Developmental maturation of hematopoietic progenitors from wt and Hhex^−/− ES cells. Hhex^−/− hematopoietic cells retain the phenotype of the earliest definitive hematopoietic progenitors throughout the coculture. (A) Number of CD41⁺ cells found in wt Jet and Hhex^−/− on days 6 to 9 of coculture (n = 5). Day 9 is significant (P < .005, 2-tailed t test). (B) Number of CD41⁺c-kit⁺ cells from wt and Hhex^−/− cocultures, as determined by flow cytometry. (C) Number of CD45⁺ cells found in wt Jet and Hhex^−/− on days 6 to 9 of coculture. The number or CD45⁺ cells is significantly reduced in the Hhex^−/− cocultures on days 6 to 8 of coculture (2-tailed t test). (D) Number of CD45⁺c-kit⁺ cells from wt and Hhex^−/− cocultures, as determined by flow cytometry. Days 6 and 7 are significant (2-tailed t test). Error bars represent SD.