Development of myelofibrosis in the bone marrow of the GATA-1^low mice.

(A) Representative hematoxylin-eosin (left column) and Gomori silver (right column) staining of longitudinal sections of femurs from progressively older (1 to 18 months) GATA-1^low mice. Representative stainings of the corresponding sections from an 18-month-old wild-type mouse are also shown for comparison (bottom panels). (Original magnifications: left column, × 20 in all cases, except for the × 40 hematoxylin-eosin staining at 1 month of age as evidence of the massive presence of Mk shown by the arrows; right column, × 40). Similar results were observed in at least 4 mice per age group. In particular, 12 mice were analyzed from the 12- to 18-month-old age group. (B) Hematoxylin-eosin staining of representative transversal sections of femur diaphysis from 18-month-old wild-type (left) and GATA-1^low (right) mice (original magnification, × 5). Similar results were observed in at least 3 mice per experimental group. (C) Total number of mononuclear cells (TNC) in the femur of progressively older wild-type (white bars) and GATA-1^low (gray bars) mice. Mice were arbitrarily divided into the same age groups used in Tables 2 and 3. Results are presented as the mean (± SD) of 4 to 8 separate determinations per age group, for a total of 12 wild-type and 22 GATA-1^low mice analyzed. **P < .01 with respect to the values observed in the age-matched wild-type group. (D) Flow cytometry analysis of the expression of TER-119 and 4A5 in bone marrow cells harvested from wild-type (on the right) and GATA-1^low (on the left) animals at 1 month of age. Bone marrow from the GATA-1^lowanimals contains approximately 6- to 7-fold more 4A5 cells than the marrow from the wild-type animals.