Effects of alpha-amanitin on programming of mouse blastocyst development

We have investigated the effect of alpha-amanitin treatment of mouse blastocysts on their further development. Twenty-four-hour treatments with alpha-amanitin at 1 microg/ml do not interfere with embryo survival or gross morphological development over the next few days although the rate of synthesis of polyA-containing RNA is dramatically reduced during exposure to the antimetabolite. Effects upon rates of protein synthesis are not observed initially, but incorporation of (35S)methionine into acid-insoluble material is ultimately inhibited by approximately 50% in all the treated samples. Developmental markers do not all respond in the same way to the alpha-amanitin treatments used. Whereas levels of beta-glucuronidase and plasminogen activator are virtually unaffected by the antimetabolite, alpha-amanitin treatment interferes with delta5,3beta-hydroxysteroid dehydrogenase activity in trophoblast cells and formation of a bilayered inner cell mass. The effects upon the latter markers differ quantitatively with the various exposure periods to alpha-amanitin. On the basis of these observations, we propose that mRNAs for at least some developmental markers in mouse blastocysts are synthesized long before they are translated.