Methylation status of human chorionic gonadotropin beta subunit promoter and TFAP2A expression as factors regulating CGB gene expression in placenta

Abstract

Objective: To evaluate mechanisms regulating the expression of CGB genes in placental tissues from uncomplicated pregnancies and chorionic samples from spontaneous miscarriages.

Design: Molecular analyses in human samples.

Setting: Laboratory of molecular biology.

Patient(s): Nine placental samples from term deliveries and 21 chorionic samples from miscarriages at 7-13 weeks of gestation.

Intervention(s): None.

Main outcome measure(s): The expression level of CGBs and genes encoding SP1, SP3, and AP2 transcription factors was analyzed using quantitative polymerase chain reaction (qPCR). The methylation status of the CGBs' promoter regions was determined using methylation-specific PCR.

Result(s): The experiments showed significant differences in CGBs' expression and their regulation between placental and chorionic tissues. In placental tissues and chorionic tissues from 7 to 9 weeks of gestation, the expression level of CGBs was shown to be associated with the amount of TFAP2A transcripts. It was also demonstrated that variation in the expression level of CGB genes relies on changes in methylation of CGB3-9 and CGB1-2 promoter sequences.

Conclusion(s): During pregnancy, regulation of hCG beta subunit genes expression correlates with both methylation of their promoters and TFAP2A expression level. The results suggest that these factors may be very influential in the early stages of pregnancy and may be associated with pregnancy outcome.

Keywords: AP2α; CGB; SP1and SP3; methylation; miscarriage; placenta.