Production of hFIX in culture by muscle cells stably transfected with pdLMe4βAhIXm1. (▪) indicate uninjected parent cells; (□), cells recovered from the animal muscle tissues 200 days after the original cell implantation. Myoblasts obtained were selected with G418 and pooled for the analysis. Experimental conditions are similar to those in Fig 2B. Averages of triplicate assays are shown with standard deviations (vertical bars).