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Human chorionic gonadotropin-beta gene expression in first trimester placenta
A K Miller-Lindholm1, C J LaBenz, J Ramey
1Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha 68198, USA.
Endocrinology
|December 6, 1997
Summary
Human chorionic gonadotropin beta (hCGbeta) gene expression in early pregnancy is dominated by gene 5. Total hCGbeta gene expression, not individual gene patterns, appears crucial for normal pregnancy maintenance.
Area of Science:
- Genetics
- Reproductive Biology
- Molecular Biology
Background:
- The human chorionic gonadotropin beta (hCGbeta) gene family comprises six genes (7, 8, 5, 1, 2, 3) on chromosome 19.
- Prior research suggested hCGbeta gene 5 is highly expressed in the first trimester, with lower levels for genes 3 and 8, and minimal expression for genes 7, 1, and 2.
- The typical expression pattern and its correlation with gestational age in normal pregnancy remain to be fully elucidated.
Purpose of the Study:
- To validate the typical expression pattern of hCGbeta genes in a large cohort of first-trimester placentas.
- To investigate the relationship between gestational age and hCGbeta gene expression patterns.
- To compare hCGbeta gene expression in normal placentas with that in abnormal pregnancy tissues and choriocarcinoma cells.
Main Methods:
- Quantification of hCGbeta gene expression from 27 first-trimester placentas (6-16 weeks gestation) using reverse transcription, PCR, and Genescan analysis.
- Analysis of gene expression in blighted ova, spontaneous abortion, hydatidiform mole, and JAR choriocarcinoma cells.
- Statistical assessment of expression patterns and correlation with gestational age.
Main Results:
- hCGbeta gene 5 constituted ≥50% of total beta mRNA in 14 out of 27 placentas.
- Gene 3 and gene 8 showed variable expression (1-42% and 12-32%, respectively), while gene 7 expression was consistently low (<3%).
- No significant correlation was found between hCGbeta gene expression patterns and placental age, though a trend of decreasing gene 3 expression after 10 weeks was observed.
- Abnormal tissues generally exhibited low gene 3 expression, within the range observed in normal placentas (excluding JAR cells).
Conclusions:
- The expression pattern observed in previous small studies is largely typical for normal first-trimester placentas.
- Gestational age does not significantly alter the relative expression pattern of hCGbeta genes in the first trimester.
- The total level of hCGbeta gene expression, rather than the specific pattern of individual genes, is likely critical for normal pregnancy maintenance.