bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sensory ganglia require neurotrophin-3 early in development
Authors: Gaese Franziska , Kolbeck Roland , Barde Yves-Alain 
Published: April 2021

ABSTRACT
The role played by neurotrophin-3 during the development of quail sensory ganglia was investigated using a mono-clonal antibody that specifically blocks the biological activity of this neurotrophin. Neutralisation of neu-rotrophin-3 was initiated during completion of gangliogen-esis. Neuronal cell counts indicate that about 30% of the neurons normally present in either the placode-derived ganglion nodosum or in a leg-innervating, neural crest-derived dorsal root ganglion are eliminated by the antibody treatment. In both ganglia, this reduction is seen early in development, and the results obtained with the ganglion nodosum indicate that neurotrophin-3 plays an essential role already during gangliogenesis. Neuronal numbers are also compared with those obtained after treatment with a monoclonal antibody to nerve growth factor, used either alone or in combination with the neurotrophin-3 antibody.
Expression and methylation of imprinted genes during in vitro differentiation of mouse parthenogenetic and androgenetic embryonic stem cell lines
Authors: Szabó Piroska , Mann Jeff R. 
Published: April 2021

ABSTRACT
Messenger RNA and methylation levels of four imprinted genes, H19, Igf2r, Igf-2 and Snrpn were examined by northern and Southern blotting in mouse parthenogenetic, androgenetic and normal or wild-type embryonic stem cell lines during their differentiation in vitro as embryoid bodies. In most instances, mRNA levels in parthenogenetic and androgenetic embryoid bodies differed from wild type as expected from previously determined patterns of monoallelic expression in midgestation embryos and at later stages of development. These findings implicate aberrant mRNA levels of these genes in the abnormal development of parthenogenetic and androgenetic embryos and chimeras. Whereas complete silence of one of the parental alleles has previously been observed in vivo, we detected some mRNA in the corresponding embryonic stem cell line. This ‘leakage’ phenomenon could be explained by partial erasure, bypass or override of imprints, or could represent the actual activity status at very early stages of development. The mRNA levels of H19, Igf2r and Igf-2 and the degree of methylation at specific associated sequences were correlated according to previous studies in embryos, and thereby are consistent with suggestions that the methylation might play a role in controlling transcription of these genes. Paternal-specific methylation of the H19 promoter region is absent in sperm, yet we observed its presence in undifferentiated androgenetic embryonic stem cells, or before the potential expression phase of this gene in embryoid bodies. As such methylation is likely to invoke a repressive effect, this finding raises the possibility that it is part of the imprinting mechanism of H19, taking the form of a secondary imprint or postfertilization epigenetic modification necessary for repression of the paternal allele.
wingless acts through the shaggy/zeste-white 3 kinase to direct dorsal-ventral axis formation in the Drosophila leg
Authors: Diaz-Benjumea Fernando J. , Cohen Stephen M. 
Published: April 2021

ABSTRACT
The secreted glycoproteins encoded by Wnt genes are thought to function as intercellular signaling molecules which convey positional information. Localized expression of Wingless protein is required to specify the fate of ventral cells in the developing Drosophila leg. We report here that Wingless acts through inactivation of the shaggy/zeste white 3 protein kinase to specify ventral cell fate in the leg. Ectopic expression of Wingless outside its normal ventral domain has been shown reorganize the dorsal-ventral axis of the leg in a non-autonomous manner. Using genetic mosaics, we show that cells that lack shaggy/zeste white 3 activity can influence the fate of neighboring cells to reo-r ganize dorsal-ventral pattern in the leg, in the same manner as Wingless-expressing cells. Therefore, clones of cells that lack shaggy/zeste white 3activity exhibit all of the organizer activity previously attributed to Wingless-expressing cells, but do so without expressingwingless. We also show that the organizing activity of ventral cells depends upon the location of the clone along the dorsalventral axis. These findings suggest that Wingless protein does not function as a morphogen in the dorsal-ventral axis of the leg.
Pleiotropic effects of the mouse lethal yellow (A
y) mutation explained by deletion of a maternally expressed gene and the simultaneous production of agouti fusion RNAs
Authors: Duhl David M. J. , Stevens Mary E. , Vrieling Harry , Saxon Paul J. , Miller Miles W. , Epstein Charles J. , Barsh Gregory S. 
Published: April 2021

ABSTRACT
Heterozygosity for the mouse lethal yellow(Ay) mutation leads to obesity, increased tumor susceptibility and increased activity of the agouti coat color gene; homozygosity for Ay results in embryonic death around the time of implantation. Although these pleiotropic effects have not been separated by recombination, previous studies have suggested that the dominant and recessive effects result from distinct genetic lesions. Here we use a combination of genomic and cDNA cloning experiments to demonstrate that the Ay mutation is caused by a 120 kb deletion which lies centromere-proximal to the agouti coat color gene. The deletion removes coding but not 5′ untranslated sequences for a ubiquitously expressed gene predicted to encode a protein similar in sequence to an RNA-binding protein, which we named Merc, for maternally expressed hnRNP C-related gene, but have renamed Raly, since the gene is nearly identical to one reported recently by Michaud et al. (Gene Dev. 7, 1203-1213, 1993). The Ay deletion results in the splicing of Merc/Raly 5′ untranslated sequences to agouti protein-coding sequences, which suggests that ectopic expression of the normal agouti protein by the Ay fusion RNA is responsible for the pleiotropic effects associated with heterozygosity for Ay.
We find that Merc/Raly RNA is present in the unfertilized egg and is also transcribed in preimplantation embryos. Using a PCR-based assay to determine the genotype of individual embryos from an Ay/a × Ay/a intercross, we show that, in the absence of zygoticMerc/Raly expression, Ay/Ay embryos develop to the blastocyst stage, but do not hatch from the zona pellucida or form trophoblastic outgrowths. Injection of a Merc/Raly antisense oligonucleotide into non-mutant embryos blocks development prior to the blastocyst stage, and can be rescued by coinjection of a Merc/Raly transgene. These results suggest that maternal expression of Merc/Raly plays an important role in preimplantation development and that its deletion of is sufficient to explainAy-associated embryonic lethality.
Bacterial symbionts induce host organ morphogenesis during early postembryonic development of the squid Euprymna scolopes
Authors: Montgomery Mary K. , McFall-Ngai Margaret 
Published: April 2021

ABSTRACT
The mutualistic association between the squid Euprymna scolopes and the bacterium Vibrio fischeri is an emerging experimental system for the study of the influence of bacteria on animal development. Taking advantage of the ability to raise both this host and its microbial partner independently under laboratory conditions, we describe the effects of bacterial interactions on morphogenesis of the juvenile host symbiotic organ. Our results show that bacteria are essential for normal postembryonic development of the symbiotic organ, which involves changes in both the surface epithelium and the epithelial tissue within the organ where the bacterial culture will take up residence. Cell death induced by exposure to symbiotic V. fischeri results in the regression of a complex ciliated surface epithelium, a tissue that apparently functions to facilitate inoculation of the juvenile organ with the appropriate specific bacterial species. Regression of this tissue begins within hours of exposure to symbiosis-competent bacteria and progresses over the next 5 days, at which time full regression is complete, resulting in a symbiotic organ whose epithelial surface resembles that of the fully mature organ. Moreover, symbiosis-competent bacteria induce modification of the epithelial cells of the crypts that will house these symbionts; these cells undergo significant changes in shape and size in response to interactions with symbiotic V. fischeri. In contrast, we find that when these tissues are not exposed to the proper bacterial symbionts they remain in a state of arrested morphogenesis, a condition that can be rescued by interactions with symbionts. The results of these studies are the first experimental data demonstrating that a specific bacterial symbiont can play an inductive role in animal development.
Rhombomere rotation reveals that multiple mechanisms contribute to the segmental pattern of hindbrain neural crest migration
Authors: Sechrist John , Scherson Talma , Bronner-Fraser Marianne 
Published: April 2021

ABSTRACT
Hindbrain neural crest cells adjacent to rhombomeres 2 (r2), r4 and r6 migrate in a segmental pattern, toward the first, second and third branchial arches, respectively. Although all rhombomeres generate neural crest cells, those arising from r3 and r5 deviate rostrally and caudally (J. Sechrist, G. Serbedzija, T. Scherson, S. Fraser and M. Bronner-Fraser (1993) Development 118, 691-703). We have altered the rostrocaudal positions of the cranial neural tube, adjacent ectoderm/mesoderm or presumptive otic vesicle to examine tissue influences on this segmental migratory pattern. After neural tube rotation, labeled neural crest cells follow pathways generally appropriate for their new position after grafting. For example, when r3 and r4 were transposed, labeled r3 cells migrated laterally to the second branchial arch whereas labeled r4 cells primarily deviated caudally toward the second arch, with some cells moving rostrally toward the first. In contrast to r4 neural crest cells, transposed r3 cells leave the neural tube surface in a polarized manner, near the r3/4 border. Surprisingly, some labeled neural crest cells moved directionally toward small ectopic otic vesicles that often formed in the ectoderm adjacent to grafted r4. Similarly, they moved toward grafted or displaced otic vesicles. In contrast, surgical manipulation of the mesoderm adjacent to r3 and r4 had no apparent effects. Our results offer evidence that neural crest cells migrate directionally toward the otic vesicle, either by selective attraction or pathway-derived cues.
Separate pathways for synapse-specific and electrical activity-dependent gene expression in skeletal muscle
Authors: Tang Jicheng , Jo Sangmee Ahn , Burden Steven J. 
Published: April 2021

ABSTRACT
Signaling between nerve and muscle is mediated by multiple mechanisms, including two transcriptional pathways. Signals provided by the nerve terminal activate transcription of acetylcholine receptor (AChR) genes in myofiber nuclei near the synaptic site, and signals associated with myofiber electrical activity inactivate AChR gene expression throughout the myofiber. These opposing effects of innervation are conferred by 1.8 kb of 5′ flanking DNA from the AChR δ subunit gene. These results raise the possibility that synapse-specific and electrical activity-dependent gene expression are mediated by the same DNA sequence and that activation and repression are determined by differential regulation of the same DNA binding protein. We produced transgenic mice carrying AChR δ subunit-hGH gene fusions, and we show here that a binding site (E-box) for myogenic basic helix-loop-helix proteins is required for electrical activity-dependent but not for synapse-specific gene expression of the δ subunit gene. These results indicate that a change in the expression or activity of an E-box binding protein(s) mediates electrical activity-dependent gene regulation and that synapse-specific and electrical activity-dependent gene expression require different DNA sequences. Moreover, we show here that the cis-acting elements for both aspects of innervation-dependent gene regulation are contained in 181 bp of 5′ flanking DNA from the AChR δ subunit gene.
The role of apterous in the control of dorsoventral compartmentalization and PS integrin gene expression in the developing wing of Drosophila
Authors: Blair Seth S. , Brower Danny L. , Thomas John B. , Zavortink Michael 
Published: April 2021

ABSTRACT
During the development of Drosophila appendages from imaginal discs lineage restrictions appear that prevent dividing cells from crossing between regionally distinct compartments. These compartments correspond not only to regions of cell lineage restrictions but also to regions of specific gene expression. When compartments were first discovered, it was proposed that their formation relied on compartment-specific ‘selector’ gene activity; engrailed is thought to play such a role for the early-arising anteriorposterior restriction. Recent results suggest that the dorsally expressed transcription factor encoded by apterous may control dorsoventral identity in the wing. In this study we use mosaic analysis to show that apterous maintains the late-arising dorsoventral lineage restriction in a manner that strongly supports the selector gene hypothesis: loss of apterous function from dorsal cells after the formation of the boundary causes them to cross into the ventral compartment. Moreover, we show that apterous plays a role controlling patterns of gene expression in the developing wing disc. The PS1 and PS2 integrins are normally expressed in primarily dorsal-specific and ventral-specific patterns, respectively. We show that ectopic expression of apterous induces ectopic ventral expression of PS1 integrin and αPS1 mRNA, while loss of apterous can induce the ectopic dorsal expression of PS2 integrin. Thus, apterous plays a selector-like role both in terms of the control of lineage restrictions and the regulation of downstream gene expression.
Embryonic origin of hemocytes and their relationship to cell death in Drosophila
Authors: Tepass Ulrich , Fessler Liselotte I. , Aziz Amina , Hartenstein Volker 
Published: April 2021

ABSTRACT
We have studied the embryonic development of Drosophila hemocytes and their conversion into macrophages. Hemocytes derive exclusively from the mesoderm of the head and disperse along several invariant migratory paths throughout the embryo. The origin of hemocytes from the head mesoderm is further supported by the finding that in Bicaudal D, a mutation that lacks all head structures, and in twist snail double mutants, where no mesoderm develops, hemocytes do not form. All embryonic hemocytes behave like a homogenous population with respect to their potential for phagocytosis. Thus, in the wild type, about 80-90% of hemocytes become macrophages during late development.
In mutations with an increased amount of cell death (knirps; stardust; fork head), this figure approaches 100%. In contrast, in these mutations, the absolute number of hemocytes does not differ from that in wild type, indicating that cell death does not ‘induce’ the formation of hemocytes. Finally, we show that, in the Drosophila embryo, apoptosis can occur independently of macrophages, since mutations lacking macrophages (Bicaudal D; twist snail double mutants; torso4021) show Abundant cell death.
Transitional cells in the regenerating pancreas
Authors: Gu Danling , Lee Myung-Shik , Krahl Troy , Sarvetnick Nora 
Published: April 2021

ABSTRACT
We examined the spectrum of intermediate cell types in the regenerating pancreas as duct epithelial cells progressed through their differentiation pathway to become mature endocrine cells. The model used was transgenic mice in which the pancreatic islets continue to grow during adulthood, unlike normal mice whose islet cell formation ceases early in life. Because the intermediate cells migrated into islet-like clusters at specific locations, we propose a specific pathway for islet development. Endocrine cells are derived from duct cells co-expressing a duct cell antigen, carbonic anhydrase II (CA II) and an exocrine enzyme, amylase. The CA II/amylase cells become amylase/endocrine intermediate cells as they exited from their lumenal location. The abluminal amylase/endocrine cells continue to differentiate to multihormone-bearing young endocrine cells, which migrated to form clusters with other differentiating endocrine cells.
A single frizzled protein has a dual function in tissue polarity
Authors: Krasnow Randi E. , Adler Paul N. 
Published: April 2021

ABSTRACT
The Drosophila frizzled (fz) gene is required for the development of normal tissue polarity in the epidermis. Genetic epistasis experiments argue that fz is at the top of a regulatory hierarchy that controls the subcellular site for prehair initiation within the cells of the pupal wing (Wong and Adler, 1993; J. Cell Biol. 123, 209-221). Genetic mosaic experiments indicate that fz has both cell autonomous and cell non-autonomous functions that are separately mutable (Vinson and Adler, 1987; Nature 329, 549-551). Two species of fz mRNA have been identified, raising the question as to whether the two functions are provided by a single protein or by two separate protein species. We generated transgenic flies that express each of these mRNAs under the control of an hsp70 promoter. Only one of the transgenes (hsfzI) showed any fz activity. At 29°C, the hsfzI transgene provided almost complete rescue of a null fz mutation, indicating that the protein encoded by this cDNA can fulfill both fz functions. Overexpression of the hsfzI transgene resulted in two distinct tissue polarity phenotypes depending on the time of heat shock.
The bithorax complex is regulated by trithorax earlier during Drosophila embryogenesis than is the Antennapedia complex, correlating with a bithorax-like expression pattern of distinct early trithorax transcripts
Authors: Sedkov Yurii , Tillib Sergei , Mizrokhi Lev , Mazo Alexander 
Published: April 2021

ABSTRACT
The trithorax gene is required throughout development to maintain expression of homeotic genes of the bithorax and Antennapedia complexes. We determined complete structures of maternal and zygotic alternatively spliced trithorax transcripts, and found that two RNA isoforms are expressed in a surprising manner in the early embryo. At syncytial blastoderm their expression is confined to the ventral region fated to become mesoderm. An additional broad domain of trithorax expression arises during cellularization and is quickly resolved into four pair-rule-like stripes in the posterior half of the embryo. This early expression pattern suggested the possibility that trithorax is involved in the very early regulation of homeotic genes expressed only in the posterior region of the embryo.
Indeed, transcription of bithorax complex genes in the mesoderm and ectoderm is altered in strong trithorax mutants during germ band elongation, while the anteriorly expressed Antennapedia complex genes are affected only at late stages of embryonic development. In addition, in another mutant allele (trxE3), expression of bithorax complex genes is normal, while expression of Antennapedia complex genes is reduced. These results suggest that proper expression of genes in the two homeotic complexes is maintained by products of different trithorax RNAs at different times of embryogenesis.
Role of mesenchymal nidogen for epithelial morphogenesis in vitro
Authors: Ekblom Peter , Ekblom Marja , Fecker Lothar , Klein Gerd , Zhang Hong-Yan , Kadoya Yuichi , Chu Mon-Li , Mayer Ulrike , Timpl Rupert 
Published: April 2021

ABSTRACT
Recent biochemical studies suggested that the extracellular matrix protein nidogen is a binding molecule linking together basement membrane components. We studied its expression and role during development. By immunofluorescence and northern blotting, nidogen was found early during epithelial cell development of kidney and lung. Yet, in situ hybridization revealed that nidogen was not produced by epithelium but by the adjacent mesenchyme in both organs. Binding of mesenchymal nidogen to epithelial laminin may thus be a key event during epithelial development. This is supported by antibody perturbation experiments. Antibodies against the nidogen binding site on laminin B2 chain perturbed epithelial development in vitro in embryonic kidney and lung. Mesenchymal nidogen could be important for early stages of epithelial morphogenesis.
The cloning of zebrin II reveals its identity with aldolase C
Authors: Ahn Andrew H. , Dziennis Suzan , Hawkes Richard , Herrup Karl 
Published: April 2021

ABSTRACT
The sagittal organization of the mammalian cerebellum can be observed at the anatomical, physiological and biochemical level. Previous screening of monoclonal antibodies produced in our laboratory has identified two intra-cellular antigens, zebrin I and II, that occur exclusively in adult cerebellar Purkinje cells. As their name suggests, the zebrin antibody staining of the Purkinje cell population is not uniform. Rather, zebrin-positive Purkinje cells are organized in stripes or bands that run from anterior to posterior across most of the cerebellum; interposed between the zebrin-positive cells are bands of Purkinje cells that are zebrin-negative. Comparison of the position of the antigenic bands with the anatomy of afferent projections suggests that the bands are congruent with the basic developmental and functional ‘compartments’ of the cerebellum. We report the isolation of cDNA clones of the 36×103Mr antigen, zebrin II, by screening of a mouse cerebellum cDNA expression library. Sequence analysis reveals a 98% identity between our clone and the glycolytic isozyme, aldolase C. In order to more rigorously demonstrate the identity of the two proteins, we stained adult cerebellum with an independent monoclonal antibody raised against aldolase C. Anti-aldolase staining occurs in a previously unreported pattern of sagittal bands of Purkinje cells; the pattern is identical to that revealed by the zebrin II mono-clonal. Further, in situ hybridization of antisense aldolase C riboprobe shows that the accumulation of zebrin II/aldolase C mRNA corresponds to the pattern of the zebrin antigen in Purkinje cells. Zebrin II/aldolase C gene expression is thus regulated at the level of transcription (or mRNA stability). In light of previous work that has demonstrated the cell-autonomous and developmentally regimented expression of zebrin II, further studies of the regulation of this gene may lead to insights about the determination of cerebellar compartmentation.
Transient localized accumulation of actin in Caenorhabditis elegans blastomeres with oriented asymmetric divisions
Authors: Waddle James A. , Cooper John A. , Waterston Robert H. 
Published: April 2021

ABSTRACT
During Caenorhabditis elegans embryogenesis, specific cells in the P1 lineage rotate their duplicated centrosome pair onto the anterior-posterior axis; this rotation is correlated with and necessary for a differential inheritance of cytoplasmic determinants in the daughter cells. Centrosome pair rotation is sensitive to inhibitors of actin and microtubule polymerization and may require microtubule attachment to a specific cortical site. We show that actin and the barbed-end binding protein, capping protein, transiently accumulate at this cortical site, possibly by assembly onto persistent remnants of previous cell divisions. Based on these observations, we propose a model for the molecular basis of centrosome rotation that is consistent with the dependence of rotation on actin filaments and microtubules.