scholarly journals Soluble and insoluble dipeptide repeat protein measurements in C9orf72-frontotemporal dementia brains show regional differential solubility and correlation of poly-GR with clinical severity

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Annelies Quaegebeur ◽  
Idoia Glaria ◽  
Tammaryn Lashley ◽  
Adrian M. Isaacs
Keyword(s):  
Frontotemporal Dementia ◽  
Potential Role ◽  
Brain Regions ◽  
Clinical Severity ◽  
Repeat Proteins ◽  
Differential Solubility ◽  
Shed Light ◽  
Lateral Sclerosis ◽  
Dipeptide Repeat

Abstract A C9orf72 repeat expansion is the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis. One of the suggested pathomechanisms is toxicity from dipeptide repeat proteins (DPRs), which are generated via unconventional translation of sense and antisense repeat transcripts with poly-GA, poly-GP and poly-GR being the most abundant dipeptide proteins. Animal and cellular studies highlight a neurotoxic role of poly-GR and poly-PR and to a lesser degree of poly-GA. Human post-mortem studies in contrast have been much less clear on a potential role of DPR toxicity but have largely focused on immunohistochemical methods to detect aggregated DPR inclusions. This study uses protein fractionation and sensitive immunoassays to quantify not only insoluble but also soluble poly-GA, poly-GP and poly-GR concentrations in brain homogenates of FTD patients with C9orf72 mutation across four brain regions. We show that soluble DPRs are less abundant in clinically affected areas (i.e. frontal and temporal cortices). In contrast, the cerebellum not only shows the largest DPR load but also the highest relative DPR solubility. Finally, poly-GR levels and poly-GP solubility correlate with clinical severity. These findings provide the first cross-comparison of soluble and insoluble forms of all sense DPRs and shed light on the distribution and role of soluble DPRs in the etiopathogenesis of human C9orf72-FTD.

Order controls disordered droplets: structure-function relationships in C9orf72-derived poly(PR)

2021 ◽  
Author(s):  
Kohsuke Kanekura ◽  
Yuhei Hayamizu ◽  
Masahiko Kuroda
Keyword(s):  
Amino Acids ◽  
Aromatic Amino Acids ◽  
Polar Amino Acid ◽  
Repeat Proteins ◽  
Intron 1 ◽  
Lateral Sclerosis ◽  
Ran Translation ◽  
Dipeptide Repeat ◽  
Positively Charged

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) have been thought as two distinct neurodegenerative diseases. However, recent genetic screening and careful investigations found the genetic and pathological overlap among these disorders. Hexanucleotide expansions in intron 1 of C9orf72 are a leading cause of familial ALS and familial FTD. These expansions facilitate the repeat-associated non-ATG initiated translation (RAN translation), producing five dipeptide repeat proteins (DRPs), including Arg-rich poly(PR: Pro-Arg) and poly-(GR: Gly-Arg) peptides. Arg is a positively charged, highly polar amino acid that facilitates interactions with anionic molecules such as nucleic acids and acidic amino acids via electrostatic forces and aromatic amino acids via cation-pi interaction, suggesting that Arg-rich DRPs underlie the pathophysiology of ALS via Arg-mediated molecular interactions. Arg-rich DRPs have also been reported to induce neurodegeneration in cellular and animal models via multiple mechanisms; however, it remains unclear why the Arg-rich DRPs exhibit such diverse toxic properties, because not all Arg-rich peptides are toxic. In this mini-review, we discuss the current understanding of the pathophysiology of Arg-rich C9orf72 DRPs and introduce recent findings on the role of Arg distribution as a determinant of the toxicity and its contribution to the pathogenesis of ALS.

scholarly journals SFPQ regulates the accumulation of RNA foci and dipeptide repeat proteins from the expanded repeat mutation in C9orf72

2021 ◽  
Vol 134 (4) ◽  
pp. jcs256602 ◽  
Author(s):  
Mirjana Malnar ◽  
Boris Rogelj
Keyword(s):  
Antisense Rna ◽  
Rna Binding ◽  
Dipeptide Repeat Proteins ◽  
Rna Transcripts ◽  
Repeat Proteins ◽  
Rna Foci ◽  
Hek Cells ◽  
Lateral Sclerosis ◽  
Dipeptide Repeat

ABSTRACTThe expanded GGGGCC repeat mutation in the C9orf72 gene is the most common genetic cause of the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The expansion is transcribed to sense and antisense RNA, which form RNA foci and bind cellular proteins. This mechanism of action is considered cytotoxic. Translation of the expanded RNA transcripts also leads to the accumulation of toxic dipeptide repeat proteins (DPRs). The RNA-binding protein splicing factor proline and glutamine rich (SFPQ), which is being increasingly associated with ALS and FTD pathology, binds to sense RNA foci. Here, we show that SFPQ plays an important role in the C9orf72 mutation. Overexpression of SFPQ resulted in higher numbers of both sense and antisense RNA foci and DPRs in transfected human embryonic kidney (HEK) cells. Conversely, reduced SPFQ levels resulted in lower numbers of RNA foci and DPRs in both transfected HEK cells and C9orf72 mutation-positive patient-derived fibroblasts and lymphoblasts. Therefore, we have revealed a role of SFPQ in regulating the C9orf72 mutation that has implications for understanding and developing novel therapeutic targets for ALS and FTD.This article has an associated First Person interview with the first author of the paper.

scholarly journals Hippocampal protein aggregation signatures fully distinguish pathogenic and wildtype UBQLN2 in amyotrophic lateral sclerosis

2022 ◽  
Author(s):  
Kyrah M Thumbadoo ◽  
Birger V Dieriks ◽  
Helen C Murray ◽  
Molly EV Swanson ◽  
Ji Hun Yoo ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Protein Aggregation ◽  
Gene Mutations ◽  
Repeat Proteins ◽  
Familial Als ◽  
Fluorescent Immunohistochemistry ◽  
Self Aggregation ◽  
Lateral Sclerosis ◽  
Dipeptide Repeat

Mutations in the UBQLN2 gene cause X-linked dominant amyotrophic lateral sclerosis (ALS) and/or frontotemporal dementia (FTD) characterised by ubiquilin 2 aggregates in neurons of the motor cortex, hippocampus, cerebellum, and spinal cord. However, ubiquilin 2 neuropathology is also seen in sporadic and familial ALS or FTD cases not caused by UBQLN2 mutations, particularly C9ORF72-linked cases. This makes the mechanistic role of ubiquilin 2 mutations and the value of ubiquilin 2 pathology for predicting genotype unclear. Here we examine a cohort of 31 genotypically diverse ALS cases with or without FTD, including four cases with UBQLN2 mutations (resulting in p.P497H, p.P506S, and two cases with p.T487I). Using double-, triple-, and six-label fluorescent immunohistochemistry, we mapped the co-localisation of ubiquilin 2 with phosphorylated TDP-43 (pTDP-43), dipeptide repeat aggregates, and p62, in the hippocampus of controls (n=5), or ALS with or without FTD in sporadic (n=19), unknown familial (n=3), SOD1-linked (n=1), C9ORF72-linked (n=4), and UBQLN2-linked (n=4) cases. We differentiate between i) ubiquilin 2 aggregation together with, or driven by, pTDP-43 or dipeptide repeat proteins, and ii) ubiquilin 2 self-aggregation driven by UBQLN2 gene mutations. Together we describe a hippocampal protein aggregation signature that fully distinguishes mutant from wildtype ubiquilin 2 in ALS with or without FTD, whereby mutant ubiquilin 2 is more prone than wildtype to aggregate independently of driving factors. This neuropathological signature can be used to assess the pathogenicity of UBQLN2 gene mutations and to understand the mechanisms of UBQLN2-linked disease.

scholarly journals Modeling C9orf72-Related Frontotemporal Dementia and Amyotrophic Lateral Sclerosis in Drosophila

2021 ◽  
Vol 15 ◽  
Author(s):  
Joanne L. Sharpe ◽  
Nikki S. Harper ◽  
Duncan R. Garner ◽  
Ryan J. H. West
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Frontotemporal Dementia ◽  
Loss Of Function ◽  
Gain Of Function ◽  
Dipeptide Repeat Proteins ◽  
Repeat Proteins ◽  
Individual Contributions ◽  
The Individual ◽  
Lateral Sclerosis ◽  
Dipeptide Repeat

An intronic hexanucleotide (GGGGCC) expansion in the C9orf72 gene is the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). In the decade following its discovery, much progress has been made in enhancing our understanding of how it precipitates disease. Both loss of function caused by reduced C9orf72 transcript levels, and gain of function mechanisms, triggered by the production of repetitive sense and antisense RNA and dipeptide repeat proteins, are thought to contribute to the toxicity. Drosophila models, with their unrivaled genetic tractability and short lifespan, have played a key role in developing our understanding of C9orf72-related FTD/ALS. There is no C9orf72 homolog in fly, and although this precludes investigations into loss of function toxicity, it is useful for elucidating mechanisms underpinning gain of function toxicity. To date there are a range of Drosophila C9orf72 models, encompassing different aspects of gain of function toxicity. In addition to pure repeat transgenes, which produce both repeat RNA and dipeptide repeat proteins (DPRs), RNA only models and DPR models have been generated to unpick the individual contributions of RNA and each dipeptide repeat protein to C9orf72 toxicity. In this review, we discuss how Drosophila models have shaped our understanding of C9orf72 gain of function toxicity, and address opportunities to utilize these models for further research.

scholarly journals The nuclear ubiquitin ligase adaptor SPOP is a conserved regulator of C9orf72 dipeptide toxicity

2021 ◽  
Author(s):  
Carley Snoznik ◽  
Valentina Medvedeva ◽  
Jelena Mojsilovic-Petrovic ◽  
Paige Rudich ◽  
James Oosten ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Nuclear Localization ◽  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Repeat Expansion ◽  
Dipeptide Repeat Proteins ◽  
C Elegans ◽  
Repeat Proteins ◽  
Lateral Sclerosis ◽  
Dipeptide Repeat

AbstractA hexanucleotide repeat expansion in the C9orf72 gene is the most common cause of inherited amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Unconventional translation of the C9orf72 repeat produces dipeptide repeat proteins (DPRs). Previously, we showed that the DPRs (PR)50 and (GR)50 are highly toxic when expressed in C. elegans and this toxicity depends on nuclear localization of the DPR. In an unbiased genome-wide RNAi screen for suppressors of (PR)50 toxicity, we identified 12 genes that consistently suppressed either the developmental arrest and/or paralysis phenotype evoked by (PR)50 expression. All of these genes have vertebrate homologs and 7/12 contain predicted nuclear localization signals. One of these genes was spop-1, the C. elegans homolog of SPOP, a nuclear localized E3 ubiquitin ligase adaptor only found in metazoans. SPOP is also required for (GR)50 toxicity and functions in a genetic pathway that includes cul-3, which is the canonical E3 ligase partner for SPOP. Genetic or pharmacological inhibition of SPOP in mammalian primary spinal cord motor neurons suppressed DPR toxicity without affecting DPR expression levels. Finally, we find that genetic inhibition of bet-1, the C. elegans homolog of the known SPOP ubiquitination targets BRD2/3/4, suppresses the protective effect of SPOP mutations. Together, these data suggest a model in which SPOP promotes the DPR-dependent ubiquitination and degradation of BRD proteins. We speculate the pharmacological manipulation of this pathway, which is currently underway for multiple cancer subtypes, could also represent a novel entry point for therapeutic intervention to treat C9 FTD/ALS.Significance statementThe G4C2 repeat expansion in the C9orf72 gene is a major cause of Fronto-Temporal Dementia (FTD) and Amyotrophic Lateral Sclerosis (ALS). Unusual translation of the repeat sequence produces two highly toxic dipeptide repeat proteins, PRX and GRX, which accumulate in the brain tissue of individuals with these diseases. Here, we show that PR and GR toxicity in both C. elegans and mammalian neurons depends on the E3 ubiquitin ligase adaptor SPOP. SPOP acts through the bromodomain protein BET-1 to mediate dipeptide toxicity. SPOP inhibitors, which are currently being developed to treat SPOP-dependent renal cancer, also protect neurons against DPR toxicity. Our findings identify a highly conserved and ‘druggable’ pathway that may represent a new strategy for treating these currently incurable diseases.

Hemodynamic responses and c-Fos changes associated with hypotensive hemorrhage: standardizing a protocol for severe hemorrhage in conscious rats

2007 ◽  
Vol 292 (5) ◽  
pp. R1862-R1871 ◽  
Author(s):  
Joslyn Ahlgren ◽  
Karen Porter ◽  
Linda F. Hayward
Keyword(s):  
Potential Role ◽  
Cardiovascular Response ◽  
Brain Regions ◽  
Total Blood Volume ◽  
Total Blood ◽  
Conscious Rats ◽  
Cuneiform Nucleus ◽  
Severe Hemorrhage ◽  
Lateral Nucleus

The central mechanisms underlying the transition from compensation to decompensation during severe hemorrhage (HEM) are poorly understood. Furthermore, a lack of consistency in HEM protocols exists in the current literature. This study assessed the cardiovascular response and Fos-like immunoreactivity (FLI) in specific brain regions following severe HEM at three rates (2, 1, or 0.5 ml·kg−1·min−1) in conscious rats. Heart rate (HR) and arterial pressure were recorded during the withdrawal of 30% of total blood volume (TBV). Data from animals hemorrhaged at the fast (F-HEM, n = 6), intermediate (I-HEM, n = 7), or slow (S-HEM, n = 7) rates were compared with saline (SAL, n = 5) and hypotensive (hydrazaline-induced, HYDRAZ, n = 5) controls. All HEM rates produced similar degrees of hypotension at the time of 30% TBV withdrawal. All HEM rates also produced bradycardia, but the change in HR was only significant in the F-HEM and I-HEM groups. Associated with I-HEM and F-HEM, but not HYDRAZ treatment were significant increases in FLI in the caudal ventrolateral periaqueductal gray (PAG), the central lateral nucleus of the rostral parabrachial nucleus, and locus coeruleus compared with SAL treatment. I-HEM also induced significant increases in FLI in the dorsomedial PAG, A7 region, and the cuneiform nucleus compared with SAL. S-HEM did not induce any significant change in FLI. Our results suggest that HEM at a rate of 1 ml·kg−1·min−1 may be most useful for investigating the potential role of the rostral brainstem regions in mediating hemorrhagic decompensation in conscious rats.

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