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In Xenopus, what does ventral mesoderm give rise to? Dorsal mesoderm?
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Ventral -lateral plate mesodermdorsal - somites and notochords
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Where does gastrulation occur in xenopus?
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Gastrulation occurs in the grey crescent, and the opening that forms is called the doral blastopore lip
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What is the process called by which gastrulation occurs?
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Epiboly
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What would happen if you transplanted dorsal blastopore lip to an ectopic location on an embryo?
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You would get a second involution, and you would get a new set of notochords and somites. Later in development you get a complete new embryo!!
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What are the four criteria that a dorsal blastopore lip/organizer has?
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1) ability to become dorsal mesoderm2) ability to dorsalize surrounding mesoderm3)abilitiy to dorsalize surrounding ectoderm (makes it neural not skin)4) abilitiy to initiate gastrulation
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What signals come from the vegetal pole to the animal pole to induce the mesoderm in a sandwich like formation?
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Vg1, Activin, FGFof these, only Vg 1 was actually working in vivo!
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What two factors specify general mesoderm?
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Vg1 and VegT
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What is the name of the dorsal endoderm cell that is responsible for inducing dorsal mesoderm formation?
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Nieuwkoop centre. Dorsal most vegetal blastomere. Induces the organizer!!!!!
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How did they prove that cortical rotation is vital when specifying dorsal mesoderm?
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They shined UV light on embryos which effectively prevents MT formation and cortical rotation was blocked. They only got ventral tissues. They then did the same thing to an embryo and transplanted dorsal vegetal cells that had undergone cortical rotation from another embryo and observed dorsal mesoderm formation.
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What maternal determinants move up with cortical rotation?
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Dishevelled, Wnt 11
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What is the first zygotic gene that is important in specifying dorsal mesoderm? What does it have in its promoter region?
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Siamois!Has beta catenin sites in promotore.
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What is Siamois, what does it help transcribe? Is it sufficient to transcribe GSc?
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Siamois is a TF and it is vital for goosecoid transcription. It is not sufficient to transcribe goosecoid. You need siamois and also Vg1 which is part of the TGFbeta family and it will induce that.
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What three tissues is the blastula composed of?
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Animal cap (blue), vegetal cells (yellow), mesoderm (red)
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What is the nodal gradient in xenopus mesoderm? Why does it have this expression pattern?
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Xnr (nodal related gene) - it is a TGFbeta, in vegetal region, expressed more in dorsal end. it has this expression pattern because of beta catenin. High beta catenin = high xnr. Therefore, nodal high in dorsal and low in ventral.
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What exactly is goosecoid?
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Goosecoid is a transcriptional repressor to downregulate ventral mesoderm.
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