title: Weird genotypes? Don't discard them, transmissible cancer could be an explanation.
abstract: Genetic chimerism is rarely considered in the analysis of population genetics data, because assumed to be an exceptionally rare, mostly benign, developmental accident. An unappreciated source of chimerism is transmissible cancer, when malignant cells have become independent parasites and can infect other individuals. Parasitic cancers were thought to be rare exceptions, only reported in dogs (Murgia et al.,Cell, 2006,126, 477; Rebbeck et al.,Evolution, 2009,63, 2340), Tasmanian devils (Pearse and Swift,Nature, 2006,439, 549; Pye et al.,Proceedings of the National Academy of Sciences, 2016,113, 374), and soft-shell clams (Metzger et al.,Cell, 2015,161, 255). However, the recent simultaneous report of four new contagious leukemias in marine mollusks (Metzger et al.,Nature, 2016,534, 705) might change the rules. By doubling up the number of naturally occurring transmissible cancers, this discovery suggests they may essentially be missed because not sufficiently searched for, especially outside mammals. We encourage population geneticists to keep in mind infectious cancer when interpreting weird genotypes in their molecular data. It would then contribute in the investigation of how widespread contagious cancer could really be in the wild. We provide an example with our own data inMytilusmussels, a commercially important shellfish. We identified genetic chimerism in a few mussels that suggests the possible occurrence at low prevalence in EuropeanM. edulispopulations of aM. trossuluscontagious cancer related to the one described by Metzger et al. (Nature, 2016,534, 705) in populations of British Columbia.
authors.affiliation: Université de Montpellier Sète France; Institut des Sciences de l'Evolution CNRS-UM-IRD Montpellier France.
authors.forename: Florentine
authors.initials: F
authors.lastname: Riquet
authors.affiliation: Université de Montpellier Sète France; Institut des Sciences de l'Evolution CNRS-UM-IRD Montpellier France.
authors.forename: Alexis
authors.initials: A
authors.lastname: Simon
authors.affiliation: Université de Montpellier Sète France; Institut des Sciences de l'Evolution CNRS-UM-IRD Montpellier France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bierne
keywords: Mytilus; heteroplasmy; infectious cancer