Id3 depletion leads to a loss of neural crest progenitors. ( A ) Morpholino antisense oligo sequence (Id3-MO) corresponding to a region 5′ upstream of the Id3 start codon (25 bp; -8 to -32) and its control oligo (control-MO) with seven mismatches (red letters). ( B ) Id3 protein synthesis was monitored in the absence of oligo (no MO) or in the presence of morpholino oligos (control, Id3 or Id2 oligo) in an in vitro translation system. Only Id3-MO specifically blocks Id3 protein translation. ( C ) Neurula-stage embryos injected with control-MO or Id3-MO. (Panel a ) slug expression (arrow) is intact on the side injected with control-MO (C-MO, Red-Gal). (Panels b - d ) Embryos injected with Id3-MO show the loss of early neural crest markers (arrows) on the injected side, which is marked by Red-Gal staining: slug (panel b ), sox10 (panel c ), and foxD3 (panel d ). ( D ) slug expression is not affected by Id2 depletion (arrow). ( E ) The loss of neural crest progenitors by Id3 depletion (panel a ) is rescued in the presence of chick Id3 (panels b,c ).
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