The First Five Days of a Mouse in GEM, Protein-Free Culture Medium

Foundation scientists are deriving new stem cell lines from fertilized mouse eggs in fully defined, protein-free culture medium, GEM (Gamete Embryo Medium). GEM is a specialized fluid that simulates fluids in the womb. By studying time lapse videos of developing mouse embryos, Foundation scientists will pinpoint the exact time to add stem cell growth factors to the culture medium.

Like all mammalian eggs, fertilized mouse eggs are huge cells that undergo several cleavage divisions before entering the uterus for further development. Each day is marked in this video, watch for these stages:

Day 1: Eggs are fertilized and cleave to the 2-cell stage
Day 2: 4-cell stage
Day 3: Morula (8 to 16 cells)
Day 4: Early blastocysts (40-60 cells)
Day 5: Hatching blastocysts (120-250 cells) This when the embryos could implant in the uterus for further development.

GEM, Bedford Research Foundation’s protein-free, chemically-defined embryo culture medium, supports the development of fertilized mouse eggs to blastocysts, the stage at which embryonic stem cells are derived. This unique culture medium has been more than 20-years in the making and is formulated based on the results of experiments designed to determine the most supportive in vitro conditions for assisted reproduction and embryo manipulation (references). The Foundation has made this medium available for research, academic and educational purposes – more info here.