The total number of cells in the spleen from Gata1^low mice is positively correlated with the hematocrit, and the frequency of MK in the spleen is correlated with the fibrosis in the spleen. Each dot represents an individual mutant mouse. For the purpose of this analysis, results obtained in heterozygous or hemizygous mice of different backgrounds were pooled together. The best-fitting linear regression and the corresponding significance value are indicated.