Adult murine hernatopoiesis can proceed without β1 and β7 integrins

The function of alpha 4 beta 1 and alpha 4 beta 7 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 beta 1 and the beta 7 integrin genes restricted to the hematopoietic system we show here that alpha 4 beta 1 and alpha 4 beta 7 integrins are not essential for differentiation of lymphocytes or myelocytes. However, beta 1 beta 7 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 alpha 4 beta 1 and alpha 4 beta 7 are not required for blood cell differentiation, although in their absence alterations in numbers and distribution of progenitor cells were observed.