MAP2, a 280-kD protein, is highly concentrated in neuronal somata and dendrites. By in situ hybridization with specific cDNA probes, Garner et al. (1988) showed that mRNA for the dendrite-specific microtubule-associated protein MAP2 was present in dendrites in the developing brain. By contrast, the mRNA for tubulin (MIM.191120), a protein present in both axons and dendrites, was localized exclusively in neuronal cell bodies.
Neuronal polarization
The microtubule-associated proteins (MAPs) isolated from brain coassemble with tubulin into microtubules in vitro.
For nerve cells to develop their highly polarized form, appropriate structural molecules must be targeted to either axons or dendrites. This could be achieved by the synthesis of structural proteins in the cell body and their sorting to either axons or dendrites by specific transport mechanisms.
For dendrites, an alternative possibility is that proteins could be synthesized locally in the dendritic cytoplasm. This would allow regulation of the production of structural molecules in response to local demand during dendritic development.
The existence of dendritic polyribosomes and the demonstration that newly synthesized RNA is transported into the dendrites of neurons differentiating in culture support the feasibility of dendritic protein synthesis.
Isoformes
Kindler and Garner (1994) noted that MAP2 can be resolved by SDS-PAGE into at least 3 isoforms. The 280-kD MAP2B is present throughout rat brain development, and the slightly larger MAP2A appears first during the end of the second week of postnatal life.
MAP2C is composed of several bands of about 70 kD, is present during early brain development, and largely disappears from the mature brain except for the retina, olfactory bulb, and cerebellum. MAP2A and MAP2B are encoded by 9-kb mRNAs, and MAP2C by a 6-kb transcript.
Immunochemistry
Microtubule associated protein-2 (MAP-2) is a marker of neuronal differentiation and is used to detect ganglion cells in formalin-fixed, paraffin-embedded tissue sections.
MAP-2 antibody is a sensitive and specific immunohistochemical marker that can confirm ganglion cells in paraffin-embedded rectal suction biopsies and may eliminate the need for repeat biopsy in select cases. (19363440)
References
Microtubule-associated protein-2 is a sensitive marker of primary and metastatic neuroblastoma. Krishnan C, Higgins JP, West RB, Natkunam Y, Heerema-McKenney A, Arber DA. Am J Surg Pathol. 2009 Nov;33(11):1695-704. PMID: 19701075
Utility of Microtubule Associated Protein-2 (MAP-2) Immunohistochemistry for Identification of Ganglion Cells in Paraffin-Embedded Rectal Suction Biopsies. Burtelow MA, Longacre TA. Am J Surg Pathol. 2009 Apr 9. PMID: 19363440