Table 3.

mtDNA alterations in HD.

Alteration Type	Observed Change	Analysis Method	Patient Sample	References
mtDNA deletion	↓mtDNA/ nDNA relative copy number	real-time quantitative PCR	peripheral leukocytes	[161]
mtDNA deletion	mtDNA/ nDNA relative copy number (↑ in leukocytes and ↓ in dermal fibroblasts)	real-time quantitative PCR	leukocytes and dermal fibroblasts	[160]
mtDNA deletion	↓mtDNA (MT-ND2)	real-time PCR	brain and plasma	[158]
mtDNA deletion	↑mtDNA lesion frequency and ↓mtDNA abundance	quantitative PCR	brain tissue	[159]
mtDNA mutation	↑mtDNA heteroplasmies	sensitive mtDNA-targeted sequencing	lymphoblasts and longitudinal blood samples	[156]

Abbreviations: C9ALS/FTD, amyotrophic lateral sclerosis and frontotemporal dementia with C9ORF72 mutation; PCR, polymerase chain reaction; nDNA, nuclear DNA; MT-ND2, a gene encoding for NADH-ubiquinone oxidoreductase chain 2, which is a core subunit of complex I; mtDNA heteroplasmies (coexistence of mutated and wild-type mtDNA)