bluuebunny/crossref_metadata_2025_split huggingface dataset:
The early blastocyst is bilaterally symmetrical and its axis of symmetry is aligned with the animal-vegetal axis of the zygote in the mouse
Authors: Gardner R. L. 
Published: April 2021

ABSTRACT
At least one polar body, almost invariably the second, persists intact to the early blastocyst stage in nearly two-thirds of mouse conceptuses of the PO strain. The distribution in early blastocysts of these surviving polar bodies was highly non-random. Most not only lay in the midregion of the embryonic-abembryonic axis but, on discovering that early blastocysts are bilaterally rather than radially symmetrical about this axis, were found to align with the bilateral axis. Cell marking experiments failed to detect movement of polar bodies relative to the surface of the conceptus during either cleavage or blastulation. That the distribution of degenerating polar bodies and their presumed debris was similar to intact ones also argued against their motility, as did the finding that at all stages second polar bodies were attached to conceptuses by a thin, extensible, weakly elastic ‘tether’. Although the transfer of small fluorochromes between them was rarely observed beyond second cleavage, the second polar body and conceptus could remain coupled ionically up to the blastocyst stage. It is concluded that the second polar body normally remains attached to the conceptus through persistence of the intercellular bridge formed during its abstriction, and therefore provides an enduring marker of the animal pole of the zygote. Hence, according to the distribution of polar bodies, the axis of bilateral symmetry of the early blastocysts is normally aligned with the animalvegetal axis of the zygote and its embryonic-abembryonic axis is orthogonal to it. Such relationships suggest that, at least in undisturbed development, specification of the axes of the blastocyst depends on spatial patterning of the zygote.
The Drosophila TGFα homolog Spitz acts in photoreceptor recruitment in the developing retina
Authors: Tio Murni , Moses Kevin 
Published: April 2021

ABSTRACT
In vertebrates and Drosophila, the Epidermal Growth Factor Receptor (EGFR) signal transduction pathway is important in the regulation of cellular development. EGFR is bound by several activating ligands including Trans-forming Growth Factor-α in vertebrates, and its homolog Spitz in Drosophila. It has been shown that Spitz and EGFR act in the development of the Drosophila central nervous system and compound eye. Here we show that spitz function is required in developing ommatidia for the first cell recruitment step, and that Spitz pro-protein is expressed in the retinal neurons as they begin to differentiate. We propose a ‘two-key’ model for additive signal transduction from EGFR and other receptor tyrosine kinases, via the Ras pathway, in the developing eye.
Two novel chick T-box genes related to mouse Brachyury are expressed in different, non-overlapping mesodermal domains during gastrulation
Authors: Knezevic Vladimir , De Santo Ronald , Mackem Susan 
Published: April 2021

ABSTRACT
The mouse Brachyury (T) gene plays critical roles in the genesis of normal mesoderm during gastrulation and in the maintenance of a functioning notochord. Abrogation of Brachyury (T) expression within the chordamesoderm of homozygous null mutants nevertheless spares anterior axis formation. An intriguing possibility to explain the preservation of anterior axis formation in these mutants would be the existence of other genes compensating for the loss of Brachyury. This compensation and the recent demonstration that Brachyury is the prototype for an evolutionarily conserved family, prompted a search for other T-box genes participating in axis formation. The chick Brachyury orthologue and two related chick T-box genes that are expressed at the onset of gastrulation have been isolated. One of these novel genes (Ch-TbxT) becomes restricted to the axial mesoderm lineage and is a potential candidate for complementing or extending Brachyury function in the anterior axis (formation of the head process, prechordal plate). The other gene (Ch-Tbx6L), together with chick T, appears to mark primitive streak progenitors before gastrulation. As cells leave the primitive streak, Ch-Tbx6L becomes restricted to the early paraxial mesoderm lineage and could play a role in regulating somitogenesis.
Spindlin, a major maternal transcript expressed in the mouse during the transition from oocyte to embryo
Authors: Oh Bermseok , Hwang Sue-Yun , Solter Davor , Knowles Barbara B. 
Published: April 2021

ABSTRACT
Timely translation of maternal transcripts and post-translational modification of their gene products control the initial development of preimplantation-stage embryos. We have isolated and characterized a gene encoding a stage-specific embryonic protein. This novel gene, spindlin (Spin), is an abundant maternal transcript present in the unfertilized egg and 2-cell, but not 8-cell, stage embryo. Spin exhibits high homology to a multicopy gene, Y-linked spermiogenesis-specific transcript (Ssty), and together they form a new gene family expressed during gametogenesis. We find that spindlin associates with the meiotic spindle and is modified by phosphorylation in a cell-cycle-dependent fashion. Furthermore, it comigrates with the previously described 30×103Mr metaphase complex which is post-translationally modified during the first mitotic cell cycle. Our data suggest that spindlin plays a role in cell-cycle regulation during the transition from gamete to embryo.
Pax3 is required for cardiac neural crest migration in the mouse: evidence from the splotch (Sp
2H) mutant
Authors: Conway Simon J. , Henderson Deborah J. , Copp Andrew J. 
Published: April 2021

ABSTRACT
Neural crest cells originating in the occipital region of the avian embryo are known to play a vital role in formation of the septum of the cardiac outflow tract and to contribute cells to the aortic arches, thymus, thyroid and parathyroids. This ‘cardiac’ neural crest sub-population is assumed to exist in mammals, but without direct evidence. In this paper we demonstrate, using RT-PCR and in situ hybridisation, that Pax3 expression can serve as a marker of cardiac neural crest cells in the mouse embryo. Cells of this lineage were traced from the occipital neural tube, via branchial arches 3, 4 and 6, into the aortic sac and aortopulmonary outflow tract. Confirmation that these Pax3-positive cells are indeed cardiac neural crest is provided by experiments in which hearts were deprived of a source of colonising neural crest, by organ culture in vitro, with consequent lack of up-regulation of Pax3. Occipital neural crest cell outgrowths in vitro were also shown to express Pax3. Mutation of Pax3, as occurs in the splotch (Sp2H) mouse, results in development of conotruncal heart defects including persistent truncus arteriosus. Homozygotes also exhibit defects of the aortic arches, thymus, thyroid and parathyroids. Pax3-positive neural crest cells were found to emigrate from the occipital neural tube of Sp2H/Sp2H embryos in a relatively normal fashion, but there was a marked deficiency or absence of neural crest cells traversing branchial arches 3, 4 and 6, and entering the cardiac outflow tract. This decreased expression of Pax3 in Sp2H/Sp2H embryos was not due to down-regulation of Pax3 in neural crest cells, as use of independent neural crest markers, Hoxa-3, CrabpI, Prx1, Prx2 and c-met also revealed a deficiency of migrating cardiac neural crest cells in homozygous embryos. This work demonstrates the essential role of the cardiac neural crest in formation of the heart and great vessels in the mouse and, furthermore, shows that Pax3 function is required for the cardiac neural crest to complete its migration to the developing heart.
Retinoid receptors promote primary neurogenesis in Xenopus
Authors: Sharpe C. R. , Goldstone K. 
Published: April 2021

ABSTRACT
Retinoid receptors, which are members of the nuclear hormone receptor superfamily, act as ligand-dependent transcription factors. They mediate the effects of retinoic acid primarily as heterodimers of retinoic acid receptors (RARs) and retinoid X receptors (RXRs). To analyse their function, xRXR β synthetic mRNA was injected into Xenopus embryos in combination with normal and mutated xRAR α transcripts. Two informative phenotypes are reported here. Firstly, over-expression of xRXR β with xRAR α results in the formation of ectopic primary neurons. Secondly, blocking retinoid signalling with a mutated xRAR α results in a lack of primary neurons. These two phenotypes, from contra-acting manipulations, indicate a role for retinoid signalling during neurogenesis.
Wnt-11 is expressed in early avian mesoderm and required for the differentiation of the quail mesoderm cell line QCE-6
Authors: Eisenberg Carol A. , Gourdie Robert G. , Eisenberg Leonard M. 
Published: April 2021

ABSTRACT
The beginning of mesodermal development involves the aggregation of newly gastrulated cells into epithelial fields, as a prelude to organ formation. To analyze the molecular regulation of this initial patterning, we have focused on the Wnt family of secreted signaling proteins, molecules which have been shown to promote embryonic patterning by regulating cell-cell associations. In this study, we show that the Wnt-11 gene is expressed by newly gastrulated mesoderm cells within avian embryos. The expression pattern of Wnt-11 also suggests that it may be involved in formation of the cardiogenic fields and somites. Subsequently, we utilized the quail mesoderm cell line QCE-6 as a culture model for examining the influence of Wnt-11 on early mesoderm cell differentiation. This cell line has been shown to be representative of early nondifferentiated mesoderm cells and has the potential to differentiate into cardiomyocytes, endohelial or red blood cells. Similar to early mesoderm cells, QCE-6 cells express Wnt-11. We have engineered stable transfectants of these cells that produce either diminished or enhanced levels of Wnt-11 protein. Our studies show that Wnt-11 regulates cellular interactions of QCE-6 cells, as demonstrated by alterations in contact-inhibited growth, tight and gap junction formation and plakoglobin expression. Both the morphology and growth factor-induced differentiation of QCE-6 cells are regulated in a cooperative fashion by Wnt-11 and fibronectin. These results, described in detail below, demonstrate the uniqueness of QCE-6 cells as a culture system for analyzing Wnt activity. In particular, QCE-6 cells are the first cell line that has demonstrated: (1) Wnt-dependent differentiation; (2) concentration-variable responses to Wnt protein; and (3) altered cell phenotypes as a direct response to Wnt-5a class proteins (e.g. Wnt-4 and Wnt-11).
Expression of the Ly-6E.1 (Sca-1) transgene in adult hematopoietic stem cells and the developing mouse embryo
Authors: Miles Colin , Sanchez Maria-Jose , Sinclair Angus , Dzierzak Elaine 
Published: April 2021

ABSTRACT
The mouse hematopoietic marker Sca-1, encoded by the Ly-6E.1 and Ly-6A.2 genes, has been instrumental in the enrichment and characterization of the stem cell for the adult blood system. In the studies reported here, we use Ly-6E.1 genomic fragments to direct expression of a lacZ marker transgene in vivo to study Ly-6E.1 specific regulatory elements in the hematopoietic stem cell and to localize these cells in the developing mouse embryo. We demonstrate that a region approximately 9 kb downstream from the transcriptional start site is required for the distinct, restricted expression pattern of the Ly-6E.1-lacZ transgene within adult hematopoietic stem cells and embryos. We also demonstrate that viable and functional lacZ-expressing hematopoietic stem cells can be enriched by FDG staining and flow cytometric sorting. The Ly-6E.1-lacZ-mediated enrichment of hematopoietic stem cells from adult transgenic bone marrow in combination with the temporal expression pattern of the transgene in the pro/mesonephros suggest an intraembryonic site of development for these cells in the mouse.
The Caenorhabditis elegans NK-2 homeobox gene ceh-22 activates pharyngeal muscle gene expression in combination with pha-1 and is required for normal pharyngeal development
Authors: Okkema Peter G. , Ha Eunju , Haun Christina , Chen Wei , Fire Andrew 
Published: April 2021

ABSTRACT
Pharyngeal muscle development in the nematode Caenorhabditis elegans appears to share similarities with cardiac muscle development in other species. We have previously described CEH-22, an NK-2 class homeodomain transcription factor similar to Drosophila tinman and vertebrate Nkx2-5, which is expressed exclusively in the pharyngeal muscles. In vitro, CEH-22 binds the enhancer from myo-2, a pharyngeal muscle-specific myosin heavy chain gene. In this paper, we examine the role CEH-22 plays in pharyngeal muscle development and gene activation by (a) ectopically expressing ceh-22 in transgenic C. elegans and (b) examining the phenotype of a ceh-22 loss-of-function mutant. These experiments indicate that CEH-22 is an activator of myo-2 expression and that it is required for normal pharyngeal muscle development. However, ceh-22 is necessary for neither formation of the pharyngeal muscles, nor for myo-2 expression. Our data suggest parallel and potentially compensating pathways contribute to pharyngeal muscle differentiation. We also examine the relationship between ceh-22 and the pharyngeal organ-specific differentiation gene pha-1. Mutations in ceh-22 and pha-1 have strongly synergistic effects on pharyngeal muscle gene expression; in addition, a pha-1 mutation enhances the lethal phenotype caused by a mutation in ceh-22. Wild-type pha-1 is not required for the onset of ceh-22 expression but it appears necessary for maintained expression of ceh-22.
Hyaluronan is a prerequisite for ductal branching morphogenesis
Authors: Gakunga Peter , Frost Gregory , Shuster Svetlana , Cunha Gerald , Formby Bent , Stern Robert 
Published: April 2021

ABSTRACT
Hyaluronan, a macromolecular carbohydrate polymer of the extracellular matrix is prominent early in embryogenesis, coinciding with rapid tissue growth. CD44, the pre-dominant receptor for hyaluronan on vertebrate cells, is a variably expressed transmembrane glycoprotein. Mouse anterior prostate glands obtained at various postnatal time points were examined for the expression of hyaluronan and CD44. Reverse transcriptase polymerase chain reaction analysis was used to map the temporal regulation of specific CD44 variant isoforms. In each age group, hyaluronan was localized exclusively in the stromal matrix. Hyaluronan was greatly reduced in the later ages and was entirely absent around the developmentally quiescent proximal regions of the ducts. Early in prostate development, CD44 was prominent in the mesenchyme. However, in the later phases, CD44 expression became associated with membranes of epithelial cells. The role of hyaluronan-CD44 interactions in ductal branching morphogenesis was studied by serum-free organ culture of mouse anterior prostate. In the presence of optimal levels of testosterone, the organs underwent ductal branching morphogenesis. Treatment with either neutralizing anti-CD44 antibodies, hyaluronan hexasaccharides or the enzyme hyaluronidase inhibited androgen-stimulated ductal branching morphogenesis. These results are suggestive of the significant role played by hyaluronan-CD44 interactions in mediating androgen-induced prostatic growth and morphogenesis.
Polydactyly and ectopic ZPA formation in Alx-4 mutant mice
Authors: Qu Shimian , Niswender Kevin D. , Ji Qunsheng , van der Meer Riet , Keeney Diane , Magnuson Mark A. , Wisdom Ron 
Published: April 2021

ABSTRACT
Correct development of the limb is dependent on coordination between three distinct signaling centers. Recently, fibroblast growth factor-4 has been identified as a crucial determinant of AER function, which directs limb bud outgrowth, and Sonic hedgehog has been identified as a signaling molecule that mediates ZPA function, which specifies anterior-posterior patterning in the developing limb bud. In addition, Shh and FGF-4 reciprocally reinforce each other’s expression via a positive feedback loop, providing a molecular basis for the coordination of limb bud outgrowth and anterior-posterior patterning. The mechanisms by which these signaling centers come to occupy their normal positions in the posterior limb bud during development are not understood. Here we identify and characterize Alx-4, a gene that encodes a paired-type homeodomain protein. Alx-4 is expressed in several populations of mesenchymal cells, including mesenchymal cells in the anterior limb bud, and mice homozygous for targeted disruption of the Alx-4 gene have multiple abnormalities, including preaxial polydactyly. The polydactyly is associated with the formation of an ectopic anterior ZPA, as indicated by anterior expression of Sonic hedgehog, HoxD13 and fibroblast growth factor-4. The expression of other candidate regulators of anterior-posterior positional information in the limb bud, including HoxB8 and Gli3, is not altered in Alx-4 mutant embryos. By chromosomal mapping experiments, Alx-4 is tightly linked to Strong’s luxoid, a polydactylous mouse mutant. The results identify Alx-4 as a determinant of anterior-posterior positional identity in the limb and a component of a regulatory program that restricts ZPA formation to the posterior limb bud mesenchyme.
Involvement of RBP-J in biological functions of mouse Notch1 and its derivatives
Authors: Kato Hisamune , Taniguchi Yoshihito , Kurooka Hisanori , Minoguchi Shigeru , Sakai Takashi , Nomura-Okazaki Saeko , Tamura Kumiko , Honjo Tasuku 
Published: April 2021

ABSTRACT
Notch is involved in the cell fate determination of many cell lineages. The intracellular region (RAMIC) of Notch1 trans-activates genes by interaction with a DNA binding protein RBP-J. We have compared the activities of mouse RAMIC and its derivatives in transactivation and differentiation sup-pression of myogenic precursor cells. RAMIC comprises two separate domains, IC for transactivation and RAM for RBP-J binding. Although the physical interaction of IC with RBP-J was much weaker than with RAM, transactivation activity of IC was shown to involve RBP-J by using an RBP-J null mutant cell line. IC showed differentiation suppression activity that was generally comparable to its transactivation activity. The RBP-J-VP16 fusion protein, which has strong transactivation activity, also suppressed myogenesis of C2C12. The RAM domain, which has no other activities than binding to RBP-J, synergistically stimulated transactivation activity of IC to the level of RAMIC. The RAM domain was proposed to compete with a putative co-repressor for binding to RBP-J because the RAM domain can also stimulate the activity of RBP-J-VP16. These results taken together, indicate that differentiation suppression of myogenic precursor cells by Notch signalling is due to transactivation of genes carrying RBP-J binding motifs.
Homophilic synaptic target recognition mediated by immunoglobulin-like cell adhesion molecule Fasciclin III
Authors: Kose Hiroyuki , Rose Demian , Zhu Xiaomao , Chiba Akira 
Published: April 2021

ABSTRACT
We demonstrate that the cell adhesion molecule Fasciclin III (FAS3) mediates synaptic target recognition through homophilic interaction. FAS3 is expressed by the RP3 motoneuron and its target muscles during synaptic target recognition. The RP3 growth cone can form synapses on muscles that ectopically express FAS3. This mistargeting is dependent on FAS3 expression in the motoneurons. In addition, when the FAS3-negative aCC and SNa motoneuron growth cones ectopically express FAS3, they gain the ability to recognize FAS3-expressing muscles as alternative targets. We propose that homophilic synaptic target recog-nition serves as a basic mechanism of neural network formation.
The Drosophila 14-3-3 protein Leonardo enhances Torso signaling through D-Raf in a Ras1-dependent manner
Authors: Li Willis , Skoulakis Efthimios M. C. , Davis Ronald L. , Perrimon Norbert 
Published: April 2021

ABSTRACT
14-3-3 proteins have been shown to interact with Raf-1 and cause its activation when overexpressed. However, their precise role in Raf-1 activation is still enigmatic, as they are ubiquitously present in cells and found to associate with Raf-1 in vivo regardless of its activation state. We have analyzed the function of the Drosophila 14-3-3 gene leonardo (leo) in the Torso (Tor) receptor tyrosine kinase (RTK) pathway. In the syncytial blastoderm embryo, acti-vation of Tor triggers the Ras/Raf/MEK pathway that controls the transcription of tailless (tll). We find that, in the absence of Tor, overexpression of leo is sufficient to activate tll expression. The effect of leo requires D-Raf and Ras1 activities but not KSR or DOS, two recently identi-fied essential components of Drosophila RTK signaling pathways. Tor signaling is impaired in embryos derived from females lacking maternal expression of leo. We propose that binding to 14-3-3 by Raf is necessary but not sufficient for the activation of Raf and that overexpressed Drosophila 14-3-3 requires Ras1 to activate D-Raf.
Hoxb-8 has a role in establishing early anterior-posterior polarity in chick forelimb but not hindlimb
Authors: Stratford Thomas H. , Kostakopoulou Konstadina , Maden Malcolm 
Published: April 2021

ABSTRACT
The distribution of Hoxb-8 transcripts through the chick flank and early forelimb mirrors the distribution of polarizing activity in the flank at these early stages. Polarizing activity displayed by Hoxb-8-expressing tissue is only realised when placed adjacent to the AER and appears to be mediated through Shh induction, suggesting that Hoxb-8 may lie genetically upstream of Shh. Accordingly, Hoxb-8 expression is rapidly induced by retinoic acid (RA) treatment in the anterior of the forelimb in a spatial and temporal manner that is consistent with the induction of Shh and formation of the ZPA. Furthermore, inhibition of RA synthesis in the flank downregulates the expression of endogenous Hoxb-8 and results in the loss of Shh expression. However, once the ZPA has become established the posterior limb mesoderm displays resistance to the induction of Hoxb-8 expression. Grafting of ZPA cells to the anterior of a host limb renders the host anterior tissue resistant to RA-induced Hoxb-8 expression. These results indicate that Hoxb-8 expression may be regulated by the established ZPA through a negative feedback loop. The anterior AER also secretes an inhibitory factor, preventing RA-induced or already established Hoxb-8 expression in the cells immediately underneath the AER.
Consistent with a role for Hoxb-8 in positioning of the forelimb ZPA, Hoxb-8 expression is not seen in RA-induced duplications at the anterior of the hindlimb. However, grafting of Hoxb-8-expressing tissue to the hindlimb can lead to Shh expression and similar duplications, suggesting that factors mediating ZPA formation are very similar in both wing and leg.