A team of stem cell scientists have successfully used embryonic stem cell engineering to create a bi-paternal mouse—a mouse with two male parents—that lived until adulthood.

Their results, published on January 28, 2025, in Cell Stem Cell, describe how targeting a particular set of genes involved in reproduction allowed the researchers to overcome previously insurmountable challenges in unisexual reproduction in mammals.

Scientists have attempted to create bi-paternal mice before, but the embryos developed only to a certain point and then stopped growing. Here, the investigators, led by corresponding author Wei Li of the Chinese Academy of Sciences (CAS) in Beijing, focused on targeting imprinting genes, which regulate gene expression in a number of ways.