Centrosomen

Centrosomen are the primary microtubule organizing centers in many animal cells. They reside near the nucleus and typically consist of a pair of cylindrical structures called centrioles surrounded by pericentriolar material, which contains proteins required for nucleating microtubules. The centrioles themselves are built from nine triplets of microtubules arranged in a ring.

Functionally, centrosomes organize the spindle apparatus during cell division and help organize the cytoskeleton during interphase. They anchor and orient microtubules, contributing to cell shape, polarity, and intracellular transport. Microtubule nucleation is driven by gamma-tubulin ring complexes embedded in the pericentriolar material, which seed new microtubules from the centrosome.

Centrosomes duplicate once per cell cycle, during S phase, so that each daughter cell inherits a centrosome. The two centrosomes then separate to form the bipolar spindle required for accurate chromosome segregation in mitosis and meiosis.

Not all eukaryotes possess centrosomes. Plants, many fungi, and some algae lack canonical centrosomes and rely on other microtubule organizing centers or dispersed nucleation sites. In these organisms, spindle poles can form at multiple sites. The mother centriole can also act as a basal body to nucleate cilia or flagella, linking centrosome function to ciliogenesis.

Abnormal centrosome number or structure is linked to cellular instability and disease. Centrosome amplification and structural defects can contribute to chromosomal instability and cancer. Genetic mutations affecting centriole duplication and function are associated with developmental disorders such as microcephaly.