Retinoic acid-induced thymic abnormalities in the mouse are associated with altered pharyngeal morphology, thymocyte maturation defects, and altered expression of Hoxa3 and Pax1.

Exogenous retinoic acid is teratogenic in animals and man, causing a spectrum of abnormalities termed retinoic acid embryopathy. Using a mouse model of retinoic acid embryopathy, our results show that exposure to all-trans retinoic acid (RA) on gestational day (gd) 9 results in thymic ectopia, hypoplasia, and thymocyte maturational defects. Immunohistochemical and flow cytometric analyses showed aberrant expression of stromal and thymocyte markers, and abnormalities in thymocyte development.