Fig. 1

Bone marrow neuropathy is a hallmark of disease in mouse models of both myeloid and lymphoid malignancies, and it involves severe ultrastructural damage to myelin and axons in pre-leukemic NRAS-G12D⁺ primary mutant mice and acute myeloid leukemia (AML) patients. C57BL/6J female mice transplanted with bone marrow (BM) nucleated cells obtained from polyinosine-polycytosine (pI-pC)-induced control (NRAS^G12D) or NRAS-G12D⁺ (Mx1-Cre NRAS^G12D) mice, and analyzed at 40 weeks of age, 32 weeks after the transplant (n = 3–4 per group). (A) Representative immunostaining of tyrosine hydroxylase (TH, red) to visualize sympathetic fibres in BM; nuclei were counterstained with DAPI (blue); scale bar, 100 µm. (B) Quantification of TH⁺ sympathetic fibres in BM diaphysis (%). (C-F) Time-course analysis of TH⁺ sympathetic fibres and of glial fibrillary acidic protein (GFAP)⁺ ensheathing Schwann cells in BM diaphysis from control (NRAS^G12D) or NRAS-G12D⁺ (Mx1-Cre NRAS^G12D) primary mutant female mice, induced with pI-pC at 7–27 weeks of age. (C) Quantification of TH⁺ sympathetic fibres and of GFAP⁺ ensheathing Schwann cells in BM diaphysis (%), 6 weeks after pI-pC induction (n = 5–6 per group). (D) Quantification of TH⁺ sympathetic fibres and of GFAP⁺ ensheathing Schwann cells in BM diaphysis (%), 24 weeks after pI-pC induction (n = 3–5 per group). (E) Representative immunostaining of TH (red, upper panel) to visualize sympathetic fibres and of GFAP (red, lower panel) to visualize ensheathing Schwann cells in BM; nuclei were counterstained with DAPI (blue); scale bar, 500 µm. Magnification is shown for better appreciation of TH⁺ sympathetic fibres, and (F) Quantification in BM diaphysis (%), 38 weeks after pI-pC induction (n = 5–7 per group). (G-H) Wild-type (p53^+/+) or p53^−/− female and male mice, analyzed at 12 weeks of age (n = 6–9 per group). (G) Representative immunostaining of TH (red, upper panel) to visualize sympathetic fibres in BM; nuclei were counterstained with DAPI (blue); scale bar, 250 µm. (H) Quantification in BM diaphysis (%). *p < 0.05, **p < 0.01, ***p < 0.001 unpaired two-tailed t test. (I) Representative transmission electron microscopy (TEM) images of GFAP⁺ BM sections from control (NRAS^G12D) or NRAS-G12D⁺ (Mx1-Cre NRAS^G12D) male mice, analyzed at 29 weeks of age, 20 weeks after pI-pC induction (n = 2–3 per group). (J) Representative TEM images of GFAP⁺ BM sections from AML patients (n = 4, P1-P4). a, Schwann cell nucleus; o, myelin sheath; *, axon; △, collagen fibres; x, tubule-vesicular elements. Scale bar indicated in the images.