We thank K. Hanley for the DNA extraction protocol; A. Green and A.-C. Chen for genotyping assistance; M. Tran for laser-capture microdissection in an effort to genotype spermatogonia; P. Jain for assistance with fibroblast transfection; H. Cook-Andersen and M. Wilkinson for conversations about mouse germline development; L. Montoliu for discussion of the tyrosinase locus; M. Tuszynski for plasmids and for early support of the project. This work was funded by a Searle Scholar Award from the Kinship Foundation, a Pew Biomedical Scholar Award from the Pew Charitable Trusts, a Packard Fellowship in Science and Engineering from the David and Lucile Packard Foundation, and NIH grant R21GM129448 awarded to K.L.C. E.B. was supported by NIH grant R01GM117321, a Paul G. Allen Frontiers Group Distinguished Investigators Award and a gift from the Tata Trusts in India to TIGS-UCSD and TIGS-India. H.A.G. was supported by a Ruth Stern Graduate Fellowship and by the NIH Cell and Molecular Genetics training grant T32GM724039; V.M.G. was supported by NIH grant DP5OD023098.

Reviewer information

Nature thanks B. Conklin, S. Qi and the other anonymous reviewer(s) for their contribution to the peer review of this work.