Mapple lifeact 7

WI-38 VA13 cells (JCRB9057; SV40-transformed WI-38 human embryonic lung fibroblasts) were obtained from the Health Science Research Resources Bank (Osaka, Japan). These cells were cultured in MEM-alpha (GIBCO/Life Technologies, Carlsbad, CA) supplemented with 10% fetal bovine serum (FBS), 50 U/mL penicillin, and 50 µg/mL streptomycin at 37°C in a humidified incubator containing 5% CO2. pEGFP-NMHC-IIA and pEGFP-NMHC-IIB were kind gifts from Dr. Robert S. Adelstein (NIH, Bethesda, MD). pmCherry-NMHC-IIA was constructed as previously described [18] . mApple-lifeact-7 (plasmid no. 54747) was purchased from Addgene (Cambridge, MA).
Cells were transfected with plasmids using X-fect Transfection Reagent (Takara Bio USA, Mountain View, CA) in antibiotic-free MEM-alpha supplemented with 10% FBS. Rabbit polyclonal anti-NMHC-IIA and anti-NMHC-IIB antibodies targeting the carboxyl termini of NMHC-IIA and NMHC-IIB, respectively, were used as previously described [19, 20] . Alexa Fluor 488-conjugated goat anti-rabbit IgG (H+L) and Cy3-conjugated goat anti-rabbit IgG (H+L) were purchased from Jackson ImmunoResearch Laboratories (West Grove, PA). TRITC-conjugated phalloidin was purchased from Sigma-Aldrich (St. Louis, MO). Alexa Fluor 350-conjugated phalloidin was purchased from Molecular Probes (Eugene, OR). Type-I collagen (Cell matrix I-C) was purchased from Nitta Gelatin (Osaka, Japan).