PKR regulates clonogenic potential of BM progenitors both in vitro and in vivo. (A) Representative colonies after culture of WT, TgPKR, TgDNPKR, or PKRKO BM cells from 3- to 5-month-old mice in methylcellulose for 7 days. (B-F) Unfractionated BM cells (2 × 10⁴ for B, C, D, and E, 10⁵ for F) from WT, TgPKR, TgDNPKR, or PKRKO mice were plated and resulting CFU-GEMM (B), CFU-GM (C), CFU-G (D), CFU-M (E), and BFU-E (F) counted. BM from 5 mice of each genotype was assayed and mean ± SEM graphed. (G) Representative examples of macroscopic spleen colonies (CFU-S) from WT irradiated recipients injected with 2 × 10⁴ unfractionated BM cells either from WT, TgPKR, TgDNPKR, or PKRKO mice as indicated. (H) Colonies were counted 10 days after transplantation. Graphs represent mean ± SEM (n = 4 donor mice of each genotype).