Cells — and their nuclei — are affected by dynamic forces during embryonic development. In mammals, the nuclear lamin proteins assemble into a filamentous meshwork at the nuclear periphery that strengthens the nucleus. This structure is commonly referred to as the nuclear lamina. In addition to its structural role, the nuclear lamina has been implicated in fundamental cellular processes including DNA replication, genome organization and gene regulation. And yet, mutations in the lamin genes cause a group of so-called laminopathy diseases, which have tissue-restricted phenotypes, raising questions such as whether lamins are essential, and if so, in which contexts.

In the follow-up paper, Zheng and colleagues reported that in fact all three nuclear lamin genes are completely dispensable for the survival of embryonic stem cells. These lamin-null cells could proliferate, differentiate and maintain a normal euploid genome. Even more surprisingly, these cells could pass the ‘gold standard’ test of pluripotency: they could generate teratomas that contained cells committed to forming endoderm, ectoderm and mesoderm lineages when transplanted into mice.