Bi-paternal mice that survived to adulthood have been successfully created, according to new research published in Cell Stem Cell. This advance has implications for reproductive and regenerative medicine.

Previously, the instability of genomic imprinting has limited the potential of embryonic stem cells to produce viable offspring. In this study, the authors used frameshift mutations, gene deletions and regulatory region edits to introduce 20 genetic modifications that affected hundreds of imprinting genes to address the most severe developmental defects observed in bi-paternal embryos.