**2.5 Retinoic acid administration to mouse embryos and pups**

To administer retinoic acid (RA; Sigma #2625 or ITSUU laboratory), the stock solution was prepared with a concentration of 30 mg/ml, and 1ml of the 1/1000 diluent (30 g) was intraperitoneally administrated to the mother or the pups, per 1g of body weight (Smith et al. 2001).
