Fig. 7

SIX1 expression in posterior cephalic muscles and skeletogenic mesenchyme in E7 chicken. a Schematic representation of an E7 (HH30) chick head; red line indicate the position and orientation of sections. b-d At BA1 level (b), SIX1 and MF20 (c-c') are co-expressed in tongue muscles (magnified in c”). d” In lower jaw rudiment, anti-CS labels Meckel’s cartilage, whereas SIX1 antibody only marks the perichondrium (see higher magnification in d”’). e-h SIX1, MF20 and CS staining in BA2 (f, g, h, magnifications of regions boxed in e). e-g SIX1 is expressed in laryngeal muscles, including ceratoglossus (g) and constrictor and dilatator glottidis (f-f’). h CS-labeled ceratobranchial cartilage, showing SIX1 expression only in the perichondrium. i-l (i’-l’ magnifications of boxed areas) In the otocyst region, SIX1 immunostaining is present in the inner ear epithelium and adjacent CS-immunoreactive cartilage of the otic capsule (i-k and i’-k’) as well as in a more lateral area wherein cells bearing RUNX2 osteoblast marker were recorded (l-l’, adjacent section). m-p Partial overlap of SIX1 and CS markers in the ventral otic capsule adjacent to the notochord (no in m). D-V, dorso-ventral orientation. Scale bars, 100 μm, except for b, 300 μm; f, 50 μm; e and i-l, 200 μm