Mannis van Oven on the Human Mitochondrial DNA Phylogeny

Fast Breaking Papers Commentary, June 2011

Mannis van Oven

Article: Updated Comprehensive Phylogenetic Tree of Global Human Mitochondrial DNA Variation

Authors: van Oven, M;Kayser, M
Journal: HUM MUTAT
Volume: 30, Issue: 2, Page: E386-E394, Year: FEB 2009
* Erasmus Univ, Med Ctr Rotterdam, Dept Forens Mol Biol, POB 2040, NL-3000 CA Rotterdam, Netherlands.
* Erasmus Univ, Med Ctr Rotterdam, Dept Forens Mol Biol, NL-3000 CA Rotterdam, Netherlands.

Mannis van Oven talks with and answers a few questions about this month's Fast Breaking Paper paper in the field of Molecular Biology & Genetics.

SW: Why do you think your paper is highly cited?

The paper presents a detailed phylogenetic tree of human mitochondrial DNA (mtDNA), available at the accompanying PhyloTree website. The tree includes branch-defining mutations, universal haplogroup nomenclature, as well as relevant references to the published literature. In addition, the tree is regularly updated and expanded to reflect the latest scientific advances. As such, it represents a convenient compendium for researchers in various fields, including evolutionary anthropology, forensics, medical genetics, and genealogy.

SW: Does it describe a new discovery, methodology, or synthesis of knowledge?

It is a synthesis of knowledge that also includes new discoveries in the form of novel branches (haplogroups) identified during the update process. We regularly screen the GenBank sequence database for newly released mtDNA sequences; when those sequences reveal novel haplogroups they are added to the next build of PhyloTree.

SW: Would you summarize the significance of your paper in layman's terms?

"...I would like to stress that one should be careful to rely on mtDNA alone as an indicator of a person's ancestry because mtDNA reflects only matrilineal ancestry and hence only a portion of our overall genetic makeup."

MtDNA is distinct from nuclear DNA in that it is haploid, free from recombination, and maternally inherited (we all received our mtDNA from our mother, she from her mother, and so on). Due to these properties mtDNA serves as an evolutionary marker of matrilineal descent. PhyloTree depicts the phylogenetic relationships between worldwide mtDNA types. So it is a global family tree of maternal lineages, starting with a single founder ("mitochondrial Eve") who lived about 200,000 years ago in Africa.

The shape of the tree, along with the geographic distribution of haplogroups, provides insights into the evolutionary and demographic history of human populations, e.g. how humans spread to other continents after a small group left Africa approximately 70,000 years ago. Having a detailed mtDNA tree available also means that any mtDNA analyzed today can be mapped to the tree to determine in which haplogroup it falls, giving the matrilineal ancestry of its carrier.

In genealogy, this can be used to check for matrilineal relatedness (female-line relatives share the same mtDNA type). In forensics, the tree can be used to select suitable polymorphisms for increased discrimination power between similar mtDNA types. In medical genetics, the tree can be used to assess the commonness and phylogenetic background of putative pathogenic mutations.

SW: How did you become involved in this research, and how would you describe the particular challenges, setbacks, and successes that you've encountered along the way?

I got interested in mtDNA when I started studying genetic diversity in human populations. I was looking for an overall mtDNA tree but realized that this information was incomplete and scattered over a high number of different publications. That is when I started to combine all available information into a single tree which eventually resulted in the PhyloTree project.

Particular challenges were cases where different papers presented conflicting topologies and haplogroup nomenclature. By re-evaluating the underlying sequence data I tried to come up with the most parsimonious solutions. It has been very encouraging to receive positive comments from PhyloTree users and I am indebted to many of them for valuable feedback.

SW: Where do you see your research leading in the future?

I hope to keep expanding PhyloTree. As more complete mtDNA sequences become available, especially from currently still underrepresented populations, the resolution of the tree will improve, leading to an increasingly finer view of human evolution. Perhaps the phylogenetic distribution of mutations will also contribute to the understanding of the mutation mechanism of mtDNA. More generally, I think the PhyloTree approach can serve as an example for the construction of detailed mtDNA phylogenies of other species.

SW: Do you foresee any social or political implications for your research?

Personal ancestry testing is becoming increasingly popular and hopefully this will lead to a wider appreciation of genetic diversity and how it preserves a legacy of our past. At the same time, I would like to stress that one should be careful to rely on mtDNA alone as an indicator of a person's ancestry because mtDNA reflects only matrilineal ancestry and hence only a portion of our overall genetic makeup.End

Mannis van Oven, M.Sc.
Department of Forensic Molecular Biology
Erasmus MC - University Medical Center Rotterdam
Rotterdam, The Netherlands



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