Submitted September 14, 2007
Returned for revision September 30, 2007
Accepted December 25, 2007
Pregnancy
Glial Cell Missing 1 Regulates Placenta Growth Factor (PGF) Gene Transcription in Human Trophoblast
Miao Chang ,
Debashree Mukherjea ,
Ryan Gobble ,
Kathleen Groesch ,
Ronald J. Torry ,
and
Donald S. Torry *
* To whom correspondence should be addressed. E-mail: dtorry{at}siumed.edu.
Abstract
PlGF is prominently expressed by trophoblast in human placenta while most non-trophoblast cells express low levels of PGF mRNA under normal physiological conditions. We have shown that hypoxia decreases PGF expression in trophoblast, little is known about transcriptional regulation of PGF gene expression. We sought to determine promoter regions of the human PGF gene that contribute to its restricted high constitutive expression in trophoblast. Overlapping putative promoter regions of human PGF gene encompassing -1.5 Kb were cloned into reporter vectors and co-transfected into trophoblast and non-trophoblast cell lines. Promoter activity generated by a -1.5 Kb clone was significantly higher in trophoblast than in non-trophoblast. Selective deletion mutants showed that a clone encompassing PGF (-828/+34) region generated promoter activity similar to the -1.5 Kb region in trophoblast. However, deletion of another 131 bp from this subclone (-698/+34) resulted in significantly less promoter activity in trophoblast. The (-828/-698) region significantly enhanced activity of a minimal promoter construct in trophoblast but not in non-trophoblast cells suggesting that this region contributes to regulating PGF transcription in trophoblast. Site-directed mutagenesis of a GCM1 motif in the 131 bp region significantly decreased enhancer activity in trophoblast. Furthermore, overexpression of GCM1 significantly increased PlGF -1.5 Kb promoter activity and PGF mRNA expression in trophoblast and non-trophoblast. Forced overexpression of GCM1 restored PGF expression in hypoxic trophoblast. These data support a functional role for GCM1 contributing to constitutively high trophoblast PGF expression and is the first direct evidence of an oxygen responsive, trophoblast-specific transcription factor contributing to the regulation of PGF expression.
Key words:
Pregnancy •
Gene regulation •
Growth factors •
Placenta •
Trophoblast
