Previous studies in humans, chicks, and rats suggested that TCE is a teratogen with a remarkable specificity for the developing heart. In the past few years our laboratory has used an in vitro culture model, and a PCR-based subtractive hybridization technique to explore some of the cellular and molecular aspects of TCE exposure on heart development. In particular, we isolated several molecules whose level of expression was altered by TCE in the embryonic heart. Two of these molecules, a p137 and a SERCA 2-like protein, were selected for further characterization, since TCE was able to inhibit their level of expression in a dose-response fashion.
The inhibitory effect of TCE on p137 expression was confirmed by Western analysis in which protein isolated from heart or embryo exposed to 110 ppm TCE was probed with p137 polyclonal antibodies. Using an in vitro collagen gel assay, the same antibodies inhibited the total number of mesenchymal cells that invade into collagen gel. Furthermore, in situ hybridization experiments indicate that p137 antibodies specifically stain the ventricular septum and walls of atria of stage 29 chicken heart, as well as several epithelial tissues. Further characterization of the SERCA-like cDNA is now in progress, in order to identify the SERCA 2 isoform (2a or 2b) which is sensitive to TCE.
In summary, we were able to identify molecules whose expression was altered in the heart as a consequence of maternal exposure to TCE. Some of these molecules can be used to identify actual effectors of birth defects. Alternatively, they might prove useful as specific bio markers of environmental exposure.