Fig. 1

MAP6 isoforms are present in mice skeletal muscle. a Structure of the MAP6 gene and of the major mRNA isoforms obtained by the alternative splicing of the four exons or the use of an alternative promoter in the case of MAP6-F. The dashed lines represented for each isoform, the localization of the start, and the stop codons. The localization of the antigen for the 23N antibody is represented. The localization of the primers used to amplify the four exons is represented by the arrowheads. b RT-PCR amplifications from muscle (M), brain (B), or C2C12 myotube (C) extracts, with H₂O (H) instead of cDNA as a negative control. PCR fragments at sizes corresponding to MAP6-N, E and F transcripts were amplified from brain homogenates: 443 bp for exons 1–3 (N/E), and 373 bp (major-N) and 176 bp (minor-F) for exons 2–4. In muscle homogenates and in C2C12, PCR fragments of the same size as in brain homogenates were amplified. c RT-q-PCR amplification of MAP6 transcripts in brain or muscle extracts, from three different mice, compared to β-actin. d Western blot analysis has been performed with antibody 23N on 60 ng whole brain homogenates prepared from WT or MAP6-KO animals, and 50 μg of muscle homogenate prepared from WT or MAP6-KO skeletal muscle (three mice of each genotype). In brain, five proteins are detected, the N, O, E, A, and an un-characterized 48-kDa isoform (48). The three bands specifically detected in WT skeletal muscle at 130 kDa (N-isoform), 75 kDa (E-isoform), and 42 kDa (F-isoform) are marked with arrows. The muscle-specific triadin isoform Trisk 95 (T95) has been used as a loading control (lower panel). e Western blot analysis has been performed with antibody 23N on C2C12 homogenate or 3 days WT and MAP6-KO myotube (MT) homogenates. GAPDH has been used as a loading control (lower panel)