Centriole
Cylindrical organelle key to cell division and cilia formation.
A centriole is a cylindrical organelle found in most eukaryotic cells, composed primarily of the protein tubulin. It is absent in conifers, flowering plants, and most fungi, and is present only in the male gametes of certain plant groups such as charophytes, bryophytes, seedless vascular plants, cycads, and Ginkgo. Typically, a centriole is constructed from nine sets of short microtubule triplets arranged in a cylinder, though some organisms deviate from this pattern: crabs and *Drosophila melanogaster* embryos have nine doublets, while *Caenorhabditis elegans* sperm cells and early embryos feature nine singlets. Additional proteins associated with centrioles include centrin, cenexin, and tektin. A bound pair of centrioles, surrounded by a dense mass called pericentriolar material (PCM), forms a centrosome, which serves as the cell’s primary microtubule-organizing center. Centrioles play key roles in forming cilia during interphase and organizing the aster and mitotic spindle during cell division. The centrosome was first observed by Walther Flemming in 1875 and Edouard Van Beneden in 1876; Van Beneden later noted it consisted of two orthogonal centrioles in 1883. Theodor Boveri coined the term "centrosome" in 1888 and "centriole" in 1895, while Theodor Wilhelm Engelmann named the basal body in 1880. The pattern of centriole duplication was independently elucidated by Étienne de Harven and Joseph G. Gall around 1950. Centrioles can self-replicate during cell division. Prior to DNA replication, a cell contains an older mother centriole and a younger daughter centriole. During S phase, a procentriole forms at the proximal end of each existing centriole and elongates through G2 and M phases, remaining orthogonally attached. During mitosis, the centrosome splits into two, each containing one centriole pair that forms a spindle pole. After division, mother and daughter centrioles disengage via separase. Centriole duplication is tightly regulated to occur once per cell cycle and is coordinated with DNA replication. Sperm centrioles are crucial for forming the flagellum and for embryo development; in humans, the oocyte lacks centrioles, and the sperm donates a proximal and distal centriole to form the zygote’s first centrosome. Proper centriole positioning is vital for establishing left-right asymmetry in mammalian development, and defects in centriole migration ar
- discovered_by
- Walther Flemming and Edouard Van Beneden
Lore & Background
The pattern of centriole duplication was first worked out independently by Étienne de Harven and Joseph G. Centrioles are involved in organizing the mitotic spindle and completing cytokinesis. Experiments have shown that cells whose centrioles have been removed via laser ablation can still progress through the G1 stage of interphase before centrioles can be synthesized de novo. Mutant flies lacking centrioles develop normally, but adult flies' cells lack flagella and cilia, leading to death shortly after birth. Centrioles can self-replicate during cell division. Sperm centrioles are important for formation of the sperm flagellum and sperm motility, as well as for development of the embryo after fertilization. In humans, the oocyte is acentriolar, and the sperm donates two structurally distinct centrioles: the proximal centriole and the distal centriole, which contribute to formation of the first centrosome in the zygote.
Reader's Guide
Centrioles are fundamental to cellular organization and reproduction. As key components of centrosomes, the cell's primary microtubule-organizing centers, they play a central role in organizing the cytoplasmic microtubule network, contributing to nuclear positioning and spatial arrangement of the cell. During cell division, centrioles organize the mitotic spindle and are involved in completing cytokinesis. Their role in ciliogenesis is critical: the mother centriole becomes the basal body that determines the position of flagella or cilia. Inability of cells to use centrioles to make functional flagella and cilia has been linked to genetic and developmental diseases, including Meckel–Gruber syndrome. Proper orientation of cilia via centriole positioning is critical for establishing left-right asymmetry during mammalian development. The last common ancestor of all eukaryotes was a ciliated cell with centrioles, though some lineages like land plants lack centrioles except in motile male gametes. Atypical centrioles, which lack microtubules or have non-radial symmetry, have evolved multiple times independently, possibly to enhance sperm function by coupling tail beating with head kinking.
Did You Know?
- Centrioles are typically made of nine sets of short microtubule triplets arranged in a cylinder, but deviations include nine doublets in crabs and Drosophila melanogaster embryos, and nine singlets in Caenorhabditis eleg
- Cells whose centrioles have been removed via laser ablation can still progress through the G1 stage of interphase before centrioles can be synthesized de novo.
- The last common ancestor of all eukaryotes was a ciliated cell with centrioles.
Frequently Asked Questions
Who is Centriole?
Centriole is a small cylindrical organelle built primarily from tubulin, typically arranged as nine microtubule triplets in a ring. It is present in most eukaryotic cells but notably absent in conifers, flowering plants, and the majority of fungi.
What are Centriole's powers or role?
During interphase it nucleates and helps form cilia, and during mitosis it organizes the aster and the mitotic spindle so chromosomes can segregate properly. In short, it acts as the structural director that sets up the cell's division machinery.
What happens to Centriole after cell division?
Each daughter cell inherits one centriole pair, which then duplicates during the next S phase to be ready for the following round of division. It is a recurring structural role rather than a one-time event, so there is no single 'ending' to its story.
Why is Centriole important?
It ensures the mitotic spindle assembles correctly so chromosomes are distributed accurately, and it anchors the base of cilia. Without it, both faithful cell division and ciliary function would be severely compromised.
Who discovered Centriole?
Walther Flemming and Edouard Van Beneden first identified this structure during their 19th-century studies of cell division.
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