Embryonic mRNA expression pattern of the zebrafish twist1a gene. All images labeled with the same letter represent the same embryo in different views. All images are oriented with rostral at the top; in all lateral views anterior is to the left. Embryos shown are at the following stages: A, ∼60% epiboly; B, ∼75% epiboly; C, 2-3 somites; D, 6-8 somites; E, 10-12 somites; F, 15 somites; G, 24 somites; H,36 hpf. A-E: Dorsal views; A′-E′: lateral views, except B′, which shows the animal pole view. F,G: Head region, dorsal view; H: ventro-lateral view; F′-H′: body, dorsal view; F′-H′: lateral view; G′-1, G′-1: higher magnification of the dorsal and lateral views of the trunk region and the migrating sclerotome; D-I: DIC image of 6-8 somites embryo section through the hindbrain. ba, branchial and pharyngeal arches; cfb, chb, cmb, neural crest at the level of the fore-, hind-, and midbrain; d, dorsal somite; fb, forebrain area; hb, hindbrain area; mb, midbrain area; mnc, migratory neural crest; nc, neural crest; or, organizer region; pfb, pectoral fin bud primordia; scl, sclerotome.

Embryonic mRNA expression pattern of the zebrafish twist1b gene. All images labeled with the same letter represent the same embryo in different views, except A1, which is slightly older than the embryos in A and A′. All images are oriented with rostral at the top; in all lateral views anterior is to the left. Embryos shown are at the following stages: A, late shield; A1, ∼8hpf; B, 1-2 somites; C, 5-6 somites; D, 10 somites; E, 12 somites; F, 15 somites; G, 24 somites; H, 30 hpf; I, 36 hpf. A, A1: Dorsal view; A′: animal pole view; B-I: dorsal veiw of the head region; B′-I′: lateral view of the body; B″-I″: dorsal view of the body; H″: tilted profile view to better show the branchial arches. ap, animal pole area; ba, branchial and pharyngeal arches; cfb, chb, cmb, neural crest of the fore-, hind-, and midbrain areas; fb, forebrain; fbv, forebrain blood vessels; hb, hindbrain; lpm, lateral plate mesoderm; lnp, lateral neural plate; mb, midbrain; mt, myotome; nd, nephric duct; olf, olfactory placode; op, optic vesicle; ot, otic vesicle; pfb, pectoral fin bud primordia; s, somite; tb, tail bud area; arrow, signal in the area of the future ventral gut.

Embryonic mRNA expression pattern of the zebrafish twist2 gene. All images labeled with the same letter represent the same embryo in different views. All images are oriented with rostral at the top; in all lateral views anterior is to the left. Embryos shown are at the following stages. A: ∼60% epiboly; B: ∼75% epiboly; C: ∼90% epiboly (10hpf); D: 1-2 somites; E: 3-4 somites; F: 10-11 somites; G: 14 somites; H: 24 somites; I: 24 hpf; J: 36hpf. A-F and J: Dorsal views; A′-F′, G-J: lateral views. N.B. Not shown is the start of twist2 expression as a weak signal at the earlier shield stage. ba, branchial and pharyngeal arches; da, dorsal aorta; fb, forebrain; hyp, hypochord; hb, hindbrain; not, notochord; or, organizer region; pcv, posterior cardinal vein; scl,sclerotome; tb, tail bud.

Embryonic mRNA expression pattern of the zebrafish twist3 gene. All images labeled with the same letter represent the same embryo in different views. All images are oriented with rostral at the top; in all lateral views anterior is to the left. Embryos shown are at the following stages. A: 13 somites; B: 20 somites; C: 24 hpf; D: 36 hpf. A-D: Lateral view; A′-D′: dorsal view of the body; A′-D′: dorsal view of the head region. D′: Tilted profile for better view of the structures. All lateral images are oriented with rostral to the left. ba, branchial and pharyngeal arches; cfb, chb, cmb, neural crest of the fore-, hind-, and midbrain areas; fbv, forebrain blood vessels; hb, hindbrain; lnp, lateral neural plate; lpm, lateral plate mesoderm; mb, midbrain; pfb, pectoral fin bud primordia; tfp, area of the tail fin primordium.

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