Fig. 1.

CV2 expression pattern at 12.5 d.p.c. and Cv2^−/− phenotype. (A-A’) Detection of the CV2 protein on sagittal paraffin sections of wild-type and Cv2 mutant mouse embryos at 12.5 d.p.c. by immunohistochemistry. Note in wild-type the CV2 protein staining in the vertebral bodies (vb). No CV2 protein is detected in Cv2^−/− embryos. Asterisks indicate unspecific signals present in both wild-type and mutant embryos. bo, basioccipital bone. (B) Higher magnification view of the CV2 staining in the vertebral bodies. ivd, intervertebral disc. (B’) The CV2 signal in thyroid cartilages (tc) and tracheal rings (tr), shown at a higher magnification. (C-C’) External view of littermates from Cv2^+/− intercrosses showing shorter tails in Cv2^−/− compared to wild-type and exencephaly observed in 25% of the mutants. Inset shows a Cv2^−/− mutant lacking exencephaly. (D-E’) Mallory’s tetrachrome staining of sagittal paraffin sections of wild-type (top panels) and mutant (bottom panels) neonates. Cv2^−/− embryos die at birth of respiratory failure. Note in the thoracic region of Cv2^−/− the reduction of the lumen of the trachea and the decreased distance between the vertebral column and the manubrium of the sternum (ms). Insets show tracheas of wild-type and Cv2^−/− embryos stained with Alcian Blue and Alizarin Red. Note that in the mutant the cartilage rings that support the trachea are absent. Boxed areas are shown at higher magnification in (E) and (E’). In the mutant the collapse of the tracheal lumen (Lt) is due to the absence of the tracheal rings (tr). cns, central nervous system; cr, cricoid cartilage; h, heart; hy, hyoid bone; li, liver; m, muscle; th, thyroid cartilage ; to, tongue.