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Extraplacental human fetal tissues express mRNA transcripts encoding the human chorionic gonadotropin-beta subunit
P A Rothman1, V A Chao, M R Taylor
1Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco 94143-0132.
Molecular Reproduction and Development
|September 1, 1992
Summary
Human chorionic gonadotropin (hCG) beta-subunit mRNA is found in fetal kidney and adrenal tissues, similar to placental tissue. This indicates extraplacental fetal organs express hCG-beta, challenging previous understanding of its exclusive placental origin.
Area of Science:
- Reproductive Biology
- Molecular Endocrinology
- Developmental Biology
Background:
- Human chorionic gonadotropin (hCG) is a key pregnancy hormone, with its alpha-subunit expressed in pituitary and trophoblasts, and beta-subunit exclusively in trophoblasts.
- Previous studies suggest some midtrimester fetal tissues, beyond the placenta, may synthesize hCG-beta-like proteins.
- The precise nature and location of hCG-beta synthesis in extraplacental fetal tissues remain unclear.
Purpose of the Study:
- To investigate the presence and nature of hCG-beta-subunit mRNA in various human fetal and adult tissues.
- To determine if extraplacental fetal tissues express hCG-beta mRNA and compare its levels to placental tissue.
- To characterize the specific hCG-beta gene transcript found in fetal organs.
Main Methods:
- Nucleic acid hybridization techniques were employed to detect mRNA.
- Reverse transcription-polymerase chain reaction (RT-PCR) was used to amplify and analyze specific gene transcripts.
- Restriction endonuclease mapping was performed on PCR-generated cDNA fragments to identify gene sequences.
Main Results:
- Midtrimester fetal kidney and adrenal tissues exhibit hCG-beta mRNA transcripts at levels comparable to placental tissue.
- Fetal lung, brain, and muscle, as well as adult adrenal tissues, show only trace or undetectable levels of hCG-beta mRNA.
- Analysis confirmed that the hCG-beta transcript in fetal organs is an authentic copy of hCG-beta gene No. 5, located on chromosome 19.
Conclusions:
- The beta-subunit of human chorionic gonadotropin (hCG) is expressed in midtrimester fetal kidney and adrenal tissues, not exclusively in the placenta.
- This finding expands the known sites of hCG-beta gene expression during human development.
- The identified transcript is a genuine copy of a specific hCG-beta gene, confirming its molecular identity in these extraplacental tissues.