Expression of aldehyde dehydrogenase family 1, member A3 in glycogen trophoblast cells of the murine placenta.

INTRODUCTION Retinoic acid (RA) signaling is a well known regulator of trophoblast differentiation and placental development, and maternal decidual cells are recognized as the source of much of this RA. We explored possible trophoblast-derived sources of RA by examining the expression of RA synthesis enzymes in the developing mouse placenta, as well as addressed potential sites of RA action by examining the ontogeny of gene expression for other RA metabolizing and receptor genes. Furthermore, we investigated the effects of endogenous RA production on trophoblast differentiation. METHODS Placental tissues were examined by in situ hybridization and assayed for RARE-LacZ transgene activity to locate sites of RAR signaling. Trophoblast stem cell cultures were differentiated in the presence of ALDH1 inhibitors (DEAB and citral), and expression of labyrinth (Syna, Ctsq) and junctional zone (Tpbpa, Prl7b1, Prl7a2) marker genes were analyzed by qRT-PCR. RESULTS We show Aldh1a3 is strongly expressed in a subset of ectoplacental cone cells and in glycogen trophoblast cells of the definitive murine placenta. Most trophoblast subtypes of the placenta express RA receptor combinations that would enable them to respond to RA signaling. Furthermore, expression of junctional zone markers decrease in differentiating trophoblast cultures when endogenous ALDH1 enzymes are inhibited. DISCUSSION Aldh1a3 is a novel marker for glycogen trophoblast cells and their precursors and may play a role in the differentiation of junctional zone cell types via production of a local source of RA.