Mitochondrial morphology and function in wild-type, heterozygous and homozygous Cb Cln3Δex7/8 cells a. Confocal and TEM micrographs of wild-type and homozygous CbCln3Δex7/8 mitochondrial morphology are shown. Immunostaining with the inner mitochondrial membrane marker, grp75 (top panels) highlighted elongated mitochondria in homozygous mutant cells (CbCln3Δex7/8/Δex7/8), relative to wild-type mitochondria (CbCln3+/+) (insets, zoom = 2.75x). Mitochondrial distribution was not altered from the wild-type pattern. Elongated homozygous CbCln3Δex7/8 mitochondria were also observed by TEM analysis. 60 × magnification. b. Cellular ATP levels in wild-type, heterozygous and homozygous CbCln3Δex7/8 precursor cells are shown. Wild-type (open bar) and heterozygous (gray bar) CbCln3Δex7/8 cells contained ~39 μM ATP, while homozygous CbCln3Δex7/8 cells (black bar) contained ~1.3 fold reduced levels of ATP (~30 μM), which was statistically significant in a t-test (p < 0.0001). Wild-type and heterozygous CbCln3Δex7/8 cellular ATP levels were not statistically different from each other (p > 0.4). A representative of triplicate experiments is shown (n = 6 in each experiment). c. Cell survival following 24-hour hydrogen peroxide treatment is shown. Homozygous CbCln3Δex7/8 cells were ~2-fold more sensitive to oxidative stress by hydrogen peroxide treatment. Wild-type (circle) and heterozygous (triangle) CbCln3Δex7/8 cells exhibited ~50% survival rates with 75–100 μM H2O2, whereas homozygous CbCln3Δex7/8 cells (squares) had a ~50% survival rate with 50 μM H2O2. A representative of triplicate experiments is shown (n = 4 in each experiment).