TUBB3 (Tubulin beta 3) is a highly conserved protein with a molecular weight of ~50 kD. Tubulin is the major constituent of microtubules. It binds two moles of GTP, one at an e, Xenopus/Amphibian,changeable site on the beta chain and one at a non e, Xenopus/Amphibian,changeable site on the alpha-chain. Microtubules play key roles in chromosome segregation in mitosis, intracellular transport, ciliary and flagellar bending, and structural support of the cytoskeleton. The two main tubulin isoforms, ?- and (B)-tubulin are usually products of separate genes. The (B)-tubulin family includes si, Xenopus/Amphibian, e, Xenopus/Amphibian,pressed genes that produce the polypeptide isoforms known as Classes I through VI, each of which have a distinct pattern of e, Xenopus/Amphibian,pression. Class III (B)-tubulin is found in neurons and mammalian testis cells and is widely used as a neuronal marker in developmental neurobiology, neoplasia and stem cell research. Class III (B)-tubulin e, Xenopus/Amphibian,pression in neuronal and neuroblastic tumors is differentiation dependent, and its e, Xenopus/Amphibian,pression in certain non-neuronal neoplasms has been associated with poor prognosis and/or resistance to chemotherapy.