bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hyperactivation of the folded gastrulation pathway induces specific cell shape changes
Authors: Morize Pierre , Christiansen Audrey E. , Costa Mike , Parks Suki , Wieschaus Eric 
Published: April 2021

ABSTRACT
During Drosophila gastrulation, mesodermal precursors are brought into the interior of the embryo by formation of the ventral furrow. The first steps of ventral furrow formation involve a flattening of the apical surface of the presumptive mesodermal cells and a constriction of their apical diameters. In embryos mutant for folded gastrulation (fog), these cell shape changes occur but the timing and synchrony of the constrictions are abnormal. A similar phenotype is seen in a maternal effect mutant, concertina (cta). fog encodes a putative secreted protein whereas cta encodes an α-subunit of a heterotrimeric G protein. We have proposed that localized expression of the fog signaling protein induces apical constriction by interacting with a receptor whose downstream cellular effects are mediated by the cta Gα protein.
In order to test this model, we have ectopically expressed fog at the blastoderm stage using an inducible promoter. In addition, we have examined the constitutive activation of cta protein by blocking GTP hydrolysis using both in vitro synthesized mutant alleles and cholera toxin treatment. Activation of the fog/cta pathway by any of these procedures results in ectopic cell shape changes in the gastrula. Uniform fog expression rescues the gastrulation defects of fog null embryos but not cta mutant embryos, arguing that cta functions downstream of fog expression. The normal location of the ventral furrow in embryos with uniformly expressed fog suggests the existence of a fog-independent pathway determining mesoderm-specific cell behaviors and invagination. Epistasis experiments indicate that this pathway requires snail but not twist expression.
Sensory axons are guided by local cues in the developing dorsal spinal cord
Authors: Sharma Kamal , Frank Eric 
Published: April 2021

ABSTRACT
During development, different classes of sensory neurons establish distinctive central projections within the spinal cord. Muscle spindle afferents (Ia fibers) grow ventrally through the dorsal horn to the ventral cord, whereas cutaneous sensory collaterals remain confined to the dorsal horn. We have studied the nature of the cues used by Ia fibers in establishing their characteristic projections within the dorsal horn. An organotypic culture preparation of embryonic chicken spinal cord and sensory ganglia was used to test the influence of ventral spinal cord and local cues within the dorsal spinal cord on the growing Ia afferents.
When the ventral half of the spinal cord was replaced with an inverted duplicate dorsal half, Ia fibers entering through the dorsal columns still grew ventrally within the host dorsal horn. After the fibers entered the duplicate dorsal half, they continued growing in the same direction. With respect to the duplicate dorsal tissue, this was in an opposite, ventral-to-dorsal, direction. In both cases, however, Ia collaterals remained confined to the medial dorsal laminae. Restriction to these laminae was maintained even when the fibers had to change their direction of growth to stay within them. These results show that cues from the ventral cord are not required for the development of correct Ia projections within the dorsal horn. Local, rather than long-range directional, cues appear to determine the pattern of these projections. When the ventral half of the spinal cord was left intact but sensory axons were forced to enter the dorsal gray matter growing rostrally or caudally, their collateral axons grew in random directions, further showing the absence of directional cues even when the ventral cord was present. Taken together, these observations suggest that Ia fibers are guided by local positional cues that keep them confined to the medial gray matter within the dorsal horn, but their direction of growth is determined primarily by their orientation and position as they enter the dorsal gray matter.
Two regulatory genes, cNkx5-1 and cPax2, show different responses to local signals during otic placode and vesicle formation in the chick embryo
Authors: Herbrand Heike , Guthrie Sarah , Hadrys Thorsten , Hoffmann Sonja , Arnold Hans-Henning , Rinkwitz-Brandt Silke , Bober Eva 
Published: April 2021

ABSTRACT
The early stages of otic placode development depend on signals from neighbouring tissues including the hindbrain. The identity of these signals and of the responding placodal genes, however, is not known. We have identified a chick homeobox gene cNkx5-1, which is expressed in the otic placode beginning at stage 10 and exhibits a dynamic expression pattern during formation and further differentiation of the otic vesicle. In a series of heterotopic transplantation experiments, we demonstrate that cNkx5-1 can be activated in ectopic positions. However, significant differences in otic development and cNkx5-1 gene activity were observed when placodes were transplanted into the more rostral positions within the head mesenchyme or into the wing buds of older hosts. These results indicate that only the rostral tissues were able to induce and/or maintain ear development. Ectopically induced cNkx5-1 expression always reproduced the endogenous pattern within the lateral wall of the otocyst that is destined to form vestibular structures. In contrast, cPax2 which is expressed in the medial wall of the early otic vesicle later forming the cochlea never resumed its correct expression pattern after transplantation. Our experiments illustrate that only some aspects of gene expression and presumably pattern formation during inner ear development can be established and maintained ectopically. In particular, the dorsal vestibular structures seem to be programmed earlier and differently from the ventral cochlear part.
The genetic control of the distinction between fat body and gonadal mesoderm in Drosophila
Authors: Riechmann Veit , Rehorn Klaus-Peter , Reuter Rolf , Leptin Maria 
Published: April 2021

ABSTRACT
The somatic muscles, the heart, the fat body, the somatic part of the gonad and most of the visceral muscles are derived from a series of segmentally repeated primordia in the Drosophila mesoderm. This work describes the early development of the fat body and its relationship to the gonadal mesoderm, as well as the genetic control of the development of these tissues.
Segmentation and dorsoventral patterning genes define three regions in each parasegment in which fat body precursors can develop. Fat body progenitors in these regions are specified by different genetic pathways. Two regions require engrailed and hedgehog for their development while the third is controlled by wingless. decapentaplegic and one or more unknown genes determine the dorsoventral extent of these regions. In each of parasegments 10-12 one of these regions generates somatic gonadal precursors instead of fat body. The balance between fat body and somatic gonadal fate in these serially homologous cell clusters is controlled by at least five genes. We suggest a model in which tinman, engrailed and wingless are necessary to permit somatic gonadal develoment, while serpent counteracts the effects of these genes and promotes fat body development. The homeotic gene abdominalA limits the region of serpent activity by interfering in a mutually repressive feed back loop between gonadal and fat body development.
Genetic control of branching pattern and floral identity during Petunia inflorescence development
Authors: Souer Erik , Krol Alexander van der , Kloos Daisy , Spelt Cornelis , Bliek Mattijs , Mol Jos , Koes Ronald 
Published: April 2021

ABSTRACT
A main determinant of inflorescence architecture is the site where floral meristems are initiated. We show that in wild-type Petunia bifurcation of the inflorescence meristem yields two meristems of approximately equal size. One terminates into a floral meristem and the other maintains its inflorescence identity. By random transposon mutagenesis we have generated two mutants in which the architecture of the inflorescence is altered. In the extra petals− (exp) mutant the inflorescence terminates with the formation of a single terminal flower. Phenotypic analysis showed that exp is required for the bifurcation of inflorescence meristems. In contrast, the aberrant leaf and flower− (alf) mutant is affected in the specification of floral meristem identity while the branching pattern of the inflorescence remains unaltered. A weak alf allele was identified that, after bifurcation of the inflorescence meristem, yields a ‘floral’ meristem with partial inflorescence characteristics. By analysing independent transposon dTph1 insertion alleles we show that the alf locus encodes the Petunia FLORICAULA/LEAFY homolog. In situ hybridisation shows that alf is expressed in the floral meristem and also in the vegetative meristem. Differences and similarities between these Petunia mutants and mutations affecting inflorescence architecture in other species will be discussed.
The hsp70 protein is involved in the acquisition of gamete self-sterility in the ascidian Ciona intestinalis
Authors: Marino Rita , Pinto Maria Rosaria , Cotelli Franco , Lamia Carla Lora , De Santis Rosaria 
Published: April 2021

SUMMARY
In the hermaphrodite ascidian Ciona intestinalis, gamete self-incompatibility is a mechanism that prevents selffertilization and is based on the ability of the oocyte vitelline coat to distinguish and accept only heterologous spermatozoa. The onset of self-sterility occurs during oogenesis and involves or is controlled by the follicle cells. Gamete self-nonself discrimination, a process that can be likened to an immune recognition event, represents a useful model with which to study the evolution of self-nonself recognition. Hsp70 genes, which belong to the major histocompatibility complex (MHC) class III, are supposedly ancestors of the MHC class I and II genes, and chaperonins are known to be involved in antigen processing and presentation. We have isolated and characterized an hsp70gene (Cihsp70) that is constitutively expressed during oogenesis in the follicle cells of previtellogenic and vitellogenic oocytes. Using a polyclonal antibody against Cihsp70 protein, we demonstrate that the expression of Cihsp70 is required for the switch from self-fertility to self-sterility. The functional involvement of Cihsp70 in gamete self-nonself recognition provides evidence for an ancestral MHC-like system in protochordates.
Progenitors of dorsal commissural interneurons are defined by MATH1 expression
Authors: Helms Amy W. , Johnson Jane E. 
Published: April 2021

SUMMARY
MATH1 is a neural-specific basic helix-loop-helix transcription factor. Members of this family of transcription factors are involved in the development of specific subsets of neurons in the developing vertebrate nervous system. Here we examine the cells expressing MATH1 with respect to their proliferative state and coexpression of cell-type-specific differentiation markers. We localize the MATH1 protein to the nucleus of cells in the dorsal neural tube and the external germinal layer (EGL) of the developing cerebellum. Using double-label immunofluorescence, we demonstrate that MATH1- expressing cells span both the proliferating and the differentiating zones within the dorsal neural tube, but within the EGL of the cerebellum are restricted to the proliferating zone. The early differentiating MATH1-expressing cells in the dorsal neural tube co-express TAG-1, DCC-1 and LH2, markers of dorsal commissural interneurons. In addition, transgenic mice with lacZ under the transcriptional control of MATHl-flanking DNA sequences express β -galactosidase specifically in the developing nervous system, in a manner that mimics subsets of the MATH 1-expression pattern, including the dorsal spinal neural tube. Expression of the MATHl/lacZ transgene persists in differentiated dorsal commissural interneurons. Taken together, we demonstrate MATH1 expression in a differentiating population of neuronal precursors in the dorsal neural tube that appear to give rise specifically to dorsal commissural interneurons.
Integrated FGF and BMP signaling controls the progression of progenitor cell differentiation and the emergence of pattern in the embryonic anterior pituitary
Authors: Ericson Johan , Norlin Stefan , Jessell Thomas M. , Edlund Thomas 
Published: April 2021

ABSTRACT
The mechanisms by which inductive signals control the identity, proliferation and timing of differentiation of progenitor cells in establishing spatial pattern in developing vertebrate tissues remain poorly understood. We have addressed this issue in the embryonic anterior pituitary, an organ in which distinct hormone cell types are generated in a precise temporal and spatial order from an apparently homogenous ectodermal primordium. We provide evidence that in this tissue the coordinate control of progenitor cell identity, proliferation and differentiation is imposed by spatial and temporal restrictions in FGF- and BMP-mediated signals. These signals derive from adjacent neural and mesenchymal signaling centers: the infundibulum and ventral juxtapituitary mesenchyme. The infundibulum appears to have a dual signaling function, serving initially as a source of BMP4 and subsequently of FGF8. The ventral juxtapituitary mesenchyme appears to serve as a later source of BMP2 and BMP7. In vitro, FGFs promote the proliferation of progenitor cells, prevent their exit from the cell cycle and contribute to the specification of progenitor cell identity. BMPs, in contrast, have no apparent effect on cell proliferation but instead appear to act with FGFs to control the initial selection of thyrotroph and corticotroph progenitor identity.
Genetic interactions between Hoxa1 and Hoxb1 reveal new roles in regulation of early hindbrain patterning
Authors: Studer Michèle , Gavalas Anthony , Marshall Heather , Ariza-McNaughton Linda , Rijli Filippo M. , Chambon Pierre , Krumlauf Robb 
Published: April 2021

ABSTRACT
In the developing vertebrate hindbrain Hoxa1 and Hoxb1 play important roles in patterning segmental units (rhombomeres). In this study, genetic analysis of double mutants demonstrates that both Hoxa1 and Hoxb1 participate in the establishment and maintenance of Hoxb1 expression in rhombomere 4 through auto- and para-regulatory interactions. The generation of a targeted mutation in a Hoxb1 3′ retinoic acid response element (RARE) shows that it is required for establishing early high levels of Hoxb1 expression in neural ectoderm. Double mutant analysis with this Hoxb13′RARE allele and other targeted loss-of-function alleles from both Hoxa1 and Hoxb1 reveals synergy between these genes. In the absence of both genes, a territory appears in the region of r4, but the earliest r4 marker, the Eph tyrosine kinase receptor EphA2, fails to be activated. This suggests a failure to initiate rather than maintain the specification of r4 identity and defines new roles for both Hoxb1 and Hoxa1 in early patterning events in r4. Our genetic analysis shows that individual members of the vertebrate labial-related genes have multiple roles in different steps governing segmental processes in the developing hindbrain.
dorsotonals/homothorax, the Drosophila homologue of meis1, interacts with extradenticle in patterning of the embryonic PNS
Authors: Kurant Estee , Pai Chi-yun , Sharf Rakefet , Halachmi Naomi , Sun Y. Henry , Salzberg Adi 
Published: April 2021

ABSTRACT
The homeotic genes of the bithorax complex are required, among other things, for establishing the patterns of sensory organs in the embryonic peripheral nervous system (PNS). However, the molecular mechanisms by which these genes affect pattern formation in the PNS are not understood and other genes that function in this pathway are not characterized. Here we report the phenotypic and molecular analysis of one such gene, homothorax (hth; also named dorsotonals). Mutations in the hth gene seem to alter the identity of the abdominal chordotonal neurons, which depend on Abd-A for their normal development. However, these mutations do not alter the expression of the abd-A gene, suggesting that hth may be involved in modulating abd-A activity. We have generated multiple mutations in the hth locus and cloned the hth gene. hth encodes a homeodomain-containing protein that is most similar to the murine proto-oncogene meis1. The hth gene is expressed throughout embryonic development in a spatially restricted pattern, which is modulated in abdominal segments by abd-A and Ubx.
The spatial distribution of the HTH protein during embryonic development is very similar to the distribution of the Extradenticle (EXD) protein, a known modulator of homeotic gene activity. Here we show that the PNS phenotype of exd mutant embryos is virtually indistinguishable from that of hth mutant embryos and does not simply follow the homeotic transformations observed in the epidermis. We also show that the HTH protein is present in extremely low levels in embryos lacking exd activity as compared to wild-type embryos. In contrast, the EXD protein is present in fairly normal levels in hth mutant embryos, but fails to accumulate in nuclei and remains cytoplasmic. Ectopic expression of hth can drive ectopic nuclear localization of EXD. Based on our observations we propose that the genetic interactions between hth and exd serve as a novel mechanism for regulating homeotic protein activity in embryonic PNS development.
EGL-17(FGF) expression coordinates the attraction of the migrating sex myoblasts with vulval induction in C. elegans
Authors: Burdine Rebecca D. , Branda Catherine S. , Stern Michael J. 
Published: April 2021

ABSTRACT
During the development of the egg-laying system in Caenorhabditis elegans hermaphrodites, central gonadal cells organize the alignment of the vulva with the sex myoblasts, the progenitors of the egg-laying muscles. A fibroblast growth factor [EGL-17(FGF)] and an FGF receptor [EGL-15(FGFR)] are involved in the gonadal signals that guide the migrations of the sex myoblasts. Here we show that EGL-17(FGF) can act as an instructive guidance cue to direct the sex myoblasts to their final destinations. We find that egl-17 reporter constructs are expressed in the primary vulval cell and that EGL-17(FGF) expression in this cell correlates with the precise positioning of the sex myoblasts. We postulate that EGL-17(FGF) helps to coordinate the development of a functional egg-laying system, linking vulval induction with proper sex myoblast migration.
Regulation in the heart field of zebrafish
Authors: Serbedzija George N. , Chen Jau-Nian , Fishman Mark C. 
Published: April 2021

ABSTRACT
In many vertebrates, removal of early embryonic heart precursors can be repaired, leaving the heart and embryo without visible deficit. One possibility is that this ‘regulation’ involves a cell fate switch whereby cells, perhaps in regions surrounding normal progenitors, are redirected to the heart cell fate. However, the lineage and spatial relationships between cells that are normal heart progenitors and those that can assume that role after injury are not known, nor are their molecular distinctions.
We have adapted a laser-activated technique to label single or small patches of cells in the lateral plate mesoderm of the zebrafish and to track their subsequent lineage. We find that the heart precursor cells are clustered in a region adjacent to the prechordal plate, just anterior to the notochord tip. Complete unilateral ablation of all heart precursors with a laser does not disrupt heart development, if performed before the 18-somite stage. By combining extirpation of the heart precursors with cell labeling, we find that cells anterior to the normal cardiogenic compartments constitute the source of regulatory cells that compensate for the loss of the progenitors.
One of the earliest embryonic markers of the premyocardial cells is the divergent homeodomain gene, Nkx2.5. Interestingly, normal cardiogenic progenitors derive from only the anterior half of the Nkx2.5-expressing region in the lateral plate mesoderm. The posterior half, adjacent to the notochord, does not include cardiac progenitors and the posterior Nkx2.5-expressing cells do not contribute to the heart, even after ablation of the normal cardiogenic region.
The cells that can acquire a cardiac cell fate after injury to the normal progenitors also reside near the prechordal plate, but anterior to the Nkx2.5-expressing domain. Normally they give rise to head mesenchyme. They share with cardiac progenitors early expression of GATA 4. The location of the different elements of the cardiac field, and their response to injury, suggests that the prechordal plate supports and/or the notochord suppresses the cardiac fate.
Tripartite organization of the ancestral chordate brain and the antiquity of placodes: insights from ascidian Pax-2/5/8, Hox and Otx genes
Authors: Wada Hiroshi , Saiga Hidetoshi , Satoh Noriyuki , Holland Peter W. H. 
Published: April 2021

ABSTRACT
Ascidians and vertebrates belong to the Phylum Chordata and both have dorsal tubular central nervous systems. The structure of the ascidian neural tube is extremely simple, containing less than 400 cells, among which less than 100 cells are neurons. Recent studies suggest that, despite its simple organization, the mechanisms patterning the ascidian neural tube are similar to those of the more complex vertebrate brain. Identification of homologous regions between vertebrate and ascidian nervous systems, however, remains to be resolved. Here we report the expression of HrPax-258 gene: an ascidian homologue of vertebrate Pax-2, Pax-5 and Pax-8 genes. Molecular phylogenetic analyses indicate that HrPax-258 is descendant from a single precursor gene that gave rise to the three vertebrate genes. The expression pattern of HrPax-258 suggests that this subfamily of Pax genes has conserved roles in regional specification of the brain. Comparison with expression of ascidian Otx (Hroth) and a Hox gene (HrHox1) by double-staining in situ hybridizations indicate that the ascidian brain region can be subdivided into three regions; the anterior region marked by Hroth probably homologous to the vertebrate forebrain and midbrain, the middle region marked by HrPax-258 probably homologous to the vertebrate anterior hindbrain (and maybe also midbrain) and the posterior region marked by Hox genes which is homologous to the vertebrate hindbrain and spinal cord. Later expression of HrPax-258 in atrial primordia implies that basal chordates such as ascidians have already acquired a sensory organ that develops from epidermal thickenings (placodes) and expresses HrPax-258; we suggest it is homologous to the vertebrate ear. Therefore, placodes are not likely to be a newly acquired feature in vertebrates, but may have already been possessed by the earliest chordates.