bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metanephric mesenchyme contains multipotent stem cells whose fate is restricted after induction
Authors: Herzlinger Doris , Koseki Chizuko , Mikawa Takashi , Al-Awqati Qais 
Published: April 2021

ABSTRACTAt least fourteen epithelial cell types of the mammalian nephron develop from the metanephric mesenchyme. To distinguish whether this single embryological primor-dium contains a heterogenous population of committed renal cell lines or a multipotent stem cell, the lac-Z gene was introduced into individual renal progenitors by retroviral mediated gene transfer. The differentiated fate of Zac-Z-tagged daughters derived from single metanephric mesenchymal cells was characterized after cytodifferentiation. We found that the metanephric mesenchyme contains multipotent stem cells that can generate at least three distinct cell types; glomerular, proximal and distal epithelia. After induction the fate of this multipotent cell becomes restricted to populate a single nephron segment.
Superman, a regulator of floral homeotic genes inArabidopsis
Authors: Bowman John L. , Sakai Hajime , Jack Thomas , Weigel Detlef , Mayer Ulrike , Meyerowitz Elliot M. 
Published: April 2021

ABSTRACTWe describe a locus, SUPERMAN, mutations in which result in extra stamens developing at the expense of the central carpels in the Arabidopsis thaliana flower. The development of superman flowers, from initial primor-dium to mature flower, is described by scanning electron microscopy. The development of doubly and triply mutant strains, constructed with superman alleles and previously identified homeotic mutations that cause alterations in floral organ identity, is also described. Essentially additive phenotypes are observed in superman agamous and superman apetala2 double mutants. The epistatic relationships observed between either apetala3 or pistillata and superman alleles suggest that the SUPERMAN gene product could be a regulator of these floral homeotic genes. To test this, the expression patterns of AGAMOUS and APETALA3 were examined in superman flowers. In wild-type flowers, APETALA3 expression is restricted to the second and third whorls where it is required for the specification of petals and stamens. In contrast, in superman flowers, APETALA3 expression expands to include most of the cells that would normally constitute the fourth whorl. This ectopic APETALA3 expression is proposed to be one of the causes of the development of the extra stamens in superman flowers. The spatial pattern of AGAMOUS expression remains unaltered in superman flowers as compared to wild-type flowers. Taken together these data indicate that one of the functions of the wild-type SUPERMAN gene product is to negatively regulate APETALA3 in the fourth whorl of the flower. In addition, superman mutants exhibit a loss of determi-nacy of the floral meristem, an effect that appears to be mediated by the APETALA3 and PISTILLATA gene products.
Commitment of abdominal neuroblasts in Drosophila to a male or female fate is dependent on genes of the sex-determining hierarchy
Authors: Taylor Barbara J. , Truman James W. 
Published: April 2021

ABSTRACT
Adult specific neurons in the central nervous system of holometabolous insects are generated by the postem-bryonic divisions of neuronal stem cells (neuroblasts). In the ventral nervous system of Drosophila melanogaster, sex-specific divisions by a set of abdominal neuroblasts occur during larval and early pupal stages. Animals mutant for several sex-determining genes were analyzed to determine the genetic regulation of neuroblast commitment to the male or female pattern of division and the time during development when these decisions are made. We have found that the choice of the sexual pathway taken by sex-specific neuroblasts depends on the expression of one of these genes, doublesex (dsx). In the absence of any functional dsx+ products, the sexspecific neuroblasts fail to undergo any postembryonic divisions in male or female larval nervous systems. From the analysis of intersexes generated by dominant alleles of dsx, it has been concluded that the same neuroblasts provide the sex-specific neuroblasts in both male and female central nervous systems. The time when neuroblasts become committed to generate their sex-specific divisions was identified by shifting tra-2ts flies between the male- and female-specifying temperatures at various times during larval development. Neuroblasts become determined to adopt a male or female state at the end of the first larval instar, a time when abdominal neuroblasts enter their first postembryonic S-phase.
Sequence and expression pattern ofpax-6are highly conserved between zebrafish and mice
Authors: Püschel Andreas W. , Gruss Peter , Westerfield Monte 
Published: April 2021

ABSTRACTDespite obvious differences in the patterns of early embryonic development, vertebrates share a number of developmental mechanisms and control genes, suggesting that they use similar genetic programs at some stages of development. To examine this idea, we isolated and characterized one such gene, pax-6, a member of the pax gene family, from the zebrafish Brachydanio rerio and determined the evolutionary conservation in the structure and expression of this gene by comparison to its homolog in mice.We found two alternatively spliced forms of the zebrafish pax-6 message. Sequence and expression pattern of the zebrafish pax-6 gene are remarkably similar to its murine homolog, pax-6 expression begins during early neurulation. A stripe of cells in the neuroectoderm, including the prospective diencephalon and a part of the telencephalon, expresses pax-6 as well as the hindbrain and the ventral spinal cord extending from the level of the first rhombomere to the posterior end of the CNS. During later development more limited regions of the brain including the eye, the olfactory bulb and the pituitary gland express pax-6. Cells at the midbrain-hindbrain junction express eng genes and are separated from the neighboring pax-6 regions by several cells that express neither gene, indicating a complex subdivision of this region, pax-6 expression appears during processes when cell-to-cell signalling is thought to be important, for example during induction of the eye and regionalization of the spinal cord and brain, suggesting that it may be one component mediating the response to inductive interactions.
Pathfinding by zebrafish motoneurons in the absence of normal pioneer axons
Authors: Pike Susan H. , Melancon Eloine F. , Eisen Judith S. 
Published: April 2021

Abstract
Individually identified primary motoneurons of the zebrafish embryo pioneer cell-specific peripheral motor nerves. Later, the growth cones of secondary motoneurons extend along pathways pioneered by primary motor axons. To learn whether primary motor axons are required for pathway navigation by secondary motoneurons, we ablated primary motoneurons and examined subsequent pathfinding by the growth cones of secondary motoneurons. We found that ablation of the primary motoneuron that pioneers the ventral nerve delayed ventral nerve formation, but a normal-appearing nerve eventually formed. Therefore, the secondary motoneurons that extend axons in the ventral nerve were able to pioneer that pathway in the absence of the pathway-specific primary motoneuron. In contrast, in the absence of the primary motoneuron that normally pioneers the dorsal nerve, secondary motoneurons did not pioneer a nerve in the normal location, instead they formed dorsal nerves in an atypical position. This difference in the ability of these two groups of motoneurons to pioneer their normal pathways suggests that the guidance rules followed by their growth cones may be very different. Furthermore, the observation that the atypical dorsal nerves formed in a consistent incorrect location suggests that the growth cones of the secondary motoneurons that extend dorsally make hierarchical pathway choices.
Skeletal muscle phenotypes initiated by ectopic MyoD in transgenic mouse heart
Authors: Miner Jeffrey H. , Miller Jeffrey B. , Wold Barbara J. 
Published: April 2021

Abstract
Forced expression of the myogenic regulatory gene MyoD in many types of cultured cells initiates their conversion into skeletal muscle. It is not known, however, if MyoD expression serves to activate all or part of the skeletal muscle program in vivo during animal development, nor is it known how limiting the influences of cellular environment may be on the regulatory effects of MyoD. To begin to address these issues, we have produced transgenic mice which express MyoD in developing heart, where neither MyoD nor its three close relatives - myogenin, Myf-5, and MRF4/her-culin/Myf-6 - are normally expressed. The resulting gross phenotype in offspring from multiple, independent transgenic founders includes abnormal heart morphology and ultimately leads to death. At the molecular level, affected hearts exhibit activation of skeletal muscle-specific regulatory as well as structural genes. We conclude that MyoD is able to initiate the program that leads to skeletal muscle differentiation during mouse development, even in the presence of the ongoing cardiac differentiation program. Thus, targeted misexpression of this tissue-specific regulator during mammalian embryogenesis can activate, either directly or indirectly, a diverse set of genes normally restricted to a different cell lineage and a different cellular environment.
Prenatal expression of the growth hormone (GH) receptor/binding protein in the rat: a role for GH in embryonic and fetal development?
Authors: Garcia-Aragón Juanita , Lobie Peter E. , Muscat George E. O. , Gobius Kari S. , Norstedt Gunnar , Waters Michael J. 
Published: April 2021

Abstract
Although fetal growth is generally considered to be independent of pituitary growth hormone (GH), it is possible that pituitary GH plays a modulatory role in organ development or that a GH-like substance of non pituitary origin may influence fetal growth through the GH receptor. Accordingly, we have used immunohisto-chemisty, northern blot analysis, the reverse transcriptase-polymerase chain reaction and solution hybridization to study the ontogeny of the GH receptor/binding protein (BP) from the 12-day-old embryo (E12) to the E18 rat fetus.
GH receptor/BP immunoreactivity was observed in all major organ systems of the E18 rat fetus and was not preferentially associated with any germ layer derivative. A general increase in GH receptor/BP immunoreactivity was evident from E12 to E18, with a marked increase occurring between E16 and E18. Hemangioblastic tissue was, however, strongly or intensely immunoreactive at all stages of development, as was the placenta. Most noteworthy of the other tissues expressing GH receptor/BP immunoreactivity by day 18 were skeletal and smooth muscle, chondroprogenitor cells, epithelial lining cells, neuronal ganglia, ependymal cells and the adrenal cortex. In the placenta, the most prominent immunoreactivity was associated with decidual cells.
Total RNA was isolated from E12 to E18 rat fetuses and adult rat liver. Northern hybridization with a 35S-labelled rat GH receptor cRNA probe revealed that 3.9 kb and 1.2 kb transcripts complementary to the rat GH receptor ribopobe are present from at least E16. The existence of GH receptor mRNA at E12 and E14 was demonstrated by the polymerase chain reaction. Solution hybridization analysis demonstrated an exponential increase in the total embryonic GH receptor/BP mRNA during fetal development. However even by E18 levels were only 8% those of adult liver.
In conclusion, we have demonstrated the presence and defined the ontogeny of the GH receptor/BP in the rat foetus from mid gestation. These results, when combined with earlier studies of GH action on fetal tissues suggest a réévaluation of the role of GH in prenatal growth.
Evolutionary dissociation between cleavage, cell lineage and embryonic axes in sea urchin embryos
Authors: Henry Jonathan J. , Klueg Kristin M. , Raff Rudolf A. 
Published: April 2021

Abstract
Using vital dye staining and the microinjection of fluorescent cell lineage-autonomous tracers, the relationship between the first cleavage plane and the prospective larval dorsoventral axis was examined in several sea urchin species, including: Strongylocentrotus purpuratus, S. droebachiensis, Lytechinus pictus, Clypeaster rosaceus, Heliocidaris tuberculata and H. erythrogramma. The results indicate that there is no single relationship between the early cleavage pattern and the dorsoventral axis for all sea urchins; however, specific relationships exist for individual species. In S. purpuratus the first cleavage plane occurs at an angle 45 degrees clockwise with respect to the prospective dorsoventral axis in most cases, as viewed from the animal pole. On the other hand, in S. droebachiensis, L. pictus and H. tuberculata, the first cleavage plane generally corresponds with the plane of bilateral symmetry. There does not appear to be a predominant relationship between the first cleavage plane and the dorsoventral axis in C. rosaceus. In the direct-developing sea urchin H. erythrogramma the first cleavage plane bisects the dorsoventral axis through the frontal plane. Clearly, evolutionary differences have arisen in the relationship between cleavage pattern and developmental axes. Therefore, the mechanism of cell determination is not necessarily tied to any particular pattern of cell cleavage, but to an underlying framework of axial systems resident within sea urchin eggs and embryos.
Embryonic cytoplasmic extracts rescue murine androgenones to the blastocyst stage
Authors: Hagemann Lora J. , First Neal L. 
Published: April 2021

Abstract
Androgenones (paternally derived genome) show a significant inability to form a blastocoele cavity. Eighty percent of these embryos die or arrest at earlier stages. Factor(s) from both normal and partbenogenetic late preimplantation embryos injected into each blastomere of androgenetic 4-cell stage can rescue more than twice as many to the blastocyst stage (47.2% versus 19.2% for non-injected androgenones). This factor(s) becomes available beginning at the 4-cell stage and is titratable. Injected total cytoplasmic mRNA will also cause a rescue response. Isolating this specific factor message(s) will permit the eventual cloning of possibly the earliest parentally imprinted gene(s) expressed during development.
Expression of the Brachyury gene during mesoderm development in differentiating embryonal carcinoma cell cultures
Authors: Vidricaire Gaël , Jardine Karen , McBurney Michael W. 
Published: April 2021

ABSTRACT
When aggregated and treated with dimethyl sulfoxide (DMSO), P19 embryonal carcinoma cells differentiate into cell types normally derived from the mesoderm and endoderm including epithelium and cardiac and skeletal muscle. The Brachyury gene is expressed transiently in these differentiating cultures several days before the appearance of markers of the differentiated cell types. The expression of Brachyury is not affected by DMSO but is induced by cell aggregation, which requires extracellular calcium. Expression of Brachyury is also induced by various members of the TGFβ family such as activin and bone morphogenetic proteins. D3 is a mutant clone of P19 cells selected for its failure to differentiate when aggregated in DMSO. Aggregated D3 cells express Brachyury mRNA suggesting that the mutation(s) responsible for the phenotype of D3 cells is downstream of the chain of events initiated by Brachyury expression.
The murine type II TGF-β receptor has a coincident embryonic expression and binding preference for TGF-β1
Authors: Lawler Sean , Candia Albert F. , Ebner Reinhard , Shum Lillian , Lopez Alfredo R. , Moses Harold L. , Wright Christopher V. E. , Derynck Rik 
Published: April 2021

ABSTRACT
We have isolated cDNAs of the murine type II TGF-β receptor and have found a conserved cytoplasmic domain, but a less extensive homology in the extracellular receptor domain between the human and murine homologues. In situ hybridization analysis of the mouse fetus during mid gestation localized the expression of this receptor to various developing tissues, primarily in the mesenchyme and epidermis. This expression pattern correlates well with the expression of TGF-β in general and especially TGF-β1, suggesting that TGF-β1 exerts its developmental role through this receptor in an autocrine or paracrine fashion. Type II receptor expression was not detected in the central nervous system and developing cartilage. These tissues lack TGF-β1 expression but express TGF-β2 and/or TGF-β3, suggesting that they may exert their activities through separate receptor isoforms. In addition, the efficient binding of TGF-β1, but not TGF-β2, to the cloned type II receptor strengthens the likelihood that additional type II receptor isoforms exist which display preferential binding to TGF-β2 and have their own defined role in development.
Primitive streak mesoderm-like cell lines expressing Pax-3 and Hox gene autoinducing activities
Authors: Pruitt Steven C. 
Published: April 2021

ABSTRACT
Differentiating P19 embryonal carcinoma (EC) cells transiently express an endogenous activity capable of inducing Pax-3 expression in adjacent P19 stem cells (Pruitt, Development 116, 573-583, 1992). In the present study, expression of this activity in mesodermal cell lineages is demonstrated. First, expression of the mesodermal marker Brachyury correlates with expression of Pax-3-inducing activity. Second, the ability of leukemia inhibitory factor (LIF) to block mesoderm differentiation at two different points is demonstrated and correlated with the inhibition of Pax-3-inducing activity. Finally, two mesodermal cell lines that express Pax-3-inducing activity were derived from P19 EC cells. Each of these lines expresses high levels of the mesodermal marker Brachyury and high levels of Oct-3/4 (which is down-regulated at early times during mesoderm differentiation) suggesting that these lines are early mesodermal derivatives.
Unlike EC or embryonic stem cell lines, each of the two mesodermal derivatives autoinduces Hox gene expression on aggregation even in the presence of LIF. Following aggregation, anterior-specific genes are expressed more rapidly than more posterior genes. These observations directly demonstrate the ability of murine mesodermal derivatives to autoinduce Hox gene expression in the absence of signals from other cell lineages. Similar to the Pax-3-inducing activity, signals from mesodermal cell lines were sufficient to induce HOX expression in adjacent P19 stem cells in cell mixing assays. These observations are consistent with the previous suggestion (Blum, M., Gaunt, S. J., Cho, K. W. Y., Steinbeisser, H., Blumberg, B., Bittner, D. and De Robertis, E. M. (1992)Cell 69, 1097-1106) that signals responsible for anterior-posterior organizer activity are localized to the anterior primitive streak mesoderm of the mouse embryo.
Dye-coupling in the root epidermis of Arabidopsis is progressively reduced during development
Authors: Duckett Catherine M. , Oparka Karl J. , Prior Denton A. M. , Dolan Liam , Roberts Keith 
Published: April 2021

ABSTRACT
Epidermal cells of the Arabidopsis thaliana root are derived from a ring of 16 or so initials (stem cells) that are located just below the quiescent centre of four central cells. Derivatives of these initials divide transversely in the meristem-atic region of the root to produce files of cells that subsequently elongate and differentiate. There are two kinds of cell file in the epidermis, hair cells and non-hair cells, that are organised in an ordered pattern and become distinguishable within a few divisions of the initials. It is likely that local intercellular communication plays an important role in the early establishment of this pattern, enabling cells to register their position and fate. We have therefore examined the extent to which cells in the root apex are sym-plastically coupled through plasmodesmata. Using a variety of dye loading methods we show that the undifferentiated cells are dye-coupled i.e. cells in the meristem and the elongation zone are symplastically connected, but that cells gradually become symplastically isolated as the cells differentiate. By the time that visible hair outgrowth is observed the cells of the epidermis are symplastically isolated. This resembles the pattern of gap-junction connectivity observed in many animal systems where cells are coupled at the stage that cell patterns become established, but become progressively more isolated as they differentiate.
Relationship between retinoic acid and sonic hedgehog, two polarizing signals in the chick wing bud
Authors: Helms Jill , Thaller Christina , Eichele Gregor 
Published: April 2021

ABSTRACT
Local application of all-trans-retinoic acid (RA) to the anterior margin of chick limb buds results in pattern duplications reminescent of those that develop after grafting cells from the zone of polarizing activity (ZPA). RA may act directly by conferring positional information to limb bud cells, or it may act indirectly by creating a polarizing region in the tissue distal to the RA source. Here we demonstrate that tissue distal to an RA-releasing bead acquires polarizing activity in a dose-dependent manner. Treatments with pharmacological (beads soaked in 330 μg/ml) and physiological (beads soaked in 10 μg/ml) doses of RA are equally capable of inducing digit pattern duplication. Additionally, both treatments induce sonic hedgehog (shh; also known as vertebrate hedgehog-1, vhh-1), a putative ZPA morphogen and Hoxd-11, a gene induced by the polarizing signal. However, tissue transplantation assays reveal that pharmacological, but not physiological, doses create a polarizing region. This differential response could be explained if physiological doses induced less shh than pharmacological doses. However, our in situ hybridization analyses demonstrate that both treatments result in similar amounts of mRNA encoding this candidate ZPA morphogen. We outline a model describing the apparently disparate effects of pharmcologic and physiological doses RA on limb bud tissue.
Products, genetic linkage and limb patterning activity of a murine hedgehog gene
Authors: Chang David T. , López Alric , Kessler Doris P. von , Chiang Chin , Simandl B. Kay , Zhao Renbin , Seldin Michael F. , Fallon John F. , Beachy Philip A. 
Published: April 2021

ABSTRACT
The hedgehog (hh) segmentation gene of Drosophila melanogaster encodes a secreted signaling protein that functions in the patterning of larval and adult structures. Using low stringency hybridization and degenerate PCR primers, we have isolated complete or partial hh-like sequences from a range of invertebrate species including other insects, leech and sea urchin. We have also isolated three mouse and two human DNA fragments encoding distinct hh-like sequences. Our studies have focused upon Hhg-1, a mouse gene encoding a protein with 46% amino acid identity to hh. The Hhg-1 gene, which corresponds to the previously described vhh-1 or sonic class, is expressed in the notochord, ventral neural tube, lung bud, hindgut and posterior margin of the limb bud in developing mouse embryos. By segregation analysis the Hhg-1 gene has been localized to a region in proximal chromosome 5, where two mutations affecting mouse limb development previously have been mapped. In Drosophila embryos, ubiquitous expression of the Hhg-1 gene yields effects upon gene expression and cuticle pattern similar to those observed for the Drosophila hh gene. We also find that cultured quail cells transfected with a Hhg-1 expression construct can induce digit duplications when grafted to anterior or middistal but not posterior borders within the developing chick limb; more proximal limb element duplications are induced exclusively by mid-distal grafts. Both in transgenic Drosophila embryos and in transfected quail cells, the Hhg-1 protein product is cleaved to yield two stable fragments from a single larger precursor. The significance of Hhg-1 genetic linkage, patterning activity and proteolytic processing in Drosophila and chick embryos is discussed.