CECR1 Human

What is CECR1 and what is its relationship to ADA2?

CECR1 is the gene encoding adenosine deaminase-2 (ADA2). It was originally named due to its location on chromosome 22 in the region affected in patients with cat eye syndrome . ADA2 was first identified in 1978 in spleen extracts from patients with ADA-SCID as a protein accounting for remnant adenosine deaminase activity in the absence of functional ADA1 . Unlike ADA1, ADA2 is unaffected by the ADA1-inhibitor erythro-9-(2-hydroxy-3-nonly)adenine (EHNA), has a lower pH optimum at 6.5, and a Michaelis constant of approximately 2 mM .

How does ADA2 function differ from ADA1 in research contexts?

When studying ADA2 enzymatic activity, researchers should note that ADA2 has distinct biochemical properties compared to ADA1. ADA2 functions optimally at pH 6.5 rather than the neutral pH preferred by ADA1 . In experimental settings, ADA2 can be selectively analyzed in the presence of EHNA, which inhibits ADA1 but not ADA2 . Methodologically, this allows for differential assays where ADA1 activity is suppressed while measuring ADA2 function in mixed biological samples.

What cellular and molecular processes are regulated by ADA2?

ADA2 plays a significant role in regulating macrophage polarization toward the M2 phenotype . In research models, ADA2 has been shown to modulate proangiogenic properties of macrophages via PDGFB production and paracrine signaling to pericytes . Experimentally, both loss and gain of function studies have demonstrated that PDGFB mRNA and protein levels in macrophages are directly modulated by ADA2 . When designing experiments to study ADA2 function, researchers should consider its extracellular activity, though recent evidence suggests it may also fulfill intracellular roles that remain incompletely understood .

What are the population-specific founder mutations in CECR1?

Researchers studying specific populations should be aware of founder mutations that vary by ethnicity. The R169Q mutation is a founder mutation in the Dutch population, while the G47R mutation is a founder mutation in Middle Eastern and Pakistani populations . This information is particularly valuable when designing targeted genetic screening approaches for specific populations. The table below summarizes confirmed pathogenic variants identified in research cohorts:

How should novel CECR1 variants be interpreted in research contexts?

The CECR1 gene is highly polymorphic, requiring cautious interpretation of identified variants . Researchers should implement a systematic approach incorporating: (1) segregation analysis using parental samples; (2) biochemical confirmation through ADA2 activity assays; (3) computational predictions of variant effects on protein structure/function; and (4) functional studies in appropriate cell models . For variants of uncertain significance, researchers should consider the possibility that single mutations may act as susceptibility alleles for complex forms of vasculitis rather than causative mutations for classical DADA2 .

What experimental approaches best elucidate the pathophysiology of ADA2 deficiency?

Research into ADA2 deficiency pathophysiology requires multiple complementary approaches. Three-dimensional co-culture systems incorporating macrophages, endothelial cells, and pericytes have been effective in modeling the vascular effects of ADA2 deficiency . In such systems, CECR1 knockdown by siRNA in macrophages inhibits new vessel formation, while CECR1 stimulation promotes angiogenesis . Researchers investigating immune dysregulation should examine type I interferon signatures in peripheral blood, as upregulation of interferon-stimulated genes has been observed in DADA2 patients . When studying bone marrow manifestations, which respond poorly to standard treatments, specialized hematopoietic stem cell models may be required.

How does ADA2 deficiency affect macrophage-pericyte interactions in vascular pathology?

ADA2 deficiency disrupts critical cross-talk between macrophages and pericytes in the vascular microenvironment. Mechanistically, ADA2 in macrophages promotes PDGFB production, which acts in a paracrine manner on PDGFRβ receptors on pericytes . Experimentally, this can be demonstrated through transwell migration assays, which show that ADA2-mediated signaling enhances pericyte migration . Additionally, this signaling pathway increases expression and deposition of periostin, a matrix component with proangiogenic properties . When designing experiments to study this interaction, researchers should consider three-dimensional co-culture systems that allow for cell-cell communication through both direct contact and soluble mediators.

What is the role of interferon signaling in ADA2 deficiency pathogenesis?

Type I interferon signaling appears to contribute to DADA2 pathogenesis in a subset of patients. Research approaches should include measurement of interferon signature genes in peripheral blood, as increased expression of these genes has been documented in multiple DADA2 cohorts . The interferon signature correlates with disease severity as measured by CRP levels, suggesting its potential utility as a biomarker for disease activity . The table below summarizes findings on interferon signatures across DADA2 patient cohorts:

What comprehensive diagnostic algorithm should be used for suspected ADA2 deficiency?

A systematic diagnostic approach for ADA2 deficiency should combine genetic, biochemical, and clinical evaluations. Initial screening should include Sanger sequencing of all coding exons of CECR1 . For patients with a single identified mutation or strong clinical suspicion despite negative genetic testing, additional analysis for large deletions or non-coding variants should be performed . Biochemical confirmation through ADA2 enzyme activity assays provides functional validation of genetic findings . Clinically, researchers should be alert to diverse manifestations beyond vasculitis, including hematological abnormalities (cytopenias, bone marrow failure), immunodeficiency (B cell deficiency, hypogammaglobulinemia), and neurological symptoms (stroke, encephalitis, neuropathy) .

How can interferon signatures be utilized as biomarkers in ADA2 deficiency research?

Interferon signatures offer valuable biomarkers for research into ADA2 deficiency. Methodologically, quantitative PCR of interferon-stimulated genes in peripheral blood can generate an interferon score (IS) that correlates with disease activity . This approach has shown that the IS decreases significantly after initiation of TNF inhibitor therapy in responsive patients, suggesting its utility in monitoring treatment efficacy . Research protocols should include measurement of both type I and type II interferon pathways, as some patients demonstrate elevation of both signatures . When analyzing interferon signatures, researchers should note that they may be elevated even in asymptomatic carriers of CECR1 mutations, potentially identifying individuals at risk before clinical manifestations appear .

What neurological manifestations should prompt consideration of ADA2 deficiency in research cohorts?

Researchers studying cryptogenic stroke or unusual neuroinflammatory conditions should consider ADA2 deficiency in their differential diagnosis. Approximately 5.7% of DADA2 patients present with neurological symptoms as their initial manifestation, and 0.6% have exclusively neurological disease . The clinical spectrum includes ischemic stroke (particularly affecting deep nuclei and brainstem), hemorrhagic stroke, encephalitis, posterior reversible encephalopathy syndrome, mononeuropathy, and polyneuropathy . In cohort studies, up to 28% of DADA2 patients present with TIA or ischemic stroke . Importantly, conventional stroke therapies (antiplatelet and anticoagulant agents) are contraindicated in DADA2 as they may precipitate hemorrhagic strokes, highlighting the critical importance of accurate diagnosis .

How should research protocols be designed to evaluate novel therapies for ADA2 deficiency?

Research protocols evaluating novel therapies should incorporate multi-parameter outcome measures addressing the diverse manifestations of ADA2 deficiency. When designing clinical trials, investigators should stratify patients based on phenotype (vasculitic, immunodeficiency, hematological) as these may respond differently to targeted interventions . Outcome measures should include: (1) clinical disease activity scores; (2) laboratory biomarkers including inflammatory markers and interferon signatures; (3) functional vascular assessments; (4) quality of life metrics; and (5) long-term safety monitoring . For hematological manifestations, which respond poorly to current therapies, specialized endpoints including bone marrow cellularity and lineage-specific differentiation should be included.

What therapeutic approaches should be investigated for bone marrow failure in ADA2 deficiency?

Bone marrow failure in ADA2 deficiency represents a significant therapeutic challenge requiring dedicated research efforts . Experimental approaches should investigate: (1) hematopoietic stem cell transplantation, which has shown promise in case reports; (2) targeted cytokine modulation beyond TNF inhibition; (3) gene therapy approaches to restore ADA2 function in hematopoietic stem cells; and (4) ex vivo expansion and modification of autologous stem cells . Research protocols should incorporate in vitro models of hematopoiesis using patient-derived cells to screen potential therapeutic agents before clinical application. As bone marrow failure can be life-threatening, development of effective treatments represents an urgent research priority.

How does CECR1/ADA2 function in tumor microenvironments and what are the implications for cancer research?

ADA2 demonstrates significant effects on tumor microenvironments, particularly in glioblastoma multiforme (GBM). Research approaches should utilize immunohistochemical evaluation of tumor samples, which has shown that CECR1 expression correlates with microvascular density in GBM . Mechanistically, ADA2 expressed by M2-like tumor-associated macrophages promotes angiogenesis through PDGFB-PDGFRβ signaling to pericytes . This cross-talk enhances pericyte recruitment, migration, and deposition of proangiogenic matrix components . These findings suggest that targeting CECR1/ADA2 could offer a novel approach for anti-angiogenic therapy in GBM through immune modulation rather than direct targeting of vascular growth factors .

What are the molecular mechanisms of single heterozygous CECR1 variants in complex vascular diseases?

The role of single heterozygous CECR1 mutations as susceptibility factors for complex vascular diseases requires sophisticated research approaches. In cohorts of patients with polyarteritis nodosa (PAN), approximately 6.5% carry mutations in CECR1, with half having biallelic mutations and half carrying single variants . Experimental designs to investigate these carriers should include: (1) quantitative analysis of ADA2 enzymatic activity to detect partial deficiencies; (2) cellular stress response studies to identify threshold effects; (3) interaction studies with other genetic and environmental risk factors; and (4) long-term prospective monitoring to determine if these individuals develop subclinical or overt disease over time .

How can structural biology approaches inform therapeutic development for ADA2 deficiency?

Structural biology offers powerful tools for understanding the molecular pathogenesis of ADA2 mutations and developing targeted therapies. Researchers should employ X-ray crystallography, cryo-electron microscopy, and molecular dynamics simulations to characterize how specific mutations affect ADA2 protein structure, dimerization, catalytic function, and protein-protein interactions. This information can guide rational design of: (1) small molecule chaperones to rescue misfolded ADA2 variants; (2) enzyme replacement therapies with enhanced stability or targeted delivery; (3) gene editing approaches addressing specific mutation types; and (4) structure-based screening for modulators of ADA2 activity or downstream signaling pathways . Understanding the structural consequences of founder mutations (R169Q, G47R) should be prioritized given their prevalence in specific populations .