Reproduction Abstracts

Introduction: Paired-related transcription factors, PRRX1 and PRRX2, which are expressed in mesenchymal tissues and participate in mesenchymal cell differentiation, were recently found in stem/progenitor cells of the pituitary gland of ectodermal origin. The present study aimed to clarify the role of PRRX1 and PRRX2 in the pituitary gland by identifying factors that regulate the expression of both genes.

Materials and methods: Immunohistochemistry, promoter assay, EMSA and siRNA-knockdown analysis were performed.

Result and discussion: Immunohistochemistry showed different stage of appearance for PRRX1 at the embryonic period and PRRX2 at the postnatal one, indicating a presence of distinct regulatory system for each gene. Assay for Prrx1- and Prrx2-promoter activity by co-transfection of the expression vector of several transcription factors showed a cell-type dependent manner. Comprehensive comparison of transcriptional activity of several factors performed in CHO cells, which do not express Prrx1 and Prrx2, revealed the presence of common and distinct regulatory factors between both genes. Among them, KLF6 showed specific and remarkable activation of the Prrx2-promoter. EMSA and siRNA interference analysis revealed a potential ability of KLF6 to regulate the Prrx2-expression. Notably, KLF6 is likely to be involved in cell proliferation through the activation of Prrx2-expression. Finally, immunohistochemistry confirmed the presence of KLF6 in SOX2/PRRX2-double positive stem/progenitor cells of the postnatal pituitary gland. Thus, the finding of KLF6 might provide a novel clue to clarify the maintenance of stem/progenitor cells of the postnatal pituitary gland.