Northern blot analysis of hFIX expressed by myoblasts and myotubes. (A) Total cellular RNAs prepared from cells on day 2 (myoblasts) and day 5 (myotubes) in Fig 4 were subjected to Northern blot analysis. Lanes 1 and 2: myoblasts (day 2) and myotubes (day 5) carrying LIXSN, respectively. Lanes 3 and 4: myoblasts (day 2) and myotubes (day 5) carrying pdLMe4βAhIXm1, respectively. Three major bands are seen in lane 4; they are transcription products from LTR and Me4βA, respectively, corresponding to the predicted mRNA size shown in Fig 1. Lane 5: total RNAs prepared from untransfected myotubes. Numbers on the right indicate the RNA molecular size markers and arrows on the left indicate the major hFIX mRNA bands. (B) Hybridization of the same filter membrane with 18S ribosome RNA probe after the dehybridization of the hFIX probe as RNA loading controls.