Embryotoxic effects of the marine biotoxin okadaic acid on murine embryonic stem cells

Okadaic acid (OA), a marine toxin produced by dinoflagellates, can accumulate in various bivalve molluscs. In humans, consumption of OA induces acute toxic effects like diarrhoea, nausea, vomiting and abdominal pain. OA is a potent inhibitor of protein phosphatase 1 (PP1) and 2A (PP2A), enzymes that are known to be critical regulators of embryonic development. To determine the embryotoxic potential of OA, we performed two independent cellular in-vitro assays, both of which are applicable for the detection of teratogenic compounds: (i) the validated embryonic stem cell test (EST) based on the morphological analysis of beating cardiomyocytes in embryoid bodies and (ii) the F9 cell assay quantifying the induction of cell differentiation by measuring the emitted luminescence of a reporter gene. In the presence of OA, beating cardiomyocytes in the EST were inhibited and the reporter gene in transiently transfected F9 cells was activated. Furthermore, OA treatment led to rapid morphological changes including cell rounding, the loss of cell-cell contacts and changed electrical impedance as monitored in real time by the xCELLigence system. The two independent bioassays (EST and F9 cell test) detected OA as a potential embryotoxic compound, since OA influences the differentiation process of cultured murine embryonic cells.