Changes in composition and activity of microtubule-associated proteins during brain development.

The onsert of neuronal differentiation is characterised by intensive neurite growth; because microtubule formation is strictly required during this process, in vitro assembly of the tubulin present in the rat brain has been studied at different stages of development: the rate of assembly is very slow in the early stages and increases progressively with age from birth until adulthood. Other data also suggested that the limiting factor in the young brain is the amount or activity of one or several of the minor components which co-polymerise into microtubules with tubulin. We show here that both the composition and the activity of the microtubule-associated proteins change during the time course of rat brain development.