mtDNA and nucleoid distributions are dismantled by OPA1-exon4b silencing. (A) Fluorescence images using anti-DNA and Mitotracker of HeLa cells (control, top) and cells transfected with the exon 4b siRNA (siRNA4b, bottom) reveal a dramatic change in mtDNA distribution in cells silenced for exon 4b, whereas the mitochondrial network remains tubular as in control cells. (B) Quantifications of cytoplasmic anti-DNA fluorescence (top, relative units) and of the number of nucleoids per cell (bottom) in control (Cont) and exon 4b siRNA-transfected cells (si4b) disclose a decrease in mtDNA-associated fluorescence (50%) and in the number of nucleoids (60%), in exon 4b–silenced cells (n = 8; Student's t-test; [*] P-value inferior to 0.01). (C) Distribution of the anti-DNA fluorescence per nucleoid (relative units) in control (Control, top) and exon 4b siRNA-transfected (si4b, bottom) cells (n = 8) reveals a population with higher than normal fluorescence levels in exon 4b–silenced cells.
