We created cellular models of DBA using murine embryonic stem (ES) cells harboring gene trap mutations [24], [25] in Rps19 or Rpl5. Murine ES cells, which have not been previously used as a disease model in DBA, are a powerful tool for the study of hematopoiesis and development in other tissues [26], [27]. The gene discussed is RPL5; the disease is Diamond-Blackfan anemia.