bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clonal analysis of the late flowering fca mutant of Arabidopsis thaliana: cell fate and cell autonomy
Authors: Furner I. J. , Ainscough J. F-X. , Pumfrey J. A. , Petty L. M. 
Published: April 2021

ABSTRACT
Plants that are homozygous for the fca mutation bolt and flower later than wild-type (FCA) plants. The mutation has little or no effect on the fate map of the dry seed, except that the central cells give rise to further rosette leaves instead of the bolting stem, cauline leaves and inflorescence. The large and variable sectors affecting the late rosette leaves of fca plants were used to generate an abstract frequency-distance fate map of vegetative growth. The map relates the initiation of leaves in the plant apex to their final arrangements. The map was found to be a shallow dome with phyllotaxy superimposed on its surface.
X-irradiation was used to provoke loss of the FCA allele from cells in heterozygous seeds. The resulting fca sectors had no effect on the plant phenotype. Even when L2 and L3 cells at the centre of the meristem could not produce the FCA gene product, bolting and flowering was unaffected. The genotypically fca mutant tissue was incorporated into phenotypically normal stems, cauline leaves and flowers. Possible reasons for the non-autonomous behaviour of the trait are discussed.
A test for cell autonomy, based on di-cistronic messenger translation
Authors: Hart Karen , Bienz Mariann 
Published: April 2021

ABSTRACT
We have devised a test for cell autonomy of a gene that is switched on ectopically in a clone of cells, allowing us to ask whether the wild-type activity of this gene can influence neighbouring cells. To switch on the test gene, we used the yeast FRT system, and marked the FRT-generated cell clone by co-expressing β-galactosidase. Co-expression is achieved by a stretch of 5′ untranslated mRNA from the homeotic gene Ultrabithorax (Ubx), which is inserted between the two coding sequences. We show that this Ubx sequence mediates efficient and reliable di-cistronic Mrna translation in wing imaginal discs of Drosophila. Applying our test to Ubx, we find that ectopic Ubx in wing discs strictly coincides with β-galactosidase expression. Consequently, wing cells are transformed into cells that appear to be intermediates between wing and haltere cells, contesting the view that homeotic genes act as binary switches.
hedgehog is required for the proliferation and specification of ovarian somatic cells prior to egg chamber formation in Drosophila
Authors: Forbes Alexandria J. , Lin Haifan , Ingham Philip W. , Spradling Allan C. 
Published: April 2021

ABSTRACT
The hedgehog (hh) gene plays a role in regulating cell proliferation and specifying cell identity in diverse systems. We show that hh is expressed at the extreme apical end of Drosophila ovarioles in terminal filament cells and a newly identified group of associated somatic cells. Reducing or ectopically expressing hh affects somatic cells in region 2 of the germarium, 2-5 cells away from the cells in which Hh protein is detected. hh activity stimulates the proliferation of pre-follicle somatic cells, and promotes the specification of polar follicle cells. hh signalling during egg chamber assembly appears to be closely related to, or part of pathways involving the neurogenic genes.
Expression and regulation of Cek-8, a cell to cell signalling receptor in developing chick limb buds
Authors: Patel K. , Nittenberg R. , D’Souza D. , Irving C. , Burt D. , Wilkinson D. G. , Tickle C. 
Published: April 2021

ABSTRACT
The Eph-related receptor tyrosine kinase gene, Cek-8, is expressed in mesenchyme at the tip of chick limb buds, with high levels of transcripts posteriorly and apically but fading out anteriorly. Expression of Cek-8 in distal mesenchyme is regulated by apical ridge- and FGF-polarising signals and retinoic acid, and is uniform across the antero- posterior axis in talpid3 mutants. These data indicate that Cek-8 expression responds to regulatory signals during limb patterning and suggest that this receptor tyrosine kinase may have a role in coordinating responses to signals in the progress zone of early buds. Later on in limb development, Cek-8 expression is associated with cell condensations that form tendons and their attachments to cartilage rudiments and then in developing feather buds.
A mutational analysis of the 5′ HoxD genes: dissection of genetic interactions during limb development in the mouse
Authors: Capecchi Allan Peter Davis and Mario R. 
Published: April 2021

ABSTRACT
Using gene targeting in mice, we have undertaken a systematic mutational analysis of the homeobox-containing 5′ HoxD genes. In particular, we have characterized the limb defects observed in mice with independent targeted disruptions of hoxd-12 and hoxd-13. Animals defective for hoxd-12 are viable, fertile, and appear outwardly normal yet have minor autopodal defects in the forelimb which include a reduction in the bone length of metacarpals and phalanges, and a malformation of the distal carpal bone d4. The limb phenotypes observed in hoxd-13 mutant mice are more extensive, including strong reductions in length, complete absences, or improper segmentations of many metacarpal and phalangeal bones. Additionally, the d4 carpal bone is not properly formed and often produces an extra rudimentary digit. To examine the genetic interactions between the 5′ HoxD genes, we bred these mutant strains with each other and with our previously characterized hoxd-11 mouse to produce a series of trans-heterozygotes. Skeletal analyses of these mice reveal that these genes interact in the formation of the vertebrate limb, since the trans-heterozygotes display phenotypes not present in the individual heterozygotes, including more severe carpal, metacarpal and phalangeal defects. Some of these pheno- types appear to be accounted for by a delay in the ossification events in the autopod, which lead to either the failure of fusion or the elimination of cartilaginous elements. Characteristically, these mutations lead to the overall trun- cation of digits II and V on the forelimb. Additionally, some trans-animals show the growth of an extra postaxial digit VI, which is composed of a bony element resembling a phalange. The results demonstrate that these genes interact in the formation of the limb. In addition to the previously characterized paralogous interactions, a multitude of inter- actions between Hox genes is used to finely sculpt the forelimb. The 5′ Hox genes could therefore act as a major permissive genetic milieu that has been exploited by evolutionary adaptation to form the tetrapod limbs.
Specification of the anteroposterior axis in Caenorhabditis elegans
Authors: Goldstein Bob , Hird Steven N. 
Published: April 2021

ABSTRACT
Anteroposterior asymmetries are apparent in C. elegans development before the first cell division. Here we identify the cue that specifies the anteroposterior axis, and investigate how this cue is interpreted to generate initial asymmetry. In C. elegans, the sperm normally enters the egg in an invariant position. We have found that causing fertilisation to occur in the abnormal end of the egg completely reverses the orientation of the anteroposterior axis, but gives otherwise normal development. This result suggests that a component of the sperm normally specifies the anteroposterior axis. We have found that a cytoplasmic rearrangement in the uncleaved zygote is directed by the sperm, suggesting a mechanism by which the sperm may specify the axis. The results additionally reveal that the C. elegans oocyte is constructed with no axis prespecified in the form of asymmetrically localised cytoplasmic determinants.
Functional domains in the Deformed protein
Authors: Zhu Aihua , Kuziora Michael A. 
Published: April 2021

ABSTRACT
A chimeric protein consisting of Deformed with a substituted Abdominal-B homeodomain (Dfd/Abd-B) is used to identify protein domains outside the homeodomain that are required for regulatory activity in vivo. A series of deletion proteins were generated based on regions showing amino acid composition similar to known regulatory domains. Each mutant protein can influence regulation of homeotic genes in a manner distinct from the intact protein. Activity was also tested using promoter elements from empty spiracles and Distal-less, two genes known to be directly regulated by Abdominal-B. Removal of the acidic region and the C-tail region convert the chimera from a strong activator to a repressor of the Distal-less element, but had comparatively little effect on the activation of the empty spiracles element. Constructs without a third domain, the N domain, fail to show any regulatory activity. The N domain is the only domain of the Dfd/Abd-B protein which exhibits significant activation activity when fused to a heterologous DNA binding domain. Our results suggest transcriptional activity of the N domain can be modulated by the acidic and C-tail domains.
Surface tensions of embryonic tissues predict their mutual envelopment behavior
Authors: Foty Ramsey A. , Pfleger Cathie M. , Forgacs Gabor , Steinberg Malcolm S. 
Published: April 2021

ABSTRACT
During embryonic development, certain tissues stream to their destinations by liquidlike spreading movements. According to the ‘differential adhesion hypothesis’, these movements are guided by cell-adhesion-generated tissue surface tensions (σs), operating in the same manner as surface tensions do in the mutual spreading behavior of immiscible liquids, among which the liquid of lower surface tension is always the one that spreads over its partner. In order to conduct a direct physical test of the ‘differential adhesion hypothesis’, we have measured the σ s of aggregates of five chick embryonic tissues, using a parallel plate compression apparatus specifically designed for this purpose, and compared the measured values with these tissues’ mutual spreading behaviors. We show that aggregates of each of these tissues behave for a time as elasticoviscous liquids with characteristic surface tension values. Chick embryonic limb bud mesoderm (σ = 20.1 dyne/cm) is enveloped by pigmented epithelium (σ = 12.6 dyne/cm) which, in turn, is enveloped by heart (σ = 8.5 dyne/cm) which, in turn, is enveloped by liver (σ = 4.6 dyne/cm) which, in turn, is enveloped by neural retina (σ = 1.6 dyne/cm). Thus, as predicted, the tissues’ surface tension values fall in the precise sequence required to account for their mutual envelopment behavior.
The Drosophila Polycomb group gene Sex comb on midleg (Scm) encodes a zinc finger protein with similarity to polyhomeotic protein
Authors: Bornemann Douglas , Miller Ellen , Simon Jeffrey 
Published: April 2021

ABSTRACT
The Sex comb on midleg (Scm) gene is a member of the Polycomb group (PcG) of genes in Drosophila melanogaster. The PcG genes encode transcriptional repressors required for proper spatial expression of homeotic genes. We report the isolation of new Scm mutations and the molecular char- acterization of the Scm gene. Scm mRNA is expressed maternally, at peak levels in early embryos and then at lower levels throughout the remainder of development. Scm encodes a putative zinc finger protein of 877 amino acids. Scm protein is similar to polyhomeotic, another member of the PcG, both in the zinc finger region and in a separate C-terminal domain of 60 amino acids, which we term the SPM domain. Sequence analysis of an Scm mutant allele suggests a functional requirement for the SPM domain. Scm protein also bears homology in multiple domains to a mouse protein, Rae-28 (Nomura, M., Takihara, Y. and Shimada, K. (1994) Differentiation 57, 39-50) and to a fly tumor suppressor protein, the product of the lethal(3)malignant brain tumor gene (Wismar, J. et al., (1995) Mech. Dev. 53, 141-154). Possible functional rela- tionships among these proteins and potential biochemical roles for Scm protein in PcG repression are discussed.
Evidence from normal expression and targeted misexpression that Bone Morphogenetic Protein-4 (Bmp-4) plays a role in mouse embryonic lung morphogenesis
Authors: Bellusci Savério , Henderson Randall , Winnier Glenn , Oikawa Tsuyoshi , Hogan Brigid L. M. 
Published: April 2021

ABSTRACT
Epithelial-mesenchymal interactions are critical for the branching and differentiation of the lung, but the mechanisms involved are still unclear. To investigate this problem in mouse embryonic lung, we have studied the temporal and spatial expression of genes implicated in the morpho-genesis of other organs. At 11.5 days p.c., hepatocyte nuclear factor-3β (Hnf-3β) is expressed uniformly through-out the epithelium, while Wnt-2 expression is confined to the distal mesenchyme. Sonic hedgehog (Shh) trancripts are found throughout the epithelium, with high levels in the distal tips of the terminal buds, while bone morphogenetic protein-4 (Bmp-4) transcripts are localized at high levels in the distal tips of the epithelium, with lower levels in the adjacent mesenchyme. Epithelial expression is also seen for Bmp-7, but transcripts are less dramatically upregulated at the distal tips. The Type I Bone morphogenetic protein receptor gene(Bmpr/Tfr-11/Brk-1) is expressed at low levels in the epithelium and in the distal mesenchyme. To investigate the role of Bmp-4 in lung development, we have mis-expressed the gene throughout the distal epithelium of transgenic lungs using a surfactant protein C enhancer/promoter. From 15.5 days p.c., transgenic lungs are smaller than normal, with grossly distended terminal buds and, at birth, contain large air-filled sacs which do not support normal lung function. Labeling with BrdU reveals an inhibition of epithelial proliferation in 15.5 days p.c. transgenic lungs. A small but significant stimulation of proliferation of mesenchymal cells is also observed, but this is accompanied by an increase in cell death. In situ hybridization with riboprobes for the proximal airway marker, CC10, and the distal airway marker, SP-C, shows normal differentiation of bronchiolar Clara cells but a reduction in the number of differentiated Type II cells in transgenic lungs. A model is proposed for the role of BMP4 and other signalling molecules in embryonic lung morphogenesis.
Involvement of FGF-8 in initiation, outgrowth and patterning of the vertebrate limb
Authors: Vogel Astrid , Rodriguez Concepción , Izpisúa-Belmonte Juan-Carlos 
Published: April 2021

ABSTRACT
Fibroblast Growth Factors (FGFs) are signaling molecules that are important in patterning and growth control during vertebrate limb development. Beads soaked in FGF-1, FGF-2 and FGF-4 are able to induce additional limbs when applied to the flank of young chick embryos (Cohn, M.J., Izpisua-Belmonte, J-C., Abud, H., Heath, J. K., Tickle, C. (1995) Cell 80, 739-746). However, biochemical and expression studies suggest that none of these FGFs is the endogenous signal that initiates limb development. During chick limb development, Fgf-8 transcripts are detected in the intermediate mesoderm and subsequently in the prelimb field ectoderm prior to the formation of the apical ectodermal ridge, structures required for limb initiation and outgrowth, respectively. Later on, Fgf-8 expression is restricted to the ridge cells and expression disappears when the ridge regresses. Application of FGF-8 protein to the flank induces the development of additional limbs. Moreover, we show that FGF-8 can replace the apical ectodermal ridge to maintain Shh expression and outgrowth and patterning of the developing chick limb. Furthermore, continuous and widespread misexpression of FGF-8 causes limb truncations and skeletal alterations with phocomelic or achondroplasia phenotype. Thus, FGF-8 appears to be a key signal involved in initiation, outgrowth and patterning of the developing vertebrate limb.
Clustered arrangement of winged helix genes fkh-6 and MFH-1: possible implications for mesoderm development
Authors: Kaestner Klaus H. , Bleckmann Susanne C. , Monaghan A. Paula , Schlöndorff Johannes , Mincheva Antoaneta , Lichter Peter , Schütz Günther 
Published: April 2021

ABSTRACT
The ‘winged helix’ or ‘forkhead’ transcription factor gene family is defined by a common 100 amino acid DNA binding domain which is a variant of the helix-turn-helix motif. Here we describe the structure and expression of the mouse fkh-6 and MFH-1 genes. Both genes are expressed in embryonic mesoderm from the headfold stage onward. Transcripts for both genes are localised mainly to mesenchymal tissues, fkh-6 mRNA is enriched in the mesenchyme of the gut, lung, tongue and head, whereas MFH-1 is expressed in somitic mesoderm, in the endocardium and blood vessels as well as the condensing mesenchyme of the bones and kidney and in head mesenchyme. Both genes are located within a 10 kb region on mouse chromosome 8 at 5.26±2.56 cM telomeric to Actsk1. The close physical linkage of these two winged helix genes is conserved in man, where the two genes map to chromosome 16q22-24. This tandem arrangement suggests the common use of regulatory mechanisms. The fkh-6/MFH-1 locus maps close to the mouse mutation amputated, which is characterised by abnormal development of somitic and facial mesoderm. Based on the expression patterns we suggest that a mutation in MFH-1, not fkh-6 is the possible cause for the amputated phenotype.
Activation of Fgf-4 and HoxD gene expression by BMP-2 expressing cells in the developing chick limb
Authors: Duprez Delphine M. , Kostakopoulou Konstadina , Francis-West Philippa H. , Tickle Cheryll , Brickell Paul M. 
Published: April 2021

ABSTRACT
Bone morphogenetic protein-2 (BMP-2) has been implicated in the polarizing region signalling pathway, which specifies pattern across the antero-posterior of the developing vertebrate limb. Retinoic acid and Sonic Hedgehog (SHH) can act as polarizing signals; when applied anteriorly in the limb bud, they induce mirror-image digit duplications and ectopic Bmp-2 expression in anterior mesenchyme. In addition, the two signals can activate Fgf-4 expression in anterior ridge and HoxD expression in anterior mesenchyme. We tested the role of BMP-2 in this signalling cascade by ectopically expressing human BMP-2 (hBMP-2) at the anterior margin of the early wing bud using a replication defective retroviral vector, and found that ectopic expression of Fgf-4 was induced in the anterior part of the apical ectodermal ridge, followed later by ectopic expression of Hoxd-11 and Hoxd-13 in anterior mesenchyme. This suggests that BMP-2 is involved in regulating Fgf-4 and HoxD gene expression in the normal limb bud. Ectopically expressed hBMP-2 also induced duplication of digit 2 and bifurcation of digit 3, but could not produce the mirror-image digit duplications obtained with SHH-expressing cells. These results suggest that BMP-2 may be involved primarily in maintenance of the ridge, and in the link between patterning and outgrowth of the limb bud.
Alternatively spliced forms of the Drosophila αPS2 subunit of integrin are sufficient for viability and can replace the function of the αPS1 subunit of integrin in the retina
Authors: Roote Carol E. , Zusman Susan 
Published: April 2021

ABSTRACT
The Drosophila inflated (if) gene encodes the αPS2 subunit of the PS family of integrins. The if transcript is spliced such that αPS2 is found in two alternative forms, αPS2(C) and αPS2(m8), which differ by 25 amino acid residues in a region shown to affect cation requirements and ligand specificity. In this study, we examine the functional significance of the protein isoforms of if by analyzing the ability of transgenes producing only one isoform to rescue developmental abnormalities associated with complete loss of PS2 integrin. We find that either form of αPS2 is sufficient to rescue if− animals to viability; however, the αPS2(C) form promotes higher survival of the organism. Furthermore, these studies suggest distinct roles for αPS2(C) and αPS2(m8) during development. When expressed in the developing wing, αPS2(m8) is more efficient at rescuing the if− wing blister phenotype than is αPS2(C). Expression of αPS2(C) in the eye produces dominant disruption of photoreceptor organization.
We have also examined the ability of αPS2 and αPS1 to maintain photoreceptor organization in the Drosophila retina. Clonal analysis of sectioned eyes suggests a requirement for αPS1, but not αPS2. However, ectopic expression of if(m8) or if(C) shows that either splice form of αPS2 can functionally replace αPS1 and rescue the mew eye phenotype.
Basic fibroblast growth factor induces notochord formation and the expression of As-T, a Brachyury homolog, during ascidian embryogenesis
Authors: Nakatani Yuki , Yasuo Hitoyoshi , Satoh Noriyuki , Nishida Hiroki 
Published: April 2021

ABSTRACT
The tadpole larva of an ascidian develops 40 notochord cells in the center of its tail. Most of the notochord cells originate from the A-line precursors, among which inductive interactions are required for the subsequent differentiation of notochord. The presumptive-endoderm blastomeres or presumptive-notochord blastomeres themselves are inducers of notochord formation. Notochord induction takes place during the 32-cell stage. In amphibia, mesoderm induction is thought to be mediated by several growth factors, for example, activins and basic fibroblast growth factor (bFGF). In the ascidian, Halocynthia roretzi, treatment with bFGF of presumptive-notochord blastomeres that had been isolated at the early 32-cell stage promoted the formation of notochord at a low concentration of bFGF (0.02 ng/ml), while activin failed to induce notochord differentiation. The effect of bFGF reached a maximum at the end of the 32-cell stage and rapidly faded at the beginning of the subsequent cleavage, the time for full induction of notochord being at least 20 minutes.
The expression of As-T, a previously isolated ascidian homolog of the mouse Brachyury (T) gene, starts at the 64cell stage and is detectable exclusively in the presumptivenotochord blastomeres. The present study showed that presumptive-notochord blastomeres, isolated at the early 32-cell stage, neither differentiated into notochord nor expressed the As-T gene. However, when the presumptivenotochord blastomeres were coisolated or recombined with inducer blastomeres, transcripts of As-T were detected. When presumptive-notochord blastomeres were treated with bFGF, the expression of the As-T gene was also detected. These results suggest that inductive interaction is required for the expression of the As-T gene and that the expression of the As-T gene is closely correlated with the determined state of the notochord-precursor cells.