Skeletal Myogenesis: The Preferred Pathway of Chick Embryo Epiblast Cellsin Vitro

George‐Weinstein, Mindy; Gerhart, Jacquelyn; Reed, Rebecca; Flynn, Joseph M.; Callihan, Beth; Mattiacci, M.; Miehle, Carolyn; Foti, Gerard; Lash, James W.; Weintraub, Harold

doi:10.1006/dbio.1996.0023

Cited by 85 publications

(75 citation statements)

References 8 publications

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“…Furthermore cell dissociation of chick epiblast does not induce neural differentiation but rather muscle (George-Weinstein et al, 1996;George-Weinstein et al, 1997). Consistent with these results in the chick, mouse mutants that lack Chordin, Noggin or both BMP antagonists still have a nervous system, although they lack the most anterior structures (McMahon et al, 1998;Bachiller et al, 2000;Belo et al, 2000;Mukhopadhyay et al, 2001).…”

Section: Conflicting Data From Chick and Other Speciessupporting

confidence: 68%

Neural induction requires BMP inhibition only as a late step, and involves signals other than FGF and Wnt antagonists

2004

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A dominant molecular explanation for neural induction is the `default model', which proposes that the ectoderm is pre-programmed towards a neural fate, but is normally inhibited by endogenous BMPs. Although there is strong evidence favouring this in Xenopus, data from other organisms suggest more complexity, including an involvement of FGF and modulation of Wnt. However, it is generally believed that these additional signals also act by inhibiting BMPs. We have investigated whether BMP inhibition is necessary and/or sufficient for neural induction. In the chick, misexpression of BMP4 in the prospective neural plate inhibits the expression of definitive neural markers (Sox2 and late Sox3), but does not affect the early expression of Sox3, suggesting that BMP inhibition is required only as a late step during neural induction. Inhibition of BMP signalling by the potent antagonist Smad6, either alone or together with a dominant-negative BMP receptor, Chordin and/or Noggin in competent epiblast is not sufficient to induce expression of Sox2 directly, even in combination with FGF2,FGF3, FGF4 or FGF8 and/or antagonists of Wnt signalling. These results strongly suggest that BMP inhibition is not sufficient for neural induction in the chick embryo. To test this in Xenopus, Smad6 mRNA was injected into the A4 blastomere (which reliably contributes to epidermis but not to neural plate or its border) at the 32-cell stage: expression of neural markers (Sox3 and NCAM) is not induced. We propose that neural induction involves additional signalling events that remain to be identified.

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Section: Conflicting Data From Chick and Other Speciessupporting

confidence: 68%

Neural induction requires BMP inhibition only as a late step, and involves signals other than FGF and Wnt antagonists

2004

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“…Interestingly, Wnt5b, its putative receptor Fz7 and MyoD are co-expressed in somitic cells. Although this could suggest that Wnt5b mediates its myogenic activity in an cell autonomous fashion, the observation (1) that myogenic differentiation is more conspicuous if presomitic mesoderm cells are cultured at high density (George-Weinstein et al, 1997;George-Weinstein et al, 1996), and (2) that MyoD expression was observed in the present work in groups, rather than isolated presomitic cells, suggests on the contrary that Wnt5b might act in a non cellautonomous fashion.…”

Section: Discussioncontrasting

confidence: 55%

Intrinsic signals regulate the initial steps of myogenesis in vertebrates

et al. 2003

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presomitic mesoderm, represents the MyoD-activating cue. Despite Wnt5b expression in the presomitic mesoderm, MyoD is not expressed in this tissue: our experiments demonstrate that this is due to a Bmp inhibitory signal that prevents the premature expression of MyoD before somites form. Our results indicate that myogenesis is a multistep process which is initiated prior to somite formation in a mesoderm-autonomous fashion; as somites form, influences from adjacent tissues are likely to be required for maintenance and patterning of early muscles.

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“…The observation that chick epiblast cells activate MyoD after dissociation in culture, has led to the suggestion that myogenesis is normally repressed in the embryo (George-Weinstein et al, 1996) (see Cossu et al, 1996;Currie and Ingham, 1998). Interestingly, perturbation of ␤1 integrin-laminin interaction has been shown to lead to precocious differentiation in other systems.…”

Section: Inhibition Of ␣ ␣6␤ ␤1-laminin Binding Leads To Activation Omentioning

confidence: 99%

Integrin α6β1-laminin interactions regulate early myotome formation in the mouse embryo

et al. 2006

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We addressed the potential role of cell-laminin interactions during epaxial myotome formation in the mouse embryo. Assembly of the myotomal laminin matrix occurs as epaxial myogenic precursor cells enter the myotome. Most Myf5-positive and myogeninnegative myogenic precursor cells localise near assembled laminin, while myogenin-expressing cells are located either away from this matrix or in areas where it is being assembled. In Myf5 nlacZ/nlacZ (Myf5-null) embryos, laminin, collagen type IV and perlecan are present extracellularly near myogenic precursor cells, but do not form a basement membrane and cells are not contained in the myotomal compartment. Unlike wild-type myogenic precursor cells, Myf5-null cells do not express the ␣6␤1 integrin, a laminin receptor, suggesting that integrin ␣6␤1-laminin interactions are required for myotomal laminin matrix assembly. Blocking ␣6␤1-laminin binding in cultured wild-type mouse embryo explants resulted in dispersion of Myf5-positive cells, a phenotype also seen in Myf5 nlacZ/nlacZ embryos. Furthermore, inhibition of ␣6␤1 resulted in an increase in Myf5 protein and ectopic myogenin expression in dermomyotomal cells, suggesting that ␣6␤1-laminin interactions normally repress myogenesis in the dermomyotome. We conclude that Myf5 is required for maintaining ␣6␤1 expression on myogenic precursor cells, and that ␣6␤1 is necessary for myotomal laminin matrix assembly and cell guidance into the myotome. Engagement of laminin by ␣6␤1 also plays a role in maintaining the undifferentiated state of cells in the dermomyotome prior to their entry into the myotome.

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Skeletal Myogenesis: The Preferred Pathway of Chick Embryo Epiblast Cellsin Vitro

Cited by 85 publications

References 8 publications

Neural induction requires BMP inhibition only as a late step, and involves signals other than FGF and Wnt antagonists

Neural induction requires BMP inhibition only as a late step, and involves signals other than FGF and Wnt antagonists

Intrinsic signals regulate the initial steps of myogenesis in vertebrates

Integrin α6β1-laminin interactions regulate early myotome formation in the mouse embryo

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