CNS midline cells in Drosophila induce the differentiation of lateral neural cells

Cells located at the midline of the developing central nervous system perform a number of conserved functions during the establishment of the lateral CNS. The midline cells of the Drosophila CNS were previously shown to be required for correct pattern formation in the ventral ectoderm and for the induction of specific mesodermal cells. Here we investigated whether the midline cells are required for the correct development of lateral CNS cells as well. Embryos that lack midline cells through genetic ablation show a 15% reduction in the number of cortical CNS cells. A similar thinning of the ventral nerve cord can be observed following mechanical ablation of the midline cells. We have identified a number of specific neuronal and glial cell markers that are reduced in CNS midline-less embryos (in single-minded embryos, in early heat-shocked Notch(ts1) embryos or in embryos where we mechanically ablated the midline cells). Genetic data suggest that both neuronal and glial midline cell lineages are required for differentiation of lateral CNS cells. We could rescue the lateral CNS phenotype of single-minded mutant embryos by transplantation of midline cells as well as by homotopic expression of single-minded, the master gene for midline development. Furthermore, ectopic midline cells are able to induce enhanced expression of some lateral CNS cell markers. We thus conclude that the CNS midline plays an important role in the differentiation or maintenance of the lateral CNS cortex.

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Induction of identified mesodermal cells by CNS midline progenitors in Drosophila

Development ◽

10.1242/dev.124.14.2681 ◽

1997 ◽

Vol 124 (14) ◽

pp. 2681-2690 ◽

Cited By ~ 4

Author(s):

K. Luer ◽

J. Urban ◽

C. Klambt ◽

G.M. Technau

Keyword(s):

Progenitor Cells ◽

Ventral Nerve Cord ◽

Early Embryo ◽

Absolute Concentration ◽

Cell Lineages ◽

Cell Ablation ◽

Inductive Effects ◽

Cns Midline ◽

Midline Cells ◽

Transplantation Experiments

The Drosophila ventral midline cells generate a discrete set of CNS lineages, required for proper patterning of the ventral ectoderm. Here we provide the first evidence that the CNS midline cells also exert inductive effects on the mesoderm. Mesodermal progenitors adjacent to the midline progenitor cells give rise to ventral somatic mucles and a pair of unique cells that come to lie dorsomedially on top of the ventral nerve cord, the so-called DM cells. Cell ablation as well as cell transplantation experiments indicate that formation of the DM cells is induced by midline progenitors in the early embryo. These results are corroborated by genetic analyses. Mutant single minded embryos lack the CNS midline as well as the DM cells. Embryos mutant for any of the spitz group genes, which primarily express defects in the midline glial cell lineages, show reduced formation of the DM cells. Conversely, directed overexpression of secreted SPITZ by some or all CNS midline cells leads to the formation of additional DM cells. Furthermore we show that DM cell development does not depend on the absolute concentration of a local inductor but appears to require a graded source of an inducing signal. Thus, the Drosophila CNS midline cells play a central inductive role in patterning the mesoderm as well as the underlying ectoderm.

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Regulation of bHLH-PAS protein subcellular localization during Drosophila embryogenesis

Development ◽

10.1242/dev.125.9.1599 ◽

1998 ◽

Vol 125 (9) ◽

pp. 1599-1608 ◽

Cited By ~ 5

Author(s):

M.P. Ward ◽

J.T. Mosher ◽

S.T. Crews

Keyword(s):

Subcellular Localization ◽

Nuclear Localization ◽

Ectopic Expression ◽

Nuclear Accumulation ◽

Salivary Duct ◽

Cell Lineages ◽

Basic Helix Loop Helix ◽

Helix Loop Helix ◽

Cns Midline ◽

Midline Cells

The Drosophila Single-minded and Tango basic-helix-loop-helix-PAS protein heterodimer controls transcription and embryonic development of the CNS midline cells, while the Trachealess and Tango heterodimer controls tracheal cell and salivary duct transcription and development. Expression of both single-minded and trachealess is highly restricted to their respective cell lineages, however tango is broadly expressed. The developmental control of subcellular localization of these proteins is investigated because of their similarity to the mammalian basic-helix-loop-helix-PAS Aromatic hydrocarbon receptor whose nuclear localization is dependent on ligand binding. Confocal imaging of Single-minded and Trachealess protein localization indicate that they accumulate in cell nuclei when initially synthesized in their respective cell lineages and remain nuclear throughout embryogenesis. Ectopic expression experiments show that Single-minded and Trachealess are localized to nuclei in cells throughout the ectoderm and mesoderm, indicating that nuclear accumulation is not regulated in a cell-specific fashion and unlikely to be ligand dependent. In contrast, nuclear localization of Tango is developmentally regulated; it is localized to the cytoplasm in most cells except the CNS midline, salivary duct, and tracheal cells where it accumulates in nuclei. Genetic and ectopic expression experiments indicate that Tango nuclear localization is dependent on the presence of a basic-helix-loop-helix-PAS protein such as Single-minded or Trachealess. Conversely, Drosophila cell culture experiments show that Single-minded and Trachealess nuclear localization is dependent on Tango since they are cytoplasmic in the absence of Tango. These results suggest a model in which Single-minded and Trachealess dimerize with Tango in the cytoplasm of the CNS midline cells and trachea, respectively, and the dimeric complex accumulates in nuclei in a ligand-independent mode and regulates lineage-specific transcription. The lineage-specific action of Single-minded and Trachealess derives from transcriptional activation of their genes in their respective lineages, not from extracellular signaling.

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Sim2 Mutants Have Developmental Defects Not Overlapping with Those of Sim1 Mutants

Molecular and Cellular Biology ◽

10.1128/mcb.22.12.4147-4157.2002 ◽

2002 ◽

Vol 22 (12) ◽

pp. 4147-4157 ◽

Cited By ~ 38

Author(s):

Eleni Goshu ◽

Hui Jin ◽

Rachel Fasnacht ◽

Mike Sepenski ◽

Jacques L. Michaud ◽

...

Keyword(s):

Genetic Interaction ◽

Expression Patterns ◽

Gene Mutations ◽

Congenital Scoliosis ◽

Developmental Defects ◽

Lung Inflation ◽

Left And Right ◽

Temporal And Spatial ◽

Cns Midline ◽

Midline Cells

ABSTRACT The mouse genome contains two Sim genes, Sim1 and Sim2. They are presumed to be important for central nervous system (CNS) development because they are homologous to the Drosophila single-minded (sim) gene, mutations in which cause a complete loss of CNS midline cells. In the mammalian CNS, Sim2 and Sim1 are coexpressed in the paraventricular nucleus (PVN). While Sim1 is essential for the development of the PVN (J. L. Michaud, T. Rosenquist, N. R. May, and C.-M. Fan, Genes Dev. 12:3264-3275, 1998), we report here that Sim2 mutant has a normal PVN. Analyses of the Sim1 and Sim2 compound mutants did not reveal obvious genetic interaction between them in PVN histogenesis. However, Sim2 mutant mice die within 3 days of birth due to lung atelectasis and breathing failure. We attribute the diminished efficacy of lung inflation to the compromised structural components surrounding the pleural cavity, which include rib protrusions, abnormal intercostal muscle attachments, diaphragm hypoplasia, and pleural mesothelium tearing. Although each of these structures is minimally affected, we propose that their combined effects lead to the mechanical failure of lung inflation and death. Sim2 mutants also develop congenital scoliosis, reflected by the unequal sizes of the left and right vertebrae and ribs. The temporal and spatial expression patterns of Sim2 in these skeletal elements suggest that Sim2 regulates their growth and/or integrity.

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A multi-stem cell basis for craniosynostosis and calvarial mineralization

10.21203/rs.3.rs-1061838/v1 ◽

2021 ◽

Author(s):

Matthew Greenblatt ◽

Seoyeon Bok ◽

Alisha Yallowitz ◽

Jason McCormick ◽

Michelle Cung ◽

...

Keyword(s):

Stem Cell ◽

Endochondral Ossification ◽

Distinct Form ◽

Therapeutic Approaches ◽

Genetic Ablation ◽

Cell Lineages ◽

Specific Fraction ◽

Maladaptive Response ◽

Suture Fusion ◽

Stem Cell Populations

Abstract Craniosynostosis is a group of disorders of premature calvarial sutural fusion. An incomplete understanding of the calvarial stem cells (CSCs) that produce fusion-driving osteoblasts has limited the development of non-surgical therapeutic approaches for craniosynostosis. Here we show that both physiologic calvarial mineralization and pathologic calvarial fusion in craniosynostosis reflect the interaction of two separate stem cell lineages; a recently reported CathepsinK (CTSK) lineage CSC (CTSK+ CSC)1 and a separate Discoidin domain-containing receptor 2 (DDR2) lineage stem cell (DDR2+ CSC) identified in this study. Deletion of Twist1, a gene associated with human craniosynostosis2,3, solely in CTSK+ CSCs is sufficient to drive craniosynostosis, however the sites destined to fuse surprisingly display a marked depletion of CTSK+ CSCs and a corresponding expansion of DDR2+ CSCs. This DDR2+ CSC expansion is a direct maladaptive response to CTSK+ CSC depletion, as partial suture fusion occurred after genetic ablation of CTSK+ CSCs. This DDR2+ CSC is a specific fraction of DDR2+ lineage cells that displayed full stemness features, establishing the presence of two distinct stem cell lineages in the sutures, with each population contributing to physiologic calvarial mineralization. DDR2+ CSCs mediate a distinct form of endochondral ossification where an initial cartilage template is formed but the recruitment of hematopoietic marrow is absent. Direct implantation of DDR2+ CSCs into suture sites was sufficient to induce fusion, and this phenotype was prevented by co-transplantation of CTSK+ CSCs. Lastly, the human counterparts of DDR2+ CSCs and CTSK+ CSCs are present in calvarial surgical specimens and display conserved functional properties in xenograft assays. The interaction between these two stem cell populations provides a new biologic interface to modulate calvarial mineralization and suture patency.

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