Lineage promiscuity and plasticity in hematopoietic development.

Hematopoiesis has provided a valuable model for understanding how genetic programs are established to decide cell fates in multipotent stem or progenitor cells. The identification of common myeloid and lymphoid progenitors has allowed us to directly assess the regulatory mechanisms of lineage commitment. Multiple genes of hematopoietic lineages, including transcription factors, are coexpressed in hematopoietic stem cells and progenitors, a phenomenon referred to as "lineage priming." The accessibility for multiple transcription factors promiscuously allows flexibility in cell fate commitments at the multipotent stages. The changes in the expression levels and timing of transcription factors can induce lineage conversion of committed cells, indicating that the regulation of transcription factors might be primarily critical for maintaining hierarchical hematopoietic development.