bluuebunny/crossref_metadata_2025 huggingface dataset:
Interacting signalling pathways regulating prestalk cell differentiation and movement during the morphogenesis of Dictyostelium
Authors: Williams Jeff , Hopper Neil , Early Anne , Traynor David , Harwood Adrian , Abe Tomoaki , Simon Marie Noelle , Véron Michel
Published: April 2021

Analysis of the expression patterns of two genes encoding extracellular matrix proteins shows there to be an unexpectedly complex pattern of prestalk cell differentiation and movement during the morphogenesis of Dictyostelium. The organism employs both cell sorting and positional differentiation to generate a patterned structure but these two mechanisms are used at different times during development. During slug formation prestalk cells arise at scattered positions within the aggregate and then move to its apex to form the tip. In contrast, during culmination, stalk cell differentiation occurs in a positionally localized manner at the entrance to the stalk tube.

Two interacting signalling pathways regulate the differentiation of prestalk and stalk cells. Prestalk cell differentiation is induced by DIF, a chlorinated hexaphenone, and a repression mechanism prevents DIF acting to induce premature stalk cell differentiation during slug migration. At culmination intracellular cAMP levels rise, the cAMP dependent protein kinase (PKA) is activated and the block to stalk cell differentiation is lifted. Activation of PKA is also necessary in order that prestalk cells move to the entrance of the stalk tube at culmination. Thus, in Dictyostelium, PKA plays a role both in the regulation of cellular differentiation and in morphogenetic cell movement.
Dissecting the modes of interactions amongst cell adhesion molecules
Authors: Simmons David L.
Published: April 2021

The process of cell adhesion can be mediated by more than 50 molecules. Fortunately, most of these can be grouped into a small number of superfamilies. For example, more than half of all leukocyte adhesion molecules are members of the immunoglobulin super-family. The principles of cell-cell adhesion are reviewed including: kinetics and equilibria; on/off rates; affinities/avidities; homotypic/heterotypic interactions; mapping and delineation of binding sites. These principles are illustrated with two CAMs: firstly the interaction of the homotypic epithelial/myeloid adhesins CD66, and the endothelial adhesin, CD31, and secondly the heterotypic adhesins ICAM-1, 2 and 3, which interact with the leukocyte integrin LFA-1.
Tumor suppressor genes encoding proteins required for cell interactions and signal transduction in Drosophila
Authors: Bryant Peter J. , Watson Kellie L. , Justice Robin W. , Woods Daniel F.
Published: April 2021

Tumor suppressor genes, whose products are required for the control of cell proliferation, have been identified by their mutant phenotype of tissue overgrowth. Here we describe recent work on the molecular identification of tumor suppressor genes that function in two different cell types of the Drosophila larva: the blood cells, and the undifferentiated epithelial cells of developing imaginai discs. Mutations in the aberrant immune responses (air8) gene lead to overproduction and precocious differentiation of blood cells. This gene encodes the Drosophila homolog of human ribosomal protein S6. The mutant phenotype is consistent with a role for S6 in the control of cell proliferation, and is compatible with findings from mammalian cells where alterations in S6 expression and phosphorylation are associated with changes in cell proliferation. Mutations in the dises large (dlg) gene cause neoplastic overgrowth of imaginai discs in the larva. The mutant discs show loss of septate .junctions and of apical-basal cell polarity, and they also lose the ability to differentiate cuticular structures. The d/g protein product (DlgA) is localized at septate junctions between epithelial cells, and cDNA sequencing indicates that the gene product includes a domain with homology to guanylate kinase (GUK). Two mammalian homologs of this gene have been identified, and one of them (PSD-95/SAP90) encodes a component of synaptic densities in the brain: this protein therefore resembles the DlgA protein in being located in a specialized cell junction that functions in information transfer between cells. Mutations in the fat gene cause hyperplastic imaginai disc overgrowth, in which the overgrowing disc tissue retains its epithelial structure and its ability to differentiate. Some of the excess disc tissue is shed as vesicles suggesting a loss of cell adhesion. In support of this hypothesis, the predicted gene product shows homology to cadherins in its extracellular domain. However, the fat protein is much larger than known cadherins. As in human cancer, somatic loss of the normal alleles of tumor suppressor genes can lead to tumor formation in Drosophila; an example of this is provided by the warts (wts) locus. The wts gene was identified by the dramatic overgrowth of mitotic recombination clones that are homozygous for a wts deletion. In these clones the cuticle intrudes between epithelial cells, suggesting an alteration in cell adhesion. The study of these and other tumor suppressor genes in Drosophila is providing new evidence supporting the critical role of cell interactions and specialized apical junctions in controlling epithelial cell proliferation.
Studies on the teratogenic properties of trypan blue and its components in mice
Authors: Barber Aeleta N. , Geer Jack C.
Published: April 2021

The teratogenic activity of the purified components of trypan blue was studied in pregnant mice. The blue component induced abnormalities similar in type and frequency to those caused by the whole dye, and the water-soluble purple fraction exerted a mild teratogenesis when the concentration was increased to 0 · 3 per cent. The sodium hydroxide-soluble purple and red fractions were without harmful effects. The blue and water-soluble purple fractions are absorbed and retained by the endodermal cells of the visceral yolk-sac from the time they become differentiated until term. The dye granules are associated with proteinaceous materials in apical vacuoles in the cytoplasm of these cells. Prior to the closure of the yolk-sac the dye has direct access to the embryo. Microscopic examination of unstained sections at this stage in development reveals a diffuse staining of the embryonic mass immediately adjacent to the visceral endoderm. The suggestion is offered that cessation of the teratogenic activity of the dye after closure of the yolk-sac is due to its retention and inactivation by the cells of the yolk-sac epithelium.
Cultivation of post-implantation mouse and rat embryos on plasma clots
Authors: New D. A. T. , Stein K. F.
Published: April 2021

Mouse and rat embryos of primitive streak to early somite stages have been grown on clots of plasma and embryo extract. Of nineteen mouse embryos explanted at 8–12 somites, seventeen acquired a blood circulation and thirteen developed to limb bud stages with 24–32 somites. Of the mouse embryos explanted at 1–7 somites, 72 per cent, developed a blood circulation and 33 per cent, went on to limb bud stages. Of the mouse embryos explanted at head fold and head process stages, 60 per cent, developed over 8 somites and 26 per cent, a blood circulation. Mouse embryos explanted at primitive streak stages developed neural folds and a few somites, but not a blood circulation. Twenty-two rat embryos explanted at 6–12 somites acquired anterior limb buds and 25–30 somites. Eighty-five rat embryos explanted at head process or head fold stages mostly became 6–12 somite embryos with beating hearts. Only four formed a blood circulation. The rate of development in vitro, at least for the first 24 hr., was about the same as in vivo. The maximum amount of development obtained in vitro was equivalent to about 40 hr. in vivo. Often the blood continued to circulate for over 48 hr., and the heart to heat for over 72 hr. Addition of 4-5 per cent. CO2 to the air in the culture vessels was found to be beneficial. Increasing the O2 to 60 per cent, improved the development of the older, but not of the younger embryos. It appeared immaterial whether the embryo extract used in the culture media was obtained from chick or mouse.
Isolement expérimental du mésenchyme propre du foie et rôle morphogène de la composante mésodermique dans l’organogenèse hépatique
Authors: Douarin par Nicole Le
Published: April 2021

L’organogenèse du foie chez les Oiseaux a été décrite par de nombreux auteurs. La première ébauche hépatique visible apparait chez l’embryon de Poulet au stade de 20 à 22 somites sous forme d’une évagination endodermique au niveau de la lèvre antérieure de l’ombilic intestinal (Brouha, 1898; Choronschitzky, 1900; Hildebrandt, 1902). Cette ébauche primaire émet bientôt un premier diverticule crânial, puis un autre caudal, qui constituent les bourgeons hépatiques secondaires. Par rapport au sinus veineux, le diverticule crânial est dorsal tandis que le diverticule caudal est ventral; ils sont décrits à ce stade par Felix (1892) et Hammar (1893) en particulier. Très rapidement, ces bourgeons s’étendent vers l’avant dans le mésentère ventral correspondant au septum transversum, et constituent pendant le 3ème et le 4ème jour de l’incubation un cylindre de tissu hépatique entourant le ductus venosus. La prolifération des trabécules hépatiques est accompagnée par la formation de capillaires issus du ductus venosus comme l’ont décrit Shore (1891), Hammar (1893) et Minot (1900). Ensuite, les lobes droit et gauche du foie s’accroissent vers l’arrière dans la cavité abdominale.
A study of carbohydrate metabolism in Planorbis exustus
Authors: Sherbet Gajanan V. , Lakshmi M. S.
Published: April 2021

The metabolism of Planorbis exustus has been studied using sodium azide and iodoacetamide (IAA) at different concentrations. Azide (0 · 001,0 · 002 and 0 ·003 M) treated cleavage-stage embryos developed normally till they reached gastrulation when their development was arrested. Gastrulae stopped all morphogenetic activities. This was generally followed by hydropia. No exogastrulation was caused. The 48-, 60- and 72-hr.-old embryos showed delay in development, Vesiculation and shell abnormalities or underwent a block in development. Treatment with IAA caused arrest of development, rounding off and slight enlargement of the blastomeres. The development of this molluscan species seems to be divisible into pre-gastrulation and post-gastrulation (including gastrulation) phases. In the pre-gastrulation phase, a metabolism involving other substrates than a carbohydrate is dominant. The energy requirement of cleavage, which conceivably forms a small fraction of the total requirement of the embryo, is met by carbohydrate metabolism. The importance of the latter for morphogenetic activities is evidenced by the vulnerability of these stages to azide. The carbohydrate metabolism is also important for the processes of differentiation and growth.
Yolk utilization in the notochord of newt as studied by electron microscopy
Authors: Jurand A. , Selman G. G.
Published: April 2021

An electron microscope study has been made of the ultrastructure of the yolk platelets in notochord cells of Triturus alpestris during the larval stages when the yolk is utilized by the differentiating cells. The inner crystalline core of the platelet which at earlier stages occupies most of its volume, is progressively replaced during the process by an irregularly-ordered granular zone. This granular zone is bounded by an envelope consisting of multiple layers of lamellae. The lamellar zone is a special feature of yolk platelets in notochord during utilization.
The anlage of the cerebellar nuclei in chick after early extirpation of the vestibular region
Authors: Rüdeberg Sven-Ingvar
Published: April 2021

An experimental investigation was made into the question of whether the deep cerebellar nuclei arise embryologically through a migration of cells from the vestibular nuclei, as has been suggested in several morphological papers dealing with different vertebrate species. In very young chick embryos (about days), the neural tube was extirpated from a point just caudal to the cerebellar anlage to a point level with the second pair of somites. Incubation of the eggs then continued until the age at which the anlage of the deep cerebellar nuclei becomes clearly visible in normal chick embryos. From an extensive material, comprising 109 serially sectioned embryos, a few stages are described. These embryos were selected according to the purity of the operation and the developmental stage of the embryo. A developmental series is thus described from HH 30-HH 36, in which stages the cerebellar nuclear anlage forms and differentiates into its different portions in normal chick embryos. Despite large gaps in the brain and lack of vestibular nuclei, the morphology of the cerebellum, as well as its nuclear anlagen, appears to be normal during the actual period. The conclusion reached is that the deep cerebellar nuclei in chick cannot, at least in their principal part, be considered to develop embryologically through a migration of cells from the vestibular nuclei.
Studies on embryonic determination of the harlequin-fly, Chironomus dorsalis. II. Effects of partial irradiation of the egg by ultra-violet light
Authors: yajima Hideo
Published: April 2021

Irradiation by ultra-violet light of the egg mass as a whole and partial irradiation of single eggs were employed for the analysis of embryonic determination in the harlequin-fly, Chironomus dorsalis. Three kinds of abnormalities were obtained; i.e. double malformations, single larvae with defective parts, and undifferentiated or dead eggs. Relationships between the frequency of occurrence of double malformations and the duration of exposure and developmental stage of irradiation are as follows : For exposures lasting from 0·5 to 3 min., double cephalons—duplication of cephalic structures—were obtained most often by 1·5 min. exposure and double abdomens were produced most often by 2 · 5 min. exposure. The frequency of double malformations decreases gradually after nuclear migration. Up until 1 hr. after nuclear migration, malformations are still obtained in small numbers but at 4 hr. they are no longer obtained. After partial irradiation, double cephalon was caused by posterior irradiation and double abdomen by anterior irradiation. The topographic extent of the formative localities is discussed.
Phosphoprotéine-phosphatase et résorption du vitellus chez les amphibiens: une étude cyto-chimique, électrophorétique et immunologique
Authors: Denis par H.
Published: April 2021

Les Cellules embryonnaires de la plupart des vertébrés sont caractérisées par la possession de réserves vitellines, dont la résorption accompagne et même conditionne, dans une certaine mesure, la morphogénèse. En effet, le vitellus constitue pour l’embryon le réservoir principal d’acides aminés, pièces de construction indispensables pour la synthèse protéique. La connaissance du mécanisme permettant aux tissus en différenciation de mobiliser leurs réserves d’acides aminés pour les intégrer dans de nouvelles protéines serait fort utile à notre compréhension de la morphogénèse. Deux enzymes ou groupes d’enzymes ont été jusqu’ici rendus responsables de la résorption du vitellus chez les embryons d’amphibien : la phosphoprotéine-phosphatase (PPPase), d’une part, la cathepsine et diverses peptidases, d’autre part. Chaque type d’enzyme aurait un röle bien défini dans la dégradation des réserves vitellines. La PPPase produirait une déphosphorylation du vitellus, grâce à laquelle celui-ci pourrait passer en solution. Les enzymes protéolytiques et peptidasiques scinderaient les protéines solubilisées en chaînes polypeptidiques de plus en plus courtes jusqu’au stade acide aminé. Ce schéma de la résorption du vitellus est basé principalement sur les travaux de Harris (1946), Gross (1952), Mezger-Freed (1953), Barth et Barth (1951, 1954), Flickinger (1956), Nass (1962) et Urbani (1955, 1957).
Transplantation antigens in the mouse embryo. The fate of early embryo tissues transplanted to adult hosts
Authors: Edidin Michael
Published: April 2021

The Evidence for and against the presence in cells of embryo and foetal mice of transplantation antigens, the cell-bound substances provoking the rejection of allogeneic tissue homografts, rests on two classes of experiments: those relying upon serological techniques for the detection of the antigens, and those involving some test of transplantation antigen activity in intact animals. Experiments of the former class have indicated that there are no histocompatibility antigens present on the cells of most newborn or late foetal mice, but that these antigens quickly appear during the first 2 days of neo-natal life, rendering cells liable to agglutination or lysis (Pizarro, Hoecker, Rubenstein & Ramus, 1961; Moller, 1961 a, 1961b). However, Moller (1961a) was able to show that cells of newborn mice resistant to cytotoxic isoantisera did absorb the antibodies of these sera, suggesting that the tissues of newborn mice contain transplantation antigens, but that these antigens are not present on cells in sufficient numbers to make them susceptible to agglutination or lysis. This suggestion was borne out by later experiments (Moller, 1963) in which transplantation antigens were demonstrated in 13-day embryos by injecting lethally irradiated liver cells of these embryos into allogeneic adults and measuring the injected animals’ production of humoral antibodies against the grafted tissues.
The influence of lithium on the competence of the ectoderm in Ambystoma mexicanum
Authors: Gebhardt D. O. E. , Nieuwkoop P. D.
Published: April 2021

Ectodermal sandwiches of Ambystoma mexicanum of stage (Harrison) containing anterior notochord as inductor were treated with a 0·05 M LiCl solution for 24 hr. It was found that lithium was capable of changing the neural induction pattern of these explants by increasing the number of rhombencephalic and spino-cordal inductions and decreasing the number of prosencephalic ones. Sandwiches made from ectoderm of various developmental stages (stages 8 –12) and not containing an inductor were treated with the lithium solution for 2- or 24-hr. periods. In the explants made with ectoderm of stage 8, stage 9 or stage a very characteristic type of cell displacement occurred which resembled the phenomenon of exogastrulation. The ectoderm of the younger stages was shown to be mesodermalized and entodermalized to a considerable extent by the treatment. The period of mesodermal competence of the ectoderm, as judged by its reactivity towards lithium, extends from stage 8 (or earlier) up to stage (Harrison). The different periods of primary competence for (a) meso- and ento-dermalization, and (b) activation (neuralization) of the ectoderm are considered. Also the subsequently acquired competence for (c) transformation (caudalization) of the activated ectoderm into more caudal neural structures is discussed. The various periods of competence are presented in the form of a diagram together with the corresponding inductive stimuli.
Comportement en culture in vitro des ébauches dentaires de rongeurs prélevées aux stades de prédifférenciation
Authors: Pourtois par M.
Published: April 2021

DÈs 1936, Glasstone a montré que des bourgeons dentaires de Mammifères, prélevés à des stades précoces, peuvent modeler in vitro toutes les cúspides et les sillons de la dent adulte, c’est à dire les détails caractéristiques de leur morphologie définitive.
The activity of hair follicles in parabiotic rats
Authors: Ebling F. J. , Hervey G. R.
Published: April 2021

Hair growth in the rat occurs in a series of waves, which start ventrally and pass over the flanks to the back (Dry, 1926; Butcher, 1934; Johnson, 1958a). The activity of the hair follicle is cyclic; when the hair has been fully formed there is a period of quiescence during which the dead hair is retained as a ‘club’. The duration of the complete cycle varies with site and age, ranging from 24 to about 100 days (Ebling & Johnson, 1964).
Effets de Factinomycine D sur la morphogénèse et le métabolisme des acides nucléiques chez l’embryon de poulet
Authors: Heilporn-Pohl par V.
Published: April 2021

On admet généralement que Factinomycine D bloque la synthèse de l’acide ribonucléique messager (m-RNA) en se combinant à l’acide désoxyribonucléique (DNA) (Reich, Goldberg et Rabinowitz, 1962; Shatkin, 1962) et en inhibant de ce fait la RNA polymérase.
A microscopic study of chlorpromazine (largactil) treated axolotl larvae
Authors: Eyal-Giladi H. , Eyal Z. , Eshel S.
Published: April 2021

In previous publications (Eyal-Giladi & Eyal, 1962; Eyal & Eyal-Giladi, 1963) some of the macroscopic effects produced by chlorpromazine (CPZ) on the development and growth rate of Axolotl embryos have been reported. They include different abnormalities (microcephaly, defects in eyes, gills and pigmentation) depending on the CPZ concentration used and the length of the immersion period. In addition, larvae subjected to high CPZ concentrations and longer time of treatment proved, at the time of fixation, to be smaller than the controls, whereas larvae treated by low CPZ concentrations tended to grow bigger than the controls.
Transient embryonic antigens in the chick
Authors: McCallion D. J. , Trott J. C.
Published: April 2021

Immunochemical analysis of the 9-day chick brain with 9-day brain antiserum reveals significant amounts of two different groups of antigens. One group consists of at least three antigens. The other group consists of at least two antigens. Comparison of 9-day brain with other 9-day organs and with adult organs, including adult brain, reveals that the group of three antigens are common antigens and that one of them is transient and disappears by hatching. It is further shown that of the group of two antigens at least one is neural-specific and transient and disappears from the brain by hatching.
The origin of the abnormalities of the inner ear in dreher mice
Authors: Deol M. S.
Published: April 2021

The abnormalities of the inner ear in dreher mice may be viewed as the consequences of an incomplete or weak differentiation of the otic vesicle. As it is known from experimental work on other vertebrates that this differentiation depends on the inductive influence of the neural tube, it was thought that the neural tube might be abnormal in these animals. It was found that not only is the neural tube abnormal, but its abnormalities are seen at least one day before those of the inner ear. The relevance of these findings to mutants with defects of the eyes is discussed.
The effects of transection and extirpation on axis formation and elongation in the young mouse embryo
Authors: Smith Lois Jean
Published: April 2021

An in vitro method is described whereby it is possible to perform transection and extirpation experiments on the young mouse embryo. Mouse embryos having 4 – 7 (rarely 8) somites at the beginning of culture were incubated for 18 – 20 hr. Intact embryos added 6 – 10 somites, the number depending on the number at the beginning of culture. Other systems, particularly gut and heart, showed even greater differentiation. The axial level at which they were transected determined the ways in which the transected embryos differed from the intact embryos. Notochord lengths in the cut embryos varied with the experiment but the base of the notochord was always present and at the same level. The neural folds closed or remained open depending on whether or not somitic mesoderm fused under them. Fusion of somitic mesoderm was affected by the presence or absence of notochord. The number of new somites formed, however, was unaffected by the experimental manipulations and all were found to come from cells located anterior to the node at the beginning of culture. Gut differentiation was unchanged. The results of all experiments were similar to those obtained from experiments in the chick.
Expression and function of Pax 1 during development of the pectoral girdle
Authors: Timmons Paula M. , Wallin Johan , Rigby Peter W. J. , Balling Rudi
Published: April 2021

Pax 1 is a member of the paired-box containing gene family. Expression has previously been observed in the developing sclerotomes and later in the anlagen of the intervertebral discs. Analysis of Pax 1-deficient undulated mice revealed an important role for this gene in the development of the axial skeleton, in which Pax 1 apparently functions as a mediator of notochordal signals during sclerotome differentiation. Here we demonstrate that Pax 1 is also transiently expressed in the developing limb buds. A comparative phenotypic analysis of different undulated alleles shows that this expression is of functional significance. In mice that are mutant for the Pax 1 gene severe developmental abnormalities are found in the pectoral girdle. These include fusions of skeletal elements which would normally remain separate, and failures in the differentiation of blastemas into cartilaginous structures. Although Pax 1 is also expressed in the developing hindlimb buds and Wolffian ridge, no malformations could be detected in the corresponding regions of Pax 1 mutant mice. These findings show that, in addition to its role in the developing vertebral column, Pax 1 has an important function in the development of parts of the appendicular skeleton.
The ‘prespore-like cells’ of Dictyostelium have ceased to express a prespore gene: analysis using short-lived β-galactosidases as reporters
Authors: Detterbeck Susanne , Morandini Piero , Wetterauer Birgit , Bachmair Andreas , Fischer Karin , MacWilliams Harry K.
Published: April 2021

In transgenic strains of Dictyostelium discoideum that express β-galactosidase under the control of a prespore-specific promoter, only early slugs show reporter confined to the prespore zone. As slugs migrate β-galactosidase-positive cells accumulate in the prestalk zone; ultimately, there may be so many that the prestalk-prespore boundary is no longer distinguishable (Harwood, A., Early, A., Jermyn, K. and Williams, J. (1991)Differentiation 46, 7-13). It is not clear whether these ‘anomalous’ reporter-positive cells currently express prespore genes; another possibility is that they are ex-prespore cells that have transformed to prestalk and sorted to the prestalk zone (Sternfeld, J. (1993) Roux Archiv. Dev. Biol. 201, 354-363), while retaining their previously produced reporter. To test the activity of the prespore genes in these cells, we have made prespore reporter constructs whose products decay quickly; these are based on constructs used to investigate protein turnover in yeast (Bachmair, A., Finley, D. and Varshavsky, A. (1986) Science 234, 179-186). In strains bearing such constructs, β-galactosidase-positive cells do not appear in the prestalk zone. The apparent deterioration of the prestalk/prespore pattern in older slugs is thus an artefact of reporter stability.
Fate mapping of the silkworm, Bombyx mori, using localized UV irradiation of the egg at fertilization
Authors: Myohara Maroko
Published: April 2021

Bombyx eggs at the fertilization stage (0-2 hours after oviposition) were irradiated with a scanning UV-laser microbeam (355 nm) over an area of about 1% of the total egg surface. In spite of absence of nuclei or cells at the irradiated sites, larvae from treated eggs showed localized cuticle defects in the integument. The location and frequency of the defects within the cuticular pattern correlated closely to the site of irradiation both in the antero-posterior and the dorsoventral direction. Based on the correlation, presumptive regions for each larval segment were located and a fate map of the Bombyx egg was established.
MyoD expression marks the onset of skeletal myogenesis in Myf-5 mutant mice
Authors: Braun Thomas , Bober Eva , Rudnicki Michael A. , Jaenisch Rudolf , Arnold Hans-Henning
Published: April 2021

The expression pattern of myogenic regulatory factors and myotome-specific contractile proteins was studied during embryonic development of Myf-5 mutant mice by in situ hybridization and immunohistochemistry.

In contrast to somites in wild-type embryos, no expression of myogenin and Myf-6 (MRF4), or any other myotomal markers was detected in mutant animals at E9.0 and E10.0 indicating that Myf-5 plays a crucial role during this developmental period. Significantly, the onset of MyoD expression in rostral somites of E10.5 embryos was unaffected by the Myf-5 mutation suggesting that the activation of the MyoD gene occurs independently of Myf-5 at the correct developmental time. Immediately after the activation of MyoD myogenin transcripts and protein accumulated within the myotome. The first contractile proteins of the sarcomeric apparatus appeared slightly later. By E11.5 the expression of muscle markers were indistinguishable between wild-type and Myf-5 mutant mice.

The migration of muscle precursor cells that leave the somites to form limb musculature was monitored in Myf-5-mutant mice by Pax-3 expression. Pax-3-positive cells were equally found in somites and limbs of E10.0 wild-type and mutant mice indicating that myogenic factor expression at the level of somites is not a prerequisite for determination and subsequent migration of limb precursor cells.
open brain, a new mouse mutant with severe neural tube defects, shows altered gene expression patterns in the developing spinal cord
Authors: Günther Thomas , Struwe Marina , Aguzzi Adriano , Schughart Klaus
Published: April 2021

We describe a new mouse mutation, designated open brain (opb), which results in severe defects in the developing neural tube. Homozygous opb embryos exhibited an exen-cephalic malformation involving the forebrain, midbrain and hindbrain regions. The primary defect of the exen-cephaly could be traced back to a failure to initiate neural tube closure at the midbrain-forebrain boundary. Severe malformations in the spinal cord and dorsal root ganglia were observed in the thoracic region. The spinal cord of opb mutant embryos exhibited an abnormal circular to oval shape and showed defects in both ventral and dorsal regions. In severely affected spinal cord regions, a dor-salmost region of cells negative for Wnt-3a, Msx-2, Pax-3 and Pax-6 gene expression was detected and dorsal expression of Pax-6 was increased. In ventral regions, the area of Shh and HNF-3β expression was enlarged and the future motor neuron horns appeared to be reduced in size. These observations indicate that opb embryos exhibit defects in the specification of cells along the dorsoventral axis of the developing spinal cord. Although small dorsal root ganglia were formed in opb mutants, their metameric organization was lost. In addition, defects in eye development and malformations in the axial skeleton and developing limbs were observed. The implications of these findings are discussed in the context of dorsoventral patterning of the developing neural tube and compared with known mouse mutants exhibiting similar defects.
Role of leukemia inhibitory factor and its receptor in mouse primordial germ cell growth
Authors: Cheng Linzhao , Gearing David P. , White Lynn S. , Compton Debra L. , Schooley Ken , Donovan Peter J.
Published: April 2021

The pleiotropic cytokine leukemia inhibitory factor (LIF) is able to promote the growth of mouse primordial germ cells (PGCs) in culture. It is unclear whether LIF acts directly on PGCs or indirectly via feeder cells or embryonic somatic cells. To understand the role of LIF in PGC growth, we have carried out molecular and cell culture analyses to investigate the role of both the LIF ligand and its receptor in PGC development. LIF is able to stimulate PGC growth independently of the presence of feeder cells supporting the hypothesis that LIF acts directly on PGCs to promote their growth. We show here that transcripts for the low-affinity LIF receptor (LIFR), an integral component of the functional LIF receptor complex, are expressed in the developing gonad. Fluorescence-activated cell sorter (FACS) analysis, using an anti-LIFR antiserum, demonstrates that LIFR is present on the surface of PGCs, suggesting that PGCs are likely to be a direct target of LIF action in culture. Signalling via LIFR is essential for PGC growth in culture since the anti-LIFR antiserum, which blocks LIF binding to its receptor, abolishes PGC survival in culture. Two LIF-related cytokines, namely oncostatin M and ciliary neurotrophic factor, can also promote PGC growth in culture in addition to LIF. Thus one or more of these LIFR-dependent cytokines may play an important role in PGC development in mice.
The Serrate locus of Drosophila and its role in morphogenesis of the wing imaginal discs: control of cell proliferation
Authors: Speicher Stephan A. , Thomas Ulrich , Hinz Uwe , Knust Elisabeth
Published: April 2021

The Drosophila gene Serrate encodes a transmembrane protein with 14 EGF-like repeats in its extracellular domain. Here we show that loss-of-function mutations in this gene lead to larval lethality. Homozygous mutant larvae fail to differentiate the anterior spiracles, exhibit poorly developed mouth-hooks and show a severe reduction in the size of the wing and haltere primordia, which is not due to cell death. The few homozygous mutant escapers that pupariate develop into pharate adults that almost completely lack wings and halteres. Clonal analysis in the adult epidermis demonstrates a requirement for Serrate during wing and haltere development. Targeted ectopic expression of Serrate in the imaginal discs using the yeast transcriptional activator Gal4 results in regionally restricted induction of cell proliferation, e. g. the ventral tissues in the case of the wings and halteres. The results suggest that the wild-type function of Serrate is required for the control of position-specific cell proliferation during development of meso- and metathoracic dorsal discs, which in turn exerts a direct effect on morphogenesis.
Dual regulation of the glycogen phosphorylase 2 gene of Dictyostelium discoideum: the effects of DIF-1, cAMP, NH3 and adenosine
Authors: Yin Yizhong , Rogers Patricia V. , Rutherford Charles L.
Published: April 2021

Cell differentiation in Dictyostelium results in the formation of two cell types, stalk and spore cells. The stalk cells undergo programmed cell death, whereas spore cells retain viability. The current evidence suggests that stalk cell differentiation is induced by Differentiation Inducing Factor (DIF), while spore cell differentiation occurs in response to cAMP. We have discovered the first developmentally regulated Dictyostelium gene, the glycogen phosphorylase gene 2 (gp2) gene, that can be induced by both DIF-1 and cAMP, suggesting the possibility of a new group of developmentally regulated genes that have DIF-1 and cAMP dual responsiveness. The gp2 gene was found to be expressed in both prestalk/stalk cells and prespore/spore cells. The DIF-1 competence of the gp2 gene required uninterrupted development, whereas the cAMP-competence for the gene required only starvation. Both DIF-1 and cAMP induction of the gene could be inhibited by NH3, a factor that is thought to act as a developmental signal in Dictyostelium. Another developmental signal, adenosine, was found to repress the DIF-1 induction of the gp2 gene. Two introns in the gp2 gene were examined for their involvement in the regulation of the gene, but no regulatory function was detected. A model for the regulation of the gp2 gene during the development is proposed.
Null mutations in the αPS2 and βPS integrin subunit genes have distinct phenotypes
Authors: Brown Nicholas H.
Published: April 2021

The two Drosophila position-specific (PS) integrins are expressed on complementary sides of sites where different cell layers adhere to each other, such as the attachments of the embryonic muscles to the epidermis. While there is suggestive evidence that the PS integrin-mediated adhesion is via the extracellular matrix, it is also possible that it occurs through the direct interaction of the two integrins, αPS1βPS and αPS2βPS. To help distinguish between these possibilities a comparison between the phenotypes caused by the absence of the βPS subunit and the absence of one of the PS α subunits, αPS2, has been made. Two pieces of evidence are provided that prove that the αPS2 subunit is encoded by the locus inflated (if). Firstly, three new if alleles have been isolated, each of which is associated with a molecular lesion in the αPS2 gene, and each of which results in the complete loss of if activity. Secondly, a 39 kb fragment of genomic DNA that encompasses the αPS2 gene completely rescues if mutations when introduced into the germline by P-element-mediated transformation. A comparison of the null inflated phenotype with that of the locus that encodes the βPS subunit, myospheroid (mys), reveals that while the βPS subunit is required for the adhesion of the epidermis along the dorsal midline, the αPS2 subunit is not. In if mutant embryos, the muscles remain attached to the other cell layers significantly longer than in a mys mutant embryo. This shows that the αPS2βPS integrin only contributes part of the adhesive activity at the sites of PS integrin adhesion, and rules out a model where PS integrin function occurs solely by the direct interaction of the two PS integrins.
The mago nashi locus encodes an essential product required for germ plasm assembly in Drosophila
Authors: Newmark Phillip A. , Boswell Robert E.
Published: April 2021

In Drosophila, the localization of maternal determinants to the posterior pole of the oocyte is required for abdominal segmentation and germ cell formation. These processes are disrupted by maternal effect mutations in ten genes that constitute the posterior group. Here, the molecular analysis of one posterior group gene, mago nashi, is presented. Restriction fragment length polymorphisms and transcript alterations associated with mago nashi mutations were used to identify the mago nashi locus within a chromosomal walk. The mago nashi locus was sequenced and found to encode a 147 amino acid protein with no similarity to proteins of known or suspected function. The identification of the mago nashi locus was confirmed by sequencing mutant alleles and by P element-mediated transformation. Nonsense mutations in mago nashi, as well as a deletion of the 5′ coding sequences, result in zygotic lethality. The original mago nashi allele disrupts the localization of oskar mRNA and staufen protein to the posterior pole of the oocyte during oogenesis; anterior localization of bicoid mRNA is unaffected by the mutation. These results demonstrate that mago nashi encodes an essential product necessary for the localization of germ plasm components to the posterior pole of the oocyte.
Embryonic expression and cloning of the murine GATA-3 gene
Authors: George Kathleen M. , Leonard Mark W. , Roth Matthew E. , Lieuw Ken H. , Kioussis Dimitris , Grosveld Frank , Engel James Douglas
Published: April 2021

We describe the embryonic expression pattern as well as the cloning and initial transcriptional regulatory analysis of the murine (m) GATA-3 gene. In situ hybridization shows that mGATA-3 mRNA accumulation is temporally and spatially regulated during early development: although found most abundantly in the placenta prior to 10 days of embryogenesis, mGATA-3 expression becomes restricted to specific cells within the embryonic central nervous system (in the mesencephalon, diencephalon, pons and inner ear) later in gestation. GATA-3 also shows a restricted expression pattern in the peripheral nervous system, including terminally differentiating cells in the cranial and sympathetic ganglia. In addition to this distinct pattern in the nervous system, mGATA-3 is also expressed in the embryonic kidney and the thymic rudiment, and further analysis showed that it is expressed throughout T lymphocyte differentiation.

To begin to investigate how this complex gene expression pattern is elicited, cloning and transcriptional regulatory analyses of the mGATA-3 gene were initiated. At least two regulatory elements (one positive and one negative) appear to be required for appropriate tissue-restricted regulation after transfection of mGATA-3-directed reporter genes into cells that naturally express GATA-3 (T lymphocytes and neuroblastoma cells). Furthermore, this same region of the locus confers developmentally appropriate expression in transgenic mice, but only in a subset of the tissues that naturally express the gene.
Expression of the heparin-binding cytokines, midkine (MK) and HB-GAM (pleiotrophin) is associated with epithelial-mesenchymal interactions during fetal development and organogenesis
Authors: Mitsiadis Thimios A. , Salmivirta Markku , Muramatsu Takashi , Muramatsu Hisako , Rauvala Heikki , Lehtonen Eero , Jalkanen Markku , Thesleff Irma
Published: April 2021

Midkine (MK) and heparin binding-growth associated molecule (HB-GAM or pleiotrophin), constitute a new family of heparin-binding proteins implicated in the regulation of growth and differentiation (T. Muramatsu (1993)Int. J. Dev. Biol. 37, 183-188). We used affinity-purified antibodies against MK and HB-GAM to analyze their distribution during mouse embryonic development. From 9 to 14.5 day post-coitum (dpc), both proteins were detected in central and peripheral nervous systems, facial processes, limb buds, sense organs, respiratory, digestive, urogenital, and skeletal systems. MK and HB-GAM were often localized on the surface of differentiating cells and in basement membranes of organs undergoing epithelial-mesenchymal interactions. The levels of MK protein decreased considerably in the 16.5 dpc embryo, whereas HB-GAM staining persisted in many tissues. Our in situ hybridization results revealed a widespread expression of MK transcripts that was not always consistent with the distribution of MK protein in developing tissues. In many epithelio-mesenchymal organs MK and HB-GAM were codistributed with syndecan-1, a cell surface proteoglycan. In limb buds and facial processes, MK, HB-GAM, and syndecan-1 were localized to the apical epithelium and the adjacent proliferating mesenchyme. Both MK and HB-GAM bound syndecan-1 in solid-phase assays in a heparan sulfate-dependent manner. The biological effects of MK and HB-GAM on limb and facial mesenchyme were studied in vitro by application of beads preloaded with the proteins. Neither MK nor HB-GAM stimulated mesenchymal cell proliferation or induced syndecan-1 expression. Taken together these results indicate that MK and HB-GAM may play regulatory roles in differentiation and morphogenesis of the vertebrate embryo, particularly in epithelio-mesenchymal organs, and suggest molecular interactions with syndecan-1.
cloche, an early acting zebrafish gene, is required by both the endothelial and hematopoietic lineages
Authors: Stainier Didier Y. R. , Weinstein Brant M. , Detrich H. William , Zon Leonard I. , Fishman Mark C.
Published: April 2021

Endothelial and hematopoietic cells appear synchronously on the extra-embryonic membranes of amniotes in structures known as blood islands. This observation has led to the suggestion that these two ventral lineages share a common progenitor. Recently, we have shown in the zebrafish, Danio rerio, that a single cell in the ventral marginal zone of the early blastula can give rise to both endothelial and blood cells as well as to other mesodermal cells (Stainier, D. Y. R., Lee, R. K. and Fishman, M. C. (1993). Development 119, 31-40; Lee, R. K. K., Stainier, D. Y. R., Weinstein, B. M. and Fishman, M. C. (1994). Development 120, 3361-3366). Here we describe a zebrafish mutation, cloche, that affects both the endothelial and hematopoietic lineages at a very early stage. The endocardium, the endothelial lining of the heart, is missing in mutant embryos. This deletion is selective as evidenced by the presence of other endothelial cells, for example those lining the main vessels of the trunk. Early cardiac morphogenesis proceeds normally even in the absence of the endocardium. The myocardial cells form a tube that is demarcated into chambers, beats rhythmically, but exhibits a reduced contractility. This functional deficit is likely due to the absence of the endocardial cells, although it may be a direct effect of the mutation on the myocardial cells. Cell transplantation studies reveal that the endothelial defect, i.e. the endocardial deletion, is a cell-autonomous lesion, consistent with the possibility that cloche is part of a signal transduction pathway.

In addition, the number of blood cells is greatly reduced in cloche mutants and the hematopoietic tissues show no expression of GATA-1 or GATA-2, two key hematopoietic transcription factors that are first expressed during early embryogenesis. These results show that cloche is involved in the genesis and early diversification of the endothelial and blood lineages, possibly by affecting a common progenitor cell population.
Repetitive sperm-induced Ca2+ transients in mouse oocytes are cell cycle dependent
Authors: Jones Keith T. , Carroll John , Merriman Julie A. , Whittingham David G. , Kono Tomohiro
Published: April 2021

Mature mouse oocytes are arrested at metaphase of the second meiotic division. Completion of meiosis and a block to polyspermy is caused by a series of repetitive Ca2+ tran-sients triggered by the sperm at fertilization. These Ca2+ transients have been widely reported to last for a number of hours but when, or why, they cease is not known. Here we show that Ca2+ transients cease during entry into inter-phase, at the time when pronuclei are forming. In fertilized oocytes arrested at metaphase using colcemid, Ca2+ tran-sients continued for as long as measurements were made, up to 18 hours after fertilization. Therefore sperm is able to induce Ca2+ transients during metaphase but not during interphase. In addition metaphase II oocytes, but not pronuclear stage 1-cell embryos showed highly repetitive Ca2+ oscillations in response to microinjection of inositol trisphosphate. This was explored further by treating in vitro maturing oocytes at metaphase I for 4-5 hours with cycloheximide, which induced nuclear progression to inter-phase (nucleus formation) and subsequent re-entry to metaphase (nuclear envelope breakdown). Fertilization of cycloheximide-treated oocytes revealed that continuous Ca2+ oscillations in response to sperm were observed after nuclear envelope breakdown but not during interphase. However interphase oocytes were able to generate Ca2+ transients in response to thimerosal. This data suggests that the ability of the sperm to trigger repetitive Ca2+ transients in oocytes is modulated in a cell cycle-dependent manner.