Identification and characterization of p137 a differentially regulated cardiac marker of embryonic trichloroethylene exposure

Abstract

Embryonic trichloroethylene (TCE) exposure was previously shown to be associated with an increased incidence of cardiac birth defects. Although embryo data are lacking exposure studies on adult animals show an association between halogenated hydrocarbon exposure and modifications in gene expression. The present study was undertaken to identify embryonic mRNA transcripts differentially expressed following TCE or metabolite exposure. This study identified numerous differentially regulated transcripts following halogenated hydrocarbon exposure. Examples of upregulated transcripts include stress responsive genes (Hsp 70, Hsp 70 cognate), a Ca²⁺-ATPase, calreticulin and serum response factor while downregulated transcripts include Midkine (RARP), numerous ribosomal proteins (8s, 18s, 24s), p137 and vimentin. p137 was a candidate sequence marked for further study to determine whether this sequence could be utilized as a molecular marker of TCE exposure. p137 showed a correlation between increased levels of maternal TCE exposure and decreased levels of transcript expressed in E11 fetal tissue. Immunohistochemical staining using an affinity purified antibody to p137 demonstrates widespread expression in rat E11 and chicken St. 17 embryos. p137 protein is broadly expressed in chicken St. 13 through St. 22 heart, but by St. 29 becomes more restricted in the ventricular myocardium with continued endocardial expression. At stages between St. 13 and St. 17 in chick embryos the ectodermal epithelium, yolk sac epithelium, dermatome, developing optic vesicle and neural tube express p137 protein. To explore potential function of p137, atrioventricular explants were exposed to affinity purified p137 antibody. Results show that p137 antibody treatment blocks epithelial-mesenchymal transformation of endothelial cells in-vitro. This study shows that p137 is expressed during rat and chicken mid-gestation in heart and other epithelial tissue derivatives and appears to play a role in the epithelial-mesenchymal transformation of the cardiac atrioventricular cushions. p137 is identified as a useful marker of developmental exposure to halogenated hydrocarbons and its altered expression may contribute to the phenotype of the affected heart.