bluuebunny/crossref_metadata_2025_split huggingface dataset:
Patterned acquisition of skin barrier function during development
Authors: Hardman Matthew J. , Sisi Paraskevi , Banbury David N. , Byrne Carolyn 
Published: April 2021

ABSTRACT
Skin barrier function is conferred by the outer layer of epidermis, the stratum corneum, and is essential for terrestrial life. Quantitative trans-epidermal water loss assays show that barrier forms late in embryogenesis, permitting the foetus to survive a terrestrial environment at birth. Using qualitative in situ assays for skin permeability, we show that barrier forms in a patterned manner late in mouse gestation. Barrier forms at specific epidermal sites, then spreads around the embryo as a moving front. The moving front of permeability change is accompanied by multiple changes in the outer, stratum corneum-precursor cells. We use the permeability assays to show that final stages of cornified envelope assembly are coordinated with initial stages of barrier formation. Hence the whole-mount permeability assays record developmental acquisition of a known, essential component of the adult barrier. We demonstrate the authenticity of the whole-mount assays after maternal glucocorticoid therapy (known to accelerate barrier formation) and in additional species including the rat where barrier formation is well characterized by TEWL assay (Aszterbaum, M., Menon, G. K., Feingold, K. R. and Williams, M. L. Pediatr. Res. 31, 308-317). The demonstration of patterned barrier formation in other species suggests patterned change as the universal mode of embryonic barrier acquisition. These results highlight the importance of patterning as a mode of epidermal maturation during development.
unc-3, a gene required for axonal guidance in Caenorhabditis elegans, encodes a member of the O/E family of transcription factors
Authors: Prasad Brinda C. , Ye Bing , Zackhary Randa , Schrader Karen , Seydoux Geraldine , Reed Randall R. 
Published: April 2021

ABSTRACT
The expression of specialized signal transduction components in mammalian olfactory neurons is thought to be regulated by the O/E (Olf-1/EBF) family of transcription factors. The O/E proteins are expressed in cells of the olfactory neuronal lineage throughout development and are also expressed transiently in neurons in the developing nervous system during embryogenesis. We have identified a C. elegans homologue of the mammalian O/E proteins, which displays greater than 80% similarity over 350 amino acids. Like its mammalian homologues, CeO/E is expressed in certain chemosensory neurons (ASI amphid neurons) throughout development and is also expressed transiently in developing motor neurons when these cells undergo axonal outgrowth. We demonstrate that CeO/E is the product of the unc-3 gene, mutations in which cause defects in the axonal outgrowth of motor neurons, as well as defects in dauer formation, a process requiring chemosensory inputs. These observations suggest that the O/E family of transcription factors play a central and evolutionarily conserved role in the expression of proteins essential for axonal pathfinding and/or neuronal differentiation in both sensory and motor neurons.
Homeotic gene action in embryonic brain development of Drosophila
Authors: Hirth Frank , Hartmann Beate , Reichert Heinrich 
Published: April 2021

ABSTRACT
Studies in vertebrates show that homeotic genes are involved in axial patterning and in specifying segmental identity of the embryonic hindbrain and spinal cord. To gain further insights into homeotic gene action during CNS development, we here characterize the role of the homeotic genes in embryonic brain development of Drosophila. We first use neuroanatomical techniques to map the entire anteroposterior order of homeotic gene expression in the Drosophila CNS, and demonstrate that this order is virtually identical in the CNS of Drosophila and mammals. We then carry out a genetic analysis of the labial gene in embryonic brain development. Our analysis shows that loss-of-function mutation and ubiquitous overexpression of labial results in ectopic expression of neighboring regulatory genes. Furthermore, this analysis demonstrates that mutational inactivation of labial results in regionalized axonal patterning defects which are due to both cell-autonomous and cell-nonautonomous effects. Thus, in the absence of labial, mutant cells are generated and positioned correctly in the brain, but these cells do not extend axons. Additionally, extending axons of neighboring wild-type neurons stop at the mutant domains or project ectopically, and defective commissural and longitudinal pathways result. Immunocytochemical analysis demonstrates that cells in the mutant domains do not express neuronal markers, indicating a complete lack of neuronal identity. An alternative glial identity is not adopted by these mutant cells. Comparable effects are seen in Deformed mutants but not in other homeotic gene mutants. Our findings demonstrate that the action of the homeotic genes labial and Deformed are required for neuronal differentiation in the developing brain of Drosophila.
A common mechanism controls the life cycle and architecture of plants
Authors: Ratcliffe Oliver J. , Amaya Iraida , Vincent Coral A. , Rothstein Steven , Carpenter Rosemary , Coen Enrico S. , Bradley Desmond J. 
Published: April 2021

ABSTRACT
The overall aerial architecture of flowering plants depends on a group of meristematic cells in the shoot apex. We demonstrate that the Arabidopsis TERMINAL FLOWER 1 gene has a unified effect on the rate of progression of the shoot apex through different developmental phases. In transgenic Arabidopsis plants which ectopically express TERMINAL FLOWER 1, both the vegetative and reproductive phases are greatly extended. As a consequence, these plants exhibit dramatic changes in their overall morphology, producing an enlarged vegetative rosette of leaves, followed by a highly branched inflorescence which eventually forms normal flowers. Activity of the floral meristem identity genes LEAFY and APETALA 1 is not directly inhibited by TERMINAL FLOWER 1, but their upregulation is markedly delayed compared to wild-type controls. These phenotypic and molecular effects complement those observed in the tfl1 mutant, where all phases are shortened. The results suggest that TERMINAL FLOWER 1 participates in a common mechanism underlying major shoot apical phase transitions, rather than there being unrelated mechanisms which regulate each specific transition during the life cycle.
CHR3: a Caenorhabditis elegans orphan nuclear hormone receptor required for proper epidermal development and molting
Authors: Kostrouchova Marta , Krause Michael , Kostrouch Zdenek , Rall Joseph Edward 
Published: April 2021

ABSTRACT
CHR3 is a Caenorhabditis elegans orphan nuclear hormone receptor highly homologous to Drosophila DHR3, an ecdysone-inducible gene product involved in metamorphosis. Related vertebrate factors include RORalpha/RZRalpha, RZRbeta and RevErb. Gel-shift studies show that CHR3 can bind the DR5-type hormone response sequence. CHR3 is a nuclear protein present in all blastomeres during early embryogenesis. During morphogenesis, both CHR3 protein and zygotically active reporter genes are detectable in epidermal cells and their precursors. Inhibition of the gene encoding CHR3 results in several larval defects associated with abnormal epidermal cell function, including molting and body size regulation, suggesting that CHR3 is an essential epidermal factor required for proper postembryonic development.
prdl-a, a gene marker for hydra apical differentiation related to triploblastic paired-like head-specific genes
Authors: Gauchat Dominique , Kreger Sylvia , Holstein Thomas , Galliot Brigitte 
Published: April 2021

ABSTRACT
Two homeobox genes, prdl-a and prdl-b, which were isolated from a Hydra vulgaris cDNA library, encode paired-like class homeodomains highly related to that of the aristaless-related genes. In adult polyps, prdl-b is a marker for synchronously dividing nematoblasts while prdl-a displays an expression restricted to the the nerve cell lineage of the head region. During budding and apical regeneration, an early and transient prdl-a expression was observed in endodermal cells of the stump at a time when the head organizer is established. When apical regeneration was delayed upon concomittant budding, prdl-a expression was found to be altered in the stump. Furthermore, a specific anti-prdl-a protein immunoserum revealed that prdl-a was overexpressed in adult polyps of the Chlorohydra viridissima multiheaded mutant, with an expression domain extending below the tentacle ring towards the body column. Accordingly, prdl-a DNA-binding activity was enhanced in nuclear extracts from this mutant. These results suggest that prdl-a responds to apical forming signals and might thus be involved in apical specification. When a marine hydrozoan (Podocorynae carnea) was used, the anti-prdl-a antibody showed cross-reactivity with cells located around the oral region, indicating that prdl-a function is shared by other cnidaria. The ancestral role for prdl-a-related genes in the molecular definition of the head (or oral-surrounding region) is discussed.
Runt determines cell fates in the Drosophila embryonic CNS
Authors: Dormand Emma-Louise , Brand Andrea H. 
Published: April 2021

ABSTRACT
The segmentation gene, runt, is expressed by a subset of the 30 neuroblasts that give rise to each neuromere of the Drosophila embryo. Runt activity in the neuroblasts is necessary for expression of even-skipped in the EL neurons. runt is therefore a good candidate for a gene specifying neuroblast identities. We have ectopically expressed Runt in restricted subsets of neuroblasts and show that Runt is sufficient to activate even-skipped expression in the progeny of specific neuroblasts. Using the marker Tau-green fluorescent protein to highlight the axons, we have found that the extra Even-skipped-expressing neurons project axons along the same pathway as the EL neurons. We find that Runt is expressed in neuroblast 3-3, supporting an autonomous role for runt during neuroblast specification.
Genetic analysis of a Hoxd-12 regulatory element reveals global versus local modes of controls in the HoxD complex
Authors: Hérault Yann , Beckers Johannes , Kondo Takashi , Fraudeau Nadine , Duboule Denis 
Published: April 2021

ABSTRACT
Vertebrate Hoxd genes are essential determinants of limb morphogenesis. In order to understand the genetic control of their complex expression patterns, we have used a combined approach involving interspecies sequence alignments in parallel with transgenic analyses, followed by in vivo mutagenesis. Here, we report on the identification of a regulatory element that is located in the vicinity of the Hoxd-12 gene. While this element is well conserved in tetrapods, little sequence similarity was scored when compared to the cognate fish DNA. The regulatory potential of this region XI (RXI) was first assayed in the context of a Hoxd-12/lacZ reporter transgene and shown to direct reporter gene expression in posterior limb buds. A deletion of this region was generated by targeted mutagenesis in ES cells and introduced into mice. Analyses of animals homozygous for the HoxDRXI mutant allele revealed the function of this region in controlling Hoxd-12 expression in the presumptive posterior zeugopod where it genetically interacts with Hoxa-11. Downregulation of Hoxd-12 expression was also detected in the trunk suggesting that RXI may mediate a rather general function in the activation of Hoxd-12. These results support a model whereby global as well as local regulatory influences are necessary to build up the complex expression patterns of Hoxd genes during limb development.
The PS2 integrin ligand tiggrin is required for proper muscle function in Drosophila
Authors: Bunch Thomas A. , Graner Michael W. , Fessler Liselotte I. , Fessler John H. , Schneider Kimberly D. , Kerschen Arthur , Choy Lynna P. , Burgess Bradford W. , Brower Danny L. 
Published: April 2021

ABSTRACT
Tiggrin is a novel extracellular matrix ligand for the Drosophila PS2 integrins. We have used flanking P elements to generate a precise deletion of tiggrin. Most flies lacking tiggrin die as larvae or pupae. A few adults do emerge and these appear to be relatively normal, displaying only misshapen abdomens and a low frequency of wing defects. Examination of larvae shows that muscle connections, function and morphology are defective in tiggrin mutants. Muscle contraction waves that extend the length of the larvae are much slower in tiggrin mutants. Direct examination of bodywall muscles shows defects in muscle attachment sites, where tiggrin is specifically localized, and muscles appear thinner. Transgenes expressing tiggrin are capable of rescuing tiggrin mutant phenotypes. Transgenes expressing a mutant tiggrin, whose Arg-Gly-Asp (RGD) integrin recognition sequence has been mutated to Leu-Gly-Ala (LGA) show much reduced, but significant, rescuing ability. Cell spreading assays detect no interactions of this mutant tiggrin with PS2 integrins. Therefore, while the RGD sequence is critical for PS2 interactions and full activity in the whole fly, the mutant tiggrin retains some function(s) that are probably mediated by interactions with other ECM molecules or cell surface receptors
Progressive lineage analysis by cell sorting and culture identiﬁes FLK1+VEcadherin+ cells at a diverging point of endothelial and hemopoietic lineages
Authors: Nishikawa Shin-Ichi , Nishikawa Satomi , Hirashima Masanori , Matsuyoshi Norihisa , Kodama Hiroaki 
Published: April 2021

ABSTRACT
Totipotent murine ES cells h ave an enormous potential for the study of cell speciﬁcation. He re we demonstrate that ES cells can diffe rentiate to hemopoietic cells th rough the proximal lateral mesoderm, me rely upon culturing in type IV collagen-coated dishes. Separation of the Flk1+ mesoderm f rom other cell lineages was critical for hemopoietic cell diffe rentiation, whe reas formation of the embryoid body was not. Since the two-dimensionally spreading cells can be monito red easily in real time, this culture system will g reatly facilitate the study of the mechanisms i nvolved in the cell speciﬁcation to mesoderm, endothelial, and hemopoietic cells. In the cultu re of ES cells, how ever, lineages and stages of diffe rentiating cells can only be deﬁned by their own characteristics. We showed that a combination of monoclonal antibodies against E-cadherin, Flk1/KDR, PDGF recepto rα, VEcadherin, CD45 and Ter119 was suf ficient to deﬁne most intermediate stages during diffe rentiation of ES cells to blood cells. Using this cultu re system and surface markers, we determined the following order for blood cell differentiation: ES cell (E-cadherin+Flk1™PDGFRα™), proximal lateral mesoderm (E-cadherin™ Flk1+VEcadherin™ ), progenitor with hemoangiogenic potential (Flk1+VE-cadherin+CD45™ ), hemopoietic p rogenitor (CD45+c-Kit+) and mature blood cells (c-Kit™ CD45+ or Ter119+), though direct differentiation of blood cells f rom the Flk1+VE-cadherin™ stage cannot be ruled out. Not only the VE-cadherin+CD45™ population generated f rom ES cells but also those di rectly sorted f rom the yolk sac of 9.5 dpc embryos h ave a potential to give rise to hemopoietic cells. P rogenitors with hemoangiogenic potential were identiﬁed in both the Flk1+VE-cadherin™and Flk1+VEcadherin+populations by the single cell deposition experiment. This line of evidence implicates Flk1+VEcadherin+ cells as a diverging point of hemopoietic and endothelial cell lineages.
Ectodermal patterning in the avian embryo: epidermis versus neural plate
Authors: Pera Edgar , Stein Stefan , Kessel Michael 
Published: April 2021

ABSTRACT
Ectodermal patterning of the chick embryo begins in the uterus and continues during gastrulation, when cells with a neural fate become restricted to the neural plate around the primitive streak, and cells fated to become the epidermis to the periphery. The prospective epidermis at early stages is characterized by the expression of the homeobox gene DLX5, which remains an epidermal marker during gastrulation and neurulation. Later, some DLX5-expressing cells become internalized into the ventral forebrain and the neural crest at the hindbrain level. We studied the mechanism of ectodermal patterning by transplantation of Hensen’s nodes and prechordal plates. The DLX5 marker indicates that not only a neural plate, but also a surrounding epidermis is induced in such operations. Similar effects can be obtained with neural plate grafts. These experiments demonstrate that the induction of a DLX5-positive epidermis is triggered by the midline, and the effect is transferred via the neural plate to the periphery. By repeated extirpations of the endoderm we suppressed the formation of an endoderm/mesoderm layer under the epiblast. This led to the generation of epidermis, and to the inhibition of neuroepithelium in the naked ectoderm. This suggests a signal necessary for neural, but inhibitory for epidermal development, normally coming from the lower layers. Finally, we demonstrate that BMP4, as well as BMP2, is capable of inducing epidermal fate by distorting the epidermis-neural plate boundary. This, however, does not happen independently within the neural plate or outside the normal DLX5 domain. In the area opaca, the co-transplantation of a BMP4 bead with a node graft leads to the induction of DLX5, thus indicating the cooperation of two factors. We conclude that ectodermal patterning is achieved by signalling both from the midline and from the periphery, within the upper but also from the lower layers.
CRABS CLAW and SPATULA, two Arabidopsis genes that control carpel development in parallel with AGAMOUS
Authors: Alvarez John , Smyth David R. 
Published: April 2021

ABSTRACT
To help understand the process of carpel morphogenesis, the roles of three carpel development genes have been partitioned genetically. Mutants of CRABS CLAW cause the gynoecium to develop into a wider but shorter structure, and the two carpels are unfused at the apex. Mutants of a second gene, SPATULA, show reduced growth of the style, stigma, and septum, and the transmitting tract is absent. Double mutants of crabs claw and spatula with homeotic mutants that develop ectopic carpels demonstrate that CRABS CLAW and SPATULA are necessary for, and inseparable from, carpel development, and that their action is negatively regulated by A and B organ identity genes. The third carpel gene studied, AGAMOUS, encodes C function that has been proposed to fully specify carpel identity. When AGAMOUS function is removed together with the A class gene APETALA2, however, the organs retain many carpelloid properties, suggesting that other genes are also involved. We show here that further mutant disruption of both CRABS CLAW and SPATULA function removes remaining carpelloid properties, revealing that the three genes together are necessary to generate the mature gynoecium. In particular, AGAMOUS is required to specify the identity of the carpel wall and to promote the stylar outgrowth at the apex, CRABS CLAW suppresses radial growth of the developing gynoecium but promotes its longitudinal growth, and SPATULA supports development of the carpel margins and tissues derived from them. The three genes mostly act independently, although there is genetic evidence that CRABS CLAW enhances AGAMOUS and SPATULA function.
CRABS CLAW, a gene that regulates carpel and nectary development in Arabidopsis, encodes a novel protein with zinc finger and helix-loop-helix domains
Authors: Bowman John L. , Smyth David R. 
Published: April 2021

ABSTRACT
Studies of plants with mutations in the CRABS CLAW gene indicate that it is involved in suppressing early radial growth of the gynoecium and in promoting its later elongation. It is also required for the initiation of nectary development. To gain further insight, the gene was cloned by chromosome walking. CRABS CLAW encodes a putative transcription factor containing a zinc finger and a helix-loop-helix domain. The latter resembles the first two helices of the HMG box, known to bind DNA. At least five other genes of Arabidopsis carry the same combination of domains, and we have named them the yabby family. The new helix-loop-helix domain itself we call the yabby domain. Consistent with the mutant phenotype, CRABS CLAW expression is mostly limited to carpels and nectaries. It is expressed in gynoecial primordia from their inception, firstly in lateral sectors where it may inhibit radial growth, and later in the epidermis and in four internal strips. The internal expression may be sufficient to support longitudinal growth, as carpels are longer in a crabs claw promoter mutant where expression is now confined to these regions. The patterns of expression of CRABS CLAW in ectopic carpels of floral homeotic mutants suggest that it is negatively regulated by the A and B organ identity functions, but largely independent of C function. CRABS CLAW expression occurs in nectaries throughout their growth and maturation. It is also expressed in their presumptive anlagen so it may specify cells that will later develop as nectaries. Nectaries arise from the floral receptacle at normal positions in all A, B and C organ identity mutants examined, and CRABS CLAW is always expressed within them. Thus CRABS CLAW expression is regulated independently in carpels and nectaries.
Reconstitution of the organizer is both sufficient and required to re-establish a fully patterned body plan in avian embryos
Authors: Yuan Shipeng , Schoenwolf Gary C. 
Published: April 2021

ABSTRACT
Lateral blastoderm isolates (LBIs) at the late gastrula/early neurula stage (i.e., stage 3d/4) that lack Hensen’s node (organizer) and primitive streak can reconstitute a functional organizer and primitive streak within 10-12 hours in culture. We used LBIs to study the initiation and regionalization of the body plan. A complete body plan forms in each LBI by 36 hours in culture, and normal craniocaudal, dorsoventral, and mediolateral axes are re-established. Thus, reconstitution of the organizer is sufficient to re-establish a fully patterned body plan. LBIs can be modified so that reconstitution of the organizer does not occur. In such modified LBIs, tissue-type specific differentiation (with the exception of heart differentiation) and reconstitution of the body plan fail to occur. Thus, the reconstitution of the organizer is not only sufficient to re-establish a fully patterned body plan, it is also required. Finally, our results show that formation and patterning of the heart is under the control of the organizer, and that such control is exerted during the early to mid-gastrula stages (i.e., stages 2-3a), prior to formation of the fully elongated primitive streak.