Rearrangement of microtubule associated protein parallels the morphological transformation of neurons from dorsal root ganglion.

In primary cultures of dorsal root ganglion cells from rat embryos, neurons undergo a morphological transformation from a bipolar to a differentiated pseudo-unipolar shape, resembling their developmental stages in vivo. Cells present in these cultures are characterized here by immunological criteria using monoclonal and polyclonal antibodies against microtubule associated proteins MAP1 and MAP2 and against tubulin. After development for seven days in culture, antibodies against microtubule associated proteins MAP1 brightly labeled cells with neuronal morphology and lightly stained cells with the shape of Schwann cells. In addition, an extended network of neuronal processes was labeled with this antibody. Anti-microtubule associated protein MAP2 stained only neurons and a more restricted network of neuronal processes. The compartmentalization of microtubule associated protein MAP2 during the maturation process was followed by double-labeling with antibodies to microtubule associated proteins MAP1 and MAP2. Initially, microtubule associated protein MAP2 was present in the cell body and the two processes of bipolar neurons. Subsequently, the labeling of both processes changed, depending on neuronal morphology. In neurons in which both processes were approaching one another, one of these neurites was stained predominantly with anti-microtubule associated protein MAP2. Finally, in pseudo, unipolar neurons, anti-microtubule associated protein MAP2 labeling was found in the cell body and excluded from the more distal processes.