bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic expression of the cell adhesion molecule fasciclin I during embryonic development in Drosophila
Authors: Mcallister Linda , Goodman Corey S. , Zinn Kai 
Published: April 2021

Abstract
A number of different cell surface glycoproteins expressed in the central nervous system (CNS) have been identified in insects and shown to mediate cell adhesion in tissue culture systems. The fasciclin I protein is expressed on a subset of CNS axon pathways in both grasshopper and Drosophila. It consists of four homologous 150-amino acid domains which are unrelated to other sequences in the current databases, and is tethered to the cell surface by a glycosyl-phosphatidylinositol linkage. In this paper we examine in detail the expression of fasciclin I mRNA and protein during Drosophila embryonic development. We find that fasciclin I is expressed in several distinct patterns at different stages of development. In blastoderm embryos it is briefly localized in a graded pattern. During the germ band extended period its expression evolves through two distinct phases. Fasciclin I mRNA and protein are initially localized in a 14-stripe pattern which corresponds to segmentally repeated patches of neuroepithelial cells and neuroblasts. Expression then becomes confined to CNS and peripheral sensory (PNS) neurons. Fasciclin I is expressed on all PNS neurons, and this expression is stably maintained for several hours. In the CNS, fasciclin I is initially expressed on all commissural axons, but then becomes restricted to specific axon bundles. The early commissural expression pattern is not observed in grasshopper embryos, but the later bundle-specific pattern is very similar to that seen in grasshopper. The existence of an initial phase of expression on all commissural bundles helps to explain the loss-of-commissures phenotype of embryos lacking expression of both fasciclin I and of the D-abl tyrosine kinase. Fasciclin I is also expressed in several nonneural tissues in the embryo.
Activation of the easter zymogen is regulated by five other genes to define dorsal-ventral polarity in the Drosophila embryo
Authors: Chasan Rebecca , Jin Yishi , Anderson Kathryn V. 
Published: April 2021

Abstract
The product of the Drosophila easter gene, a member of the trypsin family of serine proteases, must be more active ventrally than dorsally to promote normal embryonic polarity. The majority of the easter protein in the embryo is present in the unprocessed zymogen form and appears to be evenly distributed in the extracellular space, indicating that the asymmetric activity of wildtype easter must arise post-translationally. A dominant mutant form of easter that does not require cleavage of the zymogen for activity (ea ▵N) is active both dorsally and ventrally. The ea ▵N mutant bypasses the requirement for five other maternal effect genes, indicating that these five genes exert their effects on dorsal-ventral patterning solely by controlling the activation of the easter zymogen. We propose that dorsal-ventral asymmetry is initiated by a ventrally-localized molecule in the vitelline membrane that nucleates an easter zymogen activation complex, leading to the production of ventrally active easter enzyme.
Differential expression of gap junction mRNAs and proteins in the developing murine kidney and in experimentally induced nephric mesenchymes
Authors: Sainio Kirsi , Gilbert Scott F. , Lehtonen Eero , Nishi Miyuki , Kumar Nalin M. , Gilula Norton B. , Saxén Lauri 
Published: April 2021

ABSTRACT
The expression of three gap junction (GJ) proteins, α1 (Cx43), β1 (Cx32), and β2 (Cx26), and their transcripts were examined during the ontogeny of the mouse and rat kidney. These proteins were expressed in two non-overlapping patterns. The α1 GJ protein was first observed in mesenchymal cells in the 12-day mouse kidney. By day 14 and thereafter, the α1 protein was detected in the transient S-shaped bodies, but not in the podocytes of the maturing glomeruli. After birth the antigen was retained in a small subset of secretory tubules.
The β1 and β2 GJ proteins were similar in their developmental patterns. They were first detected in a small subset of secretory tubules in the subcortical zone of day 17 embryos. These tubules were identified by immuno histochemical markers to be proximal. At birth, practically all proximal tubules expressed the two antigens.
This analysis of GJ proteins was consistent with the results of S1 nuclease protection assays showing that, while the α1 mRNA appeared early during kidney development and declined around birth, the two β mRNAs appeared later and became intensified during the last days of intrauterine development.
In experimentally induced metanephric mesenchymes, a transient expression of the α1 GJ protein was seen during the segregation of the tubular anlagen. β1 and β2 GJ proteins were not detected in such induced mesenchymes cultivated up to 7 days.
These observations provide evidence for the cellspecific utilization of different GJ genes during different stages of kidney organogenesis. The α1 gene is activated during the early segregation of the secretory tubule and might contribute to its compartmentalization, while the β1 and β2 gene products are not detected until advanced stages of development. The latter gene products might be correlated with the physiological activity of the proximal tubules in vivo, as they are not expressed in experimentally induced tubules detectable with markers for proximal tubules.
Development of left/right handedness in the chick heart
Authors: Hoyle Christine , Brown Nigel A. , Wolpert Lewis 
Published: April 2021

ABSTRACT
The chick heart tube develops from the fusion of the right and left areas of precardiac mesoderm and in almost all cases loops to the embryo’s right-hand side. We have investigated whether any intrinsic difference exists in the right and left areas of precardiac mesoderm, that influences the direction of looping of the heart tube. Chick embryos incubated to stages 4,5 and 6 were cultured by the New method. Areas of precar-diac mesoderm were exchanged between donor and host embryos of the same stage and different stages to form control, double-right and double-left sided embryos. Overall, double-right sided embryos formed many more left-hand loops than double-left sided embryos. At stages 4 and 5 a small percentage of double-right embryos formed left-hand loops (13%) whereas at stage 6 almost 50% of hearts had left-hand loops. Control embryos formed right-hand loops in 97% of cases. The stability of right-hand heart looping by double-left sided embryos, may be related to the process of ‘conversion’, whereas the direction of looping by double-right sided embryos has become randomised. There is some indication that an intrinsic change occurred in the precar-diac mesoderm between stages 5 and 6 that later influenced the direction of looping of the heart tube. The direction of body turning is suggested to be linked to the direction of heart looping.
Induction of follicle formation and hair growth by vibrissa dermal papillae implanted into rat ear wounds: vibrissa-type fibres are specified
Authors: Jahoda Colin A. B. 
Published: April 2021

ABSTRACT
Adult vibrissa follicle dermal papillae have the capacity to induce hair growth and follicle formation when associated with epidermis from various sources. However, the range of conditions under which hair follicle induction will take place has not been established. The question of whether or not the adult papilla carries information to impose fibre-type specificity has also not been fully answered. This study describes how the implantation of isolated papillae into small incisional cuts on the rat ear pinna resulted in the subsequent emergence of abnormally large hair fibres from the wound sites. Many of these hairs were found to display vibrissa-type characteristics. Histological observations indicated that the papillae had interacted with the edges of the wound epidermis to produce new, and particularly large follicles, while immunohistochemical staining revealed that early follicle construction was accompanied by a profusion of the basement membrane constituents laminin and type IV collagen in the subjacent dermis. These findings show that adult rat papillae retain the capacity, as displayed by embryonic dermis, to determine vibrissa specificity in induced follicles.
Generation and early differentiation of glial cells in the first optic ganglion of Drosophila melanogaster
Authors: Winberg Margaret L. , Perez Sharon E. , Steller Hermann 
Published: April 2021

ABSTRACT
We have examined the generation and development of glial cells in the first optic ganglion, the lamina, of Drosophila melanogaster. Previous work has shown that the growth of retinal axons into the developing optic lobes induces the terminal cell divisions that generate the lamina monopolar neurons. We investigated whether photoreceptor ingrowth also influences the development of lamina glial cells, using P element enhancer trap lines, genetic mosaics and birthdating analysis. Enhancer trap lines that mark the differentiating lamina glial cells were found to require retinal innervation for expression. In mutants with only a few photoreceptors, only the few glial cells near ingrowing axons expressed the marker. Genetic mosaic analysis indicates that the lamina neurons and glial cells are readily separable, suggesting that these are derived from distinct lineages. Additionally, BrdU pulse-chase experiments showed that the cell divisions that produce lamina glia, unlike those producing lamina neurons, are not spatially or temporally correlated with the retinal axon ingrowth. Finally, in mutants lacking photoreceptors, cell divisions in the glial lineage appeared normal. We conclude that the lamina glial cells derive from a lineage that is distinct from that of the L-neurons, that glia are generated independently of photoreceptor input, and that completion of the terminal glial differentiation program depends, directly or indirectly, on an inductive signal from photoreceptor axons.
Expression of four zebrafish wnt-related genes during embryogenesis
Authors: Krauss Stefan , Korzh Vladimir , Fjose Anders , Johansen Terje 
Published: April 2021

ABSTRACT
The wnt gene family codes for a group of cysteine-rich, secreted proteins, which are differentially expressed in the developing embryo and are possibly involved in cellular communication. Here, we describe the polymerase chain reaction based cloning and embryonic expression patterns of four zebrafish wnt-related sequences; wnt[a], wnt[b], wnt[c] and wnt[d]. One of these genes, wnt[a], is a potential homologue of murine Wnt-3, while the other three genes most likely represent new members of the vertebrate wnt gene family. In zebrafish embryos, transcripts of wnt[a] are confined to the dorsal diencephalon, the dorsal midbrain, the rhombic lips and the dorsal portions of the spinal cord. wnt[b] is expressed in the tail bud and at considerably lower levels in the mesoderm of the head. wnt[c] transcripts are present within the diencephalon and the posterior midbrain whereas wnt[d] shows a surprisingly similar expression pattern to zebrafish wnt-1. By analogy to wnt-1, it is likely that the members of the zebrafish wnt gene family play an important role in cell-to-cell signalling during pattern formation in the neural tube and the tail bud.
The big brain gene of Drosophila functions to control the number of neuronal precursors in the peripheral nervous system
Authors: Rao Yi , Bodmer Rolf , Jan Lily Y. , Jan Y. N. 
Published: April 2021

ABSTRACT
big brain (bib) is one of the six known zygotic neurogenic genes involved in the decision of an ectodermal cell to take on the neurogenic or the epidermogenic cell fate. Previous studies suggest that bib functions in a pathway separate from the one involving Notch and other known neurogenic genes. For a better understanding of the bib function, it is essential first to characterize the mutant phenotype in detail. Our mutant analyses show that loss of bib function approximately doubles the number of neuronal precursors and their progeny cells in the embryonic peripheral nervous system. Mosaic studies reveal a hypertrophy of sensory bristles in bib mutant patches in adult flies. Our observations are compatible with a function of bib in specifying neuronal precursors of both the embryonic and adult sensory nervous system. This is in contrast to the function of Notch, which continues to be required at multiple stages of neural development subsequent to this initial determination event.
The relationship of gap junctions and compaction in the preimplantation mouse embryo
Authors: Becker David L. , Leclerc-David Catherine , Warner Anne 
Published: April 2021

ABSTRACT
In the mouse embryo, gap junctions first appear at the 8-cell stage as compaction is about to take place. Compaction of the embryo is important for the differentiation of the first two cell types; the inner cell mass and the trophectoderm. Our studies examine the contribution of gap junctional communication at this stage of development We have characterised the normal sequence of appearance of gap junction protein and its distribution. The extent of communication as shown by the passage of dye between cells has been recorded in both normal embryos and embryos treated with drugs that influence gap junctional communication. Comparisons have been made with embryos that express a lethal gap junction defect and attempts were made to rescue such embryos by increasing their gap junction communication.
Lachesin: an immunoglobulin superfamily protein whose expression correlates with neurogenesis in grasshopper embryos
Authors: Karlstrom Rolf O. , Wilder Leigh P. , Bastiani Michael J. 
Published: April 2021

ABSTRACT
We describe the developmental expression in grasshopper (Schistocerca americana) and molecular characterization in grasshopper and fruit fly (Drosophila melanogaster) of Lachesin, a novel immunoglobulin superfamily protein. Lachesin is expressed on the surfaces of differentiating neuronal cells from the onset of neurogenesis in both the central and peripheral nervous systems. Lachesin expression begins in some cells of the neurogenic ectoderm immediately after engrailed expression begins in the posterior cells of each future segment. All neurogenic cells express Lachesin early, but only those cells that become neuroblasts continue to express Lachesin. Ectodermal cells in the neurogenic region that adopt non-neuronal fates lose Lachesin at the time that they diverge from a potentially neurogenic pathway. Neuroblasts, ganglion mother cells and neurons all express Lachesin early in their lives, but expression becomes restricted to a subset of neurons as development progresses. Sensory neurons express Lachesin as they delaminate from the body wall ectoderm. Lachesin is also present on growing axons of the CNS and PNS and becomes restricted to a subset of axons later in development. This expression is unique among known insect neurogenic genes and suggests a role for Lachesin in early neuronal differentiation and axon outgrowth.
Grasshopper Lachesin is a 38×103Mr protein linked to cell membranes through a glycosyl phosphatidylinositol anchor. We have cloned the Lachesin gene from both grasshopper and fly. The proteins are highly conserved (70% identical) between the two species. Lachesin is similar to Drosophila amalgam, bovine OBCAM and the human poliovirus receptor, putting it into a subgroup of the immunoglobulin superfamily containing one Vand two C2-type immunoglobulin domains. Lachesin is also similar to several other vertebrate immunoglobulin superfamily proteins (TAG-1, F11, L1 and NgCAM) known to function in neurite outgrowth and other cell surface recognition events.
The chicken CdxA homeobox gene and axial positioning during gastrulation
Authors: Frumkin Ayala , Haffner Rebecca , Shapira Eli , Tarcic Nora , Gruenbaum Yosef , Fainsod Abraham 
Published: April 2021

ABSTRACT
The chicken homeobox containing gene, CdxA (formerly CHox-cad), was previously shown to be expressed during gastrulation. Localization of CdxA transcripts by in situ hybridization to tissue sections revealed that, during gastrulation, expression of this gene exhibits a posterior localization along the primitive streak. The transcripts are localized to epiblast cells in the vicinity of the primitive streak, to cells of the primitive streak itself and in the definitive endoderm as it replaces the hypoblast.
In order to study in greater detail the pattern of expression of the CdxA gene during gastrulation, we expressed the full-length CdxA protein as a fusion protein in E. coli and generated monoclonal antibodies against it. Chicken embryos at different stages of gastrulation were processed for whole-mount immunohistochemical localization of the protein using anti-CdxA antibodies. Once the pattern of expression in the whole embryo was determined, the same embryos were sectioned to determine the identity of the cells expressing the CdxA protein. Detailed analysis of the CdxA protein in embryos, from the onset of primitive streak formation to the beginning of the tail bud stage (stages 2 to 10), has shown different patterns of expression during primitive streak elongation and regression. The CdxA protein is initially detected at the posterior marginal zone and the expression moves rostrally into the primitive streak during mid-streak stages. As the primitive streak elongates, the CdxA stripe of expression moves anteriorly. By definitive streak stages, the CdxA stripe of expression delineates a position along the anteriorposterior axis in the primitive streak. CdxA, like its Drosophila homologue cad, is expressed during gastrulation in a stripe localized to the posterior region of the embryo. These observations suggest that CdxA as a homeobox gene may be part of a regulatory network coupled to axial determination during gastrulation in the early chick embryo.
Expression of the Fgf6 gene is restricted to developing skeletal muscle in the mouse embryo
Authors: deLapeyrière Odile , Ollendorff Vincent , Planche Jacqueline , Ott Marie Odile , Pizette Sandrine , Coulier François , Birnbaum Daniel 
Published: April 2021

ABSTRACT
Fgf6, a member of the Fibroblast Growth Factor (FGF) family, is developmentally regulated and its expression is highly restricted in the adult. To gain further insight into the role of Fgf6, we studied its expression during embryogenesis using RNA in situ hybridization. Fgf6 expression is restricted to developing skeletal muscle. Fgf6 transcripts are first detected in the somites at 9.5 days post-conceptus, and expression continues in developing skeletal muscles up to at least 16.5 days post-conceptus. Fgfr4 is a putative receptor for FGF6. Its pattern of expression during myogenesis overlaps that of Fgf6, but both genes are not expressed in exactly the same population of cells. In addition, recombinant FGF6 protein is able to repress the terminal differentiation of myoblasts in culture, providing additional support to the concept that FGF6 plays an important role in myogenesis.
Expression of epithelial alkaline phosphatase in segmentally iterated bands during grasshopper limb morphogenesis
Authors: Chang Wesley S. , Zachow Karen R. , Bentley David 
Published: April 2021

ABSTRACT
Although the study of rostral-caudal segmentation of the insect body has been a rich source of information about embryonic pattern formation, relatively little is known of the process of proximal-distal segmentation of insect appendages. Here we demonstrate that during the period of limb segmentation, five segmentally iterated, sharply demarcated bands of cell surface alkaline phosphatase activity are expressed in embryonic grasshopper limbs. These bands span each intersegmental boundary in the limb as well as one boundary within the tarsus. Within appendages, expression is restricted to epithelial cells, where activity is present on both apical and basolateral surfaces. This epithelial alkaline phosphatase remains active at neutral pH, is insensitive to levamisole inhibition, and is strongly inhibited by nucleoside monophosphates. Treatment of embryos with phosphatidylinositol-specific phospholipase C releases almost all visible chromogenic activity, indicating that the epithelial alkaline phosphatase is anchored to the plasma membrane by glycosyl-phosphatidylinositol. When material released by phosphatidylinositol-specific phospholipase C is separated on native polyacrylamide gels, a single broad band of enzymatic activity is detected following incubation with substrate. A polyclonal antiserum raised against a 55×103Mr alkaline phosphatase from shrimp recognizes a single band of 56×103Mr on immunoblots of grasshopper membrane proteins. The spatially restricted expression of epithelial alkaline phosphatase suggests that it may be involved in epithelial cell rearrangements or shape changes associated with limb segmentation and morphogenesis. It also may contribute to definition of axon routes in the limb, since pioneer afferent growth cones turn at, and migrate along, the edge of one alkaline phosphatase-expressing epithelial domain.
Expression of the Sex-lethal gene is controlled at multiple levels during Drosophila oogenesis
Authors: Bopp Daniel , Horabin Jamila I. , Lersch Robert A. , Cline Thomas W. , Schedl Paul 
Published: April 2021

ABSTRACT
In addition to controlling somatic sexual development in Drosophila melanogaster, the Sex-lethal (Sxl) gene is required for proper differentiation of female germ cells. To investigate its role in germ-line development, we have examined the expression of Sxl in wild-type ovaries and ovaries that are defective in early steps of germ cell differentiation. As in the soma, the basic mechanism for on/off regulation of Sxl relies on sex-specific processing of its transcripts in germ cells. One class of female-sterile mutations, which includes fs(1)1621 and the tumorous-ovary-producing allele of the ovarian tumor gene, otu1, is defective in the splicing process. These mutants have germ lines with high amounts of Sxl RNA spliced in the male mode and a severe reduction of protein levels in the germ cells. Another class of female-sterile mutations produces a phenotype similar to that seen in fs(1)1621 and otu1 but appears to express normal levels of Sxl protein in the germ cells. However, this second class does not show the changes in protein distribution normally observed in wild-type germ cells. In the wild-type germarium, the non-differentiated germ cells show a strong cytoplasmic accumulation of Sxl protein followed, as the germ cells differentiate, by a dramatic reduction and redistribution of the protein into nuclear foci. Interestingly, two female-sterile alleles of Sxl, Sxf4 and Sxlf5 belong to the second class, which shows persistent cytoplasmic accumulation of Sxl protein. These Sxl female-sterile mutants encode an altered protein indicating that Sxl regulates processes that eventually lead to the changes in Sxl protein distribution. Lastly, we demonstrate that during the final stages of oogenesis several mechanisms must operate to prevent the progeny from inheriting Sxl protein. Conceivably, this regulation safeguards the inadvertent activation of the Sxl autoregulatory feedback loop in the male zygote.