pinecone/core-2020-05-10-deduplication huggingface dataset:
Intracellular BMP Signaling Regulation in Vertebrates: Pathway or Network?

AbstractBone morphogenetic proteins (BMPs), members of the TGF-β superfamily of secreted signaling molecules, have important functions in many biological contexts. They bind to specific serine/threonine kinase receptors, which transduce the signal to the nucleus through Smad proteins. The question of how BMPs can have such diverse effects while using the same canonical Smad pathway has recently come closer to an answer at the molecular level. Nuclear cofactors have been identified that cooperate with the Smads in regulating specific target genes depending on the cellular context. In addition, the pivotal role BMP signaling plays is underscored by the identification of factors that regulate members of this pathway at the cell surface, in the cytoplasm, and in the nucleus. Many of these factors are BMP-inducible and inhibit the BMP pathway, thus establishing negative feedback loops. Members of the BMP–Smad pathway can also physically interact with components of other signaling pathways to establish crosstalk. Finally, there is accumulating evidence that an alternative pathway involving MAP kinases can transduce BMP signals. The evidence and implications of these findings are discussed with an emphasis on early embryonic development of Xenopus and vertebrates
Modulation of the Ras/MAPK Signalling Pathway by the Redox Function of Selenoproteins in Drosophila melanogaster

AbstractModulation of reactive oxygen species (ROS) plays a key role in signal transduction pathways. Selenoproteins act controlling the redox balance of the cell. We have studied how the alteration of the redox balance caused by patufet (selDptuf), a null mutation in the Drosophila melanogaster selenophosphate synthetase 1 (sps1) gene, which codes for the SelD enzyme of the selenoprotein biosynthesis, affects the Ras/MAPK signalling pathway. The selDptuf mutation dominantly suppresses the phenotypes in the eye and the wing caused by hyperactivation of the Ras/MAPK cassette and the activated forms of the Drosophila EGF receptor (DER) and Sevenless (Sev) receptor tyrosine kinases (RTKs), which signal in the eye and wing, respectively. No dominant interaction is observed with sensitized conditions in the Wnt, Notch, Insulin-Pi3K, and DPP signalling pathways. Our current hypothesis is that selenoproteins selectively modulate the Ras/MAPK signalling pathway through their antioxidant function. This is further supported by the fact that a selenoprotein-independent increase in ROS caused by the catalase amorphic Catn1 allele also reduces Ras/MAPK signalling. Here, we present the first evidence for the role of intracelular redox environment in signalling pathways in Drosophila as a whole organism
Visualizing Normal and Defective Bone Development in Zebrafish Embryos Using the Fluorescent Chromophore Calcein

AbstractZebrafish have recently become a model of choice among developmental biologists. This unique model enables both modern molecular and genetic studies to be carried out to identify genes involved in a wide variety of developmental processes. The success of the genetic approach depends largely on the application of an easy and effective screening method to identify interesting mutants. In order to develop a method for visualizing skeletal structures in zebrafish embryos that would be suitable for screening skeletal mutants, we investigated the use of the fluorescent chromophore calcein, which binds specifically to calcified skeletal structures. By using this method, we followed the development of the skeletal structures in zebrafish embryos from day 1 to day 21 postfertilization, and analyzed the effect of bone morphogenetic protein-2 (BMP2) on axial skeleton development. We found the development of the calcified skeletal structure to appear in a progressive fashion from head to tail. Calcified structures in the head (i.e., the jaw) developed first, which were then followed by the axial skeleton in the trunk. Interesting to note was that there appeared to be two domains in the calcification of vertebrae within the axial skeleton. The first three vertebrae were in the first domain; the rest being in the second domain. Compared with Alcian blue staining, we found that calcein staining indeed labels calcified skeletal structures, and, moreover, it is a more sensitive and inclusive method for visualizing skeletal structures. To determine whether calcein staining could also be used to detect abnormal bone development, we ectopically expressed BMP2 in zebrafish notochord cells. We demonstrated that ectopic expression of BMP2 in notochord cells inhibited the development of the axial skeleton. Together, these results clearly demonstrated the sensitivity of calcein staining for visualizing bone structures in developing zebrafish embryos and its effectiveness for screening for mutants that have bone structure defects
Involvement of Laminin Binding Integrins and Laminin-5 in Branching Morphogenesis of the Ureteric Bud during Kidney Development

AbstractBranching morphogenesis of the ureteric bud (UB) [induced by the metanephric mesenchyme (MM)] is necessary for normal kidney development. The role of integrins in this complex developmental process is not well understood. However, the recent advent of in vitro model systems to study branching of UB cells and isolated UB tissue makes possible a more detailed analysis of the integrins involved. We detected integrin subunits α3, α6, β1, and β4 in both the UB and cells derived from the early UB. Blocking the function of each of these integrin subunits individually markedly inhibited branching morphogenesis in cell culture models. However, inhibiting individual integrin function with blocking antibodies in whole kidney and isolated UB culture only partially inhibited UB branching morphogenesis, suggesting that, in these more complex in vitro systems, multiple integrins are involved in the branching program. In whole organ and isolated bud culture, marked retardation of UB branching was observed only when both α3 and α6 integrin subunits were inhibited. The α6 integrin subunit can be expressed as both α6β1 and α6β4, and both of these β subunits are important for UB branching morphogenesis in both cell and organ culture. Furthermore, laminin-5, a common ligand for integrins α3β1 and α6β4, was detected in the developing UB and shown to be required for normal UB branching morphogenesis in whole embryonic kidney organ culture as well as isolated UB culture. Together, these data from UB cell culture, organ culture, and isolated UB culture models indicate that both integrin α3 and α6 subunits play a direct role in UB branching morphogenesis, as opposed to being modulators of the inductive effects of mesenchyme on UB development. Furthermore the data are consistent with a role for laminin-5, acting through its α3β1 and/or α6β4 integrin receptors, in UB branching during nephrogenesis. These data may help to partially explain the renal phenotype seen in integrin α3 and α3/α6 subunit-deficient animals
cGMP Enhances the Sonic Hedgehog Response in Neural Plate Cells

AbstractThe elaboration of distinct cell types during development is dependent on a small number of inductive molecules. Among these inducers is Sonic hedgehog (Shh), which, in combination with other factors, patterns the dorsoventral (DV) axis of the nervous system. The response of a cell is dependent in part on its complement of cyclic nucleotides. cAMP antagonizes Shh signaling, and we examined the influence of cGMP on the Shh response. Cells in chick neural plate explants respond to Shh by differentiating into ventral neural-cell types. Exposure of intermediate-zone explants to cGMP analogs enhanced their response to Shh in a dose-dependent manner. The Shh response was also enhanced in dorsal-zone explants exposed to chick natriuretic peptide (chNP), which stimulates cGMP production by membrane-bound guanylate cyclase (mGC). Addition of chNP to intermediate-zone explants did not enhance the Shh response, consistent with a reported lack of mGC in this region of the neural tube. Finally, the presence of a nitric oxide (NO)-sensitive guanylate cyclase (GC) was established by demonstrating cGMP immunoreactivity in neural tissue following NO stimulation of whole chick embryos. Intracellular levels of cGMP and cAMP may thus provide a mechanism through which other factors modulate the Shh response during neural development
Zebrafish Early Macrophages Colonize Cephalic Mesenchyme and Developing Brain, Retina, and Epidermis through a M-CSF Receptor-Dependent Invasive Process

AbstractThe origin of resident (noninflammatory) macrophages in vertebrate tissues is still poorly understood. In the zebrafish embryo, we recently described a specific lineage of early macrophages that differentiate in the yolk sac before the onset of blood circulation. We now show that these early macrophages spread in the whole cephalic mesenchyme, and from there invade epithelial tissues: epidermis, retina, and brain—especially the optic tectum. In the panther mutant, which lacks a functional fms (M-CSF receptor) gene, early macrophages differentiate and behave apparently normally in the yolk sac, but then fail to invade embryonic tissues. Our video recordings then document for the first time the behavior of macrophages in the invaded tissues, revealing the striking propensity of early macrophages in epidermis and brain to wander restlessly among epithelial cells. This unexpected behavior suggests that tissue macrophages may be constantly “patrolling” for immune and possibly also developmental and trophic surveillance. At 60 h post-fertilization, all macrophages in the brain and retina undergo a specific phenotypic transformation, into “early (amoeboid) microglia”: they become more highly endocytic, they down-regulate the L-plastin gene, and abruptly start expressing high levels of apolipoprotein E, a well-known neurotrophic lipid carrier
RNAi As a Tool for Understanding Germline Development in Caenorhabditis elegans: Uses and Cautions

AbstractRNA-mediated genetic interference (RNAi) has become a very useful tool for analyzing gene function in development and other processes. RNAi can be used as a complement to traditional genetic studies or as a primary means of determining biological function. However, the efficacy of RNAi depends on a variety of factors that the researcher must take into consideration. This review focuses on germline development in the nematode, Caenorhabditis elegans, and discusses the uses and limitations of RNAi in providing new information about gene function as well as the possible endogenous role RNAi plays in germline physiology
A Reciprocal Relationship between Cutaneous Nerves and Repairing Skin Wounds in the Developing Chick Embryo

AbstractVarious studies have suggested that the rate of adult skin healing may be in some way dependent on signals emanating from cutaneous nerves. Further, it appears that adult wounds become hyperinnervated by sensory nerves during the process of healing. In order to investigate this reciprocal relationship further, we have used a simple embryonic model to look at the effect of wounds on nerves, and conversely, the effect of nerves on wounds. We find that wounds made to the dorsum of the chick wing bud, at a stage prior to normal innervation (at E4), or soon after the normal establishment of cutaneous innervation (at E7), subtly alter the pattern of branching by perturbing developmental guidance cues, but do not cause hyperinnervation, whereas wounding at E14 does cause hyperinnervation. By creating chicks with nerveless wings, we show that from E7, wound healing in the absence of nerves is significantly impaired. These observations suggest that, from the earliest stages of skin innervation, the presence of nerves is beneficial to the healing process, but that, in contrast to neonatal and adult tissues, wound healing in the embryo and early foetus does not trigger hyperinnervation
Temporary Disruption of the Retinal Basal Lamina and Its Effect on Retinal Histogenesis

AbstractAn experimental paradigm was devised to remove the retinal basal lamina for defined periods of development: the basal lamina was dissolved by injecting collagenase into the vitreous of embryonic chick eyes, and its regeneration was induced by a chase with mouse laminin-1 and α2-macroglobulin. The laminin-1 was essential in reconstituting a new basal lamina and could not be replaced by laminin-2 or collagen IV, whereas the macroglobulin served as a collagenase inhibitor that did not directly contribute to basal lamina regeneration. The regeneration occurred within 6 h after the laminin-1 chase by forming a morphologically complete basal lamina that included all known basal lamina proteins from chick embryos, such as laminin-1, nidogen-1, collagens IV and XVIII, perlecan, and agrin. The temporary absence of the basal lamina had dramatic effects on retinal histogenesis, such as an irreversible retraction of the endfeet of the neuroepithelial cells from the vitreal surface of the retina, the formation of a disorganized ganglion cell layer with an increase in ganglion cells by 30%, and the appearance of multiple retinal ectopias. Finally, basal lamina regeneration was associated with aberrant axons failing to correctly enter the optic nerve. The present data demonstrate that a transient disruption of the basal lamina leads to dramatic and probably irreversible aberrations in the histogenesis in the developing central nervous system
Molecular Integration of Inductive and Mesoderm-Intrinsic Inputs Governs even-skipped Enhancer Activity in a Subset of Pericardial and Dorsal Muscle Progenitors

AbstractIndividual somatic muscles and heart progenitors are specified at defined positions within the mesodermal layer of Drosophila. The expression of the homeobox gene even-skipped (eve) identifies one specific subset of cells in the dorsal mesoderm, which give rise to particular pericardial cells and dorsal body wall muscles. Genetic analysis has shown that the induction of eve in these cells involves the combined activities of genes encoding mesoderm-intrinsic factors, such as Tinman (Tin), and spatially restricted signaling activities that are largely derived from the ectoderm, particularly those encoded by wingless (wg) and decapentaplegic (dpp). Here we show that a Dpp-activated Smad protein, phosphorylated Mad, is colocalized in eve-expressing cells during an extended developmental period. We demonstrate further that a mesodermally active enhancer of eve contains several Smad and Tin binding sites that are essential for enhancer activity in vivo. This enhancer also contains a number of binding sites for the Wg-effector Pangolin (Pan/Lef-1), which are required for full levels of enhancer activity. However, we find that their main function is to prevent ectopic enhancer activity in the dorsal mesoderm. This suggests that, in the absence of Wg signaling, Pan binding serves to abrogate the synergistic activities of Smads and Tin in eve activation while, in cells that receive Wg signals, Pan is converted into a coactivator that promotes eve induction. Together, these data show that the eve enhancer integrates several regulatory pathways via the combinatorial binding of the mesoderm-intrinsic regulator Tin and the effectors of the Dpp and Wg signals
Activins as Regulators of Branching Morphogenesis

AbstractDevelopment of glandular organs such as the kidney, lung, and prostate involves the process of branching morphogenesis. The developing organ begins as an epithelial bud that invades the surrounding mesenchyme, projecting dividing epithelial cords or tubes away from the site of initiation. This is a tightly regulated process that requires complex epithelial–mesenchymal interactions, resulting in a three-dimensional treelike structure. We propose that activins are key growth and differentiation factors during this process. The purpose of this review is to examine the direct, indirect, and correlative lines of evidence to support this hypothesis. The expression of activins is reviewed together with the effect of activins and follistatins in the development of branched organs. We demonstrate that activin has both negative and positive effects on cell growth during branching morphogenesis, highlighting the complex nature of activin in the regulation of proliferation and differentiation. We propose potential mechanisms for the way in which activins modify branching and address the issue of whether activin is a regulator of branching morphogenesis
Dental Pulp Cells Produce Neurotrophic Factors, Interact with Trigeminal Neurons in Vitro, and Rescue Motoneurons after Spinal Cord Injury

AbstractInteractions between ingrowing nerve fibers and their target tissues form the basis for functional connectivity with the central nervous system. Studies of the developing dental pulp innervation by nerve fibers from the trigeminal ganglion is an excellent example of nerve–target tissue interactions and will allow specific questions regarding development of the dental pulp nerve system to be addressed. Dental pulp cells (DPC) produce an array of neurotrophic factors during development, suggesting that these proteins might be involved in supporting trigeminal nerve fibers that innervate the dental pulp. We have established an in vitro culture system to study the interactions between the dental pulp cells and trigeminal neurons. We show that dental pulp cells produce several neurotrophic factors in culture. When DPC are cocultured with trigeminal neurons, they promote survival and a specific and elaborate neurite outgrowth pattern from trigeminal neurons, whereas skin fibroblasts do not provide a similar support. In addition, we show that dental pulp tissue becomes innervated when transplanted ectopically into the anterior chamber of the eye in rats, and upregulates the catecholaminergic nerve fiber density of the irises. Interestingly, grafting the dental pulp tissue into hemisected spinal cord increases the number of surviving motoneurons, indicating a functional bioactivity of the dental pulp-derived neurotrophic factors in vivo by rescuing motoneurons. Based on these findings, we propose that dental pulp-derived neurotrophic factors play an important role in orchestrating the dental pulp innervation
Multiple Inductive Signals Are Involved in the Development of the Ctenophore Mnemiopsis leidyi

AbstractCtenophores possess eight longitudinally arrayed rows of comb plate cilia. Previous intracellular cell lineage analysis has shown that these comb rows are derived from two embryonic lineages, both daughters of the four e1 micromeres (e11 and e12) and a single daughter of the four m1 micromeres (the m12 micromeres). Although isolated e1 micromeres will spontaneously generate comb plates, cell deletion experiments have shown that no comb plates appear during embryogenesis following the removal of e1 descendents. Thus, the m1 lineage requires the inductive interaction of the e1 lineage to contribute to comb plate formation. Here we show that, although m12 cells are normally the only m1 derivatives to contribute to comb plate formation, m11 cells are capable of generating comb plates in the absence m12 cells. The reason that m11 cells do not normally make comb rows may be attributable either to their more remote location relative to critical signaling centers (e.g., e1 descendants) or to inhibitory signals that may be provided by other nearby cells such as sister cells m12. In addition, we show that the signals provided by the e1 lineage are not sufficient for m1-derived comb plate formation. Signals provided by endomesodermal progeny of either the E or the M lineages (the 3E or 2M macromeres) are also required
Germ–Soma Differentiation in Volvox

AbstractVolvox carteri is a spherical green alga with a predominantly asexual mode of reproduction and a complete germ–soma division of labor. Its somatic cells are specialized for motility, incapable of dividing, and programmed to die when only a few days old, whereas its gonidia (asexual reproductive cells) are nonmotile, specialized for growth and reproduction, and potentially immortal. When a gonidium is less than 2 days old it divides to produce a juvenile spheroid containing all of the somatic cells and gonidia that will be present in an adult of the next generation. The first visible step in germ–soma differentiation is a set of asymmetric cleavage divisions in the embryo that set apart small somatic initials from their large gonidial-initial sister cells. Three types of genes have been found to play key roles in germ–soma specification. First a set of gls genes act in the embryos to shift cell-division planes, resulting in the asymmetric divisions that set apart the large–small sister-cell pairs. Then a set of lag genes act in the large cells to prevent somatic differentiation, while the regA gene acts in the small cells to prevent reproductive development. An inducible transposon was used to tag and recover some of these and other developmentally important genes. The glsA gene encodes a chaperone-like protein that, like another chaperone that is one of its putative binding partners, is associated with the cell division apparatus, although how this leads to asymmetric division remains to be elucidated. The regA gene encodes a somatic-cell-specific nuclear protein that appears to function by repressing genes required for chloroplast biogenesis, thereby preventing somatic cells from growing enough to reproduce. Somatic-cell-specific expression of regA is controlled by three intronic enhancers
Coronary Smooth Muscle Differentiation from Proepicardial Cells Requires RhoA-Mediated Actin Reorganization and p160 Rho-Kinase Activity

AbstractWe recently reported that the first detectable expression of SMC-specific proteins during coronary smooth muscle cell (CoSMC) differentiation from isolated proepicardial cells was restricted to cells undergoing epithelial-to-mesenchymal transformation (EMT). The objectives of this study were to examine more closely the relation between actin cytoskeletal rearrangements and serum response factor (SRF)-dependent transcription, and to specifically test whether rhoA–GTPase signaling is required for CoSMC differentiation. We report here that PDGF-BB stimulates EMT and promotes SRF-dependent expression of SMC marker genes calponin, SM22α, and SMγactin (SMγA) in proepicardial cells. C3 exoenzyme or rhoGDI, inhibitors of rhoA signaling, blocked PDGF-BB-induced EMT, prevented actin reorganization into stress fibers, and inhibited CoSMC differentiation. Incubation with the selective p160 rho-kinase (p160RhoK) inhibitor Y27632 (RKI) blocked EMT, prevented the appearance of calponin and SMγA-positive cells, and abolished expression and nuclear localization of SRF. To test the role of RhoK signaling for CoSMC differentiation in vivo, quail proepicardial organs (PEOs) were pretreated with RKI or vehicle and then grafted into age-matched host chick embryos to produce a chimeric epicardium. The ability of grafted cells to participate in coronary vessel formation was monitored by staining with antibodies for quail cell nuclear antigen and SMC marker proteins. Proepicardial cells pretreated with RKI failed to form CoSMCs in vivo. Time course studies traced this deficiency to a failure of epicardial-derived mesenchymal cells to migrate into or survive within the myocardium. In summary, these data point to important roles for rhoA–RhoK signaling in molecular pathways controlling cytoskeletal reorganization, SRF-dependent transcription, and cell survival that are required to produce CoSMCs from proepicardial cells