<i>Drosophila</i> SPG12 ortholog, reticulon-like 1, governs presynaptic ER organization and Ca2+ dynamics

Pérez-Moreno, Juan José; Smith, Rebecca C.; Oliva, Megan; Gallo, Filomena; Ojha, Shainy; Müller, Karin H.; O’Kane, Cahir J.

doi:10.1083/jcb.202112101

Cited by 6 publications

(8 citation statements)

References 63 publications

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“…This decrease in Sec61β parallels findings in Drosophila mutants of Reticulon 1, another ER shaping and HSP linked gene. This study found that in addition to Sec61β, other ER membrane proteins, such as STIM and Stukorf, exhibited lower levels on ER tubules, suggesting overall changes in the levels of proteins at the ER membrane (Pérez-Moreno et al, 2023). However, unlike Atlastin mutants, Reticulon 1 mutants are not sensitized to the overexpression of luminal proteins (Pérez-Moreno et al, 2023).…”

Section: Discussionmentioning

confidence: 82%

“…This study found that in addition to Sec61β, other ER membrane proteins, such as STIM and Stukorf, exhibited lower levels on ER tubules, suggesting overall changes in the levels of proteins at the ER membrane (Pérez-Moreno et al, 2023). However, unlike Atlastin mutants, Reticulon 1 mutants are not sensitized to the overexpression of luminal proteins (Pérez-Moreno et al, 2023). This suggests that ER networks of Atlastin mutants have unique features compared to those of other ER-shaping proteins.…”

Section: Discussionmentioning

confidence: 82%

“…At presynaptic terminals of the Drosophila larval NMJ, the ER is highly sensitive to fixation (Summerville et al, 2016) which has limited imaging experiments to live samples, often acquired on upright microscopes using water dipping objectives (Chouhan et al, 2010; Oliva et al, 2020; O’Sullivan et al, 2012; Pérez-Moreno et al, 2023; Summerville et al, 2016; Yalçın et al, 2017). The axial resolution limit of typical water dipping objectives is >300 nm, which is insufficient to distinguish the densely packed ER tubules at presynaptic terminals (Espadas et al, 2019; Wu et al, 2017).…”

Section: Resultsmentioning

confidence: 99%

“…High resolution of the ER in Drosophila motor neuron cell bodies, axons, and presynaptic terminals At presynaptic terminals of the Drosophila larval NMJ, the ER is highly sensitive to fixation (Summerville et al, 2016) which has limited imaging experiments to live samples, often acquired on upright microscopes using water dipping objectives (Chouhan et al, 2010;Oliva et al, 2020;O'Sullivan et al, 2012;Pérez-Moreno et al, 2023;Summerville et al, 2016;Yalçın et al, 2017).…”

Section: Resultsmentioning

confidence: 99%

“…However, the cell biology and ultrastructure of these different elements of neuronal ER, particularly at presynaptic nerve terminals, have been under-investigated. This is because most studies of neuronal ER structure have either used conventional microscopy, which falls short of resolving individual ER tubules in small structures like synapses, or electron microscopy (EM), which is usually restricted to thin 2D sampling, is difficult to interpret in synaptic vesicle-rich presynaptic terminals, and does not allow examination of live dynamics (Chouhan et al, 2010; Oliva et al, 2020; Orso et al, 2009; Pérez-Moreno et al, 2023; Summerville et al, 2016; Yalçın et al, 2017; Zhu et al, 2022). Exploring the function of neuronal ER structure is important because mutations in ER-shaping genes cause neurodegenerative disorders such as Hereditary Spastic Paraplegia (HSP) and Charcot Marie Tooth Disease (Boutry et al, 2019; Fowler et al, 2019; Öztürk et al, 2020), implying that ER structure is uniquely essential for neuronal physiology.…”

Section: Introductionmentioning

confidence: 99%

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High-resolution imaging of presynaptic ER networks inAtlastinmutants

Quiñones-Frías,

Ocken,

Rodal

2023

Preprint

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The endoplasmic reticulum (ER) is a continuous organelle that extends to the periphery of neurons and regulates many neuronal functions including neurite outgrowth, neurotransmission, and synaptic plasticity. Mutations in proteins that control ER shape are linked to the neurodegenerative disorder Hereditary Spastic Paraplegia (HSP). However, the ultrastructure and dynamics of the neuronal ER have been under-investigated, particularly at presynaptic terminals. Here we developed new super-resolution and live imaging methods inD. melanogasterlarval motor neurons to investigate ER structure at presynaptic terminals from wild-type animals, and in null mutants of the HSP gene Atlastin. Previous studies indicated diffuse localization of an ER lumen marker atAtlastinmutant presynaptic terminals, which was attributed to ER fragmentation. By contrast, we found using an ER membrane marker that the ER inAtlastinmutants formed robust networks. Further, our high-resolution imaging results suggest that overexpression of luminal ER proteins inAtlastinmutants causes their progressive displacement to the cytosol at synapses, perhaps due to proteostatic stress and/or changes in ER membrane integrity. Remarkably, these luminal ER proteins remain correctly localized in cell bodies, axons, and other cell types such as body wall muscles, suggesting that ER tubules at synapses have unique structural and functional characteristics. This displacement phenotype has not been reported in numerous studies of Atlastin in non-neuronal cells, emphasizing the importance of conducting experiments in neurons when investigating the mechanisms leading to upper motor neuron dysfunction in HSP.

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

High-resolution imaging of presynaptic ER networks inAtlastinmutants

Quiñones-Frías,

Ocken,

Rodal

2023

Preprint

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Loss of Fic causes progressive neurodegeneration in a Drosophila model of hereditary spastic paraplegia

Lobato,

Ortiz-Vega,

Canic

et al. 2024

Biochimica et Biophysica Acta (BBA) - Molecular Basis of Diseas

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RTN2 deficiency results in an autosomal recessive distal motor neuropathy with lower limb spasticity

Maroofian,

Sarraf,

O’Brien

et al. 2024

Brain

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Heterozygous RTN2 variants have been previously identified in a limited cohort of families affected by autosomal dominant spastic paraplegia (SPG12-OMIM:604805) with a variable age of onset. Nevertheless, the definitive validity of SPG12 remains to be confidently confirmed due to scarcity of supporting evidence. In our study, we identified and validated seven novel or ultra-rare homozygous loss-of-function RTN2 variants in 14 individuals from seven consanguineous families with distal hereditary motor neuropathy (dHMN) using exome, genome and Sanger sequencing coupled with deep-phenotyping. All affected individuals (seven males and seven females, aged 9-50 years) exhibited weakness in the distal upper and lower limbs, lower limb spasticity, hyperreflexia, with an onset in the first decade of life. Nerve conduction studies revealed axonal motor neuropathy with neurogenic changes in the electromyography. Despite a slowly progressive disease course, all patients remained ambulatory over a mean disease duration of 19.71 ± 13.70 years. Characterisation of C. elegans RTN2 homolog loss-of-function variants demonstrated morphological and behavioural differences compared to the parental strain. Treatment of the mutant with an endoplasmic/sarcoplasmic reticulum Ca2+ reuptake inhibitor (2,5-di-tert-butylhydroquinone) rescued key phenotypic differences, suggesting a potential therapeutic benefit for RTN2-disorder. Despite Reticulon-2 being an endoplasmic reticulum (ER)-resident membrane shaping protein, our analysis of patient fibroblast cells did not find significant alterations in ER structure or the response to ER stress. Our findings delineate a distinct form of autosomal recessive dHMN with pyramidal features associated with Reticulon-2 deficiency. This phenotype shares similarities with SIGMAR1-related dHMN, and Silver-like syndromes, providing valuable insights into the clinical spectrum and potential therapeutic strategies for RTN2-related dHMN.

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Drosophila SPG12 ortholog, reticulon-like 1, governs presynaptic ER organization and Ca2+ dynamics

Cited by 6 publications

References 63 publications

High-resolution imaging of presynaptic ER networks inAtlastinmutants

High-resolution imaging of presynaptic ER networks inAtlastinmutants

Loss of Fic causes progressive neurodegeneration in a Drosophila model of hereditary spastic paraplegia

RTN2 deficiency results in an autosomal recessive distal motor neuropathy with lower limb spasticity

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