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Fig. 5. Expression of XSix1 in the lateral lines. (A) At stage 37/38 XSix1 expression corresponds to the position of the primordia of the medial trunk lateral line (m) and the ventral trunk lateral line (v). Arrowheads just caudal to the ventral lateral line primordium denote segmental expression in the ectoderm near the ventral border of the somites. (B) Transverse section demonstrating XSix1 expression in an ectodermal thickening corresponding to the medial trunk lateral line primordium. Both superficial and deep layers express the gene. Asterisk denotes faint staining in the dorsal somite. n, nephrotome. (C) At stage 41 the three trunk lateral lines (dorsal, d; middle, m; ventral, v) are distinguished by XSix1 expression. Spots of staining (blue) also are observed near the gills (asterisk). Black spots are pigment cells. (D) A ventral view of embryo in (C) demonstrates XSix1 expression in the anterior branch of the ventral trunk lateral line (v), in the hyomandibular lateral line (hy) and in spots near the gills (asterisk), which may correspond to the hypobranchial placodes. (E) Stage 37 expression of Xkrk1 in the same position as XSix1 (cf. B). Dark splotches in neural tube (nt) are optical artifacts. (F) Stage 39 expression of sox3 in the medial and ventral lateral line primordia posterior to the otocyst, in positions similar to those of XSix1 expressing cells (cf. A). (G) Stage 40 XSix1-expressing cell cluster that histologically appears to be a neuromast. (H) Stage 40 sox3-expressing cell cluster in same position as XSix1-positive cells (cf. G). The superficial cells of the cluster do not express sox3. (I) Stage 40 sox2-expressing cell clusters (arrows) in same position as XSix1-positive cells corresponding to the ventral and medial lateral lines (cf. C). (J) Stage 37/38 XSix1-expressing cell clusters (arrows) in the appropriate positions to represent the supraorbital and infraorbital lateral line primordia. ret, retina; nt, neural tube. (K) Stage 41 XSix1-expressing cell cluster (arrow) in the appropriate position to be a supraorbital neuromast. (L) Stage 41 sox2-expressing cell cluster (arrow) in same position as XSix1-positive cells in the hyomandibular lateral line. (cf. D). (M) Stage 42 XSix1-expressing neuromast of the middle lateral line. (N) Stage 42 sox2-expressing neuromast of the middle lateral line. Arrow points to border between superficial, unstained cells and deep layer of stained cells. |
