Fig. 7. Skeletal phenotype of transgenic embryos. Wild-type (A,D,F) and Six2 transgenic embryos (B,C,E,G) are shown. (A) Hyoid bone (black arrow), greater and lesser horn, and thyroid and cricoid cartilage of wild-type embryos. (B) The hyoid bone (black arrow) is malformed and fused to the thyroid cartilage. The greater horn is fused to the thyroid cartilage (arrowhead) and to the lesser horn. The thyroid and cricoid cartilages are thickened and the cricoid cartilage elongates ventrally (asterisk). (C) The hyoid bone (arrow) and the laringeal cartilages have fused in a disorganized structure. The rings of the trachea are also fused to each other. (D) The exoccipital bone and the atlas are separated by cartilage (arrow). (E) The corresponding area in transgenic embryos (arrow) displays fusion of the atlas to the exoccipital bone. (F) Ossification is almost completed in the supraoccipital bone (arrow). (G) In transgenic embryos the supraoccipital bone shows very reduced ossification (arrow points to the expected position for the supraoccipital bone). at, atlas; cr, cricoid cartilage; ex, exoccipital bone; g, greater horn; l, lesser horn; su, supraoccipital bone; th, thyroid cartilage.