lefty1 and lefty2 expression domains are disrupted in zebrafish midline mutants. (A-H) In situ localization of lft1 and lft2 in mutant embryos at 85- 90% epiboly (dorsal views). Embryos from heterozygous flh parents show wild-type expression of lft1 (A) and lft2 (B). cyc mutant embryos do not express lft1 or lft2 in the anterior midline (C,D) and lft2 is only expressed in a few cells near the dorsal margin. In oep mutants lft1 and lft2 expression in the prechordal plate is limited to a few cells (E,F); lft2 expression is also reduced in floorplate precursor cells (F). In ntl mutants lft1 expression is lost in dorsal forerunner and marginal cells (G), and lft2 expression in floorplate precursors is expanded laterally (H). (I) lefty expression domains at 85% epiboly. lft1 is expressed at the margin, and in dorsal forerunner cells. lft2 is expressed in the posterior midline in floorplate precursors. Both genes are expressed in the anterior midline in the polster and prechordal plate. Expression domains affected in different midline mutants are summarized at right.
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