University of Washington School of Medicine 1 article published in JoVE Developmental Biology Clonal Analysis of Embryonic Hematopoietic Stem Cell Precursors Using Single Cell Index Sorting Combined with Endothelial Cell Niche Co-culture Brandon K. Hadland1,2, Barbara Varnum-Finney1, Cynthia Nourigat-Mckay1, David Flowers1, Irwin D. Bernstein1,2 1Clinical Research Division, Fred Hutchinson Cancer Research Center, 2Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Washington School of Medicine Here we present methodology for the clonal analysis of hematopoietic stem cell precursors during murine embryonic development. We combine index sorting of single cells from the embryonic aorta-gonad-mesonephros region with endothelial cell co-culture and transplantation to characterize the phenotypic properties and engraftment potential of single hematopoietic precursors.