bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neurotrophins affect the pattern of DRG neurite growth in a bioassay that presents a choice of CNS and PNS substrates
Authors: Tuttle Rebecca , Matthew William D. 
Published: April 2021

ABSTRACT
Neurons can be categorized in terms of where their axons project: within the central nervous system, within the peripheral nervous system, or through both central and peripheral environments. Examples of these categories are cerebellar neurons, sympathetic neurons, and dorsal root ganglion (DRG) neurons, respectively. When explants containing one type of neuron were placed between cryosections of neonatal or adult sciatic nerve and neonatal spinal cord, the neurites exhibited a strong preference for the substrates that they would normally encounter in vivo: cerebellar neurites generally extended only on spinal cord, sympathetic neurites on sciatic nerve, and DRG neurites on both.
Neurite growth from DRG neurons has been shown to be stimulated by neurotrophins. To determine whether neurotrophins might also affect the substrate preferences of neurites, DRG were placed between cryosections of neonatal spinal cord and adult sciatic nerve and cultured for 36 to 48 hours in the presence of various neurotrophins. While DRG cultured in NGF-containing media exhibited neurite growth over both spinal cord and sciatic nerve substrates, in the absence of neurotrophins DRG neurites were found almost exclusively on the CNS cryosection. To determine whether these neurotrophin-dependent neurite patterns resulted from the selective survival of subpopulations of DRG neurons with distinct neurite growth characteristics, a type of rescue experiment was performed: DRG cultured in neurotrophin-free medium were fed with NGFcontaining medium after 36 hours in vitro and neurite growth examined 24 hours later; most DRG exhibited extensive neurite growth on both peripheral and central nervous system substrates. This experiment demonstrates that the observed neurite growth preferences are due to a nontrophic effect of NGF.
Unlike DRG cultured in NGF, those cultured in the presence of either NT-3 or BDNF often exhibited neurite growth preferences for the spinal cord cryosections; the effect was strongest in cultures containing NT-3. In addition, while a mixture of insulin, transferrin and selenium (ITS) did not by itself have a detectable effect on neurite growth, it dramatically potentiated both BDNFand NT-3-stimulated neurite growth. However, ITS had no obvious effect on NGF-stimulated neurite growth.
The Drosophila E74 gene is required for metamorphosis and plays a role in the polytene chromosome puffing response to ecdysone
Authors: Fletcher Jennifer C. , Burtis Kenneth C. , Hogness David S. , Thummel Carl S. 
Published: April 2021

ABSTRACT
The steroid hormone ecdysone initiates Drosophila metamorphosis by reprogramming gene expression during late larval and prepupal development. The ecdysone-inducible gene E74, a member of the ets proto-oncogene family, has been proposed to play a key role in this process. E74 is encoded within the 74EF early puff and consists of two overlapping transcription units, E74A and E74B. To assess the function(s) of E74 during metamorphosis, we have isolated and characterized recessive loss-of-function mutations specific to each transcription unit. We find that mutations in E74A and E74B are predominantly lethal during prepupal and pupal development, consistent with a critical role for their gene products in metamorphosis. Phenotypic analysis reveals that E74 function is required for both pupariation and pupation, and for the metamorphosis of both larval and imaginal tissues. E74B mutants are defective in puparium formation and head eversion and die as prepupae or cryptocephalic pupae, while E74A mutants pupariate normally and die either as prepupae or pharate adults. We have also investigated the effects of the E74 mutations on gene expression by examining the puffing pattern of the salivary gland polytene chromosomes in newly formed mutant prepupae. Most puffs are only modestly affected by the E74B mutation, whereas a subset of late puffs are sub-maximally induced in E74A mutant prepupae. These observations are consistent with Ashburner’s proposal that early puff proteins induce the formation of late puffs, and define E74A as a regulator of late puff activity. They also demonstrate that E74 plays a wide role in reshaping the insect during metamorphosis, affecting tissues other than the salivary gland in which it was originally identified.
Sulphated proteoglycan is required for collecting duct growth and branching but not nephron formation during kidney development
Authors: Davies Jamie , Lyon Malcolm , Gallagher John , Garrod David 
Published: April 2021

ABSTRACT
Kidney epithelia have separate origins; collecting ducts develop by ureteric bud growth and arborisation, nephrons by induced mesenchyme-epithelium transition. Both express sulphated glycosaminoglycans (GAGs) which are strikingly upregulated during nephron differentiation. However, sodium chlorate, an inhibitor of GAG sulphation, and the GAG-degrading enzymes heparitinase plus chondroitinase, did not prevent nephron development. In contrast, ureteric bud growth and branching were reversibly inhibited by the above reagents, the inhibition correlating quantitatively with sulphated GAG deprivation caused by a range of chlorate concentrations. Growth and branching could be independently restored during GAG deprivation by hepatocyte growth factor and phorbol-12myristate acetate (PMA) respectively. Together these signalling effectors stimulated both branch initiation and growth. Thus growth and morphogenesis of ureteric bud involve distinct signalling pathways both regulated by GAGs.
Expression of Sry, the mouse sex determining gene
Authors: Hacker Adam , Capel Blanche , Goodfellow Peter , Lovell-Badge Robin 
Published: April 2021

ABSTRACT
In the mouse, Sry is expressed by germ cells in the adult testis and by somatic cells in the genital ridge. Transcripts in the former exist as circular RNA molecules of 1.23 kb, which are unlikely to be efficiently translated. We have used RNase protection to map the extent of the less abundant Sry transcript in the developing gonad. We demonstrate that it is a linear mRNA derived from a single exon. This begins in the unique region 5′ of the protein coding region and extends several kilobases into the 3′ arm of the large inverted repeat which bounds the Sry genomic locus. Knowledge of this transcript, which is very different from that of the human SRY gene, allows us to predict its protein product and reveals several features which may be involved in translational control. Our data is also consistent with there being two promoters for the Sry gene, a proximal one that gives functional transcripts in the genital ridge and a distal promoter used in germ cells in the adult testis. As RNase protection is a quantitative technique, a detailed timecourse of Sry expression was carried out using accurately staged samples. Sry transcripts are first detectable just after 10.5 days post coitum, they reach a peak at 11.5 days and then decline sharply so that none are detected 24 hours later. This was compared with antiMüllerian hormone gene expression, an early marker of Sertoli cells and the first known downstream gene of Sry. Amh expression begins 20 hours after the onset of Sry expression at a time when Sry transcripts are at their peak. While this result does not prove a direct interaction between the two genes, it defines the critical period during which Sry must act to initiate Sertoli cell differentiation.
Dorsalizing and neuralizing properties of Xdsh, a maternally expressed Xenopus homolog of dishevelled
Authors: Sokol Sergei Y. , Klingensmith John , Perrimon Norbert , Itoh Keiji 
Published: April 2021

ABSTRACT
Signaling factors of the Wnt proto-oncogene family are implicated in dorsal axis formation during vertebrate development, but the molecular mechanism of this process is not known. Studies in Drosophila have indicated that the dishevelled gene product is required for wingless (Wnt1 homolog) signal transduction. We demonstrate that injection of mRNA encoding a Xenopus homolog of dishevelled (Xdsh) into prospective ventral mesodermal cells triggers a complete dorsal axis formation in Xenopus embryos. Lineage tracing experiments show that cells derived from the injected blastomere contribute to anterior and dorsal structures of the induced axis. In contrast to its effect on mesoderm, overexpression of Xdsh mRNA in prospective ectodermal cells triggers anterior neural tissue differentiation. These studies suggest that Wnt signal transduction pathway is conserved between Drosophila and vertebrates and point to a role for maternal Xdsh product in dorsal axis formation and in neural induction.
Chicken B cells undergo discrete developmental changes in surface carbohydrate structure that appear to play a role in directing lymphocyte migration during embryogenesis
Authors: Masteller Emma L. , Larsen Robert D. , Carlson Louise M. , Pickel James M. , Nickoloff Brian , Lowe John , Thompson Craig B. , Lee Kelvin P. 
Published: April 2021

ABSTRACT
The migration of progenitor cells to specific microenviron ments is essential for the development of complex organisms. Avian species possess a unique primary lymphoid organ, the bursa of Fabricius, that plays a central role in the development of B cells. B cell progenitors, however, arise outside the bursa of Fabricius and, during embryonic development, must migrate through the vasculature to the bursa of Fabricius. In this report, we demonstrate that these progenitor B cells express the sialyl Lewis x carbohydrate structure previously shown to be a ligand for the selectin family of vascular adhesion receptors. Soon after migration to the bursa of Fabricius, B cell progenitors are induced to undergo a developmental switch and terminate the expression of sialyl Lewis x in a temporal pattern that correlates with the developmental decline in the ability of these cells to home to the bursa of Fabricius upon transplantation. The induction of the devel opmental switch in the glycosylation pattern of developing B cells requires the bursal environment. In addition, sialyl Lewis x carbohydrate determinants or structurally similar determinants on the surface of immortalized bursal lymphoid stem cells participate in the adherence of these cells to the vascular regions of the bursal microenvironment. These data demonstrate that the carbohydrate structure sialyl Lewis x is developmentally regulated during chicken B cell development and may facilitate the migration of B cell progenitors to the bursal microenvironment by serving as a ligand for a lectin-like adhesion receptor.
polyhomeotic appears to be a target of Engrailed regulation in Drosophila
Authors: Serrano Nuria , Brock Hugh W. , Demeret Caroline , Dura Jean-Maurice , Randsholt Neel B. , Kornberg Thomas B. , Maschat Florence 
Published: April 2021

ABSTRACT
In Drosophila, Engrailed is a nuclear regulatory protein with essential roles in embryonic segmentation and in normal development of posterior compartments. One of its regulatory targets appears to be polyhomeotic (ph), a Polycomb group gene. We observed, by immunostaining, that Engrailed protein binds to the site of the polyhomeotic locus in region 2D of polytene chromosomes. The same analysis carried out on a transgenic line containing one copy of a P(ph-lacZ) construct shows an additional Engrailed-binding site at the location of the insert. In vivo, polyhomeotic depends on engrailed function in germ-band-elongated embryos, when engrailed and polyhomeotic genes are expressed in similar patterns. By in vitro immunoprecipitations and gel shift assays, we identified two classes of high affinity Engrailed-binding sites upstream of each of the two polyhomeotic transcription units. DNA fragments containing these sites were also immunoprecipitated from embryonic UV crosslinked chromatin in presence of anti-Engrailed antibody. These results suggest that poly-homeotic activation in germ-band-elongated embryos could be mediated by Engrailed-binding to these sites.
Zebrafish wnt8 and wnt8b share a common activity but are involved in distinct developmental pathways
Authors: Kelly Gregory M. , Greenstein Penny , Erezyilmaz Deniz F. , Moon Randall T. 
Published: April 2021

ABSTRACT
The specification of the vertebrate body plan is dependent on numerous signaling molecules, including members of the Wnt family. We have identified two zebrafish wnt8 paralogs related to Xwnt-8B and Xwnt-8, respectively. A RT-PCR assay demonstrated that wnt8 is expressed maternally, with transcripts detected throughout embryogenesis, whereas wnt8b transcripts were first detected during late gastrulation. The wnt8 transcripts at 50% epiboly are spatially restricted to those cells at the blastoderm margin, overlying gsc-expressing cells in the axial hypoblast. During late gastrulation, wnt8 was no longer detected in the marginal cells at the dorsal midline and by mid-segmentation, transcripts were found in the presumptive tail bud. In contrast, wnt8b expression is spatially restricted to prospective neuroepithelium, and later to neural-specific structures. Overexpression of both wnts results in two major phenotypes: radialized embryos and embryos with anterior defects. These phenotypes were preceded by significant changes in the spatial expression patterns of gsc and ntl transcripts, reminiscent of activities of Xwnt-8 in Xenopus, and consistent with a role for wnt8 in the specification or patterning of mesoderm.
Progenitor cells of the adult human airway involved in submucosal gland development
Authors: Engelhardt John F. , Schlossberg Howard , Yankaskas James R. , Dudus Lorita 
Published: April 2021

ABSTRACT
A bronchial xenograft model of the human airway was used to identify submucosal gland progenitor cells within the surface airway epithelium. Lineage analysis using recombinant retroviruses has demonstrated considerable diversity in the cellular composition of expanded clones within reconstituted xenograft airway epithelium. These findings provide evidence for the existence of multiple progenitors in the airway with either limited or pluripotent capacity for differentiation. Furthermore, the development of transgene-expressing submucosal glands was associated with a single subset of surface airway epithelial clones. This gland progenitor cell demonstrated two discernible characteristics consistent with the identification of an airway stem cell including: (1) pluripotent capacity for airway differentiation and (2) a two-fold higher proliferative rate than other observed clone types. The number of progenitor cells involved in gland development was also assessed by clonal analysis using alkaline phosphatase and β-galactosidase transgenes. These studies demonstrated that more than one airway progenitor cell is involved in the initial stages of gland development. A second explanation for the high prevalence of non-clonality in developing glands was suggested from three-dimensional reconstruction of transgene marked glands. These reconstruction experiments demonstrated that 27% of glands contained more than one duct to the surface airway epithelium. This observation suggests a novel mechanism of gland morphogenesis by which independently formed glands interact to join glandular lumens. Such a mechanism of glandular development and morphogenesis may play an important role in normal submucosal gland development and/or the progression of hypersecretory diseases of the adult human airway as seen in cystic fibrosis, chronic bronchitis and asthma. The identification of progenitor cells with the capacity to form submucosal glands has implications on the targets for gene therapy in cystic fibrosis.
A functional analysis of 5′, intronic and promoter regions of the homeotic gene proboscipedia in Drosophila melanogaster
Authors: Kapoun Ann M. , Kaufman Thomas C. 
Published: April 2021

ABSTRACT
In Drosophila, the homeotic gene proboscipedia (pb) is required for the formation of the adult mouthparts. To determine the functional significance of putative pb regulatory DNA, we have performed an in vivo analysis of sequences upstream of and within pb using a series of minigenes. Additionally, we have initiated a dissection of pb’s promoter and enhancer elements using lacZ reporter gene constructs. Our results establish that a conserved region located in the second intron is essential for proper formation of the adult mouthparts. A 0.5 kb fragment from this region was shown to direct lacZ expression in a pb pattern in both embryos and third instar labial discs when combined with a 600 bp pb basal promoter sequence. A 32 bp element contained within the 0.5 kb region functions as a labial disc enhancer for pb. Surprisingly, the conserved second intron pb enhancers do not function properly with a heterologous hsp70 promoter, suggesting that promoter-specific interactions occur at the pb locus. We also found redundant and cryptic enhancers in the large introns of pb that are not required for pb function. Finally, we demonstrate that the pb transcription unit does not require sequences upstream of −98 bp to provide pb function in the labial discs. Rather, pb’s upstream DNA appears to contain negative regulatory DNA required for silencing PB accumulation in inappropriate domains of third instar imaginal discs. Thus, we have defined many of pb’s cis-controlling sequences to an experimentally manageable size, thereby making this an attractive system for the discovery of trans-acting proteins and, consequently, for elucidating the mechanisms of homeotic gene regulation.
Duels without obvious sense: counteracting inductions involved in body wall muscle development in the Caenorhabditis elegans embryo
Authors: Schnabel Ralf 
Published: April 2021

ABSTRACT
During the first four cleavage rounds of the Caenorhabdi- tis elegans embryo, five somatic founder cells AB, MS, E, C and D are born, which later form the tissues of the embryo. The classical criterion for a cell-autonomous specification of a tissue is the capability of primordial cells to produce this tissue in isolation from the remainder of the embryo. By this criterion, the somatic founder cells MS, C and D develop cell-autonomously. Laser ablation experiments, however, reveal that within the embryonic context these blastomeres form a network of duelling cellular interactions.
During normal development, the blastomere D inhibits muscle specification in the MS and the C lineage inhibits muscle specification in the D lineage. These inhibitory interactions are counteracted by two activating inductions. As described before the inhibition of body wall muscle in MS is counteracted by an activating signal from the ABa lineage. Body wall muscle in the D lineage is induced by MS descendants, which suppress an inhibitory activity of the C lineage. The interaction between the D and the MS lineage occurs through the C lineage. An interesting feature of these cell-cell interactions is that they do not serve to dis- criminate between equivalent cells but are permissive or nonpermissive inductions.
No evidence was found that the C-derived body wall muscle also depends on an induction, which suggests that possibly three different pathways coexist in the early embryo to specify body wall muscle, two of which are, in different ways, influenced by cell-cell interactions and a third that is autonomous.
This work supplies evidence that cells may acquire transient states during embryogenesis that influence the specification of other cells in the embryo. These states, however, may not be reflected in the developmental potentials of the cells themselves. They can only be scored indi- rectly by their action on the specification of other cells in the embryo.
Blastomeres that behave cell-autonomously in isolation are nevertheless subjected to cell-cell interactions in the embryonic context. Why this should be is an intriguing question. The classical notion has been that blastomeres are specified autonomously in nematodes. In recent years, it was established that at least five inductions are required to determine the AB descendants of C. elegans, whereas the P1 descendants have been typically viewed to develop more autonomously. It appears now that inductions also play a major role during the determination of P1-derived blastomeres.
Sequential organizing activities of engrailed, hedgehog and decapentaplegic in the Drosophila wing
Authors: Zecca Myriam , Basler Konrad , Struhl Gary 
Published: April 2021

ABSTRACT
The Drosophila wing is formed by two cell populations, the anterior and posterior compartments, which are distin- guished by the activity of the selector gene engrailed (en) in posterior cells. Here, we show that en governs growth and patterning in both compartments by controlling the expression of the secreted proteins hedgehog (hh) and decapentaplegic (dpp) as well as the response of cells to these signaling molecules. First, we demonstrate that en activity programs wing cells to express hh whereas the absence of en activity programs them to respond to hh by expressing dpp. As a consequence, posterior cells secrete hh and induce a stripe of neighboring anterior cells across the compartment boundary to secrete dpp. Second, we demonstrate that dpp can exert a long-range organizing influence on surrounding wing tissue, specifying anterior or posterior pattern depending on the compartmental provenance, and hence the state of en activity, of the responding cells. Thus, dpp secreted by anterior cells along the compartment boundary has the capacity to organize the development of both compartments. Finally, we report evidence suggesting that dpp may exert its organizing influence by acting as a gradient morphogen in contrast to hh which appears to act principally as a short range inducer of dpp.
Versican is selectively expressed in embryonic tissues that act as barriers to neural crest cell migration and axon outgrowth
Authors: Landolt Reto M. , Vaughan Lloyd , Winterhalter Kaspar H. , Zimmermann Dieter R. 
Published: April 2021

ABSTRACT
Chondroitin sulfate proteoglycans have been implicated in the regulation of cell migration and pattern formation in the developing peripheral nervous system. To identify whether the large aggregating proteoglycan versican might be mediating these processes, we prepared monospecific antibodies against a recombinant core protein fragment of chick versican. The purified antibodies recognize the pre-dominant versican splice-variants V0 and V1. Using these antibodies, we revealed a close correlation between the spacio-temporal expression of versican and the formation of molecular boundaries flanking or transiently blocking the migration pathways of neural crest cells or motor and sensory axons. Versican is present in the caudal sclerotome, the early dorsolateral tissue underneath the ectoderm, the pelvic girdle precursor and to a certain extent in the perinotochordal mesenchyme. Versican is completely absent from tissues invaded by neural crest cells and extending axons. Upon completion of neural crest cell migration and axon outgrowth, versican expression is shifted to pre-chondrogenic areas. Since versican inhibits cellular interactions with fibronectin, laminin and collagen I in vitro, the selective expression of versican within barrier tissues may be linked to a functional role of versican in the guidance of migratory neural crest cells and outgrowing axons.