Aneuploidy and mosaicism: a strategy for early adaptation todrug pressure in Leishmania

Unlike higher eukaryotes, Leishmania, a unicellular protozoan parasite, not only tolerates high levels of aneuploidy, but also exploits it for rapid adaptation to environmental changes, by altering gene copy number and consequently modulating the abundance of key proteins. In particular, aneuploidy constitutes the very first genomic modification during in vitro experimental selection of drug resistance. It is unclear how Leishmania cell populations may evolve so quickly towards drug resistance, but cell-to-cell variability might be the key. A unique phenomenon of mosaic aneuploidy, where individual cells in clonal population differ in their karyotype, is hypothesized to underlie the ability of the parasite to adapt rapidly to changing environment, such as drug pressure. In MAD-LEI we aim to verify this hypothesis. Using single cell genomics and high-resolution tracking of parasite lineages, we will characterize in vitro the dynamics of mosaic aneuploidy in presence/absence of two drugs currently used in clinical practice (Miltefosine and Paromomycin) and assess its importance in early adaptation to drug pressure. We will also for the first time describe the parasite’s population dynamics with(out) drug pressure throughout in vivo infection and characterize early genomic adaptations of the parasite to drugs. We anticipate a broad impact of MAD-LEI, both methodologically and conceptually, for Leishmania research and beyond.