EXPRESSION OF THE KIR2.1 (INWARDLY RECTIFYING POTASSIUM CHANNEL) GENEIN THE HUMAN PLACENTA AND IN CULTURED CYTOTROPHOBLAST CELLS AT DIFFERENT STAGES OF DIFFERENTIATION

The aim of this study was to investigate whether the Kir2.1 gene is ex pressed by the human placenta throughout pregnancy and in cytotrophobl ast cells at different stages of differentiation in culture. RNA was e xtracted from cytotrophoblast cells isolated from term placentas and m aintained in culture for 18, 66 and 114 h and from first, second and t hird trimester placentas. Using the reverse transcriptase-polymerase c hain reaction (RT-PCR) with gene-specific primers, a cDNA product of 1 .2 kb, as expected for Kir2.1 gene expression, was detected in all the RNA samples from cytotrophoblast cells and from placentas. The RT-PCR products were verified by sequencing and by detection of the expected transcript size for the Kir2.1 mRNA at 5.6-5.7 kb on Northern blots, using the 1.2 kb cDNA generated by RT-PCR. Northern blot quantificatio n, using a control 28S rRNA probe, showed no significant difference in Kir2.1 mRNA expression between any of the three stages of cytotrophob last cell differentiation studied (ANOVA; n = 3 RNA samples from each stage). These data demonstrate that the Kir2.1 gene is expressed by th e human placenta and, specifically, by cytotrophoblast cells, at all s tages of development and differentiation.