(A) HeLa cells were transiently cotransfected with expression constructs encoding either mtDsRed or mtGFP (a-c), and wild-type human protein (d-f), autosomal recessively inherited (Arg120Gln), or dominantly inherited (Arg120Trp, Ala156Gly) (g-i) alleles of GDAP1. The cells were coplated and fused with PEG. Cell hybrids were stained for GDAP1 and analyzed for fusion of the mitochondrial markers mtGFP and mtDsRed. Bars, 10 μm. (B) Quantitation analysis revealed that fusion was similar for controls, GDAP1-transfected hybrids, and hybrids expressing the recessively inherited Arg120Gln. A dramatically impaired fusion was observed for cell hybrids expressing Arg120Trp and Ala156Gly (n = 3, average and standard error are shown, statistically significant levels are shown for the category full fusion; Student t test p value ** <0.005).