curly up affects expression of left-specific genes in the lateral plate mesoderm (LPM) and dorsal diencephalon. Dorsal views of spaw (A-D) and lefty1/2 (E-H) expression in 20- to 22-somite stage embryos (A-H) and ventral views of pitx2 expression in the dorsal diencephalon of 24-somite stage embryos (I-L) from cup heterozygote crosses. Alterations from normal left asymmetric Nodal signaling in the LPM (A) in cup mutants include bilateral (B), right (C), and absent (D) expression of spaw in this tissue. Over half of the bilaterally expressing embryos show only posterior propagation of spaw. Similarly, asymmetrically expressed downstream targets of Nodal signaling in the LPM and brain are also disrupted. lefty1/2, which are normally expressed in the left cardiac LPM (E), have bilateral (F), right (G), and absent (H) expression patterns in cup mutants. In H, midline expression of lefty1 can also be seen. pitx2, which is normally expressed on the left side of the diencephalon (I), can be expressed bilaterally (J), on the right (K), or not at all (L) in cup embryos. The majority of embryos show no expression of lefty1/2 in the LPM and diencephalon and no expression of pitx2 in the diencephalon.
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