The high molecular weight forms of microtubule-associated protein 2 (MAP2a and b) play a central role in the specification of dendrites. RT-PCR amplification of a portion of the N-terminal and middle MAP2b domains of rat spinal cord cDNAs allowed identification of new variants containing both exon 8 (246 bp) and a new exon, 7A (237 bp), located at the beginning of the middle MAP2b region. The brain and the spinal cord express transcripts containing exon 8, whereas exon 7A alone or exons 7A+8 were detected, whatever the developmental stage, only in the spinal cord.
