[Chromosomal structural variation -- an approach for multiple system atrophy].

The human genome contains unstable regions that account for 10％ of the entire genome and are eccentrically located around centromeres and telomeres. They consist of several kb or Mb of genome sequence, and present a variety of alterations that occur during the replication process, such as repetitions, duplications, deletions, and insertions. These structural polymorphisms are called copy number variations (CNV). The mutation rate of CNV is 10(2)-10(4) times higher than that of single-nucleotide polymorphisms (SNP), and has attracted attention as a basis for sporadic disease. The relationship between CNV and clinical conditions is complicated. While models based on duplication or deletion can be explained as resulting from genetic effect or haploinsufficiency, CNV result in a greater range of transcription anomalies, in addition to that of a gene coded in the region. Recent studies have revealed the mechanisms of transcription and splicing through snRNA and miRNA in the CNV regions. Recently, we experienced discordant monozygotic twin (DMZT) cases in which the patients developed unilateral multiple system atrophy (MSA). Here, we introduced the recent progress regarding CNV and neurodegenerative diseases as it concerns the above DMZT cases and other sporadic MSA cases.