Adult murine hematopoiesis can proceed without β1 and β7 integrins

The function of α4β1 and α4β7 integrins in hematopoiesis is controversial. While some experimental evidence suggests a crucial role for these integrins in retention and expansion of progenitor cells and lymphopoiesis, others report a less important role in hematopoiesis. Using mice with a deletion of the β1 and the β7 integrin genes restricted to the hematopoietic system we show here that α4β1 and α4β7 integrins are not essential for differentiation of lymphocytes or myelocytes. However, β1β7 mutant mice displayed a transient increase of colony-forming unit (CFU-C) progenitors in the bone marrow and, after phenylhydrazine-induced anemia, a decreased number of splenic erythroid colony-forming units in culture (CFUe's). Array gene expression analysis of CD4+CD8+ double-positive (DP) and CD4-CD8 - double-negative (DN) thymocytes and CD19+ and CD4 + splenocytes did not provide any evidence for a compensatory mechanism explaining the mild phenotype. These data show that α4β1 and α4β7 are not required for blood cell differentiation, although in their absence alterations in numbers and distribution of progenitor cells were observed. © 2006 by The American Society of Hematology.