(A) Hematoxylin and eosin-stained image obtained by vertically cutting embryo numbers 2 (WT) and 7 (KO) in Fig 5A. (B) Hematoxylin and eosin-stained image obtained by vertically cutting embryos 3 (WT) and 10 (KO) in Fig 5B. Scale bars represent 1 mm. a, spinal cord; b, sclerotome.