The myogenic cell fraction of expanded cells was quantified using flow cytometry for the myoblast surface antigens CD56+CD29+ (Fig. 1b, c)25,26 and found to be similar between healthy and Pompe disease cells (65.8 ± 7.4% and 76.4 ± 5.6% myoblasts, respectively). Here, ITGB1 is linked to glycogen storage disease II.