Figure 4. Avian superfast muscles are enriched for the myosin MYH13 ortholog.

(a) qPCR analysis of syringeal SFM of adult male (N = 3) and (b) female (N = 3, pooled) zebra finch show high enrichment for the MYH13 ortholog in singing males. Legend for color code of bars in b. Unshared lowercase letters a-d indicate post-hoc differences with significance level p<0.05. Fast myosin (MY-32) immunohistochemistry results are shown in Figure 4—figure supplement 1. (c) During the sensorimotor phase of vocal imitation learning in male zebra finches MYH13 is significantly upregulated (N = 3 for each timepoint). Legend for color code of bars in b. Unshared lowercase letters a-c indicate differences with significance level p<0.05. (d) Syrinx SFM significantly increases their speed during song development (N = 4 for each timepoint). FWHM; full width at half maximum.

Figure 4—figure supplement 1. Zebra finch SFM contains two fiber type populations.

(a) Labeling of slow and fast (MY-32) myosin antibodies in adult male zebra finch SFM shows that it contains some myofibrils that express or co-express fast MYH genes, but predominantly fibers that do not react. The latter fibers express the avian MYH13 ortholog. (b) FACS analysis of 801 cells of 4 individuals showing the two fiber populations separate c) best at intensity of 220 as shown by a Kolmogorov-Smirnov test.