Fig. 2. Dll1 is required for normal expression of both rostral and caudal genes, and Mesp2 suppresses the caudal half property in both Dll1-dependent and Dll1-independent manners. Expression of Cer1 is usually observed as two or three stripes, finally localizing to the rostral half of nascent somite in the wild-type embryo (A). Cer1 expression is almost lost in both Dll1-null and Mesp2-null embryos (B,C), as well as the Dll1/Mesp2 double-null embryo (D). Normal stripes of Uncx4.1 expression, localizing to the caudal half of each somite (E), are completely lost in the Dll1-null embryo (F). In Mesp2-null embryos, expression of both Dll1 (Fig. 1) and Uncx4.1 is strongly expanded (G). However, the additional loss of Mesp2 in the Dll1-null embryo results in an expanded pattern of Uncx4.1 expression (H). Genetic cascades are also shown.