Microtubules are 25nm diameter protein rods found in most kinds of eukarytic cells. They are polymerized from a dimeric subunit made of one a subunit and one b tubulin subunit. Microtubules are associated with a family of proteins called microtubule associated proteins (MAPs), which includes the protein t (tau) and a group of proteins referred to as MAP1, MAP2, MAP3, MAP4 and MAP5. MAP2 is made up of two approx. 280kDa apparent molecular weight bands referred to as MAP2a and MAP2b. A third lower molecular weight form, usually called MAP2c, corresponds to a pair of protein bands running at approx. 70kDa on SDS-PAGE gels. Antibodies to MAP2 are excellent markers on neuronal cells, their perikarya and neuronal dendrites. In contrast t (tau) is found predominantly in neuronal axons. Dendrite specific MAP is found specifically in the dendritic branching of neurons.