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Fig. 2. Early expression of Xencr-1. (A–C) Vegetal view of Xencr-1 during gastrula stages, dorsal side up. (A) st. 11. (B) st. 11.5. (C) st. 12.5. Xencr-1 expression begins at st. 11 in the medial dorsal marginal zone above the blastopore (A) and converges toward the dorsal midline and extends anteroposteriorly during gastrulation (B, C). (D–I) Dorsal view of Xencr-1 during neurulation, anterior side up. (D) st. 13.5. (E) st. 14. (F) st. 15. (G) st. 16. (H) st. 18. (I) st. 20. Xencr-1 expression extends to the prechordal mesoderm by st. 13.5 (E, arrowhead) and by stage 14 begins to be expressed in the anterior and lateral neural folds (F, arrowheads) of the trunk region of the embryo (intermediolateral deep cells of [Schroeder, 1970]. Expression in the pronephric anlage is seen at st. 20 (I).Sagittal section at st. 13.5 (d′) and transverse section at st. 14 (e′) reveal that Xencr-1 is expressed throughout the dorsal midline tissues, the dorsal-most endoderm, notochord, and median deep cells of the neuroectoderm. Red arrows in (e′) indicate the neural ectoderm/notochord boundary. Sagittal section at stage 16 (g′) reveals that expression is being down-regulated in the anterior notochord, while sagittal and transverse sections at st. 18 (h′), (h′) demonstrate that expression is maintained in anterior hypochord (h′, arrowhead) and floorplate (h′ arrow; median deep cells of [Schroeder, 1970]. |
