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Fig. 4
Heart field migration is sensitive to Robo1 dosage. (A) Endocardial migration was defective at 20 somites in zebrafish embryos injected with 75 pg Robo1 mRNA (mCherry mRNA was utilized as a control). (B) Rescue of migration defects in miR-218 morphants was accomplished by co-injecting sub-phenotypic doses of robo1 MO. Quantification of migration defects is shown beneath. *, P<0.05 (Fisher′s exact test for a 2×3 contingency table). (C) Analysis of endocardial migration at the 20-somite stage in Tg(hsp70l:slit2-GFP) embryos that were heat shocked at 5 somites. Embryos lacking the transgene were used as a control. Disorganization of the endocardium was evident in Slit2-overexpressing embryos. Scale bars: 50 μm.