pinecone/core-2020-05-10-deduplication huggingface dataset:
Early Posterior/Ventral Fate Specification in the Vertebrate Embryo

AbstractOne of the central questions in developmental biology is that of how one cell can give rise to all specialized cell types and organs in the organism. Within the embryo, all tissues are composed of cells derived from one or more of the three germ layers, the ectoderm, the mesoderm, and the endoderm. Understanding the molecular events that underlie both the specification and patterning of the germ layers has been a long-standing interest for developmental biologists. Recent years have seen a rapid advancement in the elucidation of the molecular players implicated in patterning the vertebrate embryo. In this review, we will focus solely on the ventral and posterior fate acquisition in the ventral–lateral domains of the pregastrula embryo. We will address the embryonic origins of various tissues and will present embryological and experimental evidence to illustrate how “classically defined” ventral and posterior structures develop in all three germ layers. We will discuss the status of our current knowledge by focusing on the African frog Xenopus laevis, although we will also gather evidence from other vertebrates, where available. In particular, genetic studies in the zebrafish and mouse have been very informative in addressing the requirement for individual genes in these processes. The amphibian system has enjoyed great interest since the early days of experimental embryology, and constitutes the best understood system in terms of early patterning signals and axis specification. We want to draw interest to the embryological origins of cells that will develop into what we have collectively termed “posterior” and “ventral” cells/tissues, and we will address the involvement of the major signaling pathways implicated in posterior/ventral fate specification. Particular emphasis is given as to how these signaling pathways are integrated during early development for the specification of posterior and ventral fates
Involvement of Heparin-Binding EGF-like Growth Factor and Its Processing by Metalloproteinases in Early Epithelial Morphogenesis of the Submandibular Gland

AbstractIn the present study, the role of a member of the epidermal growth factor (EGF) family, heparin-binding EGF-like growth factor (HB-EGF), in organ development was investigated by using developing mouse submandibular gland (SMG), in which the EGF receptor signaling and heparan sulfate chains have been implicated. HB-EGF mRNA was detected in developing SMG by RT-PCR analysis and was expressed mainly in epithelium and weakly in mesenchyme of the embryonic SMG. Epithelial morphogenesis was inhibited by a synthetic peptide corresponding to the heparin-binding domain of HB-EGF and by anti-HB-EGF neutralizing antibody. An in vitro assay using an EGF receptor ligand-dependent cell line, EP170.7 cells, allowed us to detect the growth factor activity in SMG-conditioned media, which was significantly reduced by anti-HB-EGF antibody. Furthermore, treatment of SMG rudiments with the hydroxamate-based metalloproteinase inhibitor OSU8-1, which inhibits processing of EGFR ligands including HB-EGF, markedly diminished the growth factor activity in conditioned media and resulted in almost complete inhibition of SMG morphogenesis. The inhibitory effects on morphogenesis were reversed, though partially, by adding the soluble form of HB-EGF. Our results provide the first evidence that HB-EGF is a crucial regulator of epithelial morphogenesis during organ development, highlighting the importance of its processing by metalloproteinases
Iron Modulates the Differentiation of a Distinct Population of Glial Precursor Cells into Oligodendrocytes

AbstractIron deficiency in children is associated with a number of neural defects including hypomyelination. It has been hypothesized by others that this hypomyelination is due to a failure in myelin production. Other possibilities include failure in the generation of oligodendrocytes from their precursor cells or an interruption in oligodendrocyte maturation. These hypotheses are based on the observations that there is a peak in brain iron uptake in vivo that coincides with the period of greatest myelination and that a shortage of iron leads to myelination deficiency. We now demonstrate that iron availability modulates the generation of oligodendrocytes from tripotential-glial restricted precursor (GRP) cells isolated from the embryonic day 13.5 rat spinal cord. In contrast, we found no effects of iron on oligodendrocyte maturation or survival in vitro, nor did we find that increasing iron availability above basal levels increases oligodendrocyte generation from bipotential oligodendrocyte-type-2 astrocyte/oligodendrocyte precursor cells (O-2A/OPCs). Our results raise the possibility that iron may affect oligodendrocyte development at stages during early embryogenesis rather than during later development
Alkalinization of Acrosome Measured by GFP as a pH Indicator and Its Relation to Sperm Capacitation

AbstractWe previously targeted EGFP (a mutant of green fluorescent protein) to the lumen of the mouse sperm acrosome and reported the time course of EGFP release during the acrosome reaction. In the study reported here, we estimated the pH within the mouse sperm acrosome utilizing the pH-dependent nature of EGFP fluorescence. The average intra-acrosomal pH was estimated to be 5.3 ± 0.1 immediately after sperm preparation, gradually increasing to 6.2 ± 0.3 during 120 min of incubation in TYH media suitable for capacitation. Spontaneous acrosome reactions were noted to increase concomitantly with acrosomal alkalinization during incubation. We also demonstrated that acrosomal antigens detected by monoclonal antibodies MN7 and MC41 did not dissolve following the acrosome reaction in pH 5.3 media, but dissolved at pH 6.2. These data suggest that acrosomal alkalinization during incubation conducive for sperm capacitation may function to alter acrosomal contents and prepare them for release during the acrosome reaction
Thoracic Patterning by the Drosophila Gap Gene hunchback

AbstractLocalized gene expression patterns are critical for establishing body plans in all multicellular animals. In Drosophila, the gap gene hunchback (hb) is expressed in a dynamic pattern in anterior regions of the embryo. Hb protein is first detected as a shallow maternal gradient that prevents expression of posterior gap genes in anterior regions. hb mRNA is also expressed zygotically, first as a broad anterior domain controlled by the Bicoid (Bcd) morphogen, and then in a stripe at the position of parasegment 4 (PS4). Here, we show that the PS4-hb stripe changes the profile of the anterior Hb gradient by generating a localized peak of protein that persists until after the broad domain has started to decline. This peak is required specifically for the formation of the mesothoracic (T2) segment. At the molecular level, the PS4-hb stripe is critical for activation of the homeotic gene Antennapedia, but does not affect a gradient of Hb repressive activity formed by the combination of maternal and Bcd-dependent Hb. The repressive gradient is critical for establishing the positions of several target genes, including the gap genes Kruppel (Kr), knirps (kni), and giant (gt), and the homeotic gene Ultrabithorax (Ubx). Different Hb concentrations are sufficient for repression of gt, kni, and Ubx, but a very high level of Hb, or a combinatorial mechanism, is required for repression of Kr. These results suggest that the individual phases of hb transcription, which overlap temporally and spatially, contribute specific patterning functions in early embryogenesis
NF-κB Mediates FGF Signal Regulation of msx-1 Expression

AbstractThe nuclear factor-κB (NF-κB) family of transcription factors is involved in proliferation, differentiation, and apoptosis in a stage- and cell-dependent manner. Recent evidence has shown that NF-κB activity is necessary for both chicken and mouse limb development. We report here that the NF-κB family member c-rel and the homeodomain gene msx-1 have partially overlapping expression patterns in the developing chick limb. In addition, inhibition of NF-κB activity resulted in a decrease in msx-1 mRNA expression. Sequence analysis of the msx-1 promoter revealed three potential κB-binding sites similar to the interferon-γ (IFN-γ) κB-binding site. These sites bound to c-Rel, as shown by electrophoretic mobility shift assay (EMSA). Furthermore, inhibition of NF-κB activity significantly reduced transactivation of the msx-1 promoter in response to FGF-2/-4, known stimulators of msx-1 expression. These results suggest that NF-κB mediates the FGF-2/-4 signal regulation of msx-1 gene expression
Preoviposition Activation of Cathepsin-like Proteinases in Degenerating Ovarian Follicles of the Mosquito Culex pipiens pallens

AbstractWithin developing ovaries of many insects, some developing follicles or oocytes usually degenerate (follicular atresia or oosorption), while the others may continue to grow to maturity, thus maintaining the balance between the number of eggs and reproductive circumstances such as available nutrients. To help clarify the phenomenon of follicular atresia during ovarian development, we examined cysteine proteinases stored in mosquito Culex pipiens pallens ovaries. First, analysis using synthesized substrates showed that cathepsin B- and L-like proteinases gradually accumulated in the developing ovaries after a blood meal, which required more than 10 min of preincubation under acidic conditions to reach their maximum activities. However, homogenates of degenerating follicles 3 days after feeding showed proteolytic activities without acid treatment, suggesting that the proteinases had already been activated, while the extract of normally developing follicles collected from the same ovaries required more than 10 min of acid preincubation to reach the optimum activities, suggesting that the enzymes remained as inactive forms. Chemical and immunohistochemical analyses showed that more proteinases are located in the cytoplasm, rather than being associated with yolk granules. Ovarian proteinases, which are believed to become activated at the onset of embryogenesis, should also be activated during oogenesis, presumably to enhance oosorption
The BTB/POZ Domain of the Regulatory Proteins Bric à brac 1 (BAB1) and Bric à brac 2 (BAB2) Interacts with the Novel Drosophila TAFII Factor BIP2/dTAFII155

AbstractThe BTB/POZ domain is an evolutionarily conserved protein–protein interaction domain present in the N-terminal region of numerous transcription factors involved in development, chromatin remodeling, and human cancers. This domain is involved in homomeric and heteromeric associations with other BTB/POZ domains. The Drosophila BTB/POZ proteins Bric à brac 1 (BAB1) and Bric à brac 2 (BAB2) are developmentally regulated transcription factors which are involved in pattern formation along the proximo-distal axis of the leg and antenna, in the morphogenesis of the adult ovaries, and in the control of sexually dimorphic characters. We have identified partners of the BAB1 protein by using the two-hybrid system. The characterization of one of these proteins, called BIP2 for BAB Interacting Protein 2, is presented. BIP2 is a novel Drosophila TATA-box Protein Associated Factor (TAFII), also named dTAFII155. We show that the BTB/POZ domains of BAB1 and BAB2 are sufficient to mediate a direct interaction with BIP2/dTAFII155. This provides a direct link between these BTB/POZ transcription factors and the basal transcriptional machinery. We discuss the implications of the interaction between a BTB/POZ domain and a TAFII for the molecular mechanisms of transcriptional control mediated by BTB/POZ transcription factors
Regulatory Regions Driving Developmental and Tissue-Specific Expression of the Essential Pancreatic Gene pdx1

Abstractpdx1 (pancreatic and duodenal homeobox gene-1), which is expressed broadly in the embryonic pancreas and, later, in a more restricted manner in the mature β cells in the islets of Langerhans, is essential both for organ formation and β cell gene expression and function. We carried out a transgenic reporter gene analysis to identify region- and cell type-specific regulatory regions in pdx1. A 14.5-kb pdx1 genomic fragment corrected the glucose intolerance of pdx1+/− animals but, moreover, fully rescued the severe gut and pancreas defects in pdx1−/− embryos. Sequences sufficient to direct reporter expression to the entire endogenous pdx1 expression domain lie within 4.3 kb of 5′ flanking DNA. In this region, we identified two distinct fragments that drive reporter gene expression to different sets of islet neuroendocrine cells. One shows pan-endocrine cell specificity, the other is selectively activated in insulin-producing β cells. The endocrine-specific regulatory regions overlap a localized region of 5′ flanking DNA that is remarkably conserved in sequence between vertebrate pdx1 genes, and which has been associated with β cell-selective expression in cultured cell lines. This region contains potential binding sites for several transcription factors implicated in endodermal development and the pathogenesis of some forms of type-2 diabetes. These results are consistent with our previous proposal that conserved upstream pdx1 sequences exert control over pdx1 during embryonic organogenesis and islet endocrine cell differentiation. We propose that mutations affecting the expression and/or activity of transcription factors operating via these sequences may predispose towards diabetes, at least in part by direct effects on endocrine pdx1 expression
Elevated TGFβ Signaling Inhibits Ocular Vascular Development

AbstractAlterations in the ocular vasculature are associated with retinal diseases such as retinopathy of prematurity and diabetic retinopathy. Vascular endothelial growth factor (VEGF) as a potent stimulator for normal and abnormal vascular growth has been extensively studied. However, little is known about secreted factors that negatively regulate vascular growth in ocular tissues. We now report that expression of a self-activating TGFβ1 in the ocular lens of transgenic mice results in inhibition of retinal angiogenesis followed by retinal degeneration. Transgenic TGFβ1 can rescue the hyperplasic hyaloid tissue and reverse the corneal deficiency in TGFβ2-null embryos. These results demonstrate that TGFβ signaling modulates development of ocular vasculature and cornea in a dosage-dependent manner and that TGFβ1 can substitute for TGFβ2 in ocular tissues
Postmeiotic Unfertilized Starfish Eggs Die by Apoptosis

AbstractFertilization of starfish eggs during meiosis results in rapid progression to embryogenesis as soon as meiosis II is completed. Unfertilized eggs complete meiosis and arrest in postmeiotic interphase for an, until now, indeterminate time. If they remain unfertilized, the mature postmeiotic eggs ultimately die. The aim of this study is to characterize the mechanism of death in postmeiotic unfertilized starfish eggs. We report that, in two species of starfish, in the absence of fertilization, postmeiotic interphase arrest persists for 16–20 h, after which time the cells synchronously and rapidly die. Dying eggs extrude membrane blebs, undergo cytoplasmic contraction and darkening, and fragment into vesicles in a manner reminiscent of apoptotic cells. The DNA of dying eggs is condensed, fragmented, and labeled by the TUNEL assay. Taken together, these data suggest that the default fate of postmeiotic starfish eggs, like their mammalian counterparts, is death by apoptosis. We further report that the onset and execution of apoptosis in this system is dependent on ongoing protein synthesis and is inhibited by a rise in intracellular Ca2+, an essential component of the fertilization signaling pathway. We propose starfish eggs as a useful model to study developmentally regulated apoptosis
Hemangioblast Commitment in the Avian Allantois: Cellular and Molecular Aspects

AbstractWe recently identified the allantois as a site producing hemopoietic and endothelial cells capable of colonizing the bone marrow of an engrafted host. Here, we report a detailed investigation of some early cytological and molecular processes occurring in the allantoic bud, which are probably involved in the production of angioblasts and hemopoietic cells. We show that the allantois undergoes a program characterized by the prominent expression of several “hemangioblastic” genes in the mesoderm accompanied by other gene patterns in the associated endoderm. VEGF-R2, at least from stage HH17 onward, is expressed and is shortly followed by transcription factors GATA-2, SCL/tal-1, and GATA-1. Blood island-like structures differentiate that contain both CD45+ cells and cells accumulating hemoglobin; these structures look exactly like blood islands in the yolk sac. This hemopoietic process takes place before the establishment of a vascular network connecting the allantois to the embryo. As far as the endoderm is concerned, GATA-3 mRNA is found in the region where allantois will differentiate before the posterior instestinal portal becomes anatomically distinct. Shortly before the bud grows out, GATA-2 was expressed in the endoderm and, at the same time, the hemangioblastic program became initiated in the mesoderm. GATA-3 is detected at least until E8 and GATA-2 until E3 the latest stage examined for this factor. Using in vitro cultures, we show that allantoic buds, dissected out before the establishment of circulation between the bud and the rest of the embryo, produced erythrocytes of the definitive lineage. Moreover, using heterospecific grafts between chick and quail embryos, we demonstrate that the allantoic vascular network develops from intrinsic progenitors. Taken together, these results extend our earlier findings about the commitment of mesoderm to the endothelial and hemopoietic lineages in the allantois. The detection of a prominent GATA-3 expression restricted to the endoderm of the preallantoic region and allantoic bud, followed by that of GATA-2, is an interesting and novel information, in the context of organ formation and endoderm specification in the emergence of hemopoietic cells
α11β1 Integrin Is a Receptor for Interstitial Collagens Involved in Cell Migration and Collagen Reorganization on Mesenchymal Nonmuscle Cells

Abstractα11β1 integrin constitutes a recent addition to the integrin family. Here, we present the first in vivo analysis of α11 protein and mRNA distribution during human embryonic development. α11 protein and mRNA were present in various mesenchymal cells around the cartilage anlage in the developing skeleton in a pattern similar to that described for the transcription factor scleraxis. α11 was also expressed by mesenchymal cells in intervertebral discs and in keratocytes in cornea, two sites with highly organized collagen networks. Neither α11 mRNA nor α11 protein could be detected in myogenic cells in human embryos. The described expression pattern is compatible with α11β1 functioning as a receptor for interstitial collagens in vivo. To test this hypothesis in vitro, full-length human α11 cDNA was stably transfected into the mouse satellite cell line C2C12, lacking endogenous collagen receptors. α11β1 mediated cell adhesion to collagens I and IV (with a preference for collagen I) and formed focal contacts on collagens. In addition, α11β1 mediated contraction of fibrillar collagen gels in a manner similar to α2β1, and supported migration on collagen I in response to chemotactic stimuli. Our data support a role for α11β1 as a receptor for interstitial collagens on mesenchymally derived cells and suggest a multifunctional role of α11β1 in the recognition and organization of interstitial collagen matrices during development
Regulation of Prostate Branching Morphogenesis by Activin A and Follistatin

AbstractVentral prostate development occurs by branching morphogenesis and is an androgen-dependent process modulated by growth factors. Many growth factors have been implicated in branching morphogenesis including activins (dimers of βA and βB subunits); activin A inhibited branching of lung and kidney in vitro. Our aim was to examine the role of activins on prostatic development in vitro and their localization in vivo. Organ culture of day 0 rat ventral prostates for 6 days with activin A (+/− testosterone) inhibited prostatic branching and growth without increasing apoptosis. The activin-binding protein follistatin increased branching in vitro in the absence (but not presence) of testosterone, suggesting endogenous activins may reduce prostatic branching morphogenesis. In vivo, inhibin α subunit was not expressed until puberty, therefore inhibins (dimers of α and β subunits) are not involved in prostatic development. Activin βA was immunolocalized to developing prostatic epithelium and mesenchymal aggregates at ductal tips. Activin βB immunoreactivity was weak during development, but was upregulated in prostatic epithelium during puberty. Activin receptors were expressed throughout the prostatic epithelium. Follistatin mRNA and protein were expressed throughout the prostatic epithelium. The in vitro evidence that activin and follistatin have opposing effects on ductal branching suggests a role for activin as a negative regulator of prostatic ductal branching morphogenesis
Hoxb2 and Hoxb4 Act Together to Specify Ventral Body Wall Formation

AbstractThree different alleles of the Hoxb4 locus were generated by gene targeting in mice. Two alleles contain insertions of a selectable marker in the first exon in either orientation, and, in the third, the selectable marker was removed, resulting in premature termination of the protein. Presence and orientation of the selectable marker correlated with the severity of the phenotype, indicating that the selectable marker induces cis effects on neighboring genes that influence the phenotype. Homozygous mutants of all alleles had cervical skeletal defects similar to those previously reported for Hoxb4 mutant mice. In the most severe allele, Hoxb4PolII, homozygous mutants died eitherin utero at approximately E15.5 or immediately after birth, with a severe defect in ventral body wall formation. Analysis of embryos showed thinning of the primary ventral body wall in mutants relative to control animals at E11.5, before secondary body wall formation. Prior to this defect, both Alx3 and Alx4 were specifically down regulated in the most ventral part of the primary body wall in Hoxb4PolII mutants. Hoxb4loxp mutants in which theneo gene has been removed did not have body wall or sternum defects. In contrast, both the Hoxb4PolII and the previously described Hoxb2PolII alleles that have body wall defects have been shown to disrupt the expression of bothHoxb2 and Hoxb4 in cell types that contribute to body wall formation. Our results are consistent with a model in which defects in ventral body wall formation require the simultaneous loss of at least Hoxb2 and Hoxb4, and may involve Alx3 and Alx4