pinecone/core-2020-05-10-deduplication huggingface dataset:
The Murine Otp Homeobox Gene Plays an Essential Role in the Specification of Neuronal Cell Lineages in the Developing Hypothalamus

AbstractHypothalamic nuclei, including the anterior periventricular (aPV), paraventricular (PVN), and supraoptic (SON) nuclei strongly express the homeobox gene Orthopedia (Otp) during embryogenesis. Targeted inactivation of Otp in the mouse results in the loss of these nuclei in the homozygous null neonates. The Otp null hypothalamus fails to secrete neuropeptides somatostatin, arginine vasopressin, oxytocin, corticotropin-releasing hormone, and thyrotropin-releasing hormone in an appropriate spatial and temporal fashion, and leads to the death of Otp null pups shortly after birth. Failure to produce these neuropeptide hormones is evident prior to E15.5, indicating a failure in terminal differentiation of the aPV/PVN/SON neurons. Absence of elevated apoptotic activity, but reduced cell proliferation together with the ectopic activation of Six3 expression in the presumptive PVN, indicates a critical role for Otp in terminal differentiation and maturation of these neuroendocrine cell lineages. Otp employs distinct regulatory mechanisms to modulate the expression of specific molecular markers in the developing hypothalamus. At early embryonic stages, expression of Sim2 is immediately downregulated as a result of the absence of Otp, indicating a potential role for Otp as an upstream regulator of Sim2. In contrast, the regulation of Brn4 which is also expressed in the SON and PVN is independent of Otp function. Hence no strong evidence links Otp and Brn4 in the same regulatory pathway. The involvement of Otp and Sim1 in specifying specific hypothalamic neurosecretory cell lineages is shown to operate via distinct signaling pathways that partially overlap with Brn2
Regulation and Regeneration in the Ctenophore Mnemiopsis leidyi

AbstractLobate ctenophores (tentaculates) generally exhibit a remarkable ability to regenerate missing structures as adults. On the other hand, their embryos exhibit a highly mosaic behavior when cut into halves or when specific cells are ablated. These deficient embryos do not exhibit embryonic regulation, and generate incomplete adult body plans. Under certain conditions, however, these deficient animals are subsequently able to replace the missing structures during the adult phase in a process referred to as “post-regeneration.” We have determined that successful post-regeneration can be predicted on the basis of a modified polar coordinate model, and the rules of intercalary regeneration, as defined by French et al. (V. French, P. J. Bryant, and S. V. Bryant, 1976, Science 193, 969–981.) The model makes certain assumptions about the organization of the ctenophore body plan that fit well with what we have determined on the basis of cell lineage fates maps, and their twofold rotational (“biradial”) symmetry. The results suggest that cells composing the ctenophore adult body plan possess positional information, which is utilized to reconstruct the adult body plan. More specifically, we have found that the progeny of three specific cell lineages are required to support post-regeneration of the comb rows (the e1, e2, and m1 micromeres). Furthermore, post-regeneration of the comb rows involves a suite of cell–cell inductive interactions, which are similar to those that take place during their embryonic formation. The significance of these findings is discussed in terms of the organization of the ctenophore body plan, and the mechanisms involved in cell fate specification. This situation is also contrasted with that of the atentaculate ctenophores, which are unable to undergo post-regeneration
Homologs of Drosophila Appendage Genes in the Patterning of Arthropod Limbs

AbstractStudies of the genes involved in patterning the appendages of Drosophila melanogaster have revealed a system of signaling and transcriptional regulation that is responsible for specifying the proximo-distal limb axis. Here we report the expression patterns of presumptive homologs of the Drosophila genes extradenticle, dachshund, nubbin, ventral veins lacking (a.k.a. Cf1-a), and Dll in the limbs of the woodlouse Porcellio scaber and the spider Steatoda triangulosa. Although the expression domains of the appendage genes roughly correspond to those of Drosophila, their relative positions and segmental affiliation are distinct. In addition, the expression patterns of the appendage genes allows a resolution of the segmental composition of different appendages within crustacean and spider embryos. We conclude that certain limb types, e.g., mouthparts, appear to be derived from a leg-like ground-plan via the elimination/fusion of the intermediate and distal podomeres. Moreover, we observe just such a modification during the transformation of the anterior legs into mouthparts in P. scaber. Although our data do not unequivocally resolve the question of homology of the arthropod leg segments, they do provide evidence for a single conserved proximo-distal patterning system in the development of noninsect arthropod limbs
Dystroglycan Overexpression in Vivo Alters Acetylcholine Receptor Aggregation at the Neuromuscular Junction

AbstractDystroglycan is a member of the transmembrane dystrophin glycoprotein complex in muscle that binds to the synapse-organizing molecule agrin. Dystroglycan binding and AChR aggregation are mediated by two separate domains of agrin. To test whether dystroglycan plays a role in receptor aggregation at the neuromuscular junction, we overexpressed it by injecting rabbit dystroglycan RNA into one- or two-celled Xenopus embryos. We measured AChR aggregation in myotomes by labeling them with rhodamine–α-bungarotoxin followed by confocal microscopy and image analysis. Dystroglycan overexpression decreased AChR aggregation at the neuromuscular junction. This result is consistent with dystroglycan competition for agrin without signaling AChR aggregation. It also supports the hypothesis that dystroglycan is not the myotube-associated specificity component, (MASC) a putative coreceptor needed for agrin to activate muscle-specific kinase (MuSK) and signal AChR aggregation. Dystroglycan was distributed along the surface of muscle membranes, but was concentrated at the ends of myotomes, where AChRs normally aggregate at synapses. Overexpressed dystroglycan altered AChR aggregation in a rostral–caudal gradient, consistent with the sequential development of neuromuscular synapses along the embryo. Increasing concentrations of dystroglycan RNA did not further decrease AChR aggregation, but decreased embryo survival. Development often stopped during gastrulation, suggesting an essential, nonsynaptic role of dystroglycan during this early period of development
Root Hair Formation: F-Actin-Dependent Tip Growth Is Initiated by Local Assembly of Profilin-Supported F-Actin Meshworks Accumulated within Expansin-Enriched Bulges

AbstractPlant root hair formation is initiated when specialized elongating root epidermis cells (trichoblasts) assemble distinct domains at the plasma membrane/cell wall cell periphery complexes facing the root surface. These localities show accumulation of expansin and progressively transform into tip-growing root hair apices. Experimentation showed that trichoblasts made devoid of microtubules (MTs) were unaffected in root hair formation, whereas those depleted of F-actin by the G-actin sequestering agent latrunculin B had their root hair formation blocked after the bulge formation stage. In accordance with this, MTs are naturally depleted from early outgrowing bulges in which dense F-actin meshworks accumulate. These F-actin caps remain associated with tips of emerging and growing root hairs. Constitutive expression of the GFP-mouse talin fusion protein in transgenic Arabidopsis, which visualizes all classes of F-actin in a noninvasive mode, allowed in vivo confirmation of the presence of distinct F-actin meshworks within outgrowing bulges and at tips of young root hairs. Profilin accumulates, at both the protein and the mRNA levels, within F-actin-enriched bulges and at tips of emerging hairs. ER-based calreticulin and HDEL proteins also accumulate within outgrowing bulges and remain enriched at tips of emerging hairs. All this suggests that installation of the actin-based tip growth machinery takes place only after expansin-associated bulge formation and requires assembly of profilin-supported dynamic F-actin meshworks
Kheper, a Novel ZFH/δEF1 Family Member, Regulates the Development of the Neuroectoderm of Zebrafish (Danio rerio)

AbstractKheper is a novel member of the ZFH (zinc-finger and homeodomain protein)/δEF1 family in zebrafish. kheper transcripts are first detected in the epiblast of the dorsal blastoderm margin at the early gastrula stage and kheper is expressed in nearly all the neuroectoderm at later stages. kheper expression was expanded in noggin RNA-injected embryos and also in swirl mutant embryos and was reduced in bmp4 RNA-injected embryos and chordino mutant embryos, suggesting that kheper acts downstream of the neural inducers Noggin and Chordino. Overexpression of Kheper elicited ectopic expansion of the neuroectoderm-specific genes fkd3, hoxa-1, and eng3, and the ectopic expression of hoxa-1 was not inhibited by BMP4 overexpression. Kheper interacted with the transcriptional corepressors CtBP1 and CtBP2. Overexpression of a Kheper mutant lacking the homeodomain or of a VP16–Kheper fusion protein disturbed the development of the neuroectoderm and head structures. These data underscore the role of Kheper in the development of the neuroectoderm and indicate that Kheper acts as a transcriptional repressor
Keratin 9 Is a Component of the Perinuclear Ring of the Manchette of Rat Spermatids

AbstractPrevious work in our laboratory has shown that a 62- to 64-kDa protein was a major component of the perinuclear ring of manchettes fractionated from rat spermatids. Mass spectrometry analysis of this protein indicated the presence of a glycine-rich domain homologous to human keratin 9 (K9). Several antibodies to K9, raised against synthetic peptides of human K9, recognized the 64- to 62-kDa protein in the perinuclear ring of the manchette as well as in keratinocytes of the suprabasal layer of the rat and human footpad/sole epidermis in both immunoblotting and immunocytochemical experiments. Based on these data, human-derived K9 primers were used to clone rat K9 cDNA from epidermis by RT-PCR. Rat-specific K9 primers were then used to perform a two-step (nested) PCR to amplify the K9-specific rat testicular RNA and to obtain cDNA to demonstrate K9 gene expression in rat testis. The deduced amino acid sequence of rat K9 cDNA contains 618 amino acids with an estimated molecular mass of 63,020 Da, in agreement with that obtained by electrophoretic fractionation of rat manchette and epidermis footpad proteins. The deduced protein structure correlates with the recognizable pattern of keratins: a rod domain of 304 amino acids with well-conserved initiation and termination sequences (MQNLNSRLASY and EIETYRKLLEG, respectively), flanked by glycine/serine-rich head and tail domains of 141 and 173 amino acids, respectively. A high content of phenylalanine was detected in the head domain and a repetitive motif (SGGSYGGGS) in the tail domain. A comparison with human keratin 9 showed an overall nucleotide and amino acid similarity of 75%. An increased level of K9 transcripts was detected in a cDNA library prepared from fractionated round spermatids. Results of this study show that rat testis expresses K9 and that this protein is a component the perinuclear ring of the manchette of rat spermatids
Clonally Derived Human Embryonic Stem Cell Lines Maintain Pluripotency and Proliferative Potential for Prolonged Periods of Culture

AbstractEmbryonic stem (ES) cell lines derived from human blastocysts have the developmental potential to form derivatives of all three embryonic germ layers even after prolonged culture. Here we describe the clonal derivation of two human ES cell lines, H9.1 and H9.2. At the time of the clonal derivation of the H9.1 and H9.2 ES cell lines, the parental ES cell line, H9, had already been continuously cultured for 6 months. After an additional 8 months of culture, H9.1 and H9.2 ES cell lines continued to: (1) actively proliferate, (2) express high levels of telomerase, and (3) retain normal karyotypes. Telomere lengths, while somewhat variable, were maintained between 8 and 12 kb in high-passage H9.1 and H9.2 cells. High-passage H9.1 and H9.2 cells both formed teratomas in SCID-beige mice that included differentiated derivatives of all three embryonic germ layers. These results demonstrate the pluripotency of single human ES cells, the maintenance of pluripotency during an extended period of culture, and the long-term self-renewing properties of cultured human ES cells. The remarkable developmental potential, proliferative capacity, and karyotypic stability of human ES cells distinguish them from adult cells
Notch Regulates Cell Fate in the Developing Pronephros

AbstractThe mechanisms that regulate cell fate within the pronephros are poorly understood but are important for the subsequent development of the urogenital system and show many similarities to nephrogenesis in the definitive kidney. Dynamic expression of Notch-1, Serrate-1, and Delta-1 in the developing Xenopus pronephros suggests a role for this pathway in cell fate segregation. Misactivation of Notch signaling using conditionally active forms of either Notch-1 or RBP-J/Su(H) proteins prevented normal duct formation and the proper expression of genetic markers of duct cell differentiation. Inhibition of endogenous Notch signaling elicited the opposite effect. Taken together with the mRNA expression patterns, these data suggest that endogenous Notch signaling functions to inhibit duct differentiation in the dorsoanterior region of the anlage where cells are normally fated to form tubules. In addition, elevated Notch signaling in the pronephric anlage both perturbed the characteristic pattern of the differentiated tubule network and increased the expression of early markers of pronephric precursor cells, Pax-2 and Wilms' tumor suppressor gene (Wt-1). We propose that Notch signaling plays a previously unrecognized role in the early selection of duct and tubule cell fates as well as functioning subsequently to control tubule cell patterning and development
A Fate Map of Chick Otic Cup Closure Reveals Lineage Boundaries in the Dorsal Otocyst

AbstractThe vertebrate inner ear is structurally complex, consisting of fluid-filled tubules and sensory organs that subserve the functions of hearing and balance. The epithelial parts of the inner ear are derived from the otic placode, which deepens to form a cup before closing to form the otic vesicle. We fate-mapped the rim of the otic cup to monitor the cellular movements associated with otocyst formation and to aid in interpreting the changing gene expression patterns of the early otic field. Twelve sites around the rim, defined as positions of a clock face, were targeted by iontophoretic injection of fluorescent, lipophilic dye. Labeled cells were imaged 24 and 48 h after injection. The data show that the entire dorsal rim of the otic cup becomes the endolymphatic duct (ED), while the posteroventral rim becomes the lateral otocyst wall. Two intersecting boundaries of lineage restriction were identified near the dorsal pole: one bisecting the ED into anterior and posterior halves and the other defining its lateral edge. We hypothesize that signaling across compartment boundaries may play a critical role in duct specification. This model is discussed in the context of mouse mutants that are defective in both hindbrain development and ED outgrowth
The Murine Gene, Traube, Is Essential for the Growth of Preimplantation Embryos

AbstractLittle is known about the genetic control of preimplantation development. We have isolated, characterized, and mutated a previously undescribed mouse gene, Traube (Trb), essential for preimplantation development. Similar protein coding sequences are found in rats, humans, and yeast. The TRB protein contained two amino-terminal acidic domains, a leucine zipper, and three putative nuclear localization signals. The Trb gene was expressed at low levels ubiquitously early in development and became restricted to the liver and the central nervous system from E11.5 onward. Myc-tagged TRB protein was localized to the nucleus, and in a large proportion of the cells to the nucleoli. The Trb mutant embryos halted in development at the compacted morula stage at E2.5. At E3.5 they started to decompact and a day later they disintegrated and died. The observed defect was cell autonomous, as mutant cells failed to participate in the formation of chimeric embryos. The Trb mutant embryos showed a 50% reduction of the total cell number. The mutant embryos exhibited a paucity of ribosomes, polyribosomes, and rough endoplasmic reticulum. This paucity of ribosomes together with the localization of TRB to the nucleoli, the site of ribosome synthesis, suggests that TRB is involved in the synthesis of ribosomes
A Role for Cyclin J in the Rapid Nuclear Division Cycles of Early Drosophila Embryogenesis

AbstractThe nuclear division cycles of early Drosophila embryogenesis have a number of unique features that distinguish them from later cell cycles. These features include the lack of some checkpoints that operate in later cell cycles, the absence of gap phases, and very rapid DNA synthesis phases. The molecular mechanisms that control these rapid nuclear division cycles are poorly understood. Here we describe analysis of cyclin J, a previously uncharacterized cyclin which has an RNA expression pattern that suggests a possible role in early embryogenesis. We show that the cyclin J protein is present in early embryos where it forms active kinase complexes with cyclin-dependent kinase (Cdk) 2. To determine whether cyclin J plays a role in controlling the early nuclear cycles we isolated peptide aptamers that specifically bind to cyclin J and inhibit its ability to activate Cdks. We injected the inhibitory aptamers into syncytial Drosophila embryos and demonstrated that they caused defects in chromosome segregation and progression through mitosis. We obtained similar results by injecting cyclin J antibodies into embryos. Our results suggest that a cyclin J-associated kinase activity is required for the early embryonic division cycles
Expression of Activated MAP Kinase in Xenopus laevis Embryos: Evaluating the Roles of FGF and Other Signaling Pathways in Early Induction and Patterning

AbstractFGF signaling has been implicated in germ layer formation and axial determination. An antibody specific for the activated form of mitogen-activated protein kinase (MAPK) was used to monitor FGF signaling in vivo during early Xenopus development. Activation of MAPK in young embryos is abolished by injection of a dominant negative FGF receptor (XFD) RNA, suggesting that MAPK is activated primarily by FGF in this context. A transition from cytoplasmic to nuclear localization of activated MAPK occurs in morula/blastula stage embryo animal and marginal zones coinciding with the proposed onset of mesodermal competence. Activated MAPK delineates the region of the dorsal marginal zone before blastopore formation and persists in this region during gastrulation, indicating an early role for FGF signaling in dorsal mesoderm. Activated MAPK was also found in posterior neural tissue from late gastrulation onward. Inhibition of FGF signaling does not block posterior neural gene expression (HoxB9) or activation of MAPK; however, inhibition of FGF signaling does cause a statistically significant decrease in the level of activated MAPK. These results point toward the involvement of other receptor tyrosine kinase signaling pathways in posterior neural patterning
Dorsal and Lateral Fates in the Mouse Neural Tube Require the Cell-Autonomous Activity of the open brain Gene

AbstractThe processes that specify early regional identity in dorsal and lateral regions of the mammalian neural tube are not well understood. The mouse open brain (opb) gene plays an essential role in dorsal neural patterning: in the caudal spinal cord of opb mutants, dorsal cell types are absent and markers of ventral fates, including Shh, expand into dorsal regions. Analysis of the opb mutant phenotype and of opb/opb ↔ wild-type chimeric embryos reveals that early in neural development, the wild-type opb gene (opb+) is required cell autonomously for the expression of Pax7 in dorsal cells and Pax6 in lateral cells. Thus the opb+ gene product acts intracellularly in the reception or interpretation of signals that determine cell types in the dorsal 80% of the neural tube. At later stages, the lack of opb+ causes a non-cell-autonomous expansion of ventral cell types into dorsal regions of the neural tube, revealing that opb+ controls the production of a diffusible molecule that defines the domain of Shh expression. The data indicate that opb+ could act as either a novel component of a dorsalizing pathway or a novel intracellular negative regulator of the Shh signal transduction pathway
Degradation of Type IV Collagen by Matrix Metalloproteinases Is an Important Step in the Epithelial-Mesenchymal Transformation of the Endocardial Cushions

AbstractMorphogenesis of some tissues and organs in the developing embryo requires the transformation of epithelial cells into mesenchyme followed by cell motility and invasion of surrounding connective tissues. Details of the mechanisms involved in this important process are beginning to be elucidated. The epithelial-mesenchymal transformation (EMT) process involves many steps, one of which is the upregulation and activation of specific extracellular proteinases including members of the matrix metalloproteinase (MMP) family. Here we analyze the role of MMPs in the initiation of the mesenchymal cell phenotype in the developing heart, and find that they are necessary for the invasion of mesenchymal cells into the extracellular matrix of the endocardial cushion tissues. An important requirement in the formation of this mesenchyme is the turnover of type IV collagen along the basal surface of endocardial cells. In vitro experiments suggest that type IV collagen does not provide a suitable migratory substrate for endocardial cushion cells unless MMP-2 and MT-MMP are active. Relevant MMPs were found to be upregulated by factors known to be involved in the induction of the EMT such as TGFβ3. These results provide evidence of an important role for MMPs during a specific stage of the epithelial mesenchymal transformation in the embryonic heart, and suggest that specific cell-matrix interactions which facilitate cell migration only occur when the composition of the surrounding extracellular matrix is proteolytically altered