Glutathione synthesis is essential for mouse development but not for cell growth in culture

Glutathione (GSH) is a major source of reducing equivalents in mammalian ce lls. To examine the role of GSH synthesis in development and cell growth, w e generated mice deficient in GSH by a targeted disruption of the heavy sub unit of gamma-glutamylcysteine synthetase (gamma GCs-HStm1), an essential e nzyme in GSH synthesis. Embryos homozygous for gamma GCS-HStm1 fail to gast rulate, do not form mesoderm, develop distal apoptosis, and die before day 8.5. Lethality results from apoptotic cell death rather than reduced cell p roliferation. We also isolated cell lines from homozygous mutant blastocyst s in medium containing GSH. These cells also grow indefinitely in GSH-free medium supplemented with N-acetylcysteine and have undetectable levels of G SH; further, they show no changes in mitochondrial morphology as judged by electron microscopy. These data demonstrate that GSH is required for mammal ian development but dispensable in cell culture and that the functions of G SH, not GSH itself, are essential for cell growth.