National Heart, Lung, and Blood Institute (NHLBI) 3 articles published in JoVE Genetics Identification of Homologous Recombination Events in Mouse Embryonic Stem Cells Using Southern Blotting and Polymerase Chain Reaction Dan Zhou*1,2, Lei Tan*1, Jian Li*3, Tanbin Liu1, Yi Hu1, Yalan Li1, Sachiyo Kawamoto4, Chengyu Liu5, Shiyin Guo3, Aibing Wang1 1Lab of Animal Models and Functional Genomics (LAMFG), The Key Laboratory of Animal Vaccine & Protein Engineering, College of Veterinary Medicine, Hunan Agricultural University (HUNAU), 2Department of Pathology, Georgetown University Medical School, 3College of Food Science and Technology, Hunan Agricultural University (HUNAU), 4Lab of Molecular Cardiology (LMC), National Heart, Lung, and Blood Institute (NHLBI)/National Institutes of Health (NIH), 5Transgenic Core, National Heart, Lung, and Blood Institute (NHLBI)/National Institutes of Health (NIH) Here, we present a detailed protocol for identifying homologous recombination events that occurred in mouse embryonic stem cells using Southern blotting and/or PCR. This method is exemplified by the generation of nonmuscle myosin II genetic replacement mouse models using traditional embryonic stem cell-based homologous recombination-mediated targeting technology. Behavior The Treadmill Fatigue Test: A Simple, High-throughput Assay of Fatigue-like Behavior for the Mouse John P. Dougherty1, Danielle A. Springer2, Marvin C. Gershengorn1 1Laboratory of Endocrinology and Receptor Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 2Murine Phenotyping Core, National Heart, Lung, and Blood Institute, National Institutes of Health Fatigue is a common, undertreated and frequently poorly-understood symptom in many diseases and disorders. New preclinical assays of fatigue may help to improve current understanding and future treatment of fatigue. To that end, the current protocol provides a novel means of measuring fatigue-like behavior in the mouse. Biology In vivo Clonal Tracking of Hematopoietic Stem and Progenitor Cells Marked by Five Fluorescent Proteins using Confocal and Multiphoton Microscopy Daniela Malide1, Jean-Yves Métais2, Cynthia E. Dunbar2 1Light Microscopy Core Facility, NHLBI/NIH, 2Hematology Branch, NHLBI/NIH Combinatorial 5 fluorescent proteins marking of hematopoietic stem and progenitor cells allows in vivo clonal tracking via confocal and two-photon microscopy, providing insights into bone marrow hematopoietic architecture during regeneration. This method allows non-invasive fate mapping of spectrally-coded HSPCs-derived cells in intact tissues for extensive periods of time following transplantation.