Stem CellsThe BAF45a/PHF10 subunit of SWI/SNF-like chromatin remodeling complexes is essential for hematopoietic stem cell maintenance

- BAF45a and BAF45d specify hemopoietic PBAF and BAF complexes, whereas BAF45b and BAF45c are absent from hemopoietic tissue.
- BAF45a expression is enriched in long-term hemopoietic stem cells.
- BAF45a is essential for hemopoietic stem cell maintenance.
- BAF45a function in hemopoietic cells is cell autonomous.

The ability of hemopoietic stem cells to self-renew and differentiate into downstream lineages is dependent on specialized chromatin environments that establish and maintain stage-specific patterns of gene expression. However, the epigenetic factors responsible for mediating these regulatory events remain poorly defined. Here we provide evidence that BAF45a/PHF10, a subunit of SWI/SNF-like chromatin remodeling complexes, is essential for adult hemopoietic stem cell maintenance and myeloid lineage development. Deletion of BAF45a in the mouse is embryonic lethal. Acute deletion of BAF45a in the adult hemopoietic system causes a dose-dependent decrease in the frequency of long-term repopulating hemopoietic stem cells and committed myeloid progenitors without affecting their rate of proliferation. BAF45a-deficient hemopoietic stem cells and myeloid progenitors are selectively lost from mixed bone marrow chimeras, indicating their impaired function even in an intact microenvironment. Together, these studies suggest that the BAF45a subunit of SWI/SNF-like chromatin remodeling complexes plays nonredundant and specialized roles within the developing hemopoietic tissue.