Analysis of deficiency of adenosine deaminase 2 pathogenesis based on single-cell RNA sequencing of monocytes

Abstract

Deficiency of adenosine deaminase 2 (DADA2) is a rare autosomal recessive disease caused by loss‐of‐function variants in the ADA2 gene. DADA2 typically presents in childhood and is characterized by vasculopathy, stroke, inflammation, immunodeficiency, as well as hematologic manifestations. ADA2 protein is predominantly present in stimulated monocytes, dendritic cells, and macrophages. To elucidate molecular mechanisms in DADA2, CD14+ monocytes from 14 patients and 6 healthy donors were analyzed using single‐cell RNA sequencing (scRNA‐seq). Monocytes were purified by positive selection based on CD14 expression. Subpopulations were imputed from their transcriptomes. Based on scRNA‐seq, monocytes could be classified as classical, intermediate, and nonclassical. Further, we used gene pathway analytics to interpret patterns of up‐ and down‐regulated gene transcription. In DADA2, the frequency of nonclassical monocytes was higher compared with that of healthy donors, and M1 macrophage markers were up‐regulated in patients. By comparing gene expression of each monocyte subtype between patients and healthy donors, we identified upregulated immune response pathways, including IFNα/β and IFNγ signaling, in all monocyte subtypes. Distinctively, the TNFR2 noncanonical NF‐κB pathway was up‐regulated only in nonclassical monocytes. Patients’ plasma showed increased IFNγ and TNFα levels. Our results suggest that elevated IFNγ activates cell signaling, leading to differentiation into M1 macrophages from monocytes and release of TNFα. Immune responses and more general response to stimuli pathways were up‐regulated in DADA2 monocytes, and protein synthesis pathways were down‐regulated, perhaps as stress responses. Our identification of novel aberrant immune pathways has implications for therapeutic approaches in DADA2 (registered at clinicaltrials.gov NCT00071045).

What a difference ADA2 makes: Insights into the pathophysiology of ADA2 deficiency from single-cell RNA sequencing of monocytes

“…They found immune responses, phagosome mat-uration, and protein ubiquitination to be up-regulated, and eIF2 signaling, mTOR signaling, and regulation of eIF4 and p70S6K signaling to be down-regulated, probably in line with cell stress response in DADA2. 1 Consistent with a previous report on PBMCs subjected to transcriptome analysis 13 Watanabe et al 1 identify up-regulated genes in type I and type II IFN signaling. Moreover, transcriptome analysis confirms the skewing of macrophage polarization toward an M1 phenotype initially reported by Zhou et al 8 In addition, the authors find an up-regulation of the TNFR2 noncanonical NF-κB pathway genes including several ubiquitin/proteasome pathway genes.…”

Abnormal Changes of Monocyte Subsets in Patients With Sjögren’s Syndrome

“…Though many studies have explored the roles of monocytes in human diseases, findings are inconsistent in both the immunophenotypes of monocyte subsets and their functions. The development of scRNA-seq has provided new opportunities in uncovering monocyte subsets and defining their disturbances in those diseases (14,(35)(36)(37). In the present study, we tried to identify changes in monocyte subsets and transcriptome in SjS patients via scRNA-seq analyses.…”

The Growing Spectrum of DADA2 Manifestations—Diagnostic and Therapeutic Challenges Revisited

“…ADA2 is produced and secreted by activated monocytes, macrophages, and dendritic cells, performing an important function in immune regulation ( 5 , 6 ). ADA2 deficiency results in a predominance of M1 macrophages characterized by increased production of pro-inflammatory cytokines, such as tumor necrosis factor alpha (TNF alpha), an important mediator of vasculitis and tissue damage ( 4 , 5 , 8 , 27 , 28 ). Anti-TNF alpha therapy is well-established in the treatment of juvenile idiopathic arthritis and inflammatory bowel disease ( 29 – 31 ).…”

“…Anti-TNF alpha therapy is well-established in the treatment of juvenile idiopathic arthritis and inflammatory bowel disease ( 29 – 31 ). In DADA2 treatment, anti-TNF alpha agents lead to an improvement of the inflammatory vasculitis phenotype ( 5 , 8 , 12 , 19 , 28 ). In accordance with current and published experiences in DADA2-treatment ( 16 , 19 , 22 , 23 ), we initiated anti-TNF alpha treatment in all three patients as soon as DADA2 was diagnosed.…”