Complement and inflammasome overactivation mediates paroxysmal nocturnal hemoglobinuria with autoinflammation
Britta Höchsmann, … , Peter M. Krawitz, Taroh Kinoshita
Britta Höchsmann, … , Peter M. Krawitz, Taroh Kinoshita
Published December 2, 2019; First published August 20, 2019
Citation Information: J Clin Invest. 2019;129(12):5123-5136. https://doi.org/10.1172/JCI123501.
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Research Article Hematology Inflammation

Complement and inflammasome overactivation mediates paroxysmal nocturnal hemoglobinuria with autoinflammation

Abstract

Patients with paroxysmal nocturnal hemoglobinuria (PNH) have a clonal population of blood cells deficient in glycosylphosphatidylinositol-anchored (GPI-anchored) proteins, resulting from a mutation in the X-linked gene PIGA. Here we report on a set of patients in whom PNH results instead from biallelic mutation of PIGT on chromosome 20. These PIGT-PNH patients have clinically typical PNH, but they have in addition prominent autoinflammatory features, including recurrent attacks of aseptic meningitis. In all these patients we find a germ-line point mutation in one PIGT allele, whereas the other PIGT allele is removed by somatic deletion of a 20q region comprising maternally imprinted genes implicated in myeloproliferative syndromes. Unlike in PIGA-PNH cells, GPI is synthesized in PIGT-PNH cells and, since its attachment to proteins is blocked, free GPI is expressed on the cell surface. From studies of patients’ leukocytes and of PIGT-KO THP-1 cells we show that, through increased IL-1β secretion, activation of the lectin pathway of complement and generation of C5b-9 complexes, free GPI is the agent of autoinflammation. Eculizumab treatment abrogates not only intravascular hemolysis, but also autoinflammation. Thus, PIGT-PNH differs from PIGA-PNH both in the mechanism of clonal expansion and in clinical manifestations.

Authors

Britta Höchsmann, Yoshiko Murakami, Makiko Osato, Alexej Knaus, Michi Kawamoto, Norimitsu Inoue, Tetsuya Hirata, Shogo Murata, Markus Anliker, Thomas Eggermann, Marten Jäger, Ricarda Floettmann, Alexander Höllein, Sho Murase, Yasutaka Ueda, Jun-ichi Nishimura, Yuzuru Kanakura, Nobuo Kohara, Hubert Schrezenmeier, Peter M. Krawitz, Taroh Kinoshita

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Figure 2

Genetic abnormalities in patients with PIGT-PNH.

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Genetic abnormalities in patients with PIGT-PNH. (A) PIGT mutations in G...
(A) PIGT mutations in GPI-AP–positive (GPI +) and –defective (GPI –) cells from patients with PIGT-PNH. (Top) GPI + cells from patients J1, G1, G2, and G3 had a germline PIGT mutation (triangle) in the maternal (M) allele. Two maternally imprinted genes, L3MBTL1 and SGK2, within myeloid common deleted region (CDR) are expressed from the paternal (P) allele. Solid and broken red double arrows, P and M alleles of myeloid CDR, respectively. (Bottom) GPI blood cells from PIGT-PNH patients had an 8 Mb to 18 Mb deletion spanning myeloid CDR and PIGT and/or PIGU in the P chromosome 20q leading to losses of expression of L3MBTL1 and SGK2 genes (dotted boxes). (B) A 1.9-Mb region in chromosome 20q spanning PTPRT gene to OSER1 gene is termed myeloid common deleted region. PIGT and PIGU genes are approximately 1.2 Mb telomeric and 7.4 Mb centromeric to the myeloid CDR, respectively. L3MBTL1 and SGK2 genes marked # are maternally imprinted. (C) qRT-PCR analysis of genes within myeloid CDR in GPI-AP–defective granulocytes from J1 and granulocytes from a healthy control (top) and whole blood cells from G1 and a healthy control (bottom). L3MBTL1 and SGK2, maternally imprinted genes; IFT52 and MYBL2, nonimprinted genes. Relative expression is determined taking means of ABL levels as 1 (J1) or of GAPDH as 1 (G1). Blue bars, cells from J1 and G1; orange bars, cells from healthy individuals; * indicates below detection limits. Mean of duplicate (JI) and triplicate (G1) samples in 1 of the 2 independent experiments. Mean RQ max values for J1 samples were 0.15 (IFT52) and 0.17 (MYBL2), and for normal control samples were 0.034 (L3MBLT), 0.003 (SGK2), 0.078 (IFT52), and 0.002 (MYBL2). Mean RQ max values for G1 samples were 0.01 (SGK2), 0.004 (L3MBTL), and 0.01 (GAPDH), and for normal control samples were 0.08 (SGK2), 0.22 (L3MBTL), and 0.002 (GAPDH). (D) Methylation status of the CpG islands in L3MBTL1 in G1, G2, and G3. Red, methylated CpG islands; pink, unmethylated CpG islands; gray, unknown CpG islands. Bisulfite sequencing data are shown in Supplemental Figure 3A.