Certain concepts concerning EPO/EPOR action modes have been challenged by in vivo studies : Bcl-x levels are elevated in maturing erythroblasts , but not in their progenitors ; truncated EPOR alleles that lack a major p85/PI3K recruitment site nonetheless promote polycythemia ; and Erk1 disruption unexpectedly bolsters erythropoiesis .
O O O I-GeneOrGeneProduct O O O O O O O O O O B-GeneOrGeneProduct O O O O O O O O O O O O O O B-GeneOrGeneProduct O O O O O B-GeneOrGeneProduct O O O O B-DiseaseOrPhenotypicFeature O O B-GeneOrGeneProduct O O O O O