Researchers have reconstructed the ancestry of 1.28 million cells in a mouse embryo using DNA Typewriter, a genetic recording system. Covered by ScienceDaily on October 13, the study appeared in Science on October 8, 2026. UW Medicine says the work follows development from the first cell division through 13.5 days, when organs have taken shape.
Jay Shendure of the University of Washington in Seattle and Chengxiang Qiu of Dartmouth College led the study. Mammalian embryos develop inside the mother, making extended direct observation difficult. The research instead uses inherited DNA markings to reconstruct relationships after development, according to the researchers.
The team placed a redesigned recording sequence in a fertilized mouse egg. DNA Typewriter adds successive marks that descendants inherit, allowing shared ancestry to be read from their genetic records. The paper describes a time-calibrated family tree linking cell identities to their developmental history, rather than a continuous film of the embryo.
UW Medicine reports that recording was attempted in 100 fertilized eggs, producing 10 embryos for examination. Detailed analysis focused on embryo number three, which had the richest active record. The findings therefore describe a detailed reconstruction from one embryo, rather than evidence that the method performs equally well in every mouse.
According to the team, one of the first two cells produced more descendants, but both generated diverse cell types in almost equal proportions. Blood and retinal cells settled into their identities relatively early; the outer skin layer did so later. These different schedules agree with earlier developmental research, the university said.
The researchers see potential to investigate how organs form and how development goes wrong in birth defects or cancer. The Howard Hughes Medical Institute also describes genetic recording as a way to study processes hidden from direct observation. These are research possibilities: the mouse experiment does not establish a human treatment or demonstrate clinical benefit.
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