pinecone/core-2020-05-10-deduplication huggingface dataset:
Na+/H+Antiporter Activity in Hamster Embryos Is Activated during Fertilization

AbstractThis study characterized the activation of the regulatory activity of the Na+/H+antiporter during fertilization of hamster embryos. Hamster oocytes appeared to lack any mechanism for the regulation of intracellular pH in the acid range. Similarly, no Na+/H+antiporter activity could be detected in embryos that were collected from the reproductive tract between 1 and 5 h post-egg activation (PEA). Activity of the Na+/H+antiporter was first detected in embryos collected at 5.5 h PEA and gradually increased to reach maximal activity in embryos collected at 7 h PEA. Parthenogenetically activated one-cell and two-cell embryos demonstrate Na+/H+antiporter activity, indicating that antiporter activity is maternally derived and initiated by activation of the egg. The inability of cycloheximide, colchicine, or cytochalasin D to affect initiation of antiporter activity indicates that antiporter appearance is not dependent on the synthesis of new protein or recruitment of existing protein to the cell membrane. In contrast, incubation of one-cell embryos with sphingosine did inhibit the appearance of Na+/H+antiporter activity, showing that inhibition of normal protein kinase C activity is detrimental to antiporter function. Furthermore, incubation of oocytes with a phorbol ester which stimulates protein kinase C activity induced Na+/H+antiporter activity in oocytes in which the activity was previously absent. Incubation with an intracellular calcium chelator also reduced the appearance of antiporter activity. Taken together, these data indicate that the appearance of Na+/H+antiporter activity following egg activation may be due, at least in part, to regulation by protein kinase C and intracellular calcium levels
Intracellular pH Regulation by HCO−3/Cl−Exchange Is Activated during Early Mouse Zygote Development

AbstractWe report here that at least one major pHi-regulatory mechanism, the HCO−3/Cl−exchanger, is quiescent in unfertilized mouse eggs but becomes fully activated during early development following fertilization. Zygotes (8–12 h postfertilization) exhibited a marked intracellular alkalinization upon external Cl−removal, which is indicative of active HCO−3/Cl−exchangers, in contrast to the very small response observed in eggs. In addition, efflux of Cl−from eggs upon external Cl−removal was much slower than that from zygotes, indicating additional pathways for Cl−to cross the plasma membrane in zygotes. Furthermore, while zygotes quickly recovered from an induced alkalosis, eggs exhibited only a slow, incomplete recovery. Followingin vitrofertilization (IVF), increased HCO−3/Cl−exchanger activity was first detectable about 4 h postfertilization and reached the maximal level after about 8 h. The upregulation of HCO−3/Cl−exchanger activity after fertilization appeared to occur by activation of existing, inactive exchangers rather than by synthesis or transport of new exchangers, as the increase in activity following IVF was unaffected by inhibition of protein synthesis or by disruption of the Golgi apparatus or the cytoskeleton. This activation may depend on the Ca2+transients which follow fertilization, as suppression of these transients, using the Ca2+chelator BAPTA, reduced subsequent upregulation of HCO−3/Cl−exchanger activity by about 50%. Activation of pHi-regulatory systems may be a widespread feature of the earliest period of embryonic development, not restricted to species such as marine invertebrates as previously believed
ELT-3: ACaenorhabditis elegansGATA Factor Expressed in the Embryonic Epidermis during Morphogenesis

AbstractWe have identified a gene encoding a new member of theCaenorhabditis elegansGATA transcription factor family,elt-3.The predicted ELT-3 polypeptide contains a single GATA-type zinc finger (C-X2-C-X17-C-X2-C) along with a conserved adjacent basic region.elt-3mRNA is present in all stages ofC. elegansdevelopment but is most abundant in embryos. Reporter gene analysis and antibody staining show thatelt-3is first expressed in the dorsal and ventral hypodermal cells, and in hypodermal cells of the head and tail, immediately after the final embryonic cell division that gives rise to these cells. No expression is seen in the lateral hypodermal (seam) cells.elt-3expression is maintained at a constant level in the epidermis until the 212-fold stage of development, after which reporter gene expression declines to a low level and endogenous protein can no longer be detected by specific antibody. A second phase ofelt-3expression in cells immediately anterior and posterior to the gut begins in pretzel-stage embryos.elt-1andlin-26are two genes known to be important in specification and maintenance of hypodermal cell fates. We have found thatelt-1is required for the formation of most, but not all,elt-3-expressing cells. In contrast,lin-26function does not appear necessary forelt-3expression. Finally, we have characterised the candidate homologue ofelt-3in the nematodeCaenorhabditis briggsae.Many features of theelt-3genomic and transcript structure are conserved between the two species, suggesting thatelt-3is likely to perform an evolutionarily significant function during development
NotchsplIs Deficient for Inductive Processes in the Eye, andE(spl)DEnhancessplitby Interfering with Proneural Activity

AbstractEye development inDrosophilainvolves the Notch signaling pathway at several consecutive steps. At first, Notch signaling is required for stable expression of the proneural geneatonal (ato),thereby maintaining neural potential of the cells. Second, in a process of lateral inhibition, Notch signaling is necessary to confine neural commitment to individual photoreceptor founder cells. Later on, the successive addition of cells to maturing ommatidia is under Notch control. In contrast to previous assumptions, the recessiveNotchallelesplit(Nspl) involves specifically loss of the early proneural Notch activity in the eye, which is in agreement with bristle defects as well. As a result, fewer cells gain neural potential and fewer ommatidia are founded. Enhancement of this phenotype by the dominant mutationEnhancer of split[E(spl)D] happens within the remaining proneural cells, in which Ato expression is abolished. In line with genetic data, this process occurs primarily at the protein level due to altered protein–protein interactions between the aberrant E(spl)Dand proneural proteins.Nsplis the first Notch mutation known to specifically affect Notch inductive processes during eye development
Mutations in the Zebrafish Unmask Shared Regulatory Pathways Controlling the Development of Catecholaminergic Neurons

AbstractThe mechanism by which pluripotent progenitors give rise to distinct classes of mature neurons in vertebrates is not well understood. To address this issue we undertook a genetic screen for mutations which affect the commitment and differentiation of catecholaminergic (CA) [dopaminergic (DA), noradrenergic (NA), and adrenergic] neurons in the zebrafish,Danio rerio.The identified mutations constitute five complementation groups.motionlessandfoggyaffect the number and differentiation state of hypothalamic DA, telencephalic DA, retinal DA, locus coeruleus (LC) NA, and sympathetic NA neurons. Thetoo fewmutation leads to a specific reduction in the number of hypothalamic DA neurons.no soullacks arch-associated NA cells and has defects in pharyngeal arches, andsoullesslacks both arch-associated and LC cell groups. Our analyses suggest that the genes defined by these mutations regulate different steps in the differentiation of multipotent CA progenitors. They further reveal an underlying universal mechanism for the control of CA cell fates, which involve combinatorial usage of regulatory genes
Opposite Effects of FGF and BMP-4 on Embryonic Blood Formation: Roles of PV.1 and GATA-2

AbstractIn adult vertebrates, fibroblast growth factor (FGF) synergizes with many hematopoietic cytokines to stimulate the proliferation of hematopoietic progenitors. In vertebrate development, the FGF signaling pathway is important in the formation of some derivatives of ventroposterior mesoderm. However, the function of FGF in the specification of the embryonic erythropoietic lineage has remained unclear. Here we address the role of FGF in the specification of the erythropoietic lineage in theXenopusembryo. We report that ventral injection of embryonic FGF (eFGF) mRNA at as little as 10 pg at the four-cell stage suppresses ventral blood island (VBI) formation, whereas expression of the dominant negative form of the FGF receptor in the lateral mesoderm, where physiologically no blood tissue is formed, results in a dramatic expansion of the VBI. Similar results were observed in isolated ventral marginal zones and animal caps. Bone morphogenetic protein-4 (BMP-4) is known to induce erythropoiesis in theXenopusembryo. Therefore, we examined how the BMP-4 and FGF signaling pathways might interact in the decision of ventral mesoderm to form blood. We observed that eFGF inhibits BMP-4-induced erythropoiesis by differentially regulating expression of the BMP-4 downstream effectorsGATA-2andPV.1. GATA-2,which stimulates erythropoiesis, is suppressed by FGF.PV.1,which we demonstrate to inhibit blood development, is enhanced by FGF. Additionally,PV.1andGATA-2negatively regulate transcription of each other. Thus, BMP-4 induces two transcription factors which have opposing effects on blood development. The FGF and BMP-4 signaling pathways interact to regulate the specification of the erythropoietic lineage
Zonula Occludens-1 and E-cadherin Are Coordinately Expressed in the Mouse Uterus with the Initiation of Implantation and Decidualization

AbstractTwo-way interactions between the blastocyst trophectoderm and the uterine luminal epithelium are essential for implantation. The key events of this process are cell–cell contact of trophectoderm cells with uterine luminal epithelial cells, controlled invasion of trophoblast cells through the luminal epithelium and the basement membrane, transformation of uterine stromal cells surrounding the blastocyst into decidual cells, and protection of the “semiallogenic” embryo from the mother's immunological responses. Because cell–cell contact between the trophectoderm epithelium and the luminal epithelium is essential for implantation, we investigated the expression of zonula occludens-1 (ZO-1) and E-cadherin, two molecules associated with epithelial cell junctions, in the mouse uterus during the periimplantation period. Preimplantation uterine epithelial cells express both ZO-1 and E-cadherin. With the initiation and progression of implantation, ZO-1 and E-cadherin are expressed in stromal cells of the primary decidual zone (PDZ). As trophoblast invasion progresses, these two molecules are expressed in stroma in advance of the invading trophoblast cells. These results suggest that expression of these adherence and tight junctions molecules in the PDZ serves to function as a permeability barrier to regulate access of immunologically competent maternal cells and/or molecules to the embryo and provide homotypic guidance of trophoblast cells in the endometrium
Retinoid Signaling Is Required for Chondrocyte Maturation and Endochondral Bone Formation during Limb Skeletogenesis

AbstractRetinoids have long been known to influence skeletogenesis but the specific roles played by these effectors and their nuclear receptors remain unclear. Thus, it is not known whether endogenous retinoids are present in developing skeletal elements, whether expression of the retinoic acid receptor (RAR) genes α, β, and γ changes during chondrocyte maturation, or how interference with retinoid signaling affects skeletogenesis. We found that immature chondrocytes present in stage 27 (Day 5.5) chick embryo humerus exhibited low and diffuse expression of RARα and γ, while RARβ expression was strong in perichondrium. Emergence of hypertrophic chondrocytes in Day 8–10 embryo limbs was accompanied by a marked and selective up-regulation of RARγ gene expression. The RARγ-rich type X collagen-expressing hypertrophic chondrocytes lay below metaphyseal prehypertrophic chondrocytes expressingIndian hedgehog(Ihh) and were followed by mineralizing chondrocytes undergoing endochondral ossification. Bioassays revealed that cartilaginous elements in Day 5.5, 8.5, and 10 chick embryo limbs all contained endogenous retinoids; strikingly, the perichondrial tissues surrounding the cartilages contained very large amounts of retinoids. Implantation of beads filled with retinoid antagonist Ro 41-5253 or AGN 193109 near the humeral anlagens in stage 21 (Day 3.5) or stage 27 chick embryos severely affected humerus development. In comparison to their normal counterparts, antagonist-treated humeri in Day 8.5–10 chick embryos were significantly shorter and abnormally bent; their diaphyseal chondrocytes had remained prehypertrophicIhh-expressing cells, did not express RARγ, and were not undergoing endochondral ossification. Interestingly, formation of an intramembranous bony collar around the diaphysis was not affected by antagonist treatment. Using chondrocyte cultures, we found that the antagonists effectively interfered with the ability of all-trans-retinoic acid to induce terminal cell maturation. The results provide clear evidence that retinoid-dependent and RAR-mediated mechanisms are required for completion of the chondrocyte maturation process and endochondral ossification in the developing limb. These mechanisms may be positively influenced by cooperative interactions between the chondrocytes and their retinoid-rich perichondrial tissues
Mound-Cell Movement and Morphogenesis inDictyostelium

AbstractTo examine the mechanisms of cell locomotion within a three-dimensional (3-D) cell mass, we have undertaken a systematic 3-D analysis of individual cell movements in theDictyosteliummound, the first 3-D structure to form during development of the fruiting body. We used time-lapse deconvolution microscopy to examine two strains whose motion represents endpoints on the spectrum of motile behaviors that we have observed in mounds. In AX-2 mounds, cell motion is slow and trajectories are a combination of random and radial, compared to KAX-3, in which motion is fivefold faster and most trajectories are rotational. Although radial or rotational motion was correlated with the optical-density wave patterns present in each strain, we also found small but significant subpopulations of cells that moved differently from the majority, demonstrating that optical-density waves are at best insufficient to explain all motile behavior in mounds. In examining morphogenesis in these strains, we noted that AX-2 mounds tended to culminate directly to a fruiting body, whereas KAX-3 mounds first formed a migratory slug. By altering buffering conditions we could interchange these behaviors and then found that mound-cell motions also changed accordingly. This demonstrates a correlation between mound-cell motion and subsequent development, but it is not obligatory. Chimeric mounds composed of only 10% KAX-3 cells and 90% AX-2 cells exhibited rotational motion, suggesting that a diffusible molecule induces rotation, but many of these mounds still culminated directly, demonstrating that rotational motion does not always lead to slug migration. Our observations provide a detailed analysis of cell motion for two distinct modes of mound and slug formation inDictyostelium
Z/AP, a Double Reporter for Cre-Mediated Recombination

AbstractThe Cre/loxPsite-specific recombination system combined with embryonic stem cell-mediated technologies has greatly expanded our capability to address normal and disease development in mammals using genetic approaches. The success of this emerging technology hinges on the production of Cre-expressing transgenic lines that provide cell type-, tissue-, or developmental stage-specific recombination betweenloxPsites placed in the genome. Here we describe and characterize the production of a double-reporter mouse line that provides a convenient and reliable readout of Cre recombinase activity. Throughout all embryonic and adult stages, the transgenic animal expresses thelacZreporter gene before Cre-mediated excision occurs. Cre excision, however, removes thelacZgene, allowing expression of the second reporter, the human alkaline phosphatase gene. This double-reporter transgenic line is able to indicate the occurrence of Cre excision in an extremely widespread manner from early embryonic to adult lineages. It will be a valuable reagent for the increasing number of investigators taking advantage of the powerful tools provided by the Cre/loxPsite-specific recombinase system
Control of Oocyte Maturation in Sexually MatureDrosophilaFemales

AbstractIn many sexually mature insects egg production and oviposition are tightly coupled to copulation. Sex-Peptide is a 36-amino-acid peptide synthesized in the accessory glands ofDrosophila melanogastermales and transferred to the female during copulation. Sex-Peptide stimulates vitellogenic oocyte progression through a putative control point at about stage 9 of oogenesis. Here we show that application of the juvenile hormone analogue methoprene mimics the Sex-Peptide-mediated stimulation of vitellogenic oocyte progression in sexually mature virgin females. Apoptosis is induced by 20-hydroxyecdysone in nurse cells of stage 9 egg chambers at physiological concentrations (10−7M). 20-Hydroxyecdysone thus acts as an antagonist of early vitellogenic oocyte development. Simultaneous application of juvenile hormone analogue, however, protects early vitellogenic oocytes from 20-hydroxyecdysone-induced resorption. These results suggest that the balance of these hormones in the hemolymph regulates whether oocytes will progress through the control point at stage 9 or undergo apoptosis. These data are further supported by a molecular analysis of the regulation of yolk protein synthesis and uptake into the ovary by the two hormones. We conclude that juvenile hormone is a downstream component in the Sex-Peptide response cascade and acts by stimulating vitellogenic oocyte progression and inhibiting apoptosis. Since juvenile hormone analogue does not elicit increased oviposition and reduced receptivity, Sex-Peptide must have an additional, separate effect on these two postmating responses
Independent Development of Sensory and Motor Innervation Patterns in Embryonic Chick Hindlimbs

AbstractPrevious studies suggest that sensory axon outgrowth is guided by motoneurons, which are specified to innervate particular target muscles. Here we present evidence that questions this conclusion. We have used a new approach to assess the pathfinding abilities of bona fide sensory neurons, first by eliminating motoneurons after neural crest cells have coalesced into dorsal root ganglia (DRG) and second by challenging sensory neurons to innervate muscles in a novel environment created by shifting a limb bud rostrally. The resulting sensory innervation patterns mapped with the lipophilic dyes DiI and DiA showed that sensory axons projected robustly to muscles in the absence of motoneurons, if motoneurons were eliminated after DRG formation. Moreover, sensory neurons projected appropriately to their usual target muscles under these conditions. In contrast, following limb shifts, muscle sensory innervation was often derived from inappropriate segments. In this novel environment, sensory neurons tended to make more “mistakes” than motoneurons. Whereas motoneurons tended to innervate their embryologically correct muscles, sensory innervation was more widespread and was generally from more rostral segments than normal. Similar results were obtained when motoneurons were eliminated in embryos with limb shifts. These findings show that sensory neurons are capable of navigating through their usual terrain without guidance from motor axons. However, unlike motor axons, sensory axons do not appear to actively seek out appropriate target muscles when confronted with a novel terrain. These findings suggest that sensory neuron identity with regard to pathway and target choice may be unspecified or quite plastic at the time of initial axon outgrowth
Neural Crest Can Form Cartilages Normally Derived from Mesoderm during Development of the Avian Head Skeleton

AbstractThe lateral wall of the avian braincase, which is indicative of the primitive amniote condition, is formed from mesoderm. In contrast, mammals have replaced this portion of their head skeleton with a nonhomologous bone of neural crest origin. Features that characterize the local developmental environment may have enabled a neural crest-derived skeletal element to be integrated into a mesodermal region of the braincase during the course of evolution. The lateral wall of the braincase lies along a boundary in the head that separates neural crest from mesoderm, and also, neural crest cells migrate through this region on their way to the first visceral arch. Differences in the availability of one skeletogenic population versus the other may determine the final composition of the lateral wall of the braincase. Using the quail–chick chimeric system, this investigation tests if populations of neural crest, when augmented and expanded within populations of mesoderm, will give rise to the lateral wall of the braincase. Results demonstrate that neural crest can produce cartilages that are morphologically indistinguishable from elements normally generated by mesoderm. These findings (1) indicate that neural crest can respond to the same cues that both promote skeletogenesis and enable proper patterning in mesoderm, (2) challenge hypotheses on the nature of the boundary between neural crest and mesoderm in the head, and (3) suggest that changes in the allocation of migrating cells could have enabled a neural crest-derived skeletal element to replace a mesodermal portion of the braincase during evolution
Regulation of Left–Right Asymmetries in the Zebrafish by Shh and BMP4

AbstractLeft–right (LR) asymmetry of the heart in vertebrates is regulated by early asymmetric signals in the embryo, including the secreted signal Sonic hedgehog (Shh), but less is known about LR asymmetries of visceral organs. Here we show that Shh also specifies asymmetries in visceral precursors in the zebrafish and that cardiac and visceral sidedness are independent. The transcription factors fli-1 and Nkx-2.5 are expressed asymmetrically in the precardiac mesoderm and subsequently in the heart; an Eph receptor, rtk2, and an adhesion protein, DM-GRASP, mark early asymmetries in visceral endoderm. Misexpression of shh mRNA, or a dominant negative form of protein kinase A, on the right side reverses the expression of these asymmetries in precursors of both the heart and the viscera. Reversals in the heart and gut are uncoordinated, suggesting that each organ interprets the signal independently. Misexpression of Bone Morphogenetic Protein (BMP4) on the right side reverses the heart, but visceral organs are unaffected, consistent with a function for BMPs locally in the heart field. Zebrafish mutants with midline defects show independent reversals of cardiac and visceral laterality. Thus, hh signals influence the development of multiple organ asymmetries in zebrafish and different organs appear to respond to a central cascade of midline signaling independently, which in the heart involves BMP4