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Fig. 2. XHes2 is mainly expressed in presumptive and developing sensory organs. (A-O) Whole-mount in situ hybridization analysis of XHes2 expression during embryogenesis. (A) XHes2 positive cells are transiently detected in the midgastrula animal ectoderm. (B-M) During neurulation and organogenesis, XHes2 transcripts are predominantly expressed in dorsal parts of the otic placodes (B-D,G-I) and vesicles (J-M) (black arrowheads in H,J,M), as well as in the presumptive (H,I) and developing (J-M) retina (black arrows in H,J,K). A weaker expression is detected in the olfactory placodes (grey arrowhead in I), and later in the lateral line system (white arrowheads in L,M). XHes2 transcripts are also found in lateral (grey arrow in C,D) and medial (light grey arrow in C,D) filamentous stripes within the posterior neuroectoderm, and in longitudinal domains between midline and otic placode in the anterior neuroectoderm (light grey arrow in C,D). XHes2 and N-tubulin expression domains seem to overlap (double in situ hybridization in D), but XHes2 expression is restricted to the superficial layer (E), while N-tubulin probes stain the deeper layer (F), as observed on vibratome cross sections. Further expression of XHes2 is evident in some dorsal cells of the forming brain (H,I), and later in the forebrain and hindbrain (L,M; grey arrows in H,L,M). (N-Q) During retinogenesis, XHes2 expression progressively vanishes from the central neural retina (NR) as differentiation proceeds (black arrowhead in O), and is finally restricted to the dividing precursors of the CMZ (N-P black arrows) and to the lens (LE; black arrowhead in P). In the CMZ, XHes2 expression is excluded from the stem cell containing region (black arrowhead in Q). Embryos are orientated as follows: (A) lateral view, animal up; (B-D) dorsal view, anterior down; (G-I) frontal view, dorsal up; (J-L) lateral view, anterior left; (M) dorsal view, anterior left. (N-Q) Vibratome cross-sections. Scale bar: 50 μm. (Q) Magnification of the CMZ in P. |
