Knockdown of raldh2 leads to loss of a somite and the resultant second cervical vertebra. (A) Representative images of uncx4.1 expression in control MO- (left) or raldh2 MO-injected (right) embryos at 15 hpf. Lateral view, anterior to the left. Arrows mark the position at SI. (B) Somite numbers in control MO- (black; n=32, 45, 47, 47 and 48) or raldh2 MO-injected (red; n=34, 38, 55, 55 and 56) embryos at 12, 13, 14, 15 and 16 hpf. Error bars indicate s.d. raldh2 morphants lack one somite. (C) Representative images of skeletal structures in control MO-(upper panel) or raldh2 MO-injected (lower panel) fish at 1.5 months old. Bones (red) and cartilage (blue) are stained by Alizarin Red and Alcian Blue, respectively. Right: higher-magnification views of the cervical vertebrae (right panels). The second cervical bone (arrow in upper right image) forms in control MO-injected fish, but is missing in raldh2 MO-injected embryos (lower right). (D) Vertebra number in control MO- or raldh2 MO-injected fish. Results from statistical analyses are shown in supplementary material Tables S5, S6, S8.
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