pinecone/core-2020-05-10-deduplication huggingface dataset:
Bmp6 and Bmp7 Are Required for Cushion Formation and Septation in the Developing Mouse Heart

AbstractThe mature heart valves and septa are derived from the cardiac cushions which initially form as local outgrowths of mesenchymal cells within the outflow tract and atrioventricular regions. Endocardial cells respond to signals from the overlying myocardium and undergo an epithelial-to-mesenchymal transformation to invade the intervening extracellular matrix. The molecules that can induce and maintain these cell populations are not known, but many candidates, including several TGFβs and BMPs, have been proposed based on their expression patterns and activities in other systems. In the present study, we describe the expression of Bmp6 and Bmp7 in overlapping and adjacent sites, including the cardiac cushions during mouse embryonic development. Previous analyses demonstrate that neither of these BMPs is required during cardiogenesis, but analysis of Bmp6;Bmp7 double mutants uncovers a marked delay in the formation of the outflow tract endocardial cushions. A proportion of Bmp6;Bmp7 mutants also display defects in valve morphogenesis and chamber septation, and the embryos die between 10.5 and 15.5 dpc due to cardiac insufficiency. These data provide the first genetic evidence that BMPs are involved in the formation of the cardiac cushions
Evidence for a Mesodermal Embryonic Regulator of the Sea Urchin CyIIa Gene

AbstractThe CyIIa gene of the sea urchin embryo is a model for study of cis-regulation downstream of cell-type specification, as CyIIa transcription follows the specification and initial differentiation of the embryonic domains in which it is expressed. These are the skeletogenic and secondary mesenchyme and gut. We carried out a detailed structural and functional analysis of a cis-regulatory region of this gene, extending 780 bp upstream and 125 bp downstream of the transcription start site, that had been shown earlier to reproduce faithfully the complex and dynamic CyIIa pattern of expression. This analysis revealed that the overall pattern of expression of the CyIIa gene appears to be governed mainly by two independent sets of DNA elements, which are target sites for specific proteins present in blastula-stage nuclear extract. One type of element, which controls a dynamic program of expression in both skeletogenic and secondary mesenchyme cells, contains the consensus-binding site for a member of the ets transcription factor family. The other, which is responsible for the terminal or permanent phase of CyIIa expression in the gut, shares homologies with the late module of the endoderm-specific Endo16 gene (endo16 Module B). Oligonucleotides containing replicas of these two target sites fused upstream of a sea urchin basal promoter are sufficient to confer accurate mesenchyme and late gut expression of an injected GFP construct. The finding of a single protein target site that recapitulates CyIIa expression in both primary and secondary mesenchyme cells suggests the existence of a pan-mesodermal gene expression program in the sea urchin embryo
CLIP-50 Immunolocalization during Mouse Spermiogenesis Suggests a Role in Shaping the Sperm Nucleus

AbstractThe spermatid nucleus and cytoplasm undergo dramatic morphological modifications during spermatid differentiation into mature sperm. Some of the external force causing this nuclear shaping is generated by a microtubular structure termed the manchette, which attaches to the perinuclear ring of the spermatid. Here, we report the isolation and characterization of a protein component of this perinuclear ring in an immunological screening of a mouse testis cDNA library. We termed this protein CLIP-50 because of its high similarity at the amino acid level to the C-terminal region of the microtubule-binding protein CLIP-170/restin. CLIP-50 lacks the characteristic microtubule-binding motif, but retains a portion of the predicted coiled–coiled domain and the metal-binding motif. The CLIP-50 transcript and protein are abundant in testis. The protein is also expressed in heart, lung, kidney, and skin. A distinct size variant exists in brain. In the spermatids, CLIP-50 protein localizes specifically to the centriolar region where the sperm tail originates and to the perinuclear ring from which the manchette emerges. CLIP-50 staining is retained in the ring throughout its migration over the surface of the nucleus which accompanies the nuclear shaping into its characteristic sperm configuration. This localization pattern indicates a very specific function for this novel CLIP derivative during mouse spermiogenesis
Ectopic Expression of the Arabidopsis AtMYB23 Gene Induces Differentiation of Trichome Cells

AbstractThe control of epidermal cell fate is a complex molecular process and requires the regulatory activity of different transcription factors. Here, we describe the isolation of a member of the Arabidopsis MYB transcription factor family, AtMYB23, that is involved in trichome development. Expression of the AtMYB23 gene under the control of the viral CaMV 35S promoter causes the development of ectopic trichomes. The formation of ectopic trichomes depends on TRANSPARENT TESTA GLABRA1 but not on GLABRA1. The absence of the negative regulator TRIPTYCHON leads to branching of the ectopic trichomes on cotyledons and the formation of ectopic trichomes in the leaf subepidermal cell layer. The CaMV 35S promoter-controlled expression of AtMYB23 can partially rescue the glabra1 mutant phenotype. Together, the presented data indicate that the AtMYB23 gene has partially overlapping functions with GLABRA1 in controlling the initiation of trichome development
Complementary Functions of Otx2 and Cripto in Initial Patterning of Mouse Epiblast

AbstractThe development of the mammalian antero-posterior (A-P) axis is proposed to be established by distinct anterior and posterior signaling centers, anterior visceral endoderm and primitive streak, respectively. Knock-out studies in mice have shown that Otx2 and Cripto have crucial roles in the generation and/or functions of these anterior and posterior centers, respectively. In both Otx2 and Cripto single mutants, the initial formation of the A-P axis takes place in a proximal–distal (P-D) orientation, but subsequent axis rotation fails to occur. To examine the developmental consequences of the lack of these two genes, we have analyzed the Otx2−/−;Cripto−/− double homozygous mutant phenotype. In the double mutants, the expression of the A-P axis markers Cer-l, Lim1, and Wnt3 was not induced, while expression of Fgf8 and T was expanded throughout the epiblast, indicating that the double mutants could not form the A-P axis even in its initial P-D orientation. In addition, the double mutants displayed defects in differentiation of the visceral endoderm overlying the epiblast, as well as in the extraembryonic ectoderm. Furthermore, differentiation of neuroectoderm was accelerated as judged by the reduction of Oct4 expression and emergence of Sox1 and Gbx2 expression in the double mutant epiblast. The resulting ectoderm only displayed characteristics of anterior hindbrain, implicating it as a ground state in the mammalian body plan. Our results indicate that complementary functions of Otx2 and Cripto are essential for initial patterning of the A-P axis in the mouse embryo
Regulation of dally, an Integral Membrane Proteoglycan, and Its Function during Adult Sensory Organ Formation of Drosophila

AbstractIn Drosophila, imaginal wing discs, Wg and Dpp, play important roles in the development of sensory organs. These secreted growth factors govern the positions of sensory bristles by regulating the expression of achaete-scute (ac-sc), genes affecting neuronal precursor cell identity. Earlier studies have shown that Dally, an integral membrane, heparan sulfate-modified proteoglycan, affects both Wg and Dpp signaling in a tissue-specific manner. Here, we show that dally is required for the development of specific chemosensory and mechanosensory organs in the wing and notum. dally enhancer trap is expressed at the anteroposterior and dorsoventral boundaries of the wing pouch, under the control of hh and wg, respectively. dally affects the specification of proneural clusters for dally-sensitive bristles and shows genetic interactions with either wg or dpp signaling components for distinct sensory bristles. These findings suggest that dally can differentially regulate Wg- or Dpp-directed patterning during sensory organ assembly. We have also determined that, for pSA, a bristle on the lateral notum, dally shows genetic interactions with iroquois complex (IRO-C), a gene complex affecting ac-sc expression. Consistent with this interaction, dally mutants show markedly reduced expression of an iro::lacZ reporter. These findings establish dally as an important regulator of sensory organ formation via Wg- and Dpp-mediated specification of proneural clusters
Misexpression of Noggin Leads to Septal Defects in the Outflow Tract of the Chick Heart

AbstractBMP-2 and BMP-4 are known to be involved in the early events which specify the cardiac lineage. Their later patterns of expression in the developing mouse and chick heart, in the myocardium overlying the atrioventricular canal (AV) and outflow tract (OFT) cushions, also suggest that they may play a role in valvoseptal development. In this study, we have used a recombinant retrovirus expressing noggin to inhibit the function of BMP-2/4 in the developing chick heart. This procedure resulted in abnormal development of the OFT and the ventricular septum. A spectrum of abnormalities was seen ranging from common arterial trunk to double outlet right ventricle. In hearts infected with noggin virus, where the neural crest cells have been labelled, the results show that BMP-2/4 function is required for the migration of neural crest cells into the developing OFT to form the aortopulmonary septum. Prior to septation, misexpression of noggin also leads to a decrease in the number of proliferating mesenchymal cells within the proximal cushions of the outflow tract. These results suggest that BMP-2/4 function may mediate several key events during cardiac development
Role of Thyroid Hormone Receptors in Timing Oligodendrocyte Differentiation

AbstractThe timing of oligodendrocyte differentiation is thought to depend on both intracellular mechanisms and extracellular signals. Thyroid hormone (TH) helps control this timing both in vitro and in vivo, but it is still uncertain how it does so. TH acts through nuclear receptors that are encoded by two genes, TRα and TRβ. Previous studies suggested that TRβ receptors may mediate the effect of TH on oligodendrocyte precursor cells (OPCs). Consistent with this possibility, we show here that overexpression of TRβ1 promotes precocious oligodendrocyte differentiation, whereas expression of two dominant-negative forms of TRβ1 greatly delays differentiation. Surprisingly, however, we find that postnatal TRβ−/− mice have a normal number of oligodendrocytes in their optic nerves and that TRβ−/− OPCs stop dividing and differentiate normally in response to TH in vitro. Moreover, we find that OPCs do not express TRβ1 or TRβ2 mRNAs, whereas they do express TRα1 and TRα2 mRNAs. These findings suggest that α receptors mediate the effect of TH on the timing of oligodendrocyte differentiation. We also show that TRα2 mRNA, which encodes a dominant-negative form of TRα, decreases as OPCs proliferate in vitro and in vivo. This decrease may help control when oligodendrocyte precursors differentiate
The Caenorhabditis elegans Gene lin-26 Can Trigger Epithelial Differentiation without Conferring Tissue Specificity

AbstractHow epithelial cell fates become specified is poorly understood. We have previously shown that the putative C2H2 zinc-finger transcription factor LIN-26 is required for the differentiation of ectodermal and mesodermal epithelial cells in Caenorhabditis elegans. Here, we report that ectopic LIN-26 expression during early gastrulation transforms most blastomeres into epithelial-like cells. Specifically, LIN-26 induced the expression of three epithelial markers: the adherens junction protein JAM-1; DLG-1, which is essential for the assembly of JAM-1 at junctions; and CHE-14, which is involved in apical trafficking. Furthermore, ultrastructural studies revealed that ectopic LIN-26 expression induced the formation of adherens-like junctions. However, ectopic lin-26 expression did not confer any tissue-specific cell fate, such as the epidermal cell fate, as evidenced from the observation that several epidermal-specific genes were not induced. Conversely, we show that epidermal cells displayed some polarity defects in lin-26 mutants. We conclude that lin-26 can induce epithelial differentiation and that epitheliogenesis is not a default pathway in C. elegans
A Novel Mode of Asymmetric Division Identifies the Fly Neuroglioblast 6-4T

AbstractAsymmetric cell divisions and segregation of fate determinants are crucial events in the generation of cell diversity. Fly neuroblasts, the precursors that self-reproduce and generate neurons, represent a clear example of asymmetrically dividing cells. Less is known about how neurons and glial cells are generated by multipotent precursors. Flies provide the ideal model system to study this process. Indeed, neuroglioblasts (NGBs) can be specifically identified and have been shown to require the glide/gcm fate determinant to produce glial cells, which otherwise would become neurons. Here, we follow the division of a specific NGB (NGB6-4T), which produces a neuroblast (NB) and a glioblast (GB). We show that, to generate the glioblast, glide/gcm RNA becomes progressively unequally distributed during NGB division and preferentially segregates. Subsequently, a GB-specific factor is required to maintain glide/gcm expression. Both processes are necessary for gliogenesis, showing that the glial vs. neuronal fate choice is a two-step process. This feature, together with glide/gcm subcellular RNA distribution and the behavior of the NGB mitotic apparatus identify a novel type of division generating cell diversity
Zebrafish fgf3 and fgf8 Encode Redundant Functions Required for Otic Placode Induction

AbstractMembers of the fibroblast growth factor (FGF) family of peptide ligands have been implicated in otic placode induction in several vertebrate species. Here, we have functionally analyzed the roles of fgf3 and fgf8 in zebrafish otic development. The role of fgf8 was assessed by analyzing acerebellar (ace) mutants. fgf3 function was disrupted by injecting embryos with antisense morpholino oligomers (MO) specifically designed to block translation of fgf3 transcripts. Disruption of either fgf3 or fgf8 causes moderate reduction in the size of the otic vesicle. Injection of fgf3-MO into ace/ace mutants causes much more severe reduction or complete loss of otic tissue. Moreover, preplacode cells fail to express pax8 and pax2.1, indicating disruption of early stages of otic induction in fgf3-depleted ace/ace mutants. Both fgf3 and fgf8 are normally expressed in the germring by 50% epiboly and are induced in the primordium of rhombomere 4 by 80% epibloy. In addition, fgf3 is expressed during the latter half of gastrulation in the prechordal plate and paraxial cephalic mesendoderm, tissues that either pass beneath or persist near the prospective otic ectoderm. Conditions that alter the pattern of expression of fgf3 and/or fgf8 cause corresponding changes in otic induction. Loss of maternal and zygotic one-eyed pinhead (oep) does not alter expression of fgf3 or fgf8 in the hindbrain, but ablates mesendodermal sources of fgf signaling and delays otic induction by several hours. Conversely, treatment of wild-type embryos with retinoic acid greatly expands the periotic domains of expression of fgf3, fgf8, and pax8 and leads to formation of supernumerary and ectopic otic vesicles. These data support the hypothesis that fgf3 and fgf8 cooperate during the latter half of gastrulation to induce differentiation of otic placodes
Microarray-Based Analysis of Early Development in Xenopus laevis

AbstractIn order to examine transcriptional regulation globally, during early vertebrate embryonic development, we have prepared Xenopus laevis cDNA microarrays. These prototype embryonic arrays contain 864 sequenced gastrula cDNA. In order to analyze and store array data, a microarray analysis pipeline was developed and integrated with sequence analysis and annotation tools. In three independent experimental settings, we demonstrate the power of these global approaches and provide optimized protocols for their application to molecular embryology. In the first set, by comparing maternal versus zygotic transcription, we document groups of genes that are temporally regulated. This analytical approach resulted in the discovery of novel temporally regulated genes. In the second, we examine changes in gene expression spatially during development by comparing dorsal and ventral mesoderm dissected from early gastrula embryos. We have discovered novel genes with spatial enrichment from these experiments. Finally, we use the prototype microarray to examine transcriptional responses from embryonic explants treated with activin. We selected genes (two of which are novel) regulated by activin for further characterization. All results obtained by the arrays were independently tested by RT-PCR or by in situ hybridization to provide a direct assessment of the accuracy and reproducibility of these approaches in the context of molecular embryology
Retinoic Acid Promotes Differentiation of Trophoblast Stem Cells to a Giant Cell Fate

AbstractTrophoblast stem cell (TS cell) lines have the ability to differentiate into trophoblast subtypes in vitro and contribute to the formation of placenta in chimeras. In order to investigate the possible role of retinoic acid (RA) in placentation, we analyzed the effects of exogenous RA on TS cells in vitro and the developing ectoplacental cone in vivo. TS cells expressed all subtypes of the retinoid receptor family, with the exception of RARβ, whose expression was stimulated in response to RA. TS cells treated with RA were compromised in their ability to proliferate and exhibited properties of differentiation into trophoblast giant cells. During TS cell differentiation into trophoblast subtypes induced by withdrawal of FGF4, RA treatment further illustrated its role in the specification of cell fate by the promotion of differentiation into giant cells and the suppression of spongiotrophoblast formation. Moreover, administration of RA during pregnancy resulted in the overabundance of giant cells at the expense of spongiotrophoblast cells. RA hereby acts as an extracellular signal whose potential function can be linked to specification events mediating trophoblast cell fate. Taken together with the spatial patterns of giant-cell formation and RA synthesis in vivo, these findings implicate a function for RA in giant-cell formation during placentation
Dynamic Domains of Gene Expression in the Early Avian Forebrain

AbstractThe expression domains of genes implicated in forebrain patterning often share borders at specific anteroposterior positions. This observation lies at the heart of the prosomeric model, which proposes that such shared borders coincide with proposed compartment boundaries and that specific combinations of genes expressed within each compartment are responsible for its patterning. Thus, genes such as Emx1, Emx2, Pax6, and qin (Bf1) are seen as being responsible for specifying different regions in the forebrain (diencephalon and telencephalon). However, the early expression of these genes, before the appearance of putative compartment boundaries, has not been characterized. In order to determine whether they have stable expression domains before this stage, we have compared mRNA expression of each of the above genes, relative both to one another and to morphological landmarks, in closely staged chick embryos. We find that, between HH stage 8 and HH stage 13, each of the genes has a dynamic spatial and temporal expression pattern. To test for autonomy of gene expression in the prosencephalon, we grafted tissue from this region to more caudal positions in the neural tube and analyzed for expression of Emx1, Emx2, qin, or Pax6. We find that gene expression is autonomous in prosencephalic tissue from as early as HH stage 8. In the case of Emx1, our data suggest that, from as early stage 8, presumptive telencephalic tissue also is committed to express this gene. We propose that early patterning along the anteroposterior axis of the presumptive telencephalon occurs across a field that is subdivided by different combinations of genes, with some overlapping areas, but without either sharp boundaries or stable interfaces between expression domains
Neurons and Glia in the Midline of the Higher Crustacean Orchestia cavimana Are Generated via an Invariant Cell Lineage That Comprises a Median Neuroblast and Glial Progenitors

AbstractMidline cells are a common feature of both insects and crustaceans. Midline cells in the insects Schistocerca americana and Drosophila melanogaster have been shown to give rise to pairs of either neurons or glial cells (midline precursor) as well as to repeatedly generate neurons (median neuroblast) or both neurons and glia (median neuroglioblast). This study addresses midline cell lineages in a higher crustacean, the amphipod Orchestia cavimana. In vivo labeling of single midline cells shows that the resulting cell lineage is invariant and that these cells act as progenitors for sets of three glial precursors and one median neuroblast. The progeny are restricted to parasegmental units. The glial precursors give rise to three pairs of glial cells; two of them enwrap the commissures. The median neuroblast gives rise to about 10 cells that differentiate into 3 classes of neurons. The presence of median neuroblasts is also shown for another higher crustacean, the isopod Porcellio scaber using BrdU labeling. This is the first study to analyze the cell lineage of crustacean neurons generated by early ectodermal precursors. A comparison with those of insects demonstrates both conservation and change during the evolution of arthropods
The Casein Kinase I Family: Roles in Morphogenesis

AbstractWnt signals play important roles in development and oncogenesis and are transduced through at least two pathways: a canonical β-catenin-dependent and a β-catenin-independent cascade. Casein kinase I (CKI) is required in both invertebrates and vertebrates to transduce canonical Wnt signals. However, its role in the β-catenin-independent pathway was unknown. During vertebrate embryogenesis, the β-catenin-independent cascade is thought to control cell movements and has been postulated to be analogous to the Drosophila planar cell polarity pathway, which signals through the JNK cascade. Here, we report that blocking CKI function inhibits embryonic morphogenesis and activates JNK in cell lines. These studies suggest that CKI might also act in the β-catenin-independent pathway and indicate a role for CKI during convergence extension in early vertebrate development