bluuebunny/crossref_metadata_2025_split huggingface dataset:
Signal transduction during shrimp oocyte activation by extracellular Mg2+: roles of inositol 1,4,5-trisphosphate, tyrosine kinases and G-proteins
Authors: Lindsay LeAnn L. , Clark Wallis H. 
Published: April 2021

ABSTRACT
Oocytes of the shrimp Sicyoniaingentis are naturally activated upon contact with seawater Mg2+. We investigated the mechanism of Mg2+-induced intracellular Ca2+ release and cortical contraction through treatment of oocytes with various activators and inhibitors of signal transduction pathways. Injection of oocytes with the second messenger inositol 1,4,5-trisphosphate resulted in an immediate rise in intracellular Ca2+ and normal cortical contraction. By contrast, injection of the GTP analog guanosine 5′-O-(3′-thiotriphosphate) to activate G-proteins did not affect intracellular Ca2+ levels but did induce cortical contraction. Tyrosine kinase inhibitors (tyrphostin and staurosporine) suppressed the Mg2+-induced Ca2+ rise and contraction, and the inhibition could be overcome by injection with inositol 1,4,5-trisphosphate. Immunoprecipitation of phosphotyrosine-containing proteins from oocyte lysates showed that a 110×103Mr protein was phosphorylated within seconds of oocyte exposure to Mg2+, and tyrphostin inhibited the phosphorylation of this protein. Pre-treatment of oocytes with the protease trypsin abolished their ability to release Ca2+ in response to extracellular Mg2+, indicating a role for a cell surface protein during normal oocyte activation; treated oocytes could be rescued by inositol 1,4,5-trisphosphate injection. These results suggest that S. ingentis oocytes are activated through a Mg2+ ‘receptor’ which activates a tyrosine kinase and results in the production of inositol 1,4,5-trisphosphate to release intracellular Ca2+ stores and induce cortical con-traction. A G-protein/GTPase may also be involved in the pathway leading to cortical contraction.
FGF2 regulates proliferation of neural crest cells, with subsequent neuronal differentiation regulated by LIF or related factors
Authors: Murphy Mark , Reid Kate , Ford Miriam , Furness John B. , Bartlett Perry F. 
Published: April 2021

ABSTRACT
Two of the key early events in the development of the peripheral nervous system are the proliferation of neural crest precursor cells and their subsequent differentiation into different neural cell types. We present evidence that members of the fibroblast growth factor family, (FGF1 or FGF2) act directly on the neural crest cells in vitro to stimulate proliferation in the presence of serum. These findings correlate with in situ hybridisation analysis, which shows FGF2 mRNA is expressed in cells both in the neural tube and within newly formed sensory ganglia (dorsal root ganglia, DRG) at embryonic day 10 in the mouse, when neural crest precursors are proliferating within the DRG. This data infers an autocrine/paracrine loop for FGF regulation of proliferation. Evidence supporting this notion is provided by the finding that part of the endogenous proliferative activity in the NC cultures is related to FGF. It was also found, in early neural crest cultures, that exogenous FGF completely inhibited neuronal differentiation, probably as a direct consequence of its mitogenic activity. In order to stimulate neuronal differentiation significantly, it was necessary to remove the FGF and replace it with leukemia inhibitory factor (LIF) or related factors. Under these conditions, 50% of the cells differentiated into neurons, which developed a sensory neuron morphology and were immunoreactive for the sensory markers CGRP and substance P. These data support a model of neural crest development, whereby multipotential neural crest precursor cells are stimulated to divide by FGF and subsequent development into sensory neurons is regulated by LIF or other cytokines with a similar signalling mechanism.
Regulation of scute function by extramacrochaete in vitro and in vivo
Authors: Cabrera Carlos V. , Alonso María C. , Huikeshoven Hella 
Published: April 2021

ABSTRACT
The pattern of adult sensilla in Drosophila is established by the dosage-sensitive interaction of two antagonistic groups of genes. Sensilla development is promoted by members of the achaete-scute complex and the daughterless gene whereas it is suppressed by whereas extramacrochaete (emc) and hairy. All these genes encode helix-loop-helix proteins. The products of the achaete-scute complex and daughterless interact to form heterodimers able to activate transcription. In this report, we show that (1) extra-macrochaete forms heterodimers with the achaete, scute, lethal of scute and daughterless products; (2) extra-macrochaete inhibits DNA-binding of Achaete, Scute and Lethal of Scute/Daughterless heterodimers and Daughter-less homodimers and (3) extramacrochaete inhibits tran-scription activation by heterodimers in a yeast assay system. In addition, we have studied the expression patterns of scute in wild-type and extramacrochaete mutant imaginal discs. Expression of scute RNA during imaginal development occurs in groups of cells, but high levels of protein accumulate in the nuclei of only a subset of the RNA-expressing cells. The pattern is dynamic and results in a small number of protein-containing cells that correspond to sensillum precursors. extramacrochaete loss-of-function alleles develop extra sensilla and correspondingly display a larger number of cells with scute protein. These cells appear to arise from those that in the wild type already express scute RNA; hence, extramacrochaete is a repressor of scute function whose action may take place post-tran-scriptionally.
Regulation of a decapentaplegic midgut enhancer by homeotic proteins
Authors: Manak J. Robert , Mathies Laura D. , Scott Matthew P. 
Published: April 2021

ABSTRACT
The clustered homeotic genes encode transcription factors that regulate pattern formation in all animals, conferring cell fates by coordinating the activities of downstream ‘target’ genes. In the Drosophila midgut, the Ultrabithorax (Ubx) protein activates and the abdominalA (abd-A) protein represses transcription of the decapentaplegic (dpp) gene, which encodes a secreted signalling protein of the TGFβ class. We have identified an 813 bp dpp enhancer which is capable of driving expression of a lacZ gene in a correct pattern in the embryonic midgut. The enhancer is activated ectopically in the visceral mesoderm by ubiquitous expression of Ubx or Antennapedia but not by Sex combs reduced protein. Ectopic expression of abd-A represses the enhancer. Deletion analysis reveals regions required for repression and activation. A 419 bp subfragment of the 813 bp fragment also drives reporter gene expression in an appropriate pattern, albeit more weakly. Evolutionary sequence conservation suggests other factors work with homeotic proteins to regulate dpp. A candidate cofactor, the extradenticle protein, binds to the dpp enhancer in close proximity to homeotic protein binding sites. Mutation of either this site or another conserved motif compromises enhancer function. A 45 bp fragment of DNA from within the enhancer correctly responds to both UBX and ABD-A in a largely tissue-specific manner, thus representing the smallest in vivo homeotic response element (HOMRE) identified to date.
Isoform-specific induction of a retinoid-responsive antigen after biolistic transfection of chimaeric retinoic acid/thyroid hormone receptors into a regenerating limb
Authors: Pecorino Lauren T. , Lo Donald C. , Brockes Jeremy P. 
Published: April 2021

ABSTRACTRetinoic acid (RA) induces secretory differentiation in the wound epidermis of a regenerating amphibian limb. We investigated the role of individual RA receptor (RAR) types in the newt wound epidermis by introducing chimaeric RA/thyroid hormone (T3) receptors (χ α1 and χ δ1) that can be activated by T3. A biolistic particle delivery system was employed to transfect cells in the wound epidermis of a regenerating limb and approximately 10% of the cells in targeted surface areas expressed marker genes. Both χ α1 and χ δ1 were comparable in their ability to stimulate transcription of a synthetic reporter construct through a RA response element after activation with T3 in situ. This activation was also comparable to that obtained by the endogenous complement of RARs in the RA-treated, transfected wound epidermis. The RA-inducible WE3 antigen, a marker for secretory differentiation, which distinguishes the wound epidermis from normal skin (Tassava, R. A., Johnson-Wint, B. and Gross, J. 1986, J. Exp. Zool. 239, 229-240), was used to assess the functional role of χ α1 and χ δ1. Chimaeric receptors were transfected with an alkaline phosphatase marker gene, activated with T3, and the expression of both the marker and WE3 was analyzed by double-label immunofluorescence. Newt limbs transfected with χδ1 showed many double-labelled cells dependent on the presence of T3, whereas contralateral limbs transfected with an alkaline phosphatase marker lacking chimaeric receptor sequences did not. Limbs transfected with χ α1 did not show double-labelled cells in the presence or absence of T3, whereas in an earlier study χ α1, and not χ δ1, inhibited growth. These results indicate that specific effects of RA can be mediated by particular types of RARs and demonstrate a novel approach for studying the action of RA on its target tissues.
Overlapping patterns of IGF2 and H19 expression during human development: biallelic IGF2 expression correlates with a lack of H19 expression
Authors: Ohlsson Rolf , Hedborg Fredrik , Holmgren Lars , Walsh Colum , Ekström Tomas J. 
Published: April 2021

ABSTRACT
The spatial patterns of IGF2 and H19 gene expression are strikingly similar during parts of human embryonic/fetal and early postnatal development. Notable exceptions were found with the ciliary anlage of the embryonic retina and the choroid plexus/leptomeninges, where transcripts from the IGF2 but not the H19 locus could be detected. Moreover, in contrast to the other tissue samples examined, the choroid plexus/leptomeninges expressed both parental IGF2 alleles. Whilst RNase protection analysis revealed a weak activity of the P1 promoter in the choroid plexus/leptomeninges, the P2, P3 and P4 promoters were all active wherever IGF2 was expressed. We discuss these observations with respect to a hypothesized coordinated control of the reciprocally imprinted and closely linked IGF2 and H19 loci.
Expression of maize KNOTTED1 related homeobox genes in the shoot apical meristem predicts patterns of morphogenesis in the vegetative shoot
Authors: Jackson David , Veit Bruce , Hake Sarah 
Published: April 2021

ABSTRACT
In this paper we describe the expression patterns of a family of homeobox genes in maize and their relationship to organogenic domains in the vegetative shoot apical meristem. These genes are related by sequence to KNOTTED1, a gene characterized by dominant neomorphic mutations which perturb specific aspects of maize leaf development. Four members of this gene family are expressed in shoot meristems and the developing stem, but not in determinate lateral organs such as leaves or floral organs. The genes show distinct expression patterns in the vegetative shoot apical meristem that together predict the site of leaf initiation and the basal limit of the vegetative ‘phytomer’ or segmentation unit of the shoot. These genes are also expressed in the inflorescence and floral meristems, where their patterns of expression are more similar, and they are not expressed in root apical meristems. These findings are discussed in relation to other studies of shoot apical meristem organization as well as possible commonality of homeobox gene function in the animal and plant kingdoms.
Induction of chondrogenesis: requirement for synergistic interaction of basic fibroblast growth factor and transforming growth factor-beta
Authors: Frenz Dorothy A. , Liu Wei , Williams James D. , Hatcher Victor , Galinovic-Schwartz Vera , Flanders Kathleen C. , Water Thomas R. Van De 
Published: April 2021

ABSTRACT
Interactions between the epithelial anlage of the developing mouse inner ear and its associated periotic mesenchyme control the differentiation of the cartilaginous otic capsule. Transforming growth factor-beta1 (TGF-β1) is a naturally occurring signal peptide that is present in these tissues at times of active differentiation and morphogenesis. Previous studies have shown that TGF-β1 alone is not a sufficient stimulus to initiate chondrogenesis in cultured periotic mesenchyme. In this study, we provide evidence that basic fibroblast growth factor (bFGF) can elicit a specific but limited chondrogenic response in cultured periotic mesenchymal cells. We also demonstrate that simultaneous addition of bFGF and TGF-β1 to cultured periotic mesenchyme results in a full chondrogenic response comparable to that which occurs when periotic mesenchyme is grown in the presence of its natural inductor tissue (i.e. otic epithelium). Utilizing antibodies directed against bFGF, we show localization of endogenous bFGF in the otic epithelium in vivo and in mixed epithelial-mesenchymal cultures. Additionally, we demonstrate the presence of FGF-like activity in medium conditioned by otic epithelium. Blocking of epithelial elicited chondrogenesis by a combination of both αbFGF and αTGF-β1 antibodies provides further evidence of the necessity for these growth factors in the chondrogenic differentiation of periotic mesenchyme in vitro. Our results suggest a role for both bFGF and TGF-β1 in the regulation of chondrogenesis during otic capsule formation in situ.
Microtubule and chromatin behavior follow MAP kinase activity but not MPF activity during meiosis in mouse oocytes
Authors: Verlhac Marie-Hélène , Kubiak Jacek Z. , Clarke Hugh J. , Maro Bernard 
Published: April 2021

ABSTRACT
Oocyte meiotic maturation is triggered by different stimuli (hormones, unknown signals through cell interactions) in different species. These stimuli indirectly lead to the activation of a major cell cycle regulating activity, the maturation promoting factor (MPF). Other factors, such as the product of the proto-oncogene c-mos or enzymes of the MAP kinase family, are also involved in the process of maturation. MAP kinase activation occurs during meiotic maturation in oocytes from different species with different kinetics. The relationships between MPF activation and MAP kinase activation have been well studied in species such as clam and Xenopus. In this paper, we study the precise timing of MAP kinase activation (as measured by phosphorylation of exogenous myelin basic protein and shifts in mobility of ERK 1 and ERK 2) versus MPF activation (as measured by phosphorylation of exogenous histone H1) during mouse oocyte maturation and, in parallel, morphological events such as changes in microtubule organization and chromatin condensation. We observed that MAP kinase activation was delayed after MPF activation and that this activity persisted throughout maturation whereas MPF activity dropped between the two meiotic metaphases. After parthenogenetic activation of ovulated eggs, MAP kinase inactivation was very slow compared to MPF inactivation. During the first mitotic cell cycle, a rise in myelin basic protein kinase activity at M-phase was observed but it was not related to MAP kinase activation. Furthermore, microtubules and chromatin remained in a metaphase-like state during the complete period of maturation (including the period between the two meiotic metaphases) and a few hours after activation. Thus, during meiosis but not during mitosis, the changes in microtubule organization and chromatin condensation correlate with MAP kinase activity rather than with MPF activity. We discuss the possible role of MAP kinase in the maintenance of a metaphasic state during meiosis when MPF is inactive.
A maternal factor affecting mouse blastocyst formation
Authors: Renard J.-P. , Baldacci P. , Richoux-Duranthon V. , Pournin S. , Babinet C. 
Published: April 2021

ABSTRACT
Normal development of the mouse embryo requires the presence of both paternal and maternal genomes. This is due to functional differences having their origin in a differential imprinting of parental genomes. Furthermore, several lines of evidence show that the very early interactions between egg cytoplasm and pronuclei may influence the programming of the embryonic genome and modulate the functional inequality of the parental contribution even during preimplantation stages. In this paper, we show that a factor present in ovulated oocytes of the mouse mutant strain DDK and therefore of maternal origin prevents the formation of the blastocyst. This factor, which acts via an interaction with the paternal genome, is present in oocytes as an RNA and is still active in preimplantation embryos. This is the first direct evidence of such a maternal control in the mouse.
Neuroectodermal transcription of the Drosophila neurogenic genes E(spl) and HLH-m5 is regulated by proneural genes
Authors: Kramatschek Bernd , Campos-Ortega José A. 
Published: April 2021

ABSTRACT
The Enhancer of split gene complex (E(SPL)-C) of Drosophila comprises seven genes encoding bHLH proteins, which are required by neuroectodermal cells for epidermal development. Using promoter and gene fusions with the lacZ gene, we determined the location of cis-acting sequences necessary for normal expression of two of the genes of the E(SPL)-C, E(spl) and HLH-m5. About 0.46 kb of E(spl) and 1.9 kb of HLH-m5 upstream sequences are necessary to reproduce the normal transcription pattern of these genes. The gene products of achaete, scute and lethal of scute, together with that of ventral nervous system condensation defective, act synergistically to specify the neuroectodermal E(spl) and HLH-m5 expression domains. Negative cross- and autoregulatory interactions of the E(SPL)-C on E(spl) contribute, directly or indirectly, to this regulation. Interactions involve DNA binding, since mutagenesis of binding sites for bHLH proteins in the E(spl) promoter abolishes neuroectodermal expression and activates ectopic expression in neuroblasts. A model for activation and repression of E(spl) in the neuroectoderm and neuroblasts, respectively, is proposed.
Cell intercalation during Drosophila germband extension and its regulation by pair-rule segmentation genes
Authors: Irvine Kenneth D. , Wieschaus Eric 
Published: April 2021

ABSTRACT
After the onset of gastrulation, the Drosophila germband undergoes a morphological change in which its length along the anterior-posterior axis increases over two-and-a-half fold while its width along the dorsal-ventral axis simultaneously narrows. The behavior of individual cells during germband extension was investigated by epi-illumination and time-lapse video microscopy of living embryos. Cells intercalate between their dorsal and ventral neighbors during extension, increasing the number of cells along the anterior-posterior axis while decreasing the number of cells along the dorsal-ventral axis. Mutations that reduce segmental subdivision of the embryo along the anteriorposterior axis decrease both germband extension and its associated cell intercalation. In contrast, cell intercalation and germband extension are still detected in embryos that lack dorsal-ventral polarity. Characterization of germband extension and cell intercalation in mutant embryos with altered segmentation gene expression indicates that these processes are regionally autonomous and are dependent upon the establishment of striped expression patterns for certain pair-rule genes. Based on these observations, we propose a model for germband extension in which cell intercalation results from the establishment of adhesive differences between stripes of cells by pair-rule genes.
The Drosophila 18 wheeler is required for morphogenesis and has striking similarities to Toll
Authors: Eldon Elizabeth , Kooyer Sandra , D’Evelyn Diana , Duman Molly , Lawinger Patrick , Botas Juan , Bellen Hugo 
Published: April 2021

ABSTRACT
We have isolated and characterized a novel gene, named 18 wheeler (18w) for its unique segmental expression pattern in Drosophila embryos and expression in cells that migrate extensively. 18 wheeler transcripts accumulate in embryos in a pattern reminiscent of segment polarity genes. Mutations in 18w cause death during larval development and early adulthood. Escaping mutant adults often display leg, antenna, and wing deformities, presumably resulting from improper eversion of imaginal discs. Sequence analysis indicates that 18w encodes a transmembrane protein with an extracellular moiety containing many leucine rich repeats and cysteine motifs, and an intracellular domain bearing homology to the cytoplasmic portion of the interleukin-1-receptor. Expression of 18W protein in non-adhesive Schneider 2 cells promotes rapid and robust aggregation of cells. Analysis of the expression of 18w in different mutant backgrounds shows that it is under control of segment polarity and homeotic genes. The data suggest that the 18W protein participates in the develop-mental program specified by segmentation and homeotic genes as a cell ahesion or receptor molecule that facilitates cell movements.
Selective disruption of E-cadherin function in early Xenopus embryos by a dominant negative mutant
Authors: Levine Elena , Lee Chung Hyun , Kintner Chris , Gumbiner Barry M. 
Published: April 2021

ABSTRACT
E-cadherin function was disrupted in vivo in developing Xenopus laevis embryos through the expression of a mutant E-cadherin protein lacking its cytoplasmic tail. This truncated form of E-cadherin was designed to act as a dominant negative mutant by competing with the extracellular interactions of wild-type endogenous E-cadherin. Expression of truncated E-cadherin in the early embryo causes lesions to develop in the ectoderm during gastrulation. In contrast, expression of a similarly truncated N-cadherin protein failed to cause the lesions. The ectodermal defect caused by the truncated E-cadherin is rescued by overexpression of wild-type E-cadherin, by co-injection of full-length E-cadherin RNA along with the RNA for the truncated form. Overexpression of full-length C-cadherin, however, is unable to compensate for the disruption of E-cadherin function and can actually cause similar ectodermal lesions when injected alone, suggesting that there is a specific requirement for E-cadherin. Therefore, E-cadherin seems to be specifically required for maintaining the integrity of the ectoderm during epiboly in the gastrulating Xenopus embryo. Differential cadherin expression reflects, therefore, the requirement for distinct adhesive properties during different morphogenetic cell behaviors.