Postnatal Changes in the Expression and Localization of Jmjd3 in the Mouse Submandibular Gland

The development of the submandibular gland is mediated by epithelial-mesenchymal interactions; the acini and ducts are immature at birth and proliferate and differentiate after birth. Limited information is available on epigenetic modi-fications via histone modifications during the early phase of salivary gland development. Therefore, the present study exam-ined changes in the expression and localization of Jmjd3 to clarify the role of the H3K27me3 epigenetic modification in the postnatal development of the submandibular gland in mice. Morphological, immunohistochemical, and molecular biological assays were performed using submandibular glands harvested from mice at birth on day 0 to 10 weeks of age. On day 0, submandibular glands were characterized by the presence of terminal tubules and ducts within abundant connective tissue. The proliferation and differentiation of ductal cells in submandibular glands peaked by day 7, and the structure of subman-dibular glands matured to mimic that of adult mice by day 28. Jmjd3-positive cells were mostly found in connective tissue on day 0. After day 7, most of these cells were detected in the ducts. As submandibular glands continued to develop, the number of Jmjd3-positve cells significantly decreased irrespective of the location. The mRNA expression level of Jmjd3 continued to increase until day 7 and gradually decreased after day 14. Collectively, the present results demonstrated the de-velopment and differentiation of mouse submandibular gland tissue concurrent with significant changes in the expression and localization of Jmjd3 during the early postnatal period. Therefore, epigenetic modifications via histone H3K27me3 demethylation occur as the submandibular gland develops.