Figure 4: Relation between dynamics of nodal cilia and L–R asymmetric gene expression in Dpcd and Rfx3 mutant embryos.

Ciliary motion and L–R marker gene expression were examined in the wild-type embryo (a), and Dpcd mutant embryos with severe (b) or mild (c) impairment of the formation of motile node cilia. Similarly, the wild-type embryo (d), and Rfx3 mutant embryos with severe (e) or mild (f) impairment of the formation of motile node cilia were examined for ciliary motion and L–R marker gene expression. For each embryo, rotating cilia in the node are shown on the left, whereas expression pattern of L–R markers is shown in the right boxes. Rotating cilia are shown by coloured circles. Red and pink circles denote posteriorly tilted cilia, whereas green and white circles denote rotating cilia showing no tilt. The number of total rotating cilia in the node cavity was determined by changing the focal plane. Although all the rotating cilia are shown for the mutant embryos, only a portion of rotating cilia detected on a single plane is shown for the wild-type (+/+) embryos (a,d). Expression of Cerl2 in the node and that of Nodal or Pitx2 in the lateral plate mesoderm were examined as L–R markers by in situ hybridization. Asymmetric expression of Cerl2 and Pitx2 was maintained in the mildly affected mutant embryos at the six-somite stage, whereas that of Cerl2 and Nodal was lost in the severely affected embryos. The white, black and red scale bars indicate 10 μm, 70 μm and 0.5 mm, respectively.