Extended Data Fig. 6: IRE1α-deficiency enriches a pro-leukemogenic transcription program exemplified by the Wnt/b-catenin pathway in HSPCs.

(a) Principal component analysis (PCA) of differentially expressed genes in LSK cells from non-Flt3^ITD/ITD and Flt3^ITD/ITD-expressing Ern1^wt and Ern1^ko mice (N = 3 mice per group). (b) White blood cell counts in experimental mice treated after 7-days of daily treatment with 100 mg/kg of the MAPK inhibitor CI-1040 (“MAPKi”) or vehicle. Data points represent individual mice (N = 5-8 mice/group; error bar, ± S.E.M); ns, not-significant, multiple Student’s t-test. (c) Average (± S.D.) expression of indicated genes relative to Actb. Each data point represents a mouse, N = 3 to 4 mice/group. (d and e) GSEA plot (d) and heatmap (e) of KEGG annotated Wnt/b-catenin signaling pathway genes in wildtype Flt3 (that is, Flt3^+/+) LSK cells. (f) Effect of XBP1 on an ER stress responsive promoter element (ERSE)-driven luciferase reporter in HEK293T cells. (g and h) Comparison of XBP1 (encoded by Xbp1s) and Xbp1u-encoded products (XBP1u and XBP1_(kkk), a more stable XBP1u protein) schematized in (g) on TOPFLASH reporter induced by a constitutively stable b-catenin^S33Y co-transfected into transfected into HEK293T cells. Data are average ( ± S.D.) relative luciferase units (RLU) of duplicate wells. (i) Average (± S.D.) of Ctnnb1 gene expression in BM c-Kit⁺ cells from two each of the indicated mice. (j) Dnajb9, Tet2 and Dnmt3a expression shown as average (± S.D., N = 3 mice/group) normalized to Actb in LSK cells from the indicated mice. Data in f and h are representative of three independent experiments. Statistics (c and j): *, P < 0.05; **, P < 0.01; ns, not-significant, unpaired, two-tailed Student’s t-test.

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