In 1958 McLaren and Biggers published what was undoubtedly one of the most important papers in the history of developmental biology, on the in vitro culture of mouse embryos. These important experiments demonstrated the viability of embryo culture and transfer, and were vital steps on the path to human “test tube babies”. However, what is often neglected is why Anne McLaren was interested in embryo transfer in the first place.

Throughout the 1950’s, Anne and her husband Donald Michie, performed a series of experiments to investigate the developmental basis of vertebral variation in mice, in particular the difference between strains with 5 lumbar vertebrae, and those with the usual 6. Embryo transfer experiments showed that this phenotype was the result of the uterine environment, not genetics, but this finding was somewhat overshadowed by the technical achievements.

We now have the tools and resources to revisit that question, and that what I’m doing…