Multinucleate

Multinucleate (also multinucleated, polynuclear) cells are eukaryotic cells that have more than one nucleus per cell, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coordinated, synchronous manner where all nuclei divide simultaneously or asynchronously where individual nuclei divide independently in time and space. The multinucleate stage in the life cycle of some organisms is called plasmodium.

Although not normally viewed as a case of multinucleation, plant cells share a common cytoplasm by plasmodesmata, and most cells in animal tissues are in communication with their neighbors via gap junctions.[1]

Mechanisms and types

Multinucleate cells, depending on the mechanism they are formed, can be divided into:[2][3]

Examples

Syncytia

Multinucleate cells can occur naturally under physiological conditions by the fusion of the plasma membranes of cells thus forming syncytia. Examples include the cells of the musculoskeletal systems of mammals, the tapetal cells of plants, and the storage cells of Douglas-fir seeds.[4]

The chlorarachniophytes form multinucleate cells by fusion, being syncytia and not coenocytes. This syncytia is called plasmodium, in the sense of a multinucleate protoplast without a cell wall which exhibits amoeboid movement.[5] Other examples include some plasmodiophorids, some haplosporidians,[6] and the grex of cellular slime moulds (dictyostelids and acrasids).

Coenocytes

Furthermore, multinucleate cells are produced from specialized cell cycles in which nuclear division occurs without cytokinesis, thus leading to large coenocytes or plasmodia. In filamentous fungi, multinucleate cells may extend over hundreds of meters so that different regions of a single cell experience dramatically different microenvironments. Other examples include, the plasmodia of plasmodial slime molds (myxogastrids) and the schizont of the Plasmodium parasite which causes malaria.

Pathological examples

Multinucleated cells can also occur under pathological conditions as the consequence of a disturbed cell cycle control (e.g. binucleated cells and in metastazing tumor cells).

Also in the blood systems of mammals, cells such as neutrophils and eosinophils, are also referred to as polynuclear cells due to their appearance under the microscope.

Multiple nucleoids

The equivalent of multiple nuclei in prokaryotes is multiple nucleoids in bacteria such as in Proteus mirabilis swarmer cells.

References

  1. ↑ http://www.ncbi.nlm.nih.gov/books/NBK26857/
  2. ↑ Boyd, J. D.; Hamilton, W. J. (1966). "Electron microscopic observations on the cytotrophoblast contribution to the syncytium in the human placenta". Journal of anatomy 100 (Pt 3): 535–548. PMC 1270795. PMID 5965440.
  3. ↑ Read, Nick D.; Roca, Gabriela M. (2006). "Chapter 5: Vegetative Hyphal Fusion in Filamentous Fungi". In Baluška, František; Volkmann, Dieter; Barlow, Peter W. Cell-Cell Channels. Landes Bioscience and Springer Science+Business Media. pp. 87–98. ISBN 978-0-387-36058-4.
  4. ↑ Von Aderkas, P.; Rouault, G.; Wagner, R.; Chiwocha, S.; Roques, A. (2005). "Multinucleate storage cells in Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) and the effect of seed parasitism by the chalcid Megastigmus spermotrophus Wachtl". Heredity 94 (6): 616–622. doi:10.1038/sj.hdy.6800670. PMID 15829985.
  5. ↑ Hoek, C. van den, Mann, D.G. and Jahns, H.M. (1995). Algae An Introduction to Phycology. Cambridge University Press, Cambridge
  6. ↑ Brown MW, Kolisko M, Silberman JD, Roger AJ. (2012). Aggregative Multicellularity Evolved Independently in the Eukaryotic Supergroup Rhizaria. Current Biology, Volume 22, Issue 12, 1123-1127.