Abstract
Increased levels of human chorionic gonadotropin (hCG) are used as markers for Down syndrome (DS) screening of low-risk populations. The pathophysiology for increased hCG levels remains unknown. In general, hCG synthesis is limited by the rate of β-chain formation. In the placenta, 2 of a total of 6 hCG β-genes are expressed. We hypothesized that in DS, a transcriptional factor may upregulate β-chain transcription by interacting with the β<sub>5</sub>-promoter. Primary cell cultures of skin fibroblasts from both normal and DS midtrimester fetuses were established and transfected with the β<sub>5</sub>-promoter linked to the chloramphenicol-acetyl-transferase reporter gene. The chloramphenicol-acetyl-transferase activity was measured. Three of six DS-derived cell cultures showed a three-fold increase in acetylation. The increase in hCG promoter activity in DS-derived fibroblasts suggests a possible role for a transcriptional factor located on the human chromosome 21 by either directly or indirectly interacting with the β<sub>5</sub>-promoter.
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