Tpp1 is the zebrafish orthologue of tripeptidyl-peptidase 1 (CLN2), a lysosomal sedolisin-family (MEROPS S53) serine-carboxyl peptidase that is synthesized as a zymogen with a signal peptide and a long propeptide and is activated by autocatalytic processing at acidic pH. The mature enzyme is an acid-active exopeptidase that releases N-terminal tripeptides from peptides with a free N-terminus, including the breakdown products generated by lysosomal endopeptidases, and it has weaker endopeptidase activity; it therefore contributes to bulk protein turnover inside the lysosome. In zebrafish the protein is expressed in the developing retina and brain. Loss of tpp1 removes tripeptidyl-peptidase activity from embryo extracts and produces hypertrophic lysosomes, storage of subunit c of mitochondrial ATP synthase, apoptosis and impaired secondary neurogenesis in the retina, optic tectum and cerebellum, disorganized axon tracts, seizure-like hyperactivity and motor decline, modelling human CLN2 (late-infantile neuronal ceroid lipofuscinosis).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0006508 proteolysis | IBA GO_REF:0000033 | ACCEPT | Summary: Proteolysis is the general process carried out by a peptidase. Zebrafish Tpp1 is a lysosomal serine-carboxyl peptidase; the CLN2 subfamily is highly conserved across vertebrates and tpp1(sa0011) mutant extracts lack tripeptidyl-peptidase activity, so the enzyme itself does the peptide-bond hydrolysis this term names. Reason: The PAINT node PTN000368455 spans the sedolisin/CLN2 family (human, rat, Dictyostelium donors), all of which are peptidases; the zebrafish gene has direct evidence of peptidase activity from the CLN2 mutant assay [PMID:23587805] and UniProt records EC 3.4.14.9 for this entry. The term is general but not wrong; the lysosomal context is captured by the GO:1905146 IBA row. Supporting Evidence: file:DANRE/tpp1/tpp1-uniprot.txt Lysosomal serine protease with tripeptidyl-peptidase I PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidyl peptidase 1 and PMID:14609438 The discovery of highly conserved CLN2-like enzymes not only in mammals but also in two fish species and one of frogs may indicate that these peptidases are universally present in the vertebrates |
| GO:0008240 tripeptidyl-peptidase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Tripeptidyl-peptidase activity is the release of an N-terminal tripeptide from a polypeptide (GO:0008240). This is the defining activity of the CLN2/TPP1 subfamily; UniProt records EC 3.4.14.9 for zebrafish Tpp1 on the basis of the CLN2 mutant paper, whose fluorogenic Arg-Ala-Phe-ACC assay at pH 4 shows that tpp1(sa0011) embryos have lost this activity. Reason: Core molecular function. The IBA is placed at PTN000368455 with human, mouse, rat and Dictyostelium experimental donors, and the zebrafish gene has its own experimental support: the mutant is described as deficient in tripeptidyl peptidase 1 [PMID:23587805], and the catalytic triad Ser/Glu/Asp of sedolisins is conserved in the zebrafish sequence [PMID:14609438]. Supporting Evidence: file:DANRE/tpp1/tpp1-uniprot.txt Lysosomal serine protease with tripeptidyl-peptidase I file:DANRE/tpp1/tpp1-uniprot.txt Release of an N-terminal tripeptide from a polypeptide, but PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidyl peptidase 1 and file:DANRE/tpp1/tpp1-deep-research-falcon.md **Tpp1 enzymatic activity is significantly reduced** in embryo extracts using the Arg-Ala-Phe-ACC assay PMID:14609438 characterized by the utilization of a fully conserved catalytic triad (Ser, Glu, Asp) and by the presence of an Asp in the oxyanion hole |
| GO:0004175 endopeptidase activity | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Endopeptidase activity (hydrolysis of internal peptide bonds) is a secondary activity of TPP1: the EC 3.4.14.9 reaction recorded for zebrafish Tpp1 states that the enzyme releases N-terminal tripeptides but also has endopeptidase activity. The physiologically dominant activity is the exopeptidase one. Reason: The activity is real for the family (the UniProt catalytic-activity line explicitly includes it) and the PAINT node PTN000368455 carries human and rat donors with experimental endopeptidase data, so the transfer is sound. It is not the core activity: the CLN2 disease phenotype and the zebrafish mutant assay both track loss of tripeptidyl exopeptidase cleavage, so this term is retained as non-core rather than as a defining function. Supporting Evidence: file:DANRE/tpp1/tpp1-uniprot.txt Release of an N-terminal tripeptide from a polypeptide, but file:DANRE/tpp1/tpp1-uniprot.txt also has endopeptidase activity file:DANRE/tpp1/tpp1-deep-research-falcon.md removing **tripeptides** from the N-termini of polypeptide substrates, with some **limited endopeptidase activity** |
| GO:0007417 central nervous system development | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: This IBA at PTN002681568 propagates the zebrafish IMP annotation (ZFIN:ZDB-GENE-030131-6654 is the only listed donor) to the vertebrate TPP1 clade. It asserts that TPP1 orthologues are involved in CNS development because their loss causes neurodegeneration (CLN2 disease in humans, the sa0011 phenotype in zebrafish). Reason: The node placement is defensible: TPP1 deficiency causes CNS pathology in human, mouse and zebrafish, so the phenotype is a clade-wide property rather than a zebrafish idiosyncrasy. However the underlying claim is the same downstream-phenotype claim as the IMP rows (Tpp1 does not perform a step of CNS development; neurons degenerate when lysosomal proteolysis fails), so the same non-core status applies. No propagation failure is asserted. Supporting Evidence: PMID:23587805 apoptotic cell death in the retina, optic tectum and cerebellum PMID:23587805 Tripeptidyl peptidase 1 (TPP1) deficiency causes CLN2 disease, late infantile PMID:14609438 expression of this enzyme lead to a fatal neurodegenerative disease |
| GO:0004252 serine-type endopeptidase activity | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Serine-type endopeptidase activity is mapped from the Peptidase S8/S53 superfamily fold (IPR036852). Tpp1 is a serine-carboxyl (sedolisin) peptidase with a Ser/Glu/Asp triad rather than the classical Ser/His/Asp triad, and its endopeptidase activity is a minor activity alongside its main tripeptidyl exopeptidase activity. Reason: Not wrong: TPP1 does hydrolyse internal peptide bonds (UniProt catalytic activity line) and the nucleophile is a serine, so the term applies. But the IPR036852 fold mapping cannot distinguish the endopeptidase subtilisins from the exopeptidase-dominant CLN2 subfamily, and the informative activity is GO:0008240. Kept as non-core, consistent with the GO:0004175 IBA row. Supporting Evidence: file:DANRE/tpp1/tpp1-uniprot.txt also has endopeptidase activity PMID:14609438 characterized by the utilization of a fully conserved catalytic triad (Ser, Glu, Asp) and by the presence of an Asp in the oxyanion hole |
| GO:0005764 lysosome | IEA GO_REF:0000044 | ACCEPT | Summary: Lysosome localization, mapped from the UniProt subcellular-location keyword (SL-0158). Zebrafish Tpp1 is annotated by UniProt as lysosomal by similarity to human TPP1, and tpp1 mutants show hypertrophic lysosomes with storage material, the hallmark of a missing lysosomal hydrolase. Reason: The localization is the defining context of this enzyme: it has a signal peptide, a propeptide removed autocatalytically at acidic pH, and an acid pH optimum; the CLN2 mutant phenotype (hypertrophic lysosomes, subunit c storage) is a lysosomal storage phenotype [PMID:23587805]. Supporting Evidence: file:DANRE/tpp1/tpp1-uniprot.txt SUBCELLULAR LOCATION: Lysosome file:DANRE/tpp1/tpp1-uniprot.txt Lysosomal serine protease with tripeptidyl-peptidase I PMID:23587805 of mitochondrial ATP-synthase, hypertrophic lysosomes as well as localized |
| GO:0006508 proteolysis | IEA GO_REF:0000002 | ACCEPT | Summary: Proteolysis mapped from the sedolisin/peptidase S53 InterPro entries (IPR000209, IPR030400, IPR036852). Tpp1 is an active peptidase in zebrafish (tripeptidyl-peptidase activity is lost in the sa0011 mutant). Reason: Correct and consistent with the IBA row for the same term; the InterPro entries identify the catalytic domain that performs the hydrolysis. The more specific lysosomal context is carried by the GO:1905146 IBA row. Supporting Evidence: file:DANRE/tpp1/tpp1-uniprot.txt Lysosomal serine protease with tripeptidyl-peptidase I PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidyl peptidase 1 and |
| GO:0008236 serine-type peptidase activity | IEA GO_REF:0000002 | MODIFY | Summary: Serine-type peptidase activity from the S53 family InterPro entries (IPR000209, IPR015366). True (the sedolisin nucleophile is a serine) but it is the parent of the informative term, tripeptidyl-peptidase activity, which is supported by the mutant enzyme assay. Reason: The InterPro mapping stops at the mechanism class; the specific activity of this protein, release of N-terminal tripeptides (EC 3.4.14.9), is documented for zebrafish Tpp1 [PMID:23587805] and is already the IBA/ISS term. Replace with GO:0008240. Proposed replacements: tripeptidyl-peptidase activity Supporting Evidence: file:DANRE/tpp1/tpp1-uniprot.txt Lysosomal serine protease with tripeptidyl-peptidase I file:DANRE/tpp1/tpp1-uniprot.txt Release of an N-terminal tripeptide from a polypeptide, but PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidyl peptidase 1 and file:DANRE/tpp1/tpp1-deep-research-falcon.md **Tpp1 enzymatic activity is significantly reduced** in embryo extracts using the Arg-Ala-Phe-ACC assay |
| GO:0005764 lysosome | ISS GO_REF:0000024 | ACCEPT | Summary: Lysosome localization transferred by UniProt from human TPP1 (O14773). The zebrafish protein has the same domain architecture (signal peptide, propeptide, S53 catalytic domain) and the mutant shows a lysosomal storage phenotype. Reason: The transfer from human TPP1 is appropriate: the CLN2 subfamily is highly conserved from fish to mammals [PMID:14609438], and the hypertrophic lysosomes and subunit c storage in tpp1 mutants [PMID:23587805] are the expected consequence of losing a lysosomal hydrolase. Supporting Evidence: file:DANRE/tpp1/tpp1-uniprot.txt SUBCELLULAR LOCATION: Lysosome file:DANRE/tpp1/tpp1-uniprot.txt Lysosomal serine protease with tripeptidyl-peptidase I PMID:23587805 of mitochondrial ATP-synthase, hypertrophic lysosomes as well as localized PMID:14609438 Complete sequences are shown for CLN2 from human, fugu, and zebrafish |
| GO:0007417 central nervous system development | IMP PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidy... | KEEP AS NON CORE | Summary: Central nervous system development is annotated from the tpp1(sa0011) homozygous mutant [PMID:23587805]: loss of Tpp1 gives a small retina and head, localized apoptosis in retina, optic tectum and cerebellum and disorganized optic nerve and spinal-cord axon tracts. The cached record is abstract-only. Reason: Participation test: Tpp1 is a lysosomal housekeeping peptidase; it does not itself perform any step of nervous-system morphogenesis. The CNS defects in tpp1 mutants and morphants (small retina and head, apoptosis in retina, optic tectum and cerebellum, disorganized axon tracts) follow from lysosomal storage and cell death, i.e. they are downstream consequences of lost lysosomal proteolysis. The acts_upstream_of_or_within qualifier used by ZFIN already encodes this indirectness, and the evidence is experimental and cannot be checked beyond the abstract, so the row is kept as a non-core phenotype annotation rather than removed. Supporting Evidence: PMID:23587805 early onset neurodegenerative phenotype, characterized by a significantly small PMID:23587805 apoptotic cell death in the retina, optic tectum and cerebellum PMID:23587805 spinal cord, optic nerve and the posterior commissure are disorganized, with the file:DANRE/tpp1/tpp1-uniprot.txt Morpholino knockdown of the protein in embryos file:DANRE/tpp1/tpp1-uniprot.txt including reduced eye and head size, a curved body, small jaw |
| GO:0007626 locomotory behavior | IMP PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidy... | MARK AS OVER ANNOTATED | Summary: Locomotory behavior is annotated from the tpp1(sa0011) mutant, which shows a phase of hyperactivity consistent with seizures followed by functional motor impairment. These are behavioural read-outs of progressive neurodegeneration. Reason: The experimental observation is not disputed and the row is not removed, but a lysosomal peptidase does not participate in locomotory behavior; the altered swimming of tpp1 larvae is a consequence of neuronal loss and seizure activity that follows lysosomal storage. Annotating the behaviour to the enzyme over-extends a disease-model phenotype into a gene function; the acts_upstream_of_or_within qualifier is the only thing keeping the claim accurate. Supporting Evidence: PMID:23587805 eventually results in functional motor impairment, but this is preceded by a PMID:23587805 phase of hyperactivity that is consistent with seizures |
| GO:0022008 neurogenesis | IMP PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidy... | KEEP AS NON CORE | Summary: Neurogenesis is annotated from the tpp1(sa0011) homozygous mutant [PMID:23587805]: secondary neurogenesis in the retina, optic tectum and cerebellum is impaired and proliferation is reduced when Tpp1 is lost. Reason: Participation test: the reduced proliferation and impaired secondary neurogenesis in tpp1 mutants and morphants are consequences of lysosomal dysfunction and apoptosis in the retina, optic tectum and cerebellum, not of Tpp1 acting in a neurogenic programme. The qualifier acts_upstream_of_or_within correctly records the indirect relationship. Experimental evidence from a paper cached only as abstract cannot be overruled, so the annotation is kept as a non-core phenotype. Supporting Evidence: PMID:23587805 Secondary neurogenesis in the PMID:23587805 retina, optic tectum and cerebellum is impaired and axon tracts within the PMID:23587805 displays progressive neurodegeneration accompanied by a reduction in PMID:23587805 apoptotic cell death in the retina, optic tectum and cerebellum |
| GO:0008240 tripeptidyl-peptidase activity | ISS PMID:14609438 A model of tripeptidyl-peptidase I (CLN2), a ubiquitous and ... | ACCEPT | Summary: Tripeptidyl-peptidase activity by sequence similarity to human TPP1, citing the sedolisin-family modelling paper that first identified and corrected the zebrafish CLN2 sequence and showed the catalytic residues are conserved. Reason: Core function. The ISS is now backed by direct zebrafish evidence: tpp1(sa0011) embryo extracts are deficient in tripeptidyl-peptidase activity [PMID:23587805], and UniProt assigns EC 3.4.14.9 to this entry on that basis. PMID:14609438 shows the zebrafish enzyme aligns with human CLN2 over the catalytic domain with the Ser/Glu/Asp triad conserved. Supporting Evidence: PMID:14609438 Complete sequences are shown for CLN2 from human, fugu, and zebrafish PMID:14609438 characterized by the utilization of a fully conserved catalytic triad (Ser, Glu, Asp) and by the presence of an Asp in the oxyanion hole file:DANRE/tpp1/tpp1-uniprot.txt Lysosomal serine protease with tripeptidyl-peptidase I file:DANRE/tpp1/tpp1-uniprot.txt Release of an N-terminal tripeptide from a polypeptide, but PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidyl peptidase 1 and |
| GO:0005764 lysosome | IBA GO_REF:0000033 | ACCEPT | Summary: Lysosome as the compartment where Tpp1 is active, from PAINT node PTN001022357 (human and mouse donors). Tpp1 is an acid-active enzyme with a signal peptide and an autocatalytically removed propeptide; zebrafish mutants show hypertrophic lysosomes. Reason: Node placement at the vertebrate TPP1 clade is correct: human and mouse TPP1 are lysosomal, the zebrafish protein retains the precursor architecture, UniProt annotates it lysosomal, and the sa0011 mutant develops a lysosomal storage phenotype [PMID:23587805]. Consistent with the IEA and ISS rows for the same term. Supporting Evidence: file:DANRE/tpp1/tpp1-uniprot.txt SUBCELLULAR LOCATION: Lysosome file:DANRE/tpp1/tpp1-uniprot.txt Lysosomal serine protease with tripeptidyl-peptidase I PMID:23587805 of mitochondrial ATP-synthase, hypertrophic lysosomes as well as localized file:DANRE/tpp1/tpp1-uniprot.txt Activated by autocatalytic proteolytical processing |
| GO:0007417 central nervous system development | IMP PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidy... | KEEP AS NON CORE | Summary: Central nervous system development is annotated from a tpp1 morpholino (ZDB-MRPHLNO-130718-1) [PMID:23587805]: loss of Tpp1 gives a small retina and head, localized apoptosis in retina, optic tectum and cerebellum and disorganized optic nerve and spinal-cord axon tracts. The cached record is abstract-only. Reason: Participation test: Tpp1 is a lysosomal housekeeping peptidase; it does not itself perform any step of nervous-system morphogenesis. The CNS defects in tpp1 mutants and morphants (small retina and head, apoptosis in retina, optic tectum and cerebellum, disorganized axon tracts) follow from lysosomal storage and cell death, i.e. they are downstream consequences of lost lysosomal proteolysis. The acts_upstream_of_or_within qualifier used by ZFIN already encodes this indirectness, and the evidence is experimental and cannot be checked beyond the abstract, so the row is kept as a non-core phenotype annotation rather than removed. Supporting Evidence: PMID:23587805 early onset neurodegenerative phenotype, characterized by a significantly small PMID:23587805 apoptotic cell death in the retina, optic tectum and cerebellum PMID:23587805 spinal cord, optic nerve and the posterior commissure are disorganized, with the file:DANRE/tpp1/tpp1-uniprot.txt Morpholino knockdown of the protein in embryos file:DANRE/tpp1/tpp1-uniprot.txt including reduced eye and head size, a curved body, small jaw |
| GO:0007417 central nervous system development | IMP PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidy... | KEEP AS NON CORE | Summary: Central nervous system development is annotated from a tpp1 morpholino (ZDB-MRPHLNO-130718-2) [PMID:23587805]: loss of Tpp1 gives a small retina and head, localized apoptosis in retina, optic tectum and cerebellum and disorganized optic nerve and spinal-cord axon tracts. The cached record is abstract-only. Reason: Participation test: Tpp1 is a lysosomal housekeeping peptidase; it does not itself perform any step of nervous-system morphogenesis. The CNS defects in tpp1 mutants and morphants (small retina and head, apoptosis in retina, optic tectum and cerebellum, disorganized axon tracts) follow from lysosomal storage and cell death, i.e. they are downstream consequences of lost lysosomal proteolysis. The acts_upstream_of_or_within qualifier used by ZFIN already encodes this indirectness, and the evidence is experimental and cannot be checked beyond the abstract, so the row is kept as a non-core phenotype annotation rather than removed. Supporting Evidence: PMID:23587805 early onset neurodegenerative phenotype, characterized by a significantly small PMID:23587805 apoptotic cell death in the retina, optic tectum and cerebellum PMID:23587805 spinal cord, optic nerve and the posterior commissure are disorganized, with the file:DANRE/tpp1/tpp1-uniprot.txt Morpholino knockdown of the protein in embryos file:DANRE/tpp1/tpp1-uniprot.txt including reduced eye and head size, a curved body, small jaw |
| GO:0022008 neurogenesis | IMP PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidy... | KEEP AS NON CORE | Summary: Neurogenesis is annotated from a tpp1 morpholino (ZDB-MRPHLNO-130718-1) [PMID:23587805]: secondary neurogenesis in the retina, optic tectum and cerebellum is impaired and proliferation is reduced when Tpp1 is lost. Reason: Participation test: the reduced proliferation and impaired secondary neurogenesis in tpp1 mutants and morphants are consequences of lysosomal dysfunction and apoptosis in the retina, optic tectum and cerebellum, not of Tpp1 acting in a neurogenic programme. The qualifier acts_upstream_of_or_within correctly records the indirect relationship. Experimental evidence from a paper cached only as abstract cannot be overruled, so the annotation is kept as a non-core phenotype. Supporting Evidence: PMID:23587805 Secondary neurogenesis in the PMID:23587805 retina, optic tectum and cerebellum is impaired and axon tracts within the PMID:23587805 displays progressive neurodegeneration accompanied by a reduction in PMID:23587805 apoptotic cell death in the retina, optic tectum and cerebellum |
| GO:0022008 neurogenesis | IMP PMID:23587805 A zebrafish model of CLN2 disease is deficient in tripeptidy... | KEEP AS NON CORE | Summary: Neurogenesis is annotated from a tpp1 morpholino (ZDB-MRPHLNO-130718-2) [PMID:23587805]: secondary neurogenesis in the retina, optic tectum and cerebellum is impaired and proliferation is reduced when Tpp1 is lost. Reason: Participation test: the reduced proliferation and impaired secondary neurogenesis in tpp1 mutants and morphants are consequences of lysosomal dysfunction and apoptosis in the retina, optic tectum and cerebellum, not of Tpp1 acting in a neurogenic programme. The qualifier acts_upstream_of_or_within correctly records the indirect relationship. Experimental evidence from a paper cached only as abstract cannot be overruled, so the annotation is kept as a non-core phenotype. Supporting Evidence: PMID:23587805 Secondary neurogenesis in the PMID:23587805 retina, optic tectum and cerebellum is impaired and axon tracts within the PMID:23587805 displays progressive neurodegeneration accompanied by a reduction in PMID:23587805 apoptotic cell death in the retina, optic tectum and cerebellum |
| GO:1905146 lysosomal protein catabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: Lysosomal protein catabolic process (any cellular protein catabolic process taking place in a lysosome) from PAINT node PTN001022357 with mouse TPP1 as donor. Tpp1 generates tripeptides from the breakdown products of lysosomal proteinases inside the lysosome; its loss causes storage of undegraded material (subunit c of ATP synthase) and hypertrophic lysosomes. Reason: This is the most specific and most accurate process term for the gene: the enzyme itself performs a step of lysosomal protein breakdown (tripeptide release), so the participation test is passed, and the zebrafish mutant shows the storage phenotype expected when that step fails [PMID:23587805]. Preferred over the general proteolysis rows for core_functions. Supporting Evidence: file:DANRE/tpp1/tpp1-uniprot.txt May act as a non-specific lysosomal file:DANRE/tpp1/tpp1-uniprot.txt peptidase which generates tripeptides from the breakdown products PMID:23587805 of mitochondrial ATP-synthase, hypertrophic lysosomes as well as localized file:DANRE/tpp1/tpp1-deep-research-falcon.md Loss of Tpp1 produces classic lysosomal storage phenotypes including **enlarged/hypertrophic lysosomes** |
Loading supporting content…
Download this section (compressed HTML)Q: Which endogenous lysosomal substrates require zebrafish Tpp1-mediated removal of N-terminal tripeptides, and which accumulate as storage material when the enzyme is absent?
Q: Does zebrafish Tpp1 require autocatalytic activation of its zymogen at acidic lysosomal pH, mirroring the proenzyme maturation described for mammalian TPP-I/CLN2?
Q: To what extent do the neurodegenerative and locomotor phenotypes of Tpp1-deficient zebrafish stem from impaired lysosomal proteolysis versus secondary consequences of ceroid-lipofuscin storage?
Experiment: Generate a tpp1 null line by CRISPR/Cas9, then assay lysosomal tripeptidyl-peptidase activity in larval/adult brain lysates against a fluorogenic Ala-Ala-Phe substrate and quantify ceroid-lipofuscin storage histologically.
Hypothesis: Loss of zebrafish tpp1 abolishes lysosomal tripeptidyl-peptidase activity and leads to accumulation of autofluorescent storage material in neurons.
Type: CRISPR knockout
Experiment: Express and purify the Tpp1 proenzyme, incubate across a range of pH values (acidic lysosomal versus neutral), and monitor proteolytic processing and gain of exopeptidase activity over time by SDS-PAGE and activity assays.
Hypothesis: Recombinant zebrafish Tpp1 is produced as an inactive zymogen that undergoes autocatalytic activation upon exposure to acidic pH.
Type: tripeptidyl-peptidase activity assay
Experiment: Reintroduce wild-type or catalytically dead tpp1 mRNA/transgene into tpp1 mutants and assess rescue of progressive neurodegeneration, neuronal proliferation, and swimming behavior alongside lipofuscin storage load.
Hypothesis: Restoring Tpp1 enzymatic activity in tpp1-deficient zebrafish rescues neurodegeneration and locomotor defects.
Type: lipofuscin/storage-material histology
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)