Fig. 5

SIX1 expression in head neural and sensory structures of E3 and E7 chicken embryos. a DAPI staining of E3 (HH19) chicken head longitudinal section (A and D, anterior and dorsal orientations). Boxed areas indicate regions of the otic vesicle and trigeminal ganglion magnified in b-e and f-j, respectively. c-e SIX1 immunoreactivity is located in the ventrolateral region of the otic vesicle (c), whereas SOX10 labels its dorsal region (d and e). f-j More rostrally in the same section, SIX1-immunoreactive nuclei (g) exhibit a dense pattern in the trigeminal ganglion and surrounding mesenchyme; the trigeminal ganglion is positive for SOX10 (h) and TUJ1 (i) markers; j Merge of SIX1 and SOX10; j’-j” (magnifications of the boxed area indicated in j) SIX1-positive nuclei mostly correspond to SOX10-negative, TUJ1-positive neuronal cells in the trigeminal ganglion. k Schematic representation of a chick embryonic head at E7 (HH30); red lines indicate position and orientation of the sections shown in n-o. (l) SIX1-expressing cells are found lining the dorsal mesencephalon and more ventrally, adjacent to the retina (r). l’ highlights the dorsal region boxed in l, showing SIX1-positive cells scattered in the mesenchyme between the surface ectoderm (arrow) and the neuroepithelium (arrowhead). m and n More ventrally in the same section, SIX1 is expressed in the olfactory epithelium (oe, in m), and adenohypophysis (ad, in n) whereas the neurohypophysis is SIX1-negative (arrow in n), and in the inner ear epithelium (iee in o). (D and V, dorsal and ventral orientations). Scale bars, 100 μm, except for a and l, 200 μm