tdTomato expression in the vertebral column and forelimbs of Pax9-CreER;tdTomato mice induced at E10.5 and E12.5. (a, b) Visualization of whole mount transverse section view of the vertebral column of E12.5 and E14.5 Pax9-CreER;tdTomato mice 48 hours after tamoxifen induction. Arrows indicates tdTomato expression in the intervertebral disk primodia. (c, d) Ventral views of forelimbs from E12.5 and E14.5 Pax9-CreER;tdTomato mice 48 hours after tamoxifen induction in whole mounts (c, d) and sections (c’, d’). ** and * in (c) and (c’) indicate strong and weaker expression region of tdTomato in the limb bud. ** and * in (d) and (d’) indicate expression close to the phalangeal bone primodia and in the pawpad region. Boxed areas in (c) and (d) are shown enlarged in (c’) and (d’), respectively. Thin white line outlines the forelimb. Scale bars, 200μm.