bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developmental expression of G proteins in a migratory population of embryonic neurons
Authors: Horgan A.M. , Lagrange M. T. , Copenhaver P. F. 
Published: April 2021

ABSTRACT
Directed neuronal migration contributes to the formation of many developing systems, but the molecular mechanisms that control the migratory process are still poorly understood. We have examined the role of heterotrimeric G proteins (guanyl nucleotide binding proteins) in regulating the migratory behavior of embryonic neurons in the enteric nervous system of the moth, Manduca sexta. During the formation of the enteric nervous system, a group of approx. 300 enteric neurons (the EP cells) participate in a precise migratory sequence, during which the undifferentiated cells populate a branching nerve plexus that lies superficially on the visceral musculature. Once migration is complete, the cells then acquire a variety of positionspecific neuronal phenotypes. Using affinity-purified antisera against different G protein subtypes, we found no apparent staining for any G protein in the EP cells prior to their migration. Coincident with the onset of migration, however, the EP cells commenced the expression of one particular G protein, Goα. The intensity of immunostaining continued to increase as migration progressed, with Goα immunoreactivity being detectable in the leading processes of the neurons as well as their somata. The identity of the Goα-related proteins was confirmed by protein immunoblot analysis and by comparison with previously described forms of Goα from Drosophila. When cultured embryos were treated briefly with aluminium fluoride, a compound known to stimulate the activity of heterotrimeric G proteins, both EP cell migration and process outgrowth were inhibited. The effects of aluminium fluoride were potentiated by alpha toxin, a pore-forming compound that by itself caused no significant perturbations of migration. In preliminary experiments, intracellular injections of the non-hydrolyzable nucleotide GTPγ-S also inhibited the migration of individual EP cells, supporting the hypothesis that G proteins play a key role in the control of neuronal motility in this system. In addition, once migration was complete, the expression of Goα-related proteins in the EP cells underwent a subsequent phase of regulation, so that only certain phenotypic classes among the differentiated EP cells retained detectable levels of Goα immunoreactivity. Thus Go may perform multiple functions within the same population of migratory neurons in the course of embryonic development.
Mutational analysis of the Drosophila tolloid gene, a human BMP-1 homolog
Authors: Finelli Alyce L. , Bossie Cynthia A. , Xie Ting , Padgett Richard W. 
Published: April 2021

ABSTRACT
Seven zygotically active genes have been identified in Drosophila that determine the fate of dorsal cells in the developing embryo. decapentaplegic (dpp), a member of the transforming growth factor-β (TGF-β) family, appears to play the central role in dorsal ectoderm formation, as mutations in this gene confer the most severe mutant phenotype of this group of genes. dpp’s activity is modulated by tolloid, which also has a role in the determination of dorsal cell fate. tolloid encodes a protein that contains a metalloprotease domain and regulatory domains consisting of two EGF motifs and five C1r/s repeats. We have generated several mutant tolloid alleles and have examined their interaction with a graded set of dpp point alleles. Some tolloid alleles act as dominant enhancers of dpp in a trans heterozygote, and are therefore antimorphic alleles. However, a tolloid deficiency shows no such genetic interaction. To characterize the nature of the tolloid mutations, we have sequenced eighteen tolloid alleles. We find that five of the seven alleles that act as dominant enhancers of dpp are missense mutations in the protease domain. We also find that most tolloid alleles that do not interact with dpp are missense mutations in the C-terminal EGF and C1r/s repeats, or encode truncated proteins that delete these repeats. Based on these data, we propose a model in which the tolloid protein functions by forming a complex containing DPP via protein-interacting EGF and C1r/s domains, and that the protease activity of TOLLOID is necessary, either directly or indirectly, for the activation of the DPP complex. The tolloid antimorphs, which have non-conservative amino acid changes in the protease domain, would still be capable of interacting with DPP, or a complex containing DPP, via these protein-interacting domains, but unable to perform wild-type function, since protease activity would be abolished. This results in effectively inhibiting DPP’s action by sequestration in an inactive complex. Since tolloid has highly conserved homologs in other phyla, the same mechanism of activating TGF-β-like molecules may be conserved and operate in other animals.
Expression of the atrial-specific myosin heavy chain AMHC1 and the establishment of anteroposterior polarity in the developing chicken heart
Authors: Yutzey Katherine E. , Rhee Jeanne T. , Bader David 
Published: April 2021

ABSTRACT
A unique myosin heavy chain cDNA (AMHC1), which is expressed exclusively in the atria of the developing chicken heart, was isolated and used to study the generation of diversified cardiac myocyte cell lineages. The pattern of AMHC1 gene expression during heart formation was determined by whole-mount in situ hybridization. AMHC1 is first activated in the posterior segment of the heart when these myocytes initially differentiate (Hamburger and Hamilton stage 9+). The anterior segment of the heart at this stage does not express AMHC1 although the ventricular myosin heavy chain isoform is strongly expressed beginning at stage 8+. Throughout chicken development, AMHC1 continues to be expressed in the posterior heart tube as it develops into the diversified atria. The early activation of AMHC1 expression in the posterior cardiac myocytes suggests that the heart cells are diversified when they differentiate initially and that the anterior heart progenitors differ from the posterior heart progenitors in their myosin isoform gene expression. The expression domain of AMHC1 can be expanded anteriorly within the heart tube by treating embryos with retinoic acid as the heart primordia fuse. Embryos treated with retinoic acid prior to the initiation of fusion of the heart primordia express AMHC1 throughout the entire heart-forming region and fusion of the heart primordia is inhibited. These data indicate that retinoic acid treatment produces an expansion of the posterior (atrial) domain of the heart and suggests that diversified fates of cardiomyogenic progenitors can be altered.
daughterless is essential for neuronal precursor differentiation but not for initiation of neuronal precursor formation in Drosophila embryo
Authors: Vaessin Harald , Brand Michael , Jan Lily Yeh , Jan Yuh Nung 
Published: April 2021

ABSTRACT
The first steps of neuronal precursor formation require several genes that encode transcription regulators with the helix-loop-helix (HLH) motif, including the proneural genes of the achaete-scute complex AS-C (achaete (ac), scute (sc) and lethal of scute (l’sc)) and daughterless (da). The da protein dimerizes with AS-C products in vitro to form DNA-binding proteins. Previous studies have shown that the AS-C genes are expressed initially in discrete clusters of ectodermal cells (the proneural clusters) and then more strongly in the neuronal precursors that arise from these clusters and delaminate from the epidermal layer. In this paper, we studied the distribution of da protein with an antibody raised against Da. We found that Da is ubiquitously but non-uniformly distributed. Within the ectodermal layer, its level is neither elevated (as in the case of AS-C genes) nor reduced (as in the case of emc product) in the proneural cluster. It is, however, at higher levels in many neuronal precursors. We further studied the requirement of da in neuronal precursor development by using a variety of markers for neuronal precursors. Our results reveal the existence of at least two stages in neuronal precursor formation. da is not required for the initial appearance of nascent neuronal precursors but is required for these cells to express multiple neuronal precursor genes and to produce the normal number of neurons.
Isolated rat cortical progenitor cells are maintained in division in vitro by membrane-associated factors
Authors: Temple Sally , Davis Andrew A. 
Published: April 2021

ABSTRACT
Ventricular zone cells in the developing CNS undergo extensive cell division in vivo and under certain conditions in vitro. The culture conditions that promote cell division have been studied to determine the role that contact with cell membrane associated factors plays in the proliferation of these cells. Progenitor cells have been taken from the ventricular zone of developing rat cerebral cortex and placed into microwells. Small clusters of these cells can generate large numbers of neurons and non-neuronal progeny. In contrast, single progenitor cells largely cease division, approximately 90% acquiring neuron-like characteristics by 1 day in vitro. DiI-labeled, single cells from embryonic day 14 cortex plated onto clusters of unmarked progenitor cells have a significantly higher probability (approximately 3-fold) of maintaining a progenitor cell phenotype than if plated onto the plastic substratum around 100 μm away from the clusters. Contact with purified astrocytes also promotes the progenitor cell phenotype, whereas contact with meningeal fibroblasts or balb3T3 cells promotes their differentiation. Membrane homogenates from cortical astrocytes stimulate significantly more incorporation of BrdU by E14 cortical progenitor cells than membrane homogenates from meningeal fibroblasts. These data indicate that the proliferation of rat cortical progenitor cells can be maintained by cell-type specific, membrane-associated factors.
The Drosophila miti-mere gene, a member of the POU family, is required for the specification of the RP2/sibling lineage during neurogenesis
Authors: Bhat Krishna Moorthi , Schedl Paul 
Published: April 2021

ABSTRACT
The Drosophila POU gene miti-mere (previously known as pdm2) has a complex spatial and temporal pattern of expression during early development; initially it is expressed in gap-gene-like pattern, then in 14 stripes and finally in a subset of the cells in the developing CNS and PNS. To study the function of this gene during develop-ment, we generated a ‘synthetic anti-morphic mutation’ by expressing a truncated version of the miti protein from a constitutive hsp83 and an inducible hsp70 promoter. We show that these Δmiti transgenes behave like classical anti-morphic mutations. Using these dominant negative trans-genes, together with deletions and a duplication for the gene, we show that miti is required during segmentation and neurogenesis. We have also used temperature-shift experiments with the hsp70Δmiti transgene to demonstrate that miti function in segmentation is distinct and separable from its function during neurogenesis. In segmentation, miti appears to be required in the specification of the segments A2 and A6. In the CNS, miti is required for the elaboration of the NB4-2→GMC-1→RP2/sib lineage. miti is initially required in this lineage to establish the identity of the parental ganglion mother cell, GMC-1. miti must then be down-regulated to allow the asymmetric division of GMC-1 into the RP2 and its sibling cell.
Dax, a locust Hox gene related to fushi-tarazu but showing no pair-rule expression
Authors: Dawes Rachel , Dawson Iain , Falciani Francesco , Tear Guy , Akam Michael 
Published: April 2021

ABSTRACT
We describe an unusual Antennapedia class homeobox gene from the grasshopper Schistocerca gregaria (Orthoptera, African Plague Locust). Its sequence is not sufficiently similar to that of any other insect Hom-Hox gene to identify it unambiguously, but short conserved elements suggest a relationship to the segmentation gene fushi-tarazu, (ftz). We term it Sg Dax (divergent Antenna-pedia class homeobox gene). Antibodies raised against the protein encoded by this gene reveal two phases of expression during embryogenesis. In the early embryo, it is a marker for the posterior part of the forming embryonic primordium, and subsequently for the posterior part of the growing germ band. In older embryos, it labels a subset of neural precursor cells in each trunk segment, very similar to that defined by the expression of fushi tarazu (ftz) in Drosophila. We suggest that Schistocerca Dax and Drosophila ftz are homologous members of a gene family whose members are diverging relatively rapidly, both in terms of sequence and role in early development.
Expression of the BDNF gene in the developing visual system of the chick
Authors: Herzog Karl-Heinz , Bailey Karen , Barde Yves-Alain 
Published: April 2021

ABSTRACT
Using a sensitive and quantitative method, the mRNA levels of brain-derived neurotrophic factor (BDNF) were determined during the development of the chick visual system. Low copy numbers were detected, and BDNF was found to be expressed in the optic tectum already 2 days before the arrival of the first retinal ganglion cell axons, suggesting an early role of BDNF in tectal development. After the beginning of tectal innervation, BDNF mRNA levels markedly increased, and optic stalk transection at day 4 (which prevents subsequent tectal innervation) was found to reduce the contralateral tectal levels of BDNF mRNA. Comparable reductions were obtained after injection of tetrodotoxin into one eye, indicating that, already during the earliest stages of target encounter in the CNS, the degree of BDNF gene expression is influenced by activity-dependent mechanisms. BDNF mRNA was also detected in the retina itself and at levels comparable to those found in the tectum. Together with previous findings indicating that BDNF prevents the death of cultured chick retinal ganglion cells, these results support the idea that the tightly controlled expression of the BDNF gene might be important in the co-ordinated development of the visual system.
Characterization of Star and its interactions with sevenless and EGF receptor during photoreceptor cell development in Drosophila
Authors: Kolodkin Alex L. , Pickup Amanda T. , Lin David M. , Goodman Corey S. , Banerjee Utpal 
Published: April 2021

ABSTRACT
Loss-of-function mutations in Star impart a dominant rough eye phenotype and, when homozygous, are embryonic lethal with ventrolateral cuticular defects. We have cloned the Star gene and show that it encodes a novel protein with a putative transmembrane domain. Star transcript is expressed in a dynamic pattern in the embryo including in cells of the ventral midline. In the larval eye disc, Star is expressed first at the morphogenetic furrow, then in the developing R2, R5 and R8 cells as well as in the posterior clusters of the disc in additional R cells. Star interacts with Drosophila EGF receptor in the eye and mosaic analysis of Star in the larval eye disc reveals that homozygous Star patches contain no developing R cells. Taken together with the expression pattern at the morphogenetic furrow, these results demonstrate an early role for Star in photoreceptor development. Additionally, loss-of-function mutations in Star act as suppressors of R7 development in a sensitized genetic background involving the Son of sevenless (Sos) locus, and overexpression of Star enhances R7 development in this genetic background. Based on the genetic interactions with Sos, we suggest that Star also has a later role in photoreceptor development including the recruitment of the R7 cell through the sevenless pathway.
Involvement of inositol 1,4,5-trisphosphate-mediated Ca2+release in early and late events of mouse egg activation
Authors: Xu Zhe , Kopf Gregory S. , Schultz Richard M. 
Published: April 2021

ABSTRACT
Sperm-induced activation of mammalian eggs is associated with a transient increase in the concentration of intracellular Ca2+. The role of inositol 1,4,5-trisphosphate (IP3)mediated release of Ca2+ from intracellular stores during mouse egg activation was examined in the present study by determining the effects of microinjected monoclonal antibody (mAb) 18A10, which binds to the IP3 receptor and inhibits IP3-induced Ca2+ release, on endpoints of egg activation following insemination. The antibody inhibited in a concentration-dependent manner the ZP2 to ZP2f conversion that is involved in the zona pellucida block to polyspermy, as well as the ZP2 to ZP2f conversion promoted by microinjected IP3 in non-inseminated eggs. As anticipated, inseminated eggs that had been microinjected with the antibody were polyspermic. In addition, the antibody inhibited the fertilization-associated decrease in H1 kinase activity and pronucleus formation, and the concentration dependence for inhibition of these events was similar to that observed for inhibiting the ZP2 to ZP2f conversion. Last, the antibody inhibited the fertilization-induced recruitment of maternal mRNAs and post-translational modifications of proteins. In each case, eggs microinjected with the mAb 4C11, which also binds to the IP3 receptor but does not inhibit IP3-induced Ca2+ release, had no inhibitory effect on fertilization and egg activation. Results of these studies suggest that IP3-mediated Ca2+ release is essential for both early and late events of mouse egg activation.
Topographic specificity of corticospinal connections formed in explant coculture
Authors: Kuang Rong Zhen , Merline Michael , Kalil Katherine 
Published: April 2021

ABSTRACT
The corticospinal pathway connects layer V pyramidal neurons in discrete regions of the sensorimotor cortex to topographically matching targets in the spinal cord. In rodents initial pathway errors occur transiently during early postnatal development, such that visual cortical axons project inappropriately into the corticospinal tract. Nevertheless, only sensorimotor axons form corticospinal connections, which are topographically ordered in hamsters from the earliest stages of innervation. Previous work in vivo suggests that pathfinding is carried out by primary cortical axons whereas target innervation occurs by extension of axon collaterals at appropriate locations. In vitro studies have provided evidence that chemotropic factors may selectively attract extension of neurites into specific targets. To investigate the basis for corticospinal target selection during development, we have used an in vitro explant coculture system. Sensorimotor and visual cortical explants from newborn hamsters were presented with inappropriate targets from olfactory bulb and cerebellum and targets from the cervical (forelimb) and lumbar (hindlimb) enlargements of the early postnatal spinal cord. Under in vitro conditions, corticospinal target selection was highly specific and remarkably similar to corticospinal connectivity in vivo. Visual and sensorimotor cortical neurites extended nonselectively into the white matter of the spinal cord. However, only neurites from the sensorimotor cortex were able to extend into and arborize within the spinal gray. In the majority of cases, these connections were topographically appropriate, matching forelimb cortex to cervical cord and hindlimb cortex to lumbar cord. However, we found no evidence that chemotropic attraction was responsible for selection of appropriate targets by cortical neurites or that spinal target tissue promoted extension of cortical axon collaterals within the collagen matrix. These results suggest that the ability of cortical neurites to recognize correct spinal targets and form terminal arbors may require direct axon target interaction.
Retinoic acid promotes differentiation of photoreceptors in vitro
Authors: Kelley Matthew W. , Turner Jennifer K. , Reh Thomas A. 
Published: April 2021

ABSTRACT
The results of several recent studies have demonstrated that cell commitment and differentiation in the developing vertebrate retina are influenced by cell-cell interactions within the microenvironment. Retinoic acid has been shown to influence cell fates during development of the nervous system, and retinoic acid has been detected in the embryonic retina. To determine whether retinoic acid mediates the differentiation of specific neuronal phenotypes during retinal histogenesis, we treated dissociated cell cultures of embryonic and neonatal rat retina with varying concentrations of all-trans or 9-cis retinoic acid and analyzed the effects on cell fate using neuron and photoreceptor-specific antibodies. Addition of exogenous retinoic acid caused a dose-dependent, specific increase in the number of cells that developed as photoreceptors in culture throughout the period of retinal neurogenesis. In the same cultures, retinoic acid also caused a dose-dependent decrease in the number of cells that developed as amacrine cells. Also, results of double-labeled immunohistochemical studies using bromodeoxyuridine demonstrated that the primary effect of retinoic acid was to influence progenitor cells to develop as newly generated rod photoreceptors. Since retinoic acid and at least one of the retinoic acid receptors (RARα) have been localized to the developing neural retina, these results suggest that retinoic acid may play a role in the normal development of photoreceptor cells in vivo.
Early event in maize leaf epidermis formation as revealed by cell lineage studies
Authors: Cerioli Sergio , Marocco Adriano , Maddaloni Massimo , Motto Mario , Salamini Francesco 
Published: April 2021

ABSTRACT
The epidermal cells of the juvenile leaves of maize are covered by a wax layer. glossy mutants are known which reduce drastically wax deposition. We have used the somatically unstable glossy-1 mutable 8 allele to study the distribution on the epidermis of spontaneous revertant sectors of wild-type tissues. Sectors tend to start and end at positions that correlate with the location on the epidermis of the long costal cells of ribs. It is concluded that in the protoderm only a few cells have a role and position in the generation of each of the developmental modules located between leaf midrib and margin. The module consists of an epidermal strip of cells bordered by two lateral ribs. The module originates from at least 4 cells, with one cell being the progenitor of the other three. Data are provided describing the mode of longitudinal anticlinal epidermal cell divisions within the module that are responsible for the increase in leaf width. The results suggest the existence of a clonal type of development during early leaf epidermis formation.
Expression of baculovirus P35 prevents cell death in Drosophila
Authors: Hay Bruce A. , Wolff Tanya , Rubin Gerald M. 
Published: April 2021

ABSTRACT
The baculovirus P35 protein functions to prevent apoptotic death of infected cells. We have expressed P35 in the developing embryo and eye of the fly Drosophila melanogaster. P35 eliminates most, if not all, normally occurring cell death in these tissues, as well as X-irradiation-induced death. Excess pupal eye cells that are normally eliminated by apoptosis develop into pigment cells when their death is prevented by P35 expression. Our results suggest that one mechanism by which viruses prevent the death of the host cell is to block a cell death pathway that mediates normally occurring cell death. Identification of molecules that interact biochemically or genetically with P35 in Drosophila should provide important insights into how cell death is regulated.