Fig. 1.

Mid1 is expressed in the developing cortex and enriched in axons. (A) Expression of Mid1 mRNA in the developing mouse cortex. CP, cortical plate; I-VI, cortical layer I-VI; IZ, intermediate zone; SVZ, subventricular zone; VZ, ventricular zone; WM, white matter. (B) Mid1 is associated with microtubules and mainly located in axons. Double staining of Mid1 and the indicated markers was performed in polarized neurons at 3 d in vitro (DIV). (C) Mid1 is associated with tubulin in neurons. Coimmunoprecipitation was performed on lysate from cultured cortical neurons at 4 DIV with tubulin antibody. Mouse IgG was used as control. Mid1 and tubulin were detected with specific antibodies. (D) Mid1 is enriched in the axon segment. GFP-transfected neurons were stained for Mid1 at 3 DIV. Relative immunofluorescence intensity of Mid1 in axons and dendrites was quantified. The ratio of the intensity of Mid1 to GFP in dendrites was taken as 1. Results are shown as mean ± SEM. Fourteen neurons were analyzed. ***P < 0.001. Student t test. (Scale bars: A, 200 μm; B and D, 20 μm.)