title: The specification of early hematopoiesis in the mammal.
abstract: OBJECTIVE
  A number of interesting surprises has emerged during the past year in the field of early hematopoietic development. This review highlights recent studies that have challenged the prevailing view of embryonic and fetal hematopoiesis in mammals, with a focus on the mouse as a model system. The authors apologize to the many colleagues whose work could not be cited because of space limitations.
  
  
  RESULTS
  Advances in our understanding of the embryonic origins of hematopoiesis in mammals and in the regulation of primitive and definitive hematopoietic development are discussed.
  
  
  CONCLUSIONS
  The ontological relation between primitive (embryonic) and definitive (fetal and adult) hematopoiesis still holds some mysteries for the biologist. Both technical and conceptual breakthroughs have refined our view of how blood cells form at different stages of development. What we learn from the embryo is not only of fundamental interest but may have future applications in the clinic.
authors.affiliation: Department of Medicine, Mount Sinai School of Medicine, New York, New York 10029, USA. margaret.baron@mssm.edu
authors.forename: Margaret H
authors.initials: MH
authors.lastname: Baron
authors.forename: Stuart T
authors.initials: ST
authors.lastname: Fraser
mesh_terms: D000818:Animals; D019070:Cell Lineage / Q000502:physiology; D004622:Embryo, Mammalian / Q000166:cytology / Q000502:physiology*; D015672:Erythroid Precursor Cells / Q000502:physiology; D004920:Erythropoiesis / Q000502:physiology; D006410:Hematopoiesis / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000502:physiology*; D051379:Mice; D015017:Yolk Sac / Q000166:cytology / Q000196:embryology