Differential expression of gastrointestinal glutathione peroxidase (GI-GPx) gene during mouse organogenesis

Gastrointestinal glutathione peroxidase (GI-GPx) is an antioxidant enzyme that has been known to be restricted to the gastrointestinal tract in rodents. In an effort to determine the expression pattern of GI-GPx mRNA during organogenesis, quantitative real-time PCR and in situ hybridization for GI-GPx mRNA were conducted in whole embryos or each developing organ of mice. GI-GPx mRNA was expressed more abundantly in the extraembryonic tissues, including placenta than in embryos on embryonic days (EDs) 7.5-18.5 (P < 0.05). When compared with the expression levels of cytosolic GPx (cGPx) mRNA, GI-GPx mRNA levels were low in the embryos, but relatively high in the extraembryonic tissues (P < 0.05). According to the results of whole mount in situ hybridizations, GI-GPx mRNA was principally expressed in the ectoplacental cone, neural tube and fold, and primitive heart at EDs 7.5-8.5. At EDs 9.5-12.5, GI-GPx mRNA was abundantly expressed in nervous tissues such as the telencephalon, mesencephalon and dorsal neural tube and was also detected in the forelimb and hindlimb at EDs 10.5-12.5. In the sectioned embryos after ED 13.5, GI-GPx mRNA levels were high in the cerebral cortex, metanephric corpuscle, pancreatic ducts, surface epithelia of the skin, inner ear, and nasal conchae, gastrointestinal tract, liver, urinary bladder, airway passages of lung, and whisker follicles. These findings indicate that GI-GPx is not only spatiotemporally expressed in a variety of embryonic organs during organogenesis but also may perform a mutual compensatory role with the cGPx in the protection of embryos and extraembryonic tissues against the reactive oxygen species generated in ontogenetic periods.