Overexpression of osr1 causes expansion of pronephric progenitor number and a reduction in angioblast number. Control embryos (A,C) and embryos injected with 100 pg of osr1 mRNA (B,D). (A) Control expression of pax2a is expanded after injection of osr1 mRNA (B), specifically in the mid-portion of the IM (arrowhead, B), which is normally downregulated in the control embryos at the 13-somite stage (arrowhead, A). myoD is used as an internal control for somite staging in these embryos (A,B). (C,D) Expression of scl is lost in the anterior lateral plate mesoderm (arrowhead, D) in the embryos injected with osr1 mRNA when compared with the uninjected controls (arrowhead, C).
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