pinecone/core-2020-05-10-deduplication huggingface dataset:
Evidence for the Involvement of theGliGene Family in Embryonic Mouse Lung Development

AbstractMurineGli, Gli2,andGli3are zinc finger genes related toDrosophila cubitus interuptus,a component of thehedgehogsignal transduction pathway. In the embryonic lung, all threeGligenes are strongly expressed at the pseudoglandular stage, in distinct but overlapping domains of the mesoderm. Expression ofGliandGli3,but not ofGli2,is subsequently downregulated at the canalicular stage, coincident with a decline in the expression ofsonic hedgehog(Shh) and the hedgehog receptor gene,patched (Ptc).Overexpression ofShhin the lung results in increased levels ofPtcmRNA.Gli,but notGli2,is also upregulated, suggesting a differential involvement of theGligenes in the regulation ofPtcby SHH during lung development.Gli3is not upregulated byShhoverexpression. However, its importance for lung development is shown by the finding thatGli3XtJembryos, homozygous for a mutation involving a deletion of theGli3gene, have a stereotypic pattern of abnormalities in lung morphogenesis. The pulmonary defects in these embryos, consisting of localized shape changes and size reductions, correlate with normalGli3expression. Thus, our data indicate that one of theGligenes,Gli3,is essential for normal lung development, and that another,Gli,can be placed downstream ofShhsignaling in the lung
Continuous Observation of Multipotential Retinal Progenitor Cells in Clonal Density Culture

AbstractAll neural cell types in the vertebrate retina, except astrocytes, have been shown to develop from multipotential progenitor cells. It is not known, however, to what extent the progenitor cells are heterogeneous in their developmental potential or to what extent cell–cell interactions versus cell-autonomous factors influence the types of cells they become. To address these issues we developed a clonal-density cell culture system where mouse retinal progenitor cells can survive, divide, and differentiate. We followed the development of clones both by continuous time-lapse video microscopy and by daily microscopic observation. We show that even when cultured at clonal density in a homogeneous general environment, where they cannot contact cells outside their own clone, the retinal progenitor cells vary in proliferative capacity, cell cycle time, and in the cell types that they generate. In addition, we show that under these conditions single progenitor cells can generate both neurons and glia, in which case the neurons almost always develop before glial cells, as is the casein vivo
Hensen's Node Provides an Endogenous Limb-Forming Signal

AbstractAcquisition of limb-forming ability by discrete regions of the lateral plate of the chick embryo is thought to depend on a signaling cascade moving sequentially from the area of Hensen's node to the somitic mesoderm, the intermediate mesoderm, and then to the prospective limb-forming regions of the lateral plate (Stephenset al.,1991). In the present study it is demonstrated that grafts of Hensen's node can induce the formation of supernumerary rudimentary limbs from the non-limb-forming flank region of the lateral plate of stage 9–15 chick embryos. The rudimentary limbs that form from the flank in response to Hensen's node grafts often contain elongated, jointed cartilaginous elements arranged in three distinct proximodistal segments resembling the developing stylopod, zeugopod, and autopod and express the limb-characteristic genesMsx-2andBMP-4.However, the rudimentary limbs are incomplete and nonpolarized in that they do not form girdles or paired skeletal elements and fail to expresssonic hedgehog, FGF-4,andFGF-8,signaling molecules that have been implicated in regulating the patterning of the developing limb bud. These results indicate that Hensen's node can provide a limb-forming signal to the lateral mesoderm, but that other signals are necessary to promote the expression of genes required for the complete patterning and morphogenesis of the limb
A Role for Cyclin E/Cdk2 in the Timing of the Midblastula Transition inXenopusEmbryos

AbstractDuringXenopusdevelopment, the early cell cycles consist of rapid oscillations between DNA synthesis and mitosis until completion of the 12th mitotic division. Then the cycle lengthens and becomes asynchronous, zygotic transcription begins, and G phases are established, a period known as the midblastula transition (MBT). Some aspects of the MBT, such as zygotic transcription, depend on acquisition of a threshold nuclear to cytoplasmic (N/C) ratio, whereas others, such as maternal cyclin E degradation, are independent of nuclear events and appear to be controlled by an autonomous maternal timer. To investigate the function of cyclin E during the early cycles, cyclin E/Cdk2 kinase activity was specifically inhibited in fertilized eggs by a truncated form of theXenopusCdk inhibitor, Xic1 (Δ34Xic1). Δ34Xic1 caused lengthening of the embryonic cell cycles that correlated with increased levels of mitotic cyclins. However, DNA synthesis was not inhibited. Several hallmarks of the MBT were delayed for several hours in Δ34Xic1-injected embryos, including the disappearance of cyclins E and A, the initiation of zygotic transcription, and the reappearance of phosphotyrosine on Cdc2. In both control and Δ34Xic1-injected embryos, cyclin E was degraded after the 12th mitotic division as zygotic transcription began, but experiments with α-amanitin show that cyclin E degradation is not dependent on zygotic transcription. Thus, the length of the early cycles and the timing of maternal cyclin degradation depend upon cyclin E/Cdk2 activity. Neither oscillations in cyclin E/Cdk2 activity during the early cycles nor the disappearance of cyclin E at the MBT were dependent on protein synthesis. These data suggest that cyclin E/Cdk2 is directly linked to an autonomous maternal timer that drives the early embryonic cell cycles until the MBT
A Mutational Analysis of Conjugation inTetrahymena thermophila

AbstractConjugation in the freshwater ciliateTetrahymena thermophilainvolves a developmental program that models meiosis, fertilization, and early developmental events characteristic of multicellular eukaryotes. We describe a gallery of five early-acting conjugation mutations. These mutants,cnj1–5,exhibit phenotypes in which specific steps in the conjugal pathway have been altered or eliminated. Specifically,cnj1andcnj2fail to condense their micronuclear chromatin prior to each of the three prezygotic nuclear divisions. This results in nuclear division failure, failure to replicate DNA, and failure to initiate postzygotic development. Thecnj3mutant appears to exhibit a defect in chromosome separation during anaphase of mitosis.cnj4mutants successfully carry out meiosis I, yet are unable to execute the second meiotic division and abort all further development.cnj5mutants are unable to initiate either meiosis I or meiosis II, yet proceed to execute all subsequent developmental events. These mutant phenotypes are used to draw inferences regarding developmental dependencies that exist within the conjugation program
A Mutational Analysis of Conjugation inTetrahymena thermophila

AbstractConjugation following pair formation inTetrahymenacan be divided into three distinct sequences of events: prezygotic development, postzygotic development, and exconjugant development. The decision to proceed with postzygotic development is governed by a developmental checkpoint occurring sometime during the middle stages of conjugation. A second developmental decision is made to initiate pair separation and exconjugant development. This paper examines the phenotypes of five newly isolated conjugation mutants (cnj6–cnj10) which affect middle and late events within the conjugation program.cnj6mutants exhibit normal nuclear behavior throughout development up to and including differentiation of new macronuclear anlagen. Pairs arrest at this developmental endpoint, unable to dissociate.cnj7andcnj8eliminate the third prezygotic nuclear division and the first postzygotic nuclear division. All subsequent developmental events appear normal.cnj9eliminates the second postzygotic nuclear division, and subsequently, new macronuclei fail to develop despite parental macronuclear degradation.cnj10results in a pleiotropic phenotype characterized by failure of numerous events which all appear to involve nuclear–cytoskeletal interactions. These defects include nuclear selection (anchoring nuclei to the exchange junction), pronuclear exchange, pronuclear fusion, and anchoring postzygotic nuclear division products to the posterior cell cortex. These mutant phenotypes are used to draw inferences regarding developmental dependencies that govern a cell's entry into the postzygotic and exconjugant developmental programs
Specific Inhibition of Hair Follicle Formation by Epidermal Growth Factor in an Organ Culture of Developing Mouse Skin

AbstractEmbryonic mouse skin undergoes a drastic morphological change from 13 to 16 gestational days, i.e., formation of rudiments of hair follicles and stratification and cornification of interfollicular epidermis. To investigate underlying molecular mechanisms of the morphogenesis, we established an organ culture system that allows skin tissues isolated from 12.5- or 13.5-days postcoitus embryos to develop in a manner that is histologically and temporally similar to the processin vivo.Expression of differentiation markers of epidermal keratinocytes including cholesterol sulfotransferase and cytokeratin K1 was induced in culture, as it occurs alsoin vivo.The morphogenic process was observed by time-lapse videomicrography. In this culture system, epidermal growth factor (EGF) and transforming growth factor α specifically and completely inhibited the hair follicle formation with marginal effects on interfollicular epidermis. The inhibitory action by EGF was reversible and stage specific, i.e., at an early stage of the development of hair rudiments. Among known ligands to the EGF receptor, Schwannoma-derived growth factor and heparin-binding EGF were expressed inin vivoepidermis during the period of the initial formation of hair follicles. EGF receptor is expressed in epidermis throughout the developing period examined. Using an adenovirus vector, we demonstrated that the lacZ gene was transduced into the epidermal and dermal cell layers without appreciable toxicity. These results indicate that the present culture system provides a unique opportunity to investigate molecular mechanisms of skin morphogenesis including the role of EGF signaling under defined experimental conditions
Routes of Cl−Transport across the Trophectoderm of the Mouse Blastocyst

AbstractThe blastocyst stage of embryo development is characterized by a fluid-filled cavity called the blastocoel. Blastocoel formation requires vectorial Na+and Cl−transport and the accompanying osmotic accumulation of fluid. We found under conditions of low external Cl−that inhibitors of Cl−transport mechanisms inhibited blastocoel expansion, indicating a possible transcellular route for Cl−uptake across the outer epithelial layer (the trophectoderm). Using the Cl−-sensitive fluorophore,N-(6-methoxyquinolyl)acetoethyl ester, we found that Cl−efflux from the blastocoel can occur via pathways with properties that resemble both HCO−3/Cl−exchange and Cl−channels, as well as by another yet uncharacterized pathway. In contrast, Cl−re-uptake into Cl−-depleted blastocoels (the physiologically relevant direction for Cl−transport during blastocoel expansion) occurred only via the channel-like mechanism. Patch-clamp recordings detected a component of current carried by apical Cl−channels. Intracellular pH measurements during external Cl−removal detected HCO−3/Cl−exchange activity in collapsed blastocysts but little in intact blastocysts, suggesting predominantly basolateral HCO−3/Cl−exchange activity. This was corroborated by the immunolocalization of the AE2 isoform of HCO−3/Cl−exchanger to the basolateral surface of the trophectoderm. Thus, it appears that Cl−transport into the blastocoel may occur via apical Cl−channels, while efflux also involves a basolateral HCO−3/Cl−exchanger
Regulation of Epidermal Induction by BMP2 and BMP7 Signaling

AbstractThe specification of neural fate inXenopusembryos has been shown to be under regulation by negative factors. The secreted protein bone morphogenetic protein-4 (BMP4) has been identified as one of these factors: in the early gastrula ectoderm, BMP4 can both inhibit neural fate and induce epidermis. In this study, we show that two otherXenopusBMP genes, BMP2 and BMP7, are endowed with the same types of activities. First, we show that expression of a dominant negative form of the BMP2 ligand, which blocks normal processing of the wild-type ligand, causes neuralization ofXenopusectoderm. Second, we have isolated theXenopusBMP2/7 receptor (XALK2) and generated a constitutively active mutant that signals in a ligand-independent manner. We show that signals from the activated BMP2/7 receptor also inhibit neuralization and induce epidermis in dissociated ectoderm cells. Consistent with both findings we show that secreted BMP2 and BMP7 ligands can also mediate neural inhibition and epidermal induction. These results suggest that both BMP2 and BMP7 may be involved independently or together with BMP4 in the inhibition of the neural fate and the onset of the epidermal induction pathwayin vivo.This further supports the idea that epidermal induction is due to the effects of multiple signals from heterogeneous BMP genes
Cell Fate Maps in theIlyanassa obsoletaEmbryo beyond the Third Division

AbstractIn the gastropodIlyanassa obsoleta,early development is mediated by the polar lobe, which shunts determinants to the D lineage during the first two cleavages. These determinants act to specify cell fates directly within the D lineage and to specify cell fates inductively in other lineages of the embryo. Most fate maps inI. obsoletahave been inferred from previous cell ablation experiments, although Render (1991) completed natural fate maps for the first quartet of micromeres. Here this work has been extended to include second and third quartet micromeres as well as the mesentoblast cell (4d) and some of its derivatives and selected macromeres. Fate maps were created by injecting individual cells with Lucifer Yellow dextran via iontophoresis and by analyzing patterns of fluorescence in resulting veliger larvae. In general, second quartet micromeres make major contributions to the shell-forming mantle, the velum, the stomodeum and the heart. Third quartet micromeres give rise to large areas of the foot, velum, esophagus and heart. The mesentoblast cell, 4d, contributes to retractor muscles, heart, larval kidney and intestine. These results are discussed in terms of previous ablation experiments and mechanisms of cell fate specification in theI. obsoletaembryo
Genes Induced in Programmed Cell Death of Neuronal PC12 Cells and Developing Sympathetic Neuronsin Vivo

AbstractTo identify primary response genes induced during early stages of neuronal programmed cell death (PCD), we screened by differential hybridization a subtracted cDNA library prepared from neuronal PC12 cells deprived of NGF for 6 hr in the presence of cycloheximide. Eight induced cDNA sequences were identified and designatedmessage up-regulated during death (mud)-1–8.To determine which cloned sequences might be involved in neuronal PCDin vivo,expression ofmudgenes was analyzed in developing rat superior cervical ganglia (SCG) undergoing programmed cell death, using a combination of reverse Southern, reverse transcription polymerase chain reaction (RT-PCR), andin situhybridization. Five sequences (mud-1, -3, -5/8, -6,and-7) are induced in SCG undergoing cell deathin vivo,and induction of at least three of these (mud-3, -6, and -7) occurs in neurons. Partial sequence analysis reveals thatmud-1corresponds toannexin VI; mud-3corresponds to ratPC3,mouseTIS21; mud-4appears to be the rat homolog of humanTAFII70; mud-5and-8are >85% identical members of the rodent gene family of B2-transcribed repeats; andmud-6appears to be the rat homolog of humanRing 3and Drosophilafemale sterile homeotic(fsh).Mud-2andmud-7encode novel sequences. These new candidate genes provide markers for early stages of neuronal PCD, are potentially involved in the cell death process, and serve to expand our view of cell death control in the developing nervous system
Differential Dependency of Cutaneous Mechanoreceptors on Neurotrophins, trk Receptors, and P75 LNGFR

AbstractThe impact of null mutations of the genes for the NGF family of neurotrophins and their receptors was examined among the wide variety of medium to large caliber myelinated mechanoreceptors which have a highly specific predictable organization in the mystacial pad of mice. Immunofluorescence with anti-protein gene product 9.5, anti-200-kDa neurofilament protein (RT97), and anti-calcitonin gene-related product was used to label innervation in mystacial pads from mice with homozygous null mutations for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), the three tyrosine kinase receptors (trkA, trkB, trkC), and the low-affinity nerve growth factor receptor p75. Specimens were sacrificed at birth and at 1, 2, and 4 weeks for each type of mutation as well as at 11 weeks and 1 year for p75 and trkC mutations, respectively. Our results demonstrate several major concepts about the role of neurotrophins in the development of cutaneous mechanoreceptors that are supplied by medium to large caliber myelinated afferents. First, each of the high-affinity tyrosine kinase receptors, trkA, trkB, and trkC, as well as the low-affinity p75 receptor has an impact on at least one type of mechanoreceptor. Second, consistent with the various affinities for particular trk receptors, the elimination of NGF, BDNF, and NT-3 has an impact comparable to or more complex than the absence of their most specific high-affinity receptors: trkA, trkB, and trkC, respectively. These complexities include potential NT-3 signaling through trkA and trkB to support some neuronal survival. Third, most types of afferents are dependent on a different combination of neurotrophins and receptors for their survival: reticular and transverse lanceolate afferents are dependent upon NT-3, NGF, and trkA; Ruffini afferents upon BDNF and trkB; longitudinal lanceolate afferents upon NGF, trkA, BDNF, and trkB; and Merkel afferents on NGF, trkA, NT-3, trkC, and p75. NT-4 has no obvious detrimental impact on the mechanoreceptor development in the presence of BDNF. Fourth, NT-4 and BDNF signaling through trkB may suppress Merkel innervation and NT-3 signaling through trkC may suppress Ruffini innervation. Finally, regardless of the neurotrophin/receptor dependency for afferent survival and neurite outgrowth, NT-3 has an impact on the formation of all the sensory endings. In the context of these findings, indications of competitive and suppressive interactions that appear to regulate the balance of innervation density among the various sets of innervation were evident
Arrowhead Encodes a LIM Homeodomain Protein That Distinguishes Subsets of Drosophila Imaginal Cells

AbstractTheArrowheadgene encodes a LIM-homeodomain transcription factor required for establishment of a subset of imaginal tissues: the abdominal histoblasts and the salivary gland imaginal rings. Consistent with its role in development, during embryogenesisArrowheadis expressed in each abdominal segment and in the labial segment. Late in embryonic development, expression is refined to the abdominal histoblasts and salivary gland imaginal ring cells themselves. When ectopically expressed in imaginal disc cells,Arrowheadcauses programmed cell death and loss of corresponding adult structures. Therefore,Arrowheadexpression is required for development of one set of imaginal cells and is incompatible with development of another, emphasizing the specificity ofArrowheadand the sensitivity of different target cells to its expression. Loss-of-function mutations inArrowheadaffect conserved or invariant amino acids in the LIM- and homeo-domains demonstrating the importance of these residues in LIM homeodomain protein activity
The Embryonic Central Nervous System Lineages ofDrosophila melanogaster

AbstractInDrosophila,central nervous system (CNS) formation starts with the delamination from the neuroectoderm of about 30 neuroblasts (NBs) per hemisegment. They give rise to approximately 350 neurons and 30 glial cells during embryonic development. Understanding the mechanisms leading to cell fate specification and differentiation in the CNS requires the identification of the NB lineages. The embryonic lineages derived from 17 NBs of the ventral part of the neuroectoderm have previously been described (Bossinget al.,1996). Here we present 13 lineages derived from the dorsal part of the neuroectoderm and we assign 12 of them to identified NBs. Together, the 13 lineages comprise approximately 120 neurons and 22 to 27 glial cells which we include in a systematic terminology. Therefore, NBs from the dorsal neuroectoderm produce about 90% of the glial cells in the embryonic ventral ganglion. Two of the NBs give rise to glial progeny exclusively (NB 6-4A, GP) and five to glia as well as neurons (NBs 1-3, 2-5, 5-6, 6-4T, 7-4). These seven NBs are arranged as a group in the most lateral region of the NB layer. The other lineages (NBs 2-4, 3-3, 3-5, 4-3, 4-4, 5-4, clone y) are composed exclusively of neurons (interneurons, motoneurons, or both). Additionally, it has been possible to link the lateral cluster ofeven-skippedexpressing cells (EL) to the lineage of NB 3-3. Along with the previously described clones, the vast majority (more than 90%) of cell lineages in the embryonic ventral nerve cord (thorax, abdomen) are now known. Moreover, previously identified neurons and most glial cells are now linked to certain lineages and, thus, to particular NBs. This complete set of data provides a foundation for the interpretation of mutant phenotypes and for future investigations on cell fate specification and differentiation
TPromoter Activity in the Absence of Functional T Protein during Axis Formation and Elongation in the Mouse

AbstractTheT(Brachyury) gene, which encodes a transcription factor, is involved in the formation of posterior mesoderm. Although studies inXenopushave shown thatTgene expression is responsive to mesoderm inducing factors and furthermore suggest the existence of an autoregulatory loop involving T itself, eFGF, and the FGF receptor, little is known about the regulation ofTexpression in the mouse. We report here that in the mouse the expression offgf-4,the putative homologue ofXenopus efgf,is not dependent on the presence of T protein during the first 48 hr of gastrulation. Furthermore, we address the question of autoregulation using a chimeric approach. Introduction of aTpromoter–lacZconstruct intoT/TES cells results inTpromoter activity in the primitive streak and tail bud in the absence of functional T protein. Therefore, we suggest that a direct FGF and T autoregulatory loop is unlikely to operate during gastrulation and axis elongation in the mouse