Expression of a Fragment of Ankyrin 2 Disrupts the Structure of the Axon Initial Segment and Causes Axonal Degeneration in Drosophila

Spurrier, Joshua; Shukla, Arvind Kumar; Buckley, Tyler; Smith-Trunova, Svetlana; Kuzina, Irina; Gu, Qun; Giniger, Edward

doi:10.1007/s12035-019-1477-6

Cited by 8 publications

(27 citation statements)

References 42 publications

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“…We discovered that OTUD7A is associated with synaptic, axonal, cytoskeletal, and NDD risk gene networks, which were differentially disrupted by the mutations. We confirmed the interaction of OTUD7A with the NDD risk genes Ankyrin-G (Ank3) and Ankyrin-B (Ank2), which regulate different aspects of the growth and structure of dendritic spines, axon initial segment (AIS) and axons [52][53][54][55][56][57][58]. Further analysis of Ankyrin-G revealed reduced levels in dendritic spines and the AIS in 15q13.3 microdeletion and OTUD7A L233F/L233F iNeurons, as well as reduced protein stability and elevated ubiquitination.…”

Section: Introductionsupporting

confidence: 70%

Impaired OTUD7A-dependent Ankyrin regulation mediates neuronal dysfunction in mouse and human models of the 15q13.3 microdeletion syndrome

et al. 2023

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Copy number variations (CNVs) are associated with psychiatric and neurodevelopmental disorders (NDDs), and most, including the recurrent 15q13.3 microdeletion disorder, have unknown disease mechanisms. We used a heterozygous 15q13.3 microdeletion mouse model and patient iPSC-derived neurons to reveal developmental defects in neuronal maturation and network activity. To identify the underlying molecular dysfunction, we developed a neuron-specific proximity-labeling proteomics (BioID2) pipeline, combined with patient mutations, to target the 15q13.3 CNV genetic driver OTUD7A. OTUD7A is an emerging independent NDD risk gene with no known function in the brain, but has putative deubiquitinase function. The OTUD7A protein–protein interaction network included synaptic, axonal, and cytoskeletal proteins and was enriched for ASD and epilepsy risk genes (Ank3, Ank2, SPTAN1, SPTBN1). The interactions between OTUD7A and Ankyrin-G (Ank3) and Ankyrin-B (Ank2) were disrupted by an epilepsy-associated OTUD7A L233F variant. Further investigation of Ankyrin-G in mouse and human 15q13.3 microdeletion and OTUD7AL233F/L233F models revealed protein instability, increased polyubiquitination, and decreased levels in the axon initial segment, while structured illumination microscopy identified reduced Ankyrin-G nanodomains in dendritic spines. Functional analysis of human 15q13.3 microdeletion and OTUD7AL233F/L233F models revealed shared and distinct impairments to axonal growth and intrinsic excitability. Importantly, restoring OTUD7A or Ankyrin-G expression in 15q13.3 microdeletion neurons led to a reversal of abnormalities. These data reveal a critical OTUD7A-Ankyrin pathway in neuronal development, which is impaired in the 15q13.3 microdeletion syndrome, leading to neuronal dysfunction. Furthermore, our study highlights the utility of targeting CNV genes using cell type-specific proteomics to identify shared and unexplored disease mechanisms across NDDs.

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Section: Introductionsupporting

confidence: 70%

Impaired OTUD7A-dependent Ankyrin regulation mediates neuronal dysfunction in mouse and human models of the 15q13.3 microdeletion syndrome

et al. 2023

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Section: Introductionsupporting

confidence: 62%

Impaired OTUD7A-dependent Ankyrin regulation mediates neuronal dysfunction in mouse and human models of the 15q13.3 microdeletion syndrome

Unda

Chalil

Yoon

et al. 2022

Preprint

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Copy number variations (CNV) are associated with psychiatric and neurodevelopmental disorders (NDDs), and most, including the recurrent 15q13.3 microdeletion disorder, have unknown disease mechanisms. We used a heterozygous 15q13.3 microdeletion mouse model and patient iPSC-derived neurons to reveal developmental defects in neuronal maturation and network activity. To identify the underlying molecular dysfunction, we developed a neuron-specific proximity-labeling proteomics (BioID2) pipeline, combined with patient mutations, to target the 15q13.3 CNV genetic driver OTUD7A. OTUD7A is an emerging independent NDD risk gene with no known function in the brain, but has putative deubiquitinase (DUB) function. The OTUD7A protein-protein interaction (PPI) network revealed interactions with synaptic, axonal, and cytoskeletal proteins and was enriched for known ASD and epilepsy risk genes. The interactions between OTUD7A and the NDD risk genes Ankyrin-G (Ank3) and Ankyrin-B (Ank2) were disrupted by an epilepsy-associated OTUD7A L233F variant. Further investigation of Ankyrin-G in mouse and human 15q13.3 microdeletion and OTUD7AL233F/L233F models revealed protein instability, increased polyubiquitination, and decreased levels in the axon initial segment (AIS), while structured illumination microscopy identified reduced Ankyrin-G nanodomains in dendritic spines. Functional analysis of human 15q13.3 microdeletion and OTUD7AL233F/L233F models revealed shared and distinct impairments to axonal growth and intrinsic excitability. Importantly, restoring OTUD7A or Ankyrin-G expression in 15q13.3 microdeletion neurons led to a reversal of abnormalities. These data reveal a critical OTUD7A-Ankyrin pathway in neuronal development, which is impaired in the 15q13.3 microdeletion syndrome, leading to neuronal dysfunction. Further, our study highlights the utility of targeting CNV genes using cell-type specific proteomics to identify shared and unexplored disease mechanisms across NDDs.

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“…When examining mitochondrial distribuCon between the somatodendriCc and axonal neuronal compartments of the MB, we observed a region of the proximal axon that appeared to lack mitochondrial fluorescence signal in WT flies. This region of the proximal axon seemed to overlap the area previously determined to correspond to the AIS of these neurons (Spurrier et al, 2019;Trunova et al, 2011).…”

Section: Mitochondria Are Selecmentioning

confidence: 56%

“…To determine if perturbing the AIS is sufficient to cause loss of the AIS-associated zone of mitochondrial exclusion, we examined mitochondrial distribuCon in flies that lack a funcConal AIS due to the expression of a dominant-interfering fragment of the Ank2 gene, called Ank2-L4 (Jegla et al, 2016;Pielage et al, 2008). In a previous study, expression of this dominant-negaCve variant shortened the AIS or ablated it altogether from early developmental stages (at least by the 3 rd larval instar) as assayed by several well-characterized molecular markers (Spurrier et al, 2019). We find here, however, that structural disrupCon of the AIS by expression of Ank2-L4 does not alter the paYern of mitochondrial distribuCon at the AIS by a staCsCcally significant amount in 3 rd instar larvae nor in 10 day-old adult flies (Figs.…”

Section: Structural Disrupmentioning

confidence: 99%

Changes in mitochondrial distribution occur at the axon initial segment in association with neurodegeneration inDrosophila

Wodrich,

Harris,

Giniger

2024

Preprint

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Changes in mitochondrial distribution are a feature of numerous age-related neurodegenerative diseases. In Drosophila, reducing the activity of Cdk5 causes a neurodegenerative phenotype and is known to affect several mitochondrial properties. Therefore, we investigated whether alterations of mitochondrial distribution are involved in Cdk5-associated neurodegeneration. We find that reducing Cdk5 activity does not alter the balance of mitochondrial localization to the somatodendritic vs. axonal neuronal compartments of the mushroom body, the learning and memory center of the Drosophila brain. We do, however, observe changes in mitochondrial distribution at the axon initial segment (AIS), a neuronal compartment located in the proximal axon involved in neuronal polarization and action potential initiation. Specifically, we observe that mitochondria are partially excluded from the AIS in wild-type neurons, but that this exclusion is lost upon reduction of Cdk5 activity, concomitant with the shrinkage of the AIS domain that is known to occur in this condition. This mitochondrial redistribution into the AIS is not likely due to the shortening of the AIS domain itself but rather due to altered Cdk5 activity. Furthermore, mitochondrial redistribution into the AIS is unlikely to be an early driver of neurodegeneration in the context of reduced Cdk5 activity.

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Expression of a Fragment of Ankyrin 2 Disrupts the Structure of the Axon Initial Segment and Causes Axonal Degeneration in Drosophila

Cited by 8 publications

References 42 publications

Impaired OTUD7A-dependent Ankyrin regulation mediates neuronal dysfunction in mouse and human models of the 15q13.3 microdeletion syndrome

Impaired OTUD7A-dependent Ankyrin regulation mediates neuronal dysfunction in mouse and human models of the 15q13.3 microdeletion syndrome

Impaired OTUD7A-dependent Ankyrin regulation mediates neuronal dysfunction in mouse and human models of the 15q13.3 microdeletion syndrome

Changes in mitochondrial distribution occur at the axon initial segment in association with neurodegeneration inDrosophila

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