[Somatic mosaicism of expanded CAG trinucleotide repeat in the neural and nonneural tissues of Machado-Joseph disease (MJD)].

The tissue-specific pattern of somatic mosaicism in Machado-Joseph disease (MJD) was reviewed. In the MJD central nervous system (CNS) tissues, the pattern of CAG repeat mosaicism in the mutant allele was similar among various portions except cerebellar cortex which had slightly smaller CAG repeat tracts. Among nonneural tissues, the muscle exhibited a lesser degree of CAG instability, while the liver, kidney and colon displayed a greater diversity of extra bands and more extended major band compared to CNS. Thus, mitotic turnover may contribute largely to the tissue-specific pattern of mosaicism in MJD, but other unknown cell specific factors should be taken into consideration for the understanding the mechanism of somatic mosaicism in CAG repeat diseases.