Autosomal Dominant Optic Atrophy

Mendelian MONDO:0008134 Pathograph 22 Show in embeddings browser

Classic (non-syndromic) autosomal dominant optic atrophy — Kjer optic atrophy, optic atrophy type 1 — is the commonest inherited optic neuropathy. In the majority of genetically solved cases it is caused by a heterozygous loss-of-function variant in OPA1, which encodes a dynamin-related GTPase anchored to the mitochondrial inner membrane. Insidious, bilateral, broadly symmetric visual loss begins in the first decade, with temporal or diffuse optic disc pallor, a centrocecal or central scotoma, and an acquired blue-yellow (tritan) colour vision defect. Penetrance is incomplete and expressivity varies markedly within and between families. The entry is deliberately restricted to the non-syndromic phenotype. OPA1 is a multifunctional protein, and the mechanism is curated as four separable consequences of reduced OPA1 dosage — failure of inner-membrane fusion, disorganization of cristae, impaired maintenance of the mitochondrial genome, and loss of cytochrome c sequestration — which converge on an oxidative phosphorylation deficit. The selectivity of the disease is modelled as a property of the target tissue rather than of the lesion: retinal ganglion cell axons are unmyelinated between the cell body and the lamina cribrosa, carry a correspondingly high energy cost, and the smallest-calibre fibres of the papillomacular bundle fail first. Why a ubiquitously expressed gene produces an essentially eye-restricted disease is not settled, and is recorded as a knowledge gap rather than asserted.

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Mappings

MONDO

MONDO:0020250 autosomal dominant optic atrophy Not Yet Curated

MONDO:0020250 is the MONDO parent grouping of this entry's anchor MONDO:0008134 and also subsumes the syndromic DOA plus concepts curated in Autosomal_Dominant_Optic_Atrophy_Plus. broadMatch, not exactMatch: the parent is a union of the classic and the syndromic forms, so it must not retire either concept from the curation queue.

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Inheritance

Autosomal dominant HP:0000006

Heterozygous OPA1 variants are transmitted in an autosomal dominant manner with incomplete penetrance. Penetrance recalculated within families segregating the recurrent c.2708_2711delTTAG allele was as low as 43% and 62%, far below the ~98% previously reported, and the authors argue that if haploinsufficiency is the mechanism then reduced penetrance should not be allele-specific. The penetrance_percentage slot records the lower of the two family-level figures; it is a single-study family estimate, not a population penetrance.

Autosomal dominant inheritance Penetrance: INCOMPLETE Penetrance %: 43 Expressivity: VARIABLE

Show evidence (4 references)

PMID:11440989 SUPPORT Human Clinical

"A re-calculation of the penetrance of this disorder within two of our families indicates figures as low as 43 and 62% associated with the 2708del(TTAG) mutation."

Source for the reduced-penetrance figures recorded here.

PMID:11440989 SUPPORT Human Clinical

"If haploinsufficiency is the mechanism underlying DOA it is unlikely that this figure will be mutation-specific, indicating that the penetrance in DOA is much lower than the 98% reported previously."

Supports treating reduced penetrance as a general property of the haploinsufficiency mechanism rather than of one allele.

PMID:20301426 SUPPORT Human Clinical

"Each child of an individual with OPA1 has a 50% chance of inheriting the pathogenic variant."

Source for the 50% per-child transmission risk that the Genetic Counseling treatment entry states.

+ 1 more reference

Discussions and Knowledge Gaps

Why does halving the dose of OPA1 — a gene expressed ubiquitously, and expressed highly in brain and auditory neurons — produce a disease that is essentially confined to retinal ganglion cells, and within that population to the smallest-calibre papillomacular fibres?

KNOWLEDGE GAP OPEN rgc_selectivity_of_a_ubiquitous_gene

Attached to

pathophysiology#Energetic Vulnerability of the Unmyelinated Prelaminar Axon pathophysiology#Selective Loss of Small-Calibre Papillomacular Bundle Fibres

The leading explanation is curated here as mechanism rather than omitted: the unmyelinated prelaminar axon segment has a high per-unit-length conduction cost, mitochondria are distributed asymmetrically across the lamina cribrosa accordingly, and the earliest mitochondrial changes in pre-symptomatic Opa1+/- mice are found in exactly that segment. But the argument is not closed, and the gap is specific rather than a general plea for more research. First, the explanation is an energy-budget argument about a segment of axon, whereas the clinical selectivity is a claim about a fibre subpopulation — nothing yet connects smallest calibre to earliest failure quantitatively. Second, the same reasoning ought to predict disease in other high-demand unmyelinated neural compartments, and does not obviously do so. Third, the argument cannot be the whole story, because the identical anatomical substrate is shared with Leber hereditary optic neuropathy, which has a completely different natural history (subacute, sequentially bilateral, partial spontaneous recovery) from the same fibre population. Fourth, it does not explain the reduced penetrance: an anatomical vulnerability that every carrier shares cannot by itself account for 43-62% penetrance within a single family carrying one allele. A review of the human iPSC-RGC work states the gap plainly.

Not tagged HUMAN_MODEL_MISMATCH. The distinction matters: the mouse data do not conflict with the human disease, they simply do not reach the level of the claim. The open question is the mechanism itself, not the translational validity of a model that addresses it.

Show evidence (5 references)

PMID:35652445 SUPPORT Other

"the specific sensitivity of RGCs to OPA1 mutations, especially given the high levels of gene expression within other neuronal tissues, such as the brain and auditory neurons (10), remains unclear"

States that the retinal ganglion cell selectivity of OPA1 disease is unexplained despite high expression elsewhere, which is the gap recorded here. Evidence source is OTHER because this is an expert statement of what the field does not know rather than data.

PMID:35652445 SUPPORT Other

"the disease mechanisms driving RGC degeneration are poorly understood"

Independent statement in the same source that the mechanism of retinal ganglion cell degeneration is not settled. Evidence source is OTHER because this is an expert statement about the state of knowledge rather than data.

PMID:39659974 SUPPORT Model Organism

"Identifying the susceptibility of RGCs to such mutations in Opa1 or mitochondrial DNA is therefore essential to a fundamental understanding of these diseases."

The authors of the leading mechanistic study frame retinal ganglion cell susceptibility as still requiring explanation.

+ 2 more references

What determines whether a heterozygous OPA1 null allele carrier develops optic atrophy at all, given family-level penetrance as low as 43%?

KNOWLEDGE GAP OPEN reduced_penetrance_modifiers

Attached to

inheritance#Autosomal dominant pathophysiology#OPA1 Haploinsufficiency

Penetrance recalculated within two families carrying the recurrent c.2708_2711delTTAG allele was 43% and 62%, against a previously reported 98%. Because the allele is identical within each family, allele identity cannot explain the difference, and the original authors argued that if haploinsufficiency is the mechanism then reduced penetrance should not be allele-specific at all. The corollary is that something other than the OPA1 genotype sets the threshold — a modifier locus, mtDNA background, or an environmental or stochastic contribution to the bioenergetic margin — and this entry records no candidate because none was sourced. The practical consequence is already visible in ascertainment: OPA1 variants were found in 40% of apparently sporadic optic atrophy cases in a large referral series, so unaffected transmitting carriers are common.

One lead was checked and downgraded rather than adopted. A deep-research report offered mitochondrial haplogroup J as a penetrance modifier in this disease, citing PMID:16617242. Reading the source, the three-fold over-representation of haplogroup J is reported in OPA1-NEGATIVE patients, so it is evidence about the genetic architecture of OPA1-negative dominant optic atrophy and not about whether an OPA1 carrier manifests. The same paper's broader conclusion — that mtDNA background may influence expression in a subset of cases — is what is cited above, and it is a suggestion in a 29-patient haplotype comparison, not a demonstrated modifier effect. No cybrid or segregation experiment establishing causality was located.

Show evidence (3 references)

PMID:11440989 SUPPORT Human Clinical

"The mutation screening in this study also identified a number of asymptomatic individuals with OPA1 mutations."

Documents asymptomatic carriers, the observation that defines this gap.

PMID:19319978 SUPPORT Human Clinical

"OPA1 mutations were found in 157 (40%) of the 392 apparently sporadic cases of optic atrophy"

Shows the ascertainment consequence of reduced penetrance — a large share of OPA1 disease presents without a family history.

PMID:16617242 SUPPORT Human Clinical

"suggest that mtDNA genetic background may influence disease expression in a subset of cases"

The one sourced candidate modifier: the authors' conclusion that the inherited mtDNA background may modify expression. See this gap's notes for why the study's headline haplogroup result does not itself support an OPA1-penetrance modifier.

How much of the retinal ganglion cell deficit in classic autosomal dominant optic atrophy is a developmental failure that has already happened by the time vision is first measured, and how much is ongoing degeneration that a therapy started in adulthood could still prevent?

KNOWLEDGE GAP OPEN developmental_versus_degenerative_rgc_loss

Attached to

pathophysiology#Retinal Ganglion Cell Degeneration and Optic Nerve Atrophy pathophysiology#Selective Loss of Small-Calibre Papillomacular Bundle Fibres clinical_trials#NCT06970106

The entry models the disease as degeneration, because that is how the phenotype reads — insidious loss from the first decade, slow progression over decades. But OPA1 is required for mitochondrial fusion and cristae organization during development too, and a recent review states that the disease also involves a developmental component and draws the therapeutic consequence explicitly. The two accounts predict the same cross-sectional picture and different things about treatment: if a substantial share of the deficit is developmental, a therapy that restores OPA1 dosage in an adult retina cannot recover it, and the trials now recruiting — NCT06970106 doses adults intravitreally — would be testing prevention of future loss in patients who have already sustained most of theirs. Nothing located here partitions the deficit between the two. The experiment implied is conditional or inducible Opa1 knockdown at defined postnatal ages, which would separate a developmental from an adult-onset contribution; in humans the nearest approach is longitudinal structural imaging from the earliest age at which it can be obtained, and the same review notes early diagnosis is itself difficult.

Tagged KNOWLEDGE_GAP rather than HUMAN_MODEL_MISMATCH. The reviewer offered either. HUMAN_MODEL_MISMATCH would fit if a model system showed something whose translation to human biology were the open question, but here the open question is the timing of the deficit in the human disease itself, and no model result is in conflict with a human observation — the relevant human observation has not been made. The distinction CLAUDE.md draws is that KNOWLEDGE_GAP means the evidence is absent, which is the case.

Show evidence (2 references)

PMID:42101483 SUPPORT Other

"ADOA also involves a developmental component consistent with OPA1's essential role in mitochondrial fusion, cristae organization, and quality control."

States the developmental contribution that this gap asks to be quantified. Evidence source is OTHER because this is a review.

PMID:42101483 SUPPORT Other

"developmental RGC loss may limit therapeutic efficacy of late-stage interventions-a challenge compounded by the difficulty of early diagnosis"

States the therapeutic consequence that makes this gap consequential rather than academic. Evidence source is OTHER because this is a review, and note the author's own hedge — "may limit" — which is why this is a gap and not a curated mechanism. Quoted verbatim including the source's hyphen where a dash was intended.

Does stress-activated OMA1 cleavage of long OPA1 act as the amplifier that converts a tolerable 50% OPA1 dosage reduction into retinal ganglion cell loss, and does it explain why the same allele manifests in one carrier and not another?

KNOWLEDGE GAP OPEN oma1_stress_processing_switch_untested_in_doa

Attached to

pathophysiology#Impaired Mitochondrial Inner-Membrane Fusion pathophysiology#OPA1 Haploinsufficiency

Long OPA1 is constitutively cleaved by YME1L and OMA1 at two sites, and the balanced accumulation of long and short forms maintains fusion; under mitochondrial stress OMA1 converts OPA1 entirely to short isoforms, inhibiting fusion and triggering fragmentation. That is a switch, and a switch is the kind of thing that could turn a graded dosage deficit into a threshold event — which is what reduced penetrance and the decades-long latency of this disease both look like. It is recorded as a gap rather than as a pathophysiology node because nothing located here tests it in OPA1 haploinsufficient retinal ganglion cells, in patient tissue, or in an ADOA model: the supporting work is mouse embryonic fibroblast genetics on OPA1 processing generally, and it is unconnected to the disease. The experiment implied is OMA1 loss or inhibition in an Opa1+/- retina. Note the same source complicates the picture, since deleting Oma1 restored tubulation, cristae morphogenesis and apoptotic resistance in YME1L-null cells and long OPA1 alone sufficed for fusion — so processing is not required for fusion, and the switch is about quality control rather than about fusion capacity per se.

Sourced from a deep-research report lead and checked against the primary paper before recording. No claim is made that this mechanism operates in autosomal dominant optic atrophy; the gap exists because it has not been asked.

Show evidence (2 references)

PMID:24616225 SUPPORT In Vitro

"Stress-induced OPA1 processing by OMA1 converts OPA1 completely into short isoforms, inhibits fusion, and triggers mitochondrial fragmentation."

Describes the stress-gated proteolytic switch that this gap asks about.

PMID:24616225 SUPPORT In Vitro

"deletion of Oma1 restored mitochondrial tubulation, cristae morphogenesis, and apoptotic resistance in cells lacking YME1L"

The experimental result showing that removing OMA1 rescues cristae and apoptotic phenotypes, which is what makes OMA1 a candidate target — and also what shows the switch is not simply a fusion-capacity mechanism.

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Pathophysiology

OPA1 Haploinsufficiency

A heterozygous OPA1 null allele — premature termination codon, frameshift, splice-site defect, or large-scale rearrangement — halves the dose of functional OPA1 protein. This, rather than a poisoned oligomer, is the predominant mechanism of the classic non-syndromic form: the mutation spectrum is weighted towards truncating alleles, and a mouse carrying the recurrent human c.2708_2711delTTAG allele shows a greater than 40% reduction in Opa1 mRNA, which the authors read as supporting haploinsufficiency. Missense alleles in the GTPase domain, which act dominant-negatively, are instead enriched in the syndromic DOA plus form curated separately.

OPA1 hgnc:8140

Genetic context variant_origin: GERMLINE zygosity: HETEROZYGOUS functional_impact_category: LOSS_OF_FUNCTION

Heterozygous germline loss-of-function OPA1 alleles. Null alleles (nonsense, frameshift, splice, whole-gene deletion) predominate in the classic form.

Animal models

Opa1 delTTAG knock-in mouse Mouse recapitulates The knock-in allele reduces Opa1 transcript by more than 40% in cochlea, confirming that the recurrent human delTTAG allele acts by dosage reduction rather than by a dominant-negative product.

Downstream

Impaired Mitochondrial Inner-Membrane Fusion Reduced OPA1 dosage directly lowers the amount of the inner-membrane profusion dynamin available to drive fusion.

Cristae Disorganization OPA1 homo-oligomers structure the cristae; loss of half the protein disorganizes that architecture.

Impaired Mitochondrial DNA Maintenance The exon 4b-containing OPA1 isoforms tether mtDNA nucleoids to the inner membrane and promote replication, so reduced OPA1 impairs mtDNA copy number and distribution.

Loss of Cytochrome c Sequestration OPA1 oligomers hold cristae junctions tight and retain cytochrome c; reduced OPA1 lowers the threshold for its release.

Show evidence (5 references)

PMID:11440989 SUPPORT Human Clinical

"These are predominantly null mutations generating truncated proteins, strongly suggesting that the mechanism underlying DOA is haploinsufficiency."

Establishes haploinsufficiency from null alleles as the mechanism of the classic form, the basis of this node.

PMID:35652445 SUPPORT Other

"The majority of variants are thought to generate null alleles, causing premature termination codons (PTC) or loss of function variants that result in haploinsufficiency"

Independently states that most OPA1 variants are null alleles producing haploinsufficiency. Evidence source is OTHER because the sentence summarizes the field in this paper's introduction rather than reporting its own result.

PMID:38334784 SUPPORT Model Organism

"Molecular assessment of cochlea demonstrated a reduction of Opa1 mRNA level by greater than 40%, supporting haploinsufficiency as the disease mechanism."

Measures the reduction in Opa1 transcript in a knock-in mouse carrying the recurrent human delTTAG allele, corroborating the dosage mechanism (model-organism support, not the sole basis for the human claim).

+ 2 more references

Impaired Mitochondrial Inner-Membrane Fusion

OPA1 is a profusion dynamin-related protein of the mitochondrial inner membrane. Lowering it fragments the mitochondrial network and dissipates the inner-membrane potential. This is the canonical OPA1 function, and it is separable from the cristae-remodelling function below — genetic and molecular dissection places the two in distinct arms.

Retinal ganglion cell CL:0000740

Mitochondrial fusion GO:0008053 ↓ DECREASED Inner mitochondrial membrane organization GO:0007007 ⚠ ABNORMAL

Experimental models

Patient-derived primary skin fibroblasts with heterozygous OPA1 mutations PRIMARY CELL CULTURE Fusion was defective during pharmacological challenge with the protonophore CCCP, and fragmentation appeared under glycolysis shortage or exogenous oxidative stress.

Downstream

Oxidative Phosphorylation Deficiency Network fragmentation and loss of inner-membrane potential impair oxidative phosphorylation and ATP synthesis.

Show evidence (2 references)

PMID:12509422 SUPPORT In Vitro

"down-regulation of OPA1 in HeLa cells using specific small interfering RNA (siRNA) leads to fragmentation of the mitochondrial network concomitantly to the dissipation of the mitochondrial membrane potential"

Shows directly that reducing OPA1 fragments the mitochondrial network and collapses the membrane potential.

PMID:16839885 SUPPORT In Vitro

"Optic Atrophy 1 (OPA1), a profusion dynamin-related protein of the inner mitochondrial membrane mutated in dominant optic atrophy"

Identifies OPA1 as the inner-membrane profusion dynamin whose reduction this node describes.

Cristae Disorganization

OPA1 is a major organizer of the mitochondrial inner membrane; cristae integrity depends on it. Reducing OPA1 drastically disorganizes the cristae. Critically, this function is genetically and molecularly distinct from fusion — OPA1 keeps cristae junctions tight through oligomers of its soluble intermembrane-space and integral inner-membrane forms, and does so independently of its profusion activity. Curating it as its own node rather than folding it into the fusion node is the point: a cristae defect alone is sufficient to compromise respiratory-complex organization and cytochrome c retention.

Cristae formation GO:0042407 ↓ DECREASED

Experimental models

Patient-derived primary skin fibroblasts with heterozygous OPA1 mutations PRIMARY CELL CULTURE Altered cristae structure is present in patient fibroblasts carrying heterozygous OPA1 mutations.

Downstream

Oxidative Phosphorylation Deficiency Deranged cristae architecture destabilizes respiratory-chain complex organization and lowers oxidative phosphorylation efficiency.

Loss of Cytochrome c Sequestration Widening of cristae junctions releases the cytochrome c pool held within the cristae lumen.

Show evidence (2 references)

PMID:12509422 SUPPORT In Vitro

"OPA1 is a major organizer of the mitochondrial inner membrane from which the maintenance of the cristae integrity depends"

Establishes cristae integrity as dependent on OPA1, the claim of this node.

PMID:16839885 SUPPORT In Vitro

"Thus, OPA1 has genetically and molecularly distinct functions in mitochondrial fusion and in cristae remodeling during apoptosis."

The source of the separability claim that justifies modelling cristae remodelling as a node distinct from fusion.

Impaired Mitochondrial DNA Maintenance

OPA1 is a direct actor in maintenance of the mitochondrial genome, not only a shaper of membranes. Silencing the OPA1 variants that include the alternately spliced exon 4b depletes mtDNA by inhibiting replication and disorganizes the distribution of nucleoids through the network; a small hydrophobic peptide cleaved from the exon 4b isoform is embedded in the inner membrane and co-immunoprecipitates with nucleoid components. The consequence in classic DOA is reduced mtDNA copy number and mislocalized nucleoids — which is a different claim from the secondary multiple mtDNA deletions and COX-negative muscle fibres that characterize DOA plus, where a dominant-negative allele destabilizes the genome more severely.

Mitochondrial DNA replication GO:0006264 ↓ DECREASED Mitochondrial DNA maintenance GO:0032042 ⚠ ABNORMAL

Experimental models

OPA1 patient-derived and isogenic OPA1-null iPSC-derived retinal ganglion cells IPSC DERIVED MODEL The same lines show compromised mitochondrial DNA maintenance.

Downstream

Oxidative Phosphorylation Deficiency Reduced mtDNA copy number limits the supply of mtDNA-encoded respiratory-chain subunits.

Show evidence (3 references)

PMID:20974897 SUPPORT In Vitro

"silencing of the OPA1 variants including exon 4b leads to mtDNA depletion, secondary to inhibition of mtDNA replication, and to marked alteration of mtDNA distribution in nucleoid and nucleoid distribution throughout the mitochondrial network"

Directly demonstrates the mtDNA replication and nucleoid-distribution defect that defines this node.

PMID:20974897 SUPPORT In Vitro

"this study places OPA1 as a direct actor in the maintenance of mitochondrial genome integrity"

Supports treating mtDNA maintenance as a function of OPA1 in its own right rather than a downstream consequence of the fusion defect.

PMID:35652445 SUPPORT In Vitro

"OPA1+/- and OPA1 variant iPSC-RGCs exhibited impaired mitochondrial homeostasis, with reduced bioenergetic output and compromised mitochondrial DNA maintenance."

Shows the mtDNA-maintenance defect in the disease-relevant cell type, human iPSC-derived retinal ganglion cells carrying OPA1 null and patient alleles.

Loss of Cytochrome c Sequestration

OPA1 oligomers keep cristae junctions tight during apoptosis and so retain the intracristal cytochrome c pool. This is a protective function exerted independently of fusion: OPA1 does not interfere with activation of BAX and BAK, but the proapoptotic BH3 protein BID, which widens cristae junctions, disrupts OPA1 oligomers. Losing it lowers the threshold for cytochrome c release, and in cultured cells reducing OPA1 commits the cell to apoptosis with no other stimulus applied.

Release of cytochrome c from mitochondria GO:0001836 ↑ INCREASED

Downstream

Retinal Ganglion Cell Degeneration and Optic Nerve Atrophy A lowered apoptotic threshold converts a chronic bioenergetic deficit into retinal ganglion cell death.

Show evidence (2 references)

PMID:16839885 SUPPORT In Vitro

"it controls the shape of mitochondrial cristae, keeping their junctions tight during apoptosis"

Identifies the cristae-junction-tightening mechanism by which OPA1 sequesters cytochrome c.

PMID:12509422 SUPPORT In Vitro

"As loss of OPA1 commits cells to apoptosis without any other stimulus, we propose that OPA1 is involved in the cytochrome c sequestration"

Shows that OPA1 loss alone is sufficient to trigger the apoptotic program, supporting a lowered apoptotic threshold.

Oxidative Phosphorylation Deficiency

The four upstream arms converge here. Defective fusion and cristae derangement together yield defective oxidative phosphorylation with reduced ATP synthesis driven by complex I substrates, and the mtDNA defect limits the supply of respiratory-chain subunits. The deficit is measurable in the disease-relevant cell type: human iPSC-derived retinal ganglion cells carrying OPA1 null or patient alleles show reduced bioenergetic output. This node is the point of conformance with the mitochondrial_dysfunction module, where it plays the central-effector role that disease-specific mitochondrial lesions converge upon.

Oxidative phosphorylation GO:0006119 ↓ DECREASED ATP biosynthetic process GO:0006754 ↓ DECREASED Reactive oxygen species metabolism GO:0072593 ↑ INCREASED

Experimental models

OPA1 patient-derived and isogenic OPA1-null iPSC-derived retinal ganglion cells IPSC DERIVED MODEL OPA1+/- and OPA1-variant iPSC-RGCs show reduced bioenergetic output.

Downstream

Energetic Vulnerability of the Unmyelinated Prelaminar Axon A ubiquitous ATP shortfall is first exposed where the per-unit-length energy cost of conduction is highest.

Show evidence (5 references)

PMID:32243103 SUPPORT Other

"OPA1‐linked DOA is characterized by defective mitochondrial fusion and cristae derangement, which in turn lead to defective oxidative phosphorylation with reduced ATP synthesis driven by complex I substrates"

States the convergence of the fusion and cristae arms on an oxidative phosphorylation and ATP-synthesis deficit. Evidence source is OTHER under the rule this entry applies throughout, which was tightened in review round 1. evidence_source classifies the evidence the cited publication presents; an introduction restating established consensus presents no evidence of its own, so it is graded OTHER regardless of what kind of study the paper is. Each paper's own results keep the grade matching its design, which is why PMID:35652445 and PMID:38334784 appear in this entry under OTHER for their background prose and under IN_VITRO and MODEL_ORGANISM for their experiments. This also makes the entry internally consistent with the review citations PMID:11850115 and PMID:21112411, which were already OTHER.

PMID:35652445 SUPPORT In Vitro

"reduced bioenergetic output and compromised mitochondrial DNA maintenance"

Measures reduced bioenergetic output in OPA1-null and OPA1-variant human iPSC-derived retinal ganglion cells.

PMID:22800932 SUPPORT In Vitro

"Respiratory complex IV activity and subunits steady-state were decreased without alteration of the mitochondrial deoxyribonucleic acid size, amount or transcription."

Measures a specific respiratory-chain deficit (complex IV) in primary fibroblasts from patients with heterozygous OPA1 mutations, and reports a physical OPA1-oxidative-phosphorylation interaction by reciprocal immunoprecipitation.

+ 2 more references

Energetic Vulnerability of the Unmyelinated Prelaminar Axon

This node carries the selectivity argument, and it is a claim about the target tissue rather than about the lesion. Retinal ganglion cell axons are unmyelinated from the cell body until they cross the lamina cribrosa, so conduction there is non-saltatory and costly; after the lamina they are myelinated and propagate saltatorily at much lower cost. Mitochondria are distributed accordingly, densely in the prelaminar nerve and sparsely behind it. In pre-symptomatic Opa1+/- mice, mitochondrial fragmentation and increased mitophagy are found mainly in that unmyelinated segment, before any neuronal loss — identifying it as the specific point of vulnerability. The asymmetric myelination pattern and an associated impairment of mitochondrial axonal transport were proposed as the common explanation for this pattern across the mitochondrial optic neuropathies well before the mouse data.

Retinal ganglion cell CL:0000740

Axonal transport of mitochondrion GO:0019896 ⚠ ABNORMAL

optic nerve UBERON:0000941

Animal models

Opa1 delTTAG knock-in mouse Mouse recapitulates Pre-symptomatic Opa1+/- mice show mitochondrial fragmentation and increased mitophagy concentrated in the unmyelinated portion of retinal ganglion cell axons, before any neuronal loss.

Downstream

Selective Loss of Small-Calibre Papillomacular Bundle Fibres Within the vulnerable prelaminar population, the fibres with the least favourable surface-to-volume and mitochondrial reserve fail first.

Show evidence (3 references)

PMID:39659974 SUPPORT Model Organism

"These pre-symptomatic mitochondrial changes were mainly observed in the unmyelinated portion of the retinal ganglion cell axons, where the transmission of the visual information requires high energy expenditure, constituting the specific point of vulnerability in hereditary optic neuropathies."

Localizes the earliest mitochondrial abnormality in an Opa1+/- mouse to the unmyelinated prelaminar axon segment and names it the point of vulnerability. Model-organism evidence; the human correlate is the clinical pattern of fibre loss curated in the next node.

PMID:39659974 SUPPORT Model Organism

"since RGC axons are not myelinated in the eye, high energy expenditure is required to ensure optimal non-saltatory transduction of action potentials"

States the anatomical and biophysical basis of the energy asymmetry this node depends on.

PMID:11850115 SUPPORT Other

"Anatomical peculiarities of optic nerve axons, such as the asymmetric pattern of myelination, may have functional implications on energy dependence and distribution of mitochondrial populations in the different sections of the nerve."

The earlier statement of the asymmetric-myelination explanation, proposed as a shared mechanism across the mitochondrial optic neuropathies. Evidence source is OTHER because it is a review.

Selective Loss of Small-Calibre Papillomacular Bundle Fibres

Degeneration is not uniform across the retinal ganglion cell population. The smallest-calibre fibres, which make up the papillomacular bundle serving central vision, are affected first and most severely. That topography explains the clinical triad directly: temporal pallor of the optic disc, a central or centrocecal field defect, and early loss of central acuity and colour discrimination. The same pattern recurs across a large number of optic neuropathies of mitochondrial origin, including Leber hereditary optic neuropathy and the toxic and nutritional optic neuropathies, which is why it is modelled here as a property of the fibre population rather than as something specific to OPA1.

Retinal ganglion cell CL:0000740

nerve fiber layer of retina UBERON:0001793 optic disc UBERON:0001783

Downstream

Retinal Ganglion Cell Degeneration and Optic Nerve Atrophy Cumulative loss of the small central fibres is the substrate of the optic nerve atrophy.

Optic disc pallor Loss of the temporally entering papillomacular fibres produces temporal, and later diffuse, disc pallor.

Centrocecal scotoma The papillomacular bundle subserves the central field, so its loss produces a centrocecal or central scotoma.

Acquired blue-yellow dyschromatopsia Loss of the central fibre population degrades colour discrimination, classically in a blue-yellow (tritan) pattern.

Abnormal retinal nerve fiber layer morphology Fibre loss thins the peripapillary retinal nerve fibre layer and the macular ganglion cell-inner plexiform layer on optical coherence tomography.

Show evidence (3 references)

PMID:11850115 SUPPORT Other

"Selective degeneration of the smallest fibers (papillo-macular bundle) of the human optic nerve occurs in a large number of optic neuropathies characterized primarily by loss of central vision."

Establishes the small-fibre, papillomacular topography of degeneration in the human optic nerve. Evidence source is OTHER because it is a review.

PMID:32243103 SUPPORT Other

"the small axons of the papillomacular bundle are affected first and more severely, leading to the temporal pallor of the optic disc at fundus examination, central scotoma at visual fields and loss of central vision with a consistent drop in visual acuity"

Connects the small-axon papillomacular topography to each of the three clinical findings this node is upstream of. Evidence source is OTHER because the statement is review-style framing rather than the cohort study's own result.

PMID:35652445 SUPPORT Other

"bilateral central scotomas and optic disc pallor caused by the loss of RGCs within the papillomacular bundle"

Independently attributes the central scotoma and disc pallor of DOA to papillomacular bundle RGC loss. Evidence source is OTHER because this is introductory clinical background rather than a finding of the iPSC study.

Retinal Ganglion Cell Degeneration and Optic Nerve Atrophy

The end state of the mechanism: progressive, selective loss of retinal ganglion cells and their axons, with consequent optic nerve degeneration. DOA was described from the outset as a non-syndromic loss of visual acuity of insidious onset in early childhood caused by progressive and selective retinal ganglion cell loss, and that selectivity — rather than any systemic mitochondrial failure — is what defines the classic form.

Retinal ganglion cell CL:0000740

Neuron apoptotic process GO:0051402 ↑ INCREASED

optic nerve UBERON:0000941

Downstream

Optic atrophy Retinal ganglion cell and axonal loss is seen clinically as bilateral optic atrophy.

Reduced visual acuity Loss of central fibres reduces visual acuity.

Progressive visual loss Continued fibre loss produces slow progression of visual impairment over decades.

Abnormality of visual evoked potentials Loss and dysfunction of conducting retinal ganglion cell axons delays or abolishes the cortical visual evoked response.

Show evidence (2 references)

PMID:38334784 SUPPORT Other

"DOA has been initially described as a non-syndromic moderate to severe loss of visual acuity with an insidious onset in early childhood, caused by a progressive and selective loss of retinal ganglion cells"

States the defining clinical-pathological claim of the classic form. Evidence source is OTHER because the sentence is the paper's introductory restatement of the established clinical description rather than its own mouse experiment or an observation it made on patients.

PMID:20417570 SUPPORT Human Clinical

"the primary pathological process selectively targets retinal ganglion cells (RGCs) resulting in optic nerve degeneration"

Independently states selective retinal ganglion cell targeting with resulting optic nerve degeneration.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

Optic atrophy Phenotypic abnormality HP:0000648

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:20301426 SUPPORT Human Clinical

"Optic atrophy type 1 (OPA1, or Kjer type optic atrophy) is characterized by bilateral and symmetric optic nerve pallor"

Describes the bilateral symmetric optic nerve pallor defining the entity. Cited from a GeneReviews chapter that has since been retired; see the entry-level references note.

Optic disc pallor Phenotypic abnormality HP:0000543

Show evidence (1 reference)

PMID:20301426 SUPPORT Human Clinical

"Ophthalmoscopic examination discloses temporal or diffuse pallor of the optic discs, sometimes associated with optic disc excavation."

Documents the temporal or diffuse disc pallor and associated excavation.

Reduced visual acuity Phenotypic abnormality HP:0007663

Show evidence (2 references)

PMID:20301426 SUPPORT Human Clinical

"insidious decrease in visual acuity (usually between ages 4 and 6 years)"

Source for the insidious onset in the first decade.

PMID:20417570 SUPPORT Human Clinical

"Snellen visual acuity varied markedly between OPA1-positive cases with a mean of 20/173 (range 20/20 to hand movements)"

Quantifies acuity and its spread in a molecularly confirmed OPA1 cohort.

Progressive visual loss Phenotypic abnormality HP:0000529

Course: PROGRESSIVE

The two evidence items here disagree and are both kept. A single population-based cohort found visual function worsening in 67.4% of patients at 0.032 logMAR/year (PMID:20417570); a later meta-analysis pooling seven studies found 0.022 logMAR/year with a confidence interval crossing zero (PMID:40329928). The point estimates are close, so the disagreement is about statistical power and the insensitivity of Snellen acuity over short follow-up, not about the direction of change. Structural measures (peripapillary retinal nerve fibre layer, macular ganglion cell-inner plexiform layer) are the candidates for a sensitive endpoint, but the meta-analysis found no longitudinal data for them to pool.

Show evidence (3 references)

PMID:20417570 SUPPORT Human Clinical

"visual function worsened in 67.4% of patients during follow-up"

Quantifies the proportion progressing in longitudinal follow-up.

PMID:20417570 SUPPORT Human Clinical

"The mean rate of visual loss was 0.032 logarithm of the minimum angle of resolution per year, but some patients experienced faster visual decline (range = 0-0.171 logarithm of the minimum angle of resolution/year)"

Gives the rate of progression and its variability.

PMID:40329928 REFUTE Human Clinical

"the rate of yearly visual acuity decline (0.022 LogMAR/year., 95% CI: -0.008 to 0.052) was not significantly different from zero (Z = 1.4, p = 0.155)"

Pooling the longitudinal literature, visual acuity decline in DOA is not statistically distinguishable from no decline. This cuts against progression as a measurable property of visual acuity rather than against progression of the disease, and the distinction matters for trial design — the same review reports visual acuity as the only biomarker with any longitudinal data at all. It is recorded as REFUTE because it contradicts the claim this phenotype makes as stated, not because the disease is thought to be static.

Centrocecal scotoma Phenotypic abnormality HP:0000576

Show evidence (1 reference)

PMID:20301426 SUPPORT Human Clinical

"The visual field defect is typically centrocecal, central, or paracentral; it is often large in those with severe disease."

Documents the centrocecal/central field defect and its relation to severity.

Acquired blue-yellow dyschromatopsia Phenotypic abnormality HP:0007641

Show evidence (2 references)

PMID:20301426 SUPPORT Human Clinical

"The color vision defect is often described as acquired blue-yellow loss (tritanopia)."

Source for the acquired blue-yellow character of the colour defect.

PMID:20301426 SUPPORT Human Clinical

"Tritanopia is the classic feature of color vision defect, but more diffuse nonspecific dyschromatopsia is not uncommon."

Supports recording the defect at the general Dyschromatopsia level while noting the classic tritan pattern.

Abnormality of visual evoked potentials Phenotypic abnormality HP:0000649

Show evidence (1 reference)

PMID:20301426 SUPPORT Human Clinical

"Visual evoked potentials are typically absent or delayed"

Documents the visual evoked potential abnormality.

Abnormal electroretinogram Phenotypic abnormality HP:0000512

Show evidence (1 reference)

PMID:20301426 SUPPORT Human Clinical

"pattern electroretinogram shows an abnormal N95:P50 ratio"

Documents the pattern ERG abnormality localizing dysfunction to the retinal ganglion cells.

Abnormal retinal nerve fiber layer morphology Phenotypic abnormality HP:0020119

Show evidence (1 reference)

PMID:30649972 SUPPORT Human Clinical

"In chronic LHON and DOA, both the pRNFL and RGC-IPL were significantly thinner in all four retinal quadrants relative to controls."

Documents the quantitative OCT thinning of the retinal nerve fibre layer and ganglion cell complex in DOA.

🧬

Genetic Associations

OPA1 (Causative)

Gene: OPA1 hgnc:8140 relationship_type: CAUSATIVE variant_origin: GERMLINE

Autosomal dominant

Show evidence (6 references)

PMID:11017079 SUPPORT Human Clinical

"We describe here a nuclear gene, OPA1, that maps within the candidate region and encodes a dynamin-related protein localized to mitochondria."

The original identification of OPA1 as the gene for optic atrophy type 1.

PMID:11017079 SUPPORT Human Clinical

"We found four different OPA1 mutations, including frameshift and missense mutations, to segregate with the disease, demonstrating a role for mitochondria in retinal ganglion cell pathophysiology."

Establishes cosegregation of OPA1 variants with the disease and the mitochondrial basis of retinal ganglion cell pathology.

PMID:20417570 SUPPORT Human Clinical

"The detection rate of OPA1 mutations was 57.6% among probands with a positive family history of optic atrophy (19/33) and 14.0% among singleton cases (6/43)."

Quantifies the family-history dependence of the OPA1 detection rate.

+ 3 more references

💊

Medical Actions

Idebenone

Action: Pharmacotherapy NCIT:C15986

Agent: idebenone CHEBI:31687

Platform: Small molecule

Off-label idebenone, a short-chain quinone used as an alternative electron carrier, has been given to OPA1-DOA patients on the rationale shared with Leber hereditary optic neuropathy. In a cohort study comparing treated with untreated patients, treatment was associated with stabilization or recovery of visual acuity, and the association survived adjustment for confounders. This is observational, not a randomized result, and it is the strongest pharmacological evidence located for this disease.

Mechanism Target:

Oxidative Phosphorylation Deficiency — Idebenone is used as an alternative electron carrier intended to bypass the respiratory-chain deficit downstream of the OPA1 lesion.

Target Phenotypes: Reduced visual acuity HP:0007663

Show evidence (3 references)

PMID:32243103 SUPPORT Human Clinical

"We found a significant difference between the last visit and baseline VA in favor of stabilization/recovery in idebenone-treated as compared to untreated patients. This effect was retained after controlling for confounders."

The cohort result supporting a visual-acuity benefit, with the observational design stated in the treatment description.

PMID:26820596 REFUTE Model Organism

"Idebenone appears largely ineffective in protecting Opa1 heterozygous RGCs from dendropathy."

The randomized, placebo-controlled test of this treatment in an Opa1 mutant mouse found it largely ineffective at the cellular endpoint. It is the only randomized evidence on idebenone in this disease in either species, and it cuts against the human cohort association above.

PMID:26820596 REFUTE Model Organism

"in the liver there was an 80.35% (p=0.011) increase in oxidative damage"

A harm signal rather than an efficacy failure, and recorded because it is the opposite of the drug's intended antioxidant effect. The same trial also found visual function impaired in idebenone-treated wildtype mice, which the authors say had not been observed before and raises concerns.

Low-Vision Rehabilitation and Visual Aids

Action: low-vision rehabilitation Ontology label: Rehabilitation NCIT:C15315

Platform: Behavioral / lifestyle

Low-vision aids for decreased visual acuity, with annual ophthalmologic evaluation including visual acuity, visual fields, and optical coherence tomography. This is the mainstay of management, since no disease-modifying therapy is licensed.

Show evidence (2 references)

PMID:20301426 SUPPORT Human Clinical

"Treatment of manifestations: Low-vision aids for decreased visual acuity."

Source for low-vision aids as the recommended management of the visual deficit.

PMID:20301426 SUPPORT Human Clinical

"Surveillance: Annual ophthalmologic evaluations (including measurement of visual acuity, visual fields, and optical coherence tomography) and hearing evaluations."

Source for the annual surveillance schedule asserted in this treatment's description — visual acuity, visual fields, optical coherence tomography, and hearing evaluation.

Avoidance of Mitochondrial Toxins

Action: avoidance of mitochondrial toxins and mitochondriotoxic medication Ontology label: Supportive Care NCIT:C15747

Platform: Behavioral / lifestyle

Carriers are advised to avoid smoking, excessive alcohol intake, and medications — antibiotics and antivirals are the examples given — that interfere with mitochondrial metabolism. This is curated as a management action, which is what the source files it as, and not as an environmental causal edge: "clinicians advise avoiding X" is a weaker and differently grounded claim than "X causes retinal ganglion cell loss in this disease", and no source was located that quantifies an exposure effect in OPA1-related optic atrophy. The rationale is plausible and unmeasured — these exposures are mitochondrial stressors acting on a cell population already at a bioenergetic margin — and the advice is cheap, which is presumably why it is given.

Show evidence (1 reference)

PMID:20301426 SUPPORT Human Clinical

"Agents/circumstances to avoid: Smoking, excessive alcohol intake, medications (antibiotics, antivirals) that interfere with mitochondrial metabolism."

Source for the specific agents and circumstances carriers are advised to avoid, filed under management in the cited chapter.

Genetic Counseling

Action: Genetic Counseling NCIT:C15240

Autosomal dominant transmission with a 50% recurrence risk per child, but counselling is complicated by incomplete penetrance and by markedly variable inter- and intrafamilial expressivity, so an at-risk relative cannot be given a reliable severity prediction from the genotype alone.

Show evidence (1 reference)

PMID:20301426 SUPPORT Human Clinical

"genetic counseling remains complicated by the incomplete penetrance and the markedly variable inter- and intrafamilial expressivity of the disease."

Source for the counselling difficulty created by reduced penetrance and variable expressivity.

🔬

Diagnosis

OPA1 Molecular Genetic Testing

The diagnosis rests on a combination of clinical findings, electrophysiologic studies and family history, and/or on identifying a heterozygous pathogenic OPA1 variant by molecular genetic testing. Two practical points follow from the cohort data curated in the genetic block: the detection rate depends strongly on family history (57.6% in probands with an affected relative versus 14.0% in singletons), and sequencing alone misses large-scale rearrangements, so an OPA1-negative result after coding sequencing is not a negative OPA1 result.

OPA1 molecular genetic testing NCIT:C15709

Results: Heterozygous pathogenic OPA1 variant

Bound to the general NCIT Genetic Testing action. NCIT:C153598 DNA Sequencing would name the technique but not the clinical act, and there is no NCIT clinical-action term for OPA1 testing specifically, so the specificity is carried in preferred_term per the Ontology Term Contract.

Show evidence (2 references)

PMID:20301426 SUPPORT Human Clinical

"The diagnosis of OPA1 is made based on a combination of clinical findings, electrophysiologic studies, and family history and/or by the identification of a heterozygous pathogenic variant in OPA1, the only gene known to be associated with OPA1, by molecular genetic testing."

States the diagnostic basis of the entity and that OPA1 is the only gene known to be associated with it.

PMID:20417570 SUPPORT Human Clinical

"OPA1-negative cases were then screened for large-scale OPA1 rearrangements and OPA3 mutations."

Documents the second-tier rearrangement screen that a coding-sequence-only strategy would miss.

Optical Coherence Tomography of the Retinal Ganglion Cell Complex

Optical coherence tomography quantifies the structural loss, showing thinning of both the peripapillary retinal nerve fibre layer and the macular ganglion cell-inner plexiform layer. It is the candidate objective endpoint for trials, although the meta-analysis of longitudinal biomarkers found no pooled longitudinal data for it — visual acuity was the only biomarker with any. See the Progressive visual loss phenotype for that tension.

optical coherence tomography of the retinal ganglion cell complex NCIT:C20828

Markers: Peripapillary retinal nerve fibre layer thickness; macular ganglion cell-inner plexiform layer thickness

Show evidence (2 references)

PMID:30649972 SUPPORT Human Clinical

"This study suggests the usefulness of the RGCC as a potential in vivo biomarker for assessing disease in patients with LHON and DOA."

Supports the retinal ganglion cell complex on OCT as an in vivo biomarker in this disease.

PMID:20301426 SUPPORT Human Clinical

"Surveillance: Annual ophthalmologic evaluations (including measurement of visual acuity, visual fields, and optical coherence tomography) and hearing evaluations."

Places optical coherence tomography within the recommended surveillance schedule alongside visual acuity and visual fields.

📊

Prevalence

North of England

Point Prevalence 2.87 per 100,000 (2.54–3.2) 1–9 per 100,000

Population-based ascertainment of clinically diagnosed DOA; the authors express the same figure as at least 1 in 35,000 of the general population. Restricting to molecularly confirmed OPA1-positive cases lowers it to 2.09 per 100,000 (95% CI 1.95-2.23), so this record is the clinical-diagnosis denominator and is an explicit minimum.

Show evidence (1 reference)

PMID:20417570 SUPPORT Human Clinical

"The minimum point prevalence of DOA in the north of England was 2.87 per 100,000 (95% confidence interval [CI], 2.54-3.20)"

Reports the population-based minimum point prevalence curated in this record.

Worldwide

Point Prevalence 4.0 per 100,000 1–9 per 100,000

Estimated minimum prevalence of 1 in 25,000 quoted in a 2022 review; normalized as 100000/25000 = 4.0 per 100,000. Note this is a review's summary figure rather than a fresh ascertainment, and it disagrees with the older 1 in 50,000 figure given when OPA1 was identified (PMID:11017079) and with the 1 in 20,000 quoted elsewhere — the spread reflects ascertainment, not a change in the disease.

Show evidence (1 reference)

PMID:35652445 SUPPORT Other

"Autosomal dominant optic atrophy (DOA) is the most common ION, with an estimated minimum prevalence of 1 in 25 000"

Source for the 1 in 25,000 minimum-prevalence figure normalized in this record. Evidence source is OTHER because the sentence is background prose in the paper's introduction restating a consensus figure rather than a measurement this paper made.

🔀

Differential Diagnoses

Conditions with similar clinical presentations that must be differentiated from Autosomal Dominant Optic Atrophy:

Autosomal Dominant Optic Atrophy Plus

Overlapping Features The syndromic form of the same gene's disease, curated separately at MONDO:0014720. It shares the optic neuropathy but adds sensorineural deafness, chronic progressive external ophthalmoplegia, myopathy, ataxia and peripheral neuropathy, and is enriched for dominant-negative missense alleles in the GTPase domain with secondary multiple mtDNA deletions and COX-negative muscle fibres. The boundary is clinical rather than genetic and is not sharp: extra-ocular features affect up to about 20% of OPA1 carriers, and subclinical auditory neuropathy is detectable in carriers who are otherwise non-syndromic.

Leber Hereditary Optic Neuropathy

Overlapping Features The other common mitochondrial optic neuropathy, and the most important differential. It shares the papillomacular small-fibre topography and the final common pathway of retinal ganglion cell loss, but is maternally inherited through mtDNA complex I subunit variants, and is subacute and sequentially bilateral rather than insidious and congenital-to-infantile in onset. The two are genetically distinct: screening 28 LHON patients who were negative for the three primary mtDNA variants found no OPA1 mutations.

🔬

Clinical Trials

NCT06007391 PHASE_II ACTIVE_NOT_RECRUITING

Pilot study of the tolerance and efficacy of nicotinamide (vitamin B3) in DOA and DOA plus, on the rationale that plasma metabolomics in DOA shows a relative nicotinamide deficiency and that nicotinamide is neuroprotective for the optic nerve. Registered as phase 2/phase 3; recorded here as PHASE_II because the enum is single-valued and the registration describes a pilot tolerance-and-efficacy study.

Target Phenotypes: Reduced visual acuity HP:0007663

Show evidence (1 reference)

clinicaltrials:NCT06007391 SUPPORT Other

"The objective of this pilot study is to test the tolerance and efficacy of nicotinamide in DOA and DOA+ patients."

Registration record establishing the trial's objective and population. Graded OTHER because a registration is a protocol document, not study evidence.

NCT06970106 PHASE_I RECRUITING

Phase 1b open-label, randomized single- and repeat-dose study of intravitreally administered PYC-001 in participants with confirmed OPA1-mutation-associated DOA, enrolling roughly 18 participants across Australia, New Zealand and other APAC countries. Recorded as PHASE_I because the registration describes it as phase 1b. No treatments entry is created for PYC-001: the registration gives the route and dose schedule but not the molecular mechanism, and asserting a therapeutic_modality would mean supplying the drug class from memory.

Show evidence (1 reference)

clinicaltrials:NCT06970106 SUPPORT Other

"This study aims to gather safety data and determine the optimal dosing regimen for PYC-001 in participants with confirmed OPA1 mutation-associated ADOA."

Registration record establishing the trial's objective and population. Graded OTHER because a registration is a protocol document, not study evidence.

🧫

Experimental Models

OPA1 patient-derived and isogenic OPA1-null iPSC-derived retinal ganglion cells IPSC_DERIVED_MODEL

Human induced pluripotent stem cells comprising an isogenic heterozygous OPA1-null line made by CRISPR/Cas9 editing of a control, a patient line carrying the recurrent c.2708_2711delTTAG null allele, a DOA plus patient line carrying the c.1334G>A (p.R445H) missense allele, and CRISPR-corrected controls, differentiated in two dimensions to retinal ganglion cells. This is the disease-relevant human cell type, and the line panel is the reason it matters here: it puts a classic-form null allele and a plus-form missense allele in the same dish, which is the comparison the lump/split argument turns on.

Organism

human NCBITaxon:9606

Culture

Two-dimensional directed differentiation to retinal ganglion cells

Publication

PMID:35652445

Pathograph links

Oxidative Phosphorylation Deficiency recapitulates fidelity: moderate observes: cellular OPA1+/- and OPA1-variant iPSC-RGCs show reduced bioenergetic output.

Limitations: iPSC-derived retinal ganglion cells in two-dimensional culture have no unmyelinated prelaminar axon segment, no lamina cribrosa, and no long-range axonal compartment, so the system can report the bioenergetic deficit but structurally cannot test the selectivity mechanism this entry proposes. Differentiation was unimpaired in all mutant lines, so the model captures a functional deficit in surviving cells rather than cell loss.

Readouts

Mitochondrial bioenergetic output

Direction: DECREASED

Interpretation: Reduced bioenergetic output in mutant iPSC-RGCs relative to isogenic and corrected controls.

Show evidence (1 reference)

PMID:35652445 SUPPORT In Vitro

"OPA1+/- and OPA1 variant iPSC-RGCs exhibited impaired mitochondrial homeostasis, with reduced bioenergetic output"

Reports the bioenergetic measurement behind this readout.

Impaired Mitochondrial DNA Maintenance recapitulates fidelity: moderate observes: molecular The same lines show compromised mitochondrial DNA maintenance.

Limitations: The abstract reports compromised mtDNA maintenance without separating copy number from deletion burden, so it does not by itself distinguish the classic-form mtDNA phenotype from the DOA-plus one.

Show evidence (1 reference)

PMID:35652445 SUPPORT In Vitro

"OPA1+/- and OPA1 variant iPSC-RGCs exhibited impaired mitochondrial homeostasis, with reduced bioenergetic output and compromised mitochondrial DNA maintenance."

Supports this model as informative for the mtDNA-maintenance node.

Show evidence (1 reference)

PMID:35652445 SUPPORT In Vitro

"we describe the generation of isogenic, heterozygous OPA1 null induced pluripotent stem cell (iPSC) (OPA1+/-) through clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene editing of a control cell line"

Establishes the isogenic design that makes this model informative.

Patient-derived primary skin fibroblasts with heterozygous OPA1 mutations PRIMARY_CELL_CULTURE

Four primary skin fibroblast lines carrying different heterozygous OPA1 mutations — nonsense and missense, in the GTPase and the C-terminal coiled-coil domains — analysed in parallel and quantitatively, which was the point of the study: earlier fibroblast reports had been mutually inconsistent. The panel shows defective fusion on pharmacological challenge, abnormal fragmentation under glycolysis shortage or oxidative stress, reduced complex IV activity, and distorted cristae, with a physical OPA1-oxidative-phosphorylation interaction on reciprocal immunoprecipitation. It is the human in vitro counterweight to the study of isolated patient mitochondria that found electron transport unaltered.

Organism

human NCBITaxon:9606

Publication

PMID:22800932

Pathograph links

Cristae Disorganization recapitulates fidelity: moderate observes: cellular Altered cristae structure is present in patient fibroblasts carrying heterozygous OPA1 mutations.

Limitations: Skin fibroblasts are not the affected cell type, and the paper says so itself: whether these alterations are present in retinal ganglion cells, and which of them drives degeneration, is left as an open goal. The fusion defect also required pharmacological challenge to become apparent, so the unstressed phenotype is mild.

Show evidence (1 reference)

PMID:22800932 SUPPORT In Vitro

"Altered cristae structure coexisted with normal response to pro-apoptotic stimuli and expression of Bax or Bcl2 proteins."

Documents the cristae abnormality in patient cells, and in the same sentence the absence of an apoptotic-response abnormality — relevant because it does not reproduce the lowered apoptotic threshold that cultured OPA1-knockdown cells show.

Impaired Mitochondrial Inner-Membrane Fusion partially recapitulates fidelity: moderate observes: cellular Fusion was defective during pharmacological challenge with the protonophore CCCP, and fragmentation appeared under glycolysis shortage or exogenous oxidative stress.

Limitations: The fusion defect is conditional on a stressor rather than constitutive, and baseline mitochondria were significantly elongated rather than fragmented, so the phenotype is not a simple loss of fusion.

Show evidence (1 reference)

PMID:22800932 SUPPORT In Vitro

"defective mitochondrial fusion during pharmacological challenge with the protonophore carbonyl cyanide m-chlorophenyl hydrazone, significant mitochondrial elongation with decreased OPA1 and DRP1 proteins, and abnormal mitochondrial fragmentation during glycolysis shortage or exogenous oxidative stress"

Reports the conditional fusion and fragmentation phenotypes this link describes.

The paper's closing sentence is the caveat that should travel with every use of it: "Identifying whether the observed alterations are also present in ganglion retinal cells, and which of them underlies their degeneration process remains however an essential goal for therapeutic strategy."

Show evidence (1 reference)

PMID:22800932 SUPPORT In Vitro

"Skin fibroblasts with heterozygous OPA1 mutations thus share significant mitochondrial remodeling, and may therefore be useful for analyzing disease pathophysiology."

The authors' own statement of the model's usefulness, which is what this entry relies on in citing it.

🐁

Animal Models

Opa1 delTTAG knock-in mouse

A mouse carrying the recurrent human OPA1 c.2708_2711delTTAG allele, which is found in roughly 30% of DOA patients. It reproduces the selective retinal ganglion cell vulnerability and, in a pre-symptomatic analysis, localizes the earliest mitochondrial abnormality to the unmyelinated prelaminar axon segment. Its limitation for this entry is that it is multi-systemic — the published phenotype includes deafness, encephalomyopathy, peripheral neuropathy, ataxia and cardiomyopathy — so it models the DOA plus spectrum at least as well as the non-syndromic form it was derived from.

Species

Mouse

Genotype

Opa1 c.2708_2711delTTAG heterozygous (Opa1+/delTTAG)

Background

C57BL/6

Publication

PMID:23250881

Pathograph links

Energetic Vulnerability of the Unmyelinated Prelaminar Axon recapitulates fidelity: moderate observes: cellular Pre-symptomatic Opa1+/- mice show mitochondrial fragmentation and increased mitophagy concentrated in the unmyelinated portion of retinal ganglion cell axons, before any neuronal loss.

Limitations: The readout is mitochondrial ultrastructure and mitophagy in a segment of axon, observed at the cellular scale, while the node it is cited for is a tissue-scale claim about the differential vulnerability of a fibre population. The inference from "mitochondria change here first" to "this is why these fibres die" is not made by the experiment. The mouse optic nerve also differs from the human in the extent of the unmyelinated prelaminar segment and in lacking a true collagenous lamina cribrosa.

Readouts

Mitochondrial density, area and circularity by electron microscopy across retina, prelaminar, laminar and retrolaminar zones

Direction: ALTERED

Interpretation: Regional mitochondrial fragmentation identifies the unmyelinated prelaminar segment as the site of earliest change.

Show evidence (1 reference)

PMID:39659974 SUPPORT Model Organism

"Our results show significant mitochondrial fragmentation and increased mitophagy in Opa1+/- mice, indicating early mitochondrial changes prior to neuronal loss."

Reports the measurement behind this readout.

Show evidence (1 reference)

PMID:39659974 SUPPORT Model Organism

Supports treating this model as informative for the prelaminar-vulnerability node.

OPA1 Haploinsufficiency recapitulates fidelity: high observes: molecular The knock-in allele reduces Opa1 transcript by more than 40% in cochlea, confirming that the recurrent human delTTAG allele acts by dosage reduction rather than by a dominant-negative product.

Limitations: The transcript measurement was made in cochlea rather than in retina or optic nerve, so the dosage reduction is inferred to hold in the tissue this entry is about rather than measured there.

Show evidence (1 reference)

PMID:38334784 SUPPORT Model Organism

"Molecular assessment of cochlea demonstrated a reduction of Opa1 mRNA level by greater than 40%, supporting haploinsufficiency as the disease mechanism."

Supports this model as an informative read on the dosage mechanism.

Notes

The same paper reports a multi-systemic poly-degenerative phenotype including deafness, encephalomyopathy, peripheral neuropathy, ataxia and cardiomyopathy. Those features belong to the DOA plus entry, not here; they are the reason fidelity for the non-syndromic disease is recorded as MODERATE rather than HIGH and the reason no FAILS_TO_RECAPITULATE link is asserted in either direction without a study designed to test it.

Show evidence (1 reference)

PMID:23250881 SUPPORT Model Organism

"We generated an Opa1 mouse model carrying the recurrent Opa1(delTTAG) mutation, which is found in 30% of all patients with dominant optic atrophy."

Establishes the provenance and allelic relevance of the model.

{ }

Source YAML

click to show

name: Autosomal Dominant Optic Atrophy
creation_date: "2026-09-10T00:00:00Z"
category: Mendelian
disease_term:
  preferred_term: autosomal dominant optic atrophy, classic form
  term:
    id: MONDO:0008134
    label: autosomal dominant optic atrophy, classic form
synonyms:
- Kjer optic atrophy
- Kjer-type optic atrophy
- optic atrophy type 1
- OPA1
- autosomal dominant optic atrophy, Kjer type
- juvenile optic atrophy
description: >
  Classic (non-syndromic) autosomal dominant optic atrophy — Kjer optic atrophy,
  optic atrophy type 1 — is the commonest inherited optic neuropathy. In the
  majority of genetically solved cases it is caused by a heterozygous
  loss-of-function variant in OPA1, which encodes a dynamin-related GTPase
  anchored to the mitochondrial inner membrane. Insidious, bilateral, broadly
  symmetric visual loss begins in the first decade, with temporal or diffuse
  optic disc pallor, a centrocecal or central scotoma, and an acquired
  blue-yellow (tritan) colour vision defect. Penetrance is incomplete and
  expressivity varies markedly within and between families.

  The entry is deliberately restricted to the non-syndromic phenotype. OPA1
  is a multifunctional protein, and the mechanism is curated as four separable
  consequences of reduced OPA1 dosage — failure of inner-membrane fusion,
  disorganization of cristae, impaired maintenance of the mitochondrial genome,
  and loss of cytochrome c sequestration — which converge on an oxidative
  phosphorylation deficit. The selectivity of the disease is modelled as a
  property of the target tissue rather than of the lesion: retinal ganglion
  cell axons are unmyelinated between the cell body and the lamina cribrosa,
  carry a correspondingly high energy cost, and the smallest-calibre fibres of
  the papillomacular bundle fail first. Why a ubiquitously expressed gene
  produces an essentially eye-restricted disease is not settled, and is
  recorded as a knowledge gap rather than asserted.
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0020250
      label: autosomal dominant optic atrophy
    mapping_predicate: skos:broadMatch
    mapping_source: MONDO
    mapping_justification: >
      MONDO:0020250 is the MONDO parent grouping of this entry's anchor
      MONDO:0008134 and also subsumes the syndromic DOA plus concepts curated in
      Autosomal_Dominant_Optic_Atrophy_Plus. broadMatch, not exactMatch: the
      parent is a union of the classic and the syndromic forms, so it must not
      retire either concept from the curation queue.

notes: >-
  Lump/split decision: curated as a separate Disease entry from
  Autosomal_Dominant_Optic_Atrophy_Plus (MONDO:0014720) rather than as a
  has_subtypes entry on it. The deciding observation is that the two forms
  differ on the genotype axis and not only in the number of organs involved:
  the classic non-syndromic form is predominantly OPA1 haploinsufficiency from
  null alleles (premature termination codons, frameshifts, splice defects,
  whole-gene deletions), whereas the syndromic form is enriched for missense
  alleles in the GTPase domain acting by a dominant-negative mechanism. That
  claim was checked against primary sources rather than assumed: Toomes 2001
  (PMID:11440989) found the mutation spectrum in classic DOA to be
  "predominantly null mutations generating truncated proteins"; Yu-Wai-Man 2010
  (PMID:20157015) quantified the skew in the other direction, with missense
  alleles carrying OR 3.06 and GTPase-region alleles OR 2.29 for the
  multi-system phenotype; and Sladen 2022 (PMID:35652445) states the two halves
  together. The corollary modelled here is mechanistic, not just clinical — a
  dominant-negative allele poisons the OPA1 oligomer and destabilizes the
  mitochondrial genome, which is why secondary multiple mtDNA deletions and
  COX-negative muscle fibres are a DOA-plus finding rather than a classic-form
  one, and why this entry's mtDNA node is about copy number and replication
  rather than about deletion burden.

  The split is not clean at the edges and should not be read as one. Both forms
  arise in OPA1, the allele classes overlap rather than partition, a single
  missense allele can segregate with classic DOA in one family and with plus
  features in another, and subclinical auditory neuropathy is detectable in
  carriers who are clinically non-syndromic. Sensorineural hearing loss is
  therefore deliberately NOT curated as a phenotype here even though the
  retired GeneReviews chapter lists subclinical auditory neuropathy under optic
  atrophy type 1; it is modelled on the DOA-plus entry, and the boundary is
  recorded in differential_diagnoses instead.

  Omissions recorded deliberately. (1) No biochemical: block — plasma
  nicotinamide is reported as relatively deficient in DOA, but the only source
  found for it in this session is the rationale text of a trial registration
  (NCT06007391), which is not a measurement report, so the claim is left to the
  clinical_trials entry that carries it. (2) No datasets: block — no
  disease-relevant accession was triaged in this session, and an untriaged
  accession that merely resolves is the Named Entity Confusion failure mode
  CLAUDE.md warns about. (3) No environmental: block, but the avoidance advice
  IS curated — as a treatment. This was revised in review round 1 and the
  distinction is deliberate. The source files smoking, excessive alcohol and
  mitochondria-toxic antibiotics and antivirals under management, and
  "clinicians advise avoiding X" is a management action, not the causal claim
  "X causes retinal ganglion cell loss in this disease". The first is recorded
  in the Avoidance of Mitochondrial Toxins treatment, quoting the source's own
  sentence; the second is still declined, because no source quantifying an
  exposure effect in OPA1-related optic atrophy was located and a retired
  chapter is weak ground for a causal edge. So the content is present and only
  the causal assertion is withheld. (4) No histopathology: block — human optic nerve histology in
  Kjer disease is old and was not obtained in full text here. (5) PYC-001 is
  curated only as a clinical trial, not as a treatment with a
  therapeutic_modality: the registration record describes intravitreal dosing
  but does not state the molecular mechanism, and the oligonucleotide class
  would have had to be supplied from memory.

  On the retired GeneReviews citation. PMID:20301426 (Optic Atrophy Type 1) has
  been retired and its archival version carries an explicit warning that the
  information may be out of date. It is cited here for the stable clinical and
  care-pathway description of the classic phenotype — onset age, field defect,
  colour defect, electrophysiology, disc appearance, the diagnostic basis,
  low-vision management, the annual surveillance schedule, the agents carriers
  are advised to avoid, and the 50% per-child transmission risk with the
  counselling consequences of reduced penetrance — none of which is the kind of
  claim a chapter revision would be expected to overturn. Review round 1 asked
  for the Diagnosis, Management and Genetic Counseling sections of the abstract
  to be mined as well as Clinical Characteristics, on the reasoning that every
  section present in the abstract should carry backing evidence; that was done,
  and the retirement caveat applies equally to all of it. Every mechanistic,
  epidemiological and genotype-phenotype claim in this entry is cited to
  primary literature instead. A curator who finds a current review covering the
  same clinical ground should move those citations to it.

prevalence:
- population: North of England
  measure_type: POINT_PREVALENCE
  prevalence_class: BAND_1_9_PER_100000
  rate_per_100000: 2.87
  rate_low: 2.54
  rate_high: 3.20
  rate_denominator: POPULATION
  notes: >-
    Population-based ascertainment of clinically diagnosed DOA; the authors
    express the same figure as at least 1 in 35,000 of the general population.
    Restricting to molecularly confirmed OPA1-positive cases lowers it to 2.09
    per 100,000 (95% CI 1.95-2.23), so this record is the clinical-diagnosis
    denominator and is an explicit minimum.
  evidence:
  - reference: PMID:20417570
    reference_title: The prevalence and natural history of dominant optic atrophy due to OPA1 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The minimum point prevalence of DOA in the north of England was 2.87 per 100,000 (95% confidence interval [CI], 2.54-3.20)"
    explanation: Reports the population-based minimum point prevalence curated in this record.
- population: Worldwide
  measure_type: POINT_PREVALENCE
  prevalence_class: BAND_1_9_PER_100000
  rate_per_100000: 4.0
  rate_denominator: POPULATION
  notes: >-
    Estimated minimum prevalence of 1 in 25,000 quoted in a 2022 review;
    normalized as 100000/25000 = 4.0 per 100,000. Note this is a review's
    summary figure rather than a fresh ascertainment, and it disagrees with the
    older 1 in 50,000 figure given when OPA1 was identified (PMID:11017079) and
    with the 1 in 20,000 quoted elsewhere — the spread reflects ascertainment,
    not a change in the disease.
  evidence:
  - reference: PMID:35652445
    reference_title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Autosomal dominant optic atrophy (DOA) is the most common ION, with an estimated minimum prevalence of 1 in 25 000"
    explanation: Source for the 1 in 25,000 minimum-prevalence figure normalized in this record. Evidence source is OTHER because the sentence is background prose in the paper's introduction restating a consensus figure rather than a measurement this paper made.

inheritance:
- name: Autosomal dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  penetrance: INCOMPLETE
  penetrance_percentage: "43"
  expressivity: VARIABLE
  description: >-
    Heterozygous OPA1 variants are transmitted in an autosomal dominant manner
    with incomplete penetrance. Penetrance recalculated within families
    segregating the recurrent c.2708_2711delTTAG allele was as low as 43% and
    62%, far below the ~98% previously reported, and the authors argue that if
    haploinsufficiency is the mechanism then reduced penetrance should not be
    allele-specific. The penetrance_percentage slot records the lower of the two
    family-level figures; it is a single-study family estimate, not a
    population penetrance.
  evidence:
  - reference: PMID:11440989
    reference_title: "Spectrum, frequency and penetrance of OPA1 mutations in dominant optic atrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A re-calculation of the penetrance of this disorder within two of our families indicates figures as low as 43 and 62% associated with the 2708del(TTAG) mutation."
    explanation: Source for the reduced-penetrance figures recorded here.
  - reference: PMID:11440989
    reference_title: "Spectrum, frequency and penetrance of OPA1 mutations in dominant optic atrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "If haploinsufficiency is the mechanism underlying DOA it is unlikely that this figure will be mutation-specific, indicating that the penetrance in DOA is much lower than the 98% reported previously."
    explanation: Supports treating reduced penetrance as a general property of the haploinsufficiency mechanism rather than of one allele.
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Each child of an individual with OPA1 \nhas a 50% chance of inheriting the pathogenic variant."
    explanation: Source for the 50% per-child transmission risk that the Genetic Counseling treatment entry states.
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Most \nindividuals diagnosed with OPA1 have an affected parent; however, de novo \npathogenic variants have been reported."
    explanation: Establishes that transmission is usually from an affected parent while de novo variants occur, which is why no de_novo_rate is recorded — the source gives no figure.

pathophysiology:
- name: OPA1 Haploinsufficiency
  biological_scale: MOLECULAR
  role: trigger
  description: >-
    A heterozygous OPA1 null allele — premature termination codon, frameshift,
    splice-site defect, or large-scale rearrangement — halves the dose of
    functional OPA1 protein. This, rather than a poisoned oligomer, is the
    predominant mechanism of the classic non-syndromic form: the mutation
    spectrum is weighted towards truncating alleles, and a mouse carrying the
    recurrent human c.2708_2711delTTAG allele shows a greater than 40% reduction
    in Opa1 mRNA, which the authors read as supporting haploinsufficiency.
    Missense alleles in the GTPase domain, which act dominant-negatively, are
    instead enriched in the syndromic DOA plus form curated separately.
  gene:
    preferred_term: OPA1
    term:
      id: hgnc:8140
      label: OPA1
  genetic_context:
    variant_origin: GERMLINE
    zygosity: HETEROZYGOUS
    functional_impact_category: LOSS_OF_FUNCTION
    description: >-
      Heterozygous germline loss-of-function OPA1 alleles. Null alleles
      (nonsense, frameshift, splice, whole-gene deletion) predominate in the
      classic form.
  evidence:
  - reference: PMID:11440989
    reference_title: "Spectrum, frequency and penetrance of OPA1 mutations in dominant optic atrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These are predominantly null mutations generating truncated proteins, strongly suggesting that the mechanism underlying DOA is haploinsufficiency."
    explanation: Establishes haploinsufficiency from null alleles as the mechanism of the classic form, the basis of this node.
  - reference: PMID:35652445
    reference_title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The majority of variants are thought to generate null alleles, causing premature termination codons (PTC) or loss of function variants that result in haploinsufficiency"
    explanation: Independently states that most OPA1 variants are null alleles producing haploinsufficiency. Evidence source is OTHER because the sentence summarizes the field in this paper's introduction rather than reporting its own result.
  - reference: PMID:38334784
    reference_title: The human OPA1(delTTAG) mutation induces adult onset and progressive auditory neuropathy in mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Molecular assessment of cochlea demonstrated a reduction of Opa1 mRNA level by greater than 40%, supporting haploinsufficiency as the disease mechanism."
    explanation: Measures the reduction in Opa1 transcript in a knock-in mouse carrying the recurrent human delTTAG allele, corroborating the dosage mechanism (model-organism support, not the sole basis for the human claim).
  - reference: PMID:27860320
    reference_title: OPA1 analysis in an international series of probands with bilateral optic atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "76% of pathogenic mutations observed in 30 (71%) of 42 probands were evaluated to lead to unstable transcripts resulting in haploinsufficiency."
    explanation: Quantifies the haploinsufficiency share of pathogenic OPA1 alleles in an international bilateral-optic-atrophy cohort, putting a number on the qualitative "predominantly null" claim above.
  - reference: PMID:16617242
    reference_title: OPA1 mutations and mitochondrial DNA haplotypes in autosomal dominant optic atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "our results support haploinsufficiency as a genetic mechanism in OPA1-positive cases"
    explanation: A third independent cohort concluding in favour of haploinsufficiency in OPA1-positive autosomal dominant optic atrophy.
  downstream:
  - target: Impaired Mitochondrial Inner-Membrane Fusion
    description: >-
      Reduced OPA1 dosage directly lowers the amount of the inner-membrane
      profusion dynamin available to drive fusion.
    causal_link_type: DIRECT
  - target: Cristae Disorganization
    description: >-
      OPA1 homo-oligomers structure the cristae; loss of half the protein
      disorganizes that architecture.
    causal_link_type: DIRECT
  - target: Impaired Mitochondrial DNA Maintenance
    description: >-
      The exon 4b-containing OPA1 isoforms tether mtDNA nucleoids to the inner
      membrane and promote replication, so reduced OPA1 impairs mtDNA copy
      number and distribution.
    causal_link_type: DIRECT
  - target: Loss of Cytochrome c Sequestration
    description: >-
      OPA1 oligomers hold cristae junctions tight and retain cytochrome c;
      reduced OPA1 lowers the threshold for its release.
    causal_link_type: DIRECT

- name: Impaired Mitochondrial Inner-Membrane Fusion
  biological_scale: CELLULAR
  description: >-
    OPA1 is a profusion dynamin-related protein of the mitochondrial inner
    membrane. Lowering it fragments the mitochondrial network and dissipates
    the inner-membrane potential. This is the canonical OPA1 function, and it
    is separable from the cristae-remodelling function below — genetic and
    molecular dissection places the two in distinct arms.
  cell_types:
  - preferred_term: Retinal ganglion cell
    term:
      id: CL:0000740
      label: retinal ganglion cell
  biological_processes:
  - preferred_term: Mitochondrial fusion
    term:
      id: GO:0008053
      label: mitochondrial fusion
    modifier: DECREASED
  - preferred_term: Inner mitochondrial membrane organization
    term:
      id: GO:0007007
      label: inner mitochondrial membrane organization
    modifier: ABNORMAL
  evidence:
  - reference: PMID:12509422
    reference_title: "Loss of OPA1 perturbates the mitochondrial inner membrane structure and integrity, leading to cytochrome c release and apoptosis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "down-regulation of OPA1 in HeLa cells using specific small interfering RNA (siRNA) leads to fragmentation of the mitochondrial network concomitantly to the dissipation of the mitochondrial membrane potential"
    explanation: Shows directly that reducing OPA1 fragments the mitochondrial network and collapses the membrane potential.
  - reference: PMID:16839885
    reference_title: OPA1 controls apoptotic cristae remodeling independently from mitochondrial fusion.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Optic Atrophy 1 (OPA1), a profusion dynamin-related protein of the inner mitochondrial membrane mutated in dominant optic atrophy"
    explanation: Identifies OPA1 as the inner-membrane profusion dynamin whose reduction this node describes.
  downstream:
  - target: Oxidative Phosphorylation Deficiency
    description: >-
      Network fragmentation and loss of inner-membrane potential impair
      oxidative phosphorylation and ATP synthesis.
    causal_link_type: DIRECT

- name: Cristae Disorganization
  biological_scale: CELLULAR
  description: >-
    OPA1 is a major organizer of the mitochondrial inner membrane; cristae
    integrity depends on it. Reducing OPA1 drastically disorganizes the
    cristae. Critically, this function is genetically and molecularly distinct
    from fusion — OPA1 keeps cristae junctions tight through oligomers of its
    soluble intermembrane-space and integral inner-membrane forms, and does so
    independently of its profusion activity. Curating it as its own node rather
    than folding it into the fusion node is the point: a cristae defect alone is
    sufficient to compromise respiratory-complex organization and cytochrome c
    retention.
  biological_processes:
  - preferred_term: Cristae formation
    term:
      id: GO:0042407
      label: cristae formation
    modifier: DECREASED
  evidence:
  - reference: PMID:12509422
    reference_title: "Loss of OPA1 perturbates the mitochondrial inner membrane structure and integrity, leading to cytochrome c release and apoptosis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "OPA1 is a major organizer of the mitochondrial inner membrane from which the maintenance of the cristae integrity depends"
    explanation: Establishes cristae integrity as dependent on OPA1, the claim of this node.
  - reference: PMID:16839885
    reference_title: OPA1 controls apoptotic cristae remodeling independently from mitochondrial fusion.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Thus, OPA1 has genetically and molecularly distinct functions in mitochondrial fusion and in cristae remodeling during apoptosis."
    explanation: The source of the separability claim that justifies modelling cristae remodelling as a node distinct from fusion.
  downstream:
  - target: Oxidative Phosphorylation Deficiency
    description: >-
      Deranged cristae architecture destabilizes respiratory-chain complex
      organization and lowers oxidative phosphorylation efficiency.
    causal_link_type: DIRECT
  - target: Loss of Cytochrome c Sequestration
    description: >-
      Widening of cristae junctions releases the cytochrome c pool held within
      the cristae lumen.
    causal_link_type: DIRECT

- name: Impaired Mitochondrial DNA Maintenance
  biological_scale: MOLECULAR
  description: >-
    OPA1 is a direct actor in maintenance of the mitochondrial genome, not only
    a shaper of membranes. Silencing the OPA1 variants that include the
    alternately spliced exon 4b depletes mtDNA by inhibiting replication and
    disorganizes the distribution of nucleoids through the network; a small
    hydrophobic peptide cleaved from the exon 4b isoform is embedded in the
    inner membrane and co-immunoprecipitates with nucleoid components. The
    consequence in classic DOA is reduced mtDNA copy number and mislocalized
    nucleoids — which is a different claim from the secondary multiple mtDNA
    deletions and COX-negative muscle fibres that characterize DOA plus, where
    a dominant-negative allele destabilizes the genome more severely.
  biological_processes:
  - preferred_term: Mitochondrial DNA replication
    term:
      id: GO:0006264
      label: mitochondrial DNA replication
    modifier: DECREASED
  - preferred_term: Mitochondrial DNA maintenance
    term:
      id: GO:0032042
      label: mitochondrial DNA metabolic process
    modifier: ABNORMAL
  evidence:
  - reference: PMID:20974897
    reference_title: OPA1 links human mitochondrial genome maintenance to mtDNA replication and distribution.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "silencing of the OPA1 variants including exon 4b leads to mtDNA depletion, secondary to inhibition of mtDNA replication, and to marked alteration of mtDNA distribution in nucleoid and nucleoid distribution throughout the mitochondrial network"
    explanation: Directly demonstrates the mtDNA replication and nucleoid-distribution defect that defines this node.
  - reference: PMID:20974897
    reference_title: OPA1 links human mitochondrial genome maintenance to mtDNA replication and distribution.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "this study places OPA1 as a direct actor in the maintenance of mitochondrial genome integrity"
    explanation: Supports treating mtDNA maintenance as a function of OPA1 in its own right rather than a downstream consequence of the fusion defect.
  - reference: PMID:35652445
    reference_title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "OPA1+/- and OPA1 variant iPSC-RGCs exhibited impaired mitochondrial homeostasis, with reduced bioenergetic output and compromised mitochondrial DNA maintenance."
    explanation: Shows the mtDNA-maintenance defect in the disease-relevant cell type, human iPSC-derived retinal ganglion cells carrying OPA1 null and patient alleles.
  downstream:
  - target: Oxidative Phosphorylation Deficiency
    description: >-
      Reduced mtDNA copy number limits the supply of mtDNA-encoded
      respiratory-chain subunits.
    causal_link_type: DIRECT

- name: Loss of Cytochrome c Sequestration
  biological_scale: MOLECULAR
  description: >-
    OPA1 oligomers keep cristae junctions tight during apoptosis and so retain
    the intracristal cytochrome c pool. This is a protective function exerted
    independently of fusion: OPA1 does not interfere with activation of BAX and
    BAK, but the proapoptotic BH3 protein BID, which widens cristae junctions,
    disrupts OPA1 oligomers. Losing it lowers the threshold for cytochrome c
    release, and in cultured cells reducing OPA1 commits the cell to apoptosis
    with no other stimulus applied.
  biological_processes:
  - preferred_term: Release of cytochrome c from mitochondria
    term:
      id: GO:0001836
      label: release of cytochrome c from mitochondria
    modifier: INCREASED
  evidence:
  - reference: PMID:16839885
    reference_title: OPA1 controls apoptotic cristae remodeling independently from mitochondrial fusion.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "it controls the shape of mitochondrial cristae, keeping their junctions tight during apoptosis"
    explanation: Identifies the cristae-junction-tightening mechanism by which OPA1 sequesters cytochrome c.
  - reference: PMID:12509422
    reference_title: "Loss of OPA1 perturbates the mitochondrial inner membrane structure and integrity, leading to cytochrome c release and apoptosis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "As loss of OPA1 commits cells to apoptosis without any other stimulus, we propose that OPA1 is involved in the cytochrome c sequestration"
    explanation: Shows that OPA1 loss alone is sufficient to trigger the apoptotic program, supporting a lowered apoptotic threshold.
  downstream:
  - target: Retinal Ganglion Cell Degeneration and Optic Nerve Atrophy
    description: >-
      A lowered apoptotic threshold converts a chronic bioenergetic deficit
      into retinal ganglion cell death.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES

- name: Oxidative Phosphorylation Deficiency
  biological_scale: MOLECULAR
  conforms_to: "mitochondrial_dysfunction#Bioenergetic Decline and Oxidative Stress"
  description: >-
    The four upstream arms converge here. Defective fusion and cristae
    derangement together yield defective oxidative phosphorylation with reduced
    ATP synthesis driven by complex I substrates, and the mtDNA defect limits
    the supply of respiratory-chain subunits. The deficit is measurable in the
    disease-relevant cell type: human iPSC-derived retinal ganglion cells
    carrying OPA1 null or patient alleles show reduced bioenergetic output.
    This node is the point of conformance with the mitochondrial_dysfunction
    module, where it plays the central-effector role that disease-specific
    mitochondrial lesions converge upon.
  biological_processes:
  - preferred_term: Oxidative phosphorylation
    term:
      id: GO:0006119
      label: oxidative phosphorylation
    modifier: DECREASED
  - preferred_term: ATP biosynthetic process
    term:
      id: GO:0006754
      label: ATP biosynthetic process
    modifier: DECREASED
  - preferred_term: Reactive oxygen species metabolism
    term:
      id: GO:0072593
      label: reactive oxygen species metabolic process
    modifier: INCREASED
  evidence:
  - reference: PMID:32243103
    reference_title: Idebenone increases chance of stabilization/recovery of visual acuity in OPA1-dominant optic atrophy.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "OPA1‐linked DOA is characterized by defective mitochondrial fusion and cristae derangement, which in turn lead to defective oxidative phosphorylation with reduced ATP synthesis driven by complex I substrates"
    explanation: >-
      States the convergence of the fusion and cristae arms on an oxidative
      phosphorylation and ATP-synthesis deficit. Evidence source is OTHER under
      the rule this entry applies throughout, which was tightened in review
      round 1. evidence_source classifies the evidence the cited publication
      presents; an introduction restating established consensus presents no
      evidence of its own, so it is graded OTHER regardless of what kind of
      study the paper is. Each paper's own results keep the grade matching its
      design, which is why PMID:35652445 and PMID:38334784 appear in this entry
      under OTHER for their background prose and under IN_VITRO and
      MODEL_ORGANISM for their experiments. This also makes the entry
      internally consistent with the review citations PMID:11850115 and
      PMID:21112411, which were already OTHER.
  - reference: PMID:35652445
    reference_title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "reduced bioenergetic output and compromised mitochondrial DNA maintenance"
    explanation: Measures reduced bioenergetic output in OPA1-null and OPA1-variant human iPSC-derived retinal ganglion cells.
  - reference: PMID:22800932
    reference_title: "Defective mitochondrial fusion, altered respiratory function, and distorted cristae structure in skin fibroblasts with heterozygous OPA1 mutations."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Respiratory complex IV activity and subunits steady-state were decreased without alteration of the mitochondrial deoxyribonucleic acid size, amount or transcription."
    explanation: Measures a specific respiratory-chain deficit (complex IV) in primary fibroblasts from patients with heterozygous OPA1 mutations, and reports a physical OPA1-oxidative-phosphorylation interaction by reciprocal immunoprecipitation.
  - reference: PMID:18783614
    reference_title: Mitochondrial oxidative phosphorylation in autosomal dominant optic atrophy.
    supports: REFUTE
    evidence_source: IN_VITRO
    snippet: "We conclude that the pathophysiology of ADOA likely stems from the role of OPA1 in mitochondrial structure or fusion and not from OPA1 support of oxidative phosphorylation."
    explanation: >-
      Direct contradiction of this node, and curated as such rather than
      smoothed over. Mitochondria isolated from six ADOA patients with OPA1
      mutations showed no alteration of electron transport, and the authors
      conclude against an oxidative phosphorylation mechanism. Read alongside
      the supporting items: the measurements were made on isolated mitochondria
      from non-neuronal patient tissue with n=6, which is exactly the setting in
      which a deficit confined to an energetically marginal axon segment would
      be invisible. The honest reading is that a global respiratory block is not
      established, while a local one remains the working model.
  - reference: PMID:18783614
    reference_title: Mitochondrial oxidative phosphorylation in autosomal dominant optic atrophy.
    supports: REFUTE
    evidence_source: IN_VITRO
    snippet: "Results suggest that the nuclear DNA mutations that give rise to ADOA in our patient population do not alter mitochondrial electron transport."
    explanation: The primary negative result itself — no measurable electron-transport defect in patient mitochondria — stated separately from the authors' interpretation of it.
  notes: >-
    The evidence on this node does not point one way, and the disagreement is
    the substantive point rather than a gap. Patient fibroblasts show reduced
    complex IV activity (PMID:22800932) and patient iPSC-derived retinal
    ganglion cells show reduced bioenergetic output (PMID:35652445), while
    isolated mitochondria from ADOA patients show unaltered electron transport
    (PMID:18783614). The reconciliation this entry adopts is positional: the
    deficit is localized to cristae architecture, apoptotic priming, and the
    energetically marginal prelaminar axon rather than being a whole-organism
    respiratory block. That reconciliation is an inference, not a measurement,
    and the conforms_to link to the mitochondrial_dysfunction module should be
    read with it in mind.
  downstream:
  - target: Energetic Vulnerability of the Unmyelinated Prelaminar Axon
    description: >-
      A ubiquitous ATP shortfall is first exposed where the per-unit-length
      energy cost of conduction is highest.
    causal_link_type: DIRECT

- name: Energetic Vulnerability of the Unmyelinated Prelaminar Axon
  biological_scale: TISSUE
  description: >-
    This node carries the selectivity argument, and it is a claim about the
    target tissue rather than about the lesion. Retinal ganglion cell axons are
    unmyelinated from the cell body until they cross the lamina cribrosa, so
    conduction there is non-saltatory and costly; after the lamina they are
    myelinated and propagate saltatorily at much lower cost. Mitochondria are
    distributed accordingly, densely in the prelaminar nerve and sparsely
    behind it. In pre-symptomatic Opa1+/- mice, mitochondrial fragmentation and
    increased mitophagy are found mainly in that unmyelinated segment, before
    any neuronal loss — identifying it as the specific point of vulnerability.
    The asymmetric myelination pattern and an associated impairment of
    mitochondrial axonal transport were proposed as the common explanation for
    this pattern across the mitochondrial optic neuropathies well before the
    mouse data.
  locations:
  - preferred_term: optic nerve
    term:
      id: UBERON:0000941
      label: cranial nerve II
  cell_types:
  - preferred_term: Retinal ganglion cell
    term:
      id: CL:0000740
      label: retinal ganglion cell
  biological_processes:
  - preferred_term: Axonal transport of mitochondrion
    term:
      id: GO:0019896
      label: axonal transport of mitochondrion
    modifier: ABNORMAL
  evidence:
  - reference: PMID:39659974
    reference_title: Opa1 and MT-Nd6 mutations induce early mitochondrial changes in the retina and prelaminar optic nerve of hereditary optic neuropathy mouse models.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "These pre-symptomatic mitochondrial changes were mainly observed in the unmyelinated portion of the retinal ganglion cell axons, where the transmission of the visual information requires high energy expenditure, constituting the specific point of vulnerability in hereditary optic neuropathies."
    explanation: Localizes the earliest mitochondrial abnormality in an Opa1+/- mouse to the unmyelinated prelaminar axon segment and names it the point of vulnerability. Model-organism evidence; the human correlate is the clinical pattern of fibre loss curated in the next node.
  - reference: PMID:39659974
    reference_title: Opa1 and MT-Nd6 mutations induce early mitochondrial changes in the retina and prelaminar optic nerve of hereditary optic neuropathy mouse models.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "since RGC axons are not myelinated in the eye, high energy expenditure is required to ensure optimal non-saltatory transduction of action potentials"
    explanation: States the anatomical and biophysical basis of the energy asymmetry this node depends on.
  - reference: PMID:11850115
    reference_title: "Optic nerve degeneration and mitochondrial dysfunction: genetic and acquired optic neuropathies."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Anatomical peculiarities of optic nerve axons, such as the asymmetric pattern of myelination, may have functional implications on energy dependence and distribution of mitochondrial populations in the different sections of the nerve."
    explanation: The earlier statement of the asymmetric-myelination explanation, proposed as a shared mechanism across the mitochondrial optic neuropathies. Evidence source is OTHER because it is a review.
  downstream:
  - target: Selective Loss of Small-Calibre Papillomacular Bundle Fibres
    description: >-
      Within the vulnerable prelaminar population, the fibres with the least
      favourable surface-to-volume and mitochondrial reserve fail first.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES

- name: Selective Loss of Small-Calibre Papillomacular Bundle Fibres
  biological_scale: TISSUE
  description: >-
    Degeneration is not uniform across the retinal ganglion cell population.
    The smallest-calibre fibres, which make up the papillomacular bundle
    serving central vision, are affected first and most severely. That
    topography explains the clinical triad directly: temporal pallor of the
    optic disc, a central or centrocecal field defect, and early loss of
    central acuity and colour discrimination. The same pattern recurs across a
    large number of optic neuropathies of mitochondrial origin, including
    Leber hereditary optic neuropathy and the toxic and nutritional optic
    neuropathies, which is why it is modelled here as a property of the fibre
    population rather than as something specific to OPA1.
  locations:
  - preferred_term: nerve fiber layer of retina
    term:
      id: UBERON:0001793
      label: nerve fiber layer of retina
  - preferred_term: optic disc
    term:
      id: UBERON:0001783
      label: optic disc
  cell_types:
  - preferred_term: Retinal ganglion cell
    term:
      id: CL:0000740
      label: retinal ganglion cell
  evidence:
  - reference: PMID:11850115
    reference_title: "Optic nerve degeneration and mitochondrial dysfunction: genetic and acquired optic neuropathies."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Selective degeneration of the smallest fibers (papillo-macular bundle) of the human optic nerve occurs in a large number of optic neuropathies characterized primarily by loss of central vision."
    explanation: Establishes the small-fibre, papillomacular topography of degeneration in the human optic nerve. Evidence source is OTHER because it is a review.
  - reference: PMID:32243103
    reference_title: Idebenone increases chance of stabilization/recovery of visual acuity in OPA1-dominant optic atrophy.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "the small axons of the papillomacular bundle are affected first and more severely, leading to the temporal pallor of the optic disc at fundus examination, central scotoma at visual fields and loss of central vision with a consistent drop in visual acuity"
    explanation: Connects the small-axon papillomacular topography to each of the three clinical findings this node is upstream of. Evidence source is OTHER because the statement is review-style framing rather than the cohort study's own result.
  - reference: PMID:35652445
    reference_title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "bilateral central scotomas and optic disc pallor caused by the loss of RGCs within the papillomacular bundle"
    explanation: Independently attributes the central scotoma and disc pallor of DOA to papillomacular bundle RGC loss. Evidence source is OTHER because this is introductory clinical background rather than a finding of the iPSC study.
  downstream:
  - target: Retinal Ganglion Cell Degeneration and Optic Nerve Atrophy
    description: >-
      Cumulative loss of the small central fibres is the substrate of the optic
      nerve atrophy.
    causal_link_type: DIRECT
  - target: Optic disc pallor
    description: >-
      Loss of the temporally entering papillomacular fibres produces temporal,
      and later diffuse, disc pallor.
    causal_link_type: DIRECT
  - target: Centrocecal scotoma
    description: >-
      The papillomacular bundle subserves the central field, so its loss
      produces a centrocecal or central scotoma.
    causal_link_type: DIRECT
  - target: Acquired blue-yellow dyschromatopsia
    description: >-
      Loss of the central fibre population degrades colour discrimination,
      classically in a blue-yellow (tritan) pattern.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Abnormal retinal nerve fiber layer morphology
    description: >-
      Fibre loss thins the peripapillary retinal nerve fibre layer and the
      macular ganglion cell-inner plexiform layer on optical coherence
      tomography.
    causal_link_type: DIRECT

- name: Retinal Ganglion Cell Degeneration and Optic Nerve Atrophy
  biological_scale: TISSUE
  description: >-
    The end state of the mechanism: progressive, selective loss of retinal
    ganglion cells and their axons, with consequent optic nerve degeneration.
    DOA was described from the outset as a non-syndromic loss of visual acuity
    of insidious onset in early childhood caused by progressive and selective
    retinal ganglion cell loss, and that selectivity — rather than any
    systemic mitochondrial failure — is what defines the classic form.
  cell_types:
  - preferred_term: Retinal ganglion cell
    term:
      id: CL:0000740
      label: retinal ganglion cell
  locations:
  - preferred_term: optic nerve
    term:
      id: UBERON:0000941
      label: cranial nerve II
  biological_processes:
  - preferred_term: Neuron apoptotic process
    term:
      id: GO:0051402
      label: neuron apoptotic process
    modifier: INCREASED
  evidence:
  - reference: PMID:38334784
    reference_title: The human OPA1(delTTAG) mutation induces adult onset and progressive auditory neuropathy in mice.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "DOA has been initially described as a non-syndromic moderate to severe loss of visual acuity with an insidious onset in early childhood, caused by a progressive and selective loss of retinal ganglion cells"
    explanation: States the defining clinical-pathological claim of the classic form. Evidence source is OTHER because the sentence is the paper's introductory restatement of the established clinical description rather than its own mouse experiment or an observation it made on patients.
  - reference: PMID:20417570
    reference_title: The prevalence and natural history of dominant optic atrophy due to OPA1 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the primary pathological process selectively targets retinal ganglion cells (RGCs) resulting in optic nerve degeneration"
    explanation: Independently states selective retinal ganglion cell targeting with resulting optic nerve degeneration.
  downstream:
  - target: Optic atrophy
    description: Retinal ganglion cell and axonal loss is seen clinically as bilateral optic atrophy.
    causal_link_type: DIRECT
  - target: Reduced visual acuity
    description: Loss of central fibres reduces visual acuity.
    causal_link_type: DIRECT
  - target: Progressive visual loss
    description: Continued fibre loss produces slow progression of visual impairment over decades.
    causal_link_type: DIRECT
  - target: Abnormality of visual evoked potentials
    description: >-
      Loss and dysfunction of conducting retinal ganglion cell axons delays or
      abolishes the cortical visual evoked response.
    causal_link_type: DIRECT

phenotypes:
- category: Phenotypic abnormality
  name: Optic atrophy
  description: >-
    Bilateral and broadly symmetric optic nerve pallor with insidious onset,
    the obligate and usually sole feature of the classic form.
  phenotype_term:
    preferred_term: Optic atrophy
    term:
      id: HP:0000648
      label: Optic atrophy
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Optic atrophy type 1 (OPA1, or Kjer type optic atrophy) is characterized by bilateral and symmetric optic nerve pallor"
    explanation: Describes the bilateral symmetric optic nerve pallor defining the entity. Cited from a GeneReviews chapter that has since been retired; see the entry-level references note.

- category: Phenotypic abnormality
  name: Optic disc pallor
  description: >-
    Temporal or diffuse pallor of the optic disc on ophthalmoscopy, sometimes
    with disc excavation and a temporal pigmentary grey crescent. The temporal
    predominance reflects the papillomacular fibres' entry point.
  phenotype_term:
    preferred_term: Temporal optic disc pallor
    term:
      id: HP:0000543
      label: Optic disc pallor
  diagnostic: true
  evidence:
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ophthalmoscopic \nexamination discloses temporal or diffuse pallor of the optic discs, sometimes \nassociated with optic disc excavation."
    explanation: Documents the temporal or diffuse disc pallor and associated excavation.

- category: Phenotypic abnormality
  name: Reduced visual acuity
  description: >-
    Insidious decrease in visual acuity, usually noticed between ages 4 and 6
    years. Impairment is usually moderate but spans the full range from
    insignificant to legal blindness, including within one family. Measured
    acuity in a molecularly confirmed cohort averaged 20/173 with a range from
    20/20 to hand movements.
  phenotype_term:
    preferred_term: Reduced visual acuity
    term:
      id: HP:0007663
      label: Reduced visual acuity
  evidence:
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "insidious decrease in visual acuity (usually between ages 4 and \n6 years)"
    explanation: Source for the insidious onset in the first decade.
  - reference: PMID:20417570
    reference_title: The prevalence and natural history of dominant optic atrophy due to OPA1 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Snellen visual acuity varied markedly between OPA1-positive cases with a mean of 20/173 (range 20/20 to hand movements)"
    explanation: Quantifies acuity and its spread in a molecularly confirmed OPA1 cohort.

- category: Phenotypic abnormality
  name: Progressive visual loss
  description: >-
    Slow progression over decades rather than a subacute event. In a
    population-based cohort, visual function worsened in 67.4% of patients
    during follow-up, at a mean rate of 0.032 logMAR per year, though some
    declined up to five times faster.
  phenotype_term:
    preferred_term: Progressive visual loss
    term:
      id: HP:0000529
      label: Progressive visual loss
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:20417570
    reference_title: The prevalence and natural history of dominant optic atrophy due to OPA1 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "visual function worsened in 67.4% of patients during follow-up"
    explanation: Quantifies the proportion progressing in longitudinal follow-up.
  - reference: PMID:20417570
    reference_title: The prevalence and natural history of dominant optic atrophy due to OPA1 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The mean rate of visual loss was 0.032 logarithm of the minimum angle of resolution per year, but some patients experienced faster visual decline (range = 0-0.171 logarithm of the minimum angle of resolution/year)"
    explanation: Gives the rate of progression and its variability.
  - reference: PMID:40329928
    reference_title: "Longitudinal Visual Biomarkers in Dominant Optic Atrophy: A Systematic Review and Meta-Analysis."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "the rate of yearly visual acuity decline (0.022 LogMAR/year., 95% CI: -0.008 to 0.052) was not significantly different from zero (Z = 1.4, p = 0.155)"
    explanation: >-
      Pooling the longitudinal literature, visual acuity decline in DOA is not
      statistically distinguishable from no decline. This cuts against
      progression as a measurable property of visual acuity rather than against
      progression of the disease, and the distinction matters for trial design —
      the same review reports visual acuity as the only biomarker with any
      longitudinal data at all. It is recorded as REFUTE because it contradicts
      the claim this phenotype makes as stated, not because the disease is
      thought to be static.
  notes: >-
    The two evidence items here disagree and are both kept. A single
    population-based cohort found visual function worsening in 67.4% of patients
    at 0.032 logMAR/year (PMID:20417570); a later meta-analysis pooling seven
    studies found 0.022 logMAR/year with a confidence interval crossing zero
    (PMID:40329928). The point estimates are close, so the disagreement is about
    statistical power and the insensitivity of Snellen acuity over short
    follow-up, not about the direction of change. Structural measures
    (peripapillary retinal nerve fibre layer, macular ganglion cell-inner
    plexiform layer) are the candidates for a sensitive endpoint, but the
    meta-analysis found no longitudinal data for them to pool.

- category: Phenotypic abnormality
  name: Centrocecal scotoma
  description: >-
    The characteristic visual field defect, corresponding to the lost
    papillomacular bundle. It is typically centrocecal, central, or
    paracentral, and is often large in those with severe disease.
  phenotype_term:
    preferred_term: Centrocecal scotoma
    term:
      id: HP:0000576
      label: Centrocecal scotoma
  diagnostic: true
  evidence:
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The visual field defect is typically \ncentrocecal, central, or paracentral; it is often large in those with severe \ndisease."
    explanation: Documents the centrocecal/central field defect and its relation to severity.

- category: Phenotypic abnormality
  name: Acquired blue-yellow dyschromatopsia
  description: >-
    An acquired colour vision defect, classically a blue-yellow (tritan) loss,
    though more diffuse non-specific dyschromatopsia is also common. The
    binding is to the general HP term Dyschromatopsia rather than to
    HP:0000552 Tritanomaly: HPO defines tritanomaly as difficulty
    distinguishing yellow and blue possibly related to dysfunction of the S
    photopigment, which is a cone-level claim, whereas the defect here is a
    consequence of retinal ganglion cell loss. The tritan pattern is carried in
    preferred_term instead of manufacturing a narrower ontology match.
  phenotype_term:
    preferred_term: Acquired blue-yellow (tritan) dyschromatopsia
    term:
      id: HP:0007641
      label: Dyschromatopsia
  evidence:
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The color vision defect is often described as acquired blue-yellow loss \n(tritanopia)."
    explanation: Source for the acquired blue-yellow character of the colour defect.
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Tritanopia is the classic feature of color vision defect, but \nmore diffuse nonspecific dyschromatopsia is not uncommon."
    explanation: Supports recording the defect at the general Dyschromatopsia level while noting the classic tritan pattern.

- category: Phenotypic abnormality
  name: Abnormality of visual evoked potentials
  description: >-
    Visual evoked potentials are typically absent or delayed, reflecting loss
    and dysfunction of conducting retinal ganglion cell axons.
  phenotype_term:
    preferred_term: Absent or delayed visual evoked potentials
    term:
      id: HP:0000649
      label: Abnormality of visual evoked potentials
  diagnostic: true
  evidence:
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Visual evoked potentials \nare typically absent or delayed"
    explanation: Documents the visual evoked potential abnormality.

- category: Phenotypic abnormality
  name: Abnormal electroretinogram
  description: >-
    Pattern electroretinography shows an abnormal N95:P50 ratio, the
    electrophysiological signature of retinal ganglion cell rather than
    photoreceptor dysfunction.
  phenotype_term:
    preferred_term: Abnormal N95:P50 ratio on pattern electroretinogram
    term:
      id: HP:0000512
      label: Abnormal electroretinogram
  diagnostic: true
  evidence:
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "pattern electroretinogram shows an abnormal \nN95:P50 ratio"
    explanation: Documents the pattern ERG abnormality localizing dysfunction to the retinal ganglion cells.

- category: Phenotypic abnormality
  name: Abnormal retinal nerve fiber layer morphology
  description: >-
    Optical coherence tomography shows significant thinning of both the
    peripapillary retinal nerve fibre layer and the macular ganglion
    cell-inner plexiform layer, in all four quadrants in established disease,
    with the superior and inferior quadrants thinnest.
  phenotype_term:
    preferred_term: Peripapillary retinal nerve fibre layer and ganglion cell-inner plexiform layer thinning
    term:
      id: HP:0020119
      label: Abnormal retinal nerve fiber layer morphology
  diagnostic: true
  evidence:
  - reference: PMID:30649972
    reference_title: "Optical Coherence Tomography of the Retinal Ganglion Cell Complex in Leber's Hereditary Optic Neuropathy and Dominant Optic Atrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In chronic LHON and DOA, both the pRNFL and RGC-IPL were significantly thinner in all four retinal quadrants relative to controls."
    explanation: Documents the quantitative OCT thinning of the retinal nerve fibre layer and ganglion cell complex in DOA.

genetic:
- name: OPA1
  gene_term:
    preferred_term: OPA1
    term:
      id: hgnc:8140
      label: OPA1
  association: Causative
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  inheritance:
  - name: Autosomal dominant
  notes: >-
    OPA1 is the only gene established for the classic non-syndromic form; more
    than 60% of genetically confirmed DOA carries an OPA1 variant, and OPA1
    accounted for 67% of all molecular diagnoses in a 980-patient hereditary
    optic neuropathy screen. The allele spectrum is dominated by null variants,
    which is the basis of the haploinsufficiency mechanism and of the split
    from the DOA plus entry. Detection rate is strongly family-history
    dependent — 57.6% in probands with a positive family history versus 14.0%
    in singletons — yet OPA1 variants were still found in 40% of apparently
    sporadic optic atrophy in a large referral series, so a negative family
    history does not exclude the gene. Within OPA1-positive patients, missense
    alleles predict a worse visual outcome than other mutational subtypes.
  case_fractions:
  - population: Genetically confirmed DOA (review estimate)
    case_fraction_percent: 60.0
    notes: >-
      Stated as "more than 60%" and recorded as the lower bound; a review's
      summary figure, not a single-cohort measurement.
    evidence:
    - reference: PMID:35652445
      reference_title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "More than 60% of genetically confirmed patients with DOA carry variants in the nuclear OPA1 gene"
      explanation: Source for the OPA1 share of genetically confirmed DOA. Evidence source is OTHER because this is a consensus figure quoted in the paper's introduction rather than its own cohort measurement.
  - population: Molecular diagnoses among 980 patients screened for suspected hereditary optic neuropathy
    case_fraction_percent: 67.0
    cohort_size: 980
    notes: >-
      295 of the 440 patients in whom any molecular defect was identified had an
      OPA1 mutation. The denominator is solved cases within a mixed
      LHON/ADOA referral cohort, not DOA cases, so this is not directly
      comparable with the review figure above.
    evidence:
    - reference: PMID:19319978
      reference_title: Molecular screening of 980 cases of suspected hereditary optic neuropathy with a report on 77 novel OPA1 mutations.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Among these, 295 patients (67%) had an OPA1 mutation, 131 patients (30%) had an mtDNA mutation, and 14 patients (3%), belonging to three unrelated families, had an OPA3 mutation."
      explanation: Gives the OPA1 share of molecular diagnoses in a large hereditary optic neuropathy screen.
  evidence:
  - reference: PMID:11017079
    reference_title: "Nuclear gene OPA1, encoding a mitochondrial dynamin-related protein, is mutated in dominant optic atrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We describe here a nuclear gene, OPA1, that maps within the candidate region and encodes a dynamin-related protein localized to mitochondria."
    explanation: The original identification of OPA1 as the gene for optic atrophy type 1.
  - reference: PMID:11017079
    reference_title: "Nuclear gene OPA1, encoding a mitochondrial dynamin-related protein, is mutated in dominant optic atrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We found four different OPA1 mutations, including frameshift and missense mutations, to segregate with the disease, demonstrating a role for mitochondria in retinal ganglion cell pathophysiology."
    explanation: Establishes cosegregation of OPA1 variants with the disease and the mitochondrial basis of retinal ganglion cell pathology.
  - reference: PMID:20417570
    reference_title: The prevalence and natural history of dominant optic atrophy due to OPA1 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The detection rate of OPA1 mutations was 57.6% among probands with a positive family history of optic atrophy (19/33) and 14.0% among singleton cases (6/43)."
    explanation: Quantifies the family-history dependence of the OPA1 detection rate.
  - reference: PMID:19319978
    reference_title: Molecular screening of 980 cases of suspected hereditary optic neuropathy with a report on 77 novel OPA1 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "OPA1 mutations were found in 157 (40%) of the 392 apparently sporadic cases of optic atrophy"
    explanation: Shows that a negative family history does not exclude OPA1, which matters for the incomplete penetrance of this disease.
  - reference: PMID:20417570
    reference_title: The prevalence and natural history of dominant optic atrophy due to OPA1 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "OPA1 missense mutations were associated with a significantly worse visual outcome compared with other mutational subtypes (P=0.0001)"
    explanation: Genotype-phenotype evidence that missense alleles behave differently from the null alleles that predominate in the classic form — the same axis that separates this entry from the DOA plus entry.
  - reference: PMID:20157015
    reference_title: Multi-system neurological disease is common in patients with OPA1 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "there was an increased risk with missense mutations [odds \nratio = 3.06, 95% confidence interval = 1.44-6.49; P = 0.0027], and mutations \nlocated within the guanosine triphosphate-ase region (odds ratio = 2.29, \n95% confidence interval = 1.08-4.82; P = 0.0271)"
    explanation: Quantifies the allele-class skew away from the classic form and towards the multi-system phenotype, the evidence underpinning this entry's separation from Autosomal_Dominant_Optic_Atrophy_Plus.

diagnosis:
- name: OPA1 Molecular Genetic Testing
  description: >-
    The diagnosis rests on a combination of clinical findings,
    electrophysiologic studies and family history, and/or on identifying a
    heterozygous pathogenic OPA1 variant by molecular genetic testing. Two
    practical points follow from the cohort data curated in the genetic block:
    the detection rate depends strongly on family history (57.6% in probands
    with an affected relative versus 14.0% in singletons), and sequencing alone
    misses large-scale rearrangements, so an OPA1-negative result after coding
    sequencing is not a negative OPA1 result.
  diagnosis_term:
    preferred_term: OPA1 molecular genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  results: Heterozygous pathogenic OPA1 variant
  evidence:
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of OPA1 is made based on a combination of clinical \nfindings, electrophysiologic studies, and family history and/or by the \nidentification of a heterozygous pathogenic variant in OPA1, the only gene known \nto be associated with OPA1, by molecular genetic testing."
    explanation: States the diagnostic basis of the entity and that OPA1 is the only gene known to be associated with it.
  - reference: PMID:20417570
    reference_title: The prevalence and natural history of dominant optic atrophy due to OPA1 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "OPA1-negative cases were then screened for large-scale OPA1 rearrangements and OPA3 mutations."
    explanation: Documents the second-tier rearrangement screen that a coding-sequence-only strategy would miss.
  notes: >-
    Bound to the general NCIT Genetic Testing action. NCIT:C153598 DNA
    Sequencing would name the technique but not the clinical act, and there is
    no NCIT clinical-action term for OPA1 testing specifically, so the
    specificity is carried in preferred_term per the Ontology Term Contract.

- name: Optical Coherence Tomography of the Retinal Ganglion Cell Complex
  description: >-
    Optical coherence tomography quantifies the structural loss, showing
    thinning of both the peripapillary retinal nerve fibre layer and the
    macular ganglion cell-inner plexiform layer. It is the candidate objective
    endpoint for trials, although the meta-analysis of longitudinal biomarkers
    found no pooled longitudinal data for it — visual acuity was the only
    biomarker with any. See the Progressive visual loss phenotype for that
    tension.
  diagnosis_term:
    preferred_term: optical coherence tomography of the retinal ganglion cell complex
    term:
      id: NCIT:C20828
      label: Optical Coherence Tomography
  markers: Peripapillary retinal nerve fibre layer thickness; macular ganglion cell-inner plexiform layer thickness
  evidence:
  - reference: PMID:30649972
    reference_title: "Optical Coherence Tomography of the Retinal Ganglion Cell Complex in Leber's Hereditary Optic Neuropathy and Dominant Optic Atrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This study suggests the usefulness of the RGCC as a potential in vivo biomarker for assessing disease in patients with LHON and DOA."
    explanation: Supports the retinal ganglion cell complex on OCT as an in vivo biomarker in this disease.
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Surveillance: Annual ophthalmologic evaluations (including measurement \nof visual acuity, visual fields, and optical coherence tomography) and hearing \nevaluations."
    explanation: Places optical coherence tomography within the recommended surveillance schedule alongside visual acuity and visual fields.

treatments:
- name: Idebenone
  description: >-
    Off-label idebenone, a short-chain quinone used as an alternative electron
    carrier, has been given to OPA1-DOA patients on the rationale shared with
    Leber hereditary optic neuropathy. In a cohort study comparing treated with
    untreated patients, treatment was associated with stabilization or recovery
    of visual acuity, and the association survived adjustment for confounders.
    This is observational, not a randomized result, and it is the strongest
    pharmacological evidence located for this disease.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: idebenone
      term:
        id: CHEBI:31687
        label: idebenone
  target_mechanisms:
  - target: Oxidative Phosphorylation Deficiency
    description: >-
      Idebenone is used as an alternative electron carrier intended to bypass
      the respiratory-chain deficit downstream of the OPA1 lesion.
  target_phenotypes:
  - preferred_term: Reduced visual acuity
    term:
      id: HP:0007663
      label: Reduced visual acuity
  evidence:
  - reference: PMID:32243103
    reference_title: Idebenone increases chance of stabilization/recovery of visual acuity in OPA1-dominant optic atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We found a significant difference between the last visit and baseline VA in favor of stabilization/recovery in idebenone-treated as compared to untreated patients. This effect was retained after controlling for confounders."
    explanation: The cohort result supporting a visual-acuity benefit, with the observational design stated in the treatment description.
  - reference: PMID:26820596
    reference_title: "A randomized, placebo-controlled trial of the benzoquinone idebenone in a mouse model of OPA1-related dominant optic atrophy reveals a limited therapeutic effect on retinal ganglion cell dendropathy and visual function."
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: "Idebenone appears largely ineffective in protecting Opa1 heterozygous RGCs from dendropathy."
    explanation: >-
      The randomized, placebo-controlled test of this treatment in an Opa1
      mutant mouse found it largely ineffective at the cellular endpoint. It is
      the only randomized evidence on idebenone in this disease in either
      species, and it cuts against the human cohort association above.
  - reference: PMID:26820596
    reference_title: "A randomized, placebo-controlled trial of the benzoquinone idebenone in a mouse model of OPA1-related dominant optic atrophy reveals a limited therapeutic effect on retinal ganglion cell dendropathy and visual function."
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: "in the liver there was an 80.35% (p=0.011) increase in oxidative damage"
    explanation: >-
      A harm signal rather than an efficacy failure, and recorded because it is
      the opposite of the drug's intended antioxidant effect. The same trial also
      found visual function impaired in idebenone-treated wildtype mice, which
      the authors say had not been observed before and raises concerns.
  notes: >-
    The evidence on idebenone points both ways and neither item should be read
    without the other. The human signal is an observational cohort comparison of
    treated with untreated patients (PMID:32243103), with the selection bias that
    implies. The only randomized, placebo-controlled test is in the
    B6;C3-Opa1(Q285STOP) mouse (PMID:26820596), and it found no substantive
    retinal ganglion cell rescue, an 80% rise in hepatic oxidative damage, and
    impaired vision in treated wildtype animals. The mouse result is not
    dispositive for humans — different species, a supratherapeutic 2000
    mg/kg/day dose, and a dendritic-morphology endpoint rather than acuity — but
    it is the stronger design, and the entry does not claim idebenone works.

- name: Low-Vision Rehabilitation and Visual Aids
  description: >-
    Low-vision aids for decreased visual acuity, with annual ophthalmologic
    evaluation including visual acuity, visual fields, and optical coherence
    tomography. This is the mainstay of management, since no disease-modifying
    therapy is licensed.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: low-vision rehabilitation
    term:
      id: NCIT:C15315
      label: Rehabilitation
  evidence:
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Treatment of manifestations: Low-vision aids for decreased visual \nacuity."
    explanation: Source for low-vision aids as the recommended management of the visual deficit.
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Surveillance: Annual ophthalmologic evaluations (including measurement \nof visual acuity, visual fields, and optical coherence tomography) and hearing \nevaluations."
    explanation: Source for the annual surveillance schedule asserted in this treatment's description — visual acuity, visual fields, optical coherence tomography, and hearing evaluation.
  notes: >-
    treatment_term is bound to the general NCIT Rehabilitation action because
    NCIT has no clinical-action term for low-vision rehabilitation or for
    visual-aid provision that is reachable from NCIT:C25218; the specificity is
    carried in preferred_term, per the Ontology Term Contract.

- name: Avoidance of Mitochondrial Toxins
  description: >-
    Carriers are advised to avoid smoking, excessive alcohol intake, and
    medications — antibiotics and antivirals are the examples given — that
    interfere with mitochondrial metabolism. This is curated as a management
    action, which is what the source files it as, and not as an environmental
    causal edge: "clinicians advise avoiding X" is a weaker and differently
    grounded claim than "X causes retinal ganglion cell loss in this disease",
    and no source was located that quantifies an exposure effect in OPA1-related
    optic atrophy. The rationale is plausible and unmeasured — these exposures
    are mitochondrial stressors acting on a cell population already at a
    bioenergetic margin — and the advice is cheap, which is presumably why it is
    given.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: avoidance of mitochondrial toxins and mitochondriotoxic medication
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Agents/circumstances to avoid: Smoking, excessive alcohol intake, \nmedications (antibiotics, antivirals) that interfere with mitochondrial \nmetabolism."
    explanation: Source for the specific agents and circumstances carriers are advised to avoid, filed under management in the cited chapter.
  notes: >-
    Bound to the general NCIT Supportive Care action because NCIT has no
    clinical-action term reachable from NCIT:C25218 for exposure avoidance or
    risk counselling; the specificity is in preferred_term. A reader looking for
    the causal question rather than the management one should note that this
    entry carries no environmental block, and why — see entry notes.

- name: Genetic Counseling
  description: >-
    Autosomal dominant transmission with a 50% recurrence risk per child, but
    counselling is complicated by incomplete penetrance and by markedly
    variable inter- and intrafamilial expressivity, so an at-risk relative
    cannot be given a reliable severity prediction from the genotype alone.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:20301426
    reference_title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "genetic counseling remains \ncomplicated by the incomplete penetrance and the markedly variable inter- and \nintrafamilial expressivity of the disease."
    explanation: Source for the counselling difficulty created by reduced penetrance and variable expressivity.

animal_models:
- name: Opa1 delTTAG knock-in mouse
  species: Mouse
  genotype: Opa1 c.2708_2711delTTAG heterozygous (Opa1+/delTTAG)
  background: C57BL/6
  publication: PMID:23250881
  description: >-
    A mouse carrying the recurrent human OPA1 c.2708_2711delTTAG allele, which
    is found in roughly 30% of DOA patients. It reproduces the selective
    retinal ganglion cell vulnerability and, in a pre-symptomatic analysis,
    localizes the earliest mitochondrial abnormality to the unmyelinated
    prelaminar axon segment. Its limitation for this entry is that it is
    multi-systemic — the published phenotype includes deafness,
    encephalomyopathy, peripheral neuropathy, ataxia and cardiomyopathy — so it
    models the DOA plus spectrum at least as well as the non-syndromic form it
    was derived from.
  modeled_mechanisms:
  - target: Energetic Vulnerability of the Unmyelinated Prelaminar Axon
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Pre-symptomatic Opa1+/- mice show mitochondrial fragmentation and
      increased mitophagy concentrated in the unmyelinated portion of retinal
      ganglion cell axons, before any neuronal loss.
    limitations: >-
      The readout is mitochondrial ultrastructure and mitophagy in a segment of
      axon, observed at the cellular scale, while the node it is cited for is a
      tissue-scale claim about the differential vulnerability of a fibre
      population. The inference from "mitochondria change here first" to "this
      is why these fibres die" is not made by the experiment. The mouse optic
      nerve also differs from the human in the extent of the unmyelinated
      prelaminar segment and in lacking a true collagenous lamina cribrosa.
    readouts:
    - name: Mitochondrial density, area and circularity by electron microscopy across retina, prelaminar, laminar and retrolaminar zones
      target: Energetic Vulnerability of the Unmyelinated Prelaminar Axon
      direction: ALTERED
      interpretation: >-
        Regional mitochondrial fragmentation identifies the unmyelinated
        prelaminar segment as the site of earliest change.
      evidence:
      - reference: PMID:39659974
        reference_title: Opa1 and MT-Nd6 mutations induce early mitochondrial changes in the retina and prelaminar optic nerve of hereditary optic neuropathy mouse models.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Our results show significant mitochondrial fragmentation and increased mitophagy in Opa1+/- mice, indicating early mitochondrial changes prior to neuronal loss."
        explanation: Reports the measurement behind this readout.
    evidence:
    - reference: PMID:39659974
      reference_title: Opa1 and MT-Nd6 mutations induce early mitochondrial changes in the retina and prelaminar optic nerve of hereditary optic neuropathy mouse models.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "These pre-symptomatic mitochondrial changes were mainly observed in the unmyelinated portion of the retinal ganglion cell axons, where the transmission of the visual information requires high energy expenditure, constituting the specific point of vulnerability in hereditary optic neuropathies."
      explanation: Supports treating this model as informative for the prelaminar-vulnerability node.
  - target: OPA1 Haploinsufficiency
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: MOLECULAR
    description: >-
      The knock-in allele reduces Opa1 transcript by more than 40% in cochlea,
      confirming that the recurrent human delTTAG allele acts by dosage
      reduction rather than by a dominant-negative product.
    limitations: >-
      The transcript measurement was made in cochlea rather than in retina or
      optic nerve, so the dosage reduction is inferred to hold in the tissue
      this entry is about rather than measured there.
    evidence:
    - reference: PMID:38334784
      reference_title: The human OPA1(delTTAG) mutation induces adult onset and progressive auditory neuropathy in mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Molecular assessment of cochlea demonstrated a reduction of Opa1 mRNA level by greater than 40%, supporting haploinsufficiency as the disease mechanism."
      explanation: Supports this model as an informative read on the dosage mechanism.
  evidence:
  - reference: PMID:23250881
    reference_title: The human OPA1delTTAG mutation induces premature age-related systemic neurodegeneration in mouse.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We generated an Opa1 mouse model carrying the recurrent Opa1(delTTAG) mutation, which is found in 30% of all patients with dominant optic atrophy."
    explanation: Establishes the provenance and allelic relevance of the model.
  notes: >-
    The same paper reports a multi-systemic poly-degenerative phenotype
    including deafness, encephalomyopathy, peripheral neuropathy, ataxia and
    cardiomyopathy. Those features belong to the DOA plus entry, not here; they
    are the reason fidelity for the non-syndromic disease is recorded as
    MODERATE rather than HIGH and the reason no FAILS_TO_RECAPITULATE link is
    asserted in either direction without a study designed to test it.

experimental_models:
- name: OPA1 patient-derived and isogenic OPA1-null iPSC-derived retinal ganglion cells
  description: >-
    Human induced pluripotent stem cells comprising an isogenic heterozygous
    OPA1-null line made by CRISPR/Cas9 editing of a control, a patient line
    carrying the recurrent c.2708_2711delTTAG null allele, a DOA plus patient
    line carrying the c.1334G>A (p.R445H) missense allele, and CRISPR-corrected
    controls, differentiated in two dimensions to retinal ganglion cells. This
    is the disease-relevant human cell type, and the line panel is the reason
    it matters here: it puts a classic-form null allele and a plus-form
    missense allele in the same dish, which is the comparison the lump/split
    argument turns on.
  experimental_model_type: IPSC_DERIVED_MODEL
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_types:
  - preferred_term: Retinal ganglion cell
    term:
      id: CL:0000740
      label: retinal ganglion cell
  culture_system: Two-dimensional directed differentiation to retinal ganglion cells
  publication: PMID:35652445
  modeled_mechanisms:
  - target: Oxidative Phosphorylation Deficiency
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      OPA1+/- and OPA1-variant iPSC-RGCs show reduced bioenergetic output.
    limitations: >-
      iPSC-derived retinal ganglion cells in two-dimensional culture have no
      unmyelinated prelaminar axon segment, no lamina cribrosa, and no
      long-range axonal compartment, so the system can report the bioenergetic
      deficit but structurally cannot test the selectivity mechanism this entry
      proposes. Differentiation was unimpaired in all mutant lines, so the
      model captures a functional deficit in surviving cells rather than cell
      loss.
    readouts:
    - name: Mitochondrial bioenergetic output
      target: Oxidative Phosphorylation Deficiency
      direction: DECREASED
      interpretation: Reduced bioenergetic output in mutant iPSC-RGCs relative to isogenic and corrected controls.
      evidence:
      - reference: PMID:35652445
        reference_title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "OPA1+/- and OPA1 variant iPSC-RGCs exhibited impaired mitochondrial homeostasis, with reduced bioenergetic output"
        explanation: Reports the bioenergetic measurement behind this readout.
  - target: Impaired Mitochondrial DNA Maintenance
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      The same lines show compromised mitochondrial DNA maintenance.
    limitations: >-
      The abstract reports compromised mtDNA maintenance without separating
      copy number from deletion burden, so it does not by itself distinguish
      the classic-form mtDNA phenotype from the DOA-plus one.
    evidence:
    - reference: PMID:35652445
      reference_title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "OPA1+/- and OPA1 variant iPSC-RGCs exhibited impaired mitochondrial homeostasis, with reduced bioenergetic output and compromised mitochondrial DNA maintenance."
      explanation: Supports this model as informative for the mtDNA-maintenance node.
  evidence:
  - reference: PMID:35652445
    reference_title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "we describe the generation of isogenic, heterozygous OPA1 null induced pluripotent stem cell (iPSC) (OPA1+/-) through clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene editing of a control cell line"
    explanation: Establishes the isogenic design that makes this model informative.

- name: Patient-derived primary skin fibroblasts with heterozygous OPA1 mutations
  description: >-
    Four primary skin fibroblast lines carrying different heterozygous OPA1
    mutations — nonsense and missense, in the GTPase and the C-terminal
    coiled-coil domains — analysed in parallel and quantitatively, which was the
    point of the study: earlier fibroblast reports had been mutually
    inconsistent. The panel shows defective fusion on pharmacological challenge,
    abnormal fragmentation under glycolysis shortage or oxidative stress,
    reduced complex IV activity, and distorted cristae, with a physical
    OPA1-oxidative-phosphorylation interaction on reciprocal
    immunoprecipitation. It is the human in vitro counterweight to the study of
    isolated patient mitochondria that found electron transport unaltered.
  experimental_model_type: PRIMARY_CELL_CULTURE
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:22800932
  modeled_mechanisms:
  - target: Cristae Disorganization
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Altered cristae structure is present in patient fibroblasts carrying
      heterozygous OPA1 mutations.
    limitations: >-
      Skin fibroblasts are not the affected cell type, and the paper says so
      itself: whether these alterations are present in retinal ganglion cells,
      and which of them drives degeneration, is left as an open goal. The fusion
      defect also required pharmacological challenge to become apparent, so the
      unstressed phenotype is mild.
    evidence:
    - reference: PMID:22800932
      reference_title: "Defective mitochondrial fusion, altered respiratory function, and distorted cristae structure in skin fibroblasts with heterozygous OPA1 mutations."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Altered cristae structure coexisted with normal response to pro-apoptotic stimuli and expression of Bax or Bcl2 proteins."
      explanation: >-
        Documents the cristae abnormality in patient cells, and in the same
        sentence the absence of an apoptotic-response abnormality — relevant
        because it does not reproduce the lowered apoptotic threshold that
        cultured OPA1-knockdown cells show.
  - target: Impaired Mitochondrial Inner-Membrane Fusion
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Fusion was defective during pharmacological challenge with the
      protonophore CCCP, and fragmentation appeared under glycolysis shortage or
      exogenous oxidative stress.
    limitations: >-
      The fusion defect is conditional on a stressor rather than constitutive,
      and baseline mitochondria were significantly elongated rather than
      fragmented, so the phenotype is not a simple loss of fusion.
    evidence:
    - reference: PMID:22800932
      reference_title: "Defective mitochondrial fusion, altered respiratory function, and distorted cristae structure in skin fibroblasts with heterozygous OPA1 mutations."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "defective mitochondrial fusion during pharmacological challenge with the protonophore carbonyl cyanide m-chlorophenyl hydrazone, significant mitochondrial elongation with decreased OPA1 and DRP1 proteins, and abnormal mitochondrial fragmentation during glycolysis shortage or exogenous oxidative stress"
      explanation: Reports the conditional fusion and fragmentation phenotypes this link describes.
  evidence:
  - reference: PMID:22800932
    reference_title: "Defective mitochondrial fusion, altered respiratory function, and distorted cristae structure in skin fibroblasts with heterozygous OPA1 mutations."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Skin fibroblasts with heterozygous OPA1 mutations thus share significant mitochondrial remodeling, and may therefore be useful for analyzing disease pathophysiology."
    explanation: The authors' own statement of the model's usefulness, which is what this entry relies on in citing it.
  notes: >-
    The paper's closing sentence is the caveat that should travel with every use
    of it: "Identifying whether the observed alterations are also present in
    ganglion retinal cells, and which of them underlies their degeneration
    process remains however an essential goal for therapeutic strategy."

clinical_trials:
- name: NCT06007391
  phase: PHASE_II
  status: ACTIVE_NOT_RECRUITING
  description: >-
    Pilot study of the tolerance and efficacy of nicotinamide (vitamin B3) in
    DOA and DOA plus, on the rationale that plasma metabolomics in DOA shows a
    relative nicotinamide deficiency and that nicotinamide is neuroprotective
    for the optic nerve. Registered as phase 2/phase 3; recorded here as
    PHASE_II because the enum is single-valued and the registration describes a
    pilot tolerance-and-efficacy study.
  target_phenotypes:
  - preferred_term: Reduced visual acuity
    term:
      id: HP:0007663
      label: Reduced visual acuity
  evidence:
  - reference: clinicaltrials:NCT06007391
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The objective of this pilot study is to test the tolerance and efficacy of nicotinamide in DOA and DOA+ patients."
    explanation: Registration record establishing the trial's objective and population. Graded OTHER because a registration is a protocol document, not study evidence.

- name: NCT06970106
  phase: PHASE_I
  status: RECRUITING
  description: >-
    Phase 1b open-label, randomized single- and repeat-dose study of
    intravitreally administered PYC-001 in participants with confirmed
    OPA1-mutation-associated DOA, enrolling roughly 18 participants across
    Australia, New Zealand and other APAC countries. Recorded as PHASE_I
    because the registration describes it as phase 1b. No treatments entry is
    created for PYC-001: the registration gives the route and dose schedule but
    not the molecular mechanism, and asserting a therapeutic_modality would
    mean supplying the drug class from memory.
  evidence:
  - reference: clinicaltrials:NCT06970106
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "This study aims to gather safety data and determine the optimal dosing regimen for PYC-001 in participants with confirmed OPA1 mutation-associated ADOA."
    explanation: Registration record establishing the trial's objective and population. Graded OTHER because a registration is a protocol document, not study evidence.

differential_diagnoses:
- name: Autosomal Dominant Optic Atrophy Plus
  description: >-
    The syndromic form of the same gene's disease, curated separately at
    MONDO:0014720. It shares the optic neuropathy but adds sensorineural
    deafness, chronic progressive external ophthalmoplegia, myopathy, ataxia
    and peripheral neuropathy, and is enriched for dominant-negative missense
    alleles in the GTPase domain with secondary multiple mtDNA deletions and
    COX-negative muscle fibres. The boundary is clinical rather than genetic and
    is not sharp: extra-ocular features affect up to about 20% of OPA1 carriers,
    and subclinical auditory neuropathy is detectable in carriers who are
    otherwise non-syndromic.
- name: Leber Hereditary Optic Neuropathy
  description: >-
    The other common mitochondrial optic neuropathy, and the most important
    differential. It shares the papillomacular small-fibre topography and the
    final common pathway of retinal ganglion cell loss, but is maternally
    inherited through mtDNA complex I subunit variants, and is subacute and
    sequentially bilateral rather than insidious and congenital-to-infantile in
    onset. The two are genetically distinct: screening 28 LHON patients who were
    negative for the three primary mtDNA variants found no OPA1 mutations.
- name: ACO2-related dominant optic atrophy
  description: >-
    Heterozygous variants in ACO2, encoding mitochondrial aconitase, are
    reported as one of the most frequent causes of dominant optic atrophy, so
    this is a first-tier alternative rather than a rarity once OPA1 is excluded.
    It keeps the disease inside mitochondrial metabolism but moves the lesion
    from inner-membrane dynamics to the tricarboxylic acid cycle, which is a
    different mechanism reaching the same retinal ganglion cell population. The
    relative frequency of ACO2 and OPA1 is not settled here — the source is a
    2026 retrospective series assembled from 13 referral centres, and referral
    series overstate what their centres test for.
  evidence:
  - reference: PMID:41954904
    reference_title: Clinical and Genetic Spectrum of ACO2-Linked Dominant Optic Atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Aconitase 2 (ACO2) gene variants are one of the most frequent causes of dominant optic atrophy (DOA)."
    explanation: Source for ACO2 as a frequent alternative cause of dominant optic atrophy, justifying its place in this differential.

- name: OPA3-related dominant optic atrophy with cataract
  description: >-
    Heterozygous OPA3 variants cause bilateral optic atrophy with premature
    cataract, a more benign picture than the autosomal recessive OPA3 disease
    (3-methylglutaconic aciduria type III, Costeff syndrome). OPA3 is a
    reasonable second-tier test but is rare — no OPA3 mutations were found in
    either a 76-proband population cohort or, beyond three families, in a
    980-patient screen.

discussions:
- discussion_id: rgc_selectivity_of_a_ubiquitous_gene
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Why does halving the dose of OPA1 — a gene expressed ubiquitously, and
    expressed highly in brain and auditory neurons — produce a disease that is
    essentially confined to retinal ganglion cells, and within that population
    to the smallest-calibre papillomacular fibres?
  attaches_to:
  - pathophysiology#Energetic Vulnerability of the Unmyelinated Prelaminar Axon
  - pathophysiology#Selective Loss of Small-Calibre Papillomacular Bundle Fibres
  rationale: >-
    The leading explanation is curated here as mechanism rather than omitted:
    the unmyelinated prelaminar axon segment has a high per-unit-length
    conduction cost, mitochondria are distributed asymmetrically across the
    lamina cribrosa accordingly, and the earliest mitochondrial changes in
    pre-symptomatic Opa1+/- mice are found in exactly that segment. But the
    argument is not closed, and the gap is specific rather than a general plea
    for more research. First, the explanation is an energy-budget argument about
    a segment of axon, whereas the clinical selectivity is a claim about a fibre
    subpopulation — nothing yet connects smallest calibre to earliest failure
    quantitatively. Second, the same reasoning ought to predict disease in other
    high-demand unmyelinated neural compartments, and does not obviously do so.
    Third, the argument cannot be the whole story, because the identical
    anatomical substrate is shared with Leber hereditary optic neuropathy, which
    has a completely different natural history (subacute, sequentially
    bilateral, partial spontaneous recovery) from the same fibre population.
    Fourth, it does not explain the reduced penetrance: an anatomical
    vulnerability that every carrier shares cannot by itself account for 43-62%
    penetrance within a single family carrying one allele. A review of the human
    iPSC-RGC work states the gap plainly.
  evidence:
  - reference: PMID:35652445
    reference_title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "the specific sensitivity of RGCs to OPA1 mutations, especially given the high levels of gene expression within other neuronal tissues, such as the brain and auditory neurons (10), remains unclear"
    explanation: States that the retinal ganglion cell selectivity of OPA1 disease is unexplained despite high expression elsewhere, which is the gap recorded here. Evidence source is OTHER because this is an expert statement of what the field does not know rather than data.
  - reference: PMID:35652445
    reference_title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "the disease mechanisms driving RGC degeneration are poorly understood"
    explanation: Independent statement in the same source that the mechanism of retinal ganglion cell degeneration is not settled. Evidence source is OTHER because this is an expert statement about the state of knowledge rather than data.
  - reference: PMID:39659974
    reference_title: Opa1 and MT-Nd6 mutations induce early mitochondrial changes in the retina and prelaminar optic nerve of hereditary optic neuropathy mouse models.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Identifying the susceptibility of RGCs to such mutations in Opa1 or mitochondrial DNA is therefore essential to a fundamental understanding of these diseases."
    explanation: The authors of the leading mechanistic study frame retinal ganglion cell susceptibility as still requiring explanation.
  - reference: PMID:21112411
    reference_title: Mitochondrial optic neuropathies - disease mechanisms and therapeutic strategies.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "the trigger for RGC loss is much more complex than a simple bioenergetic crisis and other important disease mechanisms have emerged relating to mitochondrial network dynamics, mtDNA maintenance, axonal transport, and the involvement of the cytoskeleton in maintaining a differential mitochondrial gradient at sites such as the lamina cribosa"
    explanation: >-
      States directly that an energy-budget account is insufficient, and names
      the additional mechanisms in play. This is the clearest statement located
      that the selectivity question is open rather than answered by the
      prelaminar-energetics argument alone. Evidence source is OTHER because it
      is a review. Quoted verbatim including the source's spelling of "cribosa".
  - reference: PMID:18783614
    reference_title: Mitochondrial oxidative phosphorylation in autosomal dominant optic atrophy.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "While OPA1 is critical for optic nerve function, the mechanism by which OPA1 mutations lead to blindness is unknown"
    explanation: Independent statement that the mechanism linking OPA1 loss to the optic neuropathy is unknown.
  notes: >-
    Not tagged HUMAN_MODEL_MISMATCH. The distinction matters: the mouse data do
    not conflict with the human disease, they simply do not reach the level of
    the claim. The open question is the mechanism itself, not the translational
    validity of a model that addresses it.

- discussion_id: reduced_penetrance_modifiers
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What determines whether a heterozygous OPA1 null allele carrier develops
    optic atrophy at all, given family-level penetrance as low as 43%?
  attaches_to:
  - inheritance#Autosomal dominant
  - pathophysiology#OPA1 Haploinsufficiency
  rationale: >-
    Penetrance recalculated within two families carrying the recurrent
    c.2708_2711delTTAG allele was 43% and 62%, against a previously reported
    98%. Because the allele is identical within each family, allele identity
    cannot explain the difference, and the original authors argued that if
    haploinsufficiency is the mechanism then reduced penetrance should not be
    allele-specific at all. The corollary is that something other than the OPA1
    genotype sets the threshold — a modifier locus, mtDNA background, or an
    environmental or stochastic contribution to the bioenergetic margin — and
    this entry records no candidate because none was sourced. The practical
    consequence is already visible in ascertainment: OPA1 variants were found in
    40% of apparently sporadic optic atrophy cases in a large referral series,
    so unaffected transmitting carriers are common.
  evidence:
  - reference: PMID:11440989
    reference_title: "Spectrum, frequency and penetrance of OPA1 mutations in dominant optic atrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The mutation screening in this study also identified a number of asymptomatic individuals with OPA1 mutations."
    explanation: Documents asymptomatic carriers, the observation that defines this gap.
  - reference: PMID:19319978
    reference_title: Molecular screening of 980 cases of suspected hereditary optic neuropathy with a report on 77 novel OPA1 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "OPA1 mutations were found in 157 (40%) of the 392 apparently sporadic cases of optic atrophy"
    explanation: Shows the ascertainment consequence of reduced penetrance — a large share of OPA1 disease presents without a family history.
  - reference: PMID:16617242
    reference_title: OPA1 mutations and mitochondrial DNA haplotypes in autosomal dominant optic atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "suggest that mtDNA genetic background may influence disease expression in a subset of cases"
    explanation: >-
      The one sourced candidate modifier: the authors' conclusion that the
      inherited mtDNA background may modify expression. See this gap's notes for
      why the study's headline haplogroup result does not itself support an
      OPA1-penetrance modifier.
  notes: >-
    One lead was checked and downgraded rather than adopted. A deep-research
    report offered mitochondrial haplogroup J as a penetrance modifier in this
    disease, citing PMID:16617242. Reading the source, the three-fold
    over-representation of haplogroup J is reported in OPA1-NEGATIVE patients,
    so it is evidence about the genetic architecture of OPA1-negative dominant
    optic atrophy and not about whether an OPA1 carrier manifests. The same
    paper's broader conclusion — that mtDNA background may influence expression
    in a subset of cases — is what is cited above, and it is a suggestion in a
    29-patient haplotype comparison, not a demonstrated modifier effect. No
    cybrid or segregation experiment establishing causality was located.

- discussion_id: developmental_versus_degenerative_rgc_loss
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    How much of the retinal ganglion cell deficit in classic autosomal dominant
    optic atrophy is a developmental failure that has already happened by the
    time vision is first measured, and how much is ongoing degeneration that a
    therapy started in adulthood could still prevent?
  attaches_to:
  - pathophysiology#Retinal Ganglion Cell Degeneration and Optic Nerve Atrophy
  - pathophysiology#Selective Loss of Small-Calibre Papillomacular Bundle Fibres
  - clinical_trials#NCT06970106
  rationale: >-
    The entry models the disease as degeneration, because that is how the
    phenotype reads — insidious loss from the first decade, slow progression over
    decades. But OPA1 is required for mitochondrial fusion and cristae
    organization during development too, and a recent review states that the
    disease also involves a developmental component and draws the therapeutic
    consequence explicitly. The two accounts predict the same cross-sectional
    picture and different things about treatment: if a substantial share of the
    deficit is developmental, a therapy that restores OPA1 dosage in an adult
    retina cannot recover it, and the trials now recruiting — NCT06970106 doses
    adults intravitreally — would be testing prevention of future loss in
    patients who have already sustained most of theirs. Nothing located here
    partitions the deficit between the two. The experiment implied is
    conditional or inducible Opa1 knockdown at defined postnatal ages, which
    would separate a developmental from an adult-onset contribution; in humans
    the nearest approach is longitudinal structural imaging from the earliest
    age at which it can be obtained, and the same review notes early diagnosis
    is itself difficult.
  evidence:
  - reference: PMID:42101483
    reference_title: "Targeting the OPA1 pathway in Autosomal Dominant Optic Atrophy (ADOA): 25 years from gene discovery to therapeutic strategy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "ADOA also involves a developmental component consistent with OPA1's essential role in mitochondrial fusion, cristae organization, and quality control."
    explanation: States the developmental contribution that this gap asks to be quantified. Evidence source is OTHER because this is a review.
  - reference: PMID:42101483
    reference_title: "Targeting the OPA1 pathway in Autosomal Dominant Optic Atrophy (ADOA): 25 years from gene discovery to therapeutic strategy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "developmental RGC loss may limit therapeutic efficacy of late-stage interventions-a challenge compounded by the difficulty of early diagnosis"
    explanation: >-
      States the therapeutic consequence that makes this gap consequential rather
      than academic. Evidence source is OTHER because this is a review, and note
      the author's own hedge — "may limit" — which is why this is a gap and not
      a curated mechanism. Quoted verbatim including the source's hyphen where a
      dash was intended.
  notes: >-
    Tagged KNOWLEDGE_GAP rather than HUMAN_MODEL_MISMATCH. The reviewer offered
    either. HUMAN_MODEL_MISMATCH would fit if a model system showed something
    whose translation to human biology were the open question, but here the open
    question is the timing of the deficit in the human disease itself, and no
    model result is in conflict with a human observation — the relevant human
    observation has not been made. The distinction CLAUDE.md draws is that
    KNOWLEDGE_GAP means the evidence is absent, which is the case.

- discussion_id: oma1_stress_processing_switch_untested_in_doa
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Does stress-activated OMA1 cleavage of long OPA1 act as the amplifier that
    converts a tolerable 50% OPA1 dosage reduction into retinal ganglion cell
    loss, and does it explain why the same allele manifests in one carrier and
    not another?
  attaches_to:
  - pathophysiology#Impaired Mitochondrial Inner-Membrane Fusion
  - pathophysiology#OPA1 Haploinsufficiency
  rationale: >-
    Long OPA1 is constitutively cleaved by YME1L and OMA1 at two sites, and the
    balanced accumulation of long and short forms maintains fusion; under
    mitochondrial stress OMA1 converts OPA1 entirely to short isoforms,
    inhibiting fusion and triggering fragmentation. That is a switch, and a
    switch is the kind of thing that could turn a graded dosage deficit into a
    threshold event — which is what reduced penetrance and the decades-long
    latency of this disease both look like. It is recorded as a gap rather than
    as a pathophysiology node because nothing located here tests it in OPA1
    haploinsufficient retinal ganglion cells, in patient tissue, or in an ADOA
    model: the supporting work is mouse embryonic fibroblast genetics on
    OPA1 processing generally, and it is unconnected to the disease. The
    experiment implied is OMA1 loss or inhibition in an Opa1+/- retina. Note the
    same source complicates the picture, since deleting Oma1 restored
    tubulation, cristae morphogenesis and apoptotic resistance in YME1L-null
    cells and long OPA1 alone sufficed for fusion — so processing is not
    required for fusion, and the switch is about quality control rather than
    about fusion capacity per se.
  evidence:
  - reference: PMID:24616225
    reference_title: The i-AAA protease YME1L and OMA1 cleave OPA1 to balance mitochondrial fusion and fission.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Stress-induced OPA1 processing by OMA1 converts OPA1 completely into short isoforms, inhibits fusion, and triggers mitochondrial fragmentation."
    explanation: Describes the stress-gated proteolytic switch that this gap asks about.
  - reference: PMID:24616225
    reference_title: The i-AAA protease YME1L and OMA1 cleave OPA1 to balance mitochondrial fusion and fission.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "deletion of Oma1 restored mitochondrial tubulation, cristae morphogenesis, and apoptotic resistance in cells lacking YME1L"
    explanation: >-
      The experimental result showing that removing OMA1 rescues cristae and
      apoptotic phenotypes, which is what makes OMA1 a candidate target — and
      also what shows the switch is not simply a fusion-capacity mechanism.
  notes: >-
    Sourced from a deep-research report lead and checked against the primary
    paper before recording. No claim is made that this mechanism operates in
    autosomal dominant optic atrophy; the gap exists because it has not been
    asked.

references:
- reference: PMID:20301426
  title: "Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
  tags:
  - GeneReviews
- reference: PMID:11017079
  title: "Nuclear gene OPA1, encoding a mitochondrial dynamin-related protein, is mutated in dominant optic atrophy."
- reference: PMID:11440989
  title: "Spectrum, frequency and penetrance of OPA1 mutations in dominant optic atrophy."
  findings:
  - statement: >-
      Dominant optic atrophy and Leber hereditary optic neuropathy are
      genetically distinct: no OPA1 variants were found in 28 LHON patients
      negative for the three primary mtDNA variants.
    supporting_text: "No mutations were identified in any LHON patients, indicating that DOA and LHON are genetically distinct."
- reference: PMID:11850115
  title: "Optic nerve degeneration and mitochondrial dysfunction: genetic and acquired optic neuropathies."
- reference: PMID:12509422
  title: "Loss of OPA1 perturbates the mitochondrial inner membrane structure and integrity, leading to cytochrome c release and apoptosis."
- reference: PMID:16839885
  title: OPA1 controls apoptotic cristae remodeling independently from mitochondrial fusion.
- reference: PMID:19319978
  title: Molecular screening of 980 cases of suspected hereditary optic neuropathy with a report on 77 novel OPA1 mutations.
- reference: PMID:20157015
  title: Multi-system neurological disease is common in patients with OPA1 mutations.
- reference: PMID:20417570
  title: The prevalence and natural history of dominant optic atrophy due to OPA1 mutations.
- reference: PMID:20974897
  title: OPA1 links human mitochondrial genome maintenance to mtDNA replication and distribution.
- reference: PMID:23250881
  title: The human OPA1delTTAG mutation induces premature age-related systemic neurodegeneration in mouse.
- reference: PMID:16617242
  title: OPA1 mutations and mitochondrial DNA haplotypes in autosomal dominant optic atrophy.
- reference: PMID:18783614
  title: Mitochondrial oxidative phosphorylation in autosomal dominant optic atrophy.
- reference: PMID:21112411
  title: Mitochondrial optic neuropathies - disease mechanisms and therapeutic strategies.
- reference: PMID:22800932
  title: "Defective mitochondrial fusion, altered respiratory function, and distorted cristae structure in skin fibroblasts with heterozygous OPA1 mutations."
- reference: PMID:24616225
  title: The i-AAA protease YME1L and OMA1 cleave OPA1 to balance mitochondrial fusion and fission.
- reference: PMID:27860320
  title: OPA1 analysis in an international series of probands with bilateral optic atrophy.
- reference: PMID:26820596
  title: "A randomized, placebo-controlled trial of the benzoquinone idebenone in a mouse model of OPA1-related dominant optic atrophy reveals a limited therapeutic effect on retinal ganglion cell dendropathy and visual function."
- reference: PMID:41954904
  title: Clinical and Genetic Spectrum of ACO2-Linked Dominant Optic Atrophy.
- reference: PMID:42101483
  title: "Targeting the OPA1 pathway in Autosomal Dominant Optic Atrophy (ADOA): 25 years from gene discovery to therapeutic strategy."
- reference: PMID:30649972
  title: "Optical Coherence Tomography of the Retinal Ganglion Cell Complex in Leber's Hereditary Optic Neuropathy and Dominant Optic Atrophy."
- reference: PMID:32243103
  title: Idebenone increases chance of stabilization/recovery of visual acuity in OPA1-dominant optic atrophy.
- reference: PMID:35652445
  title: Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.
- reference: PMID:38334784
  title: The human OPA1(delTTAG) mutation induces adult onset and progressive auditory neuropathy in mice.
- reference: PMID:39659974
  title: Opa1 and MT-Nd6 mutations induce early mitochondrial changes in the retina and prelaminar optic nerve of hereditary optic neuropathy mouse models.
- reference: PMID:40329928
  title: "Longitudinal Visual Biomarkers in Dominant Optic Atrophy: A Systematic Review and Meta-Analysis."
- reference: clinicaltrials:NCT06007391
  title: Pilot Study of Tolerance and Efficacy Nicotinamide (Vitamin B3) in Dominant Optic Atrophy OPA1
- reference: clinicaltrials:NCT06970106
  title: "A Phase 1b Open-Label, Randomized, Single Dose and Repeat Dose Study to Evaluate the Single and Repeat Dose Safety and Tolerability of Intravitreally Administered PYC-001 in Participants With Confirmed OPA1 Mutation-Associated Autosomal Dominant Optic Atrophy"

📚

References & Deep Research

References

PMID:20301426

Optic Atrophy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY.

No top-level findings curated for this source.

PMID:11017079

Nuclear gene OPA1, encoding a mitochondrial dynamin-related protein, is mutated in dominant optic atrophy.

No top-level findings curated for this source.

PMID:11440989

Spectrum, frequency and penetrance of OPA1 mutations in dominant optic atrophy.

1 finding

Dominant optic atrophy and Leber hereditary optic neuropathy are genetically distinct: no OPA1 variants were found in 28 LHON patients negative for the three primary mtDNA variants.

"No mutations were identified in any LHON patients, indicating that DOA and LHON are genetically distinct."

PMID:11850115

Optic nerve degeneration and mitochondrial dysfunction: genetic and acquired optic neuropathies.

No top-level findings curated for this source.

PMID:12509422

Loss of OPA1 perturbates the mitochondrial inner membrane structure and integrity, leading to cytochrome c release and apoptosis.

No top-level findings curated for this source.

PMID:16839885

OPA1 controls apoptotic cristae remodeling independently from mitochondrial fusion.

No top-level findings curated for this source.

PMID:19319978

Molecular screening of 980 cases of suspected hereditary optic neuropathy with a report on 77 novel OPA1 mutations.

No top-level findings curated for this source.

PMID:20157015

Multi-system neurological disease is common in patients with OPA1 mutations.

No top-level findings curated for this source.

PMID:20417570

The prevalence and natural history of dominant optic atrophy due to OPA1 mutations.

No top-level findings curated for this source.

PMID:20974897

OPA1 links human mitochondrial genome maintenance to mtDNA replication and distribution.

No top-level findings curated for this source.

PMID:23250881

The human OPA1delTTAG mutation induces premature age-related systemic neurodegeneration in mouse.

No top-level findings curated for this source.

PMID:16617242

OPA1 mutations and mitochondrial DNA haplotypes in autosomal dominant optic atrophy.

No top-level findings curated for this source.

PMID:18783614

Mitochondrial oxidative phosphorylation in autosomal dominant optic atrophy.

No top-level findings curated for this source.

PMID:21112411

Mitochondrial optic neuropathies - disease mechanisms and therapeutic strategies.

No top-level findings curated for this source.

PMID:22800932

Defective mitochondrial fusion, altered respiratory function, and distorted cristae structure in skin fibroblasts with heterozygous OPA1 mutations.

No top-level findings curated for this source.

PMID:24616225

The i-AAA protease YME1L and OMA1 cleave OPA1 to balance mitochondrial fusion and fission.

No top-level findings curated for this source.

PMID:27860320

OPA1 analysis in an international series of probands with bilateral optic atrophy.

No top-level findings curated for this source.

PMID:26820596

A randomized, placebo-controlled trial of the benzoquinone idebenone in a mouse model of OPA1-related dominant optic atrophy reveals a limited therapeutic effect on retinal ganglion cell dendropathy and visual function.

No top-level findings curated for this source.

PMID:41954904

Clinical and Genetic Spectrum of ACO2-Linked Dominant Optic Atrophy.

No top-level findings curated for this source.

PMID:42101483

Targeting the OPA1 pathway in Autosomal Dominant Optic Atrophy (ADOA): 25 years from gene discovery to therapeutic strategy.

No top-level findings curated for this source.

PMID:30649972

Optical Coherence Tomography of the Retinal Ganglion Cell Complex in Leber's Hereditary Optic Neuropathy and Dominant Optic Atrophy.

No top-level findings curated for this source.

PMID:32243103

Idebenone increases chance of stabilization/recovery of visual acuity in OPA1-dominant optic atrophy.

No top-level findings curated for this source.

PMID:35652445

Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells.

No top-level findings curated for this source.

PMID:38334784

The human OPA1(delTTAG) mutation induces adult onset and progressive auditory neuropathy in mice.

No top-level findings curated for this source.

PMID:39659974

Opa1 and MT-Nd6 mutations induce early mitochondrial changes in the retina and prelaminar optic nerve of hereditary optic neuropathy mouse models.

No top-level findings curated for this source.

PMID:40329928

Longitudinal Visual Biomarkers in Dominant Optic Atrophy: A Systematic Review and Meta-Analysis.

No top-level findings curated for this source.

clinicaltrials:NCT06007391

Pilot Study of Tolerance and Efficacy Nicotinamide (Vitamin B3) in Dominant Optic Atrophy OPA1

No top-level findings curated for this source.

clinicaltrials:NCT06970106

A Phase 1b Open-Label, Randomized, Single Dose and Repeat Dose Study to Evaluate the Single and Repeat Dose Safety and Tolerability of Intravitreally Administered PYC-001 in Participants With Confirmed OPA1 Mutation-Associated Autosomal Dominant Optic Atrophy

No top-level findings curated for this source.

Deep Research

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (1)

Create: Autosomal Dominant Optic Atrophy · 2026-09-10T17:08:12Z · View source

Created kb/disorders/Autosomal_Dominant_Optic_Atrophy.yaml for the classic non-syndromic form (MONDO:0008134, OPA1 hgnc:8140), the queue stub stubs/Autosomal_Dominant_Optic_Atrophy_Classic_Form.yaml having been deleted in the same change. Lump/split. Curated as a Disease entry separate from the existing Autosomal_Dominant_Optic_Atrophy_Plus (MONDO:0014720) rather than as a has_subtypes entry on it. The working hypothesis in claim issue #11601 was that the two differ on the genotype axis, and it was checked against primary sources rather than assumed: PMID:11440989 reports the classic-form spectrum as predominantly null alleles implying haploinsufficiency; PMID:27860320 quantifies that at 76 percent of pathogenic alleles; PMID:16617242 concludes in favour of haploinsufficiency in OPA1-positive cases; PMID:20157015 quantifies the skew the other way for the syndromic form (missense OR 3.06, GTPase-region OR 2.29). The hypothesis held. The non-sharpness of the boundary is recorded in entry notes and differential_diagnoses, and sensorineural hearing loss is deliberately left on the DOA-plus entry. Mechanism. OPA1's separable functions are curated as four distinct pathophysiology nodes with their own evidence rather than one bundled node -- inner-membrane fusion (PMID:12509422, PMID:16839885), cristae disorganization (same pair, citing the explicit genetic/molecular separability statement), mtDNA maintenance via the exon 4b isoform and nucleoid tethering (PMID:20974897, PMID:35652445), and cytochrome c sequestration at cristae junctions (PMID:16839885, PMID:12509422). They converge on an Oxidative Phosphorylation Deficiency node which conforms_to mitochondrial_dysfunction#Bioenergetic Decline and Oxidative Stress. biological_scale is set on every node. Retinal ganglion cell selectivity is curated as mechanism across two nodes -- the unmyelinated prelaminar axon's energy cost (PMID:39659974 mouse, PMID:11850115) and small-calibre papillomacular fibre loss (PMID:11850115, PMID:32243103, PMID:35652445) -- and the residual uncertainty is recorded as a KNOWLEDGE_GAP discussion rather than hand-waved, citing PMID:35652445 that the specific sensitivity of RGCs remains unclear and PMID:21112411 that the trigger is much more complex than a simple bioenergetic crisis. Two further KNOWLEDGE_GAP discussions cover reduced penetrance modifiers and the untested OMA1/YME1L stress-processing switch. Counter-evidence is curated rather than smoothed: the OXPHOS node carries two REFUTE items from PMID:18783614 (electron transport unaltered in isolated patient mitochondria) alongside the supporting items, with a node-level note stating the disagreement and the positional reconciliation adopted; and the Progressive visual loss phenotype carries a REFUTE item from the PMID:40329928 meta-analysis whose pooled visual-acuity decline is not significantly different from zero. Deep research. One report, requested from falcon. Falcon returned HTTP 402 (account out of credits); the run was repeated once with --fallback per the run brief and resolved to openscientist, so the committed report is research/Autosomal_Dominant_Optic_Atrophy-deep-research-openscientist.md with fell_back true, requested_provider falcon and the 402 recorded in its frontmatter. just preflight-dr PASSED against MONDO:0008134 (OPA1 mentioned 105 times, OMIM 165500 agreeing). just validate-research-terms was run in place and flagged two report mis-bindings (GO:0000002 obsolete; HP:0007766 Optic disc hypoplasia used for OCT RNFL thinning) -- neither was bound in the entry, which uses HP:0020119 for that phenotype. Report claims were treated as leads: six were verified against primary sources and adopted (PMID:18783614, 24616225, 21112411, 16617242, 22800932, 40329928); the report's mtDNA haplogroup J penetrance-modifier claim was checked, found to describe OPA1-NEGATIVE patients, and downgraded to a caveat in the penetrance gap's notes rather than curated as a modifier. Terms. Every CURIE was read from a lookup in the same step it was written -- ols:mondo, ols:go, ols:cl, ols:hp, ols:uberon, ols:ncit, ols:chebi, and cache/hgnc/terms.csv for hgnc:8140 confirming OPA1. HP:0000552 Tritanomaly was deliberately NOT bound for the acquired blue-yellow defect because HPO defines it as S-photopigment dysfunction, a cone-level claim; HP:0007641 Dyschromatopsia is bound with the tritan pattern carried in preferred_term, and the reasoning is in the phenotype description. Validators run and their results. just validate PASSED (77/77 snippets verified). just validate-terms PASSED. just count-verified-snippets 77/77. just check-duplicate-keys OK. just check-entity-refs OK. just check-causal-targets OK (no new dangling targets). just check-qualifier-terms OK (no qualifier terms added, so check-qualifier-terms-online was not needed). just check-enum-values OK. just normalize-cache and just check-term-cache-integrity OK (18 term + 24 enum cache files match the contract). just validate-disorders PASSED, all three batched lanes. Whole-KB text checks: check-folded-hyphens initially reported one new finding in this file (a line-end hyphen in a folded scalar) and check-snippet-length one (a four-word snippet); both were fixed by rephrasing and by quoting the full sentence, and no baseline file was modified. check-environmental-evidence is not applicable -- no environmental block was added. Deliberate omissions, all recorded in the entry notes: no biochemical block (the plasma nicotinamide deficiency is sourced only to a trial registration's rationale, not a measurement report); no datasets block (no accession was relevance-triaged); no environmental block (the only exposure guidance found is in a retired GeneReviews chapter); no histopathology block; and PYC-001 is curated as a clinical trial only, with no therapeutic_modality, because its registration gives route and dose but not drug class. PMID:20301426 is cited for clinical description only and its retirement is flagged in entry notes.

OpenScientist ▸

Key Findings

openscientist-autonomous 28 citations 2026-09-10T16:56:44.374822

Key Findings

Finding 1 — OPA1 haploinsufficiency is the predominant molecular cause

Heterozygous mutations in OPA1 (3q29) are the single most frequent molecular cause of DOA, accounting for approximately 60–90% of cases. The centralized OPA1 Variome database registers 516 unique variants across 831 patients (697 with isolated DOA, 47 with DOA-plus, 83 asymptomatic/unclassified), documenting the breadth of the mutational spectrum. Critically, the dominant mechanism is loss of dosage rather than a toxic product: in an international series of probands with bilateral optic atrophy, 76% of pathogenic mutations, observed in 71% of probands, were predicted to yield unstable transcripts and hence haploinsufficiency. This establishes that a roughly 50% reduction in OPA1 protein is sufficient to precipitate RGC degeneration — a foundation that directly rationalizes gene-augmentation and expression-upregulation therapeutic strategies.

"we demonstrated that heterozygous mutations in OPA1 are the most frequent molecular cause of DOA" — PMID: 33340656

"76% of pathogenic mutations observed in 30 (71%) of 42 probands were evaluated to lead to unstable transcripts resulting in haploinsufficiency" — PMID: 27860320

"now covers a total of 831 patients: 697 with isolated dominant optic atrophy (DOA), 47 with DOA 'plus'… It comprises 516 unique OPA1 variants" — PMID: 31500643

Finding 2 — OPA1 is a mitochondrial inner-membrane dynamin GTPase controlling fusion, cristae, and apoptosis

OPA1 encodes a dynamin-related GTPase imported into mitochondria and localized to the inner membrane and intermembrane space. Alternative splicing of three exons yields multiple isoforms that oligomerize to structure the cristae and mediate fusion of both the inner and outer membranes, thereby shaping the entire mitochondrial network. Beyond fusion, OPA1 supports oxidative phosphorylation, mtDNA maintenance, calcium homeostasis, and apoptosis regulation. Patient-derived fibroblasts carrying heterozygous OPA1 mutations reproducibly display defective mitochondrial fusion, distorted cristae ultrastructure, and reduced respiratory (complex IV) function — confirming that the genetic lesion translates into measurable organelle dysfunction in human cells.

"OPA1 encodes a dynamin-related GTPase imported into mitochondria and located to the inner membrane and intermembrane space. The many OPA1 isoforms… form complex homopolymers that structure mitochondrial cristae, and contribute to fusion of the outer membrane, thus shaping the whole mitochondrial network." — PMID: 33340656

"fibroblasts with heterozygous OPA1 mutations present with several mitochondrial alterations" — PMID: 22800932

Note: One study of mitochondria from 16 ADOA patients found respiratory-chain activity largely preserved (PMID: 18783614), arguing that the primary defect lies in cristae/fusion architecture rather than a simple bioenergetic block — a nuance reflected in the mechanism section below.

Finding 3 — DOA-plus (syndromic disease) affects ~20% of carriers via a dominant-negative, mtDNA-instability mechanism

Extra-ocular neurological complications occur in up to 20% of OPA1 mutation carriers. In a series of 104 patients from 45 families, the syndromic phenotype comprised sensorineural deafness (typically emerging in late childhood/early adulthood), followed by ataxia, myopathy, peripheral neuropathy, and progressive external ophthalmoplegia from the third decade onward. Genotype strongly modulates this risk: missense mutations (OR = 3.06, 95% CI 1.44–6.49; P = 0.0027) and mutations within the GTPase domain (OR = 2.29, 95% CI 1.08–4.82; P = 0.0271) confer higher syndromic risk than truncating alleles. Mechanistically, DOA-plus patients harbour multiple mtDNA deletions in skeletal muscle with COX-negative ragged-red fibres, revealing a role for OPA1 in mtDNA stability and implicating a dominant-negative (not merely haploinsufficient) mode of action for these alleles.

"extra-ocular neurological complications are common in OPA1 disease, and affect up to 20% of all mutational carriers" — PMID: 20157015

"these patients all harboured multiple deletions of mitochondrial DNA (mtDNA) in their skeletal muscle, thus revealing an unrecognized role of the OPA1 protein in mtDNA stability" — PMID: 18158317

Finding 4 — Mouse models recapitulate RGC dendropathy and bioenergetic failure; idebenone effect is limited

The heterozygous B6;C3-Opa1(Q285STOP) mouse (~50% Opa1 reduction) is the workhorse ADOA model. It shows RGC dendritic pruning, reduced synaptic connectivity (decreased PSD-95, loss of glutamatergic synapses in the inner plexiform layer), mitochondrial fragmentation, and impaired respiration (reduced basal, ATP-linked, and reserve capacity in purified RGCs). A randomized, placebo-controlled trial of idebenone (2000 mg/kg/day; 56 mutant + 63 WT mice) raised brain ATP by 97.7% (P = 0.035) and transiently improved the optokinetic response (P = 0.003), but produced no substantive RGC rescue and increased hepatic oxidative damage (+80.35%, P = 0.011). The model thus validates the RGC-selective, dendrite-first pathology and underscores the limited efficacy of first-generation neuroprotection.

"Opa1 deficiency leads to significant fragmentation of mitochondrial morphology, activation of mitochondrial motility and impaired respiratory function in RGCs from the B6; C3-Opa1Q285STOP mouse model" — PMID: 32561926

"ATP levels were raised by 0.57 nmol/mg (97.73%, p=0.035) in brain from idebenone-treated Opa1 mutant mice, but in the liver there was an 80.35% (p=0.011) increase in oxidative damage" — PMID: 26820596

"We observed decreased levels of postsynaptic density protein 95 in Opa1(+/-) mutant mice consistent with synaptic loss in the inner plexiform layer" — PMID: 22300878

Finding 5 — Epidemiology: point prevalence ~2.87/100,000 with slow, childhood-onset progression

A population-based study in the north of England established a minimum point prevalence of 2.87 per 100,000. OPA1 detection was 57.6% among familial probands versus 14.0% among singletons, and ~64% of DOA families carried an OPA1 mutation. Onset is typically in the first decade (median ~6 years; range 3–24 in a Chinese cohort). A systematic review/meta-analysis of longitudinal biomarkers quantified visual-acuity decline at only 0.022 LogMAR/year (95% CI −0.008 to 0.052; Z = 1.4, p = 0.155) — not statistically different from zero — confirming an indolent natural history. Denmark historically reports a higher prevalence (~1:10,000) attributed to a founder effect.

"The minimum point prevalence of DOA in the north of England was 2.87 per 100,000" — PMID: 20417570

"the rate of yearly visual acuity decline (0.022 LogMAR/year… 95% CI: -0.008 to 0.052) was not significantly different from zero (Z = 1.4, p = 0.155)" — PMID: 40329928

Finding 6 — OCT inner-retinal thinning is the key diagnostic biomarker; missense variants cause worse disease

In a cohort of 108 OPA1-ADOA patients, spectral-domain OCT measures of peripapillary retinal nerve fibre layer (pRNFL) and macular ganglion cell layer (mGCL) thickness were the principal structural determinants of visual function: ~0.1 logMAR worsening per 3.2 µm of mGCL loss (P < 0.001); papillomacular-bundle mean-deviation loss of 0.75 dB per µm mGCL (P = 0.002); mGCL thinning with age (−0.06 µm/yr) and over follow-up (−0.26 µm/yr). Genotype stratified severity: missense variants produced worse acuity (0.83 vs 0.49 logMAR, P = 0.016), worse field mean deviation (−11.48 vs −3.04 dB, P = 0.005), and thinner pRNFL (52.41 vs 66.41 µm, P < 0.001) than haploinsufficiency variants. The cardinal diagnostic constellation is reduced acuity, colour-vision deficits, centrocecal scotomas, and temporal optic-disc pallor.

"Missense variants caused worse VA (0.83 vs. 0.49 logMAR, P = 0.016), MD (-11.48 vs. -3.04 decibel [dB], P = 0.005)… than haploinsufficiency variants" — PMID: 41944540

"Their clinical features comprise reduced visual acuity, colour vision deficits, centro-caecal scotomas and optic disc pallor with thinning of the retinal nerve fibre layer" — PMID: 37181108

Finding 7 — Genetic heterogeneity beyond OPA1

While OPA1 dominates, next-generation sequencing has identified additional DOA genes that converge on mitochondrial function. ACO2 (aconitase 2) is now "one of the most frequent causes of dominant optic atrophy" (55 patients/37 families; median BCVA 0.46 logMAR). SSBP1 (p.Arg38Gln) causes DOA-plus-foveopathy with incomplete penetrance. OPA3 causes autosomal-recessive Costeff syndrome (optic atrophy + 3-methylglutaconic aciduria, ataxia, chorea, spastic paraparesis), near-exclusive to Iraqi-Jewish descent (founder mutation), and rare ADOA. Dominant WFS1 variants cause optic atrophy with low-frequency sensorineural hearing loss (median optic-atrophy diagnosis age 10 years). Additional genes include DNM1L and MFN2.

"Aconitase 2 (ACO2) gene variants are one of the most frequent causes of dominant optic atrophy (DOA)" — PMID: 41954904

"Dominant optic atrophy (DOA) is genetically heterogeneous and most commonly caused by mutations in OPA1" — PMID: 34548540

"identification of the disease-causing mutation in the OPA3 gene" — PMID: 25201222

Finding 8 — No approved therapy; gene-modulation/antisense and neuroprotection lead the pipeline

There is currently no curative therapy for ADOA. Strategies span prevention, compensation (neuroprotection), replacement (gene augmentation), and repair. Idebenone (approved for LHON) is being explored in DOA. For ADOA specifically, antisense therapies targeting OPA1 haploinsufficiency are among the most advanced approaches "currently under human safety evaluation," and early-phase trials use variant-agnostic gene-expression modulation. Because a substantial fraction of RGC loss may be developmental, late-stage intervention efficacy could be limited — a key uncertainty for trial design.

"Antisense therapies targeting OPA1 haploinsufficiency are among the more advanced ADOA treatments currently under human safety evaluation" — PMID: 42101483

"Early phase clinical trials are underway for ADOA caused by variants in the nuclear gene OPA1 using innovative techniques to modulate gene expression in a variant-agnostic manner" — PMID: 41318849

"There is currently only one approved treatment and no curative therapy is available" — PMID: 37181108

Finding 9 — Incomplete penetrance and variable expressivity are modulated by mtDNA background and secondary alleles

Both OPA1-positive and OPA1-negative DOA families exhibit variable expressivity and incomplete penetrance (classically ~88% for OPA1). Mitochondrial DNA haplotype acts as a genetic modifier: haplogroup J was three-fold over-represented among OPA1-negative patients. In compound/biallelic cases, a second hypomorphic OPA1 allele "considered asymptomatic by itself" can act as a phenotypic modifier, producing severe early-onset Behr-like disease. Missense/GTPase-domain alleles increase both syndromic risk and structural/functional severity.

"Both OPA1-positive and OPA1-negative families exhibit variable expressivity and incomplete penetrance" — PMID: 16617242

"haplogroup J was three-fold over-represented in OPA1-negative patients" — PMID: 16617242

"the second is considered asymptomatic by itself but has been reported in patients with DOA phenotype and is presumed to act as a phenotypic modifier" — PMID: 35741767

Finding 10 — Conserved cross-species RGC-selective mitochondrial pathology

Multiple in vivo models reproduce OPA1/Opa1 disease with conserved features. The zebrafish Opa1 knockout — the first developmentally viable vertebrate Opa1 KO — and a Drosophila model both show reduced survival but viable larvae with impaired visual (not locomotor) function, mitochondrial fragmentation, and disordered cristae in neuronal axons. A naturally occurring/engineered rhesus macaque ADOA model has also been reported. Retinal neurons are "particularly sensitive to Opa1 loss," confirming conserved RGC vulnerability.

"zebrafish Opa1 KO larvae show impaired visual function but unchanged locomotor function, indicating that retinal neurons are particularly sensitive to Opa1 loss" — PMID: 40202868

"mitochondrial fragmentation and disordered cristae organization were observed in neuronal axons in both models highlighting Opa1's highly conserved role in regulating mitochondrial morphology and function in neuronal axons" — PMID: 40202868

Finding 11 — OPA1 requires balanced proteolytic processing (l-OPA1/s-OPA1); stress tips the balance to fragmentation

Inner-membrane-anchored long OPA1 (l-OPA1) is constitutively cleaved by the proteases YME1L (site S2) and OMA1 (site S1) to yield short OPA1 (s-OPA1); balanced accumulation of both forms maintains fusion. Under mitochondrial stress (membrane depolarization, low ATP), OMA1 is activated and converts OPA1 completely to short isoforms, inhibiting fusion and triggering fragmentation. This proteolytic switch is a plausible amplifier that tips already-haploinsufficient RGC mitochondria over the edge, and identifies OMA1 as a candidate therapeutic target.

"Constitutive OPA1 cleavage by YME1L and OMA1 at two distinct sites leads to the accumulation of both long and short forms of OPA1 and maintains mitochondrial fusion. Stress-induced OPA1 processing by OMA1 converts OPA1 completely into short isoforms, inhibits fusion, and triggers mitochondrial fragmentation." — PMID: 24616225

"Inner membrane-anchored long forms of OPA1 (l-OPA1) are proteolytically processed by the OMA1 or YME1L proteases, acting at cleavage sites S1 and S2, respectively, to produce short forms (s-OPA1)" — PMID: 33237841

Finding 12 — OPA1 independently gates apoptosis by sequestering cytochrome c at cristae junctions

Beyond fusion, OPA1 protects against apoptosis by controlling cristae-junction shape. OPA1 oligomers — of a soluble intermembrane-space form and an integral inner-membrane form — keep cristae junctions tight, sequestering cytochrome c within the cristae. The pro-apoptotic BID widens junctions and disrupts these oligomers, releasing cytochrome c. This anti-apoptotic function is "genetically and molecularly distinct" from OPA1's fusion role, and proper processing (e.g., by the rhomboid protease PARL) is required: Parl-/- mitochondria undergo faster cristae remodeling and cytochrome c release. Reduced OPA1 therefore lowers the apoptotic threshold of RGCs independently of any fusion defect.

"Optic Atrophy 1 (OPA1)… protects from apoptosis by preventing cytochrome c release independently from mitochondrial fusion" — PMID: 16839885

"it controls the shape of mitochondrial cristae, keeping their junctions tight during apoptosis. Tightness of cristae junctions correlates with oligomerization of two forms of OPA1" — PMID: 16839885

"Parl-/- mitochondria undergo faster apoptotic cristae remodeling and cytochrome c release" — PMID: 16839884

Finding 13 — RGC selective vulnerability arises from papillomacular-bundle anatomy and energetics

DOA (Kjer disease) and LHON share selective loss of the smallest RGC axons of the papillomacular bundle, producing central vision loss. This vulnerability reflects anatomical peculiarities: an asymmetric myelination pattern (long unmyelinated prelaminar segments with high metabolic demand) and a differential mitochondrial gradient at the lamina cribrosa, together with dependence on axonal transport and cytoskeleton. Importantly, the trigger for RGC loss is "much more complex than a simple bioenergetic crisis," involving mitochondrial network dynamics, mtDNA maintenance, and axonal transport — and is modulated by the local cellular milieu and exogenous factors (e.g., mitochondrial toxins).

"Both disorders share striking pathological similarities, marked by the selective loss of retinal ganglion cells (RGCs) and the early involvement of the papillomacular bundle" — PMID: 21112411

"the trigger for RGC loss is much more complex than a simple bioenergetic crisis and other important disease mechanisms have emerged relating to mitochondrial network dynamics, mtDNA maintenance, axonal transport, and the involvement of the cytoskeleton in maintaining a differential mitochondrial gradient at sites such as the lamina cribosa" — PMID: 21112411

"Selective degeneration of the smallest fibers (papillo-macular bundle) of the human optic nerve occurs in a large number of optic neuropathies characterized primarily by loss of central vision" — PMID: 11850115

Mechanistic Model / Interpretation

Causal chain (initiating lesion → clinical manifestation)

Heterozygous OPA1 mutation → ~50% reduction in functional OPA1 protein (haploinsufficiency), or a dominant-negative missense product. (demonstrated — PMID 27860320, 18158317)
Reduced/mutant OPA1 → impaired inner-membrane fusion + disordered cristae architecture. (demonstrated in patient fibroblasts — PMID 22800932, 33340656)
In parallel, reduced OPA1 → loosened cristae junctions, lowering the apoptotic threshold by making cytochrome c more releasable — a fusion-independent branch. (demonstrated in vitro — PMID 16839885, 16839884)
For dominant-negative alleles → mtDNA instability / multiple deletions in post-mitotic tissue → OXPHOS decline (DOA-plus branch). (demonstrated in muscle — PMID 18158317)
Metabolic/oxidative stress → OMA1 activation → complete conversion of l-OPA1 to s-OPA1 → mitochondrial fragmentation (a stress-gated amplifier). (demonstrated in vitro; inferred in RGCs — PMID 24616225, 33237841)
Steps 2–5 converge on energetic + apoptotic vulnerability of RGCs, most acutely in the smallest unmyelinated papillomacular-bundle axons with high metabolic demand and a steep mitochondrial gradient at the lamina cribrosa. (anatomy demonstrated; RGC mechanism inferred — PMID 21112411, 11850115)
→ RGC dendritic pruning, synaptic loss, and apoptosis. (demonstrated in mouse — PMID 22300878, 32561926)
→ Optic-nerve axonal degeneration and RNFL/GCL thinning → central visual loss, dyschromatopsia, centrocecal scotoma, temporal disc pallor. (demonstrated clinically — PMID 37181108, 41944540)

 OPA1 mutation (3q29, heterozygous)
│
├── LoF / unstable transcript ──► ~50% OPA1 protein (HAPLOINSUFFICIENCY)
│                                        │
└── Missense (GTPase/BSE) ──► dominant-negative ──► mtDNA instability (deletions)
                                 │                     │  (DOA-plus branch)
                                 ▼                     ▼
              ┌─────────────────────────────────────────────┐
              │  Impaired inner-membrane fusion              │
              │  Disordered cristae architecture             │
              │  Loosened cristae junctions (↓cyt-c hold)    │
              │  ↓ OXPHOS reserve                            │
              └─────────────────────────────────────────────┘
                                 │
    metabolic / oxidative stress ─► OMA1 activation
                                 │  (l-OPA1 → s-OPA1, fragmentation)
                                 ▼
     SELECTIVE VULNERABILITY of small unmyelinated papillomacular RGC axons
     (high energy demand; mitochondrial gradient at lamina cribrosa)
                                 │
 RGC dendritic pruning ► synaptic loss ► apoptosis (cyt-c/caspase)
                                 │
    Optic-nerve degeneration ► RNFL/GCL thinning
                                 │
Central visual loss · dyschromatopsia · centrocecal scotoma · temporal disc pallor

Upstream vs downstream: OPA1 dosage/processing is upstream; RGC apoptosis and vision loss are downstream. The apoptotic (cristae-junction) and fusion branches are molecularly distinct; the OMA1 switch is a stress-gated amplifier. Ontology anchors: biological processes — mitochondrial fusion (GO:0008053), cristae formation (GO:0042407), OXPHOS (GO:0006119), intrinsic apoptosis (GO:0006915), mtDNA maintenance (GO:0000002); cell type — retinal ganglion cell (CL:0000740); compartments — mitochondrial inner membrane (GO:0005743), cristae (GO:0030061), intermembrane space (GO:0005758); protein — OPA1 (UniProt O60313), OMA1 (Q96E52), YME1L1 (Q96TA2).

Section-by-Section Disease Dossier

1. Disease Information

ADOA is a slowly progressive, bilateral, symmetric optic neuropathy caused by selective degeneration of retinal ganglion cells, presenting in childhood with central visual loss, dyschromatopsia, and temporal optic-disc pallor. Identifiers: MONDO:0008134; OMIM #165500; Orphanet ORPHA:98673 (isolated), ORPHA:1215 (DOA-plus); ICD-10 H47.2; ICD-11 9C40.0; MeSH D029242. Synonyms: Kjer-type optic atrophy, Kjer optic atrophy, dominant optic atrophy (DOA), optic atrophy type 1 (OPA1), autosomal dominant optic atrophy and deafness (DOAD, for DOA-plus). Information here is derived from aggregated, disease-level resources (OMIM, Orphanet, the OPA1 Variome of 831 patients/516 variants, and cohort/natural-history studies), not from individual EHR data.

2. Etiology

Primary cause: heterozygous pathogenic variants in OPA1 (most commonly haploinsufficiency; missense/GTPase alleles dominant-negative). Genetic risk factors: OPA1 causal variants (516 catalogued); additional genes ACO2, OPA3, SSBP1, WFS1, DNM1L, MFN2; modifiers include mtDNA haplogroup (J over-represented in OPA1-negative disease) and secondary hypomorphic OPA1 alleles. Environmental risk factors / triggers: because RGC survival is energetically marginal, mitochondrial toxins and stressors (tobacco, alcohol, and drugs impairing OXPHOS) are plausible aggravators, mirroring LHON; formal ADOA-specific evidence is limited. Protective factors: none genetically established; avoidance of mitochondrial toxins is prudent. Gene–environment interaction: OPA1 dosage sets a low reserve; environmental/metabolic stress (via OMA1 activation) can tip mitochondria into fragmentation (Findings 11, 13).

3. Phenotypes

Phenotype	HPO term	Type	Onset	Severity/Course	Frequency
Optic atrophy / temporal disc pallor	HP:0000648	Clinical sign	Childhood	Progressive	~100%
Reduced visual acuity	HP:0007663	Symptom	1st decade (median ~6 y)	Mild→severe, very slow	~100%
Colour-vision defect (tritan/blue-yellow)	HP:0000551 / HP:0500020	Symptom	Childhood	Stable–progressive	Common
Centrocecal / central scotoma	HP:0000575 / HP:0030532	Sign	Childhood	Progressive	Common
RNFL / ganglion-cell-layer thinning (OCT)	HP:0007766	Lab/imaging	Childhood	Progressive	~100%
Sensorineural hearing loss (DOA-plus)	HP:0000407	Sign	Late childhood/adult	Progressive	Subset of ~20%
Progressive external ophthalmoplegia (DOA-plus)	HP:0000590	Sign	3rd decade+	Progressive	DOA-plus
Ataxia / myopathy / peripheral neuropathy (DOA-plus)	HP:0001251 / HP:0003198 / HP:0009830	Signs	Adult	Progressive	DOA-plus

Incomplete penetrance (HP:0003829, ~88%) and variable expressivity (HP:0003828). Quality of life: central-vision loss impairs reading, driving, education/employment, and face recognition; peripheral field is spared, so mobility is often preserved. Many reach low-vision/legal-blindness thresholds but rarely total blindness.

4. Genetic/Molecular Information

Causal gene: OPA1 (HGNC:8140; NCBI Gene 4976; 3q29; OMIM 605290). Variant classes: predominantly loss-of-function (nonsense, frameshift, splice-site) yielding unstable transcripts → haploinsufficiency (~76% of pathogenic alleles); missense (often GTPase/BSE domains) act dominant-negatively. Classification per ACMG/AMP; ClinVar and the OPA1 Variome are primary references (>80% of the 516 variants pathogenic). Allele frequency: individually rare in gnomAD (consistent with a Mendelian disease). Origin: germline; de novo cases occur. Functional consequences: loss of function (haploinsufficiency) and dominant-negative (mtDNA instability). Modifier genes/alleles: mtDNA haplogroup; secondary OPA1 hypomorphs. Other genes: ACO2, OPA3, SSBP1, WFS1, DNM1L, MFN2. Chromosomal abnormalities / epigenetics:* not characteristic; no established primary epigenetic driver.

5. Environmental Information

No infectious agent. Environmental contribution is limited to mitochondrial-toxic exposures — tobacco, alcohol, B-vitamin/folate deficiency, and toxins such as ethambutol, chloramphenicol, methanol, carbon monoxide, cyanide — which cause phenocopy optic neuropathies affecting the same papillomacular RGCs and may unmask/aggravate the energetically marginal ADOA phenotype (by analogy to LHON; PMID 11850115, 21112411). CHEBI anchors: ethanol (CHEBI:16236), nicotine (CHEBI:18723), ethambutol (CHEBI:4877).

6. Mechanism / Pathophysiology

See the Mechanistic Model / Interpretation section above for the full ordered causal chain, branch structure, and ontology anchors. In brief: OPA1 dosage loss → impaired fusion + disordered cristae + lowered apoptotic threshold (+ mtDNA instability for dominant-negative alleles) → stress-gated OMA1 fragmentation → selective papillomacular RGC apoptosis → optic-nerve atrophy → central vision loss.

7. Anatomical Structures Affected

Primary organ: eye — retina and optic nerve (UBERON:0000970 eye; UBERON:0000966 retina; UBERON:0001791 retinal ganglion cell layer; UBERON:0000941 optic nerve). Cell/tissue: retinal ganglion cells (CL:0000740), especially small papillomacular-bundle axons; inner plexiform-layer synapses. Secondary (DOA-plus): cochlea/auditory nerve, cerebellum, skeletal muscle, peripheral nerve, extraocular muscles. Subcellular: mitochondrion (inner membrane/cristae/intermembrane space). Lateralization: bilateral and symmetric.

8. Temporal Development

Onset: childhood/first decade (median ~6 y; range early childhood–adult), insidious/chronic. Progression: very slow and progressive, often plateauing; acuity decline ~0.022 LogMAR/yr (not significantly different from zero). Course: chronic, lifelong, irreversible; largely non-remitting (occasional stepwise worsening). DOA-plus features emerge later (deafness in late childhood; PEO/ataxia from the 3rd decade). Critical period: a developmental component of RGC loss suggests earliest intervention may be most effective (relevant to gene-therapy timing).

9. Inheritance and Population

Prevalence: ~2.87/100,000 (north England, minimum); higher in Denmark (~1:10,000, founder effect). Inheritance: autosomal dominant (OPA1); rare AR/biallelic forms cause severe Behr-like disease. Penetrance: incomplete (~88%), age-dependent. Expressivity: highly variable. Modifiers: mtDNA haplogroup J; secondary OPA1 alleles. Anticipation: not a repeat-expansion disorder; not characteristic. Founder effects: Danish (OPA1); Iraqi-Jewish (OPA3/Costeff). Sex ratio: roughly equal, no strong bias. Detection: OPA1 found in 57.6% of familial vs 14.0% of singleton probands. Age distribution: presents in childhood, diagnosed across the lifespan.

10. Diagnostics

Ophthalmic/functional: best-corrected visual acuity; colour vision (tritan defect); automated perimetry (central/centrocecal scotoma); fundoscopy (temporal disc pallor). Imaging biomarker: SD-OCT peripapillary RNFL and macular ganglion-cell-layer thinning — the key structural biomarker (~0.1 logMAR per 3.2 µm mGCL loss; missense alleles thinner pRNFL 52 vs 66 µm). Electrophysiology: pattern VEP (delayed/reduced), PERG (RGC dysfunction). Genetic testing: OPA1 sequencing + MLPA for large rearrangements, then a multigene hereditary-optic-neuropathy panel / WES for ACO2, OPA3, SSBP1, WFS1, DNM1L, MFN2; mtDNA testing to exclude LHON. Differential diagnosis: LHON (mtDNA m.11778/m.3460/m.14484; often subacute, male, central scotoma), WFS1/Wolfram (arcuate defects, later onset), POLG, glaucoma, and compressive/toxic/nutritional optic neuropathies. ADOA shows the greatest peripapillary RNFL thinning of the optic-atrophy syndromes.

11. Outcome/Prognosis

Survival: normal life expectancy in isolated DOA; DOA-plus adds neuromuscular morbidity. Visual outcome: slowly progressive, moderate-to-severe bilateral central impairment; legal blindness in a subset; total blindness rare; peripheral field usually preserved; recovery is not expected. Morbidity: central-vision disability affecting reading/driving/education. Prognostic factors: variant class (missense/GTPase → worse acuity, fields, RNFL), degree of GCL/RNFL thinning, age, and DOA-plus status. Prognostic biomarker candidate for trials: macular GCL thickness.

12. Treatment

No curative therapy. Supportive/rehabilitative: low-vision aids, occupational support, avoidance of mitochondrial toxins (tobacco/alcohol/toxic drugs), genetic counselling; audiology/neurology for DOA-plus (NCIT: supportive care C15277). Pharmacotherapy/neuroprotection: idebenone (benzoquinone electron carrier/antioxidant; NCIT:C61637; approved in LHON) explored in DOA with limited/mixed effect (mouse trial: transient optokinetic improvement, no major RGC recovery). Advanced/experimental (most promising): variant-agnostic OPA1 gene-expression modulation and antisense oligonucleotide approaches targeting haploinsufficiency, now in early-phase human safety evaluation; AAV gene augmentation, gene editing, and stem-cell optic-nerve regeneration in preclinical development. Personalized medicine: genotype (missense vs LoF) informs prognosis and potentially therapy selection.

13. Prevention

No primary prevention (Mendelian). Secondary: OCT-based early detection; cascade genetic testing of at-risk relatives. Reproductive/genetic screening: genetic counselling; prenatal/preimplantation genetic testing for known familial variants. Counselling: 50% transmission risk per offspring; counsel on incomplete penetrance, variable expressivity, and DOA-plus risk for missense/GTPase alleles. Tertiary: low-vision rehabilitation, avoid mitochondrial stressors, manage DOA-plus complications. No immunization applicable.

14. Other Species / Natural Disease

OPA1 is deeply conserved. Orthologues: mouse Opa1 (NCBI Gene 74143), zebrafish opa1 (30129), Drosophila Opa1-like. Engineered/model disease exists in mouse (Mus musculus, Taxon 10090), zebrafish (Danio rerio, 7955), fruit fly (Drosophila melanogaster, 7227), and a rhesus macaque (Macaca mulatta, 9544) ADOA model. Naturally occurring companion-animal ADOA is not a recognized veterinary entity; models are experimental. The mitochondrial fusion/cristae mechanism is evolutionarily conserved (PMID 40202868). Not zoonotic.

15. Model Organisms

Model	Type	Key phenotype recapitulated	Limitation	Resource
B6;C3-Opa1(Q285STOP) mouse	Heterozygous KO (mammalian)	RGC dendropathy, synaptic (PSD-95) loss, mitochondrial fragmentation, impaired respiration	Modest, slow visual deficit	MGI
Zebrafish opa1 KO	Vertebrate KO	Impaired visual (not locomotor) function, axonal mitochondrial fragmentation/cristae disorder	Reduced survival; developmental	ZFIN
Drosophila Opa1	Invertebrate	Conserved axonal mitochondrial pathology, reduced respiration	Anatomical divergence from human eye	FlyBase
Rhesus macaque	Primate ADOA model	Human-like ocular anatomy, translational	New/limited characterization	—
Patient fibroblasts	In vitro (human)	Fusion defect, cristae distortion, complex IV reduction	Non-neuronal	—

Recapitulation/limitations: models reproduce degenerative RGC/mitochondrial pathology and RGC-selective vulnerability, but the slow, variable human phenotype and the possible developmental RGC-loss component are captured imperfectly.

Evidence Base

PMID	Contribution	Evidence type
33340656	OPA1 as leading cause; protein biology	Review (human)
27860320	Haploinsufficiency in 76% of pathogenic alleles	Human cohort
31500643	OPA1 Variome: 516 variants, 831 patients	Database
22800932	Fusion/cristae/complex-IV defects in patient fibroblasts	In vitro (human)
18783614	OXPHOS often preserved → structural not bioenergetic primacy	In vitro (human)
20157015	DOA-plus ~20%; missense/GTPase risk ORs	Human cohort
18158317	mtDNA deletions → dominant-negative mechanism	Human tissue
32561926	Mouse RGC bioenergetic/morphological phenotype	Mouse
22300878	RGC synaptic/dendritic pathology (PSD-95)	Mouse
26820596	Idebenone RCT — limited/mixed effect	Mouse RCT
20417570	Prevalence 2.87/100,000; OPA1 detection rates	Epidemiology
40329928	Slow natural history (0.022 LogMAR/yr)	Meta-analysis
41944540	OCT biomarker; missense-vs-LoF severity	Human cohort
37181108	Clinical features; no curative therapy	Review
41954904	ACO2 as major DOA gene	Human cohort
34548540	SSBP1; genetic heterogeneity	Human cohort
25201222	OPA3/Costeff syndrome	Human cohort
16617242	Penetrance/expressivity; mtDNA haplogroup J modifier	Human cohort
35741767	Secondary OPA1 allele as phenotypic modifier	Case series
40202868	Zebrafish/Drosophila conserved RGC pathology	Model organisms
24616225	YME1L/OMA1 processing; stress fragmentation	In vitro
33237841	S1/S2 cleavage; s-OPA1 roles	In vitro
16839885	Fusion-independent anti-apoptotic role	In vitro
16839884	PARL processing required for cristae/apoptosis control	In vitro (mouse)
21112411	RGC/papillomacular selective vulnerability; multifactorial	Review
11850115	Smallest-fibre papillomacular degeneration	Review
42101483	Antisense/haploinsufficiency-targeting therapy	Review
41318849	Variant-agnostic gene-modulation trials	Review

Converging vs challenging evidence: Findings are strongly convergent across human cohorts, patient cells, and multiple animal models. The main internal tension is between the fusion/cristae paradigm (Findings 2, 11, 12) and the observation that whole-cell OXPHOS can be preserved in ADOA patient mitochondria (PMID: 18783614); this is reconciled by localizing the deficit to cristae architecture, apoptotic priming, and the energetically marginal papillomacular RGC axon rather than a global respiratory block.

Supported and Refuted Hypotheses

Supported: 1. OPA1 haploinsufficiency is the predominant cause of ADOA (PMID 27860320, 31500643, 33340656). 2. OPA1 dysfunction acts via impaired mitochondrial fusion/cristae → RGC bioenergetic failure and apoptotic priming (PMID 33340656, 22800932, 32561926, 16839885). 3. Missense/GTPase (dominant-negative) alleles cause more severe and syndromic disease via mtDNA instability (PMID 20157015, 18158317, 41944540). 4. Penetrance/expressivity are modified by mtDNA background and secondary alleles (PMID 16617242, 35741767). 5. The OMA1/YME1L proteolytic balance is a stress-gated amplifier of fragmentation (PMID 24616225, 33237841).

Refuted / nuanced: - The hypothesis that OPA1 mutations cause disease chiefly by directly impairing electron transport was not supported in one patient study (electron transport unaltered; pathology attributed to structure/fusion role) — favouring the cristae/fusion + apoptotic-priming mechanism (PMID 18783614).

Limitations and Knowledge Gaps

Developmental vs degenerative RGC loss is unresolved. If much RGC loss is developmental, post-symptomatic gene therapy may have a narrow therapeutic window — a pivotal uncertainty for trial design (Finding 8).
No human therapeutic efficacy data yet. Idebenone benefit in ADOA is inferred from LHON and mouse data; ADOA-specific RCTs are lacking. Antisense/gene-modulation approaches are only at the safety-evaluation stage.
Penetrance/modifier biology is incompletely mapped. The mechanistic basis of ~88% penetrance, mtDNA haplogroup effects, and secondary-allele modifiers is correlational, not causally dissected.
Prevalence is likely under-ascertained. The 2.87/100,000 figure is a minimum; incomplete penetrance and mild cases inflate the true carrier frequency.
Environmental triggers are hypothesized, not quantified for ADOA specifically (extrapolated from LHON).
OMA1 as a drug target (Finding 11) is mechanistically attractive but untested in ADOA models.
Literature-based synthesis without primary patient-level data; frequencies are cohort-dependent.

Proposed Follow-up Experiments / Actions

Test OMA1 inhibition (genetic or pharmacological) in Opa1+/- mouse and zebrafish models to determine whether blocking the stress-fragmentation switch preserves RGCs — a targeted extension of Findings 11 and 4.
Define the developmental window using conditional/inducible Opa1 knockdown at defined postnatal ages to quantify how much RGC loss is developmental vs adult-onset, informing gene-therapy timing.
Genotype-stratified natural-history/OCT study contrasting missense/GTPase vs LoF alleles longitudinally to build a prognostic model with macular GCL thickness as endpoint (extends Findings 6, 9).
AAV-OPA1 gene augmentation and antisense upregulation dose-ranging in the rhesus macaque model (human-like eye) as a bridge to clinical trials.
mtDNA-haplogroup modifier study in large OPA1 cohorts (cybrid experiments) to establish causality for haplogroup J and identify protective backgrounds (extends Finding 9).
Cristae-junction/apoptosis-targeted neuroprotection (e.g., stabilizing OPA1 oligomers or blocking cytochrome c release) tested in RGCs, exploiting the fusion-independent branch (Finding 12).
Systematic ADOA drug-toxicity registry to quantify environmental/pharmacological aggravators and generate evidence-based avoidance guidance (extends Finding 13).

Report compiled from 13 confirmed findings and 46 reviewed papers across five investigation iterations. Evidence types are labelled (human clinical, model organism, in vitro, database/computational). All quotations are verbatim from the cited abstracts.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	28
Resolved	28
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	28
On topic	21
Off topic	0

All extracted references resolved successfully.

Term Validation

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

Outcome	Count
Terms checked	35
Resolved	31
Unresolved (possible confabulation)	0
Obsolete	1
Unverifiable	3
Terms whose name was checked	6
Terms named correctly	1
Terms named as a different term	2
Terms whose name is worth a second look	3

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:0008134 (3 mentions) - the report calls it "if available"; MONDO calls it autosomal dominant optic atrophy, classic form
HP:0007766 (1 mention) - the report calls it "RNFL / ganglion-cell-layer thinning (OCT)"; HP calls it Optic disc hypoplasia

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:0000002 (obsolete mitochondrial genome maintenance) (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:0000648 (1 mention) - the report calls it "Optic atrophy / temporal disc pallor"; HP calls it Optic atrophy
HP:0000407 (1 mention) - the report calls it "Sensorineural hearing loss (DOA-plus)"; HP calls it Sensorineural hearing impairment, and lists "Sensorineural hearing loss" among its other names
HP:0000590 (1 mention) - the report calls it "Progressive external ophthalmoplegia (DOA-plus)"; HP calls it Progressive external ophthalmoplegia

Terms named inconsistently

The report gives these identifiers more than one name of its own:

ORPHA:98673 - called "isolated DOA", "isolated"

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.

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Mappings

Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Prevalence

Differential Diagnoses

Clinical Trials

Experimental Models

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Key Findings

Finding 1 — OPA1 haploinsufficiency is the predominant molecular cause

Finding 2 — OPA1 is a mitochondrial inner-membrane dynamin GTPase controlling fusion, cristae, and apoptosis

Finding 3 — DOA-plus (syndromic disease) affects ~20% of carriers via a dominant-negative, mtDNA-instability mechanism

Finding 4 — Mouse models recapitulate RGC dendropathy and bioenergetic failure; idebenone effect is limited

Finding 5 — Epidemiology: point prevalence ~2.87/100,000 with slow, childhood-onset progression

Finding 6 — OCT inner-retinal thinning is the key diagnostic biomarker; missense variants cause worse disease

Finding 7 — Genetic heterogeneity beyond OPA1

Finding 8 — No approved therapy; gene-modulation/antisense and neuroprotection lead the pipeline

Finding 9 — Incomplete penetrance and variable expressivity are modulated by mtDNA background and secondary alleles

Finding 10 — Conserved cross-species RGC-selective mitochondrial pathology

Finding 11 — OPA1 requires balanced proteolytic processing (l-OPA1/s-OPA1); stress tips the balance to fragmentation

Finding 12 — OPA1 independently gates apoptosis by sequestering cytochrome c at cristae junctions

Finding 13 — RGC selective vulnerability arises from papillomacular-bundle anatomy and energetics

Mechanistic Model / Interpretation

Causal chain (initiating lesion → clinical manifestation)

Section-by-Section Disease Dossier

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Evidence Base

Supported and Refuted Hypotheses

Limitations and Knowledge Gaps

Proposed Follow-up Experiments / Actions

Artifacts

Reference Validation

Term Validation

Terms the report names something else

Obsolete terms

Terms whose name is worth a second look

Terms named inconsistently

Prefixes with no resolver