myo1D is required for left–right Organizer function. a–f MZ myo1D mutants display an impaired expression of southpaw (spaw) and pitx2 in the left lateral plate mesoderm. c, f Quantifications of spaw (c) and pitx2 (f) expression. For pitx2, the most marked difference between WT and MZ myo1D mutants is observed in the category with right-sided expression (e). g–m Temporal evolution of the asymmetry of dand5 expression between the end of gastrulation (Bud) and the 14-somite stage. m Quantifications of the relative abundance of dand5 transcripts on the left (L) and right (R) side of WT ABTÜ embryos reveal a peak of LR asymmetry at the eight-somite stage. n–q Eight-somite stage asymmetry of dand5 asymmetry is reduced in MZ myo1D mutants. No further reduction of asymmetry is observed in MZ myo1D; MZ myo1G double mutants. For values of dand5 asymmetry for individual display items, see Methods. r–t Asymmetric spaw expression is altered in MZ myo1D; MZ myo1G double mutants. The frequency of defects is comparable to MZ myo1D single mutants (c). a, b, d, e, r, s are dorsal views of 18-somite stage embryos, anterior up. g–l and n–p are dorsal views of the LRO, anterior up. Error bars in m and q indicate SEM. Scale bars: 50 µm in a, b, d, e, r, s; 20 µm in g–l and n–p
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