Rare copy number variations by the nonrecurrent rearrangements involving PMP22 have been recently suggested to be associated with CMT1A peripheral neuropathy. As a mechanism of the nonrecurrent rearrangement, replication-based fork stalling template switching (FoSTeS) by microhomology-mediated break-induced replication (MMBIR) has been proposed. We found three Korean CMT1A families with putative nonrecurrent duplication. The duplications were identified by microsatellite typing and applying a CGH microarray. The breakpoint sequences in two families suggested an Alu-Alu-mediated rearrangement with the FoSTeS by the MMBIR, and a two-step rearrangement of the replication-based FoSTeS/MMBIR and meiosis-based recombination. The two-step mechanism has still not been reported. Segregation analysis of 17p12 microsatellite markers and breakpoint junction analysis suggested that the nonrecurrent rearrangements are stably inherited without alteration of junction sequence; however, they may allow some alteration of the genomic contents in duplication across generations by recombination event. It might be the first study on the pedigree analysis of the large CMT1A families with nonrecurrent rearrangements. It seems that the exact mechanism of the nonrecurrent rearrangements in the CMT1A may have a far more complex process than has been expected.

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Mitochondrial diseases are clinically and genetically heterogeneous disorders, which make the exact diagnosis and classification difficult. The purpose of this study was to identify pathogenic mtDNA mutations in 61 Korean unrelated families (or isolated patients) with MELAS or MERRF. In particular, the mtDNA sequences were completely determined for 49 patients. From the mutational analysis of mtDNA obtained from blood, 5 confirmed pathogenic mutations were identified in 17 families, and 4 unreported pathogenically suspected mutations were identified in 4 families. The m.3243A＞G in the tRNA Leu(UUR) was predominantly observed in 10 MELAS families, and followed by m.8344A＞G in the tRNA Lys of 4 MERRF families. Most pathogenic mutations showed heteroplasmy, and the rates were considerably different within the familial members. Patients with a higher rate of mutations showed a tendency of having more severe clinical phenotypes, but not in all cases. This study will be helpful for the molecular diagnosis of mitochondrial diseases, as well as establishment of mtDNA database in Koreans.

We identified a potential molecular marker associated with meat quality traits in the myosin heavy chain 4, MYH4 gene of Landrace pigs. Sequencing revealed a single nucleotide polymorphism (SNP; g.‐1398G>T) in the 5' upstream region of MYH4. It was significantly associated with the number of type IIa muscle fibers and water‐holding capacity based on filter‐paper fluid uptake. The GG genotype groups had a greater number of type IIa fibers and a larger area composed of type IIa fibers than the other genotype group (P = 0.004 and P = 0.061, respectively). Expression level of MYH4 gene in the genotype TT or GT was higher than in genotype of GG (P < 0.0001). The T allele may enhance expression level of MYH4 gene and then the portion of IIb type fiber in the muscle be increased by the T allelle. Therefore, we suggest that the g.‐1398G>T in the 5' upstream region of the porcine MYH4 may be used as a molecular marker for meat quality traits, although its functional effect is not defined yet.