Figure 5.

Heteroplasmy levels of somatic hybrids generated without selection for OXPHOS function. Three different cell lines were fused to each other as depicted in (A). One contained wild-type mtDNA and a neomycin-resistance nuclear marker (N), a second was homoplasmic for a mtDNA 7.5 kb deletion containing a zeocin-resistance nuclear marker (Z) and a third was homoplasmic for a pathogenic 4 bp deletion in cytochrome b gene containing a puromycin-resistance nuclear marker (P). Fusion products were grown in high glucose media containing two of the respective selection drugs (i.e. G418, zeocin or puromycin) and supplemented with uridine. Surviving clones were isolated and their DNA analyzed by Southern blot as described in Materials and Methods. (B) Analysis of the cytochrome b 4 bp deletion in hybrids of PN cell lines. A ³²P-labeled PCR amplicon, corresponding to the 5′ end of the apocytochrome b gene, was separated by electrophoresis on a 6% denaturing polyacrylamide gel and analyzed in a phosphoimager. (C) Phosphoimager signal from a Southern blot of DNA extracted from the hybrids between cells containing the 7.5 kb deletion and wt (NZ lines) or the 4 bp deletion in apocytochrome b (ZP lines).