endomitosis

Endomitosis is a form of cell cycle in which the genome is duplicated without successful cell division, producing a polyploid nucleus. In endomitosis, the cell initiates a mitotic program and chromosomes condense, but cytokinesis fails or is skipped. The net result is an enlarged nucleus containing multiple copies of the genome. Endomitosis is often described as a mitosis-like cycle with incomplete or aborted cytokinesis, and it is sometimes discussed in relation to but distinguished from endoreduplication, in which DNA replication occurs without entry into mitosis.

In humans, the best-described example occurs in megakaryocytes, the bone-marrow-derived precursor cells that give rise to platelets. Megakaryocytes undergo repeated rounds of DNA replication without cell division, becoming polyploid and contributing to platelet production by extending cytoplasmic processes. Endomitosis-like cycles have also been reported in other tissues and organisms, including certain placental cell types and liver or insect tissues, though the frequency and regulation vary widely.

The polyploid state produced by endomitosis is thought to support increased cellular biosynthetic capacity and cell size, enabling higher production of specific proteins or structural components required by differentiating cells. Endomitosis is a normal developmental program in some cell lineages, but dysregulation can be associated with pathologies in others.