Tubulin microheterogeneity increases with rat brain maturation [22]

MICROTUBULES are present in all eukaryotic cells and have been found to have a variety of structural and dynamic roles in cell shape, division, motility, transport and secretion¹. In nervous tissue neurite outgrowth and axoplasmic transport are also thought to depend on microtubule integrity². The micro-tubule subunit protein, tubulin, is a heterodimer composed of two polypeptides α and β (refs 3,4). The α and β subunits show microheterogeneity and both have been resolved into two or three components^5-8. The question therefore arises as to whether changes occur in the relative proportions of the multiple forms of tubulin upon assumption of different roles within the nerve cell. We show here that cytoplasmic rat brain tubulin, as resolved by isoelectric focusing, is highly heterogeneous. Moreover, tubulin microheterogeneity seems to be developmentally determined, increasing from seven to nine distinct components during early postnatal rat brain maturation. However, extensive tubulin microheterogeneity is prominent in the brain, as tubulin from other organs is less heterogeneous.