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Microtubule-associated protein 2, commonly called MAP2, is a neuronal protein associated with microtubules and strongly enriched in many dendrites. It contributes to organization of the dendritic cytoskeleton. Enrichment makes it useful as an experimental marker, but marker abundance and the full functional identity of a cell compartment are different properties. ^[ref]

In cultured hippocampal neurons, MAP2 immunostaining helped confirm dendritic identity after processes had been followed through development. ^[ref] Combining time-resolved shape changes with a molecular marker is more informative than calling every short process a dendrite. Developmental stage, isoform and preparation conditions also matter when interpreting staining.

Neuronal polarity is the structural and molecular differentiation of a neuron into compartments such as an axon and dendrites. Different distributions of proteins, transport machinery and synapses support different roles in receiving and sending signals. This organization does not require every electrical event to travel in only one direction: action potentials can propagate back into dendrites.

In 1988, Carlos G. Dotti, Christopher A. Sullivan and Gary A. Banker followed individual embryonic rat hippocampus neurons in culture using repeated photography and time-lapse imaging. Several initially similar neurites preceded rapid growth of one future axon; staining for microtubule-associated protein 2 helped distinguish later dendrites. Following the same biological cells over time directly tested the developmental sequence, which a collection of mature shapes could only suggest.^[ref]