Patent Ductus Arteriosus 3 (PDA3) — Disease Characteristics Research Report

1. Disease Information

Overview. Patent ductus arteriosus 3 (PDA3) is an autosomal-dominant, non-syndromic (isolated) form of patent ductus arteriosus (PDA) caused by heterozygous loss-of-function mutation in PRDM6 (PR/SET domain 6; chromosome 5q23.2). The ductus arteriosus is the fetal vessel connecting the main pulmonary artery to the descending aorta that normally closes within hours to weeks of birth; in PDA3 the vessel remains patent because the vascular smooth muscle cells (VSMCs) of the ductus fail to differentiate and remodel normally, independent of prematurity or other congenital heart disease. PDA3 was defined by Li et al. (2016) after linkage mapping in a large African-American kindred (PDA-101) segregating autosomal-dominant PDA with incomplete penetrance, followed by whole-exome sequencing that identified PRDM6 mutations (Li et al. 2016, AJHG, PMID:27181681).

Key identifiers: - OMIM phenotype: #617039 – PATENT DUCTUS ARTERIOSUS 3; PDA3 (omim.org/entry/617039) - OMIM gene: 616982 – PR DOMAIN-CONTAINING PROTEIN 6; PRDM6 (omim.org/entry/616982) - MONDO: MONDO:0024266 – "patent ductus arteriosus 3," defined as "Any patent ductus arteriosus in which the cause of the disease is a mutation in the PRDM6 gene" - Orphanet (parent nosologic entity): ORPHA:466729 – Familial patent arterial duct (rare, non-syndromic, autosomal-dominant congenital anomaly of the great arteries) — note that PDA in general is not itself in the Orphanet rare-disease nomenclature (ORPHA:706, "non-rare in Europe"); it is the familial/genetic form that is classified as rare (Orphanet) - ICD-10-CM: Q25.0 – Patent ductus arteriosus (the general code; no PDA3-specific code exists) - Gene (HGNC): PRDM6, HGNC:9350, 5q23.2 (GeneCards) - Related loci for genetic heterogeneity of isolated PDA: PDA1 (OMIM 607411, reference/heterogeneity locus symbol), PDA2 (OMIM 617035, caused by TFAP2B, 6p12), PDA3 (OMIM 617039, PRDM6). TFAP2B is also the gene mutated in Char syndrome (syndromic PDA with facial dysmorphism and fifth-finger clinodactyly), and MYH11 mutations cause a distinct syndrome combining thoracic aortic aneurysm/dissection with PDA (not itself numbered "PDA3"). - Synonyms:* PRDM6-related patent ductus arteriosus; familial nonsyndromic patent ductus arteriosus (PRDM6 form)

Evidence basis. All data on PDA3 specifically derive from aggregated, family-based genetic studies (linkage + exome sequencing across pedigrees and unrelated probands) plus a small number of subsequent case reports, not large-scale EHR/individual-patient registries — reflecting its rarity (three known causal variants reported to date, expanded to a handful of additional cases in follow-up reports).

2. Etiology

Disease causal factor: Heterozygous, non-conservative missense mutation in PRDM6, acting via loss of function (impaired nuclear localization and/or altered histone methyltransferase activity), inherited in an autosomal-dominant pattern with incomplete penetrance.

Genetic risk factors (causal)

Three independent PRDM6 mutations have been reported, all in individuals/families with isolated (nonsyndromic) PDA and normal-term birth (i.e., not a prematurity-related PDA):

Statistical enrichment: recurrent independent PRDM6 mutations in this small sample were judged unlikely by chance (p < 4.74 × 10⁻⁶); no nonsynonymous PRDM6 variant was found among 2,000 healthy white control exomes (Li et al. 2016, PMID:27181681).

A subsequent case series identified additional/novel PRDM6 variants (including a previously unreported likely-pathogenic variant) in three patients presenting with both PDA and coarctation of the aorta, extending the phenotypic spectrum beyond isolated PDA (Stanley et al. 2024, Am J Med Genet A, PMID:38071433, PMC summary).

Gene-set enrichment analysis (GSEA) in the same cohort found that rare deleterious variants in broader histone-modification pathway genes were significantly associated with PDA in 15 of 32 affected individuals (estimated OR = 14.95), suggesting epigenetic dysregulation is a recurring theme in nonsyndromic PDA beyond PRDM6 alone.

Broader genetic landscape of isolated/nonsyndromic PDA (context, not PDA3-specific)

• PDA1 (OMIM 607411) — reference locus for genetic heterogeneity of isolated PDA (originally mapped to 5q23 before renaming; a separate autosomal-recessive PDA locus on 12q24 had already used the "PDA1" symbol).
• PDA2 (OMIM 617035) — TFAP2B, 6p12; also causal for Char syndrome (facial dysmorphism, PDA, 5th-finger clinodactyly) when haploinsufficient/dominant-negative missense.
• MYH11 — smooth-muscle myosin heavy chain; mutations cause a syndrome combining thoracic aortic aneurysm/dissection (TAAD) with PDA (Pannu et al. 2007; Zhu et al. 2006, PMID:16444274).
• Candidate/rare-variant genes from exome studies: NOTCH1, FOXC2, CITED2, and others identified via WES/CNV studies of nonsyndromic PDA cohorts (e.g., PMID:35734438, PMC7689032).
• Chromosomal etiologies of PDA broadly: trisomy 21, trisomy 13, trisomy 18, and other aneuploidies/CNVs are well-documented non-Mendelian causes of PDA (not PDA3, but relevant differential).

Environmental / infectious risk factors (for PDA broadly, differential for PDA3)

• Prematurity is the dominant risk factor for PDA in general (up to 30% of infants 500–1500 g by day 3; >70% in infants <1000 g) — this is mechanistically and clinically distinct from the genetic PDA3 form, which occurs in term infants.
• Congenital rubella syndrome: maternal rubella infection in the first trimester is a classic teratogenic/infectious cause of PDA (histopathologically distinct — abnormal elastic tissue in the ductal wall) (PMID reviews on congenital rubella and PDA, PMC6863812).
• High altitude, maternal factors, and other prematurity-associated exposures are risk factors for the sporadic/prematurity form but are not implicated in PDA3.

Protective factors

No specific genetic or environmental protective factors have been reported for PDA3. For prematurity-associated PDA generally, antenatal corticosteroids reduce PDA incidence indirectly by reducing prematurity-related morbidity; this is not disease-specific to PDA3.

Gene-environment interaction

Not established for PDA3; the mechanism is described as a cell-autonomous VSMC differentiation/epigenetic defect rather than gene-environment interaction.

3. Phenotypes

PDA3 presents as an essentially isolated cardiovascular malformation — the reported kindreds and cases are notable for the absence of syndromic features (no consistent facial dysmorphism, limb anomaly, or other organ-system involvement), distinguishing it from Char syndrome (TFAP2B/PDA2).

Severity/progression: Severity is determined by shunt size (small/moderate/large), not by genotype specifically; no PDA3-specific genotype-phenotype severity correlation has been established given the small number of reported families. Course is not episodic — an uncorrected large PDA follows a progressive trajectory toward pulmonary vascular disease if untreated, while a small PDA may remain stable or even undergo spontaneous late closure in rare cases (uncommon after infancy in term-born PDA).

Quality of life impact: Direct QOL data for PDA3 specifically are not available. For symptomatic PDA generally, unrepaired large shunts are associated with exercise intolerance, failure to thrive in infancy, and, if progressing to Eisenmenger physiology, cyanosis and severe functional limitation.

4. Genetic/Molecular Information

Causal gene: PRDM6 (PR domain-containing protein 6), HGNC:9350, chromosome 5q23.2. OMIM gene entry *616982.

Gene product/function: PRDM6 is a nuclear protein expressed selectively in vascular smooth muscle cells. It contains a SET (PR) domain with histone methyltransferase activity and zinc-finger DNA/protein-interaction domains. It acts as a transcriptional repressor of VSMC contractile genes (e.g., MYH11, α-smooth muscle actin) and cooperates with myocardin-related transcription factor-A (MRTF-A) and other SMC transcriptional regulators; it also epigenetically regulates neural-crest-cell specification genes (Wnt1, Tfap2b, Sox9) via H4K20 monomethylation, controlling G1–S progression needed for neural crest delamination/migration into the ductal wall (Zou et al. 2023, JCI Insight, PMID:36749647; additional neural-crest mechanistic paper, PMC8876496).

Variant classification (ACMG/AMP framework, as reported by original authors, not formally re-classified in ClinVar at time of writing):

Zygosity/origin: All reported variants are heterozygous, germline, consistent with autosomal-dominant transmission (no somatic PDA3 cases reported; PDA is not a neoplastic condition).

Functional consequences (mechanistically loss-of-function, established in vitro): - Subcellular mislocalization: Wild-type PRDM6 and p.Cys263Ser localize normally to the nucleus in HEK293 cells and human aortic VSMCs; p.Arg549Gln is predominantly mislocalized to the cytoplasm, with co-staining excluding ER/Golgi/mitochondrial retention — consistent with impaired nuclear import via the disrupted zinc-finger domain. - Histone methyltransferase activity reversed: Wild-type PRDM6 reduces H3K9 dimethylation and increases H4K20 dimethylation; both p.Arg549Gln and p.Cys263Ser show completely opposite effects on these histone marks. - Failure to suppress contractile proteins: Wild-type PRDM6 overexpression suppresses MYH11 in human aortic VSMCs; both mutant proteins largely fail to reduce MYH11, and variant-expressing cells show higher steady-state MYH11 and α-SMA than wild-type. - No dominant-negative dimerization effect: Native PAGE excluded altered wild-type/variant heterodimerization as the mechanism — supporting simple haploinsufficiency-type loss of function rather than dominant-negative protein poisoning.

Modifier genes: None specifically established for PDA3; broader GSEA-level enrichment of histone-modification-pathway variants in the same cohort suggests a possible oligogenic/epigenetic modifier landscape, but no individual modifier gene has been validated.

Epigenetic information: PDA3 is fundamentally a disorder of epigenetic dysregulation — PRDM6 is itself a chromatin-modifying enzyme, and its variants alter H3K9me2/H4K20me2 marks at target loci controlling VSMC differentiation genes. This is the central molecular lesion, not a downstream epiphenomenon.

Chromosomal abnormalities: None reported for PDA3 specifically (contrast with PDA broadly, where trisomy 21/18/13 are well-known non-Mendelian causes).

Suggested ontology terms: - Gene: HGNC:9350 (PRDM6); note dismech convention uses lowercase hgnc:9350 - GO Molecular Function candidates (verify via OAK before binding): histone methyltransferase activity (GO:0042054/more specific child terms), histone H4-K20 methyltransferase activity (GO:0140945 or similar — verify), DNA-binding transcription repressor activity - GO Biological Process candidates: negative regulation of transcription (GO:0045892), histone H4-K20 methylation (GO:0034770), regulation of smooth muscle cell differentiation, neural crest cell migration (GO:0001755)

5. Environmental Information

PDA3 itself is a monogenic condition with no reported environmental modifiers of penetrance or expressivity in the literature. Environmental factors relevant to PDA as a broader clinical entity (but not specifically implicated in the PRDM6-driven form): - Congenital rubella syndrome (infectious/teratogenic) — classic non-genetic cause of PDA, histologically distinct (elastic tissue fragmentation in the ductal wall) from the genetic forms. - Prematurity/hypoxia/high altitude — drive the far more common, non-genetic "premature PDA," mechanistically related to immature oxygen-sensing and prostaglandin-clearance pathways rather than a structural/differentiation gene defect. - No infectious agent, toxin, or lifestyle factor has been linked causally to PDA3.

6. Mechanism / Pathophysiology

Causal chain (PDA3)

1. Heterozygous loss-of-function mutation in PRDM6 (e.g., p.Arg549Gln, p.Cys263Ser, p.Gln462Arg) impairs PRDM6 nuclear localization and/or its histone methyltransferase activity (established in vitro, human/mouse cell systems).
2. Loss of PRDM6 function reverses its normal epigenetic output at target loci: instead of reducing H3K9me2 and increasing H4K20me2, mutant protein produces the opposite chromatin changes (demonstrated in vitro).
3. Altered chromatin state fails to repress VSMC contractile-differentiation genes (MYH11, α-SMA) in ductal smooth muscle cells during fetal life, when PRDM6 is normally highly expressed specifically in ductus arteriosus (but not aortic) smooth muscle (demonstrated by mouse immunofluorescence at E14.5, E17.5, P0.5).
4. This leads to premature differentiation of ductal VSMCs and — paradoxically, despite higher contractile-protein levels — reduced VSMC proliferation and impaired subintimal cushion formation/remodeling of the ductus (the process that normally produces permanent anatomical closure); this step is inferred from the correlative in vitro/mouse expression data rather than directly demonstrated by lineage-tracing loss-of-function in the human variant carriers themselves.
5. Failure of normal ductal wall remodeling results in persistent ductal patency after birth despite the normal postnatal drop in prostaglandin E2 and rise in oxygen tension (i.e., the general perinatal "closure trigger" signal may still occur, but the ductal wall cannot execute the anatomic remodeling response) — clinical PDA.
6. If the ductus remains widely patent, sustained left-to-right shunting leads to pulmonary overcirculation, left heart volume overload, and, if uncorrected over years, progressive pulmonary vascular remodeling → pulmonary arterial hypertension → (in the most severe, longstanding, uncorrected cases) Eisenmenger physiology with shunt reversal and cyanosis.
7. A parallel/branching pathway, shown specifically in mouse neural-crest-conditional Prdm6 knockouts (not yet directly confirmed as the operative mechanism in the human missense-variant carriers): loss of Prdm6-mediated H4K20 monomethylation impairs G1–S cell-cycle progression required for cardiac neural crest cell (CNCC) delamination and migration, via elevated Wnt1 signaling; this reduces CNCC contribution to the ductal smooth muscle layer, independently contributing to a PDA phenotype (Wnt1-Cre and SM22-Cre conditional Prdm6 knockout mice both show complete-penetrance PDA and perinatal lethality) (PMC8876496).

Molecular pathways

• Histone methylation / chromatin remodeling (H3K9me2, H4K20me2) via the PRDM6 SET domain.
• MRTF-A/SRF-dependent smooth-muscle gene transcription — PRDM6 physically interacts with the central and N-terminal actin-binding regions of MRTF-A (JCI Insight, PMC/Zou et al. 2023).
• Downstream target genes altered in Prdm6-depleted mouse ductus arteriosus include the PGE2 receptor EP4 (Ptger4), and transcription factors Tfap2b, myocardin, Foxc1, Hand2; Notch pathway components Jag1, Notch3 are also altered.
• A common non-coding PRDM6 variant (rs17149944) in an SMC-selective intronic enhancer (bound by SRF, RBPJ, TEAD) has separately been proposed as a causal SNP at a cardiovascular/hypertension GWAS locus, indicating a dose-sensitive relationship between PRDM6 expression level and vascular smooth muscle/blood-pressure phenotypes more broadly.

Cellular processes

• Vascular smooth muscle cell (VSMC) differentiation and proliferation (dysregulated — premature differentiation, reduced proliferation).
• Neural crest cell delamination, EMT, and migration (impaired in conditional knockout mice).
• Intimal cushion formation via subendothelial VSMC migration/proliferation and extracellular matrix deposition (the normal anatomic-closure process that fails).
• Contractile response: in a related Prdm6-depletion mouse model, DA segments showed reduced myogenic tone, absent contractile response to KCl, eliminated oxygen-induced constriction, and reduced thromboxane-agonist response (40% vs. 76% in controls) — directly linking loss of PRDM6-regulated SMC identity to failure of the ductal functional constriction response as well as anatomic remodeling.

Protein dysfunction

Loss-of-function via (a) impaired nuclear localization (p.Arg549Gln) and (b) altered catalytic/chromatin-binding output of the SET domain (p.Cys263Ser and, inferentially, p.Gln462Arg) — not dominant-negative dimerization.

Tissue damage mechanism

Not applicable in the classic sense (no cell death/fibrosis/oxidative injury described); the "tissue damage" analog is a developmental patterning failure — the ductal wall never acquires the mature, contractile, remodeling-competent VSMC phenotype needed for closure.

Immune system involvement

None reported.

Suggested GO/CL terms (verify exact IDs/labels via OAK before curating)

• GO Biological Process: "smooth muscle cell differentiation," "positive regulation of vascular associated smooth muscle cell proliferation," "neural crest cell migration" (GO:0001755), "histone H4-K20 methylation"
• GO Molecular Function: "histone methyltransferase activity," "chromatin binding"
• Cell types (CL): vascular associated smooth muscle cell (CL:0000359 — verify), cardiac neural crest cell
• GO Cellular Component: nucleus (GO:0005634) for wild-type PRDM6 localization; cytoplasm (GO:0005737) for the mislocalized p.Arg549Gln variant

7. Anatomical Structures Affected

Organ level: - Primary: Ductus arteriosus (fetal/perinatal vascular structure connecting main pulmonary artery to descending aorta, just distal to the left subclavian artery origin). - Secondary (downstream, shunt-dependent): Left atrium and left ventricle (volume overload/dilation), pulmonary arteries (pressure/flow overload → pulmonary vascular remodeling), and — in the co-occurring phenotype reported by Stanley et al. — the aortic arch (coarctation). - Body systems: Cardiovascular system primarily; pulmonary vascular bed secondarily if the shunt is large and uncorrected.

Tissue/cell level: - Ductus arteriosus smooth muscle cells (specifically — not aortic SMCs, which do not show the same PRDM6 developmental expression decline) are the principal cell population implicated. - Endothelial cells of the ductal intima participate in the normal anatomic remodeling process (subendothelial migration, cushion formation) that fails in PDA3. - Cardiac/vascular neural crest cells contribute to the ductal SMC layer during development; their delamination/migration is impaired in Prdm6-deficient mouse models.

Subcellular level: - Nucleus (site of normal PRDM6 chromatin-modifying activity; site of pathology when nuclear import is disrupted by p.Arg549Gln). - Chromatin/histones (H3K9, H4K20 methylation marks directly altered).

Localization: The ductus arteriosus is a midline, typically solitary structure — laterality is not applicable in the way it is for paired organs; it lies at the aortic isthmus, adjacent to the site where coarctation (also reported in some PRDM6-variant carriers) occurs.

Suggested UBERON term: ductus arteriosus (UBERON:0002106 — verify via OAK).

8. Temporal Development

Onset: Congenital — present from birth in structurally term-appropriate infants (as opposed to prematurity-related PDA, which is a consequence of gestational immaturity rather than a fixed structural anomaly). PDA3 pedigrees are explicitly described as comprising term-born affected individuals.

Onset pattern: The structural lesion is congenital, but clinical detection may occur at any point from the newborn period (murmur on routine exam) through adulthood (incidental finding, or presentation with heart failure/pulmonary hypertension symptoms in a previously undiagnosed adult).

Progression: - Untreated small PDA: often clinically silent and hemodynamically insignificant; may remain stable indefinitely. - Untreated large/moderate PDA: progressive — left heart volume overload → pulmonary overcirculation → progressive pulmonary vascular remodeling → pulmonary arterial hypertension (in ~50% of infants with large nonrestrictive PDA by early childhood) → potential Eisenmenger physiology (shunt reversal, cyanosis, arrhythmia, sudden death) if never closed. - Once anatomically closed (surgically or via catheter device), the ductal lesion itself is cured; any established pulmonary vascular disease may or may not regress depending on how long it was present before closure.

Critical period: The perinatal window (first hours to ~3 weeks after birth) is the critical period for normal anatomic closure (functional closure within hours; anatomic remodeling to a permanent fibrous seal over 2–3 weeks). This is precisely the window in which the PRDM6-dependent transcriptional/epigenetic program is disrupted in PDA3.

Remission: Spontaneous late closure of an isolated PDA in an otherwise term, structurally normal infant beyond early infancy is uncommon; treatment-induced closure (catheter device or surgical ligation) is the standard "remission" pathway.

9. Inheritance and Population

Epidemiology of PDA (general, not PDA3-specific): PDA occurs in 1 in 2,000–5,000 term/live births and accounts for 5–7% of all congenital heart defects; incidence is far higher in preterm infants (up to 70–80% in extremely low-birth-weight infants), but this preterm form is developmentally/mechanistically distinct from PDA3.

PDA3 specifically: Exceedingly rare — the literature to date comprises one large index kindred (PDA-101, 9 affected individuals) plus a small number of additional unrelated probands/families (2 further mutation-positive cases in the original report, plus 3 more recently reported patients with PDA/coarctation and PRDM6 variants). No formal population prevalence estimate exists; it should be considered an "ultra-rare"/"cases in literature" tier of the PrevalenceClassEnum sense.

Inheritance pattern: Autosomal dominant, with incomplete penetrance — explicitly demonstrated in the PDA-101 kindred, where some obligate mutation carriers did not manifest PDA, and further supported by the general finding that PDA has "great phenotypic variability" across TFAP2B/PRDM6 families.

Penetrance: Incomplete; not formally quantified numerically in the literature (unlike some Mendelian conditions with published penetrance percentages).

Expressivity: Variable — ranging from isolated PDA to PDA with coarctation of the aorta in different PRDM6-variant carriers (Stanley et al. 2024).

Genetic anticipation: Not reported/applicable (not a repeat-expansion disorder).

Germline mosaicism: Not specifically reported for PDA3.

Founder effects: Not established; the index kindred is African-American, and additional families are of Iranian and North American/white ancestry in the discovery cohort — suggesting independent mutational events rather than a single founder haplotype.

Consanguinity: Not reported as a feature (autosomal dominant, not recessive).

Carrier frequency: Not applicable in the traditional AR sense; population allele frequency of the specific PRDM6 missense variants is essentially zero in reference databases (absent from >2,000 control exomes at publication).

Population demographics: No specific ethnic/geographic enrichment beyond the ancestry of the reported families (African-American, Iranian, white/North American); sex ratio and detailed age-distribution data specific to PDA3 have not been published (too few cases). For PDA broadly, a female predominance (roughly 2:1 to 3:1) is well documented, but this figure should not be assumed to hold for the genetic PDA3 subtype without dedicated data.

10. Diagnostics

Clinical tests: - Auscultation: classic continuous ("machinery") murmur, best heard at the left infraclavicular/upper sternal border, in a hemodynamically significant PDA. - Echocardiography (2D with color-flow and spectral Doppler) is the primary diagnostic and confirmatory test, establishing ductal patency, direction/velocity of shunt flow, and chamber size/loading conditions. It is standard for both symptomatic detection and "clinically silent" PDA found incidentally on color-flow imaging. - Chest radiography: may show cardiomegaly and increased pulmonary vascular markings in a large shunt (nonspecific). - Cardiac catheterization: used both diagnostically (hemodynamic assessment, pulmonary vascular resistance calculation before intervention in older patients/pulmonary hypertension) and therapeutically (device closure).

Genetic testing: - No PDA3-specific clinical panel is described in the literature reviewed; given the described disease model, genetic evaluation of isolated/familial (rather than prematurity-associated) PDA would reasonably include a congenital heart disease gene panel (covering TFAP2B, PRDM6, NOTCH1, MYH11, FOXC2, etc.) or whole-exome sequencing, particularly when PDA occurs in a term infant with a family history of PDA/other CHD and no syndromic features. - Chromosomal microarray is indicated to exclude aneuploidy/CNV causes of PDA in the differential (trisomy 21/18/13, other CNVs) before attributing an isolated PDA to a monogenic cause like PRDM6. - Sanger confirmation of a candidate PRDM6 variant, with segregation analysis in the family, was the approach used in the discovery studies.

Clinical criteria / differential diagnosis: Differentiate PDA3 from: - Prematurity-associated PDA (gestational-age history is key). - Char syndrome (TFAP2B) — look for facial dysmorphism and 5th-finger clinodactyly/middle-phalanx hypoplasia. - Chromosomal syndromes (trisomy 21/18/13) via karyotype/microarray. - Congenital rubella syndrome — maternal infection history, additional classic triad features (cataracts, sensorineural hearing loss). - Other genetic CHD-PDA associations (e.g., MYH11-associated TAAD/PDA syndrome — screen for aortic aneurysm).

Screening: No population or targeted genetic screening program exists for PDA3 specifically; pulse oximetry newborn screening detects critical CHD generally but is not ductus-specific, and an isolated PDA (without other critical CHD) may not be reliably flagged by oximetry screening alone.

11. Outcome/Prognosis

Survival/mortality: With modern transcatheter or surgical closure, prognosis for isolated PDA (including the PDA3 genetic form) is excellent, with normalization of cardiac loading and low procedural mortality. Untreated large PDA carries substantial long-term morbidity/mortality risk via progression to pulmonary arterial hypertension and Eisenmenger syndrome, which is associated with arrhythmia and sudden cardiac death as late complications.

Morbidity: - Congestive heart failure and failure to thrive in infancy with a large untreated shunt. - Progressive pulmonary vascular disease (~50% of infants with large nonrestrictive PDA develop pulmonary hypertension by early childhood if uncorrected). - Increased risk of infective endarteritis of the ductal lesion (a recognized general PDA complication, though specific incidence data for PDA3 are not available). - In the subset of PRDM6-variant carriers with co-occurring coarctation of the aorta, additional morbidity from arch obstruction (hypertension, arch re-intervention risk) applies.

Recovery potential: Full anatomic and hemodynamic correction is achieved with device or surgical closure in the great majority of cases; pulmonary vascular changes that have already become fixed (established Eisenmenger physiology) may not fully reverse even after closure, and closure can be contraindicated in advanced Eisenmenger physiology (shunt reversal used for right-ventricular decompression).

Prognostic factors: Shunt size/hemodynamic significance, age/timing of diagnosis and closure, and presence of associated lesions (e.g., coarctation) are the operative prognostic variables; no PRDM6-genotype-specific prognostic marker has been established given the small case numbers.

12. Treatment

Pharmacotherapy: Pharmacologic ductal closure agents (indomethacin, ibuprofen, and increasingly paracetamol/acetaminophen — all COX inhibitors reducing PGE2 synthesis) are the mainstay for prematurity-associated PDA in neonates, effective in roughly 70–80% of extremely-low-birth-weight infants. This pharmacologic approach is not the relevant treatment paradigm for PDA3, since the lesion occurs in structurally mature, term infants with a fixed anatomic/developmental ductal-wall defect rather than a reversible prostaglandin-mediated patency — mechanical/procedural closure is expected to be the definitive treatment. - NCIT suggestion: NCIT:C15986 (Pharmacotherapy) as the generic action term, if pharmacologic closure is ever attempted; therapeutic agents indomethacin (CHEBI) or ibuprofen (CHEBI) as therapeutic_agent.

Surgical/interventional (primary treatment modality for PDA3): - Transcatheter device closure is now the treatment of choice for most children >1 year and many infants with favorable ductal anatomy — devices include the Amplatzer Duct Occluder and Amplatzer Piccolo Occluder (implant success ~95.5%, major complication rate ~2.1%, effective closure in ~99.4% at 6 months in one large series). - Surgical ligation/division remains preferred for infants <1 year with anatomy unfavorable for catheter closure. - NCIT suggestions: NCIT:C15329 (Surgical Procedure) for ligation; a device-specific qualifier pattern (per dismech convention) would bind the clinical action (e.g., NCIT:C15329) with a qualifiers predicate-value pair naming the occluder device, since NCIT device terms are not valid treatment_term bindings on their own.

Supportive care: Management of heart failure symptoms (diuretics, fluid management) in infants awaiting closure, or in those with a large symptomatic shunt.

Experimental/advanced therapeutics: No gene therapy, RNA-based therapy, or other advanced modality has been developed or trialed for PDA3; given the structural/anatomic nature of the lesion, mechanical closure rather than molecular correction is the applicable treatment paradigm.

Treatment outcomes: High closure success rates and low complication rates with modern transcatheter devices, as above; surgical ligation carries a low but real risk profile (recurrent laryngeal nerve injury, residual shunt, bleeding) typical of thoracic surgical procedures.

Genetic counseling: Because PDA3 is autosomal dominant with incomplete penetrance, genetic counseling for affected families should address a 50% transmission risk per pregnancy for a carrier parent, with the caveat that not all mutation carriers will manifest PDA (or may show variable expressivity, e.g., isolated PDA vs. PDA with coarctation).

13. Prevention

Primary prevention: No primary prevention exists for the underlying PRDM6 mutation (a de novo or inherited germline variant); genetic counseling and prenatal/preimplantation genetic testing could theoretically be offered in a family with a known pathogenic variant, though this has not been reported as clinical practice for PDA3 specifically given its rarity and generally favorable treatability.

Secondary prevention: Early echocardiographic detection (e.g., prompted by a family history of PDA, or postnatal murmur screening) allows early closure before pulmonary vascular disease develops — this is the principal "prevention" lever for PDA3's main morbidity (Eisenmenger progression).

Tertiary prevention: Timely device/surgical closure once diagnosed prevents progression to pulmonary arterial hypertension and Eisenmenger syndrome.

Screening/genetic counseling: Cascade screening (echocardiography ± targeted genetic testing) of first-degree relatives in a family with a confirmed PRDM6 variant would be a reasonable clinical approach given the autosomal-dominant inheritance, though no formal screening program is published.

Public health: Congenital rubella vaccination programs remain the relevant public-health primary-prevention measure for the infectious form of PDA (not PDA3).

14. Other Species / Natural Disease

Naturally occurring PDA in other species: PDA is a well-recognized, common congenital cardiac defect in dogs (e.g., over-represented in Poodles, Pomeranians, Maltese, and notably studied in the Dutch Stabyhoun breed, where epidemiology and population genetics have been characterized — PMC4906750) and other companion animals; it is generally regarded as heritable/polygenic in most affected dog breeds rather than tied to a PRDM6 ortholog specifically. No PRDM6-specific naturally-occurring veterinary PDA has been reported in the literature surveyed.

Orthologous gene: Prdm6 is conserved from mammals to lower vertebrates; the Li et al. 2016 study explicitly notes that Arg549 is "highly conserved in orthologs from humans to sea anemones," indicating deep evolutionary conservation of this residue/domain.

Comparative pathology: Mouse Prdm6 conditional-knockout studies (below) recapitulate complete-penetrance PDA, supporting cross-species conservation of the PRDM6-dependent ductal-closure mechanism; this is the primary comparative-biology evidence base for PDA3, rather than natural disease in other species.

Zoonotic potential: Not applicable (non-infectious, monogenic developmental disorder).

15. Model Organisms

Mouse models (the dominant model system for PDA3 mechanism):

1. Prdm6fl/fl; Wnt1-Cre2* (neural-crest-specific conditional knockout) — complete-penetrance PDA with perinatal lethality (P0.5–P1.5) in both sexes; neural crest migration/delamination impaired via elevated Wnt1 signaling and reduced H4K20 monomethylation-dependent G1–S progression (PMC8876496).
2. Prdm6fl/fl; SM22-Cre* (smooth-muscle-specific conditional knockout) — also complete-penetrance PDA with perinatal lethality, confirming a cell-autonomous requirement for Prdm6 in ductal SMC identity independent of the neural crest contribution pathway (same source).
3. Prdm6 depletion models used by Zou et al. 2023 (JCI Insight, PMID:36749647) — demonstrated Prdm6's role in maintaining DA-specific SMC gene expression (319 of 519 DA-enriched genes downregulated on Prdm6 depletion), reduced myogenic tone, abolished KCl and oxygen-induced contractile responses, and reduced thromboxane-agonist response, directly linking Prdm6 loss to failure of both anatomic remodeling and functional ductal constriction. Pharmacologic (indomethacin) and oxygen stimulation both failed to induce closure in mutant embryos, unlike controls — a key translational finding showing that the standard postnatal closure triggers are insufficient to overcome the structural/differentiation defect.
4. Immunofluorescence expression-mapping in wild-type mouse ductus arteriosus vs. aorta at E14.5, E17.5, and P0.5 established the developmental expression pattern underpinning the human disease model (high embryonic PRDM6 in DA SMCs, postnatal decline, contrasted with persistent aortic SMC expression) (Li et al. 2016).

Model characteristics: These conditional-knockout mouse models recapitulate the core human phenotype (PDA) with high fidelity and complete penetrance, and additionally reveal a functional-contractility deficit and a neural-crest-migration mechanism not yet directly demonstrated in human PDA3 carriers — representing a model-to-human translational gap: it remains unconfirmed whether the specific human missense variants (haploinsufficient/hypomorphic) produce the same degree of pathway disruption as the mouse complete conditional knockouts (a full biallelic tissue-specific null), which is a candidate HUMAN_MODEL_MISMATCH consideration for KB curation.

In vitro models: HEK293 cells and primary/immortalized human aortic vascular smooth muscle cells (VSMCs) transfected with wild-type or mutant PRDM6 constructs — used for subcellular localization, histone methylation (H3K9me2/H4K20me2), and MYH11/α-SMA suppression assays (Li et al. 2016).

Resources: No dedicated PDA3/PRDM6 mouse strain repository entry (e.g., MGI/IMSR ID) was identified in this search; strains described are custom conditional-knockout lines (Prdm6^fl/fl^ crossed to Wnt1-Cre2 or SM22-Cre) generated by the cited research groups rather than centrally banked at time of publication.

Summary Table of Key Citations

Sources: - OMIM #617039 – PATENT DUCTUS ARTERIOSUS 3; PDA3 - OMIM *616982 – PRDM6 - OMIM #617035 – PATENT DUCTUS ARTERIOSUS 2; PDA2 - OMIM `607411 – PATENT DUCTUS ARTERIOSUS 1; PDA1 - Li N et al. 2016, "Mutations in the Histone Modifier PRDM6 Are Associated with Isolated Nonsyndromic Patent Ductus Arteriosus" — PMC4908195 - Stanley HM et al. 2024, "Patent ductus arteriosus and coarctation of the aorta in association with PRDM6 variants" — PubMed 38071433 - Zou M et al. 2023, "Prdm6 drives ductus arteriosus closure by promoting ductus arteriosus smooth muscle cell identity and contractility" — JCI Insight - Prdm6 controls heart development by regulating neural crest cell differentiation and migration — PMC8876496 - Char Syndrome – GeneReviews, NCBI Bookshelf NBK1106 - Char Syndrome – StatPearls, NCBI Bookshelf NBK604201 - PRDM6 gene – GeneCards - Orphanet: Familial patent arterial duct (ORPHA:466729) - Orphanet: Patent arterial duct (ORPHA:706, non-rare in Europe) - Molecular and Mechanical Mechanisms Regulating Ductus Arteriosus Closure in Preterm Infants – PMC7477801 - Prostaglandin E2–Mediated Relaxation of the Ductus Arteriosus – Circulation - Patent Ductus Arteriosus – Merck Manual Professional Edition - Patent Ductus Arteriosus: A Contemporary Perspective – Journal of the American Heart Association - Catheter Closure of Clinically Silent PDA Using Amplatzer Duct Occluder II – PMC8465329 - Characteristics of Patent Ductus Arteriosus in Congenital Rubella Syndrome – PMC6863812 - Epidemiology, presentation and population genetics of patent ductus arteriosus (PDA) in the Dutch Stabyhoun dog – PMC4906750 - Zhu L et al. 2006, "Mutations in myosin heavy chain 11 cause a syndrome associating thoracic aortic aneurysm/aortic dissection and patent ductus arteriosus" – PubMed 16444274

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Unresolved references

These identifiers did not resolve to a record and may be fabricated. A lookup that failed for transport reasons is indistinguishable from one that failed because the record does not exist, so spot-check before acting on them:

• PMC:PMC38071433 (2 mentions) - NCBI reports no such accession in PMC

References that may not be about this subject

These identifiers resolve, so they are not fabrications, but the records they resolve to share almost none of this report's vocabulary. That is a clue and not a verdict - a paper can be relevant in ways its title and abstract do not spell out - so read them before deciding:

• DOI:10.1161/01.cir.0000145159.16637.5d (2 mentions) - Prostaglandin E ₂ —Mediated Relaxation of the Ductus Arteriosus
• shared terms: ductus, arteriosus

Weighed against this report's own most characteristic terms: pda3, pda, prdm6, genetic, via, ductal, vascular, gene, variant, disease, closure, ductus, arteriosus, congenital, isolated, cell, specifically, syndrome, muscle, mutation.

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:

• MONDO:0024266 (2 mentions) - the report calls it "Ontology identifier for PDA3"; MONDO calls it patent ductus arteriosus 3
• CL:0000359 (1 mention) - the report calls it "verify"; CL calls it vascular associated smooth muscle cell
• UBERON:0002106 (1 mention) - the report calls it "verify via OAK"; UBERON calls it spleen

Obsolete terms

These terms are real but deprecated. Citing one is not a fabrication; it does mean the report is naming something the ontology has retired:

• GO:0034770 (obsolete histone H4-K20 methylation) (1 mention)

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:0002092 (1 mention) - the report calls it "Pulmonary hypertension"; HP calls it Pulmonary arterial hypertension, and lists "Pulmonary artery hypertension" among its other names
• GO:0045892 (1 mention) - the report calls it "GO Biological Process candidates: negative regulation of transcription"; GO calls it negative regulation of DNA-templated transcription
• GO:0005634 (1 mention) - the report calls it "GO Cellular Component: 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: ORPHA.