EGFR signaling promotes β-cell proliferation and survivin expression during pregnancy.
Placental lactogen (PL) induced serotonergic signaling is essential for gestational β-cell mass expansion. We have previously shown that intact Epidermal growth factor -receptor (EGFR) function is a crucial component of this pathway. We now explored more specifically the link between EGFR and pregnancy-induced β-cell mass compensation. Islets were isolated from wild-type and β-cell-specific EGFR-dominant negative mice (E1-DN), stimulated with PL and analyzed for β-cell proliferation and expression of genes involved in gestational β-cell growth. β-cell mass dynamics were analyzed both with traditional morphometrical methods and three-dimensional optical projection tomography (OPT) of whole-mount insulin-stained pancreata. Insulin-positive volume analyzed with OPT increased 1.4-fold at gestational day 18.5 (GD18.5) when compared to non-pregnant mice. Number of islets peaked by GD13.5 (680 vs 1134 islets per pancreas, non-pregnant vs. GD13.5). PL stimulated beta cell proliferation in the wild-type islets, whereas the proliferative response was absent in the E1-DN mouse islets. Serotonin synthesizing enzymes were upregulated similarly in both the wild-type and E1-DN mice. However, while survivin (Birc5) mRNA was upregulated 5.5-fold during pregnancy in the wild-type islets, no change was seen in the E1-DN pregnant islets. PL induced survivin expression also in isolated islets and this was blocked by EGFR inhibitor gefitinib, mTOR inhibitor rapamycin and MEK inhibitor PD0325901. Our 3D-volumetric analysis of β-cell mass expansion during murine pregnancy revealed that islet number increases during pregnancy. In addition, our results suggest that EGFR signaling is required for lactogen-induced survivin expression via MAPK and mTOR pathways.
Research Programs Unit, Molecular Neurology, Biomedicum Stem Cell Center, University of Helsinki, Helsinki, Finland.
Elina
E
Hakonen
Research Programs Unit, Molecular Neurology, Biomedicum Stem Cell Center, University of Helsinki, Helsinki, Finland.
Jarkko
J
Ustinov
Research Programs Unit, Molecular Neurology, Biomedicum Stem Cell Center, University of Helsinki, Helsinki, Finland.
Jaan
J
Palgi
Research Programs Unit, Molecular Neurology, Biomedicum Stem Cell Center, University of Helsinki, Helsinki, Finland; Children's Hospital, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland.
Päivi J
PJ
Miettinen
Research Programs Unit, Molecular Neurology, Biomedicum Stem Cell Center, University of Helsinki, Helsinki, Finland; Children's Hospital, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland.
Timo
T
Otonkoski
D000818:Animals; D049109:Cell Proliferation; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism*; D007515:Islets of Langerhans / Q000166:cytology* / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D051379:Mice; D011247:Pregnancy; D060888:Real-Time Polymerase Chain Reaction; D012097:Repressor Proteins / Q000378:metabolism*; D015398:Signal Transduction; D000077022:Survivin; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D015854:Up-Regulation
C117749:Birc5 protein, mouse; D051034:Inhibitor of Apoptosis Proteins; D012097:Repressor Proteins; D000077022:Survivin; C546843:mTOR protein, mouse; D066246:ErbB Receptors; D058570:TOR Serine-Threonine Kinases; D020930:MAP Kinase Kinase Kinases