Lack of Ptn modulates repopulating behavior of HSCs. Changes in self-renewal and stem cell quality can be masked by alterations in proliferation. (A) Experimental design to address this issue, we sorted Lin⁻ Kit⁺ donor (Ly-5.1) cells from primary 129S2B6 (Ly-5.2) Ptn^+/+ or Ptn^−/− recipients (see Figure 2A) and transplanted equal numbers of LSK cells into second-degree WT recipients in a competitive manner (ie, together with 2 × 10⁵ recipient-type BM cells). (B) FACS plots from the pool of BM from Ptn^+/+ and Ptn^−/− primary recipients. (C) Level of engraftment, 16 weeks after transplantation of 1000 LSK cells from first-degree recipients. (D) Relative contribution of donor myeloid cells (non-T, non-B, Gr1⁺) and lymphoid cells (T plus B) to the total population in the second-degree recipient mice. (E) Relative numbers of LSK, MMP, and IL-7R⁺ CLPs (common lymphoid progenitors) within the donor Lin⁻ population of second-degree recipients, 16 weeks after transplantation.