Base specific variation rates at mtDNA positions 16093 and 16183 in human hairs.

Small variations between haplotypes detected in different tissues from the same individual have been previously described. These differences complicate the interpretation of mtDNA results in real forensic casework. mtDNA haplotypes detected in hair strands collected at the crime scene have to be frequently compared with haplotypes of reference samples (buccal swabs) from victims or suspects. Nucleotide position 16093 is a well-known hot spot where differences can accumulate between different tissues of the same individual. Intra individual variation was also detected at positions 16182 and 16183 in haplotypes showing an uninterrupted HV1 poly-C stretch (with 16189C). In order to better characterize the type of variation in these positions between buccal cells and hair strands from the same individual, we have performed Sanger sequencing in 25-28 hair strands (411 in total) from 15 individuals showing either an uninterrupted HV1 polyC-stretch (16189C) or 16093C/Y in their buccal cells. The results have been evaluated by also taking into account our previous results published in [19]. We have found that no variation among hair strands was detected in individuals showing T16093 in buccal cells, while variation in hair strands (T16093, 16093C and 16093Y) were detected in individuals showing 16093C or 16093Y in buccal cells. Regarding nucleotide positions 16182 and 16183 in combination with an uninterrupted polyC-stretch, no variation was detected in hairs from individuals showing A16182 16183C in their buccal cells. In contrast, individuals A16182 A16183 showed hair strands with A16182 16183 M and A16182 16183C. And finally, individuals with 16182C 16183C showed some variation in a small amount of their hair strands (some hairs with 16182 M 16183C). These results can be relevant for forensic practitioners when comparing reference samples with hair strands, which is the type of sample most tested by using mtDNA analysis in forensic casework.

[1]  R. Cicarelli,et al.  No relationship found between point heteroplasmy in mitochondrial DNA control region and age range, sex and haplogroup in human hairs , 2011, Molecular Biology Reports.

[2]  M. Hirata,et al.  Heteroplasmy in Hair: Study of Mitochondrial DNA Third Hypervariable Region in Hair and Blood Samples *† , 2010, Journal of forensic sciences.

[3]  Jana Naue,et al.  Evidence for frequent and tissue-specific sequence heteroplasmy in human mitochondrial DNA. , 2015, Mitochondrion.

[4]  B Brinkmann,et al.  DNA commission of the international society for forensic genetics: guidelines for mitochondrial DNA typing. , 2000, Forensic science international.

[5]  M. Hirata,et al.  Heteroplasmy in hair: differences among hair and blood from the same individuals are still a matter of debate. , 2007, Forensic science international.

[6]  Tricia A. Thornton-Wells,et al.  Recurrent Tissue-Specific mtDNA Mutations Are Common in Humans , 2013, PLoS genetics.

[7]  J. A. DiZinno,et al.  A family exhibiting heteroplasmy in the human mitochondrial DNA control region reveals both somatic mosaicism and pronounced segregation of mitotypes , 1997, Human Genetics.

[8]  M. Holland,et al.  A sensitive denaturing gradient-Gel electrophoresis assay reveals a high frequency of heteroplasmy in hypervariable region 1 of the human mtDNA control region. , 2000, American journal of human genetics.

[9]  W R Mayr,et al.  DNA Commission of the International Society for Forensic Genetics: revised and extended guidelines for mitochondrial DNA typing. , 2014, Forensic science international. Genetics.

[10]  D. Turnbull,et al.  Reanalysis and revision of the Cambridge reference sequence for human mitochondrial DNA , 1999, Nature Genetics.

[11]  Arne Röhl,et al.  Evaluating length heteroplasmy in the human mitochondrial DNA control region , 2010, International Journal of Legal Medicine.

[12]  A. Di Rienzo,et al.  Tracing European founder lineages in the Near Eastern mtDNA pool. , 2000, American journal of human genetics.

[13]  W Parson,et al.  Results of a collaborative study of the EDNAP group regarding mitochondrial DNA heteroplasmy and segregation in hair shafts. , 2004, Forensic science international.

[14]  Katherine A. Roberts,et al.  Characterization of Mitochondrial DNA Sequence Heteroplasmy in Blood Tissue and Hair as a Function of Hair Morphology *,†,‡ , 2011, Journal of forensic sciences.

[15]  W. Parson,et al.  Hairy matters: MtDNA quantity and sequence variation along and among human head hairs. , 2016, Forensic science international. Genetics.

[16]  G. Tully,et al.  Mitochondrial DNA: Interpretation , 2009 .

[17]  A. Carracedo,et al.  DNA commission of the international society for forensic genetics: guidelines for mitochondrial DNA typing. , 2000, Forensic science international.

[18]  S. Lutz-Bonengel,et al.  Mitochondrial D-loop (CA)n repeat length heteroplasmy: frequency in a German population sample and inheritance studies in two pedigrees , 2007, International Journal of Legal Medicine.

[19]  T. Parsons,et al.  Investigation of Heteroplasmy in the Human Mitochondrial DNA Control Region: A Synthesis of Observations from More Than 5000 Global Population Samples , 2009, Journal of Molecular Evolution.

[20]  D. Dressman,et al.  Heteroplasmic mitochondrial DNA mutations in normal and tumor cells , 2010, Nature.

[21]  A. Salas,et al.  Results of the 1999-2000 collaborative exercise and proficiency testing program on mitochondrial DNA of the GEP-ISFG: an inter-laboratory study of the observed variability in the heteroplasmy level of hair from the same donor. , 2002, Forensic science international.

[22]  S. Lutz-Bonengel,et al.  Factors affecting the detection and quantification of mitochondrial point heteroplasmy using Sanger sequencing and SNaPshot minisequencing , 2011, International Journal of Legal Medicine.

[23]  Walther Parson,et al.  EMPOP--a forensic mtDNA database. , 2007, Forensic science international. Genetics.

[24]  H. Bandelt,et al.  Phylogeographic investigations: the role of trees in forensic genetics. , 2007, Forensic science international.

[25]  M. Stoneking,et al.  Extensive tissue-related and allele-related mtDNA heteroplasmy suggests positive selection for somatic mutations , 2015, Proceedings of the National Academy of Sciences.

[26]  David C. Samuels,et al.  Universal heteroplasmy of human mitochondrial DNA , 2012, Human molecular genetics.

[27]  Walther Parson,et al.  Concept for estimating mitochondrial DNA haplogroups using a maximum likelihood approach (EMMA) , 2013, Forensic science international. Genetics.

[28]  S. Woodward,et al.  Titanic's unknown child: the critical role of the mitochondrial DNA coding region in a re-identification effort. , 2011, Forensic science international. Genetics.

[29]  B Brinkmann,et al.  Considerations by the European DNA profiling (EDNAP) group on the working practices, nomenclature and interpretation of mitochondrial DNA profiles. , 2001, Forensic science international.

[30]  Terry Melton,et al.  Forensic mitochondrial DNA analysis of 691 casework hairs. , 2005, Journal of forensic sciences.

[31]  Manfred Kayser,et al.  Updated comprehensive phylogenetic tree of global human mitochondrial DNA variation , 2009, Human mutation.

[32]  B. Sykes,et al.  Variable levels of a heteroplasmic point mutation in individual hair roots. , 1997, American journal of human genetics.

[33]  Tissue-specific mitochondrial heteroplasmy at position 16,093 within the same individual , 2013, Current Genetics.

[34]  Mark R. Wilson,et al.  Forensics and mitochondrial DNA: applications, debates, and foundations. , 2003, Annual review of genomics and human genetics.

[35]  Á. Carracedo,et al.  Heteroplasmy in mtDNA and the weight of evidence in forensic mtDNA analysis: a case report , 2001, International Journal of Legal Medicine.

[36]  W. Parson,et al.  Mitochondrial DNA heteroplasmy or artefacts—a matter of the amplification strategy? , 2003, International Journal of Legal Medicine.

[37]  M. Holland,et al.  Mitochondrial DNA Sequence Analysis - Validation and Use for Forensic Casework. , 1999, Forensic science review.