NKX2-5-Related Congenital, Conduction and Myopathic Heart Disease: Research Report

Target: MONDO:0800441 · Causal gene: NKX2-5 (HGNC:2488, written hgnc:2488 in this repository; OMIM gene *600584) · Category: Mendelian, autosomal dominant

The disease is caused by heterozygous variants in NKX2-5, the homeobox transcription factor gene at chromosome 5q35.1. It is the human counterpart of the Drosophila gene tinman. Everything below is about that gene. It is a different gene from NKX2-1 (thyroid and lung disease), which the repo also holds as NKX2-1_Related_Choreoathetosis....

What the repo already holds. kb/disorders/NKX2-5-Related_Congenital_Conduction_and_Myopathic_Heart_Disease.yaml already exists (834 lines). There is also a leftover stub, stubs/NKX2.5-related_Congenital_Conduction_And_Myopathic_Heart_Disease.yaml, for the same MONDO ID. just tidy-stubs should list it as already_curated. The quotes marked ✔ below are snippets that entry already cites against the local reference cache. Quotes marked ◇ come from search-result abstracts and still need just fetch-reference before use.

1. Disease information

Overview. This is an autosomal dominant cardiac disorder with variable features that can appear together: - congenital heart defects, mostly secundum atrial septal defect (ASD), and also VSD, tetralogy of Fallot (TOF), other conotruncal defects and hypoplastic left heart syndrome (HLHS); - atrioventricular (AV) conduction disease that gets worse over time, often reaching complete heart block; - later-onset myocardial disease: left ventricular noncompaction (LVNC, also called hypertrabeculation) or dilated cardiomyopathy (DCM); - atrial and ventricular arrhythmias, and a markedly raised risk of sudden cardiac death (SCD).

ClinGen's Congenital Heart Disease Gene Curation Expert Panel merged several separate OMIM entities into this one disease ("lumping"). They reasoned that:

✔ "more than 26 unique variants (missense, nonsense, frameshift, deletions) across 18 papers have reported cases of a similar phenotype including congenital heart disease (predominantly ASD), AV block and later onset dilated cardiomyopathy and/or hypertrabeculation with predisposition to atrial and ventricular arrhythmias" (ClinGen CGGV:assertion_c429ebe5…, 2024-11-07)

✔ "Phenotype is variable within families and individuals may have only some of these features." (same record)

Identifiers

Synonyms: NKX2-5-related congenital heart disease; atrial septal defect 7 with or without AV conduction defects (ASD7); CSX-related congenital heart disease; familial ASD with progressive AV block; "Holt–Oram-like ASD with heart block" (historical). (CSX is an old name for the gene; NKX2E is an alias.)

Source type. The evidence is aggregated disease-level knowledge (ClinGen, OMIM, literature reviews) built on family-based linkage, case series and case reports. No EHR-derived cohort exists for it.

2. Etiology

Cause. Germline heterozygous NKX2-5 variants. The founding linkage paper said:

✔ "A dominant disease locus associated with cardiac malformations and atrioventricular conduction abnormalities was mapped to chromosome 5q35, where NKX2-5, a Drosophila tinman homolog, is located." … "Mutations in the gene encoding the homeobox transcription factor NKX2-5 were found to cause nonsyndromic, human congenital heart disease." (Schott et al. 1998, Science, PMID:9651244)

Genetic risk factors and modifiers - Variant class affects the phenotype. Truncating variants and homeodomain missense variants carry the full syndrome:

✔ "Variants causing this phenotype appear to be either truncating or missense within the homeodomain." (ClinGen)

Missense variants outside the homeodomain, found in sporadic CHD, are mostly not associated with AV block. McElhinney et al. (2003, JACC 42:1650–1655; PMID unconfirmed) found NKX2-5 variants in 18 of 608 CHD patients (3%), and most were missense variants outside the homeodomain without AV block ◇. - Genetic background changes penetrance in mice:

✔ "We assessed the role of genetic and environmental factors on the incidence of ventricular septal defects (VSDs) caused by a heterozygous Nkx2-5 knockout mutation." (Winston et al., PMID:22534315)

That study found that inbred strain background and maternal age both changed VSD incidence. This is evidence from mice. - Interacting cardiac transcription factors (GATA4, TBX5, TBX20, HAND2) are biologically plausible modifiers. No human modifier locus has been established.

Environmental and protective factors. None are established in humans. The mouse maternal-age effect (PMID:22534315) is the only gene–environment interaction described, and it is model-organism evidence only. No protective variants are known.

3. Phenotypes

The defining family report is:

✔ "We identified a CHD family with atrial septal defects (ASDs), atrioventricular block, ventricular noncompaction, syncope and sudden death." (PMID:20932824)

Quality of life. No disease-specific QoL data exist. The burden comes from repeated surgery, lifelong pacing, ICD shocks and heart failure.

4. Genetic and molecular information

• Gene: NKX2-5, two exons, encoding a 324-amino-acid NK-2 class homeodomain protein. Its domains are an N-terminal tinman (TN) domain, the homeodomain (about residues 138–197), the NK2-specific domain and a C-terminal transactivation domain. Check the residue boundaries against UniProt P52952.
• Variant spectrum: missense (concentrated in the homeodomain, e.g. T178M, Q181P, I184M, R190C), nonsense, frameshift (e.g. c.512insGC) and whole-gene deletions. Ellesøe's review counted 59 distinct mutations in 202 patients ◇. Most are private to a family. ClinVar classifications should be pulled at curation time.
• Functional consequence: mostly loss of function / haploinsufficiency. Some alleles may be dominant-negative, and some may gain DNA-binding activity:

  ✔ "Two are predicted to impair binding of NKX2-5 to target DNA, resulting in haploinsufficiency, and a third potentially augments target-DNA binding." (PMID:9651244)

✔ "Functional studies indicate that the c.512insGC mutation impedes nuclear localization of NKX2.5 and causes a total loss of transactivation activity of NKX2.5." (PMID:20932824) - Origin: germline. A de novo origin is reported in some sporadic cases. - Population frequency: pathogenic homeodomain and truncating variants are absent or ultra-rare in gnomAD. - Chromosomal: deletions at 5q35 that include NKX2-5 (some overlapping the Sotos region around NSD1) can cause CHD with conduction disease as part of a contiguous-gene syndrome. - Epigenetics: no disease-specific data.

5. Environmental information

No exposures, lifestyle factors or infectious agents are known to cause or trigger this disease. Mouse data show maternal age affects penetrance (PMID:22534315).

6. Mechanism and pathophysiology

Causal chain

1. A heterozygous truncating or homeodomain NKX2-5 variant leads to reduced functional NKX2-5 protein (haploinsufficiency; sometimes dominant-negative), through impaired DNA binding, nuclear import or transactivation ✔ (PMIDs 9651244, 20932824).
2. Reduced NKX2-5 dosage results in misregulated cardiac transcriptional networks. Normally NKX2-5 works with GATA4, TBX5 and TBX20, drives NPPA, GJA5 (Cx40) and MYL2, and represses BMP10 and atrial genes in the ventricles. This regulatory detail is from mouse and in vitro work; in humans it is inferred.
3. Branch A, septation: abnormal atrial septum development and abnormal endocardial-cushion and outflow-tract morphogenesis lead to secundum ASD, VSD and conotruncal defects.

   ✔ "NKX2-5 is important for regulation of septation during cardiac morphogenesis" (PMID:9651244)

4. Branch B, conduction system: dose-dependent hypoplasia of the AV node and His–Purkinje system, followed by progressive loss of conduction cells after birth, leads to progressive AV block. In Jay et al. 2004 (JCI, DOI 10.1172/JCI19846), heterozygous mice had about half the normal number of conduction-system cells ◇. In Pashmforoush et al. 2004 (Cell 117:373, DOI 10.1016/S0092-8674(04)00405-2), ventricle-restricted knockout mice had a hypoplastic AV node at birth, then "selective dropout" of conduction cells and complete heart block ◇.

   ✔ "…for maturation and maintenance of atrioventricular node function throughout life." (PMID:9651244)

✔ "Nkx2-5+/- haploinsufficient mice have an abnormal electrocardiogram, with a prolonged QRS and progressive elongation of the PR interval" (PMID:29979676) 5. Branch C, myocardium: failure of trabecular compaction and loss of ventricular myocyte lineage identity (ectopic BMP10, atrial and conduction-system gene expression in the ventricle) lead to hypertrabeculation/LVNC with subendocardial fibrosis. Over time this progresses to strain defects, DCM and heart failure. ✔ "Conditional deletion of Nkx2-5 at embryonic stages, during trabecular formation, provokes a severe hypertrabeculated phenotype associated with subendocardial fibrosis and Purkinje fiber hypoplasia." … "in 50% of mutant mice, to heart failure." (Choquet et al. 2018, PMID:29979676) 6. Branches B and C together (conduction block, a hypoplastic Purkinje network and a fibrotic, noncompacted myocardium) result in ventricular arrhythmia and sudden cardiac death. SCD has been reported even in people with a working pacemaker. That points to a ventricular arrhythmic substrate, not bradycardia alone. This step is inferred from clinical series.

Suggested GO terms: GO:0003290 atrial septum secundum morphogenesis; GO:0060413 atrial septum morphogenesis; GO:0060412 ventricular septum morphogenesis; GO:0003162 atrioventricular node development; GO:0003161 cardiac conduction system development; GO:0060982 coronary artery morphogenesis / GO:0060993 kidney morphogenesis (not relevant, avoid); GO:0003222 ventricular trabecula myocardium morphogenesis; GO:0061384 heart trabecula morphogenesis; GO:0007507 heart development; GO:0006357 regulation of transcription by RNA polymerase II; GO:0000978 (DNA binding, molecular function).

Suggested CL terms: CL:0002068 Purkinje myocyte; CL:1000409 / CL:1000410 (AV node and His bundle cells; check labels); CL:0002131 regular ventricular cardiac myocyte; CL:0002129 regular atrial cardiac myocyte; CL:0002548 fibroblast of cardiac tissue (check).

Molecular profiling. Transcriptomics of conditional Nkx2-5 mutant mouse hearts is available. GEO:GSE113251 is already cited in the entry ✔ ("identifies Six1 as a marker upregulated in hypertrabeculated hearts"). Patient-iPSC cardiomyocyte studies exist but are small. No human single-cell, spatial or proteomic disease datasets were found.

7. Anatomical structures affected

• Organ: heart (UBERON:0000948). Specifically: interatrial septum (UBERON:0002085), interventricular septum (UBERON:0002094), AV node (UBERON:0002352), bundle of His (UBERON:0002064), Purkinje fibers (UBERON:0002354, check the CURIE), left ventricular myocardium / trabeculae carneae (UBERON:0002084, UBERON:0002513, check). The cardiovascular system is the only system involved, and the disease is non-syndromic.
• Subcellular: nucleus (GO:0005634). Some variants mislocalize the protein to the cytoplasm (PMID:20932824).
• Lateralization: not applicable. The myopathy mainly affects the left ventricle.

8. Temporal development

• Onset: structural defects are congenital. AV conduction delay may be present early, and first-degree block often appears in childhood or adolescence. Higher-grade block, atrial fibrillation, LVNC/DCM and SCD usually appear in adolescence to middle age.
• Course: lifelong and progressive for conduction and myocardial disease. Conduction disease progresses whether or not the ASD is repaired. The disease does not remit.
• Critical window: the gap between diagnosis of an ASD or first-degree AV block and the onset of high-grade block or SCD. This is when ECG/Holter surveillance and timely pacing or ICD decisions matter.

9. Inheritance and population

• Inheritance: autosomal dominant (HP:0000006), with high penetrance for truncating and homeodomain variants. Expressivity is variable even within one family.
• Prevalence: not established. NKX2-5 variants are found in about 1–4% of unselected CHD cohorts (≈3% in McElhinney 2003 ◇). Rates are higher in familial ASD with AV block. A conservative estimate is prevalence_class: NOT_YET_DOCUMENTED or RARE, with measure_type: UNKNOWN.
• No anticipation, founder effects or ancestry bias are known. Both sexes are affected equally. Germline mosaicism is possible but rarely reported.

10. Diagnostics

• ECG: PR prolongation, progressive AV block, QRS widening (LOINC 8626-4 PR interval, 8633-0 QRS duration; check these codes with just loinc-seed-cache). Use Holter or ambulatory monitoring.
• Imaging: transthoracic or transesophageal echocardiography for septal defects. Cardiac MRI for LVNC (noncompacted-to-compacted ratio above 2.3 in diastole, Petersen criteria), LV function and late gadolinium enhancement (fibrosis).
• Genetic testing: single-gene NKX2-5 sequencing plus deletion/duplication analysis. Alternatively, a CHD, cardiomyopathy or conduction-disease panel, or exome sequencing. CMA if syndromic features suggest a 5q35 deletion. Cascade testing of relatives.
• Clinical clue: ASD plus AV block in a family should prompt NKX2-5 testing.
• Differential diagnosis:
• Holt–Oram syndrome (TBX5; upper-limb defects);
• GATA4-related CHD (usually no AV block);
• LMNA cardiomyopathy (AV block plus DCM; no ASD; raised CK);
• SCN5A progressive cardiac conduction disease;
• TBX20;
• MYH6-related ASD;
• TBX5;
• post-surgical heart block.

11. Outcome and prognosis

• SCD is the main cause of death. In the Ellesøe review it occurred in 15% of individuals in families with ASD plus conduction disease (9 confirmed and 10 possible carriers) ◇ (PMID:26679770), and some deaths happened despite a pacemaker.
• Other burdens: heart failure from DCM/LVNC, and atrial fibrillation with thromboembolic risk.
• Prognostic factors: truncating or homeodomain variant; family history of SCD; LV dysfunction; ventricular arrhythmia; fibrosis on MRI. Formal risk models are not available.

12. Treatment

There is no disease-modifying therapy, so management is symptomatic and preventive.

Pacing (prefer physiologic, conduction-system pacing) and ICDs carry lifelong device risks. No pharmacogenomic issues, gene therapy or registered disease-specific trials were found.

13. Prevention

• Primary: no primary prevention exists apart from reproductive options: prenatal testing or preimplantation genetic testing for a known familial variant.
• Secondary: cascade genotyping of relatives. Serial ECG, Holter, echocardiography and MRI in carriers, including those with a repaired or absent ASD.
• Tertiary: pacing at the onset of high-grade block, and a low threshold for an ICD.
• No vaccines or public-health measures apply.

14. Other species

No naturally occurring animal disease is recorded in OMIA (check before citing). The gene is highly conserved: mouse Nkx2-5 (MGI:97350, check), zebrafish nkx2.5, Drosophila tin.

15. Model organisms

Limits of the mouse models: mice show the septal and conduction features at a mouse heart rate. Human-like adult SCD and atrial fibrillation are not modelled well, and the strain-dependent penetrance argues for a HUMAN_MODEL_MISMATCH discussion.

Curation notes for the existing entry

• The stub is stale: the KB already holds this MONDO ID. just tidy-stubs --apply should delete it.
• The entry relies on only four PMIDs. These papers are worth adding with just fetch-reference:
• Benson et al. 1999 (JCI 104:1567; DOI 10.1172/JCI8154; PMID 10587520 from a third-party mirror, so confirm it). This covers the TOF, VSD and conotruncal spectrum.
• Ellesøe et al. 2016 (PMID:26679770). This covers SCD frequency and the ICD recommendation.
• Pashmforoush et al. 2004 (Cell). This covers conduction-cell dropout and BMP10.
• Jay et al. 2004 (JCI). This covers dose-dependent conduction-system hypoplasia.
• Morlanes-Gracia et al. 2021 (Front Cardiovasc Med, PMC8280289; p.Gln181Pro with LVNC and SCD).
• Hanley et al. 2016 (BMC Med Genet, PMC5114776; DCM).
• McElhinney et al. 2003 and Elliott et al. 2003 (JACC). These cover genotype–phenotype data in sporadic CHD and HLHS.
• Run just check-genereviews on the entry. I found no GeneReviews chapter specific to NKX2-5.
• Every HPO, GO, CL, UBERON, NCIT and LOINC CURIE suggested above is a lead I recalled, not something I looked up. Verify each one in cache/<prefix>/terms.csv, with runoak, or in OLS before binding it.

Sources

• Schott JJ et al. 1998 Science — PMID:9651244 (cached in repo)
• Ouyang P et al. 2011 — PMID:20932824 (cached)
• Winston JB et al. 2012 — PMID:22534315 (cached)
• Choquet C et al. 2018 — PMID:29979676 (cached)
• ClinGen GDV CGGV:assertion_c429ebe5-43ec-40e7-9d73-55bbbb44f6d1-2024-11-07T170000.000Z (cached)
• Benson et al. 1999, JCI (PMC409868) · JCI PDF
• Ellesøe et al. 2016, Congenit Heart Dis — PubMed 26679770 · record
• Pashmforoush et al. 2004, Cell (Scilit)
• Jay et al. 2004, JCI
• Lyons et al. 1995, Genes Dev
• Tanaka et al. 1999, Development (via JCI references)
• Morlanes-Gracia et al. 2021, Front Cardiovasc Med (PMC8280289)
• Hanley et al. 2016, BMC Med Genet (PMC5114776)
• Chung & Rajakumar 2016, "Genetics of CHD: the NKX2-5 gene, a key player" (PMC4773750)
• McElhinney / Elliott 2003 JACC records

Reference Validation

Checked with linkml-reference-validator 0.5.1.

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.

• PMC:PMC4773750 (abstract only): "Genetics of CHD: the NKX2-5 gene, a key player"
• closest text in source: "The mutant NKX2-5 factor can regulate a number of off-targets downstream to facilitate CHD development"

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:

• GO:0000978 (1 mention) - the report calls it "DNA binding, molecular function"; GO calls it RNA polymerase II cis-regulatory region sequence-specific DNA binding
• NCIT:C15986 (2 mentions) - the report calls it "Anticoagulation for atrial fibrillation; anticoagulation in LVNC with LV dysfunction"; NCIT calls it Pharmacotherapy

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:

• HP:0004383 (1 mention) - the report calls it "Hypoplastic left heart"; HP calls it Hypoplastic left ventricle
• HP:0011705 (1 mention) - the report calls it "First-degree AV block"; HP calls it First degree atrioventricular block
• CL:1000410 (1 mention) - the report calls it "AV node and His bundle cells; check labels"; CL calls it myocyte of atrioventricular node, and lists "AV node cardiac muscle cell" among its other names
• UBERON:0000948 (1 mention) - the report calls it "Organ: heart"; UBERON calls it heart**, and lists "branchial heart" among its other names
• GO:0005634 (1 mention) - the report calls it "Subcellular: nucleus"; GO calls it nucleus**, and lists "cell nucleus" among its other names

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: MGI.