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Figure 2. Examples of changes in gene expression of putative Six1 targets after knock-down of endogenous Six1 levels by injection of antisense morpholino oligonucleotides (Six1 MOs), increased levels of wild-type Six1 by mRNA injection (Six1 WT), activation of Six1 targets by mRNA injection of an activating construct (Six1-VP16), or repression of Six1 targets by mRNA injection of a repressive construct (EnR-Six1) (see Brugmann et al., 2004 for validation of these constructs). Six1 MOs: Expression of Cdca7l in the segmenting somites (arrows on control [ctrl] side) is lost on the injected (inj) side (side views, anterior to left). Expression of HoxA3 in the neural crest (nc) is greatly reduced on the injected side, whereas hindbrain (hb) expression is maintained (side views, anterior to left). Expression of Ism1 is lost in the midbrain (arrow) (frontal view, dorsal to the top). Expression of IMAGE 3399268 is expanded in the neural plate (line depicts width from midline to lateral border) on the injected side (dorsal view, anterior to the bottom). Expression patterns of Cnfn1-a in the hatching gland (arrows) and of Snail1 in the migrating neural crest are reduced and disrupted on the injected sides (frontal views, dorsal to the top). Six1 WT: Expression of BG022063 is broader in the neural plate (line) and neural crest (bracket) on the injected side (frontal view, dorsal to the top). Expression of Nfya is broader in the neural tube (line) on the injected side (dorsal view, anterior to the top). Expression of IMAGE 3399268 in the segmented somites (arrows, ctrl side) is lost on the injected side (side views, anterior to left). Expression of IMAGE 4057931 in the neural crest (bracket), otocyst (oto) and trigeminal ganglion (arrow) is greatly diminished on the injected side (side views, anterior to left). Six1-VP16: Expression of Frizzled10b, Pbx1, and Zic2 in the neural plate is expanded (line) on the injected side (frontal views, dorsal to the top). EnR-Six1: Expression of Frizzled10b in the neural plate is reduced (line) on the injected side (frontal view, dorsal to the top). Expression of IMAGE 4057931 is reduced in the PPR (arrows on the control side; frontal view, dorsal to the top). Expression of Zic2 and Otx1 in the neural tube is reduced (line) on the injected sides (arrows; frontal views, dorsal to the top). In MO-injected embryos, injected sides were confirmed by the use of lysamine-labeled MOs (not shown). In mRNA-injected embryos, injected sides were confirmed by the presence of nuclear β-galactosidase lineage labeling (pink dots visible in most images).
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