Ephrin-A3 is expressed on all MyHC-I^+ve (slow) myofibers. (A–F) Immunohistochemistry showing localization of ephrin-A3 (green) compared with two of three fast MyHCs (red: MyHC-I, top row; MyHC-IIa, middle row; and MyHC-IIb, bottom row), along with nuclei (DAPI, blue) and laminin (white) on transverse cryosections from uninjured gastrocnemius (G), plantaris (P), soleus (S), TA (T), and EDL (E) muscles. The yellow boxes in the left of each panel indicate the magnified regions on the top right, which are separated underneath to show expression of MyHC/laminin (left) and ephrin-A3/laminin (right). (A and B) All slow, MyHC-I^+ve myofibers in all muscles of the distal hindlimb express ephrin-A3. (C and D) No fast, MyHC-IIa^+ve myofibers in the distal hindlimb express ephrin-A3. (E and F) Ephrin-A3 is also never expressed by fast, MyHC-IIb^+ve myofibers. (G) Fiber type distribution of the TA, EDL, and soleus muscles (n = 3) in adult: each muscle has a unique and consistent ratio of the four myofiber types. Whole muscle montage gamma = 1.45. Bars: (montages) 1 mm; (insets) 300 µm. MH, gastrocnemius medial head; LH, lateral head.