Epon 812

Muscular biopsy was performed in the proband of family 2 to observe the ultrastructure of mitochondria in muscular tissue. Muscular tissue was fixed in 2.5% glutaraldehyde (Sangon Biotech, China) in PBS at 4°C for 2 h. Then, the tissue block was washed three times with PBS, and the block embedded with agar were fixed again with 1% osmium tetroxide for 2 h then washed three times with PBS. The tissue block was dehydrated with an ethanol series and fixed again with Epon 812 (Sangon Biotech, China). The ultrathin (70 nm) sections were collected on Formvar/carbon‐coated nickel grids (Sangon Biotech, China), and the grids were stained with 2.5% uranyl acetate (Sangon Biotech, China) for 7 min followed by lead citrate (Sangon Biotech, China) for 2.5 min, and then the sections were observed with a JEM‐1011 electron microscope (JEOL, Japan).

Cells were fixed in caco-dylate-buffered 1% osmium tetroxide, then dehydrated and embedded in Epon 812 (both Sangon Biotech Co., Ltd.) for ultra-thin sectioning. The ultrastructures of connection protein were examined by TEM using a TecnaiTM-10 electron microscope (FEI Company, Hillsboro, OR, USA) and operated at a high-tension setting of 80 kV with a magnification of x135,000.