J:73737

Interval mapping was performed on phenotypically extreme animals from a (C57BL/6Ka-Thy1 x AKR/J)F2 intercross to identify QTLs associated with hematopoietic stem cell (HSC) regulation. Parental strain AKR/J exhibits a higher number of long-term reconstituting HSCs compared to parental strain C57BL/Ka-Thy1. A significant locus mapped to approximately 20 cM on mouse Chromosome 17 and is named Hscfr (hematopoietic stem cell frequency regulator). The QTL interval of Hscfr spans 9.8 cM to 33.8 cM, and the peakLOD score is 4.85 at D17Mit65 and D17Mit66. The AKR/J-derived allele is associated with increased HSC frequencies. When an AKR/J-derived region of Hscfr from D7Mit31 to D17Mit87 was bred onto a C57BL/6 background the phenotype was lost. Authors conclude that Hscfr alone is not sufficient to increase HSCs on a C57BL/6 background. Potential candidate genes for Hscfr are Notch3 and Notch4.