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Structural and Genetic Studies Demonstrate Neurologic Dysfunction in Triosephosphate Isomerase Deficiency Is Associated with Impaired Synaptic Vesicle Dynamics.

Roland BP, Zeccola AM, Larsen SB, Amrich CG, Talsma AD, Stuchul KA, Heroux A, Levitan ES, VanDemark AP, Palladino MJ - PLoS Genet. (2016)

Bottom Line: This study combines structural, biochemical, and genetic approaches to demonstrate that perturbations of the TPI dimer interface are sufficient to elicit TPI deficiency neuropathogenesis.The present study demonstrates that neurologic dysfunction resulting from TPI deficiency is characterized by synaptic vesicle dysfunction, and can be attenuated with catalytically inactive TPI.Collectively, our findings are the first to identify, to our knowledge, a functional synaptic defect in TPI deficiency derived from molecular changes in the TPI dimer interface.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.

ABSTRACT
Triosephosphate isomerase (TPI) deficiency is a poorly understood disease characterized by hemolytic anemia, cardiomyopathy, neurologic dysfunction, and early death. TPI deficiency is one of a group of diseases known as glycolytic enzymopathies, but is unique for its severe patient neuropathology and early mortality. The disease is caused by missense mutations and dysfunction in the glycolytic enzyme, TPI. Previous studies have detailed structural and catalytic changes elicited by disease-associated TPI substitutions, and samples of patient erythrocytes have yielded insight into patient hemolytic anemia; however, the neuropathophysiology of this disease remains a mystery. This study combines structural, biochemical, and genetic approaches to demonstrate that perturbations of the TPI dimer interface are sufficient to elicit TPI deficiency neuropathogenesis. The present study demonstrates that neurologic dysfunction resulting from TPI deficiency is characterized by synaptic vesicle dysfunction, and can be attenuated with catalytically inactive TPI. Collectively, our findings are the first to identify, to our knowledge, a functional synaptic defect in TPI deficiency derived from molecular changes in the TPI dimer interface.

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TPI dimer interface substitutions do not alter NMJ development and morphology.(A) NMJ morphology of segment A2 muscle 6/7 was characterized for (B) bouton number and (C) branching. Boutons were defined as varicosities greater than 2 μm in diameter. Neither parameter showed significant differences elicited by the mutations, relative to either dTPIWT or dTPIWT-CFP/TPIWT. CFP tags did not alter the behavioral deficits of the animals (S6 Fig). n = 10. Comparisons were made with a One-way ANOVA using Tukey’s post hoc test, ns indicated no significance. Scale bar = 10 μm.
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pgen.1005941.g008: TPI dimer interface substitutions do not alter NMJ development and morphology.(A) NMJ morphology of segment A2 muscle 6/7 was characterized for (B) bouton number and (C) branching. Boutons were defined as varicosities greater than 2 μm in diameter. Neither parameter showed significant differences elicited by the mutations, relative to either dTPIWT or dTPIWT-CFP/TPIWT. CFP tags did not alter the behavioral deficits of the animals (S6 Fig). n = 10. Comparisons were made with a One-way ANOVA using Tukey’s post hoc test, ns indicated no significance. Scale bar = 10 μm.

Mentions: Finally, functional changes at the synapse can be the result of acute impairments in recycling machinery or more chronic developmental defects. Mutations in the E3- ubiquitin ligase Highwire or alterations in the trans-synaptic signaling proteins wingless and Glass-bottom boat have been shown to alter synaptic function through primary changes in development [49–51]. These changes in synaptic physiology are accompanied by dramatic alterations in synaptic morphology, a hallmark of neurodevelopmental defects. To examine whether aberrant neurodevelopment may contribute to this recycling deficit, we morphologically characterized the Drosophila NMJ from segment A2, muscle 6/7; this particular NMJ is highly elaborate and therefore sensitive to developmental perturbations. The dTPIM80T, dTPIT73R, and dTPIG74E alleles all exhibited early lethality if maintained at 25°C, therefore development was scored at RT. Third instar larva were dissected, and an assessment of bouton number and branches revealed no significant developmental differences in the thermal-stress sensitive mutants relative to dTPIWT (Fig 8). These results suggest that the synaptic defect is an acute disruption of function, and not likely a secondary defect caused by altered development. Collectively, these data demonstrate that TPI deficiency thermal-stress sensitivity is characterized by acute perturbation of synaptic vesicle dynamics.


Structural and Genetic Studies Demonstrate Neurologic Dysfunction in Triosephosphate Isomerase Deficiency Is Associated with Impaired Synaptic Vesicle Dynamics.

Roland BP, Zeccola AM, Larsen SB, Amrich CG, Talsma AD, Stuchul KA, Heroux A, Levitan ES, VanDemark AP, Palladino MJ - PLoS Genet. (2016)

TPI dimer interface substitutions do not alter NMJ development and morphology.(A) NMJ morphology of segment A2 muscle 6/7 was characterized for (B) bouton number and (C) branching. Boutons were defined as varicosities greater than 2 μm in diameter. Neither parameter showed significant differences elicited by the mutations, relative to either dTPIWT or dTPIWT-CFP/TPIWT. CFP tags did not alter the behavioral deficits of the animals (S6 Fig). n = 10. Comparisons were made with a One-way ANOVA using Tukey’s post hoc test, ns indicated no significance. Scale bar = 10 μm.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4816394&req=5

pgen.1005941.g008: TPI dimer interface substitutions do not alter NMJ development and morphology.(A) NMJ morphology of segment A2 muscle 6/7 was characterized for (B) bouton number and (C) branching. Boutons were defined as varicosities greater than 2 μm in diameter. Neither parameter showed significant differences elicited by the mutations, relative to either dTPIWT or dTPIWT-CFP/TPIWT. CFP tags did not alter the behavioral deficits of the animals (S6 Fig). n = 10. Comparisons were made with a One-way ANOVA using Tukey’s post hoc test, ns indicated no significance. Scale bar = 10 μm.
Mentions: Finally, functional changes at the synapse can be the result of acute impairments in recycling machinery or more chronic developmental defects. Mutations in the E3- ubiquitin ligase Highwire or alterations in the trans-synaptic signaling proteins wingless and Glass-bottom boat have been shown to alter synaptic function through primary changes in development [49–51]. These changes in synaptic physiology are accompanied by dramatic alterations in synaptic morphology, a hallmark of neurodevelopmental defects. To examine whether aberrant neurodevelopment may contribute to this recycling deficit, we morphologically characterized the Drosophila NMJ from segment A2, muscle 6/7; this particular NMJ is highly elaborate and therefore sensitive to developmental perturbations. The dTPIM80T, dTPIT73R, and dTPIG74E alleles all exhibited early lethality if maintained at 25°C, therefore development was scored at RT. Third instar larva were dissected, and an assessment of bouton number and branches revealed no significant developmental differences in the thermal-stress sensitive mutants relative to dTPIWT (Fig 8). These results suggest that the synaptic defect is an acute disruption of function, and not likely a secondary defect caused by altered development. Collectively, these data demonstrate that TPI deficiency thermal-stress sensitivity is characterized by acute perturbation of synaptic vesicle dynamics.

Bottom Line: This study combines structural, biochemical, and genetic approaches to demonstrate that perturbations of the TPI dimer interface are sufficient to elicit TPI deficiency neuropathogenesis.The present study demonstrates that neurologic dysfunction resulting from TPI deficiency is characterized by synaptic vesicle dysfunction, and can be attenuated with catalytically inactive TPI.Collectively, our findings are the first to identify, to our knowledge, a functional synaptic defect in TPI deficiency derived from molecular changes in the TPI dimer interface.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.

ABSTRACT
Triosephosphate isomerase (TPI) deficiency is a poorly understood disease characterized by hemolytic anemia, cardiomyopathy, neurologic dysfunction, and early death. TPI deficiency is one of a group of diseases known as glycolytic enzymopathies, but is unique for its severe patient neuropathology and early mortality. The disease is caused by missense mutations and dysfunction in the glycolytic enzyme, TPI. Previous studies have detailed structural and catalytic changes elicited by disease-associated TPI substitutions, and samples of patient erythrocytes have yielded insight into patient hemolytic anemia; however, the neuropathophysiology of this disease remains a mystery. This study combines structural, biochemical, and genetic approaches to demonstrate that perturbations of the TPI dimer interface are sufficient to elicit TPI deficiency neuropathogenesis. The present study demonstrates that neurologic dysfunction resulting from TPI deficiency is characterized by synaptic vesicle dysfunction, and can be attenuated with catalytically inactive TPI. Collectively, our findings are the first to identify, to our knowledge, a functional synaptic defect in TPI deficiency derived from molecular changes in the TPI dimer interface.

Show MeSH
Related in: MedlinePlus