Class III β-tubulin is one of the seven β-tubulin isotypes identified in the human genome, predominantly in neurons and the testis. It is conditionally expressed in a number of other tissues after exposure to a toxic microenvironment featured by hypoxia and poor nutrient supply.[14][15][16] Posttranslational changes including phosphorylation and glycosylation are required for functional activity.[12]
Class III β-tubulin's role in neural development has warranted its use as an early biomarker of neural cell differentiation from multi potent progenitors.[17] TUBB3 inactivation impairs neural progenitor proliferation. Rescue experiments demonstrate the non-interchangeability of TUBB3 with other classes of β-tubulins which cannot restore the phenotype resulting from TUBB3 inactivation.[18] Congenital neurologic syndromes associated with TUBB3 missense mutations demonstrate the critical importance of class III β-tubulin for normal neural development.[13][19]