Cajal body

Cajal bodies (CBs) are spherical sub-organelles found in the nucleus of proliferative cells like tumor cells, or metabolically active cells like neurons. They were first reported by Santiago Ramón y Cajal in 1903, who called them nucleolar accessory bodies due to their association "with the nucleoli in neuronal cells." Electron microscopists gave them the name "coiled body" because of their shape in EM sections. More recently, in honor of Ramón, they were termed Cajal bodies (CBs).

They are about 0.1 - 2.0 micrometres and are found one to five per nucleus; the number varies over the cell cycle and in different types of cells. Cajal bodies are possibly sites of assembly or modification of the transcription machinery of the nucleus.

Cajal bodies are only found in nuclei of plant, yeast, and animal cells. The cells are usually demonstrating high levels of transcriptional activity, including cells that are rapidly dividing.

CBs are bound to the nucleolus by coilin proteins.