Document Detail

An evolutionary test of the isoform switching hypothesis of functional progesterone withdrawal for parturition: humans have a weaker repressive effect of PR-A than mice.
MedLine Citation:
PMID:  22752763     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: A decrease in maternal serum progesterone (P4) concentrations precedes the onset of labor in most placental mammals. Humans differ by maintaining high levels of P4 throughout birth. Parturition in humans probably includes mechanisms that undercut the pregnancy sustaining function of P4. One attractive hypothesis is the isoform switching hypothesis (ISH). ISH is supported by in vitro evidence that progesterone receptor isoform A (PR-A) inhibits PR-B and that the PR-A/PR-B ratio increases towards term.
MATERIALS AND METHODS: Here, we test the hypothesis that isoform switching is an adaptation to high levels of P4 at term, predicting that, in humans, PR-A mediated repression of PR-B is stronger than in mouse. We use reporter assays with human and mouse PRs to detect species differences in the repressive effects of PR-A.
RESULTS: We found that human PR-B is less sensitive to repression by human PR-A than mouse PR-B, contrary to our prediction. The difference between human and mouse PR-B sensitivity is most pronounced at PR-A/PR-B ratios typical for the preterm myometrium.
CONCLUSIONS: Our results are inconsistent with the ISH. We speculate that, instead, the lower sensitivity of human PR-B to PR-A may be relevant for the maintenance of pregnancy at high progesterone levels and increasing PR-A concentrations towards term.
Günter P Wagner; Yingchun Tong; Deena Emera; Roberto Romero
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Publication Detail:
Type:  Comparative Study; Journal Article     Date:  2012-03-27
Journal Detail:
Title:  Journal of perinatal medicine     Volume:  40     ISSN:  1619-3997     ISO Abbreviation:  J Perinat Med     Publication Date:  2012 Jun 
Date Detail:
Created Date:  2012-07-03     Completed Date:  2012-11-23     Revised Date:  2014-09-03    
Medline Journal Info:
Nlm Unique ID:  0361031     Medline TA:  J Perinat Med     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  345-51     Citation Subset:  IM    
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MeSH Terms
Myometrium / chemistry
Parturition / blood,  physiology*
Pregnancy Maintenance / physiology
Progesterone / physiology*
Protein Isoforms / physiology
Receptors, Progesterone / analysis,  physiology*
Species Specificity
Grant Support
Reg. No./Substance:
0/Protein Isoforms; 0/Receptors, Progesterone; 0/progesterone receptor A; 0/progesterone receptor B; 4G7DS2Q64Y/Progesterone

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