Search results for "Gastrula"

Axis Specification in Zebrafish Is Robust to Cell Mixing and Reveals a Regulation of Pattern Formation by Morphogenesis

2020

Summary A fundamental question in developmental biology is how the early embryo establishes the spatial coordinate system that is later important for the organization of the embryonic body plan. Although we know a lot about the signaling and gene-regulatory networks required for this process, much less is understood about how these can operate to pattern tissues in the context of the extensive cell movements that drive gastrulation. In zebrafish, germ layer specification depends on the inheritance of maternal mRNAs [1, 2, 3], cortical rotation to generate a dorsal pole of β-catenin activity [4, 5, 6, 7, 8], and the release of Nodal signals from the yolk syncytial layer (YSL) [9, 10, 11, 12]…

2018

During gastrulation, embryonic cells become specified into distinct germ layers. In mouse, this continues throughout somitogenesis from a population of bipotent stem cells called neuromesodermal progenitors (NMps). However, the degree of self-renewal associated with NMps in the fast-developing zebrafish embryo is unclear. With a genetic clone tracing method, we labelled early embryonic progenitors and find a strong clonal similarity between spinal cord and mesoderm tissues. We followed individual cell lineages by light-sheet imaging, revealing a common neuromesodermal lineage contribution to a subset of spinal cord tissue across the anterior-posterior body axis. An initial population subdiv…

Self-organised symmetry breaking in zebrafish reveals feedback from morphogenesis to pattern formation

2019

A fundamental question in developmental biology is how the early embryo breaks initial symmetry to establish the spatial coordinate system later important for the organisation of the embryonic body plan. In zebrafish, this is thought to depend on the inheritance of maternal mRNAs [1–3], cortical rotation to generate a dorsal pole of beta-catenin activity [4–8] and the release of Nodal signals from the yolk syncytial layer (YSL) [9–12]. Recent work aggregating mouse embryonic stem cells has shown that symmetry breaking can occur in the absence of extra-embryonic tissue [19,20]. To test whether this is also true in zebrafish, we separated embryonic cells from the yolk and allowed them to deve…

Correction

2019

ABSTRACT During gastrulation, embryonic cells become specified into distinct germ layers. In mouse, this continues throughout somitogenesis from a population of bipotent stem cells called neuromesodermal progenitors (NMps). However, the degree of self-renewal associated with NMps in the fast-developing zebrafish embryo is unclear. Using a genetic clone-tracing method, we labelled early embryonic progenitors and found a strong clonal similarity between spinal cord and mesoderm tissues. We followed individual cell lineages using light-sheet imaging, revealing a common neuromesodermal lineage contribution to a subset of spinal cord tissue across the anterior-posterior body axis. An initial pop…

Neuromesodermal Progenitors are a Conserved Source of Spinal Cord with Divergent Growth Dynamics

2018

AbstractDuring gastrulation, embryonic cells become specified into distinct germ layers. In mouse, this continues throughout somitogenesis from a population of bipotent stem cells called neuromesodermal progenitors (NMps). However, the degree self-renewal is associated with NMps in the fast-developing zebrafish embryo is unclear. With a genetic clone tracing method, we labelled early embryonic progenitors and find a strong clonal similarity between spinal cord and mesoderm tissues. We then followed individual cell lineages by light-sheet imaging and reveal a common neuromesodermal lineage contribution to a subset of spinal cord tissue across the anterior-posterior body axis. An initial popu…

The dynamics of structural modifications of mitochondria at the early stages of sea urchin embryonic development

1992

The organization of the chondriome and the ultrastructure of mitochondria have been studied in eggs and embryos of the sea urchin Paracentrotus lividus. The egg chondriome is characterized by an arrangement in well-delimited clusters. Analysis of mitochondrial clusters on electron micrographs of ultrathin serial sections shows two kinds of mitochondria of different shapes, the rod-shaped and the spherical. The egg mitochondria have a dense matrix and a well-ordered arrangement of cristae which, in rod-shaped variety, are perpendicular to the major axis. Cell division is accompanied by significant changes in intracellular distribution of mitochondria and in their structure. At the stage of 2…

Tenectin, a novel extracellular matrix protein expressed during Drosophila melanogaster embryonic development

2006

1567-133X (Print) Journal Article Research Support, Non-U.S. Gov't; During Drosophila embryonic development, various morphogenetic processes require the remodeling of the extracellular matrix. In a previous study, we have identified and characterized a cDNA encoding a novel putative extracellular matrix protein named tenebrin, in the beetle Tenebrio molitor. Here, we examine the expression of the Drosophila ortholog, referred to as Tenectin (Tnc), during embryonic development. Tnc is expressed in the majority of tissues of neuroectodermic origin such as hindgut, foregut, tracheal system, anal plate, and CNS. In the CNS, the Tnc transcript is restricted to a few cells, whereas the protein is…

A common precursor for glia and neurons in the embryonic CNS of Drosophila gives rise to segment-specific lineage variants

1993

ABSTRACT The nervous system consists of two classes of cells, neurons and glia, which differ in morphology and function. They derive from precursors located in the neurogenic region of the ectoderm. In this study, we present the complete embryonic lineage of a neuroectodermal precursor in Drosophila that gives rise to neurons as well as glia in the abdominal CNS. This lineage is conserved among different Drosophila species. We show that neuronal and glial cell types in this clone derive from one segregating precursor, previously described as NB1-1. Thus, in addition to neuroblasts and glioblasts, there exists a third class of CNS precursors in Drosophila, which we call neuroglioblasts. We f…

Commitment of CNS Progenitors Along the Dorsoventral Axis of Drosophila Neuroectoderm

1995

In the Drosophila embryo, the central nervous system (CNS) develops from a population of neural stem cells (neuroblasts) and midline progenitor cells. Here, the fate and extent of determination of CNS progenitors along the dorsoventral axis was assayed. Dorsal neuroectodermal cells transplanted into the ventral neuroectoderm or into the midline produced CNS lineages consistent with their new position. However, ventral neuroectodermal cells and midline cells transplanted to dorsal sites of the neuroectoderm migrated ventrally and produced CNS lineages consistent with their origin. Thus, inductive signals at the ventral midline and adjacent neuroectoderm may confer ventral identities to CNS p…

The origin of postembryonic neuroblasts in the ventral nerve cord of Drosophila melanogaster.

1991

ABSTRACT Embryonic and postembryonic neuroblasts in the thoracic ventral nerve cord of Drosophila melanogaster have the same origin. We have traced the development of threefold-labelled single precursor cells from the early gastrula stage to late larval stages. The technique allows in the same individual monitoring of progeny cells at embryonic stages (in vivo) and differentially staining embryonic and postembryonic progeny within the resulting neural clone at late postembryonic stages. The analysis reveals that postembryonic cells always appear together with embryonic cells in one clone. Further-more, BrdU labelling suggests that the embryonic neuroblast itself rather than one of its proge…