Figure 5. Cholesterol Accumulation Couples ABCA1 Invalidation and Tet2 Deficiency to IL-3 Receptor β Signaling Hypersensitivity.

(A-D) Quantification of BODIPY staining by flow cytometry expressed as mean fluorescence intensity (MFI) as a surrogate of cellular cholesterol neutral lipid per cell (A-D) in BM hematopoietic stem (A and C) and progenitor (B and D) cells (i.e., LSKs, MEPs, CMPs, and GMPs) of recipient mice transplanted with Mx1-Cre⁺, Mx1-Cre⁺Abca1^fl/fl, Mx1-Cre⁺Tet2^fl/fl,and Mx1-Cre⁺Tet2^fl/,lAbca1^fl/fl BM (A and B) or control and Mx1-Cre⁺Tet2^fl/fl BM expressing empty, ABCA1-WT, or ABCA1 mutants (C and D). Results are means ± SEMs of 5–9 animals per group.

(E) mRNA expression of SREBP-2 and cholesterol biosynthesis target genes (Hmgcr, Mvk, Idi1, Sc4mol, and Dhcr24) from empty, WT, and ABCA1 mutant-transduced BM on a Tet2-deficient background isolated at the end of the study period. The expression of mRNA was normalized to m36B4. mRNA levels were expressed as percentage over WT whole BM cells.

(F) Proliferation rates were determined after 2 h [³H]-thymidine pulse labeling in BM cells from empty, ABCA1-WT, and ABCA1 mutant-transduced animals on a Tet2-deficient background that were grown for 72 h in liquid culture in the presence or absence of 6 ng/mL IL-3 and 2 ng/mL GM-CSF and the indicated chemical compounds. Results are means ± SEMs of cultures from at least 3 independent mice.

*p < 0.05 versus empty control-transduced animals on a Tet2-deficient background. §p < 0.05 versus ABCA1-WT. #p < 0.05 and ##p < 0.001 versus Mx1-Cre⁺ controls.