Fig. 1

Myotubes had fewer, but larger, nucleoli than myoblasts. Immunostaining for nucleolin (green) was used to identify nucleoli and staining for myosin heavy chain (red) was used to distinguish nuclei in myotubes from those in myoblasts. a, a’ Myoblast nuclei, three of which are shown, typically had four or five nucleoli. b, b’ Myotube nuclei, of which four are shown from a single myotube, usually had one to three nucleoli that were typically larger than those in the myoblast nuclei. c Quantitation of nucleoli in myoblasts (light gray bars) and myotubes (dark gray bars) in cultures of healthy control, MDC1A, DUX4-negative FSHD, and LGMD2D myogenic cells. All cultures showed similar decreases in nucleolar number in myotube vs. myoblast nuclei. Error bars = s.e.m. **P < 0.01 by t test. Nucleoli were counted in n = 50 nuclei. d Quantitation of the cross-sectional areas of nucleoli in myoblasts (light gray bars) and myotubes (dark gray bars) in cultures of healthy control, MDC1A, DUX4-negative FSHD, and LGMD2D myogenic cells. All cultures showed similar increases in nucleolar size in myotube vs. myoblast nuclei. Scale bar in A = 20 μm. Error bars = s.e.m. **P < 0.01 by t test. Number of nucleoli measured as indicated on each data bar