Abasal body (synonymous withbasal granule,kinetosome, and in older cytological literature withblepharoplast) is a protein structure found at the base of aeukaryoticundulipodium (cilium orflagellum). The basal body was named byTheodor Wilhelm Engelmann in 1880.^[1][2] It is formed from acentriole and several additional protein structures, and is, essentially, a modified centriole.^[3][4] The basal body serves as a nucleation site for the growth of theaxoneme microtubules. Centrioles, from which basal bodies are derived, act as anchoring sites for proteins that in turn anchormicrotubules, and are known as themicrotubule organizing center (MTOC). These microtubules provide structure and facilitate movement of vesicles and organelles within many eukaryotic cells.

Cilia and basal bodies form during quiescence or theG1 phase of thecell cycle. Before the cell enters G1 phase, i.e. before the formation of the cilium, the mother centriole serves as a component of thecentrosome.

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 two 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.^[5]

In multiciliated cells, however, in many cases basal bodies are not made from centrioles but are generatedde novo from a special protein structure called thedeuterosome.^[6]

During cell cycle dormancy, 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.^[7]

Mutations in proteins that localize to basal bodies are associated with several human ciliary diseases, includingBardet–Biedl syndrome,^[8]orofaciodigital syndrome,^[9][10]Joubert syndrome,^[11]cone-rod dystrophy,^[12][13]Meckel syndrome,^[14] andnephronophthisis.^[15]

Regulation of basal body production and spatial orientation is a function of the nucleotide-bindingdomain ofγ-tubulin.^[16]

Plants lack centrioles and only lower plants (such as mosses and ferns) with motile sperm have flagella and basal bodies.^[17]

• Histology image: 21804loa – Histology Learning System at Boston University - "Ultrastructure of the Cell: ciliated epithelium, cilia and basal bodies"

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