Progesterone Induced Blocking Factor Isoforms in Normal and Failed Murine Pregnancies


  • A. Bogdan and B. Polgar contributed equally to the work.



Progesterone induced blocking factor (PIBF) is required for successful pregnancy. Alternative splicing produces PIBF isoforms with different functions. The full-length (90 kDa) PIBF is involved in cell cycle regulation, whereas smaller secreted forms act as cytokines. We aim to examine the PIBF exon pattern and protein isoform profile in normal and failed murine pregnancies.

Method of study

Pregnant Balb/c mice were killed on gestation days 12–14 or 17–19. Normal and resorbed fetuses, placentae, and uterine tissue were used for RNA and protein analysis with RT-PCR and Western blot, respectively.


Late pregnancy and resorption were associated with lower expression of the N-terminal exons, together with significantly reduced production of the full-length protein.


Reduced production of the full-length PIBF protein might result in disturbed cell cycle regulation and dysregulated trophoblast invasion, while the absence of PIBF isoforms containing exon 2–4 coded sequences might lead to the loss of local immunosuppression.