Fig. 8

SIX1 expression in cephalic NCC differentiating in culture. After 6 days of culture, cephalic quail NCC were assayed for expression of SIX1 and various NC-derived phenotypic markers (see Methods section). SIX1-positive nuclei were recorded in approximately 1% of the NCC population (n = 12 cultures). a-d Co-staining of nuclear SIX1 and cytoplasmic αSMA shows expression of SIX1 in myofibroblastic cells (arrows in d). e-h DAPI, SIX1 and CS co-staining identifies SIX1-expressing chondrocytes, positive for CS and forming a tridimensional nodule; SIX1-immunoreactive cells are also present in the perichondrial region (arrowhead in h). i Quantification of cell phenotypes in the SIX1-positive cell subpopulation identified in the NCC cultures. Data are expressed as mean ± S.E.M. (n = 5 cultures). Approximately 55% of SIX1-labeled NCC were of myofibroblastic (αSMA+) and 13% of chondrocytic (CS+), phenotypes. The remaining SIX1-expressing cells (i.e., negative for CS and αSMA) were not labeled with HNK1 and tyrosine hydroxylase (markers of PNS precursor cells and adrenergic neurons, respectively); these cells are thus designated as of undefined phenotype. Scale bars, 50 μm