binucleate

Binucleate refers to a cell that contains two nuclei within a single cytoplasm. This condition can arise when a cell completes mitosis with karyokinesis but fails to complete cytokinesis, leaving two nuclei in one cell. It can also result from the fusion of two cells or from developmental programs and polyploidization processes that accompany growth and regeneration.

In biology, binucleation is observed in various organisms and tissues. In mammals, binucleate hepatocytes are common in adult liver tissue, where two nuclei per cell are linked to the organ’s regenerative capacity and metabolic demands. Cardiac muscle cells (cardiomyocytes) can also be binucleate in some species and developmental stages, reflecting adaptations to maintain tissue function and protein synthesis.

Beyond animals, binucleation has been reported in other kingdoms as well. In fungi, the dikaryotic stage of many basidiomycetes features cells that harbor two genetically distinct nuclei within the same cell, a condition important for their sexual life cycle. In plants, binucleation can occur in certain tissues as a result of incomplete cytokinesis or endoreduplication, though it is less common than overall polyploidy in plants.

Formation mechanisms commonly involve incomplete cytokinesis after mitosis, direct cell fusion, or nuclear replication without cell division (endomitosis or endoreduplication), leading to two nuclei sharing a single cytoplasm.

Identification is typically achieved by microscopy, using DNA or nuclear stains to reveal two distinct nuclei within a single cell.

See also: multinucleation, endomitosis, dikaryon, syncytium.