Figure 4.

The clinical, histochemical and mtDNA abnormalities associated with mitochondrial PEO. (A) Typical clinical features of a patient with mitochondrial CPEO, extraocular motility in cardinal directions of gaze is severely reduced with relative preservation of downgaze as the patient is asked to look down (i), up (ii), right (iii) and left (iv). (B) Sequential COX-SDH histochemistry showing the presence of scattered COX-deficient fibres in a quadriceps muscle biopsy. (C) Southern blotting of muscle DNA indicates the patterns observed in a control (lane 1), a patient with a heteroplasmic, single large-scale mtDNA deletion (lane 2) and multiple mtDNA deletions (lanes 3 and 4). (D) Long-range PCR is also widely used to identify multiple mtDNA deletions (lane 3) which are amplified in addition to full-length, wild type mtDNA. Also shown is a control (lane 2) and DNA size markers (lane 1).