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NBAS, a gene involved in cytotoxic degranulation, is recurrently mutated in pediatric hemophagocytic lymphohistiocytosis

ABSTRACT: Hemophagocytic lymphohistiocytosis (HLH), particularly primary HLH (pHLH), is a rare, life-threatening disease. Germline genetic deficiency of 12 known HLH genes impairs cytotoxic degranulation in natural killer (NK) cells or cytotoxic T lymphocytes (CTLs) and contributes to pHLH development. However, no pathogenic mutations in these HLH genes are found in nearly 10% of HLH patients, despite a strong suspicion of pHLH, suggesting that the underlying genetic basis of HLH is still unclear. To discover novel susceptibility genes, we first selected 13 children with ppHLH (presumed primary HLH patients in the absence of detectable known HLH gene variants) and their parents for initial screening. Whole-genome sequencing (WGS) in one trio and whole-exome sequencing (WES) in twelve trios revealed that two ppHLH patients carried biallelic NBAS variants, a gene that is involved in Golgi-to-endoplasmic reticulum (ER) retrograde transport upstream of the degranulation pathway. Additionally, two candidate genes, RAB9B and KLC3, showed a direct relationship with known HLH genes in protein-protein interaction (PPI) network analysis. We analyzed NBAS, RAB9B, KLC3 and known HLH genes in an independent validation cohort of 224 pediatric HLH patients. Only biallelic NBAS variants were identified in three patients who harbored no pathogenic variants in any of the known HLH genes. Functionally, impaired NK-cell cytotoxicity and degranulation were revealed in both NBAS biallelic variant patients and in an NBAS-deficient NK-cell line. Knockdown of NBAS in an NK-cell line (IMC-1) using short hairpin RNA (shRNA) resulted in loss of lytic granule polarization and a decreased number of cytotoxic vesicles near the Golgi apparatus. According to our findings, NBAS is the second most frequently mutated gene (2.11%) in our HLH cohort after PRF1. NBAS deficiency may contribute to the development of HLH via a dysregulated lytic vesicle transport pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-022-01318-z.

SUBMITTER: Bi X

PROVIDER: S-EPMC9331571 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Expression data from CD8+ T cells and CD68+ monocytes from patients with hemophagocytic lymphohistiocytosis, sepsis, and persistent systemic inflammatory response syndrome Hemophagocytic lymphohistiocytosis (HLH) is a syndrome characterized by pathologic immune activation in which prompt recognition and initiation of immune suppression is essential for survival. Children with HLH have many overlapping clinical features with critically ill children with sepsis and persistent systemic inflammatory response syndrome (SIRS) in whom alternative therapies are indicated. To determine if plasma biomarkers could differentiate HLH from other inflammatory conditions and to better define a ‘core inflammatory signature’ of HLH, concentrations of inflammatory plasma proteins were compared in 40 patients with HLH to 47 pediatric patients with severe sepsis or SIRS. Seventeen of 135 analytes were significantly different in HLH plasma compared to SIRS/sepsis, including increased interferon-gamma (IFNg)-regulated chemokines CXCL9, CXCL10 and CXCL11. Further, a 5-analyte plasma protein classifier including these chemokines was able to differentiate HLH from SIRS/sepsis. Gene expression in CD8+ T cells and CD68+ monocytes from blood were also enriched for IFNg pathway signatures in peripheral blood cells from patients with HLH compared to SIRS/sepsis. This study identifies differential expression of inflammatory proteins as a diagnostic strategy to identify critically ill children with HLH. Further, comprehensive unbiased analysis of inflammatory plasma proteins and global gene expression demonstrates that IFNg signaling is uniquely elevated in HLH. In addition to demonstrating the ability of diagnostic criteria for HLH, sepsis and SIRS to identify groups with distinct inflammatory patterns, results from this study support the potential for prospective evaluation of inflammatory biomarkers to aid in diagnosis of and optimizing therapeutic strategies for children with distinctive hyperinflammatory syndromes.

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NBAS, a gene involved in cytotoxic degranulation, is recurrently mutated in pediatric hemophagocytic lymphohistiocytosis

Supplementary Information

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