A basal body (synonymous with basal granule, kinetosome, and in older cytological literature with blepharoplast) is a protein structure found at the base of a

eukaryotic Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bact ...

undulipodium An undulipodium or undulopodium (a Greek word meaning "swinging foot"), or a 9+2 organelle is a motile filamentous extracellular projection of eukaryotic cells. It is basically synonymous to flagella and cilia which are differing terms for similar ...

( cilium or

flagellum A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

). The basal body was named by Theodor Wilhelm Engelmann in 1880 It is formed from a

centriole In cell biology a centriole is a cylindrical organelle composed mainly of a protein called tubulin. Centrioles are found in most eukaryotic cells, but are not present in conifers (Pinophyta), flowering plants ( angiosperms) and most fungi, and a ...

and several additional protein structures, and is, essentially, a modified centriole. The basal body serves as a nucleation site for the growth of the

axoneme An axoneme, also called an axial filament is the microtubule-based cytoskeletal structure that forms the core of a cilium or flagellum. Cilia and flagella are found on many cells, organisms, and microorganisms, to provide motility. The axoneme ...

microtubules. Centrioles, from which basal bodies are derived, act as anchoring sites for proteins that in turn anchor

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 a ...

s, and are known as the

microtubule organizing center The microtubule-organizing center (MTOC) is a structure found in eukaryotic cells from which microtubules emerge. MTOCs have two main functions: the organization of eukaryotic flagella and cilia and the organization of the mitotic and meiotic spi ...

(MTOC). These microtubules provide structure and facilitate movement of vesicles and organelles within many eukaryotic cells.

Assembly, structure

Cilia and basal bodies form during quiescence or the

G1 phase The G1 phase, gap 1 phase, or growth 1 phase, is the first of four phases of the cell cycle that takes place in eukaryotic cell division. In this part of interphase, the cell synthesizes mRNA and proteins in preparation for subsequent steps l ...

of the

cell cycle The cell cycle, or cell-division cycle, is the series of events that take place in a cell that cause it to divide into two daughter cells. These events include the duplication of its DNA (DNA replication) and some of its organelles, and subs ...

. Before the cell enters G1 phase, i.e. before the formation of the cilium, the mother centriole serves as a component of the

centrosome In cell biology, the centrosome (Latin centrum 'center' + Greek sōma 'body') (archaically cytocentre) is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell, as well as a regulator of cell-cycle prog ...

. In cells that are destined to have only one primary cilium, the mother centriole differentiates into the basal body upon entry into G1 or quiescence. Thus, the basal body in such a cell is derived from the centriole. The basal body differs from the mother centriole in at least 2 aspects. First, basal bodies have basal feet, which are anchored to cytoplasmic microtubules and are necessary for polarized alignment of the cilium. Second, basal bodies have pinwheel-shaped transition fibers that originate from the appendages of mother centriole. In multiciliated cells, however, in many cases basal bodies are not made from centrioles but are generated ''de novo'' from a special protein structure called the

deuterosome In cell biology, a deuterosome is a protein structure within a multiciliated cell (such as an epithelial cell of respiratory tract) that produces multiple centrioles. Most cells in human body possess one primary cilium, a relatively small protrus ...

Function

During cell cycle quiescence, basal bodies organize primary cilia and reside at the cell cortex in proximity to plasma membrane. On cell cycle entry, cilia resorb and the basal body migrates to the nucleus where it functions to organize centrosomes. Centrioles, basal bodies, and cilia are important for mitosis, polarity, cell division, protein trafficking, signaling, motility and sensation. Mutations in proteins that localize to basal bodies are associated with several human ciliary diseases, including

Bardet–Biedl syndrome Bardet–Biedl syndrome (BBS) is a ciliopathic human genetic disorder that produces many effects and affects many body systems. It is characterized by rod/cone dystrophy, polydactyly, central obesity, hypogonadism, and kidney dysfunction in so ...

, orofaciodigital syndrome,

Joubert syndrome Joubert syndrome is a rare autosomal recessive genetic disorder that affects the cerebellum, an area of the brain that controls balance and coordination. Joubert syndrome is one of the many genetic syndromes associated with syndromic retinitis pig ...

, cone-rod dystrophy,

Meckel syndrome Meckel may refer to: People German anatomist/physician family Meckel * Johann Friedrich Meckel, the Younger (1781–1833), German anatomist * Johann Friedrich Meckel, the Elder (1724–1774) German anatomist, grandfather of the Younger * Ph ...

, and

nephronophthisis Nephronophthisis is a genetic disorder of the kidneys which affects children. It is classified as a medullary cystic kidney disease. The disorder is inherited in an autosomal recessive fashion and, although rare, is the most common genetic cause o ...

. Regulation of basal body production and spatial orientation is a function of the nucleotide-binding

domain Domain may refer to: Mathematics *Domain of a function, the set of input values for which the (total) function is defined ** Domain of definition of a partial function ** Natural domain of a partial function ** Domain of holomorphy of a function * ...

γ-tubulin Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cyto ...

. Plants lack centrioles and only lower plants (such as mosses and ferns) with motile sperm have flagella and basal bodies.Philip E. Pack, Ph.D., Cliff's Notes: AP Biology 4th edition.

References

External links

* - "Ultrastructure of the Cell: ciliated epithelium, cilia and basal bodies" {{Authority control Organelles