Asymmetric Mbc, active Rac1 and F-actin foci in the fusion-competent myoblasts during myoblast fusion in Drosophila

Development ◽  
2013 ◽  
Vol 140 (6) ◽  
pp. 1370-1371
Author(s):  
S. Haralalka ◽  
C. Shelton ◽  
H. N. Cartwright ◽  
E. Katzfey ◽  
E. Janzen ◽  
...  
Keyword(s):  
Myoblast Fusion ◽  
Fusion Competent Myoblasts

scholarly journals A distinct set of founders and fusion-competent myoblasts make visceral muscles in the Drosophila embryo

Development ◽  
2001 ◽  
Vol 128 (17) ◽  
pp. 3331-3338 ◽  
Author(s):  
Beatriz San Martin ◽  
Mar Ruiz-Gómez ◽  
Matthias Landgraf ◽  
Michael Bate
Keyword(s):  
Myoblast Fusion ◽  
Drosophila Embryo ◽  
Visceral Muscle ◽  
Visceral Muscles ◽  
Fusion Competent Myoblasts ◽  
Longitudinal Muscles ◽  
Two Populations ◽  
Somatic Muscles

The embryonic Drosophila midgut is enclosed by a latticework of longitudinal and circular visceral muscles. We find that these muscles are syncytial. Like the somatic muscles they are generated by the prior segregation of two populations of cells: fusion-competent myoblasts and founder myoblasts specialised to seed the formation of particular muscles. Visceral muscle founders are of two classes: those that seed circular muscles and those that seed longitudinal muscles. These specialisations are revealed in mutant embryos where myoblast fusion fails. In the absence of fusion, founders make mononucleate circular or longitudinal fibres, while their fusion-competent neighbours remain undifferentiated.

scholarly journals The control of chick myoblast fusion by ion channels operated by prostaglandins and acetylcholine.

1988 ◽  
Vol 106 (5) ◽  
pp. 1693-1702 ◽  
Author(s):  
A Entwistle ◽  
R J Zalin ◽  
S Bevan ◽  
A E Warner
Keyword(s):  
Acetylcholine Receptor ◽  
Myoblast Fusion ◽  
Chloride Ions ◽  
Calcium Flux ◽  
Extracellular Potassium ◽  
Ca Channel ◽  
High Potassium ◽  
Calcium Permeability ◽  
Fusion Competent Myoblasts ◽  
Alpha Bungarotoxin

Chick myoblast fusion in culture was investigated using prostanoid synthesis inhibitors to delay spontaneous fusion. During this delay myoblast fusion could be induced by prostaglandin E1 (PGE1), by raising extracellular potassium and by addition of carbachol. Carbachol-induced fusion, but not PGE-induced fusion, was prevented by the acetylcholine receptor blocker alpha-bungarotoxin. Fusion induced by any of these agents was prevented by the Ca channel blockers lanthanum and D600. The threshold for potassium-induced fusion was 7-8 mM; maximal fusion occurred at 16-20 mM. Low extracellular potassium inhibited spontaneous fusion. Intracellular potassium in fusion competent myoblasts was 101 m-moles/l cell. Calcium flux measurements demonstrated that high potassium increased calcium permeability in fusion-competent myoblasts. A 30-s exposure to high potassium or PGE1 was sufficient to initiate myoblast fusion. Anion-exchange inhibitors (SITS and DIDS) delayed spontaneous myoblast fusion and blocked fusion induced by PGE1 but not carbachol. Blocking the acetylcholine receptor shifted the dose-response relation for PGE-induced fusion to higher concentrations. PGE1-induced fusion required chloride ions; carbachol-induced fusion required sodium ions. Provided calcium channels were available, potassium always induced fusion. We conclude that myoblasts possess at least three, independent pathways, each of which can initiate myoblast fusion and that the PGE-activated pathway and the acetylcholine receptor-activated pathway act synergistically. We suggest that fusion competent myoblasts have a high resting membrane potential and that fusion is controlled by depolarization initiated directly (potassium), by an increase in permeability to chloride ions (PGE), or by activation of the acetylcholine receptor (carbachol); depolarization triggers a rise in calcium permeability. The consequent increase in intracellular calcium initiates myoblast fusion.

scholarly journals Asymmetric Mbc, active Rac1 and F-actin foci in the fusion-competent myoblasts during myoblast fusion in Drosophila

Development ◽  
2011 ◽  
Vol 138 (8) ◽  
pp. 1551-1562 ◽  
Author(s):  
S. Haralalka ◽  
C. Shelton ◽  
H. N. Cartwright ◽  
E. Katzfey ◽  
E. Janzen ◽  
...  
Keyword(s):  
Myoblast Fusion ◽  
Fusion Competent Myoblasts

myoblasts incompetent encodes a zinc finger transcription factor required to specify fusion-competent myoblasts in Drosophila

Development ◽  
2002 ◽  
Vol 129 (1) ◽  
pp. 133-141 ◽  
Author(s):  
Mar Ruiz-Gómez ◽  
Nikola Coutts ◽  
Maximiliano L. Suster ◽  
Matthias Landgraf ◽  
Michael Bate
Keyword(s):  
Transcription Factor ◽  
Zinc Finger ◽  
Myoblast Fusion ◽  
Loss Of Function ◽  
Cubitus Interruptus ◽  
Zinc Finger Transcription Factor ◽  
General Pathway ◽  
Twist Expression ◽  
Fusion Competent Myoblasts ◽  
Normal Differentiation

We report a new gene, myoblasts incompetent, essential for normal myogenesis and myoblast fusion in Drosophila. myoblasts incompetent encodes a putative zinc finger transcription factor related to vertebrate Gli proteins and to Drosophila Cubitus interruptus. myoblasts incompetent is expressed in immature somatic and visceral myoblasts. Expression is predominantly in fusion-competent myoblasts and a loss-of-function mutation in myoblasts incompetent leads to a failure in the normal differentiation of these cells and a complete lack of myoblast fusion. In the mutant embryos, founder myoblasts differentiate normally and form mononucleate muscles, but genes that are specifically expressed in fusion-competent cells are not activated and the normal downregulation of twist expression in these cells fails to occur. In addition, fusion-competent myoblasts fail to express proteins characteristic of the general pathway of myogenesis such as myosin and Dmef2. Thus myoblasts incompetent appears to function specifically in the general pathway of myogenesis to control the differentiation of fusion-competent myoblasts.

Changes in phospholipid metabolism dependent on calcium-regulated myoblast fusion

1988 ◽  
Vol 66 (10) ◽  
pp. 1110-1118 ◽  
Author(s):  
Victor S. Sauro ◽  
Gregory A. Brown ◽  
Michael R. Hamilton ◽  
Craig K. Strickland ◽  
Kenneth P. Strickland
Keyword(s):  
Calcium Content ◽  
Phospholipid Metabolism ◽  
Myoblast Fusion ◽  
Myoblast Differentiation ◽  
Phospholipid Content ◽  
Phospholipid Synthesis ◽  
Normal Medium ◽  
Low Calcium ◽  
High Calcium ◽  
Fusion Competent Myoblasts

Fusion-competent myoblasts can be prevented from fusing (differentiating) by reducing medium calcium concentrations from 1.65 mM to less than 50 μM. Fusion is completely retarded after 24 h but is noticeable after 48 h and significant after 72 h in low-calcium medium. After 24 h in low-calcium medium, a rapid, synchronous fusion can be initiated by return to normal (high-calcium) medium. Calcium content increases over threefold during myoblast differentiation and closely parallels the fusion process. Phospholipid content is also dependent upon the state of differentiation. Myotubes (fused myoblasts) have an almost twofold greater content of lipid phosphate per milligram of protein compared with that of myoblasts; this increase is localized to increased contents of phosphatidylcholine and pooled phosphatidylinositol – phosphatidylserine. Phospholipid synthesis (32Pi incorporation) is markedly stimulated four- to five-fold when myoblasts grown in low-calcium medium are switched to normal medium. These significant increases are observed in all the major phospholipids studied, predominantly in phosphatidylcholine and pooled phosphatidylinositol – phosphatidylserine, and most noticeably in phosphatidylinositol 4,5-bisphosphate. Furthermore, we show that phosphatidylinositol 4,5-bisphosphate prelabelled with myo-[2-3H]inositol is rapidly degraded after switching from low-calcium medium to normal medium. These changes are not observed in myotubes treated similarly, which suggests that the changes in phospholipid metabolism may be fusion related. These results support a proposal by another author, which suggests that phosphatidylinositol 4,5-bisphosphate breakdown may play an important regulating role in myoblast differentiation.

The immunoglobulin-like protein Hibris functions as a dose-dependent regulator of myoblast fusion and is differentially controlled by Ras and Notch signaling

Development ◽  
2001 ◽  
Vol 128 (21) ◽  
pp. 4251-4264 ◽  
Author(s):  
Ruben D. Artero ◽  
Irinka Castanon ◽  
Mary K. Baylies
Keyword(s):  
Cell Membrane ◽  
Temporal Pattern ◽  
Human Kidney ◽  
Myoblast Fusion ◽  
Ras Signaling ◽  
Visceral Mesoderm ◽  
Functional Differences ◽  
Fusion Competent Myoblasts ◽  
Dose Dependent

Hibris (Hbs) is a transmembrane immunoglobulin-like protein that shows extensive homology to Drosophila Sticks and stones (Sns) and human kidney protein Nephrin. Hbs is expressed in embryonic visceral, somatic and pharyngeal mesoderm among other tissues. In the somatic mesoderm, Hbs is restricted to fusion competent myoblasts and is regulated by Notch and Ras signaling pathways. Embryos that lack or overexpress hbs show a partial block of myoblast fusion, followed by abnormal muscle morphogenesis. Abnormalities in visceral mesoderm are also observed. In vivo mapping of functional domains suggests that the intracellular domain mediates Hbs activity. Hbs and its paralog, Sns, co-localize at the cell membrane of fusion-competent myoblasts. The two proteins act antagonistically: loss of sns dominantly suppresses the hbs myoblast fusion and visceral mesoderm phenotypes, and enhances Hbs overexpression phenotypes. Data from a P-homed enhancer reporter into hbs and co-localization studies with Sns suggest that hbs is not continuously expressed in all fusion-competent myoblasts during the fusion process. We propose that the temporal pattern of hbs expression within fusion-competent myoblasts may reflect previously undescribed functional differences within this myoblast population.

Characterization ofDrosophila hibris, a gene related to human nephrin

Development ◽  
2001 ◽  
Vol 128 (21) ◽  
pp. 4265-4276 ◽  
Author(s):  
Heather A. Dworak ◽  
Michael A. Charles ◽  
Lidia B. Pellerano ◽  
Helen Sink
Keyword(s):  
Muscle Development ◽  
Attachment Site ◽  
Cell Aggregation ◽  
Myoblast Fusion ◽  
Immunoglobulin Superfamily ◽  
Somatic Muscle ◽  
Muscle Insertion ◽  
Fusion Competent Myoblasts ◽  
Cns Midline ◽  
Heterotypic Interaction

Hibris encodes a protein that is a newly identified member of the immunoglobulin superfamily and has homology to vertebrate Nephrins and Drosophila Sticks-and-Stones. The Hibris protein has eight Ig-like domains, a fibronectin domain and a 160 amino acid cytoplasmic tail. The hibris transcript is expressed in a broad range of tissues and across life stages. In the embryo, hibris transcript is present in the mesectoderm, then in a group of cells at the developing CNS midline and in a subset of glia. In the periphery, hibris is expressed by fusion competent myoblasts and the epidermal muscle attachment site cells. Deletion analyses show that loss of hibris does not visibly affect embryonic CNS or somatic muscle development. However overexpressing hibris in the somatic mesoderm disrupts myoblast fusion. Furthermore, when overexpressed in the epidermis, Hibris causes comprehensive derangement of muscle insertion locations. A similar myoblast fusion defect is observed when the Drosophila homologs of DM-GRASP/BEN/SC1 (irregular chiasm-roughest and dumbfounded) are deleted together. Our S2 cell aggregation assays have revealed a heterotypic interaction between Hibris and Dumbfounded, but not between Hibris and Irregular Chiasm-Roughest. We propose that Hibris is an extracellular partner for Dumbfounded and potentially mediates the response of myoblasts to this attractant.

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