Antisense MAP‐2 oligonucleotides induce changes in microtubule assembly and neuritic elongation in pre‐existing neurites of rat cortical neurons

Microtubule‐associated protein 2 (MAP‐2) is an abundant component of the cytoskeleton present in dendrites and cell bodies of neurons of the CNS. To examine the biological function of MAP‐2, two MAP‐2 antisense (AS) oligonucleotides complementary to the 5′ region of the rat MAP‐2 cDNA were added to rat primary embryonic day 17–18 (E17‐18) cultured cortical neurons 24 h after plating and neurite outgrowth and morphology studied. The treatment of primary cortical cultures with either of the two MAP‐2 AS oligonucleotides resulted in decreased MAP‐2 and reduction in the number of neuritic processes relative to the control or MAP‐2 sense‐treated cultures. By immunostaining and light microscopy the AS‐treated neurons appeared smaller, more rounded, and less intensely stained for MAP‐2 than the untreated or the MAP‐2 sense‐treated cultures. By electron microscopy disorganized microtubules and a reduction in the number of microtubules within neurites of the AS‐treated cultures were observed. We conclude that MAP‐2 continues to be required for microtubule spacing and stability within neurites once they have formed. © 1994 Wiley‐Liss, Inc.