Co-localization of KLF6 and KLF4 with pregnancy-specific glycoproteins during human placenta development.

Pregnancy-specific glycoproteins (PSGs) are major placental proteins essential for the maintenance of normal gestation. However, little is known about their gene expression regulation during placentation. It was previously demonstrated that the human core promoter binding protein recently renamed Krüppel-like factor (KLF) 6 binds to a highly conserved sequence within the PSG promoters and is mainly expressed in human term placenta. Here, we determined the expression pattern of the 13 other KLFs during human placental development. We demonstrate that eight KLFs exhibit specific expression patterns in human placental tissues and membranes, in favor of a functional cooperation of specific KLFs during placentation. In addition, we demonstrate that KLF6, KLF4 and PSG proteins are co-expressed in same cell types of placental villi and membranes. This experimental evidence further strengthens the potential cross talk of both transcription factors for PSG gene regulation in vivo.