Immunodeficiency 128 (IMD128) — Comprehensive Research Report

1. Disease Information

Overview. Immunodeficiency-128 (IMD128) is an autosomal recessive combined immunodeficiency (CID) caused by a homozygous missense mutation in COPG1, which encodes the γ1 subunit of the coat protein complex I (COPI). COPI mediates retrograde vesicular trafficking of cargo — including KDEL-motif-bearing endoplasmic reticulum (ER) chaperones — from the Golgi back to the ER. The single reported kindred (five siblings of consanguineous Omani parents) presented in the first year of life with recurrent bacterial and viral infections, failure to thrive, hepatitis, and progressive bronchiectasis, with a combined (T- and B-cell) immunodeficiency phenotype. The molecular mechanism established by the discovery study is that loss of γ1-COP–mediated KDEL-receptor engagement impairs retrieval of chaperones (BiP/GRP78, calreticulin, protein disulfide isomerase) to the ER, producing exaggerated, activation-induced ER stress and unfolded protein response (UPR) signaling selectively in lymphocytes — explaining the immune-restricted phenotype despite COPI's ubiquitous cellular role (Bainter et al., 2021, PMID:33529166).

Key identifiers: - OMIM phenotype: #620983 — IMMUNODEFICIENCY 128; IMD128 (https://omim.org/entry/620983) - OMIM gene: 615525 — COATOMER PROTEIN COMPLEX, SUBUNIT GAMMA-1; COPG1 - Gene symbol / HGNC: COPG1, HGNC:2236 - Cytogenetic location: 3q21.3 - MONDO: MONDO:0975834 (as supplied by the curation stub — not independently cross-verified against a MONDO release in this session; verify with runoak before binding) - Inheritance: Autosomal recessive - Primary literature source: Bainter W, et al. "Combined immunodeficiency due to a mutation in the γ1 subunit of the coat protein I complex." J Clin Invest.* 2021. PMID:33529166 (https://www.jci.org/articles/view/140494)

Synonyms/alternative names: COPG1 deficiency; γ1-COP deficiency; combined immunodeficiency due to COPG1 mutation. No ICD-10/ICD-11 code specific to this ultra-rare monogenic entity was found (it would fall under the broad "Combined immunodeficiency, unspecified" / D81 family in ICD-10). No dedicated MeSH heading exists; it is indexed under "Severe Combined Immunodeficiency" and "COPI Vesicle Coat"-adjacent terms in PubMed.

Data provenance: All disease-level information here derives from a single aggregated disease-mechanism study (whole-exome sequencing of an index family plus mechanistic mouse/cell-line follow-up) rather than an EHR-based cohort or registry — this is a gene-discovery paper, not population-level disease surveillance. There is no OMIM Clinical Synopsis text retrievable in this session (OMIM blocked direct fetch with HTTP 403); the clinical/laboratory detail below is drawn from the JCI primary article and searches, not the OMIM Clinical Synopsis itself — this is a gap to independently verify against OMIM's full entry before curation (flagging per the attribution rule: I did not access omim.org directly).

2. Etiology

Disease Causal Factor: Purely genetic/monogenic. Homozygosity for the COPG1 missense variant c.1954A>G (p.Lys652Glu, p.K652E) is the sole reported cause. No environmental, infectious, or multifactorial contribution to disease initiation is described; the clinical phenotype's severity, however, is modulated by environmental microbial exposure (see Mechanism section — mouse cohousing data).

Genetic risk factors: - The single causal variant identified to date is homozygous COPG1 p.K652E (Bainter et al. 2021, PMID:33529166), found in 5 affected siblings, heterozygous (carrier, unaffected) in both parents — consistent with autosomal recessive inheritance. - Consanguinity is the dominant identified genetic/demographic risk factor: the parents were first-degree or close relatives from Oman, and consanguinity is the mechanism by which a rare recessive allele became homozygous in multiple siblings. - No modifier genes, no digenic contribution, and no other COPG1 alleles have been reported in the literature to date — this remains a single-family, single-variant disease as of this search (September 2026). - I was unable to retrieve COPG1-specific gnomAD constraint metrics (pLI / LOEUF / missense Z) in this session; this should be pulled directly from the gnomAD browser before curation rather than assumed. COPG1 is broadly expressed and essential (it is the major γ-COP paralog used in most tissues, versus the minor paralog γ2-COP/COPG2), so a priori it is plausible the gene is constrained against loss-of-function, but I have no sourced number to cite.

Environmental risk factors: None reported as causal. However, environmental microbial exposure is a documented disease-severity modifier (not a cause): in the Copg1^K652E mouse model, animals raised under specific-pathogen-free (SPF) conditions had a comparatively mild baseline phenotype (hypogammaglobulinemia, defective antibody responses, but grossly normal lymphocyte numbers/proliferation), whereas cohousing with pet-store mice (i.e., exposure to a naturalistic, diverse microbial burden) for 22 days precipitated overt disease: progressive weight loss to ~70% of baseline, T-cell lymphopenia, severely impaired T-cell proliferation, hypergammaglobulinemia, and elevated serum TNF-α, IFN-γ, and IL-6 (Bainter et al. 2021, PMID:33529166). This is strong evidence for a gene-by-environment interaction: the COPG1 mutation creates increased susceptibility to ER stress under the high secretory demand imposed by real-world pathogen exposure, and a low-antigen-burden environment can mask or attenuate the phenotype.

Protective factors: None identified in the human literature. In the mouse model, the chemical chaperone tauroursodeoxycholic acid (TUDCA) — a bile-acid-derived ER-stress-relieving agent — substantially reversed multiple phenotypic and molecular defects both in vitro and in vivo (see Treatment, below); this is best framed as a pharmacologic/therapeutic rescue rather than a naturally occurring protective factor, but it is directly relevant to the disease's gene-environment mechanism (buffering ER stress reduces phenotype severity).

Gene-environment interaction: As above — the core mechanistic insight of the primary paper is precisely a G×E interaction: γ1-COP loss of function creates latent ER-stress vulnerability that is unmasked specifically by the high secretory/proliferative demand lymphocytes experience upon antigenic/microbial activation. This is the central causal-chain logic for the mechanism section below.

3. Phenotypes

All phenotypes below are drawn from the 5-patient Omani sibling cohort in Bainter et al. 2021 (PMID:33529166); frequencies are reported as fractions of 5 unless stated otherwise. Suggested HPO terms are provided for KB curation; these are leads and must be verified against the HPO ontology before binding.

Severity/progression: Onset is uniformly in the first year of life (congenital/infantile-onset CID). The course is progressive in at least one patient (fatal at 3.5 years) and chronic/persistent in survivors (chronic viremia, progressive bronchiectasis). Severity appears to fluctuate with microbial/antigenic exposure burden, consistent with the mouse-model G×E data above — this is an inference from the animal model, not directly demonstrated longitudinally in the human patients within the source material I retrieved.

Quality of life impact: Not formally studied (no PROMIS/EQ-5D/SF-36 data found); QoL impact can be reasonably inferred as substantial given chronic infection burden, growth failure, and one death, but this is inference, not sourced measurement — flag as such in any KB notes:.

4. Genetic/Molecular Information

Causal gene: COPG1 (HGNC:2236; OMIM *615525; chromosome 3q21.3). Encodes the γ1 subunit of the heptameric coatomer (COPI) complex (subunits α/COPA, β/COPB1, β′/COPB2, γ/COPG1, δ/ARCN1, ε/COPE, ζ/COPZ1), which coats vesicles budding from the Golgi for retrograde transport to the ER.

Pathogenic variant: - Variant: c.1954A>G; p.Lys652Glu (p.K652E) (NM_016128 reference transcript implied by standard nomenclature; exact transcript ID not independently confirmed in this session — verify before curation) - Zygosity: Homozygous in all 5 affected siblings; heterozygous (carrier, clinically unaffected) in both parents - Variant type: Missense - Classification: Not independently retrieved from ClinVar in this session — should be checked via ClinVar/VarSome before curation (the variant is very likely listed given the JCI publication, but I have not confirmed the classification string) - Population frequency: Not found in the search results retrieved (gnomAD-specific allele frequency for this exact variant was not confirmed in this session — should be checked directly) - Origin: Germline - Functional consequence: Loss-of-function at the level of a specific protein-protein interaction (structural/interaction-selective LOF) rather than global loss of γ1-COP protein or complete abrogation of all COPI function. Structural modeling in the primary paper predicts the mutation disrupts two stabilizing bonds in the appendage domain of γ1-COP: "a salt bridge between K652 and the carboxyl side chain of E757 and a hydrogen bond between K652 and the main chain carbonyl oxygen of D762" (Bainter et al. 2021, PMID:33529166). Functionally, the mutant coatomer retains normal binding to classic dilysine-motif cargo (e.g., Wbp1) but loses direct binding to the KDEL receptor (KDELR) cytoplasmic tail — i.e., a selective, cargo-specific trafficking defect, not a general COPI assembly failure.

Modifier genes: None established. The paper does note that the paralogous subunit γ2-COP (encoded by COPG2) does not compensate for γ1-COP loss in lymphoid tissue, which may explain the immune-restricted phenotype despite COPI's role in all cells — γ2-COP may substitute sufficiently in non-lymphoid tissues, a mechanistic hypothesis rather than a formally proven modifier relationship.

Epigenetic information: None reported; not applicable/not studied for this disorder.

Chromosomal abnormalities: None — this is a single-nucleotide missense substitution, not a structural/copy-number variant.

Suggested gene binding for KB: gene_term → hgnc:2236 (COPG1); functional_impact_category on the genetic_context block should likely be a selective/partial loss-of-function category (e.g., PARTIAL_LOSS_OF_FUNCTION) rather than a full LOSS_OF_FUNCTION, given the interaction-selective mechanism — this is a curatorial judgment call to make against the primary paper's own framing, not something I am asserting definitively here.

5. Environmental Information

Environmental factors: Not causal for disease initiation (monogenic recessive disease). The key environmental factor is microbial/antigenic exposure burden as a disease-severity modifier, demonstrated experimentally in the mouse model via cohousing with pet-store mice (a standard model for simulating "wild"/naturalistic microbial exposure) versus SPF housing (Bainter et al. 2021, PMID:33529166). No human environmental epidemiology (toxin, occupational, pollution) is relevant or reported.

Lifestyle factors: Not applicable — this is an early-onset monogenic pediatric CID; no lifestyle/behavioral contribution is described.

Infectious agents: Infection is a consequence/manifestation of the immunodeficiency rather than a cause of the disease itself, but specific pathogens recur prominently and are clinically important for the disease's natural history: - Bacterial: Haemophilus influenzae, Streptococcus pneumoniae, Moraxella species (recurrent respiratory infections/pneumonia) - Viral (chronic/persistent viremia, reflecting impaired antiviral clearance): cytomegalovirus (CMV, all 5 patients), Epstein-Barr virus (EBV, 2/5 patients), parvovirus B19 (1/5 patients)

For an environmental[] entry in a KB curation, these would likely be modeled with environmental_effect: EXACERBATES or as downstream infection phenotypes rather than as TRIGGERS of the underlying disease (the disease is present from birth/genetically; infections exacerbate/reveal the clinical course).

6. Mechanism / Pathophysiology

Causal chain (ordered, from the primary paper's mechanistic model)

1. Homozygous COPG1 c.1954A>G (p.K652E) disrupts the appendage-domain structure of γ1-COP, abolishing two predicted stabilizing bonds (K652–E757 salt bridge; K652–D762 hydrogen bond). (Demonstrated: structural modeling + biochemical binding assays.)
2. The structurally altered γ1-COP fails to bind the cytoplasmic KDEL-receptor (KDELR) tail, while retaining normal binding to classic dilysine-motif cargo such as Wbp1 — i.e., a cargo-selective defect in coatomer function rather than global COPI failure. (Demonstrated: direct binding assays.)
3. Loss of coatomer–KDELR engagement impairs retrograde Golgi-to-ER retrieval of KDEL-bearing ER-resident chaperones — BiP/GRP78, calreticulin, protein disulfide isomerase (PDI) — leaving them mislocalized toward/at the Golgi instead of recycled to the ER. (Demonstrated: patient fibroblast VSVGts-KDELR/GM130 colocalization assay showing impaired retrograde transport.)
4. Chronic chaperone mislocalization reduces the ER's folding/quality-control capacity, which is normally buffered at baseline but becomes rate-limiting under high secretory demand. (Inferred from downstream UPR activation data; not directly visualized as "folding failure" per se.)
5. Upon lymphocyte activation (antigen receptor engagement, cytokine stimulation), the massive increase in secretory protein synthesis (immunoglobulin in B cells; cytokines in T cells) exceeds the ER's now-diminished folding capacity, precipitating pathological ER stress selectively in activated — but not resting — B and T cells. (Demonstrated: increased Xbp1/spliced Xbp1 (sXbp1), elevated BiP (Hspa5) expression, PERK-pathway activation with increased CHOP in activated mutant cells; reduced ER size in mutant B cells.)
6. Sustained/exaggerated unfolded protein response (UPR) signaling in activated B cells impairs IgG secretion despite normal plasmablast differentiation and normal class-switch recombination — i.e., a post-differentiation secretory bottleneck rather than a defect in B-cell developmental commitment. (Demonstrated: normal CSR/plasmablast markers, but diminished IgG output.)
7. In activated T cells, UPR/PERK-CHOP activation drives increased apoptosis and reduced cell viability, which secondarily reduces IFN-γ output (a viability effect, not an intrinsic cytokine-production defect) while proliferation and activation-marker expression remain broadly normal. (Demonstrated: apoptosis assays; proliferation and marker studies.)
8. Clinically, impaired antigen-specific antibody production (from step 6) and impaired T-cell survival/effector persistence (from step 7) together produce a combined humoral and cellular immunodeficiency, manifesting as recurrent bacterial respiratory infections, chronic viremia (CMV/EBV/parvovirus B19), and poor vaccine responses. (Clinical observation in the index family, connected to the cellular mechanism by the paper's overall argument — this final clinical link is the paper's central inferential claim rather than a directly traced single-cell-to-bedside proof.)
9. Branch — environmental modulation: Under low antigenic burden (SPF housing in mice), the residual UPR-buffering capacity is sufficient to keep the phenotype relatively mild (hypogammaglobulinemia, poor antibody response only); under high/naturalistic microbial exposure (pet-store cohousing), cumulative secretory/proliferative demand overwhelms buffering, producing overt lymphopenia, weight loss, and systemic inflammatory cytokine elevation (TNF-α, IFN-γ, IL-6) — showing the causal chain above is exposure-dependent in severity, not fixed. (Demonstrated directly in the mouse model.)
10. Therapeutic rescue arm: Pharmacologic ER-stress relief with TUDCA (a chemical chaperone) normalizes sXbp1/Hspa5 expression, restores B-cell IgG secretion, corrects T-cell survival/IFN-γ output in vitro, and reverses antibody-response defects and the pet-store-exposure-induced phenotype in vivo — providing causal (not merely correlative) support for steps 4–8 by showing that relieving ER stress specifically reverses the downstream immune defects. (Demonstrated: in vitro and in vivo TUDCA rescue experiments.)

Category detail

• Molecular pathways: COPI-mediated retrograde vesicular trafficking (Golgi→ER); KDEL-receptor cargo-retrieval pathway; IRE1–XBP1 and PERK–CHOP arms of the unfolded protein response (UPR). Suggested GO terms: GO:0006890 (retrograde vesicle-mediated transport, Golgi to ER); GO:0030968 (endoplasmic reticulum unfolded protein response); GO:0036498 (IRE1-mediated unfolded protein response); GO:0036499 (PERK-mediated unfolded protein response).
• Cellular processes: Activation-induced apoptosis in T cells (GO:0006915 apoptotic process); impaired antibody secretion in B cells (GO:0002377 immunoglobulin production, or more specifically antibody secretion process — verify exact GO ID); ER stress response (GO:0034976 response to endoplasmic reticulum stress).
• Protein dysfunction: γ1-COP loses a specific protein-protein interaction (KDELR binding) via disruption of two intramolecular stabilizing bonds in its appendage domain — a structurally localized, interaction-selective defect rather than global misfolding/instability of γ1-COP itself. Suggested UniProt entry: COPG1_HUMAN (UniProt Q9Y678).
• Biochemical abnormalities: Defective KDEL-receptor engagement by coatomer; secondary chaperone (BiP/GRP78, calreticulin, PDI) mislocalization; secondary XBP1 splicing and CHOP induction as UPR markers.
• Immune system involvement: Combined immunodeficiency — impaired humoral immunity (poor specific antibody responses despite normal B-cell numbers/differentiation) and impaired cellular immunity (CD4+ T-lymphopenia, reduced T-cell survival upon activation, poor T-cell proliferation to mitogen/anti-CD3). This is not autoimmunity/immune dysregulation (contrast with COPA syndrome, below) but a bona fide immunodeficiency.
• Cell types/tissue involvement: Activated CD4+ and CD8+ T cells; activated (antigen/CD40+IL-4-stimulated) B cells and plasmablasts. Suggested CL terms: CL:0000624 (CD4-positive, alpha-beta T cell), CL:0000625 (CD8-positive, alpha-beta T cell), CL:0000236 (B cell), CL:0000980 (plasmablast).
• Advanced/omics data: No transcriptomic, proteomic, single-cell, or spatial datasets were identified as publicly deposited for this specific disease in the sources retrieved; the primary paper's UPR-marker data (Xbp1/sXbp1, Hspa5, CHOP) were generated by targeted qPCR/immunoblot rather than genome-wide profiling, as best I can determine from the retrieved summary. Verify against the full JCI methods/supplement before asserting "no omics data exist."

Cross-paralog comparative mechanism (relevant differential/context)

Other COPI-subunit diseases illustrate that different subunits within the same heptameric complex can produce distinct immunophenotypes: - COPA syndrome (autosomal dominant, COPA, α-COP; OMIM #601924 gene) causes an immune dysregulation/autoinflammatory phenotype (interstitial lung disease ± pulmonary hemorrhage, inflammatory arthritis, immune-mediated kidney disease), mechanistically linked to aberrant STING pathway activation from COPI deficiency (Nature Communications 2022, PMID:35484149; Watkin et al., PMC6372856). - COPB1 deficiency (COPB1, β-COP) causes Baralle–Macken syndrome, combining neurodevelopmental features (global developmental delay, intellectual disability, early-onset cataracts) with combined immunodeficiency features (neutropenia, lymphopenia, impaired specific antibody responses) — a broader multisystem phenotype than IMD128 (PMID:41676145). - COPB2 loss-of-function variants cause a distinct skeletal/microcephaly phenotype, without the same immunodeficiency emphasis.

This positions IMD128/COPG1 deficiency as the coatomer-subunit disorder with the most immunologically "pure" combined-immunodeficiency phenotype identified to date, useful context for the KB's classifications (IUIS immunodeficiency category) and for distinguishing lump/split decisions from COPA syndrome and COPB1 deficiency, which should remain separate disease entries given their genetically and mechanistically distinct (dominant immune-dysregulation vs. recessive multisystem vs. recessive pure-CID) natures.

7. Anatomical Structures Affected

• Organ level: Primary — respiratory system (recurrent pneumonia, bronchiectasis) and lymphoid/immune system (lymphopenia, impaired antibody production). Secondary — liver (hepatitis, present in all 5 patients), growth (failure to thrive, a systemic/endocrine-adjacent secondary effect). Suggested UBERON terms: UBERON:0001004 (respiratory system), UBERON:0002048 (lung), UBERON:0002107 (liver), UBERON:0002405 (immune system).
• Tissue/cell level: Bronchial/pulmonary tissue (bronchiectasis); hepatic parenchyma; lymphoid tissue — specifically activated T and B lymphocytes as the mechanistically critical cell population (see Mechanism section for CL terms).
• Subcellular level: Endoplasmic reticulum (chaperone retrieval failure, UPR activation; GO:0005783 endoplasmic reticulum) and Golgi apparatus (site of COPI vesicle budding and KDELR mislocalization; GO:0005794 Golgi apparatus). Suggested GO Cellular Component terms: GO:0030137 (COPI-coated vesicle), GO:0000139 (Golgi membrane).
• Localization: No lateralization pattern reported (systemic/multi-organ, bilateral pulmonary disease implied by "bronchiectasis" without laterality specified).

8. Temporal Development

• Onset: Infantile — recurrent infections beginning in the first year of life in all 5 reported patients. One patient (P5) had normal CD4+/CD8+ counts documented at birth, suggesting T-cell lymphopenia may develop postnatally/progressively rather than being present in utero — an important nuance for framing "onset."
• Onset pattern: Insidious/chronic rather than acute, punctuated by recurrent infectious episodes.
• Progression: Progressive and chronic. Bronchiectasis (an anatomically progressive, largely irreversible airway process) developed in 3/5 patients. One patient (P4) died at 3.5 years of age from respiratory failure and multiorgan dysfunction, indicating a potentially fatal, progressive course in at least a subset.
• Disease course pattern: Chronic-persistent with recurrent infectious exacerbations (viremia is described as "persistent"/"chronic" rather than episodic-clearing).
• Duration: Chronic, lifelong in survivors (no report of spontaneous resolution).
• Remission: No spontaneous remission reported; TUDCA-based pharmacologic rescue in the mouse model is the only intervention shown to reverse (not merely stabilize) components of the phenotype, and this is preclinical, not yet a demonstrated human remission-inducing therapy.
• Critical periods: Infancy/early childhood is the critical period for clinical presentation and, per the fatal case, mortality risk; no data on prenatal/neonatal screening windows.

9. Inheritance and Population

• Epidemiology: IMD128 is described in exactly one kindred (5 affected siblings from one consanguineous Omani family) as of the primary 2021 publication — no formal prevalence or incidence estimate exists; it should be classified as ultra-rare / cases-in-literature only (n=5) for any Prevalence record (measure_type: CASES_IN_LITERATURE, prevalence_class: NOT_YET_DOCUMENTED or an ultra-rare qualitative tier if only "rare" language is used — do not fabricate a numeric rate).
• Inheritance pattern: Autosomal recessive (confirmed — homozygous in affected siblings, heterozygous carrier parents).
• Penetrance: Appears complete among the 5 homozygous siblings reported (all were symptomatic), though the sample size is too small to make a formal penetrance estimate, and possible variability is suggested by P5's normal birth T-cell counts versus later lymphopenia.
• Expressivity: Variable — bronchiectasis in 3/5, chronic EBV viremia in 2/5, parvovirus B19 in only 1/5, and one death versus four survivors, indicating substantial variable expressivity even within one sibship carrying the identical genotype. This variability is consistent with — and mechanistically explained by — the gene-by-environment (microbial exposure) interaction demonstrated in the mouse model.
• Genetic anticipation: Not applicable/not reported (not a repeat-expansion disorder).
• Germline mosaicism: Not reported/not applicable (biallelic inheritance from two heterozygous carrier parents, not mosaicism).
• Founder effect: Not established as a population founder variant; the variant was identified in one extended consanguineous family. Whether it represents an Omani/Arabian Peninsula founder allele versus a private familial variant is not determined from the sources retrieved.
• Consanguinity role: Central — consanguinity is the mechanism by which the rare recessive allele reached homozygosity in this family; this is explicitly the demographic context of the discovery.
• Carrier frequency: Not established/not found in population databases in this session.
• Population demographics: Only Omani (Arabian Peninsula, Middle Eastern) ancestry is documented. No data on other populations, geographic distribution, sex ratio (the paper does not appear to specify sex distribution among the 5 siblings in the material retrieved — verify from full text), or age distribution beyond the pediatric-onset pattern described above.

10. Diagnostics

Laboratory tests (as performed in the index cohort): - Complete blood count with lymphocyte subset flow cytometry (CD4+, CD8+, B-cell, NK-cell enumeration) - T-cell proliferation assays (response to PHA and anti-CD3 stimulation) - Quantitative serum immunoglobulins (IgG, IgA, IgM) - Specific antibody titers to tetanus, diphtheria, hepatitis B, and measles (pre/post-booster) - In vitro B-cell functional assay: IgG secretion following anti-CD40 + IL-4 stimulation - Viral load monitoring (CMV, EBV, parvovirus B19 PCR/viremia) - Liver function tests (given universal hepatitis)

Genetic testing: - Whole-exome sequencing (WES) was the diagnostic modality that identified the causal COPG1 variant in this family — appropriate as first-tier testing in a suspected novel/undiagnosed CID, especially in a consanguineous pedigree where a homozygosity-mapping-informed WES approach is efficient. - No commercial single-gene or panel test specific to COPG1 CID was confirmed as available in this session (this is a very recently described, single-family gene-disease relationship; coverage on standard primary immunodeficiency gene panels should be checked directly against panel providers such as Invitae/GeneDx/Blueprint Genetics, and against Genomics England PanelApp, which does list COPG1 on its "Primary immunodeficiency or monogenic inflammatory bowel disease" panel per the search result above — https://panelapp.genomicsengland.co.uk/panels/398/gene/COPG1/). - Sanger sequencing was used to confirm the WES-identified variant and to test parental carrier status.

Genetic testing utility (general/inferred): For a CID presenting with the described phenotype, WES or WGS is likely to have higher diagnostic yield than a targeted panel given the extreme rarity/novelty of the gene-disease association; a comprehensive primary immunodeficiency gene panel that includes COPG1 would also be reasonable.

Clinical criteria: No standardized diagnostic criteria (e.g., ESID/PAGID criteria for CID) specific to IMD128 exist; diagnosis rests on the combination of clinical phenotype plus molecular confirmation of biallelic pathogenic COPG1 variants. Differential diagnosis should include other combined immunodeficiencies (SCID variants, other coatomer-subunit disorders such as COPB1 deficiency/Baralle–Macken syndrome, and other CIDs presenting with infantile recurrent infection, failure to thrive, and hepatitis) — distinguishing features from COPB1 deficiency include the presence of neurodevelopmental impairment and cataracts in the latter, which are not reported in IMD128.

Screening: No newborn screening protocol exists for this ultra-rare, recently described condition; it would not currently be detected by standard SCID newborn screening (TREC assay), since the reported patients had detectable (if reduced/declining) T-cell populations rather than a classic SCID-level absence of T cells — this is an inference based on the described lymphopenia pattern, not a directly stated TREC result.

11. Outcome/Prognosis

• Survival/mortality: Of 5 reported patients, 1 (P4) died at age 3.5 years from respiratory failure and multiorgan dysfunction; the other 4 were alive at the time of publication (specific follow-up ages/duration not confirmed in the material retrieved in this session — verify from full text). This gives an observed case-fatality of 1/5 in the only reported cohort — far too small a sample for a formal survival-rate estimate, and this should be presented as raw case count, not extrapolated to a population rate.
• Morbidity: Chronic bronchiectasis (3/5) represents a significant, largely irreversible morbidity affecting long-term pulmonary function. Chronic viremia (CMV/EBV/parvovirus B19) represents ongoing infectious morbidity. Hepatitis (5/5) represents chronic hepatic morbidity of unspecified severity/etiology attribution (viral vs. direct ER-stress-related hepatocyte injury is not distinguished in the sources retrieved).
• Complications: Bronchiectasis, chronic viral infection/viremia, growth failure, and (in one case) fatal multiorgan dysfunction.
• Quality of life: Not formally measured (see Section 3).
• Prognostic factors: No formal prognostic model exists. Based on the mouse-model data, cumulative microbial/antigenic exposure burden is a plausible severity/prognostic modifier, and early recognition with reduced-exposure management (analogous to protective isolation in other CIDs) plus prompt antimicrobial and immunoglobulin support would be the biologically rational, though not yet clinically validated in humans, prognosis-modifying strategy.

12. Treatment

Established human clinical management: The primary source material retrieved does not specify the exact clinical management regimen used for the 5 index patients (e.g., whether IVIG replacement, prophylactic antimicrobials, or hematopoietic stem cell transplantation were used) — I could not confirm these details from the sources available in this session, and this should be verified directly from the JCI full text/supplement before curating specific treatments: entries with NCIT bindings. Given the phenotype (combined immunodeficiency with impaired antibody responses and recurrent bacterial/viral infection), standard-of-care management for CID would conventionally include: - Immunoglobulin replacement therapy (IVIG/SCIG) — NCIT term candidate: generic Pharmacotherapy (NCIT:C15986) with therapeutic_agent bound to an immunoglobulin product, if directly documented in the source - Antimicrobial prophylaxis - Consideration of hematopoietic stem cell transplantation (HSCT) as the only potentially curative option for a genetically defined CID

These are inferred, standard-of-care possibilities based on the disease category, not confirmed treatments documented for this specific cohort in the sources I retrieved — do not curate them into a KB entry as disease-specific evidence without independently sourcing the exact treatment history from the full JCI article or a follow-up case report.

Investigational/preclinical (mechanistically validated in the mouse model, not yet a clinical therapy): - Tauroursodeoxycholic acid (TUDCA) — an ER-stress-relieving chemical chaperone (a bile acid derivative). In the Copg1^K652E mouse model, TUDCA: - Normalized sXbp1 and Hspa5 mRNA expression to wild-type levels in mutant B cells in vitro - Restored IgG secretion in LPS+IL-4-stimulated mutant B cells in vitro - Corrected T-cell survival and IFN-γ secretion upon anti-CD3+anti-CD28 stimulation in vitro - Normalized IgG anti-TNP antibody responses to both T-independent and T-dependent antigens in vivo - Partially reversed cachexia, reversed T-cell lymphopenia, corrected defective T-cell proliferation, and decreased sXbp1 expression when administered during pet-store microbial exposure in vivo - Had no significant effect on wild-type control mice (supporting specificity of the rescue to the mutant genotype) (All: Bainter et al. 2021, PMID:33529166.)

TUDCA is an FDA-approved-adjacent compound in other contexts (it is marketed/used off-label as a chemical chaperone in some settings), but no human clinical trial of TUDCA specifically for IMD128/COPG1 deficiency was found in this search — this represents a clear translational-research gap rather than an established therapy. Suggested NCIT candidate if curated as an experimental treatment: NCIT:C15986 (Pharmacotherapy) with therapeutic_agent bound to a CHEBI term for tauroursodeoxycholic acid (CHEBI ID not independently verified in this session).

Treatment strategy note for KB curation: Given the strength of the mechanistic rescue data, this disease is a strong candidate for a mechanistic_hypotheses/discussions entry (kind: KNOWLEDGE_GAP or a treatment-hypothesis framing) noting that TUDCA and other UPR-modulating agents represent a mechanistically grounded but clinically untested therapeutic avenue — this should be explicitly flagged as preclinical/model-organism evidence (evidence_source: MODEL_ORGANISM and IN_VITRO as appropriate, split by evidence item per the mixed-source rule) and not conflated with an approved human treatment.

13. Prevention

No primary, secondary, or tertiary prevention strategies specific to IMD128 were found. As an autosomal recessive monogenic disease identified in a consanguineous family, the only directly applicable prevention modalities are the general ones applicable to any newly characterized recessive disorder: - Genetic counseling for the family and extended consanguineous kindred regarding recurrence risk (25% for each future pregnancy of carrier parents) — NCIT:C15240 (Genetic Counseling) - Carrier screening / prenatal or preimplantation genetic testing could in principle be offered to the family once the causal variant is known, though no report of this being implemented was found - Cascade/family testing of at-risk relatives given the consanguineous pedigree structure

No population-level newborn screening, vaccination strategy, or public-health intervention exists for this condition, consistent with its status as a single-family, recently discovered ultra-rare disease.

14. Other Species / Natural Disease

Taxonomy: No naturally occurring veterinary/animal disease caused by spontaneous COPG1 mutation was identified in the search (no OMIA entry found in this session). NCBI Taxon: Homo sapiens (NCBITaxon:9606) is the only species with reported natural disease.

Gene orthologs: Copg1 is highly conserved; mouse ortholog Copg1 (used directly to generate the engineered model below). No comparative/orthology database identifiers were independently retrieved in this session (e.g., specific NCBI Gene ID for mouse Copg1 was not confirmed here).

Natural disease in other species: None reported — this is not a known veterinary disease.

Comparative biology: The mouse model (below) represents an engineered, not naturally occurring, disease model, but demonstrates strong evolutionary conservation of the underlying γ1-COP/KDELR/UPR mechanism between mouse and human.

15. Model Organisms

Genetic model: CRISPR/Cas9-generated Copg1^K652E knock-in mouse, homozygous for the orthologous patient mutation, engineered specifically to recapitulate the human disease (Bainter et al. 2021, PMID:33529166). This is a precise, patient-variant-matched knock-in model (not a knockout), directly testing the pathogenicity and mechanism of the identified human allele.

Phenotype recapitulation: - Under SPF (low pathogen exposure) conditions: normal lymphocyte development/numbers, normal T-cell proliferation, but hypogammaglobulinemia and defective antibody responses — a partial/subclinical recapitulation. - Under naturalistic microbial exposure (pet-store mouse cohousing, 22 days): progressive weight loss (to ~70% baseline), T-cell lymphopenia (CD3+, CD4+, CD8+), severely impaired T-cell proliferation, hypergammaglobulinemia, and elevated pro-inflammatory cytokines (TNF-α, IFN-γ, IL-6) — a much closer recapitulation of the overt human clinical phenotype (though the human patients had hepatitis and bronchiectasis, which are not described as reproduced in the mouse model in the material retrieved). - Mechanistically, the mouse model reproduced the key cellular findings from human patient cells: increased ER stress markers (sXbp1, Hspa5/BiP, CHOP) in activated T and B cells, and increased T-cell apoptosis upon activation.

Model limitations: The SPF-housed mouse alone substantially underrepresents disease severity relative to the human phenotype, which is itself the paper's key insight (motivating the environmentally "dirty" cohousing paradigm to unmask the phenotype) — i.e., standard SPF vivarium conditions are explicitly identified as a limitation for recapitulating this particular immunodeficiency. No mouse data on hepatitis, bronchiectasis, or mortality were reported in the material retrieved, so the pulmonary/hepatic end-organ damage seen in human patients is not clearly reproduced (or at least was not described in the summary I retrieved) — flag as an unconfirmed gap rather than asserting either a positive or negative finding without checking the full paper.

Other model systems: - Patient-derived skin fibroblasts were used to demonstrate impaired retrograde COPI transport (increased colocalization of a VSVGts-KDELR fusion reporter with the Golgi marker GM130) — an in vitro human cellular model directly from affected individuals, valuable for confirming variant pathogenicity independent of the mouse system. - No zebrafish, Drosophila, C. elegans, yeast, iPSC, or organoid models of COPG1 deficiency were identified in the sources retrieved for this session.

Research applications: The mouse model is directly useful for studying (1) the UPR/ER-stress mechanism of lymphocyte-restricted immunodeficiency, (2) gene-by-environment interaction in primary immunodeficiency severity, and (3) preclinical testing of ER-stress-modulating therapeutics (TUDCA), as already demonstrated.

Resources: No specific repository/stock number (JAX, MMRRC, IMSR) for the Copg1^K652E mouse line was found in the search results retrieved in this session — this should be checked directly against IMSR/MGI before citing a specific resource identifier.

Summary of Key Gaps and Verification Needs (for curator follow-up)

This report should be treated as a lead, per this repository's evidence-discipline rules — every CURIE, exact quote, and identifier above needs independent verification before being written into a KB YAML file: 1. OMIM full Clinical Synopsis text was not directly retrievable (403 error) — re-fetch from omim.org or via an authenticated/cached source before finalizing phenotype frequencies and any additional clinical detail. 2. gnomAD constraint metrics (pLI/LOEUF) for COPG1, and population allele frequency for the specific c.1954A>G variant, were not found/confirmed in this session. 3. ClinVar classification of the variant was not independently confirmed. 4. Exact human clinical management (IVIG, antimicrobial prophylaxis, HSCT) for the 5 index patients was not confirmed from the sources retrieved — do not assume standard CID management was actually used for this family without checking the JCI full text/methods. 5. Sex distribution and precise ages/follow-up duration of the 4 surviving siblings were not confirmed. 6. MONDO:0975834 mapping was taken from the task's own stub metadata and not independently cross-checked against a live MONDO release in this session. 7. Transcript reference (e.g., NM_ accession) for the c.1954A>G nomenclature was not independently confirmed.

All quoted material above in quotation marks is copied directly, as reported by the fetched source, from the JCI article's text (via WebFetch summarization) or from search-engine-generated summaries of PubMed/JCI content — these are AI-mediated retrievals of the primary source, not my own reading of the original PDF, and should be re-verified against the original JCI article text (open access: https://www.jci.org/articles/view/140494) before being used as an exact-quote snippet: in KB evidence items, per this repository's rule that a snippet must be an exact source substring verified at curation time, not a paraphrase relayed through an intermediate tool.

Sources

• Entry - #620983 - IMMUNODEFICIENCY 128; IMD128 - OMIM
• Entry - *615525 - COATOMER PROTEIN COMPLEX, SUBUNIT GAMMA-1; COPG1 - OMIM
• JCI - Combined immunodeficiency due to a mutation in the γ1 subunit of the coat protein I complex (Bainter et al., 2021, PMID:33529166)
• Gene: COPG1 — Genomics England PanelApp (Primary immunodeficiency panel)
• COPG1 curation results — ClinGen
• COPG1 Gene - GeneCards
• Deficiency in coatomer complex I causes aberrant activation of STING signalling — Nature Communications, PMID:35484149
• Genetics of COPA syndrome — PMC
• Expanding the clinical and immunological phenotypes of COPB1 deficiency, PMID:41676145
• COATOMER PROTEIN COMPLEX, SUBUNIT ALPHA; COPA - OMIM

Reference Validation

Checked with linkml-reference-validator 0.3.0rc1.

Quotes not found in the cited source

Searched the abstract, any retrieved full text, and the title. A quote drawn from a part of the paper that was not retrieved will appear here too, so check before treating one as invented:

Every one of these was searched against an abstract alone, with no full text retrieved - marked abstract only below. Where full text can be fetched, re-running with it will settle them; where the source publishes only a summary to PubMed, as GeneReviews chapters do, it will not, and the quote has to be checked by hand against the chapter itself.

• PMID:33529166 (abstract only): "a salt bridge between K652 and the carboxyl side chain of E757 and a hydrogen bond between K652 and the main chain carbonyl oxygen of D762"
• Text part not found as substring: 'a salt bridge between K652 and the carboxyl side chain of E757 and a hydrogen bond between K652 and the main chain carbonyl oxygen of D762' (note: only abstract available for PMID:33529166, full text may contain this excerpt)

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

• HP:0032179 (1 mention) - the report calls it "verify exact CD8 lymphopenia term"; HP calls it Abnormal circulating globulin concentration

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

• GO:0006890 (1 mention) - the report calls it "retrograde vesicle-mediated transport, Golgi to ER"; GO calls it retrograde vesicle-mediated transport, Golgi to endoplasmic reticulum, and lists "retrograde vesicle-mediated transport, Golgi to ER" among its other names