[Detection of deletions in platelet mitochondrial DNA in Kearns-Sayre syndrome using polymerase chain reaction].

Kearns-Sayre syndrome has been genetically diagnosed by detecting deleted mitochondrial DNA in muscle biopsy specimen using the Southern blot method. However, deleted mitochondrial DNA cannot be detected in the blood by this method. With the limited availability of muscle biopsy specimens in mind, we attempted to establish a noninvasive genetic diagnostic method for this syndrome. The polymerase chain reaction (PCR) was employed for detecting mitochondrial DNA deletions in platelets at levels below the sensitivity of Southern blotting. We selected several pairs of oligonucleotide primers, considering the regions of predilection for deletion in this syndrome, and identified mitochondrial DNA deletions in platelets in three of four patients. The size and the locations of the deletions were determined by the nesting primer PCR method, in which the primary PCR products derived from deleted mitochondrial DNAs were subjected for reamplification using a series of nesting primers. By this method, it was possible to determine whether the products retained a complementary site for each primer. Patient 1 had an 8.3-kb deletion starting within the CO1 gene and ending within the Cyt b gene. Patient 2 had a 7.2-kb deletion starting within the CO1 gene and ending within the ND5 gene. Patient 3 had a 4.7-kb deletion starting within the ATPase6 or the CO3 gene and ending within the ND5 gene. Deletions were detected neither in Patient 4 nor in three mothers of four patients. These results indicate that the present method is useful for noninvasive genetic diagnosis of Kearns-Sayre syndrome.