) plays a principal role in D-V patterning, particularly in the neural tube of the amniote embryo. A great many transcription factor markers are available and mouse knockouts provide evidence of their involvement in the regional specification of the neural tube. Recent evidence indicating that differentiation of posterior CNS is promoted by FGF, Wnt-3a, and retinoic acid is reviewed from the point of view of the classical experiments of Nieuwkoop that defined an activation and a transformation step during neural induction
Expression of ZebrafishragGenes during Early Development Identifies the Thymus

AbstractRecent experiments have demonstrated that zebrafish is a vertebrate in which it is possible to carry out large-scale mutagenic screens to identify genes involved in specific developmental pathways. To follow development of the immune system in zebrafish, we have analyzed the expression of the recombination activating genes,rag1andrag2,which we have previously isolated and characterized. These genes catalyze the rearrangement of immunoglobulin genes in immature B lymphocytes and of T cell receptor genes in immature T lymphocytes and are therefore appropriate markers to follow the development of organs containing these cells. By whole-mountin situhybridization, we detected expression of bothraggenes in a paired organ in the head, beginning on the fourth day after fertilization. Histological examination of this organ indicated that it corresponds to the thymus, as described for other fish, an organ that has not previously been identified in zebrafish. By histological analysis, the thymus primordium appears at 54 hr but does not enlarge significantly until 30 hr later. The thymus continues to enlarge and reaches its mature histological organization at 1 month. The pronephros, the major hematopoietic organ in the adult fish, begins to develop hematopoietic tissue about 2 weeks after fertilization. By 1 month, mature lymphocytes are distinguishable in the tissue surrounding renal tubules. Lymphocytes appear in the kidney too late for screening by whole-mountin situhybridization; however, the pattern ofrag1expression in the thymus forms the basis of an assay for mutations affecting development of the thymus or its constituent lymphocytes
Analysis of Cell Movement and Signalling during Ring Formation in an Activated Gα1 Mutant ofDictyostelium discoideumThat Is Defective in Prestalk Zone Formation

AbstractMound formation in the cellular slime mouldDictyosteliumresults from the chemotactic aggregation of competent cells. Periodic cAMP signals propagate as multiarmed spiral waves and coordinate the movement of the cells. In the late aggregate stage the cells differentiate into prespore and several prestalk cell types. Prestalk cells sort out chemotactically to form the tip, which then controls all further development. The tip organises cell movement via a scroll wave that converts to planar waves in the prespore zone leading to rotational cell movement in the tip and periodic forward movement in the prespore zone. Expression of an activated Gα1 protein under its own promoter leads to a severely altered morphogenesis from the mound stage onwards. Instead of forming a tipped mound, the cells form a ring-shaped structure without tip. Wave propagation pattern and dynamics during aggregation and mound formation in the mutant are indistinguishable from the parental strain AX3. However, at the time of tip formation the spiral waves that organise the late aggregate do not evolve in a scroll-organising centre in the tip but transform into a circularly closed (twisted) scroll ring wave. This leads to the formation of a doughnut-shaped aggregate. During further development, the doughnut increases in diameter and the twisted scroll wave converts into a train of planar waves, resulting in periodic rotational cell movement. Although biochemical consequences resulting from this mutation are still unclear, it must affect prestalk cell differentiation. The mutant produces the normal proportion of prespore cells but is unable to form functional prestalk cells, i.e., prestalk cells with an ability to sort out from the prespore cells and form a prestalk zone. Failure of sorting leads to an altered signal geometry, ring-shaped scroll waves, that then directs ring formation. This mutant demonstrates the importance of prestalk cell sorting for the stabilisation of the scroll wave that organises the tip
The Expression of the MouseZic1, Zic2,andZic3Gene Suggests an Essential Role forZicGenes in Body Pattern Formation

AbstractWe examined the expression ofZic1, Zic2,andZic3genes in the mouse embryo by means ofin situhybridization.Zicgenes were found as a group of genes coding for zinc finger proteins that are expressed in a restricted manner in the adult mouse cerebellum. We showed that the genes are the vertebrate homologues ofDrosophila odd-paired,which may play an essential role in parasegmental subdivision and in visceral mesoderm development. The expression of the threeZicgenes was first detected at gastrulation in a spatially restricted manner. At neurulation, the expression became restricted to the dorsal neural ectoderm and dorsal paraxial mesoderm. During organogenesis, the three genes were expressed in specific regions of several developing organs, including dorsal areas of the brain, spinal cord, paraxial mesenchyme, and epidermis, the marginal zone of the neural retina and distal regions of the developing limb. For all stages, significant differences in the spatial expression ofZic1, Zic2,andZic3were observed. Furthermore, the expression ofZicgenes inPax3, Wnt-1,andWnt-3amutant embryos suggested thatZicgenes are not primarily regulated by the three genes which were expressed in dorsal areas similar toZicgenes. However, inopen brain,a mutant with severe neural tube defects, and in theWnt-3amutant mice, the expression ofZicgenes was changed. The changed expression pattern inWnt-3amutant mice suggests thatZicgenes in the neural tube are regulated by the factors from notochord. Our findings suggest thatZicgenes are involved in many developmental processes. Furthermore, analysis of gene expression patterns in different mouse mutants indicated thatZicgenes may act upstream of many known developmental regulatory genes
Clonal Sectors Reveal That a Specific Meristematic Domain Is Not Utilized in the Maize Mutantnarrow sheath

AbstractThe narrow leaf and shortened stem phenotypes of the maize mutant narrow sheath (ns) are postulated to result from the lack of founder cell initialization in a region of the meristem that gives rise to leaf and stem margins. To test this model, a lineage map of the maize meristem is presented which compares the development of leaf margins in the narrow leaf mutant, narrow sheath (ns), and wild-type sibling plants. X-irradiation of mature seeds produced aneuploid albino sectors in wild-type and ns mutant plants. Of particular interest are sectors occurring in more than one leaf, which reflect a meristematic albino cell lineage. Analyses of these sectors indicated that: (1) a region of the ns meristem does not contribute to the founder cell population of the incipient leaf; (2) the margins of ns mutant leaves are derived from a lateral region of the meristem different from those in wild-type siblings; (3) founder cells in wild-type, juvenile-staged vegetative meristems encircle the meristem to a greater extent than do founder cells in adult-staged meristems; and (4) meristematic leaf founder cells may be subdivided into specific lateral domains, such that the position of a sector on the meristem correlates with a particular cell lineage. These data support our model fornsgene function in a specific domain of the meristem
Mist1: A Novel Basic Helix-Loop-Helix Transcription Factor Exhibits a Developmentally Regulated Expression Pattern

AbstractBasic helix-loop-helix (bHLH) proteins often belong to a family of transcription factors that bind to the DNA target sequence -CANNTG- (E-box) that is present in the promoter or enhancer regions of numerous developmentally regulated genes. In this study, we report the isolation and initial characterization of a novel bHLH factor, termed Mist1, that was identified by virtue of its ability to interact with E-box regulatory elements in a yeast “one-hybrid” screening procedure. Northern analysis revealed thatMist1transcripts are expressed in several adult tissues, including stomach, liver, lung, and spleen but no expression is detected in the heart, brain, kidney, or testis. During mouse embryogenesis,Mist1mRNA is first observed at E10.5 in the primitive gut and in the developing lung bud. Expression persists through E16.5 and remains restricted primarily to the epithelial lining.Mist1also is detected in skeletal muscle tissues beginning at E12.5, persisting throughout all embryonic stages examined although in older embryos and in the adult expression becomes severely reduced. At later developmental times,Mist1transcripts also are found in the pancreas, submandibular gland, and adult spleen. As predicted, the Mist1 protein is nuclear and binds efficiently to E-box sites as a homodimer. Mist1 also is capable of binding to E-box elements when complexed as a heterodimer with the widely expressed E-proteins, E12 and E47. Surprisingly, although Mist1 binds to E-boxesin vivo,the Mist1 protein lacks a functional transcription activation domain. These observations suggest that Mist1 may function as a unique regulator of gene expression in several different embryonic and postnatal cell lineages
Two Isoforms of Orthodenticle-Related Proteins (HpOtx) Bind to the Enhancer Element of Sea Urchin Arylsulfatase Gene

AbstractThe sea urchin (Hemicentrotus pulcherrimus) arylsulfatase (HpArs) gene, expressed specifically in aboral ectoderm, contains a 229-bp enhancer in its first intron that is required for the activation ofHpArsgene expression. Deletion analysis shows that a tandem repeat of orthodenticle-related protein (Otx) binding sites are responsible for the activity of this enhancer. Gel mobility shift analysis reveals that three types of Otx-proteins, which show different mobilities in gel shift assays, form complexes with the enhancer. Band I appears before hatching and gradually decreases by the gastrula stage. Band III appears at the blastula stage and Band II appears at the mesenchyme blastula stage; the levels of Band II and III remain constant until the gastrula stage. Two distinct types of HpOtx cDNA clones have been isolated from cDNA libraries of unfertilized eggs and gastrulae. Nucleotide sequences of the homeobox and downstream regions are well conserved in the two types of HpOtx cDNAs, while the region upstream from the homeobox has different nucleotide sequences. By genomic Southern blot analysis, only a single copy ofHpOtxgene is detectable in the Hp genome, making it likely that two HpOtx isoforms are generated from the same gene. Results from Northern blot analysis confirm the presence of two types of HpOtx transcripts. Transcriptional regulation of theHpArsgene may, in part, be carried out through switching of Otx isoforms
In VivoNGF Treatment Increases Proliferation in the Primary Sympathetic Ganglia of Chick Embryos

AbstractNerve growth factor (NGF) is considered to be a target-derived survival or differentiation factor for neural crest cells of the sympathoadrenal lineage. However, exogenous NGF was found to have a positive effect on the size of the primary sympathetic ganglia (PSG) of the chick embryo, well before sympathetic innervation of the periphery. We have determined the cellular mechanism of NGF's action on the PSG by quantifying both proliferation and apoptosis. The proportion of PSG cells in S-phase is nearly double in NGF-treated embryos compared to that in controls, strongly suggesting that NGF acts as a mitogenic factor. NGF reduced the low level of apoptosis at this stage as well. Since trkA has not been detected in the avian sympathetic ganglia until later in development, we suggest that these early effects of exogenous NGF may be mediated by the low-affinity neurotrophin receptor, p75, which is expressed from neural crest migration stages
Multigenic Control of the Localization of the Zone of Polarizing Activity in Limb Morphogenesis in the Mouse

AbstractWe report here that in three preaxial polydactylous mutants in the mouse, namely,lst, lx,andXpl,ectopic expression of theShhandFgf-4genes can be detected at the anterior margin of limb buds. These and three other mutants, namely,Rim4, Hx,andXtJ, which we described in our previous study, all appeared to form a duplicated zone of polarizing activity (ZPA) at the anterior margin of the limb bud. We studied the spatial and temporal pattern of expression of theGli3gene, which is affected in a loss-of-function type of mutation,XtJ. The expression domain ofGli3appeared to be complementary to the ZPA region and the gene was expressed prior toShh.The results support the hypothesis that GLI3 functions in the anterior portion of limb mesoderm to suppress the expression ofShh.InDrosophila,the geneci,the fly homologue ofGli,functions to represshh,suggesting that the negative regulation of the expression ofhedgehogby genes belonging to the GLI-kruppel family has been conserved from flies to mice. Finally, we found that the polydactylous phenotype of the mutantsRim4, Xt, lst,andlxcould be abrogated by the crossing with an inbred strain derived from wild mouse, MSM, whereas the phenotype ofXplcould not. These results indicate the presence of a modifier gene(s) that can influence the mutant phenotype and also that the mutations could be classified into two categories with regard to the mode of interaction with the modifier gene(s). Thus, this study revealed a multigenic control in the establishment of the anteroposterior axis in mouse limb development
ADAM 13: A Novel ADAM Expressed in Somitic Mesoderm and Neural Crest Cells duringXenopus laevisDevelopment

AbstractEmbryonic development involves a series of cell adhesive interactions that provide mechanical and instructive information required for morphogenesis. The ADAMs family of membrane-anchored proteins, containinga disintegrinandmetalloprotease domain, is well suited for participating in such developmental events. They encode not only a potential adhesive function, through an integrin-binding disintegrin domain, but also a potential antiadhesive function, through a zinc-dependent metalloprotease domain. In order to investigate the role of ADAMs in early development we cloned a cDNA encoding a novel member of the ADAM family from aXenopus laevisneurula stage library. We call this cDNA, and the 915-amino-acid protein it encodes, ADAM 13. X-ADAM 13 RNA is expressed during embryogenesis from the midblastula stage through tadpole stage 45. X-ADAM 13 is localized to somitic mesoderm and cranial neural crest cells during gastrulation, neurulation, and in tail bud stages. Sequence analyses of the X-ADAM 13 metalloprotease and disintegrin domains indicate that the protein is likely to be involved in both proteolytic and cell-adhesive functions. The X-ADAM 13 sequence is most closely related to that of mouse meltrin α, which is implicated in myoblast fusion. Our data suggest that X-ADAM 13 may be involved in neural crest cell adhesion and migration as well as myoblast differentiation
A Conserved Element in the Protein-Coding Sequence Is Required for Normal Expression of Replication-Dependent Histone Genes in DevelopingXenopusEmbryos

AbstractReplication-dependent histone genes in the mouse andXenopusshare a common regulatory element within the protein-encoding sequence called the CRASα element (coding region activating sequence α) which has been shown to mediate normal expressionin vivoand to interact with nuclear factorsin vitroin a cell cycle-dependent manner. Thus far, the α element has only been studied in rodent cells in culture, and its effect on histone gene expression during development has not been determined. Here we examine the role of the α element in histone gene expression duringXenopusdevelopment which features a switch in histone gene expression from a replication-independent mode in oocytes to a replication-dependent mode in embryos after midblastula stage.In vivoexpression experiments involving wild-type or α-mutant mouse H3.2 genes show that mutation of the CRASα element results in a fourfold decline of expression in embryos, but does not affect expression in oocytes. Two distinct α sequence-specific binding activities were detected in both oocyte and embryonic extracts. A slowly migrating DNA-binding complex was present at relatively constant levels throughout development from the earliest stages of oogenesis through larval stages. In contrast, levels of a rapidly migrating complex were high in stage I and II oocytes, declined in stage II–VI oocytes, remained low in unfertilized eggs and cleavage stage embryos, and rose dramatically after the midblastula transition. The molecular masses of the factors forming the slow and rapidly migrating complexes were estimated to be approximately 110 and 85 kDa, respectively. DNA-binding activity of the 85 kDa α-binding factor was affected by phosphorylation, binding with higher affinity in the dephosphorylated state. The abrupt increase in DNA-binding activity of the 85-kDa α-binding factor at late blastula coincides with the switch to the replication-dependent mode of histone gene expression. We propose that the conserved α element present in the coding sequence of mouse andXenopuscore histone genes is required for normal replication-dependent histone expression in the developingXenopusembryo
SpHmx,a Sea Urchin Homeobox Gene Expressed in Embryonic Pigment Cells

AbstractWe describe the first complete sea urchin member of the H6 subfamily of homeobox genes. A cDNA encoding the complete protein was recovered from aStrongylocentrotus purpuratuslibrary, and sequence comparisons demonstrate that this gene belongs to the same family as theNkx-5.1, Nkx-5.2,andH6genes of mammals, and theGH6andSOHo-1genes of chicken. In accord with current nomenclature this gene is namedSpHmx.The gene is present in a single copy per haploid genome. Single-strand probe excess hybridization demonstrates that a rare maternal SpHmx mRNA is present in unfertilized eggs. Strong zygotic expression begins during the blastula stage, and the transcript is present at moderately high levels until late in development. Whole mountin situhybridization reveals a remarkable pattern of expression: In midgastrula-stage embryosSpHmxis expressed throughout the archenteron, but particularly strongly in delaminating secondary mesenchyme cells. This more general expression resolves to a dramatic pigment cell-specific pattern in prism and pluteus stages.SpHmxapparently encodes a cell-type-specific transcription factor of embryonic pigment cells
Mechanical Signals in Plant Development: A New Method for Single Cell Studies

AbstractCell division, which is critical to plant development and morphology, requires the orchestration of hundreds of intracellular processes. In the end, however, cells must make critical decisions, based on a discrete set of mechanical signals such as stress, strain, and shear, to divide in such a way that they will survive the mechanical loads generated by turgor pressure and cell enlargement within the growing tissues. Here we report on a method whereby tobacco protoplasts swirled into a 1.5% agarose entrapment medium will survive and divide. The application of a controlled mechanical load to agarose blocks containing protoplasts orients the primary division plane of the embedded cells. Photoelastic analysis of the agarose entrapment medium can identify the lines of principal stress within the agarose, confirming the hypothesis that cells divide either parallel or perpendicular to the principal stress tensors. The coincidence between the orientation of the new division wall and the orientation of the principal stress tensors suggests that the perception of mechanical stress is a characteristic of individual plant cells. The ability of a cell to determine a shear-free orientation for a new partition wall may be related to the applied load through the deformation of the matrix material. In an isotropic matrix a uniaxial load will produce a rotationally symmetric strain field, which will define a shear-free plane. Where high stress intensities combine with the loading geometry to produce multiaxial loads there will be no axis of rotational symmetry and hence no shear free plane. This suggests that two mechanisms may be orienting the division plane, one a mechanism that works in rotationally symmetrical fields, yielding divisions perpendicular to the compressive tensor, parallel to the long axis of the cell, and one in asymmetric fields, yielding divisions parallel to the short axis of the cell and the compressive tensor
Modulation of Embryonic Intracellular Ca2+Signaling byWnt-5A

AbstractWntgenes encode secreted proteins which are implicated in receptor-mediated cell–cell signaling events important in embryogenesis, but the second messenger systems modulated byWntshave not been identified. We report that ectopic expression ofXwnt-5A in zebrafish embryos enhances the frequency of intracellular Ca2+transients in the enveloping layer of the blastodisc, whereasXwnt-8 does not. These transients are independent of extracellular Ca2+. Consistent with the observed Ca2+transients playing a role in responses of embryos toXwnt-5A, we report that the ligand-activated serotonin type 1C receptor, which stimulates PI cycle activity and Ca2+signaling independent ofWnts,phenocopies embryonic responses toXwnt-5A. These results suggest that intercellular signaling by a subset of vertebrate Wnts involves modulation of a intracellular Ca2+signaling pathway, which may arise from phosphatidylinositol cycle activity