FIG 4.

SRSF2 is indispensable for survival of adult BM cells. (A to D) Poly(IC) injection into adult Mx1-Cre⁺ or Mx1-Cre⁻ Srsf2 cKO mice. Poly(IC) was injected i.p. every other day for three injections in total into cKO mice (600 μg/dose). The day of the first injection was defined as day 0. Mx1-Cre⁻ Srsf2^flox/+, n = 11. Mx1-Cre⁻ Srsf2^flox/flox, n = 23. Mx1-Cre⁺ Srsf2^flox/+, n = 9. Mx1-Cre⁺ Srsf2^flox/flox, n = 24. (A) Genotyping of PB and BM cells on day16. Mx1-Cre⁺ Srsf2^flox/+ samples showed almost complete excision of the flox allele, while Mx1-Cre⁺ Srsf2^flox/flox samples showed incomplete excision. (B) Platelet (Plt) count on day 16. (C) Total BM cells from femurs and tibias of both legs counted using trypan blue. (D) Absolute number of LSK cells in total BM measured by flow cytometry. (E) Percent LSK in total BM measured by flow cytometry. (F) Competitive BMT of Mx1-Cre cKO cells. One million test cells (CD45.2) were mixed with the same number of competitor cells (CD45.1) and transplanted. Chimerism in PB was evaluated by flow cytometry before (week 0) and after poly(IC) injection. Five mice were in each group. Mx1-Cre⁺ Srsf2^flox/flox cells had lower engraftment efficiency than others and showed a continuous decrease in the level of donor chimerism after poly(IC) injection. *, P < 0.05; **, P < 0.005.