Phosphorylated MAP‐1B isoforms in the developing mouse barrel cortex

Abstract

Developmental expression of two phosphorylation modes of microtubule-associated protein 1B (MAP-1B) has been studied in the barrel cortex of mice at postnatal days (P)5, P12, P21 and P90 using immunocytochemistry with antibodies 125 and 150 that recognize phosphorylation modes II and I, respectively. The antibody 125 immunoreactive processes, identified as dendrites, are not yet detectable at P5; they are already present at P12 and become more evident at P21. In the barrel cortex of P90 animals the antibody 125 immunopositive dendrites are still present, although they are much less pronounced. The antibody 150 punctate immunostaining seen at P5 is not detectable at P12. At P21, however, thin immunopositive fibres appear, implicating a re-expression of the microtubule-associated protein 1B phosphorylation mode I in a portion of axons. The antibody 150 immunopositive axons are no longer present in the P90 barrel cortex. The re-expression of the MAP-1B phosphorylation mode I, which is a juvenile isoform characteristic for growing axons, may imply induction of mechanisms providing mouse barrel cortex neurons with the potency for plastic changes at a terminal stage of synaptogenesis.

Microtubule-binding protein MAP1B regulates interstitial axon branching of cortical neurons via the tubulin tyrosination cycle

“…In addition, we find that GSK3β-mediated phosphorylation of MAP1B is also necessary for collateral axon branch formation since overexpression of dephosphomimetic MAP1B mutant prevented GSK3β-induced axon branching. In agreement with this hypothesis, enrichment of mode I phosphorylated MAP1B has been observed in layer 5 axons in developing mouse cortex, (Majewska and Skangiel-Kramska, 2000 ) and our immunostaining data also support this observation. Thus, we propose a ‘MAP1B brake’ model in which a brake on the formation of interstitial axon branches is released by GSK3β-mediated MAP1B phosphorylation.…”

MAP1B Regulates Cortical Neuron Interstitial Axon Branching Through the Tubulin Tyrosination Cycle

“…Interestingly, enrichment of mode I phosphorylated MAP1B has indeed been observed in layer 5 axons in developing mouse cortex. 67 Thus, we propose a ‘MAP1B brake’ model in which a brake on the formation of interstitial axon branches is released by GSK3β-mediated MAP1B phosphorylation.…”