endoreduplication

Endoreduplication is a cellular process in which the genome is duplicated without accompanying cell division, producing polyploid cells with increased DNA content. This change in ploidy typically arises from cycles of DNA replication without mitosis, a mode often referred to as the endocycle. It is distinct from endomitosis, where the cell enters mitosis but fails to complete it; both pathways can yield polyploid nuclei, but their mechanisms differ.

The process can occur through endocycles, in which the cell repeatedly undergoes S phase and gap phases while skipping the M phase. In some contexts, cells may undergo multiple rounds of endoreduplication, leading to 4N, 8N, 16N or higher DNA content within a single nucleus. Endoreduplication is regulated by shifts in cell cycle control networks, including the downregulation of mitotic cyclin-dependent kinases and the upregulation of factors that promote DNA replication without division.

Endoreduplication is widespread in plants and is found in tissues such as leaf mesophyll, fruit flesh, endosperm, and trichomes, where it is linked to cell and organ enlargement and metabolic capacity. In animals, polyploid cells formed by endoreduplication are observed in liver hepatocytes, placental trophoblasts, and certain specialized tissues of insects. The extent and pattern of endoreduplication can be developmentally programmed or responsive to environmental cues and stress.

Functional consequences include increased cell size, greater biosynthetic capacity, and altered gene expression. In agriculture and development, endoreduplication is associated with organ growth and adaptability, while in some disease contexts, abnormal endoreduplication can contribute to genomic instability and pathology.