We thank D. Schatz, C. Murre and J.-P. Changeux for discussions; the UCSD ADRC and the UCI MIND for human brain specimens, along with the donors and families who shared these precious materials; flow cytometry core colleagues B. Seegers, M. Haynes (TSRI) and Y. Altman (SBP); and M. Wang (ACD), D. J. Weiss (Agilent) and H. Lee (PacBio) for technical assistance. Support was provided by The Shaffer Family Foundation, The Bruce Ford & Anne Smith Bundy Foundation, a UCSD pilot grant (NIH P50AG00513) and SBP institutional funds (J.C.); a PRAP fellowship from the Ministry of Science and Technology, Taiwan (105-2917-I-564-085, M.-H.L.); and NIH training grant 5T32AG000216-24 (G.E.K.).

Reviewer information

Nature thanks L. Feuk, F. Gage and the other anonymous reviewer(s) for their contribution to the peer review of this work.