mtDNA HVI length heteroplasmic profile in different tissues of maternally related members.

Sequencing of the homopolymeric tract of cytosines (C-stretch) in human mitochondrial HVI region usually results in a blurred pattern beyond it when a T/C transition at nt 16189 occurs: it depends on a length heteroplasmy probably arising through a replication slippage. This study aims to investigate the distribution of heteroplasmic length variants within three related individuals along maternal lineage by cloning approach. Sequencing of multiple independent clones (12--14) is sufficient to yield heteroplasmic profiles. In addition, we illustrate a direct correlation between expansion of heteroplasmy modal length and reduction of the number of adenines preceding the homopolymeric tract; this association may be useful in pedigree analysis and in forensic field for tissues comparison, single hair sample included.