CFU-E

CFU-E is a hematopoietic colony forming unit. It arises from CFU-GEMM (via BFU-E, which stands for "erythroid burst-forming units") and gives rise to proerythroblasts.

Understanding the murine CFU-e assay (analogous to human assay):

CFU-e is a stage of erythroid development between the BFU-e stage and the pro-erythroblast stage. CFU-e colony assay is designed to detect how many colony-forming-units of erythroid lineage there are in a hematopoietic tissue (bone marrow, spleen, or fetal liver), which may be reflective of the organism’s demand for oxygen delivery to the tissues or a hematopoietic disorder.

Early erythroid progenitors are found at a quite low frequency relative to later stages of erythroid differentiation, such as the pro-erythroblast and the basophilic erythroblast stages which can be detected by flowcytometry directly ex-vivo (Socolovsky et al. 2001 PMID 11719363). Furthermore, unlike for the pro-erythroblast and later stages of erythroid development, no truly reliable and unique positive flow-cytometric markers exist, though it is possible to use negative exclusion markers to deplete a cell population of other precursors and differentiated cells by cell sorting, thus greatly enriching it for the CFU-e activity (Prospective isolation and global gene expression analysis of the erythrocyte colony-forming unit, Terszowski G. et al. Blood 2005). CFU-e cells express Epo receptor, c-Kit (Stem cell factor receptor), transferrin receptor (CD71+), and are Ter119(glycophorin-A associated antigen)-negative. For the above reasons, the CFU-e assay, as inefficient and variable as it can often be, is still in use today.