Multiorgan failure with abnormal receptor metabolism in mice mimicking Samd9/9L syndromes
Akiko Nagamachi, … , Hirotaka Matsui, Toshiya Inaba
Akiko Nagamachi, … , Hirotaka Matsui, Toshiya Inaba
Published December 29, 2020
Citation Information: J Clin Invest. 2021;131(4):e140147. https://doi.org/10.1172/JCI140147.
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Research Article Cell biology Hematology

Multiorgan failure with abnormal receptor metabolism in mice mimicking Samd9/9L syndromes

Abstract

Autosomal dominant sterile α motif domain containing 9 (Samd9) and Samd9L (Samd9/9L) syndromes are a large subgroup of currently established inherited bone marrow failure syndromes that includes myelodysplasia, infection, growth restriction, adrenal hypoplasia, genital phenotypes, and enteropathy (MIRAGE), ataxia pancytopenia, and familial monosomy 7 syndromes. Samd9/9L genes are located in tandem on chromosome 7 and have been known to be the genes responsible for myeloid malignancies associated with monosomy 7. Additionally, as IFN-inducible genes, Samd9/9L are crucial for protection against viruses. Samd9/9L syndromes are caused by gain-of-function mutations and develop into infantile myelodysplastic syndromes associated with monosomy 7 (MDS/–7) at extraordinarily high frequencies. We generated mice expressing Samd9LD764N, which mimic MIRAGE syndrome, presenting with growth retardation, a short life, bone marrow failure, and multiorgan degeneration. In hematopoietic cells, Samd9LD764N downregulates the endocytosis of transferrin and c-Kit, resulting in a rare cause of anemia and a low bone marrow reconstitutive potential that ultimately causes MDS/–7. In contrast, in nonhematopoietic cells we tested, Samd9LD764N upregulated the endocytosis of EGFR by Ship2 phosphatase translocation to the cytomembrane and activated lysosomes, resulting in the reduced expression of surface receptors and signaling. Thus, Samd9/9L is a downstream regulator of IFN that controls receptor metabolism, with constitutive activation leading to multiorgan dysfunction.

Authors

Akiko Nagamachi, Akinori Kanai, Megumi Nakamura, Hiroshi Okuda, Akihiko Yokoyama, Satoru Shinriki, Hirotaka Matsui, Toshiya Inaba

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Figure 7

Samd9LD764N translocates Ship2 and activates lysosomes under the control of IFN.

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Samd9LD764N translocates Ship2 and activates lysosomes under the control...
(A and B) LFs cultured in serum/cytokine-free medium (left panels) or medium containing IFN-γ (1 ng/mL) were stained with Lamp1 and EGFR antibodies (A). Quantification of areas of Lamp1 signals (red) greater than EGFR (green) using the method described in the legend of Supplemental Figure 3 (B). (C) Immunoblot detection of LF extracts using antibodies indicated at left. Representative data of 2 experiments. (D and E) 293 cells were transiently transfected with a pCMV3 expression vector containing cDNA of Samd9L as indicated. Cells were stained with a Lamp1 antibody (D). Number of pixels positive for red signals determined by ImageJ software divided by the number of nuclei are shown (E). (F) IHC-p with hematoxylin counterstaining (upper) and IHC-f (lower) of 6-week-old mouse kidney using antibodies listed at left. The overlap of EGFR and Lamp1 signals is shown by an arrow. (G) LF+/+ or LFm/m were cultured with IFN-γ at the concentrations indicated above for 48 hours. Extracts were subjected to immunoblot analysis using antibodies indicated at left. Relative expression ratios of Samd9L to β-actin are indicated between the 2 panels. Representative data of 3 independent experiments. (H) LFs were cultured with IFN-γ (1 and 5 ng/mL) for 48 hours. Representative FCM histogram (of 3 independent experiments) of surface EGFR expression. Nuclei were stained with DAPI. Scale bars: 50 μm.