Epidermal Differentiation and DNA Demethylation of the Epidermis in Late Gestation of the Mouse Fetus

OBJECTIVE: To investigate the dynamic changes of epidermal differentiation and demethylation in Kunming mice during late gestation fetal development. STUDY DESIGN: The fetuses were obtained from pregnant Kunming mice at embryonic (E) days 12.5, 14.5, 16.5, and 18.5. Hematoxylin and eosin staining and immunohistochemistry were used to detect the epidermal differentiation and demethylation on the back, abdomen, hind leg, and face of the late-stage murine fetuses. RESULTS: Cutaneous keratinization did not occur in Kunming mice until E18.5. The facial epidermis was thicker than the other parts of the epidermis. Cytokeratin (K) 15 was strongly expressed in 4 parts of the epidermis at E16.8. K19 was stronger in the abdominal and hind limb epidermis at E18.5. Involucrin appeared in the epidermis of the abdomen, hind limb, and face from E16.5 to E18.5 but in the back epidermis only at E18.5. 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) began to be detectable at E12.5, but they were undetectable in all parts of the epidermis except the facial skin at E18.5. The expression of Tet methylcytosine dioxygenase 2 (TET2) and TET3 appeared mainly at E14.5 and E16.5. CONCLUSION: The differentiation of epidermis in different parts of Kunming mice before birth is related to DNA demethylation, which is related to the function of epidermis in different parts.