bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sex determination in the germ line of Drosophila melanogaster: activation of the gene Sex-lethal
Authors: Granadino Begoña , Santamaria Pedro , Sánchez Lucas 
Published: April 2021

ABSTRACT
The germ line exhibits sexual dimorphism as do the somatic tissues. Cells with the 2X;2A chromosome constitution will follow the oogenic pathway and X;2A cells will develop into sperm. In both somatic and germ-line tissues, the sexual pathway chosen by the cells depends on the gene Sex-lethal (Sxl), whose function is continuously needed for female development. In the soma, the sex of the cells is autonomously determined by the X:A signal while, in the germ line, the sex is determined by cell autonomous (the X:A signal) and somatic inductive signals. Three X-linked genes have been identified, scute (sc), sisterless-a (sis-a) and runt (run), that determine the initial functional state of Sxl in the soma. Using pole cell transplantation, we have tested whether these genes are also needed to activate Sxl in the germ line. We found that germ cells simultaneously heterozygous for sc, sis-a, run and a deficiency for Sxl transplanted into wild-type female hosts develop into functional oocytes. We conclude that the genes sc, sis-a and run needed to activate Sxl in the soma seem not to be required to activate this gene in the germ line; therefore, the X:A signal would be made up by different genes in somatic and germ-line tissues. The Sxlf7M1/Sxlfc females do not have developed ovaries. We have shown that germ cells of this genotype transplanted into wild-type female hosts produce functional oocytes. We conclude that the somatic component of the gonads in Sxlf7M1/Sxlfc females is affected, and consequently germ cells do not develop. This result supports the existence of a somatic positive feminizing signal for germ-line development. The activation of Sxl in the germ line would be controlled by cell-autonomous genetic factors (the X:A signal) and a positive feminizing function from the female gonadal soma.
Age-dependent selection against hypoxanthine phosphoribosyl transferase-deficient cells in mouse haematopoiesis
Authors: Samuel K. , Clarke A. R. , Ansell J. D. , Hooper M. L. 
Published: April 2021

ABSTRACT
The basis of a previously observed difference in the level of contribution of hypoxanthine phosphoribosyltrans-ferase-deficient cells between the haematopoietic and non-haematopoietic tissues of chimaeric and heterozy-gous mice has been clarified by studying two populations of female mice that differ only in that one is heterozy-gous for a null allele at the hprt locus and the other is wild type at this locus. Both populations are heterozy-gous for an electrophoretic variant allele at the X-linked Pgk-1 locus, so that X-chromosome inactivation generates cells expressing different isozymes of phos-phoglycerate kinase which can be assayed to monitor cell selection. The results show that hypoxanthine phospho-ribosyltransferase deficiency itself, rather than an effect of another X-linked gene, causes a reduced level of con-tribution to haematopoietic tissues. Further, the extent of the depletion increases significantly with age, and this effect is due to a progressive reduction in the level of con-tribution to haematopoietic tissues rather than to an increase in the level of contribution to non-haematopoi-etic tissues.
Influence of Drosophila ventral epidermal development by the CNS midline cells and spitz class genes
Authors: Kim Sang Hee , Crews Stephen T. 
Published: April 2021

ABSTRACT
The ventral epidermis of Drosophila melanogaster is derived from longitudinal rows of ectodermal precursor cells that divide and expand to form the ventral embryonic surface. The spitz class genes are required for the proper formation of the larval ventral cuticle. Using a group of enhancer trap lines that stain subsets of epidermal cells, it is shown here that spitz class gene function is necessary for ventral epidermal development and gene expression. Analysis of single-minded mutant embryos implies that ventral epidermal cell fate is influenced by the CNS midline cells.
Inhibition of urokinase synthesis and cell surface binding alters the motile behavior of embryonic endocardial-derived mesenchymal cells in vitro
Authors: McGuire Paul G. , Alexander Susan M. 
Published: April 2021

ABSTRACT
The expression of the serine protease urokinase is elevated during the epithelial-mesenchymal transformation of the endocardium in the developing avian heart. Elevated urokinase expression is associated with the migrating mesenchymal cells of the atrioventricular canal and bulbotruncus and not the myocardium. Treatment of isolated endocardial-derived mesenchymal cells with phosphatidyinositol-specific phospholipase C released urokinase and its receptor from the cell surface and caused significant alterations in cell morphology and motility. Likewise inhibition of urokinase synthesis by treatment of cells with antisense oligonucleotides also inhibited the migration and motility of the endocardialderived cells. These results suggest an important role for this enzyme in cell-matrix interactions and cell migration during development.
9-cis-retinoic acid, a potent inducer of digit pattern duplications in the chick wing bud
Authors: Thaller Christina , Hofmann Clementine , Eichele Gregor 
Published: April 2021

ABSTRACT
The effects of retinoids are mediated by two types of receptors, the retinoic acid receptors (RARs) and the retinoid-X-receptors (RXRs). The physiological ligand of the RARs is all-trans-retinoic acid whereas RXRs have high affinity for 9-cis-retinoic acid, a naturally occurring retinoid isomer. RXRs are broadly expressed in embryonic and adult tissues, and they are capable of forming homodimers as well as heterodimers with RARs and other nuclear hormone receptors. The role of 9-cis-retinoic acid in regulating the activity of RXR homo-dimers and RXR-containing heterodimers is poorly understood in vivo. To begin to explore the function of 9-cis-retinoic acid in morphogenesis, we have examined the activity of this isomer in the chick wing. Using reverse transcriptase polymerase chain reaction analyses, we show that RXR is expressed in stage 20 wing buds. Similar to all-trans-retinoic acid, the 9-cis-isomer induces pattern duplications when locally applied to chick wing buds, but the 9-cis isomer is about 25 times more potent than the all-trans form. Furthermore, applied all-trans-retinoic acid is converted to the 9-cis isomer in the wing bud. The ratio of 9-cis to all-trans-retinoic acid established in the tissue is approximately 1:25. This quantitative agreement between the degree of conversion and the 25-fold higher efficacy of the 9-cis isomer, raises the possibility that, at least in part, the effects of all-trans-retinoic acid on the wing pattern result from a conversion to the 9-cis isomer. Therefore, it is possible that, in this system, the actual active species is 9-cis-retinoic acid and that the all-trans form serves as a precursor.
Modulated expression of a surface epitope on migrating germ cells of Manduca sexta embryos
Authors: Nardi James B. 
Published: April 2021

ABSTRACT
In embryos of the moth Manduca sexta, the first cells that immunolabel with a monoclonal antibody to a surface epitope are the primordial germ cells. With this specific immunolabel, the migratory pathways of all primordial germ cells can be readily observed in whole mounts of embryos. The germ cells begin their migration by dispersing from an aggregate that lies on the midline of the embryonic germ band. Concurrently with segmentation of the embryo several hours later, germ cells segregate to several abdominal segments. With the advent of neurulation, germ cells again segregate, this time laterally within the segments. Shortly thereafter germ cells begin moving toward the lateral margins of abdominal segments. Simultaneously, two longitudinal strips of mesodermal cells along the lateral margins in each of four abdominal segments (3–6) begin expressing the surface epitope. The four initially noncontiguous strips on each side of the embryo fuse during the next several hours and form a single immunolabeled strip that stretches over four abdominal segments. Upon contacting these two lateral strips of mesodermal cells, germ cells begin moving bidirectionally along the anteroposterior embryonic axis toward the fifth abdominal segment where gonads will complete their morphogenesis. The immunolabel is asymmetrically distributed on the surfaces of germ cells during the early stages of migration and only during the later stages of migration after neurulation does the epitope adopt a more uniform distribution on the cells’ surfaces.
Genetic characterization of the multipotent dedifferentiated state of pigmented epithelial cells in vitro
Authors: Agata Kiyokazu , Kobayashi Hiroshi , Itoh Yoshiaki , Mochii Makoto , Sawada Kaichiro , Eguchi Goro 
Published: April 2021

ABSTRACT
Retinal pigmented epithelial cells (PECs) of chicken embryos extensively and almost synchronously transdif-ferentiate into lens cells in medium containing phenylth-iourea and testicular hyaluronidase, passing through the bipotent dedifferentiated state. We have isolated genes that are expressed specifically by either pigment or lens cells and analyzed their expression in the transdifferentiation process. The expression of some proto-oncogenes was also studied. In the dedifferentiation process, expression of the c-myc gene was enhanced and the transcription of PEC-specific genes (MMP115, pP344) was completely repressed. However, transcription of lens-specific genes (α-, β γ- and -crystallin genes) remained silent in dedifferentiated pigment cells. Activation of lens- or PEC-specific genes occurred only in conditions permissive for lens or PEC differentiation, respectively. These results indicated that lens transdifferentiation from PECs proceeds through a multipotent (or at least bipotent) intermediate cell state in which the c-myc gene is activated, but neither PEC-nor lens-specific genes are expressed.
A repressor controls the timing and spatial localisation of stalk cell-specific gene expression in Dictyostelium
Authors: Harwood A. J. , Early A. , Williams J. G. 
Published: April 2021

ABSTRACT
The ecmA and ecmB genes of Dictyostelium encode related extracellular matrix proteins and both are induced by DIF, the stalk cell-specific morphogen. The ecmA gene is expressed throughout the prestalk region of the migrating slug but only later, at culmination, do the prestalk cells express the ecmB gene. Expression of the ecmB gene is induced at the entrance to the stalk tube and we have identified two, apparently redundant, promoter elements that control this process. They act as repressors, preventing transcription in the tip of the migrating slug and the apical papilla of the culminant. They have a semi-palindromic consensus sequence TTGnCAA, where n is in one case 2 and in the other 4 bp. Either element alone is able to repress ecmB promoter activity in prestalk cells. Introduction of a single repressor element into the promoter of the ecmA gene changes its expression pattern to resemble that of the ecmB gene.
Mutant elements, where n is altered, cause repression during the slug stage but allow premature ecmB expression during culmination; suggesting that the effective strength of the inductive signal may increase during culmination. Inhibition of cAMP-dependent protein kinase (PKA) in prestalk cells blocks both stalk cell maturation and ecmB gene expression. We show that the block to gene expression correlates precisely with the presence of a functional repressor element and this is consistent with the notion that expression of the ecmB gene is controlled by a PKA-dependent release from transcriptional repression.
A central role for microtubules in the differentiation of Drosophila oocytes
Authors: Theurkauf William E. , Alberts Bruce M. , Jan Yuh Nung , Jongens Thomas A. 
Published: April 2021

ABSTRACT
Drosophila oocytes develop within cysts containing 16 cells that are interconnected by cytoplasmic bridges. Although the cysts are syncytial, the 16 cells differentiate to form a single oocyte and 15 nurse cells, and several mRNAs that are synthesized in the nurse cells accumulate specifically in the oocyte. To gain insight into the mechanisms that generate the cytoplasmic asymmetry within these cysts, we have examined cytoskeletal organization during oocyte differentiation. Shortly after formation of the 16 cell cysts, a prominent microtubule organizing center (MTOC) is established within the syncytial cytoplasm, and at the time the oocyte is determined, a single microtubule cytoskeleton connects the oocyte with the remaining 15 cells of each cyst. Recessive mutations at the Bicaudal-D (Bic-D) and egalitarian (egl) loci, which block oocyte differentiation, disrupt formation and maintenance of this polarized microtubule cytoskeleton. Microtubule assembly-inhibitors phenocopy these mutations, and prevent oocyte-specific accumulation of oskar, cyclin B and 65F mRNAs. We propose that formation of the polarized microtubule cytoskeleton is required for oocyte differentiation, and that this structure mediates the asymmetric accumulation of mRNAs within the syncytial cysts.
Genomic organization and developmental pattern of expression of the engrailed gene from the brine shrimp Artemia
Authors: Manzanares Miguel , Marco Roberto , Garesse Rafael 
Published: April 2021

ABSTRACT
We report the isolation and characterization of an engrailed gene in the crustacean Artemia franciscana. The Artemia gene spans a genomic region of 15 kilobases and the coding sequence is interrupted by two introns. It appears to be the only gene of the engrailed family present in the Artemia genome. The predicted engrailed-like protein is 349 amino acids long and contains several domains including the homeodomain, well conserved when compared to other proteins of the engrailed family. Based on sequence comparisons we have detected, in the Artemia engrailed protein, several features which are in common with the Drosophila and Bombyx engrailed proteins. It also has some features specific for invected proteins. Therefore, this gene appears to have diverged from an ancestral gene common to both the engrailed and invected insect genes. Whole-mount in situ hybridization experiments show that the expression of this gene in postembryonic development of Artemia is restricted to the posterior part of at least the thoracic and maxillar segments. The pattern is generated sequentially from a growth zone organized in columns of cells close to the caudal region of the larvae. Cell proliferation in the growth zone follows an interspersed pattern without evidence of early lineage restrictions. The engrailed expression is detected in the growth zone before any seg-mentation is visible and continues to be expressed in a posterior location in the segments that are morphologically defined. Initially expressed in isolated cells, it spreads into rows broadening to two-three cells as segments mature. The evidence presented here is compatible with the hypothesis that intercellular signaling mechanisms are in part responsible of the early activation of selector genes.
RNA regulatory element BLE1 directs the early steps of bicoid mRNA localization
Authors: Macdonald Paul M. , Kerr Karen , Smith Jeffrey L. , Leask Andrew 
Published: April 2021

ABSTRACT
Deployment of the bicoid morphogen gradient in early Drosophila embryos requires the prelocalization of bicoid mRNA to the anterior pole of the egg. This anterior localization is mediated by a cis-acting localization signal contained within the 3 ′ untranslated region of the bicoid mRNA. Here we use a series of bicoid transgenes carrying small deletions in the 3 ′ untranslated region to survey for functional elements that constitute the localization signal. We identify and characterize one essential element, BLE1, which specifically directs the early steps of localization. In addition, we find that many deletions within the bicoid mRNA 3 ′ untranslated region impair but do not prevent localization. One such deletion specifically interferes with a later step in localization. Thus the bicoid mRNA localization signal appears to consist of multiple different elements, each responsible for different steps in the localization process.
Fertile females of the mole Talpa occidentalis are phenotypic intersexes with ovotestes
Authors: Jiménez Rafael , Burgos Miguel , Sánchez Antonio , Sinclair Andrew H. , Alarcón Francisco J. , Marín Juan J. , Ortega Esperanza , Díaz de la Guardia Rafael 
Published: April 2021

ABSTRACT
We investigated the origin of XX sex reversal in the insectivorous mole Talpa occidentalis. Cytogenetic, histological and hormonal studies indicate that all XX individuals analyzed from two different populations are true hermaphrodites, with ovotestes. This suggests that XX sex reversal may be the norm in this species. The inter-sexes are functional fertile females and the trait is transmitted and maintained in the population. Intersexes lack the Y chromosome gene SRY (sex determining region Y gene), shown to be the testis determining gene. These results suggest that XX intersex moles may have arisen from a mutation of a gene located downstream from SRY/TDY in the testis determining pathway.
asense is a Drosophila neural precursor gene and is capable of initiating sense organ formation
Authors: Brand Michael , Jarman Andrew P. , Jan Lily Y. , Jan Yuh Nung 
Published: April 2021

ABSTRACT
Neural precursor cells in Drosophila arise from the ectoderm in the embryo and from imaginal disc epithelia in the larva. In both cases, this process requires daugh - terless and the proneural genes achaete, scute and lethal-of-scute of the achaete-scute complex. These genes encode basic helix-loop-helix proteins, which are nuclear transcription factors, as does the asense gene of the achaete-scute complex. Our studies suggest that asense is a neural precursor gene, rather than a proneural gene. Unlike the proneural achaete-scute gene products, the asense RNA and protein are found in the neural precursor during its formation, but not in the proneural cluster of cells that gives rise to the neural precursor cell. Also, asense expression persists longer during neural precursor development than the proneural gene products; it is still expressed after the first division of the neural precursor. Moreover, asense is likely to be down-stream of the proneural genes, because (1) asense expression is affected in proneural and neurogenic mutant backgrounds, (2) ectopic expression of asense protein with an intact DNA-binding domain bypasses the requirement for achaete and scute in the formation of imaginal sense organs. We further note that asense ectopic expression is capable of initiating the sense organ fate in cells that do not normally require the action of asense. Our studies therefore serve as a cautionary note for the inference of normal gene function based on the gain-of-function phenotype after ectopic expression.
Preimplantation mouse embryos express a cell surface receptor for tissue-plasminogen activator
Authors: Carroll Pamela M. , Richards William G. , Darrow Andrew L. , Wells James M. , Strickland Sidney 
Published: April 2021

ABSTRACT
The serine protease tissue-plasminogen activator (t-PA) has previously been shown to be intracellular in mouse secondary oocytes and extracellular in fertilized eggs. Here we demonstrate that extracellular t-PA activity is bound to the surface of the fertilized egg. The level of t-PA activity associated with preimplantation mouse embryos decreases in the 2-cell stage embryo, then increases in 4-cell and morula stage embryos. However, morulae grown in culture from fertilized eggs lack t-PA activity but are able to bind exogenously added mouse t-PA. Additionally, northern analysis indicates that preim-plantation embryos do not contain detectable levels of t-PA mRNA. Therefore, the enzyme activity associated with 4-cell and morula stage embryos in vivo is derived from t-PA present in the oviduct lumen that binds the embryo, and not from protein produced from translation of embryonic mRNA. The binding activity is species and protein specific in that neither mouse urokinase-type plasminogen activator (u-PA) nor human t-PA bind to cultured morulae. Furthermore, binding activity is dose-dependent and saturable, and does not require the active site of t-PA. These data indicate that a cell surface-specific t-PA-binding activity exists in the preimplantation mouse embryo and may localize function and concentrate the proteolytic activity of t-PA in early mouse development.
XASH-3, a novel Xenopus achaete-scute homolog, provides an early marker of planar neural induction and position along the mediolateral axis of the neural plate
Authors: Zimmerman Kathryn , Shih John , Bars Julie , Collazo Andres , Anderson David J. 
Published: April 2021

ABSTRACT
We have isolated a novel Xenopus homolog of the Drosophila achaete-scute genes, called XASH-3. XASH-3 expression is neural specific and is detected as early as stage 11, making it one of the earliest markers of neural induction so far described. Moreover, XASH-3 expression within the neural plate is regionally restricted. Transverse bands of XASH-3 mRNA mark discrete positions along the anteroposterior axis, while longitudinal bands mark a discrete position along the mediolateral axis. This latter site of XASH-3 expression appears to demarcate the prospective sulcus limitans, a boundary zone that later separates the functionally distinct dorsal (alar) and ventral (basal) regions of the spinal cord. In sandwich explants lacking any underlying mesoderm, XASH-3 is expressed in longitudinal stripes located lateral to the midline. This provides the first indication that planar or midline-derived inductive signals are sufficient to establish at least some aspects of positional identity along the mediolateral axis of the neural plate. By contrast, the transverse stripes of XASH-3 expression are not detected, suggesting that this aspect of anteroposterior neural pattern is lost or delayed in the absence of vertically passed signals. The restricted mediolateral expression of XASH-3 suggests that mediolateral patterning of the neural plate is an early event, and that this regionalization can be achieved in the absence of inducing signals derived from underlying mesoderm.
The strawberry notch gene functions with Notch in common developmental pathways
Authors: Coyle-Thompson Catherine A. , Banerjee Utpal 
Published: April 2021

ABSTRACT
Genetic and phenotypic analysis of strawberry notch suggests that its gene product is required during embryogenesis and oogenesis, and for the development of the eye, wing and leg. Several lines of evidence suggest that strawberry notch participates together with Notch in many common pathways. A number of strawberry notch mutant phenotypes are similar to those of Notch mutants and can be rescued by an extra copy of wild-type Notch. In addition, mutations in strawberry notch interact strongly with Notch mutants in a tissue-specific manner. Mutations in the strawberry notch and Notch loci also show very similar interactions with genes like Hairless, Delta, groucho, Serrate, and deltex that have all been proposed to participate in Notch related pathways. The genetic evidence presented here suggests that strawberry notch participates with members of the Notch pathway in facilitating developmentally relevant cell-cell communications.