bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiple requirements for the receptor serine/threonine kinase thick veins reveal novel functions of TGFβ homologs during Drosophila embryogenesis
Authors: Affolter Markus , Nellen Denise , Nussbaumer Ute , Basler Konrad 
Published: April 2021

ABSTRACT
Differentiation of distinct cell types at specific locations within a developing organism depends largely on the ability of cells to communicate. A major class of signalling proteins implicated in cell to cell communication is represented by members of the TGFβ superfamily. A corresponding class of transmembrane serine/threonine kinases has recently been discovered that act as cell surface receptors for ligands of the TGFβ superfamily. The product of the Drosophila gene decapentaplegic (dpp) encodes a TGFβ homolog that plays multiple roles during embryogenesis and the development of imaginal discs. Here we describe the complex expression pattern of thick veins (tkv), which encodes a receptor for dpp. We make use of tkv loss-of-function mutations to examine the consequences of the failure of embryonic cells to respond to dpp and/or other TGFβ homologs. We find that while maternal tkv product allows largely normal dorsoventral pattering of the embryo, zygotic tkv activity is indispensable for dorsal closure of the embryo after germ band retraction. Fur-thermore, tkv activity is crucial for patterning the visceral mesoderm; in the absence of functional tkv gene product, visceral mesoderm parasegment 7 cells fail to express Ultra-bithorax, but instead accumulate Antennapedia protein. The tkv receptor is therefore involved in delimiting the expression domains of homeotic genes in the visceral mesoderm. Interestingly, tkv mutants fail to establish a proper tracheal network. Tracheal braches formed by cells migrating in dorsal or ventral directions are absent in tkv mutants. The requirements for tkv in dorsal closure, visceral mesoderm and trachea development assign novel functions to dpp or a closely related member of the TGFβ superfamily.
Segment and cell type lineage restrictions during pharyngeal arch development in the zebrafish embryo
Authors: Schilling Thomas F. , Kimmel Charles B. 
Published: April 2021

ABSTRACT
In zebrafish, the segmental series of pharyngeal arches is formed predominantly by two migratory cell types, neural crest and paraxial mesoderm, which arise in the early embryo. Neural crest cells migrate ventrally out of the neuroepithelium and into the arches to form cartilage, neurons, glia and pigment cells. Surrounding mesoderm generates muscles and endothelia. We labeled individual pharyngeal precursor cells with fluorescent dyes and found that their clonal progeny were confined to single segments and generated single cell types. When a neural crest or mesodermal cell was marked before migration into the pharynx, its progeny dispersed but generally remained confined to a single arch primordium. Such segmental restrictions arose first in the most rostral arches, mandibular and hyoid, and progressed caudally. The phenotypes of progeny generated by single cells were examined in the mandibular arch. Clones derived from premigratory neural crest cells generally did not contribute to more than one cell type. Further, the progenitors of some cell types were spatially separated in the premigratory crest. In particular, neurogenic crest cells were situated further laterally than cells that generate cartilage and connective tissues, while pigment and glial cell progenitors were more evenly distributed. Based on these results we suggest that arch precursors may be specified as to their eventual fates before the major morphogenetic movements that form the arch primordia. Further, cell movements are restricted during segmentation establishing a group of arch precursors as a unit of developmental patterning, as in the fashion of vertebrate rhombomeres or segmental lineage compartments in Drosophila.
Pax-3 is required for the development of limb muscles: a possible role for the migration of dermomyotomal muscle progenitor cells
Authors: Bober Eva , Franz Thomas , Arnold Hans-Henning , Gruss Peter , Tremblay Patrick 
Published: April 2021

ABSTRACT
Limb muscles in vertebrates originate from dermomyotomal cells, which during early development migrate from the ventrolateral region of somites into the limb buds. These progenitor cells do not express any muscle-specific marker genes or myogenic transcription factors until they reach their destination in the limbs. Here, we demonstrate by in situ hybridization that myogenic cells in somites and a population of presumably migratory muscle precursor cells in somatopleural tissue as well as myoblasts in the developing limbs express Pax-3. Significantly, in homozygous splotch mutant mice, which synthesize altered Pax-3 mRNA but make no normal protein, no cells positive for Pax-3 transcripts can be detected in the region of migrating limb muscle precursors or in the limb itself. In contrast, myotomal precursor cells and axial skeletal muscles contain Pax-3 transcripts also in the mutant. Interestingly, these animals fail to develop limb musculature as demon-strated by the lack of hybridization with various probes for myogenic transcription factors (Myf-5, myogenin, MyoD) but make apparently normal axial muscles. These observations suggest that Pax-3 is necessary for the formation of limb muscles, affecting either the generation of myogenic precursors in the somitic dermomyotome or the migration of these cells into the limb field.
The fate of the CNS midline progenitors in Drosophila as revealed by a new method for single cell labelling
Authors: Bossing Torsten , Technau Gerhard M. 
Published: April 2021

ABSTRACT
We present a new method for marking single cells and tracing their development through embryogenesis. Cells are labelled with a lipophilic fluorescent tracer (DiI) in their normal positions without impaling their membranes. The dye does not diffuse between cells but is transferred to the progeny, disclosing their morphology in all detail. Behaviour of labelled cells can be observed in vivo (cell divisions, morphogenetic movements and differentiation). Following photoconversion of the dye, fully differentiated clones can be analyzed in permanent preparations.
We apply this method for cell lineage analysis of the embryonic Drosophila CNS. Here we describe the fate of the CNS midline cells. We present the complete lineages of these cells in the fully differentiated embryo and show that variability exists in segmental numbers of the midline progenitors as well as in the composition of their lineages.
A primary requirement for nodal in the formation and maintenance of the primitive streak in the mouse
Authors: Conlon Frank L , Lyons Karen M , Takaesu Norma , Barth Katrin S , Kispert Andreas , Herrmann Bernhard , Robertson Elizabeth J 
Published: April 2021

ABSTRACT
The 413.d insertional mutation arrests mouse development shortly after gastrulation. nodal, a novel TGFb-related gene, is closely associated with the locus. The present study provides direct evidence that the proviral insertion causes a loss of function mutation. nodal RNA is initially detected at day 5.5 in the primitive ectoderm. Concomitant with gastrulation, expression becomes restricted to the proximal posterior regions of the embryonic ectoderm. nodal RNA is also expressed in the primitive endoderm overlying the primitive streak. A few hours later, expression is strictly confined to the periphery of the mature node. Interestingly 413.d mutant embryos show no morphological evidence for the formation of a primitive streak. Nonetheless, about 25% of mutant embryos do form randomly positioned patches of cells of a posterior mesodermal character. Data presented in this report demonstrate the involvement of a TGFb-related molecule in axis formation in mammals.
Multiple developmental defects in Engrailed-1 mutant mice: an early mid-hindbrain deletion and patterning defects in forelimbs and sternum
Authors: Wurst Wolfgang , Auerbach Anna B. , Joyner Alexandra L. 
Published: April 2021

ABSTRACT
During mouse development, the homeobox-containing gene En-1 is specifically expressed across the mid-hindbrain junction, the ventral ectoderm of the limb buds, and in regions of the hindbrain, spinal cord, somites and somite-derived tissues. To address the function of En-1 during embryogenesis, we have generated mice homozygous for a targeted deletion of the En-1 homeobox. En-1 mutant mice died shortly after birth and exhibited multiple developmental defects. In the brains of newborn mutants, most of the colliculi and cerebellum were missing and the third and fourth cranial nerves were absent. A deletion of mid-hindbrain tissue was observed as early as 9.5 days of embryonic development and the phenotype resembles that previously reported for Wnt-1 mutant mice. In addition, patterning of the forelimb paws and sternum was disrupted, and the 13th ribs were truncated. The results of these studies suggest a cell autonomous role for En-1 in generation and/or survival of mid-hindbrain precursor cells and also a non-cell autonomous role in signaling normal development of the limbs and possibly sternum.
The expression pattern of a novel gene encoding brain-fatty acid binding protein correlates with neuronal and glial cell development
Authors: Kurtz Andreas , Zimmer Andreas , Schnütgen Frank , Brüning Gerold , Spener Friedrich , Müller Thomas 
Published: April 2021

ABSTRACT
Fatty acid binding proteins (FABPs) are a multigene family of small intracellular proteins that bind hydrophobic ligands. In this report we describe the cloning and expression pattern of a novel member of this gene family that is specifically expressed in the developing and adult nervous system and thus was designated brain (B)-FABP. B-FABP is closely related to heart (H)-FABP with 67% amino acid identity. B-FABP expression was first detected at mouse embryonic day 10 in neuroepithelial cells and its pattern correlates with early neuronal differentiation. Upon further development, B-FABP was confined to radial glial cells and immature astrocytes. B-FABP mRNA and protein were found in glial cells of the peripheral nervous system such as satellite cells of spinal and cranial ganglia and ensheathing cells of the olfactory nerve layer from as early as embryonic day 11 until adulthood. In the adult mouse brain, B-FABP was found in the glia limitans, in radial glial cells of the hippocampal dentate gyrus and Bergman glial cells. These findings suggest a function of B-FABP during neurogenesis or neuronal migration in the developing nervous system. The partially overlapping expression pattern with that of cellular retinoid binding proteins suggests that B-FABP is involved in the metabo-lism of a so far unknown hydrophobic ligand with potential morphogenic activity during CNS development.
blistered: a gene required for vein/intervein formation in wings of Drosophila
Authors: Fristrom Dianne , Gotwals Philip , Eaton Suzanne , Kornberg Thomas B. , Sturtevant Mark , Bier Ethan , Fristrom James W. 
Published: April 2021

ABSTRACT
We have characterized the blistered (bs) locus phenotypically, genetically and developmentally using a set of new bs alleles. Mutant defects range from wings with ectopic veins and intervein blisters to completely ballooned wings where the distinction between vein and intervein is lost. Mosaic analyses show that severe bs alleles behave largely autonomously; homozygous patches having vein-like properties. Developmental analyses were undertaken using light and electron microscopy of wild-type and bs wings as well as confocal microscopy of phalloidin- and laminin-stained preparations. bs defects were first seen early in the prepupal period with the failure of apposition of dorsal and ventral wing epithelia. Correspondingly, during definitive vein/intervein differentiation in the pupal period (18–36 hours after puparium formation), the extent of dorsal/ventral reapposition is reduced in bs wings. Regions of the wing that fail to become apposed differentiate properties of vein cells; i.e. become constricted apically and acquire a laminin-containing matrix basally.
To further understand bs function, we examined genetic interactions between various bs alleles and mutants of two genes whose products have known functions in wing development. (i) rhomboid, a component of the EGF-R signalling pathway, is expressed in vein cells and is required for specification of vein cell fate. rhove mutations (lacking rhomboid in wings) suppress the excess vein formation and associated with bs. Conversely, rho expression in prepupal and pupal bs wings is expanded in the regions of increased vein formation. (ii) The integrin genes, inflated and myospheroid, are expressed in intervein cells and are required for adhesion between the dorsal and ventral wing surfaces. Loss of integrin function results in intervein blisters. Integrin mutants interact with bs mutants to increase the frequency of intervein blisters but do not typically enhance vein defects. Both developmental and genetic analyses suggest that the bs product is required during metamorphosis for the initiation of intervein development and the concomitant inhibition of vein development.
Ectopic expression of activated Ras1 induces hyperplastic growth and increased cell death in Drosophila imaginal tissues
Authors: Karim Felix D. , Rubin Gerald M. 
Published: April 2021

ABSTRACT
The Drosophila Ras1 gene is required for proper cell fate specification throughout development, and the loss-of-function phenotype of Ras1 suggests an additional role in cell proliferation or survival. A direct role for RAS1 in promoting cell proliferation, however, has not been established. We show that expression of an activated form of RAS1 (RAS1V12) during Drosophila imaginal disc development is sufficient to drive ectopic cell proliferation and hyperplastic tissue growth. In addition, expression of RAS1V12 induces widespread cell death in the imaginal discs, including cells not expressing the transgene, which results in ablation of adult structures. Loss-of-function mutations in the genes encoding RAF, MEK, MAPK and KSR dominantly suppress RAS1V12-induced cell proliferation. Furthermore, two RAS effector loop mutations (E37G and Y40C) that block the RAS-RAF interaction, also suppress RAS1V12-induced proliferation, consistent with a requirement for the MAPK cascade during the RAS1 mitogenic response. These two RAS effector loop mutants, however, retain some activity and can act synergistically with a MAPK gain-of-function mutation, suggesting that RAS1 may also act through signaling pathway(s) distinct from the MAPK cascade.
Expression of murine STF-1, a putative insulin gene transcription factor, in β cells of pancreas, duodenal epithelium and pancreatic exocrine and endocrine progenitors during ontogeny
Authors: Guz Y. , Montminy M. R. , Stein R. , Leonard J. , Gamer L. W. , Wright C. V. E. , Teitelman G. 
Published: April 2021

ABSTRACT
The XlHbox 8 homeodomain protein of Xenopus and STF-1, its mammalian homolog, are selectively expressed by β cells of adult mouse pancreatic islets, where they are likely to regulate insulin expression. We sought to determine whether the expression of the homeobox protein/s during mouse embryonic development was specific to β cells or, alternatively, whether XlHbox 8/STF-1 protein/s were initially expressed by multipotential precursors and only later became restricted to the insulin-containing cells. With two antibodies, we studied the localization of STF-1 during murine pancreatic development. In embryos, as in adults, STF-1 was expressed by most β cells, by subsets of the other islet cell types and by mucosal epithelial cells of the duodenum. In addition, most epithelial cells of the pancreatic duct and exocrine cells of the pancreas transiently contained STF-1. We conclude that in mouse, STF-1 not only labels a domain of intestinal epithelial cells but also provides a spatial and temporal marker of endodermal commitment to a pancreatic and subsequently, to an endocrine β cell fate. We propose a model of pancreatic cell development that suggests that exocrine and endocrine (α, β, ∂ and PP) cells arise from a common precursor pool of STF-1+ cells and that progression towards a defined mono-specific non-β cell type is correlated with loss of STF-1 expression.
Developmental expression of the lipocalin Lazarillo and its role in axonal pathfinding in the grasshopper embryo
Authors: Sánchez Diego , D. Ganfornina María , Bastiani Michael J. 
Published: April 2021

ABSTRACT
This article describes the expression pattern and functional analysis of Lazarillo, a novel cell surface glycoprotein expressed in the embryonic grasshopper nervous system, and a member of the lipocalin family. Lazarillo is expressed by a subset of neuroblasts, ganglion mother cells and neurons of the central nervous system, by all sensory neurons of the peripheral nervous system, and by a subset of neurons of the enteric nervous system. It is also present in a few non neuronal cells associated mainly with the excretory system. A monoclonal antibody raised against Lazarillo perturbs the extent and direction of growth of identified commissural pioneer neurons. We propose that Lazarillo is the receptor for a midline morphogen involved in the outgrowth and guidance of these neurons.
Transposon induced chimeras show that floricaula, a meristem identity gene, acts non-autonomously between cell layers
Authors: Carpenter Rosemary , Coen Enrico S. 
Published: April 2021

ABSTRACT
Flower meristems comprise several distinct cell layers. To understand the role of cell interactions between and within these layers, we have generated plants chimeric for a key floral homeotic gene, floricaula (flo). These chimeras arose in Antirrhinum by excision of a transposon, restoring flo gene function. Activity of flo in a subset of cell layers gives fertile flowers with an abnormal morphology. This shows that flo can act non-autonomously between layers, although some aspects of its function are impaired. In addition, we show that flo exhibits some cell-autonomy within layers.
The Xenopus laevis tail-forming region
Authors: Tucker Abigail S. , Slack Jonathan M. W. 
Published: April 2021

ABSTRACT
A fate map is produced for the Xenopus tail-forming region at the neurula stage by orthotopic grafting of tissue labelled with fluorescein-dextran amine. It is shown that the axial tissues of the tail are derived from a rectangle 700 μm wide by 600 μm long, while the epidermis of the tail is drawn from a much larger area. The fate map shows that much of the final tail is not formed from the tail bud itself, but by a displacement of trunk axial tissue relative to the proctodaeum.
A specification map is also produced by culturing parts of the tail-forming region in vitro or as grafts on a neutral site on host embryos. For the axial tissues this map is identical to the fate map, showing that the tail-forming region is embryologically mosaic. The prospective tail epidermis can, however, regulate defects.
It is shown that previous claims of regeneration of the Xenopus tail bud are misleading. Removal of the tailforming region totally prevents tail development. Removal of the tail bud leads to a partial tail, formed by the normal process of displacement of trunk tissue relative to the proctodaeum. Even when only part of the tail bud is removed the tail is still truncated. This shows that there is no terminal regeneration of the tail at embryonic stages.
Neuroectodermal fate of epiblast cells in the distal region of the mouse egg cylinder: implication for body plan organization during early embryogenesis
Authors: Quinlan Gabriel A. , Williams Elizabeth A. , Tan Seong-Seng , Tam Patrick P. L. 
Published: April 2021

ABSTRACT
The developmental fate of cells in the distal region (distal cap) of the epiblast was analysed by fate mapping studies. The displacement and differentiation of cells labelled in situ with carbocyanine dyes and lacZ-expressing cells grafted to the distal cap were studied over a 48-hour period of in vitro development. The distal cap epiblast differentiates predominantly into neurectodermal cells. Cells at the anterior site of the distal cap colonise the fore-, midand hindbrain and contribute to non-neural ectoderm cells of the amnion and craniofacial surface ectoderm. Those cells in the most distal region of the epiblast contribute to all three brain compartments as well as the spinal cord and the posterior neuropore. Cells at the posterior site of the distal cap are mainly localised to the caudal parts of the neural tube. A minor contribution to the embryonic (paraxial and lateral) and extraembryonic (allantoic and yolk sac) mesoderm is also found. Epiblast cells located outside the distal cap give rise to surface ectoderm and other non-ectodermal derivatives, with only a minor contribution to the neuroectoderm. Results of this study provide compelling evidence that the precursor population of the neural tube is contained in the distal cap epiblast of the early-primitive-streak-stage embryo. Furthermore, the regionalisation of cell fate within this small population suggest that a preliminary craniocaudal patterning may have occurred in the neural primordium before neurulation.
The dual role of hermaphrodite in the Drosophila sex determination regulatory hierarchy
Authors: Pultz Mary Anne , Baker Bruce S. 
Published: April 2021

ABSTRACT
The hermaphrodite (her) locus has both maternal and zygotic functions required for normal female development in Drosophila. Maternal her function is needed for the viability of female offspring, while zygotic her function is needed for female sexual differentiation. Here we focus on understanding how her fits into the sex determination regulatory hierarchy. Maternal her function is needed early in the hierarchy: genetic interactions of her with the sisterless genes (sis-a and sis-b), with function-specific Sex-lethal (Sxl) alleles and with the constitutive allele SxlM#1 suggest that maternal her function is needed for Sxl initiation. When mothers are defective for her function, their daughters fail to activate a reporter gene for the Sxl early promoter and are deficient in Sxl protein expression. Dosage compensation is misregulated in the moribund daughters: some salivary gland cells show binding of the maleless (mle) dosage compensation regulatory protein to the X chromosome, a binding pattern normally seen only in males. Thus maternal her function is needed early in the hierarchy as a positive regulator of Sxl, and the maternal effects of her on female viability probably reflect Sxl’s role in regulating dosage compensation. In contrast to her’s maternal function, her’s zygotic function in sex determination acts at the end of the hierarchy. This zygotic effect is not rescued by constitutive Sxl expression, nor by constitutive transformer (tra) expression. Moreover, the expression of doublesex (dsx) transcripts appears normal in her mutant females. We conclude that the maternal and zygotic functions of her are needed at two distinctly different levels of the sex determination regulatory hierarchy.