Publications by authors named "Marka Van Blitterswijk"

69 Publications

Long-read targeted sequencing uncovers clinicopathological associations for C9orf72-linked diseases.

Brain 2021 May;144(4):1082-1088

Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA.

To examine the length of a hexanucleotide expansion in C9orf72, which represents the most frequent genetic cause of frontotemporal lobar degeneration and motor neuron disease, we employed a targeted amplification-free long-read sequencing technology: No-Amp sequencing. In our cross-sectional study, we assessed cerebellar tissue from 28 well-characterized C9orf72 expansion carriers. We obtained 3507 on-target circular consensus sequencing reads, of which 814 bridged the C9orf72 repeat expansion (23%). Importantly, we observed a significant correlation between expansion sizes obtained using No-Amp sequencing and Southern blotting (P = 5.0 × 10-4). Interestingly, we also detected a significant survival advantage for individuals with smaller expansions (P = 0.004). Additionally, we uncovered that smaller expansions were significantly associated with higher levels of C9orf72 transcripts containing intron 1b (P = 0.003), poly(GP) proteins (P = 1.3 × 10- 5), and poly(GA) proteins (P = 0.005). Thorough examination of the composition of the expansion revealed that its GC content was extremely high (median: 100%) and that it was mainly composed of GGGGCC repeats (median: 96%), suggesting that expanded C9orf72 repeats are quite pure. Taken together, our findings demonstrate that No-Amp sequencing is a powerful tool that enables the discovery of relevant clinicopathological associations, highlighting the important role played by the cerebellar size of the expanded repeat in C9orf72-linked diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/brain/awab006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8105038PMC
May 2021

-derived arginine-containing dipeptide repeats associate with axonal transport machinery and impede microtubule-based motility.

Sci Adv 2021 Apr 9;7(15). Epub 2021 Apr 9.

KU Leuven-University of Leuven, Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), Leuven, Belgium.

A hexanucleotide repeat expansion in the gene is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). How this mutation leads to these neurodegenerative diseases remains unclear. Here, we show using patient stem cell-derived motor neurons that the repeat expansion impairs microtubule-based transport, a process critical for neuronal survival. Cargo transport defects are recapitulated by treating neurons from healthy individuals with proline-arginine and glycine-arginine dipeptide repeats (DPRs) produced from the repeat expansion. Both arginine-rich DPRs similarly inhibit axonal trafficking in adult neurons in vivo. Physical interaction studies demonstrate that arginine-rich DPRs associate with motor complexes and the unstructured tubulin tails of microtubules. Single-molecule imaging reveals that microtubule-bound arginine-rich DPRs directly impede translocation of purified dynein and kinesin-1 motor complexes. Collectively, our study implicates inhibitory interactions of arginine-rich DPRs with axonal transport machinery in -associated ALS/FTD and thereby points to potential therapeutic strategies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/sciadv.abg3013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8034861PMC
April 2021

Unravelling the clinical spectrum and the role of repeat length in repeat expansions.

J Neurol Neurosurg Psychiatry 2021 May 15;92(5):502-509. Epub 2021 Jan 15.

Department of Neurology and Alzheimer Center, Erasmus University Medical Center, Rotterdam, Netherlands

Since the discovery of the repeat expansion as the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis, it has increasingly been associated with a wider spectrum of phenotypes, including other types of dementia, movement disorders, psychiatric symptoms and slowly progressive FTD. Prompt recognition of patients with -associated diseases is essential in light of upcoming clinical trials. The striking clinical heterogeneity associated with repeat expansions remains largely unexplained. In contrast to other repeat expansion disorders, evidence for an effect of repeat length on phenotype is inconclusive. Patients with -associated diseases typically have very long repeat expansions, containing hundreds to thousands of GGGGCC-repeats, but smaller expansions might also have clinical significance. The exact threshold at which repeat expansions lead to neurodegeneration is unknown, and discordant cut-offs between laboratories pose a challenge for genetic counselling. Accurate and large-scale measurement of repeat expansions has been severely hindered by technical difficulties in sizing long expansions and by variable repeat lengths across and within tissues. Novel long-read sequencing approaches have produced promising results and open up avenues to further investigate this enthralling repeat expansion, elucidating whether its length, purity, and methylation pattern might modulate clinical features of -related diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/jnnp-2020-325377DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8053328PMC
May 2021

Toward allele-specific targeting therapy and pharmacodynamic marker for spinocerebellar ataxia type 3.

Sci Transl Med 2020 10;12(566)

Department of Pathology, Brain Research Institute, Niigata University, Niigata 951-8585, Japan.

Spinocerebellar ataxia type 3 (SCA3), caused by a CAG repeat expansion in the ataxin-3 gene (), is characterized by neuronal polyglutamine (polyQ) ATXN3 protein aggregates. Although there is no cure for SCA3, gene-silencing approaches to reduce toxic polyQ ATXN3 showed promise in preclinical models. However, a major limitation in translating putative treatments for this rare disease to the clinic is the lack of pharmacodynamic markers for use in clinical trials. Here, we developed an immunoassay that readily detects polyQ ATXN3 proteins in human biological fluids and discriminates patients with SCA3 from healthy controls and individuals with other ataxias. We show that polyQ ATXN3 serves as a marker of target engagement in human fibroblasts, which may bode well for its use in clinical trials. Last, we identified a single-nucleotide polymorphism that strongly associates with the expanded allele, thus providing an exciting drug target to abrogate detrimental events initiated by mutant ATXN3. Gene-silencing strategies for several repeat diseases are well under way, and our results are expected to improve clinical trial preparedness for SCA3 therapies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/scitranslmed.abb7086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7927160PMC
October 2020

Truncated stathmin-2 is a marker of TDP-43 pathology in frontotemporal dementia.

J Clin Invest 2020 11;130(11):6080-6092

Center for Genomics of Neurodegenerative Disease, and.

No treatment for frontotemporal dementia (FTD), the second most common type of early-onset dementia, is available, but therapeutics are being investigated to target the 2 main proteins associated with FTD pathological subtypes: TDP-43 (FTLD-TDP) and tau (FTLD-tau). Testing potential therapies in clinical trials is hampered by our inability to distinguish between patients with FTLD-TDP and FTLD-tau. Therefore, we evaluated truncated stathmin-2 (STMN2) as a proxy of TDP-43 pathology, given the reports that TDP-43 dysfunction causes truncated STMN2 accumulation. Truncated STMN2 accumulated in human induced pluripotent stem cell-derived neurons depleted of TDP-43, but not in those with pathogenic TARDBP mutations in the absence of TDP-43 aggregation or loss of nuclear protein. In RNA-Seq analyses of human brain samples from the NYGC ALS cohort, truncated STMN2 RNA was confined to tissues and disease subtypes marked by TDP-43 inclusions. Last, we validated that truncated STMN2 RNA was elevated in the frontal cortex of a cohort of patients with FTLD-TDP but not in controls or patients with progressive supranuclear palsy, a type of FTLD-tau. Further, in patients with FTLD-TDP, we observed significant associations of truncated STMN2 RNA with phosphorylated TDP-43 levels and an earlier age of disease onset. Overall, our data uncovered truncated STMN2 as a marker for TDP-43 dysfunction in FTD.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1172/JCI139741DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7598060PMC
November 2020

Elevated methylation levels, reduced expression levels, and frequent contractions in a clinical cohort of C9orf72 expansion carriers.

Mol Neurodegener 2020 01 30;15(1). Epub 2020 Jan 30.

Department of Neuroscience, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL, 32224, USA.

Background: A repeat expansion in the C9orf72-SMCR8 complex subunit (C9orf72) is the most common genetic cause of two debilitating neurodegenerative diseases: amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Currently, much remains unknown about which variables may modify these diseases. We sought to investigate associations between C9orf72 promoter methylation, RNA expression levels, and repeat length, their potential effects on disease features, as well as changes over time and within families.

Methods: All samples were obtained through the ALS Center at Mayo Clinic Florida. Our primary cohort included 75 unrelated patients with an expanded C9orf72 repeat, 33 patients who did not possess this expansion, and 20 control subjects without neurodegenerative diseases. Additionally, 67 members from 17 independent C9orf72 families were selected of whom 33 harbored this expansion. Longitudinally collected samples were available for 35 C9orf72 expansion carriers. To increase our understanding of C9orf72-related diseases, we performed quantitative methylation-sensitive restriction enzyme-based assays, digital molecular barcoding, quantitative real-time PCR, and Southern blotting.

Results: In our primary cohort, higher methylation levels were observed in patients with a C9orf72 repeat expansion than in patients without this expansion (p = 1.7e-13) or in control subjects (p = 3.3e-07). Moreover, we discovered that an increase in methylation levels was associated with a decrease in total C9orf72 transcript levels (p = 5.5e-05). These findings aligned with our observation that C9orf72 expansion carriers had lower expression levels of total C9orf72 transcripts than patients lacking this expansion (p = 3.7e-07) or control subjects (p = 9.1e-05). We also detected an elevation of transcripts containing intron 1a (upstream of the repeat) in patients carrying a C9orf72 repeat expansion compared to (disease) controls (p ≤ 0.01), an indication of abortive transcripts and/or a switch in transcription start site usage. While methylation and expression levels were relatively stable over time, fluctuations were seen in repeat length. Interestingly, contractions occurred frequently in parent-offspring transmissions (> 50%), especially in paternal transmissions. Furthermore, smaller repeat lengths were detected in currently unaffected individuals than in affected individuals (p = 8.9e-04) and they were associated with an earlier age at collection (p = 0.008).

Conclusions: In blood from C9orf72 expansion carriers, we found elevated methylation levels, reduced expression levels, and unstable expansions that tend to contract in successive generations, arguing against anticipation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s13024-020-0359-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6993399PMC
January 2020

Genetic screening of a large series of North American sporadic and familial frontotemporal dementia cases.

Alzheimers Dement 2020 01;16(1):118-130

University of California, San Francisco, San Francisco, California.

Introduction: The Advancing Research and Treatment for Frontotemporal Lobar Degeneration (ARTFL) and Longitudinal Evaluation of Familial Frontotemporal Dementia Subjects (LEFFTDS) consortia are two closely connected studies, involving multiple North American centers that evaluate both sporadic and familial frontotemporal dementia (FTD) participants and study longitudinal changes.

Methods: We screened the major dementia-associated genes in 302 sporadic and 390 familial (symptomatic or at-risk) participants enrolled in these studies.

Results: Among the sporadic patients, 16 (5.3%) carried chromosome 9 open reading frame 72 (C9orf72), microtubule-associated protein tau (MAPT), and progranulin (GRN) pathogenic variants, whereas in the familial series we identified 207 carriers from 146 families. Of interest, one patient was found to carry a homozygous C9orf72 expansion, while another carried both a C9orf72 expansion and a GRN pathogenic variant. We also identified likely pathogenic variants in the TAR DNA binding protein (TARDBP), presenilin 1 (PSEN1), and valosin containing protein (VCP) genes, and a subset of variants of unknown significance in other rare FTD genes.

Discussion: Our study reports the genetic characterization of a large FTD series and supports an unbiased sequencing screen, irrespective of clinical presentation or family history.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/alz.12011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7199807PMC
January 2020

Extensive transcriptomic study emphasizes importance of vesicular transport in C9orf72 expansion carriers.

Acta Neuropathol Commun 2019 10 8;7(1):150. Epub 2019 Oct 8.

Department of Neuroscience, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL, 32224, USA.

The majority of the clinico-pathological variability observed in patients harboring a repeat expansion in the C9orf72-SMCR8 complex subunit (C9orf72) remains unexplained. This expansion, which represents the most common genetic cause of frontotemporal lobar degeneration (FTLD) and motor neuron disease (MND), results in a loss of C9orf72 expression and the generation of RNA foci and dipeptide repeat (DPR) proteins. The C9orf72 protein itself plays a role in vesicular transport, serving as a guanine nucleotide exchange factor that regulates GTPases. To further elucidate the mechanisms underlying C9orf72-related diseases and to identify potential disease modifiers, we performed an extensive RNA sequencing study. We included individuals for whom frontal cortex tissue was available: FTLD and FTLD/MND patients with (n = 34) or without (n = 44) an expanded C9orf72 repeat as well as control subjects (n = 24). In total, 6706 genes were differentially expressed between these groups (false discovery rate [FDR] < 0.05). The top gene was C9orf72 (FDR = 1.41E-14), which was roughly two-fold lower in C9orf72 expansion carriers than in (disease) controls. Co-expression analysis revealed groups of correlated genes (modules) that were enriched for processes such as protein folding, RNA splicing, synaptic signaling, metabolism, and Golgi vesicle transport. Within our cohort of C9orf72 expansion carriers, machine learning uncovered interesting candidates associated with clinico-pathological features, including age at onset (vascular endothelial growth factor A [VEGFA]), C9orf72 expansion size (cyclin dependent kinase like 1 [CDKL1]), DPR protein levels (eukaryotic elongation factor 2 kinase [EEF2K]), and survival after onset (small G protein signaling modulator 3 [SGSM3]). Given the fact that we detected a module involved in vesicular transport in addition to a GTPase activator (SGSM3) as a potential modifier, our findings seem to suggest that the presence of a C9orf72 repeat expansion might hamper vesicular transport and that genes affecting this process may modify the phenotype of C9orf72-linked diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s40478-019-0797-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6781370PMC
October 2019

Microglia in frontotemporal lobar degeneration with progranulin or C9ORF72 mutations.

Ann Clin Transl Neurol 2019 09 25;6(9):1782-1796. Epub 2019 Aug 25.

Department of Neuroscience, Mayo Clinic, Jacksonville, Florida.

Objective: To identify clinicopathological differences between frontotemporal lobar degeneration (FTLD) due to mutations in progranulin (FTLD-GRN) and chromosome 9 open reading frame 72 (FTLD-C9ORF72).

Methods: We performed quantitative neuropathologic comparison of 17 FTLD-C9ORF72 and 15 FTLD-GRN with a focus on microglia. For clinical comparisons, only cases with high quality medical documentation and concurring diagnoses by at least two neurologists were included (14 FTLD-GRN and 13 FTLD-C9ORF72). Neuropathological analyses were limited to TDP-43 Type A to assure consistent assessment between the groups, acknowledging that Type A is a minority of C9ORF72 patients. Furthermore, only cases with sufficient tissue from all regions were studied (11 FTLD-GRN and 11 FTLD-C9ORF72). FTLD cases were also compared to age- and sex-matched normal controls. Immunohistochemistry was performed for pTDP-43, IBA-1, CD68, and GFAP. Morphological characterization of microglia was performed in sections of cortex blinded to clinical and genetic information.

Results: FTLD-GRN patients had frequent asymmetric clinical features, including aphasia and apraxia, as well as more asymmetric cortical atrophy. Neuropathologically, FTLD-C9ORF72 had greater hippocampal tau pathology and more TDP-43 neuronal cytoplasmic inclusions. FTLD-GRN had more neocortical microvacuolation, as well as more IBA-1-positive ameboid microglia in superficial cortical layers and in subcortical white matter. FTLD-GRN also had more microglia with nuclear condensation, possibly indicating apoptosis. Microglial morphology with CD68 immunohistochemistry in FTLD-GRN and FTLD-C9ORF72 differed from controls.

Interpretation: Our findings underscore differences in microglial response in FTLD-C9ORF72 and FTLD-GRN as shown by significant differences in ameboid microglia in gray and white matter. These results suggest the differential contribution of microglial dysfunction in FTLD-GRN and FTLD-C9ORF72 and suggest that clinical, neuroimaging and pathologic differences could in part be related to differences in microglia response.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/acn3.50875DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6764493PMC
September 2019

Genome-wide analyses as part of the international FTLD-TDP whole-genome sequencing consortium reveals novel disease risk factors and increases support for immune dysfunction in FTLD.

Acta Neuropathol 2019 06 9;137(6):879-899. Epub 2019 Feb 9.

German Center for Neurodegenerative Diseases (DZNE), 18147, Rostock, Germany.

Frontotemporal lobar degeneration with neuronal inclusions of the TAR DNA-binding protein 43 (FTLD-TDP) represents the most common pathological subtype of FTLD. We established the international FTLD-TDP whole-genome sequencing consortium to thoroughly characterize the known genetic causes of FTLD-TDP and identify novel genetic risk factors. Through the study of 1131 unrelated Caucasian patients, we estimated that C9orf72 repeat expansions and GRN loss-of-function mutations account for 25.5% and 13.9% of FTLD-TDP patients, respectively. Mutations in TBK1 (1.5%) and other known FTLD genes (1.4%) were rare, and the disease in 57.7% of FTLD-TDP patients was unexplained by the known FTLD genes. To unravel the contribution of common genetic factors to the FTLD-TDP etiology in these patients, we conducted a two-stage association study comprising the analysis of whole-genome sequencing data from 517 FTLD-TDP patients and 838 controls, followed by targeted genotyping of the most associated genomic loci in 119 additional FTLD-TDP patients and 1653 controls. We identified three genome-wide significant FTLD-TDP risk loci: one new locus at chromosome 7q36 within the DPP6 gene led by rs118113626 (p value = 4.82e - 08, OR = 2.12), and two known loci: UNC13A, led by rs1297319 (p value = 1.27e - 08, OR = 1.50) and HLA-DQA2 led by rs17219281 (p value = 3.22e - 08, OR = 1.98). While HLA represents a locus previously implicated in clinical FTLD and related neurodegenerative disorders, the association signal in our study is independent from previously reported associations. Through inspection of our whole-genome sequence data for genes with an excess of rare loss-of-function variants in FTLD-TDP patients (n ≥ 3) as compared to controls (n = 0), we further discovered a possible role for genes functioning within the TBK1-related immune pathway (e.g., DHX58, TRIM21, IRF7) in the genetic etiology of FTLD-TDP. Together, our study based on the largest cohort of unrelated FTLD-TDP patients assembled to date provides a comprehensive view of the genetic landscape of FTLD-TDP, nominates novel FTLD-TDP risk loci, and strongly implicates the immune pathway in FTLD-TDP pathogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00401-019-01962-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6533145PMC
June 2019

Long-read sequencing across the C9orf72 'GGGGCC' repeat expansion: implications for clinical use and genetic discovery efforts in human disease.

Mol Neurodegener 2018 08 21;13(1):46. Epub 2018 Aug 21.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA.

Background: Many neurodegenerative diseases are caused by nucleotide repeat expansions, but most expansions, like the C9orf72 'GGGGCC' (GC) repeat that causes approximately 5-7% of all amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) cases, are too long to sequence using short-read sequencing technologies. It is unclear whether long-read sequencing technologies can traverse these long, challenging repeat expansions. Here, we demonstrate that two long-read sequencing technologies, Pacific Biosciences' (PacBio) and Oxford Nanopore Technologies' (ONT), can sequence through disease-causing repeats cloned into plasmids, including the FTD/ALS-causing GC repeat expansion. We also report the first long-read sequencing data characterizing the C9orf72 GC repeat expansion at the nucleotide level in two symptomatic expansion carriers using PacBio whole-genome sequencing and a no-amplification (No-Amp) targeted approach based on CRISPR/Cas9.

Results: Both the PacBio and ONT platforms successfully sequenced through the repeat expansions in plasmids. Throughput on the MinION was a challenge for whole-genome sequencing; we were unable to attain reads covering the human C9orf72 repeat expansion using 15 flow cells. We obtained 8× coverage across the C9orf72 locus using the PacBio Sequel, accurately reporting the unexpanded allele at eight repeats, and reading through the entire expansion with 1324 repeats (7941 nucleotides). Using the No-Amp targeted approach, we attained > 800× coverage and were able to identify the unexpanded allele, closely estimate expansion size, and assess nucleotide content in a single experiment. We estimate the individual's repeat region was > 99% GC content, though we cannot rule out small interruptions.

Conclusions: Our findings indicate that long-read sequencing is well suited to characterizing known repeat expansions, and for discovering new disease-causing, disease-modifying, or risk-modifying repeat expansions that have gone undetected with conventional short-read sequencing. The PacBio No-Amp targeted approach may have future potential in clinical and genetic counseling environments. Larger and deeper long-read sequencing studies in C9orf72 expansion carriers will be important to determine heterogeneity and whether the repeats are interrupted by non-GC content, potentially mitigating or modifying disease course or age of onset, as interruptions are known to do in other repeat-expansion disorders. These results have broad implications across all diseases where the genetic etiology remains unclear.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s13024-018-0274-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6102925PMC
August 2018

TMEM106B haplotypes have distinct gene expression patterns in aged brain.

Mol Neurodegener 2018 07 3;13(1):35. Epub 2018 Jul 3.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.

Background: Single nucleotide polymorphisms (SNPs) inherited as one of two common haplotypes at the transmembrane protein 106B (TMEM106B) locus are associated with the risk of multiple neurodegenerative diseases, including frontotemporal lobar degeneration with pathological inclusions of TDP-43. Among the associated variants, rs3173615 (encoding p.T185S) is the only coding variant; however, non-coding variants may also contribute to disease risk. It has been reported that the risk haplotype is associated with higher levels of TMEM106B and increased levels of TMEM106B cause cytotoxicity; however, the precise mechanism through which TMEM106B haplotypes contribute to neurodegeneration is unclear.

Methods: We utilized RNA sequencing data derived from temporal cortex (TCX) and cerebellum (CER) from 312 North American Caucasian subjects neuropathologically diagnosed with Alzheimer's disease, progressive supranuclear palsy, pathological aging or normal controls to analyze transcriptome signatures associated with the risk (TT) and protective (SS) TMEM106B haplotypes. In cohorts matched for disease phenotype, we used Analysis of Variance (ANOVA) to identify differentially expressed genes and Weighted Gene Co-expression Network Analysis (WGCNA) to identify gene networks associated with the risk and protective TMEM106B haplotypes.

Results: A total of 110 TCX and 116 CER samples were included in the analyses. When comparing TT to SS carriers, we detected 593 differentially expressed genes in TCX and 7 in CER. Gene co-expression network analyses further showed that in both TCX and CER the SS haplotype was positively correlated with gene networks involved in synaptic transmission, whereas the TT haplotype was positively correlated with gene networks enriched for immune response. Gene expression patterns of 5 cell-type-specific markers revealed significantly reduced expression of the neuronal marker and relative increases in all other cell markers in TT as compared to SS carriers in TCX with a similar but non-significant trend in CER.

Conclusions: By comparing the common TMEM106B risk and protective haplotypes we identified significant and partly conserved transcriptional differences across TCX and CER and striking changes in cell-type composition, especially in TCX. These findings illustrate the profound effect of TMEM106B haplotypes on brain health and highlight the importance to better understand TMEM106B's function and dysfunction in the context of neurodegenerative diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s13024-018-0268-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6029036PMC
July 2018

Potential genetic modifiers of disease risk and age at onset in patients with frontotemporal lobar degeneration and GRN mutations: a genome-wide association study.

Lancet Neurol 2018 06 30;17(6):548-558. Epub 2018 Apr 30.

Department of Neurological-Psychiatric Nursing, Medical University of Gdansk, Gdansk, Poland.

Background: Loss-of-function mutations in GRN cause frontotemporal lobar degeneration (FTLD). Patients with GRN mutations present with a uniform subtype of TAR DNA-binding protein 43 (TDP-43) pathology at autopsy (FTLD-TDP type A); however, age at onset and clinical presentation are variable, even within families. We aimed to identify potential genetic modifiers of disease onset and disease risk in GRN mutation carriers.

Methods: The study was done in three stages: a discovery stage, a replication stage, and a meta-analysis of the discovery and replication data. In the discovery stage, genome-wide logistic and linear regression analyses were done to test the association of genetic variants with disease risk (case or control status) and age at onset in patients with a GRN mutation and controls free of neurodegenerative disorders. Suggestive loci (p<1 × 10) were genotyped in a replication cohort of patients and controls, followed by a meta-analysis. The effect of genome-wide significant variants at the GFRA2 locus on expression of GFRA2 was assessed using mRNA expression studies in cerebellar tissue samples from the Mayo Clinic brain bank. The effect of the GFRA2 locus on progranulin concentrations was studied using previously generated ELISA-based expression data. Co-immunoprecipitation experiments in HEK293T cells were done to test for a direct interaction between GFRA2 and progranulin.

Findings: Individuals were enrolled in the current study between Sept 16, 2014, and Oct 5, 2017. After quality control measures, statistical analyses in the discovery stage included 382 unrelated symptomatic GRN mutation carriers and 1146 controls free of neurodegenerative disorders collected from 34 research centres located in the USA, Canada, Australia, and Europe. In the replication stage, 210 patients (67 symptomatic GRN mutation carriers and 143 patients with FTLD without GRN mutations pathologically confirmed as FTLD-TDP type A) and 1798 controls free of neurodegenerative diseases were recruited from 26 sites, 20 of which overlapped with the discovery stage. No genome-wide significant association with age at onset was identified in the discovery or replication stages, or in the meta-analysis. However, in the case-control analysis, we replicated the previously reported TMEM106B association (rs1990622 meta-analysis odds ratio [OR] 0·54, 95% CI 0·46-0·63; p=3·54 × 10), and identified a novel genome-wide significant locus at GFRA2 on chromosome 8p21.3 associated with disease risk (rs36196656 meta-analysis OR 1·49, 95% CI 1·30-1·71; p=1·58 × 10). Expression analyses showed that the risk-associated allele at rs36196656 decreased GFRA2 mRNA concentrations in cerebellar tissue (p=0·04). No effect of rs36196656 on plasma and CSF progranulin concentrations was detected by ELISA; however, co-immunoprecipitation experiments in HEK293T cells did suggest a direct binding of progranulin and GFRA2.

Interpretation: TMEM106B-related and GFRA2-related pathways might be future targets for treatments for FTLD, but the biological interaction between progranulin and these potential disease modifiers requires further study. TMEM106B and GFRA2 might also provide opportunities to select and stratify patients for future clinical trials and, when more is known about their potential effects, to inform genetic counselling, especially for asymptomatic individuals.

Funding: National Institute on Aging, National Institute of Neurological Disorders and Stroke, Canadian Institutes of Health Research, Italian Ministry of Health, UK National Institute for Health Research, National Health and Medical Research Council of Australia, and the French National Research Agency.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/S1474-4422(18)30126-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6237181PMC
June 2018

Repeat expansions in myoclonic epilepsy.

Nat Genet 2018 04;50(4):477-478

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41588-018-0093-0DOI Listing
April 2018

Genome-wide Analyses Identify KIF5A as a Novel ALS Gene.

Neuron 2018 03;97(6):1268-1283.e6

Department of Neurology, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Milan, Italy.

To identify novel genes associated with ALS, we undertook two lines of investigation. We carried out a genome-wide association study comparing 20,806 ALS cases and 59,804 controls. Independently, we performed a rare variant burden analysis comparing 1,138 index familial ALS cases and 19,494 controls. Through both approaches, we identified kinesin family member 5A (KIF5A) as a novel gene associated with ALS. Interestingly, mutations predominantly in the N-terminal motor domain of KIF5A are causative for two neurodegenerative diseases: hereditary spastic paraplegia (SPG10) and Charcot-Marie-Tooth type 2 (CMT2). In contrast, ALS-associated mutations are primarily located at the C-terminal cargo-binding tail domain and patients harboring loss-of-function mutations displayed an extended survival relative to typical ALS cases. Taken together, these results broaden the phenotype spectrum resulting from mutations in KIF5A and strengthen the role of cytoskeletal defects in the pathogenesis of ALS.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuron.2018.02.027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5867896PMC
March 2018

Unaffected mosaic case: RNA foci, dipeptide proteins, but upregulated C9orf72 expression.

Neurology 2018 01 27;90(4):e323-e331. Epub 2017 Dec 27.

From the Tanz Centre for Research in Neurodegenerative Diseases (P.M., M.Z., C.S., D.M., S.X., A.B.Z., P.M.M., A.W., R.S., J.R., E.R.), Department of Medicine (L.Z., E.R.), Division of Neurology, and Department of Laboratory Medicine and Pathobiology (J.R.), University of Toronto, Ontario, Canada; Department of Neuroscience (M.v.B., L.P., R.R.), Mayo Clinic, Jacksonville, FL; and Sunnybrook Health Sciences Centre (J.K., L.Z.), Toronto, Ontario, Canada.

Objective: Suggested disease mechanisms for amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration include haploinsufficiency, GC/CG RNA foci, and dipeptide repeat (DPR) proteins translated from the GC expansion; however, the role of small expansions (e.g., 30-90 repeats) is unknown and was investigated here.

Methods: We conducted a molecular and pathology study of a family in which the father (unaffected at age 90) carried a 70-repeat allele in blood DNA that expanded to ≈1,750 repeats in his children, causing ALS.

Results: Southern blotting revealed different degrees of mosaicism of small and large expansions in the father's tissues from the CNS. Surprisingly, in each mosaic tissue, mRNA levels were significantly increased compared to an ALS-affected daughter with a large expansion. Increased expression correlated with higher levels of the 70-repeat allele (the upregulation was also evident at the protein level). Remarkably, RNA foci and DPR burdens were similar or even significantly increased (in cerebellum) in the unaffected father compared to the daughter with ALS. However, the father did not display TDP-43 pathology and signs of neurodegeneration.

Conclusion: The presence of RNA foci and DPR pathology was insufficient for disease manifestation and TDP-43 pathology in the mosaic carrier with upregulated expression. It is important to conduct an investigation of similar cases, which could be found among unaffected parents of sporadic patients (e.g., 21% among Finnish patients with ALS). Caution should be taken when consulting carriers of small expansions because disease manifestation could be dependent on the extent of the somatic instability in disease-relevant tissues.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1212/WNL.0000000000004865DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5798652PMC
January 2018

Detection of long repeat expansions from PCR-free whole-genome sequence data.

Genome Res 2017 11 8;27(11):1895-1903. Epub 2017 Sep 8.

Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, King's College London, London SE5 9RX, United Kingdom.

Identifying large expansions of short tandem repeats (STRs), such as those that cause amyotrophic lateral sclerosis (ALS) and fragile X syndrome, is challenging for short-read whole-genome sequencing (WGS) data. A solution to this problem is an important step toward integrating WGS into precision medicine. We developed a software tool called ExpansionHunter that, using PCR-free WGS short-read data, can genotype repeats at the locus of interest, even if the expanded repeat is larger than the read length. We applied our algorithm to WGS data from 3001 ALS patients who have been tested for the presence of the repeat expansion with repeat-primed PCR (RP-PCR). Compared against this truth data, ExpansionHunter correctly classified all (212/212, 95% CI [0.98, 1.00]) of the expanded samples as either expansions (208) or potential expansions (4). Additionally, 99.9% (2786/2789, 95% CI [0.997, 1.00]) of the wild-type samples were correctly classified as wild type by this method with the remaining three samples identified as possible expansions. We further applied our algorithm to a set of 152 samples in which every sample had one of eight different pathogenic repeat expansions, including those associated with fragile X syndrome, Friedreich's ataxia, and Huntington's disease, and correctly flagged all but one of the known repeat expansions. Thus, ExpansionHunter can be used to accurately detect known pathogenic repeat expansions and provides researchers with a tool that can be used to identify new pathogenic repeat expansions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1101/gr.225672.117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5668946PMC
November 2017

Abnormal expression of homeobox genes and transthyretin in expansion carriers.

Neurol Genet 2017 Aug 7;3(4):e161. Epub 2017 Jun 7.

Department of Neuroscience (N.A.F., M.C.B., T.F.G., K.F.B., M.D.-H., P.H.B., J.C., K.R.J.-W., L.M.D., A.M.N., M.E.M., L.P., D.W.D., R.R., M.v.B.), Department of Health Sciences Research (X.W., Y.W.A.), Department of Neurology (N.R.G.-R., K.B.B.), Division of Biomedical Statistics and Informatics (M.G.H.), Mayo Clinic, Jacksonville, FL; Department of Neurology (J.W., M.B.), University of Miami, FL; Department of Neurology (K.A.J., J.E.P., D.S.K., R.C.P., B.F.B.), Mayo Clinic, Rochester, MN; and Divisions of Neurology and Neurobiology (R.B.), Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ.

Objective: We performed a genome-wide brain expression study to reveal the underpinnings of diseases linked to a repeat expansion in chromosome 9 open reading frame 72 ().

Methods: The genome-wide expression profile was investigated in brain tissue obtained from expansion carriers (n = 32), patients without this expansion (n = 30), and controls (n = 20). Using quantitative real-time PCR, findings were confirmed in our entire pathologic cohort of expansion carriers (n = 56) as well as nonexpansion carriers (n = 31) and controls (n = 20).

Results: Our findings were most profound in the cerebellum, where we identified 40 differentially expressed genes, when comparing expansion carriers to patients without this expansion, including 22 genes that have a homeobox (e.g., genes) and/or are located within the gene cluster (top hit: homeobox A5 []). In addition to the upregulation of multiple homeobox genes that play a vital role in neuronal development, we noticed an upregulation of transthyretin (), an extracellular protein that is thought to be involved in neuroprotection. Pathway analysis aligned with these findings and revealed enrichment for gene ontology processes involved in (anatomic) development (e.g., organ morphogenesis). Additional analyses uncovered that and levels are associated with variant 2 levels as well as with intron-containing transcript levels, and thus, disease-related changes in those transcripts may have triggered the upregulation of and .

Conclusions: In conclusion, our identification of genes involved in developmental processes and neuroprotection sheds light on potential compensatory mechanisms influencing the occurrence, presentation, and/or progression of -related diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1212/NXG.0000000000000161DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5479438PMC
August 2017

Repetitive element transcripts are elevated in the brain of C9orf72 ALS/FTLD patients.

Hum Mol Genet 2017 09;26(17):3421-3431

Integrative Physiology, Institute for Behavioral Genetics University of Colorado, CO 80309, USA.

Significant transcriptome alterations are detected in the brain of patients with amyotrophic lateral sclerosis (ALS), including carriers of the C9orf72 repeat expansion and C9orf72-negative sporadic cases. Recently, the expression of repetitive element transcripts has been associated with toxicity and, while increased repetitive element expression has been observed in several neurodegenerative diseases, little is known about their contribution to ALS. To assess whether aberrant expression of repetitive element sequences are observed in ALS, we analysed RNA sequencing data from C9orf72-positive and sporadic ALS cases, as well as healthy controls. Transcripts from multiple classes and subclasses of repetitive elements (LINEs, endogenous retroviruses, DNA transposons, simple repeats, etc.) were significantly increased in the frontal cortex of C9orf72 ALS patients. A large collection of patient samples, representing both C9orf72 positive and negative ALS, ALS/FTLD, and FTLD cases, was used to validate the levels of several repetitive element transcripts. These analyses confirmed that repetitive element expression was significantly increased in C9orf72-positive compared to C9orf72-negative or control cases. While previous studies suggest an important link between TDP-43 and repetitive element biology, our data indicate that TDP-43 pathology alone is insufficient to account for the observed changes in repetitive elements in ALS/FTLD. Instead, we found that repetitive element expression positively correlated with RNA polymerase II activity in postmortem brain, and pharmacologic modulation of RNA polymerase II activity altered repetitive element expression in vitro. We conclude that increased RNA polymerase II activity in ALS/FTLD may lead to increased repetitive element transcript expression, a novel pathological feature of ALS/FTLD.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/hmg/ddx233DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5886204PMC
September 2017

In-depth clinico-pathological examination of RNA foci in a large cohort of C9ORF72 expansion carriers.

Acta Neuropathol 2017 08 15;134(2):255-269. Epub 2017 May 15.

Department of Neuroscience, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL, 32224, USA.

A growing body of evidence suggests that a loss of chromosome 9 open reading frame 72 (C9ORF72) expression, formation of dipeptide-repeat proteins, and generation of RNA foci contribute to disease pathogenesis in amyotrophic lateral sclerosis and frontotemporal dementia. Although the levels of C9ORF72 transcripts and dipeptide-repeat proteins have already been examined thoroughly, much remains unknown about the role of RNA foci in C9ORF72-linked diseases. As such, we performed a comprehensive RNA foci study in an extensive pathological cohort of C9ORF72 expansion carriers (n = 63). We evaluated two brain regions using a newly developed computer-automated pipeline allowing recognition of cell nuclei and RNA foci (sense and antisense) supplemented by manual counting. In the frontal cortex, the percentage of cells with sense or antisense RNA foci was 26 or 12%, respectively. In the cerebellum, 23% of granule cells contained sense RNA foci and 1% antisense RNA foci. Interestingly, the highest percentage of cells with RNA foci was observed in cerebellar Purkinje cells (~70%). In general, more cells contained sense RNA foci than antisense RNA foci; however, when antisense RNA foci were present, they were usually more abundant. We also observed that an increase in the percentage of cells with antisense RNA foci was associated with a delayed age at onset in the frontal cortex (r = 0.43, p = 0.003), whereas no other associations with clinico-pathological features were seen. Importantly, our large-scale study is the first to provide conclusive evidence that RNA foci are not the determining factor of the clinico-pathological variability observed in C9ORF72 expansion carriers and it emphasizes that the distribution of RNA foci does not follow the pattern of neurodegeneration, stressing the complex interplay between different aspects of C9ORF72-related diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00401-017-1725-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5508036PMC
August 2017

Poly(GP) proteins are a useful pharmacodynamic marker for -associated amyotrophic lateral sclerosis.

Sci Transl Med 2017 03;9(383)

Department of Neurology, Mayo Clinic, Jacksonville, FL 32224, USA.

There is no effective treatment for amyotrophic lateral sclerosis (ALS), a devastating motor neuron disease. However, discovery of a GC repeat expansion in the gene as the most common genetic cause of ALS has opened up new avenues for therapeutic intervention for this form of ALS. GC repeat expansion RNAs and proteins of repeating dipeptides synthesized from these transcripts are believed to play a key role in -associated ALS (c9ALS). Therapeutics that target GC RNA, such as antisense oligonucleotides (ASOs) and small molecules, are thus being actively investigated. A limitation in moving such treatments from bench to bedside is a lack of pharmacodynamic markers for use in clinical trials. We explored whether poly(GP) proteins translated from GC RNA could serve such a purpose. Poly(GP) proteins were detected in cerebrospinal fluid (CSF) and in peripheral blood mononuclear cells from c9ALS patients and, notably, from asymptomatic mutation carriers. Moreover, CSF poly(GP) proteins remained relatively constant over time, boding well for their use in gauging biochemical responses to potential treatments. Treating c9ALS patient cells or a mouse model of c9ALS with ASOs that target GC RNA resulted in decreased intracellular and extracellular poly(GP) proteins. This decrease paralleled reductions in GC RNA and downstream GC RNA-mediated events. These findings indicate that tracking poly(GP) proteins in CSF could provide a means to assess target engagement of GC RNA-based therapies in symptomatic repeat expansion carriers and presymptomatic individuals who are expected to benefit from early therapeutic intervention.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/scitranslmed.aai7866DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5576451PMC
March 2017

TYROBP genetic variants in early-onset Alzheimer's disease.

Neurobiol Aging 2016 12 8;48:222.e9-222.e15. Epub 2016 Aug 8.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA. Electronic address:

We aimed to identify new candidate genes potentially involved in early-onset Alzheimer's disease (EOAD). Exome sequencing was conducted on 45 EOAD patients with either a family history of Alzheimer's disease (AD, <65 years) or an extremely early age at the onset (≤55 years) followed by multiple variant filtering according to different modes of inheritance. We identified 29 candidate genes potentially involved in EOAD, of which the gene TYROBP, previously implicated in AD, was selected for genetic and functional follow-up. Using 3 patient cohorts, we observed rare coding TYROBP variants in 9 out of 1110 EOAD patients, whereas no such variants were detected in 1826 controls (p = 0.0001), suggesting that at least some rare TYROBP variants might contribute to EOAD risk. Overexpression of the p.D50_L51ins14 TYROBP mutant led to a profound reduction of TREM2 expression, a well-established risk factor for AD. This is the first study supporting a role for genetic variation in TYROBP in EOAD, with in vitro support for a functional effect of the p.D50_L51ins14 TYROBP mutation on TREM2 expression.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neurobiolaging.2016.07.028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5159294PMC
December 2016

Spt4 selectively regulates the expression of C9orf72 sense and antisense mutant transcripts.

Science 2016 Aug;353(6300):708-12

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.

An expanded hexanucleotide repeat in C9orf72 causes amyotrophic lateral sclerosis and frontotemporal dementia (c9FTD/ALS). Therapeutics are being developed to target RNAs containing the expanded repeat sequence (GGGGCC); however, this approach is complicated by the presence of antisense strand transcription of expanded GGCCCC repeats. We found that targeting the transcription elongation factor Spt4 selectively decreased production of both sense and antisense expanded transcripts, as well as their translated dipeptide repeat (DPR) products, and also mitigated degeneration in animal models. Knockdown of SUPT4H1, the human Spt4 ortholog, similarly decreased production of sense and antisense RNA foci, as well as DPR proteins, in patient cells. Therapeutic targeting of a single factor to eliminate c9FTD/ALS pathological features offers advantages over approaches that require targeting sense and antisense repeats separately.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/science.aaf7791DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5823025PMC
August 2016

NEK1 variants confer susceptibility to amyotrophic lateral sclerosis.

Nat Genet 2016 09 25;48(9):1037-42. Epub 2016 Jul 25.

Neurogenetics Group, Division of Brain Sciences, Imperial College London, London, UK.

To identify genetic factors contributing to amyotrophic lateral sclerosis (ALS), we conducted whole-exome analyses of 1,022 index familial ALS (FALS) cases and 7,315 controls. In a new screening strategy, we performed gene-burden analyses trained with established ALS genes and identified a significant association between loss-of-function (LOF) NEK1 variants and FALS risk. Independently, autozygosity mapping for an isolated community in the Netherlands identified a NEK1 p.Arg261His variant as a candidate risk factor. Replication analyses of sporadic ALS (SALS) cases and independent control cohorts confirmed significant disease association for both p.Arg261His (10,589 samples analyzed) and NEK1 LOF variants (3,362 samples analyzed). In total, we observed NEK1 risk variants in nearly 3% of ALS cases. NEK1 has been linked to several cellular functions, including cilia formation, DNA-damage response, microtubule stability, neuronal morphology and axonal polarity. Our results provide new and important insights into ALS etiopathogenesis and genetic etiology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ng.3626DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5560030PMC
September 2016

Prosaposin is a regulator of progranulin levels and oligomerization.

Nat Commun 2016 06 30;7:11992. Epub 2016 Jun 30.

Division of Human Genetics, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio 45229, USA.

Progranulin (GRN) loss-of-function mutations leading to progranulin protein (PGRN) haploinsufficiency are prevalent genetic causes of frontotemporal dementia. Reports also indicated PGRN-mediated neuroprotection in models of Alzheimer's and Parkinson's disease; thus, increasing PGRN levels is a promising therapeutic for multiple disorders. To uncover novel PGRN regulators, we linked whole-genome sequence data from 920 individuals with plasma PGRN levels and identified the prosaposin (PSAP) locus as a new locus significantly associated with plasma PGRN levels. Here we show that both PSAP reduction and overexpression lead to significantly elevated extracellular PGRN levels. Intriguingly, PSAP knockdown increases PGRN monomers, whereas PSAP overexpression increases PGRN oligomers, partly through a protein-protein interaction. PSAP-induced changes in PGRN levels and oligomerization replicate in human-derived fibroblasts obtained from a GRN mutation carrier, further supporting PSAP as a potential PGRN-related therapeutic target. Future studies should focus on addressing the relevance and cellular mechanism by which PGRN oligomeric species provide neuroprotection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ncomms11992DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4931318PMC
June 2016

CCNF mutations in amyotrophic lateral sclerosis and frontotemporal dementia.

Nat Commun 2016 Apr 15;7:11253. Epub 2016 Apr 15.

Montreal Neurological Institute and Hospital, Department of Neurology and Neurosurgery, McGill University, Montreal, Québec, Canada H3A 2B4.

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are overlapping, fatal neurodegenerative disorders in which the molecular and pathogenic basis remains poorly understood. Ubiquitinated protein aggregates, of which TDP-43 is a major component, are a characteristic pathological feature of most ALS and FTD patients. Here we use genome-wide linkage analysis in a large ALS/FTD kindred to identify a novel disease locus on chromosome 16p13.3. Whole-exome sequencing identified a CCNF missense mutation at this locus. Interrogation of international cohorts identified additional novel CCNF variants in familial and sporadic ALS and FTD. Enrichment of rare protein-altering CCNF variants was evident in a large sporadic ALS replication cohort. CCNF encodes cyclin F, a component of an E3 ubiquitin-protein ligase complex (SCF(Cyclin F)). Expression of mutant CCNF in neuronal cells caused abnormal ubiquitination and accumulation of ubiquitinated proteins, including TDP-43 and a SCF(Cyclin F) substrate. This implicates common mechanisms, linked to protein homeostasis, underlying neuronal degeneration.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ncomms11253DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4835537PMC
April 2016

C9orf72 promoter hypermethylation is reduced while hydroxymethylation is acquired during reprogramming of ALS patient cells.

Exp Neurol 2016 Mar 31;277:171-177. Epub 2015 Dec 31.

Center for Therapeutic Innovation, University of Miami Miller School of Medicine, Miami, FL, USA; Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL, USA. Electronic address:

Among several genetic mutations known to cause amyotrophic lateral sclerosis (ALS), a hexanucleotide repeat expansion in the C9orf72 gene is the most common. In approximately 30% of C9orf72-ALS cases, 5-methylcytosine (5mC) levels within the C9orf72 promoter are increased, resulting in a modestly attenuated phenotype. The developmental timing of C9orf72 promoter hypermethylation and the reason why it occurs in only a subset of patients remain unknown. In order to model the acquisition of C9orf72 hypermethylation and examine the potential role of 5-hydroxymethylcytosine (5hmC), we generated induced pluripotent stem cells (iPSCs) from an ALS patient with C9orf72 promoter hypermethylation. Our data show that 5mC levels are reduced by reprogramming and then re-acquired upon neuronal specification, while 5hmC levels increase following reprogramming and are highest in iPSCs and motor neurons. We confirmed the presence of 5hmC within the C9orf72 promoter in post-mortem brain tissues of hypermethylated patients. These findings show that iPSCs are a valuable model system for examining epigenetic perturbations caused by the C9orf72 mutation and reveal a potential role for cytosine demethylation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.expneurol.2015.12.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4761318PMC
March 2016

Neurodegenerative disease: C9orf72 repeats compromise nucleocytoplasmic transport.

Nat Rev Neurol 2015 Dec 3;11(12):670-2. Epub 2015 Nov 3.

Department of Neuroscience, Mayo Clinic Jacksonville, 4500 San Pablo Road, Jacksonville, FL 32224, USA.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nrneurol.2015.219DOI Listing
December 2015

Novel clinical associations with specific C9ORF72 transcripts in patients with repeat expansions in C9ORF72.

Acta Neuropathol 2015 Dec 5;130(6):863-76. Epub 2015 Oct 5.

Department of Neuroscience, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL, 32224, USA.

The loss of chromosome 9 open reading frame 72 (C9ORF72) expression, associated with C9ORF72 repeat expansions, has not been examined systematically. Three C9ORF72 transcript variants have been described thus far; the GGGGCC repeat is located between two non-coding exons (exon 1a and exon 1b) in the promoter region of transcript variant 2 (NM_018325.4) or in the first intron of variant 1 (NM_145005.6) and variant 3 (NM_001256054.2). We studied C9ORF72 expression in expansion carriers (n = 56) for whom cerebellum and/or frontal cortex was available. Using quantitative real-time PCR and digital molecular barcoding techniques, we assessed total C9ORF72 transcripts, variant 1, variant 2, variant 3, and intron containing transcripts [upstream of the expansion (intron 1a) and downstream of the expansion (intron 1b)]; the latter were correlated with levels of poly(GP) and poly(GA) proteins aberrantly translated from the expansion as measured by immunoassay (n = 50). We detected a decrease in expansion carriers as compared to controls for total C9ORF72 transcripts, variant 1, and variant 2: the strongest association was observed for variant 2 (quantitative real-time PCR cerebellum: median 43 %, p = 1.26e-06, and frontal cortex: median 58 %, p = 1.11e-05; digital molecular barcoding cerebellum: median 31 %, p = 5.23e-10, and frontal cortex: median 53 %, p = 5.07e-10). Importantly, we revealed that variant 1 levels greater than the 25th percentile conferred a survival advantage [digital molecular barcoding cerebellum: hazard ratio (HR) 0.31, p = 0.003, and frontal cortex: HR 0.23, p = 0.0001]. When focusing on intron containing transcripts, analysis of the frontal cortex revealed an increase of potentially truncated transcripts in expansion carriers as compared to controls [digital molecular barcoding frontal cortex (intron 1a): median 272 %, p = 0.003], with the highest levels in patients pathologically diagnosed with frontotemporal lobar degeneration. In the cerebellum, our analysis suggested that transcripts were less likely to be truncated and, excitingly, we discovered that intron containing transcripts were associated with poly(GP) levels [digital molecular barcoding cerebellum (intron 1a): r = 0.33, p = 0.02, and (intron 1b): r = 0.49, p = 0.0004] and poly(GA) levels [digital molecular barcoding cerebellum (intron 1a): r = 0.34, p = 0.02, and (intron 1b): r = 0.38, p = 0.007]. In summary, we report decreased expression of specific C9ORF72 transcripts and provide support for the presence of truncated transcripts as well as pre-mRNAs that may serve as templates for RAN translation. We further show that higher C9ORF72 levels may have beneficial effects, which warrants caution in the development of new therapeutic approaches.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00401-015-1480-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4655160PMC
December 2015