RT Journal Article SR Electronic T1 Genetic mapping of species differences via “in vitro crosses” in mouse embryonic stem cells JF bioRxiv FD Cold Spring Harbor Laboratory SP 148486 DO 10.1101/148486 A1 Stefano Lazzarano A1 Marek Kučka A1 João P. L. Castro A1 Ronald Naumann A1 Paloma Medina A1 Michael N. C. Fletcher A1 Rebecka Wombacher A1 Joost Gribnau A1 Tino Hochepied A1 Claude Libert A1 Yingguang Frank Chan YR 2017 UL http://biorxiv.org/content/early/2017/06/10/148486.abstract AB Discovering the genetic changes underlying species differences is a central goal in evolutionary genetics. However, hybrid crosses between species in mammals often suffer from hybrid sterility, greatly complicating genetic dissection of trait variation. Here we describe a simple, robust and transgene-free technique to make “in vitro crosses” in hybrid mouse embryonic stem cells by inducing random mitotic crossovers with the drug ML216, which inhibits Bloom syndrome (BLM). Starting with an interspecific hybrid (between Mus musculus and Mus spretus) embryonic stem cell line spanning 1.5 million years of divergence, we demonstrate the feasibility of mapping enzymatic differences across species within weeks and the possibility of re-deriving whole mice. Our work shows how in vitro crosses can overcome major bottlenecks like hybrid sterility in traditional mouse breeding to address fundamental questions in evolutionary biology.Impact Statement By mixing hybrid mouse genomes in stem cells via mitotic recombination, genetic mapping and hybrid mosaic mice can be achieved in weeks, even across species barriers.