Finally, because subunit c is a mitochondrial protein and its turnover proceeds through autophagic engulfment of mitochondria [13], we analyzed homozygous CbCln3Δex7/8 cell mitochondrial morphology and function. Mitochondrial distribution in homozygous CbCln3Δex7/8 cells was indistinguishable from wild-type and heterozygous cells; however, homozygous CbCln3Δex7/8 mitochondria appeared more elongated by grp75 marker immunostaining and TEM analysis (Fig. 8a). 72% of homozygous mutant mitochondria were greater than 0.6 μm in length (range = 0.26 μm to 2.75 μm), while fewer wild-type mitochondria (51%) reached this length (range = 0.15 μm to 2.29 μm). Mitochondrial width was not altered in homozygous CbCln3Δex7/8 cells (data not shown). Moreover, compared to wild-type or heterozygous cells, homozygous CbCln3Δex7/8 cells had significantly reduced cellular ATP levels (1.3 fold less, Fig. 8b) and exhibited reduced survival following hydrogen peroxide treatment (~50% of wild-type survival, Fig. 8c), suggesting impaired energy metabolism and oxidative stress response. Taken together, these data support impaired mitochondrial function in homozygous CbCln3Δex7/8 cells.