Overcoming gene dosage barriers in mammalian development: An imprinting balancing act

Genomic imprinting ensures parent-of-origin gene expression and prevents uniparental development. In this issue of Cell Stem Cell, Li et al.¹ extensively engineered androgenic haploid embryonic stem cells to overcome imprinting barriers, producing adult bi-paternal mice, albeit with low efficiency, and providing insights into roles of imprinted genes in development.