| Aspect | Zebrafish-specific evidence | Cross-species mechanistic support | Notes/implications | Key sources (with citation IDs) |
|---|---|---|---|---|
| Protein type / identity | Zebrafish **opa1** is reported as a **single-copy, ubiquitously expressed** gene with multiple protein isoforms; the zebrafish protein is ~**78% identical** to human OPA1-4. Morphoblotting detected several Opa1 bands (~100, 85, 80, and a 78 kDa doublet), consistent with isoform complexity. CRISPR deletion of exons 8-9 generated a predicted **304 aa truncated protein** versus the **1034 aa long isoform**. (pqac-00000012, pqac-00000019) | OPA1 is a **dynamin-like GTPase** with an N-terminal mitochondrial targeting sequence/transmembrane anchor plus GTPase/dynamin/GED-related regions; structural studies support membrane-remodeling assemblies. (pqac-00000000, pqac-00000005, pqac-00000007) | Matches UniProt Q5U3A7 annotation as a mitochondrial dynamin-family GTPase and supports orthology-based functional annotation. | (pqac-00000012, pqac-00000019, pqac-00000000, pqac-00000007) |
| Subcellular localization | Zebrafish Opa1 studies interpret the protein as mitochondrial; mitochondrial matrix-targeted reporter imaging in morphants showed reduced fluorescence and fragmented mitochondria, and optic-nerve EM in CRISPR models showed axonal mitochondrial ultrastructural defects. (pqac-00000012, pqac-00000015, pqac-00000018) | OPA1 is localized to the **inner mitochondrial membrane (IMM)**, where the long form is membrane-anchored and the short form is soluble in the intermembrane space. (pqac-00000001, pqac-00000008) | Functional site is the mitochondrial inner membrane/crista junction region rather than cytosol or other organelles. | (pqac-00000015, pqac-00000001, pqac-00000008) |
| Core molecular function | Zebrafish loss-of-function causes **fragmented mitochondria**, altered mitochondrial fluorescence, and developmental bioenergetic defects, indicating a conserved role in maintaining mitochondrial morphology and metabolism. (pqac-00000012, pqac-00000013, pqac-00000016) | OPA1 mediates **IMM fusion** after MFN1/MFN2-dependent OMM fusion and also shapes/maintains **cristae**; GTP-dependent oligomerization/dimerization drives membrane curvature and fusion. (pqac-00000008, pqac-00000001, pqac-00000005) | Primary annotation: mitochondrial inner-membrane fusion/cristae organizer rather than enzyme in small-molecule metabolism. The catalytic reaction is **GTP hydrolysis** coupled to membrane remodeling. | (pqac-00000013, pqac-00000008, pqac-00000005) |
| Processing / regulation (L-Opa1 / S-Opa1) | Zebrafish morphants showed isoform-specific depletion and altered relative abundance of smaller Opa1 species, supporting regulated processing in vivo. (pqac-00000012, pqac-00000013) | OPA1 exists as **long (L-OPA1)** and **short (S-OPA1)** isoforms; **OMA1** cleaves at S1 and **YME1L** at S2. Balanced L/S forms are required for efficient fusion and cristae organization; stress increases OMA1-dependent cleavage and fragmentation. (pqac-00000000, pqac-00000001, pqac-00000006, pqac-00000008) | Even where zebrafish cleavage-site mapping is incomplete, family-level conservation strongly supports the same regulatory logic for Q5U3A7. | (pqac-00000012, pqac-00000000, pqac-00000006, pqac-00000008) |
| Cristae organization | In zebrafish optic-nerve axons, Opa1 deficiency caused **disordered cristae organization** by EM; mitochondria were also classified for loss of internal structure. (pqac-00000003, pqac-00000014, pqac-00000015) | OPA1 collaborates with **MICOS/MIC60** to control crista junction width, stability, and lumen shape; different L/S balances produce distinct crista architectures. (pqac-00000008, pqac-00000020) | Supports annotation to mitochondrial crista morphogenesis and junction maintenance. | (pqac-00000015, pqac-00000008, pqac-00000020) |
| Morpholino knockdown evidence | Translation-blocking and splice-blocking morpholinos reduced Opa1 protein strongly at 24-72 hpf. The 100/85/80 kDa isoforms fell to **<10% of control at 24 hpf**; the 78 kDa doublet fell to ~**50%**, then became **~4-fold more intense at 48 hpf**. (pqac-00000012) | Prior mammalian work predicts that partial loss of OPA1 reduces fusion and perturbs cristae/bioenergetics. (pqac-00000001, pqac-00000005) | Confirms zebrafish Opa1 is dosage-sensitive and exhibits isoform-selective regulation in early development. | (pqac-00000012, pqac-00000001) |
| CRISPR crispant / knockout evidence | CRISPR targeting exons 8-9 produced a ~**932 bp deletion**; **90.3%** of F0 animals carried the deletion band. Stable opa1-/- larvae were developmentally viable early but **did not survive past ~60 dpf / were absent by 2 months**. (pqac-00000014, pqac-00000015, pqac-00000019) | Vertebrate Opa1 knockout is generally severe/lethal, consistent with essential developmental roles. (pqac-00000009) | Important for annotation confidence because genetic KO/crispant results converge with older morpholino data. | (pqac-00000014, pqac-00000015, pqac-00000019, pqac-00000009) |
| Developmental phenotypes | Morphants showed **small eyes**, **small pectoral fins**, enlarged hindbrain ventricle, impaired circulation, **unlooped hearts**, pericardial edema, reduced heart rate, larger yolk, reduced startle/locomotion, and death before **7 dpf**. (pqac-00000012, pqac-00000013, pqac-00000016) | Cross-species OPA1 loss disrupts development through mitochondrial fusion/cristae failure and downstream energetic stress. (pqac-00000001, pqac-00000009) | Early pleiotropy likely reflects high developmental energy demand rather than unrelated non-mitochondrial function. | (pqac-00000012, pqac-00000016, pqac-00000009) |
| Visual / retinal phenotypes | CRISPR opa1 larvae had **marked visual impairment** with preserved gross locomotion; retinal lamination and RGC numbers were grossly normal early, but mitoEGFP signal in RGCs was significantly reduced, indicating mitochondrial dysfunction precedes neurodegeneration. (pqac-00000003, pqac-00000015, pqac-00000019) | Human OPA1 mutations cause autosomal optic atrophy, with retinal ganglion cells especially vulnerable. (pqac-00000009, pqac-00000001) | Zebrafish data support a neuron/axon-centric annotation relevant to optic neuropathy biology. | (pqac-00000003, pqac-00000015, pqac-00000019, pqac-00000009) |
| Quantitative visual-function data | In CRISPR crispants, OKR saccades were significantly reduced: **33.29%** decrease at **0.02 cpd**, **64.43%** decrease at **0.2 cpd**, and **37.28%** reduction in contrast sensitivity with **20%** black-white contrast. VMR locomotor activity was not significantly altered. (pqac-00000019) | These functional readouts align with OPA1-linked optic neuropathy phenotypes seen across model systems and patients. (pqac-00000009) | Strongest zebrafish quantitative evidence that Opa1 loss preferentially impairs visual system function. | (pqac-00000019, pqac-00000009) |
| Bioenergetics / respiration | In morphants, **total basal respiration decreased significantly**; **proton leak** and **maximal uncoupled OCR** were not different, while **RCR increased significantly at 24 and 72 hpf (p<0.03)**. In CRISPR larvae, **maximal respiration decreased**, while **basal respiration** and **ATP production** were not significantly altered; **non-mitochondrial respiration** and **proton leak** increased. (pqac-00000013, pqac-00000015) | OPA1 supports respiratory supercomplex stability, complex V organization, and mitochondrial energetic plasticity. (pqac-00000003, pqac-00000004) | Suggests Opa1 is especially important for **respiratory reserve / stress response**, not only basal ATP output. | (pqac-00000013, pqac-00000015, pqac-00000003, pqac-00000004) |
| Gene-expression / compensatory response | Morphants transiently upregulated **pgc1a** at 24 and 48 hpf and increased **peo1** at 48 hpf; **mfn1, mfn2, and opa1** transcripts were upregulated at 48 hpf, while **drp1** was unchanged and mtDNA copy number/integrity was unchanged. (pqac-00000013) | Cross-species studies link OPA1 loss to mtDNA maintenance and mitochondrial stress responses. (pqac-00000001) | Indicates compensatory mitochondrial biogenesis/fusion signaling in response to impaired Opa1 function. | (pqac-00000013, pqac-00000001) |
| Neuronal axon mitochondrial pathology | In zebrafish optic nerve/RGC axons, Opa1 loss caused **mitochondrial fragmentation** and **disordered cristae**; EM quantified longest axis, area, circularity, and cristae area, with analyses on **n = 226-345 mitochondria** depending on metric. (pqac-00000015) | In situ cryo-ET and structural studies show OPA1 state dictates crista stacking, junction width, and mitochondrial shape. (pqac-00000020, pqac-00000005) | Provides direct subcellular evidence tying zebrafish visual dysfunction to axonal mitochondrial ultrastructure. | (pqac-00000015, pqac-00000020, pqac-00000005) |
| Functional annotation summary | Danio rerio **opa1 / Q5U3A7** encodes a **mitochondrial inner-membrane dynamin-like GTPase** required for **GTP-dependent IMM fusion**, **cristae junction/ultrastructure maintenance**, and **mitochondrial respiratory resilience**; regulation likely depends on conserved **L-Opa1/S-Opa1** processing by **OMA1/YME1L**. Zebrafish loss-of-function causes early developmental, cardiac, visual, ultrastructural, and bioenergetic phenotypes. (pqac-00000012, pqac-00000013, pqac-00000015, pqac-00000019) | Mechanistic consensus across structural, cell, and animal studies strongly supports this annotation. (pqac-00000000, pqac-00000001, pqac-00000005, pqac-00000020) | Best-supported primary role is mitochondrial membrane remodeling, not generalized signaling; pathology arises from downstream energetic and crista defects. | (pqac-00000012, pqac-00000013, pqac-00000015, pqac-00000019, pqac-00000000, pqac-00000020) |


*Table: This table summarizes the functional annotation of Danio rerio opa1 (UniProt Q5U3A7), integrating zebrafish-specific morpholino and CRISPR evidence with conserved OPA1 mechanism from cross-species studies. It highlights localization, molecular function, isoform processing, phenotypes, and key quantitative data relevant for gene annotation.*