Encephalopathy Due To Defective Mitochondrial And Peroxisomal Fission 2 (EMPF2)

Disease Knowledge Base Research Report MONDO:0014905 · OMIM #617086 · Orphanet 485421 · Gene: MFF (HGNC:24858)

Summary

Encephalopathy due to defective mitochondrial and peroxisomal fission 2 (EMPF2) is an ultra-rare, autosomal-recessive neurodevelopmental/neurodegenerative disorder caused by biallelic loss-of-function variants in the MFF gene (mitochondrial fission factor). MFF is the outer-membrane receptor that recruits the dynamin-related GTPase DRP1/DNM1L to the surface of mitochondria and peroxisomes to execute organelle scission. When MFF is absent, this shared fission machinery cannot be assembled, and affected cells accumulate hyper-elongated, net-like mitochondria and elongated peroxisomes. The disease was first delineated as a distinct entity by Koch and colleagues in 2016 (PMID: 26783368).

Clinically, EMPF2 presents in the first year of life with developmental delay, acquired (secondary) microcephaly, spasticity and hyperreflexia, seizures (frequently infantile spasms with hypsarrhythmia), optic atrophy, and peripheral neuropathy. Brain MRI shows a Leigh-like pattern with bilateral basal-ganglia and subthalamic-nucleus signal change, yet — in a key biochemical distinction from classic Leigh syndrome — mitochondrial respiratory-chain enzyme activities in skeletal muscle are typically normal. The disorder is closely related to and is the principal differential diagnosis of EMPF1 (caused by variants in DNM1L/DRP1), because both diseases disrupt the same fission pathway.

There is no disease-specific therapy; management is entirely supportive (seizure control, spasticity management, nutrition/feeding support, visual and physical rehabilitation). The strongest mechanistic lead toward a rational therapy comes from mouse genetics: reducing mitochondrial fusion (via Mfn1 deletion) fully rescues the Mff-null phenotype, identifying fission/fusion rebalancing as a promising therapeutic direction. Naturally occurring animal models exist in Mff-knockout mice (fatal dilated cardiomyopathy) and in Bullmastiff dogs carrying a homozygous MFF frameshift variant, providing translational platforms.

Key Findings

Finding 1 — EMPF2 is caused by biallelic loss-of-function MFF variants that disrupt DRP1-mediated fission of both mitochondria and peroxisomes

The defining discovery, by Koch et al. (2016), came from exome sequencing of index patients from two families. As the authors state, "Exome sequencing revealed three different biallelic loss-of-function variants in MFF in both index cases" (PMID: 26783368). Western blotting demonstrated absent MFF protein, and patient fibroblasts displayed elongated mitochondria and elongated peroxisomes, directly linking the genotype to an organelle-division defect.

Mechanistically, MFF is the outer-mitochondrial-membrane (and peroxisomal-membrane) receptor that recruits the fission GTPase DRP1/DNM1L. As Liu and Chan's work summarizes, "the OMM protein mitochondrial fission factor (Mff) is a key receptor for recruiting Drp1 from the cytosol to the mitochondrion" (PMID: 34347505). Because "components of the fission machinery are partly shared between mitochondria and peroxisomes" (PMID: 26783368), loss of MFF simultaneously impairs the division of both organelles — the molecular basis for the disease name.

This establishes the disease as an autosomal-recessive loss-of-function disorder confirmed across multiple unrelated patients.

Finding 2 — Core clinical phenotype: early-infantile Leigh-like encephalopathy with acquired microcephaly, seizures, spasticity, optic atrophy and peripheral neuropathy, but normal muscle respiratory-chain activity

Koch et al. describe the natural history precisely: "The patients became symptomatic within the first year of life, exhibiting seizures, developmental delay and acquired microcephaly. Dysphagia, spasticity and optic and peripheral neuropathy developed subsequently" (PMID: 26783368). Neuroimaging showed a characteristic pattern: "Brain MRI showed Leigh-like patterns with bilateral changes of the basal ganglia and subthalamic nucleus."

A crucial diagnostic distinction from classic Leigh syndrome is that "activities of mitochondrial respiratory chain complexes were found to be normal in skeletal muscle" (PMID: 26783368). This tells clinicians that a normal muscle biopsy respiratory-chain panel does not exclude EMPF2 — the disease is one of organelle morphology/dynamics, not primary OXPHOS enzyme deficiency.

An independent patient reported by Panda et al. (2020) corroborated the phenotype and added a specific pathogenic variant: an Indian child with "global developmental followed by regression of acquired milestones, spasticity, visual and auditory impairment, and was found to harbor a novel pathogenic homozygous MFF truncating variant c.433C>T; p.Arg145Ter" (PMID: 32181496).

Finding 3 — Downstream mechanism: peroxisome-maturation failure plus mitochondrial Ca²⁺ overload and oxidative stress link organelle dynamics to neuronal dysfunction

Beyond simple elongation, loss of MFF produces functional organelle defects. Passmore et al. (2020) showed that "loss of MFF results in reduced import-competence of the peroxisomal compartment and leads to the accumulation of pre-peroxisomal membrane structures" and that "peroxisomes in MFF-deficient cells display alterations in peroxisomal redox state and intra-peroxisomal pH" (PMID: 32224193). Thus MFF is a critical regulator of peroxisome maturation, not merely division.

On the mitochondrial/neuronal side, Sun et al. (2022) differentiated dopaminergic neurons from dental-pulp stem cells with MFF insufficiency and observed impaired neurite outgrowth, elongated mitochondria confined to neurites, and mitochondrial Ca²⁺-triggered oxidative stress (PMID: 35883852) — connecting the fission defect to the kind of neuronal energetic/oxidative failure that could underlie a Leigh-like phenotype.

In vivo, Chen et al. (2015) showed that "mutant tissue showed reduced mitochondrial density and respiratory chain activity along with increased mitophagy" in Mff-null mice, and — critically — that "concomitant deletion of the mitochondrial fusion gene Mfn1 completely rescued heart dysfunction, life span, and respiratory chain function" (PMID: 26598616). This demonstrates the disease is driven by a fission/fusion imbalance and is, in principle, reversible by rebalancing organelle dynamics.

Finding 4 — Naturally occurring and engineered animal models

A naturally occurring canine model was identified by Christen et al. (2022): two young Bullmastiffs with progressive gait/behavioural abnormalities (onset ~6 months) and bilateral symmetrical cerebellar-nuclei MRI lesions carried a private homozygous MFF frameshift variant. As reported, "This search revealed a private homozygous frameshift variant in the MFF gene in the affected dog" (XM_038574000.1:c.471_475delinsCGCTCT, p.(Glu158Alafs14), truncating ~55% of the ORF), with perfect autosomal-recessive segregation across 4 affected and 70 unaffected dogs. The authors explicitly connect this to the human disease: "Human patients with pathogenic MFF variants suffer from 'encephalopathy due to defective mitochondrial and peroxisomal fission 2'"* (PMID: 36085405).

The mouse knockout is more severe systemically: "Mff mutant mice die at 13 wk as a result of severe dilated cardiomyopathy leading to heart failure" (PMID: 26598616), reflecting the high energetic demand of cardiac tissue.

Finding 5 — MFF is a physiological AMPK substrate coupling energy stress to fission

MFF sits at a regulatory node linking cellular energy status to mitochondrial dynamics. Zong et al. (2019) showed that "mitochondrion-localized AMPK is activated to phosphorylate ACC2 and mitochondrial fission factor (MFF) only during severe nutrient stress" (PMID: 30948787). Peng et al. (2022) confirmed that "the AMPK pathway promoted mitochondrial fission and mitophagy by increasing the recruitment of dynamin-related protein 1 (DRP1) to the mitochondrial outer membrane" (PMID: 36374514). This AMPK→MFF→DRP1 axis is precisely the function lost in EMPF2, and it frames why energy-stressed neurons might be especially vulnerable.

Finding 6 — EMPF2 is the recessive counterpart of EMPF1 (DNM1L/DRP1)

EMPF2 and EMPF1 disrupt the same fission pathway at adjacent steps (receptor vs. effector GTPase). Keller/Verrigni et al. note that "Autosomal dominant and recessive variants in DNM1L cause encephalopathy due to defective mitochondrial and peroxisomal fission 1 (EMPF1), which presents as a complex and clinically heterogeneous neurological disorder of variable severity, often accompanied by seizures" (PMID: 33387674). DRP1's role is confirmed: it is "a cytosolic protein encoded by dynamin 1-like (DNM1L) gene, which relocalizes to the outer mitochondrial membrane, where it assembles, oligomerizes and drives mitochondrial division" (PMID: 31868880). EMPF1 is therefore the primary genetic differential diagnosis of EMPF2.

Finding 7 — Verified identifiers and cross-references

The RefSeq summary states the encoded protein "recruits dynamin-1-like protein (DNM1L) to mitochondria." Multiple splice transcript variants and processed pseudogenes (chr 1, 5, X) exist.

Finding 8 — Quantitative HPO phenotype spectrum and frequencies

Curated HPO annotations for OMIM:617086 / MONDO:0014905 (primary source PMID: 26783368, n=4 patients unless noted):

Finding 9 — ClinVar variant spectrum supports the loss-of-function mechanism

A ClinVar query (2026) returned ~251 MFF variant records, of which 58 are classified Pathogenic/Likely-pathogenic. The gene-specific P/LP variants are predominantly loss-of-function: splice-site (e.g., NM_001277062.2:c.181+2T>A, c.352-2A>C, deep-intronic c.440+2432G>T, c.-40-842G>T), frameshift (c.159del p.Pro54fs), and truncating changes such as c.433C>T (p.Arg145Ter). By contrast, reported missense variants (c.226C>G p.Leu76Val; c.611G>A p.Arg204His; c.382C>T p.Arg128Trp; c.223G>A p.Asp75Asn) are largely classified as Variants of Uncertain Significance (VUS). Several "Pathogenic" entries are large 2q chromosomal copy-number gains that merely overlap MFF and are not EMPF2-causing. This distribution is consistent with a haploinsufficiency/loss-of-function disease requiring biallelic null or near-null alleles.

Mechanistic Model / Interpretation

Ordered causal chain (initiating lesion → clinical manifestation)

1. Biallelic loss-of-function variant in MFF (nonsense, frameshift, splice-site, or deletion) → absent or non-functional MFF protein (demonstrated: Western blot shows absent protein — 26783368).
2. Absent MFF → failure to recruit the DRP1/DNM1L GTPase to the outer membranes of mitochondria and peroxisomes (mechanistically established; MFF is the DRP1 receptor — 34347505).
3. No DRP1 recruitment → no assembly of the scission machinery → organelle fission arrest → hyper-elongated, net-like mitochondria and elongated peroxisomes (demonstrated in patient fibroblasts — 26783368).
4. Branch A (peroxisome): fission arrest → reduced peroxisomal import-competence, accumulation of pre-peroxisomal membrane structures, and altered redox state / intra-peroxisomal pH → impaired peroxisomal metabolism (demonstrated — 32224193).
5. Branch B (mitochondria): fission arrest → impaired mitochondrial quality control (mitophagy dysregulation), reduced mitochondrial density and respiratory-chain activity in high-demand tissue, mitochondrial Ca²⁺ overload and oxidative stress (demonstrated in vivo, 26598616; and in dopaminergic neurons, 35883852).
6. Branches converge → energetic and oxidative failure of neurons, particularly in metabolically demanding basal ganglia, subthalamic nucleus, optic and peripheral nerves → neuronal dysfunction and neurodegeneration (inferred from imaging + cellular data).
7. Neuronal injury → clinical phenotype: developmental delay/regression, acquired microcephaly, spasticity, seizures, optic atrophy, peripheral neuropathy, Leigh-like MRI (demonstrated clinically — 26783368, 32181496).

Notably, because the primary lesion is one of organelle morphology/dynamics rather than primary OXPHOS enzymology, skeletal-muscle respiratory-chain activities are typically normal — a diagnostic hallmark.

Schematic

   MFF (biallelic LoF)
        │  no receptor
        ▼
   DRP1/DNM1L not recruited to OMM/peroxisomal membrane
        │
        ▼
   Fission machinery cannot assemble → SCISSION ARREST
        │
        ├──────────────► Peroxisomes: elongated, immature,
        │                 impaired import, altered redox/pH
        │
        └──────────────► Mitochondria: hyper-elongated network,
                          dysregulated mitophagy, Ca²⁺ overload, ROS↑
                                   │
                                   ▼
                 Neuronal energetic/oxidative failure
                 (basal ganglia, subthalamic nucleus, optic/peripheral nerve)
                                   │
                                   ▼
      Leigh-like encephalopathy: delay/regression, microcephaly,
      spasticity, seizures, optic atrophy, peripheral neuropathy

Regulatory context and therapeutic logic

MFF is a physiological AMPK substrate (30948787, 36374514): energy stress activates AMPK, which phosphorylates MFF to drive DRP1 recruitment, fission and mitophagy. EMPF2 removes this node entirely. The single most actionable mechanistic insight is that shifting the fission/fusion balance back toward fission-competence rescues the phenotype in vivo — deletion of the fusion gene Mfn1 completely rescued Mff-null mice (26598616). This nominates pharmacological or genetic fusion inhibition / fission promotion as a rational (though still preclinical) therapeutic strategy.

Ontology annotations

• Genes/proteins: MFF (HGNC:24858), DNM1L/DRP1 (differential), MFN1 (modifier).
• GO biological process: mitochondrial fission (GO:0000266), peroxisome fission (GO:0016559), mitochondrion organization (GO:0007005), mitophagy (GO:0000422), regulation of mitochondrial fission (GO:0090140).
• GO cellular component: mitochondrial outer membrane (GO:0005741), peroxisomal membrane (GO:0005778), mitochondrion (GO:0005739), peroxisome (GO:0005777).
• Cell types (CL): neuron (CL:0000540), dopaminergic neuron (CL:0000700), cardiac muscle cell (CL:0000746, model), fibroblast (CL:0000057, patient cells).
• UBERON: basal ganglia (UBERON:0002420), subthalamic nucleus (UBERON:0001906), cerebellum (UBERON:0002037), optic nerve (UBERON:0000941), peripheral nervous system (UBERON:0000010), brain (UBERON:0000955).
• CHEBI (relevant chemistry): calcium(2+) (CHEBI:29108), reactive oxygen species (CHEBI:26523).

Section-by-Section Report

1. Disease Information

EMPF2 is an ultra-rare autosomal-recessive mitochondrial/peroxisomal dynamics disorder producing an early-infantile Leigh-like encephalopathy. Identifiers: MONDO:0014905, OMIM #617086, ORPHA:485421, DOID:0060994, GARD 0017881, MedGen 934693, UMLS C4310726. There is no dedicated ICD-10 code; it maps to mitochondrial/metabolic encephalopathy categories (e.g., ICD-10 G31.8 / E88.4x class). Synonyms: "EMPF2," "MFF-related encephalopathy," and the ontology synonym "Leigh-like basal ganglia disease–optic atrophy–peripheral neuropathy syndrome." The knowledge base here is derived from aggregated disease-level resources (OMIM, Orphanet, HPO, ClinVar) plus a small number of individual published patient reports (26783368, 32181496), not EHR-scale data.

2. Etiology

Causal factor: purely genetic — biallelic loss-of-function variants in MFF (26783368). Genetic risk factors: the causal variants themselves; carrier parents are unaffected. Modifier genes: experimentally, MFN1 (fusion) modifies severity (rescue in mouse — 26598616); DRP1/DNM1L and PEX11 proteins act in the same pathway. Environmental/lifestyle/infectious factors and protective factors: none established; consanguinity increases risk of recessive homozygosity. Gene–environment interactions: none demonstrated; the AMPK–MFF energy-sensing axis (30948787) suggests, hypothetically, that metabolic/energy stress could modulate residual pathway output, but this is not clinically shown.

3. Phenotypes

See Finding 8 for the full HPO frequency table. Phenotypes are predominantly neurological signs and physical manifestations (spasticity, hyperreflexia, microcephaly, ophthalmoplegia, optic atrophy) plus developmental/behavioral features (developmental delay/regression, absent speech). Onset is infantile (first year of life), severity is severe, and course is progressive with regression. Quality-of-life impact is profound: affected children have major motor disability (often inability to walk), feeding difficulty (dysphagia requiring support), visual/auditory impairment, and seizures — a globally dependent care status.

4. Genetic/Molecular Information

Causal gene: MFF (2q36.3; NCBI Gene 56947; gene OMIM 614785). Variant classes: predominantly nonsense/frameshift/splice-site loss-of-function (e.g., c.433C>T p.Arg145Ter — 32181496; c.159del p.Pro54fs; splice variants c.181+2T>A, c.352-2A>C). ACMG classification: null variants are Pathogenic/Likely-pathogenic; missense variants are largely VUS (Finding 9). Allele frequency: causal alleles are extremely rare/private in gnomAD, consistent with an ultra-rare recessive disease. Origin: germline. Functional consequence: loss of function / haploinsufficiency requiring biallelic hits. Epigenetics/chromosomal abnormalities: none specific to EMPF2; large 2q copy-number gains overlapping MFF in ClinVar are incidental and not disease-causing.

5. Environmental Information

Not applicable — EMPF2 is a monogenic disorder with no established environmental, lifestyle, or infectious contributors. (Note: the environmental-toxin paper 41296099 concerns Drp1/MFF upregulation in fluorine/aluminium neurotoxicity, a distinct context, not EMPF2 causation.)

6. Mechanism / Pathophysiology

See the ordered causal chain and schematic above. Upstream lesion: MFF loss → failed DRP1 recruitment → fission arrest. Downstream: peroxisome maturation failure (32224193) and mitochondrial Ca²⁺ overload/oxidative stress/mitophagy dysregulation (35883852, 26598616), converging on neuronal energetic failure. Key regulatory pathway: AMPK→MFF→DRP1 (30948787, 36374514). Cell types: neurons (esp. dopaminergic and basal-ganglia neurons), with cardiomyocyte involvement in the mouse model.

7. Anatomical Structures Affected

Primary organ: brain — basal ganglia (UBERON:0002420) and subthalamic nucleus (UBERON:0001906), with Leigh-like bilateral (symmetric) involvement; cerebellar atrophy in some. Secondary/associated: optic nerve (optic atrophy), peripheral nerves (neuropathy). Body system: central and peripheral nervous system. Subcellular: mitochondrial outer membrane (GO:0005741) and peroxisomal membrane (GO:0005778). Lateralization: bilateral/symmetric CNS lesions. The mouse model additionally shows cardiac involvement (dilated cardiomyopathy), not prominent in human patients.

8. Temporal Development

Onset: infantile, within the first year of life (HP:0003593), congenital-to-early-infantile. Pattern: insidious then progressive with developmental regression. Course: progressive neurodegeneration; lifelong. Critical period: infancy/early childhood is the window of rapid deterioration; no established intervention window given lack of therapy. Death in childhood occurs in a subset (1/4 in the index series).

9. Inheritance and Population

Inheritance: autosomal recessive (HP:0000007; 26783368, original locus 22499341). Penetrance: presumed complete for biallelic LoF. Expressivity: variable in severity and survival. Epidemiology: ultra-rare — only a handful of published families worldwide; prevalence not formally estimated (well below Orphanet's <1/1,000,000 threshold). Consanguinity: relevant (homozygous truncating variants reported in consanguineous/related settings, e.g., 32181496). Founder effects/carrier frequency: none established. Sex ratio: no sex bias expected (autosomal). No specific ethnic predilection established.

10. Diagnostics

Genetic testing is definitive: WES/WGS or targeted MFF sequencing identifying biallelic LoF variants (26783368). Supportive tests: brain MRI (Leigh-like bilateral basal-ganglia/subthalamic signal); patient-fibroblast microscopy showing elongated mitochondria and peroxisomes; nerve conduction studies (peripheral neuropathy); EEG (hypsarrhythmia/epileptic spasms); ophthalmologic exam (optic atrophy/pallor). Key negative: skeletal-muscle respiratory-chain enzyme activities are typically normal, distinguishing EMPF2 from classic Leigh syndrome (26783368). Differential diagnosis: EMPF1 (DNM1L/DRP1; 33387674), classic mitochondrial Leigh syndrome (with abnormal OXPHOS), peroxisomal biogenesis disorders. Genetic testing distinguishes these. Screening: carrier/cascade testing within affected families; prenatal testing when the familial variants are known.

11. Outcome / Prognosis

Prognosis is poor: severe, progressive neurodevelopmental disability with regression, inability to walk, dysphagia, seizures, and sensory/visual loss; childhood death occurs in a subset. There are no formal survival statistics given rarity. Prognostic factors are not formally validated but likely relate to variant severity (complete null vs. hypomorphic) and seizure burden. Recovery potential is minimal; care is supportive.

12. Treatment

No disease-specific or curative therapy exists. Management is supportive and symptomatic: anti-seizure medication (including for infantile spasms; NCIT: Anticonvulsant Agent), spasticity management (e.g., baclofen; physical therapy), nutritional/feeding support for dysphagia (gastrostomy where needed), visual and developmental rehabilitation (physical, occupational, speech therapy). Rational future directions (preclinical only): fission/fusion rebalancing — the Mfn1-deletion rescue in mice (26598616) suggests fusion inhibition could be therapeutic; antioxidant strategies targeting mitochondrial Ca²⁺/ROS are hypothesis-generating from the dopaminergic-neuron model (35883852). No approved gene, cell, or RNA therapies. Pharmacogenomics: not applicable.

13. Prevention

No primary prevention exists for this monogenic disease. Genetic counseling is central: recurrence risk is 25% for carrier couples. Reproductive options: carrier/cascade screening in affected families, prenatal diagnosis, and preimplantation genetic testing (PGT-M) when the familial MFF variants are known. No immunization, behavioral, or public-health interventions apply. Tertiary prevention = optimized supportive care to limit complications (aspiration, seizure-related injury, contractures).

14. Other Species / Natural Disease

Naturally occurring canine disease: Bullmastiff dogs with a homozygous MFF frameshift (p.Glu158Alafs14) develop a progressive encephalopathy with bilateral symmetric cerebellar-nuclei lesions, explicitly linked to human EMPF2 (36085405). Species/orthologs: MFF is conserved; mouse Mff, dog MFF. Comparative pathology: dogs show cerebellar-nuclei predominant lesions; mice (Mff-null) die of dilated cardiomyopathy at ~13 weeks (26598616) — highlighting species-specific tissue vulnerability (cardiac in mouse, CNS in human/dog). Zoonotic potential:* none (genetic disease).

15. Model Organisms

Mouse: constitutive and cardiac Mff knockouts — robust model of fission failure, fatal dilated cardiomyopathy, reduced respiratory-chain activity, increased mitophagy; the Mff/Mfn1 double-knockout provides proof-of-concept rescue (26598616). Dog: spontaneous Bullmastiff model (36085405). Cellular/in vitro: patient fibroblasts (elongated organelles — 26783368); iPSC/dental-pulp-derived dopaminergic neurons with MFF knockdown recapitulating neurite/Ca²⁺/ROS defects (35883852). Phenotype recapitulation: cellular and canine models capture the fission defect and CNS phenotype well; the mouse captures the biochemistry and rescue paradigm but emphasizes cardiac (not encephalopathic) lethality — its main limitation for modeling the human neurological disease.

Evidence Base

Supporting/contextual references also reviewed: peroxisome division/pexophagy reviews (26434997; 22595523) and muscle-BDNF/AMPK–DRP1–MFF signaling (34689722).

Limitations and Knowledge Gaps

• Extreme rarity / small n. The core clinical picture and all HPO frequencies derive from a handful of patients (n=4 index series plus isolated case reports). Frequencies (e.g., "4/4 spasticity") are statistically fragile and may not generalize.
• No epidemiological estimates. Prevalence, incidence, carrier frequency, sex ratio, and geographic distribution are unquantified.
• Genotype–phenotype correlation unestablished. Too few variants to correlate variant type/position with severity or survival.
• VUS burden. Most reported missense MFF variants are of uncertain significance; functional assays are needed to classify them.
• Mechanistic inference. The link from organelle-level defects to specific neuronal death in basal ganglia is inferred from cellular/animal models, not directly demonstrated in patient brain.
• Model mismatch. The mouse knockout's lethal phenotype is cardiac, not encephalopathic, limiting its face validity for the human neurological disease.
• No therapeutic trials. Fission/fusion rebalancing is proof-of-concept in mice only; no human or even neuronal-model therapeutic data exist.
• No natural-history study. Longitudinal course, survival curves, and prognostic biomarkers are undefined.

Proposed Follow-up Experiments / Actions

1. Establish an international patient registry / GeneMatcher-driven cohort to expand n, quantify HPO frequencies robustly, define natural history and survival, and enable genotype–phenotype analysis.
2. Functional classification of MFF VUS using patient-fibroblast or knockout-cell complementation assays (mitochondrial/peroxisomal morphology, DRP1 recruitment) to reclassify uncertain missense variants per ACMG PS3/BS3.
3. Test fission/fusion rebalancing in a neuronal model. Apply MFN1/2 knockdown or pharmacological fusion modulation to MFF-deficient iPSC-derived neurons (extending 35883852) to determine whether the mouse cardiac rescue (26598616) translates to neurons.
4. Antioxidant / mitochondrial-Ca²⁺ modulation in the dopaminergic-neuron model to test whether buffering Ca²⁺/ROS restores neurite outgrowth — a druggable downstream node.
5. Characterize the Bullmastiff model longitudinally (imaging, neuropathology, peroxisomal biochemistry) as a large-animal platform for preclinical therapeutics (36085405).
6. Peroxisomal biomarker discovery (plasma VLCFA, plasmalogens, bile-acid intermediates) to identify a non-genetic diagnostic/monitoring signature reflecting the peroxisome-maturation defect (32224193).
7. Brain-tissue / autopsy studies where available, to confirm the inferred causal chain from elongated organelles to regional neuronal loss.