The crosstalk between extrinsic niche-derived and intrinsic hematopoietic stem cell (HSC) factors controlling HSC maintenance remain elusive. Here we demonstrate that amphiregulin (AREG) from bone marrow (BM) leptin receptor (LepR+) niche cells is an important factor that mediates the crosstalk between BM niche and HSCs in stem cell maintenance. Mice deficient for the DNA repair gene Brca2 specifically in LepR+ cells (LepR-Cre;Brca2fl/fl) exhibit increased frequencies of total and …