BFU-E in the BM and spleen. BM (A-B) and spleen (C-D) of 2-day-old c-Kit^W/+ (□) and c-Kit^W/W (○) and adult c-Kit^W/+ (▪), EPO-tg (▴), and WEPO (•) mice were analyzed. Frequencies of BFU-Es per 10⁵ Ter119^neg/Low cells (enriched for progenitors) (A, C) and total numbers of BFU-Es per each organ are shown. Total BM cells correspond to the cells from 2 femura. Two-tailed P values were determined according to the Mann-Whitney U test. Brackets and corresponding P values are indicated for the compared groups. Horizontal black lines indicate mean colony numbers.