AMINO-ACID-TRANSPORT REGULATION IN PREIMPLANTATION MOUSE EMBRYOS - EFFECTS ON AMINO-ACID CONTENT AND PREIMPLANTATION AND PERIIMPLANTATION DEVELOPMENT

Several nonessential amino acids improve preimplantation development o f mouse embryos in vitro and increase the proportion of the embryos th at implant after transfer to surrogate mothers. The beneficial effects of the amino acids are associated with accumulation of them by embryo s via transport systems that select for the amino acids. Expression of most of the transport systems is developmentally regulated apparently at the level of synthesis and degradation of mRNAs encoding their tra nsport proteins. Since genes encoding pertinent amino acid transport p roteins have now been partially cloned, it will be possible to use tra nsgenic experiments further to test the theory that regulation of amin o acid transport is needed for normal pre- and peri-implantation devel opment.