Defects in the formation of the prechordal plate and its derivatives in oep mutants. (A,B) Formation of hatching gland cells in wild-type (A) but not oep mutant (B) embryos at 26 hpf as judged from the expression of the hatching gland specific gene hgg1. Dorsal-anterior view, ventral is to the right. (C,D) Formation of eye muscles (arrows) in wild-type (C) but not oep mutant (D) embryos at 42 hpf as judged from expression of myoD. Arrowhead indicates the location of pharyngeal muscles in wild-type and oep mutant embryos. (E,F) Formation of hatching gland precursors (pillow) in wild-type (E, fine arrowhead) but not in oep mutant (F) embryos at the 6-somites stage as judged from islet1 expression. Stars indicate the normal formation of the trigeminal ganglion anlage. Dorsal view, anterior is to the left. (G,H) Formation of hatching gland precursors in wild-type (G, fine arrowhead) but not oep mutants at the end of gastrulation (bud stage) as judged from hgg1 expression. Note the normal anterior limit of notochord precursors anterior to the krox20 stripe in rhombomere 3 (star) as judged from the expression pattern of T/ntl (arrow). Dorsal view, anterior is to the left. (I,J) Expression of hlx1 in wild-type (I) and oep mutant embryos (J) at the tail bud stage. Arrows highlight the expression of hlx1 in the hindbrain. Dorsal view, anterior is to the left. (K,L) Expression of hgg1, axial and krox20 in wild-type (K) and oep mutant embryos (L) at 90% epiboly. Note that at this stage wild-type axial expression in the axial mesoderm still includes the prechordal plate (arrow) with the exception of the hatching gland precursors (fine arrowhead). Star indicates the location of krox20 expression in rhombomere 3. Dorsal view, anterior is to the left.
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