Haploinsufficiency in PTPN2 leads to early onset systemic autoimmunity from Evans syndrome to lupus. Haploinsufficiency in PTPN2 leads to early onset systemic autoimmunity from Evans syndrome to lupus

An exome sequencing strategy employed to identify pathogenic variants in patients with pediatric-onset systemic lupus or Evans syndrome resulted in the discovery of six novel monoallelic mutations in PTPN2. PTPN2 is a phosphatase that acts as an essential negative regulator of the JAK/STAT pathways downstream of several cytokine pathways. All identified mutations led to a loss of PTPN2 regulatory function as evidenced by in vitro cytokine reporter and phosphatase assays, and by hyperproliferation of patients’ T cells stimulated with cytokines. Furthermore, patients exhibited high serum levels of various inflammatory cytokines, mimicking the profile observed in individuals with gain-of-function mutations in various STAT factors. Flow cytometry analysis of patients’ blood cells revealed typical alterations associated with autoimmunity, such as an expansion of CD11c+ B cells and follicular helper T cells, and all patients presented with anti-platelet or other autoantibodies. These findings further supported the notion that a loss of function in negative regulators of cytokine pathways can lead to a broad spectrum of autoimmune manifestations and that PTPN2 along with SOCS1 haploinsufficiency constitute a new group of monogenic autoimmune diseases that can benefit from targeted therapy. Overall design: The expanded T cells were starved of IL-2 for 24h, plated at cell concentration of 1.106 cells/ ml in Panserin medium only and then were left unstimulated or stimulated with IFN-a (104U/ml, Millipore, #IF007) or IL-2 (104U/ml) during 3h at 37°C. RNA was extracted using RNeasy Mini Kit (Qiagen) and quality was assessed using Fragment Analyzer (Agilent Technologies) with RNA Integrity Number >8 and 28S/18S ratio around 2. Messenger RNA was finally converted to complementary DNA by capture of poly-A+ RNA, amplified and sequenced to a depth of at least 50 million reads using the Illumina technology (Novaseq 6000 sequencer) at the Genomic Plateform of Imagine Institut. A1: Patient with the heterozygous mutation p.F403Lfs*25 in PTPN2 A2: Patient with the heterozygous mutation p.F403Lfs*25 in PTPN2 B1: Patient with the heterozygous mutation p.W98* in PTPN2 C1: Patient with the heterozygous mutation p.W289* in PTPN2 D1: Patient with the heterozygous mutation p.E24Mfs*20 in PTPN2 E1: Patient with the heterozygous mutation p.Y126N in PTPN2 F1: Patient with the heterozygous mutation p.C216S in PTPN2 HC1: Healthy donor, female 28 years old HC2: Healthy donor, female, 35 years old HC3: Healthy donor, male, 29 years old