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Exome sequencing in amyotrophic lateral sclerosis implicates a novel gene, DNAJC7, encoding a heat-shock protein.

ABSTRACT: To discover novel genes underlying amyotrophic lateral sclerosis (ALS), we aggregated exomes from 3,864 cases and 7,839 ancestry-matched controls. We observed a significant excess of rare protein-truncating variants among ALS cases, and these variants were concentrated in constrained genes. Through gene level analyses, we replicated known ALS genes including SOD1, NEK1 and FUS. We also observed multiple distinct protein-truncating variants in a highly constrained gene, DNAJC7. The signal in DNAJC7 exceeded genome-wide significance, and immunoblotting assays showed depletion of DNAJC7 protein in fibroblasts in a patient with ALS carrying the p.Arg156Ter variant. DNAJC7 encodes a member of the heat-shock protein family, HSP40, which, along with HSP70 proteins, facilitates protein homeostasis, including folding of newly synthesized polypeptides and clearance of degraded proteins. When these processes are not regulated, misfolding and accumulation of aberrant proteins can occur and lead to protein aggregation, which is a pathological hallmark of neurodegeneration. Our results highlight DNAJC7 as a novel gene for ALS.

SUBMITTER: Farhan SMK

PROVIDER: S-EPMC6919277 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Exome sequencing in amyotrophic lateral sclerosis implicates a novel gene, DNAJC7, encoding a heat-shock protein.

Farhan Sali M K SMK Howrigan Daniel P DP Abbott Liam E LE Klim Joseph R JR Topp Simon D SD Byrnes Andrea E AE Churchhouse Claire C Phatnani Hemali H Smith Bradley N BN Rampersaud Evadnie E Wu Gang G Wuu Joanne J Shatunov Aleksey A Iacoangeli Alfredo A Al Khleifat Ahmad A Mordes Daniel A DA Ghosh Sulagna S Eggan Kevin K Rademakers Rosa R McCauley Jacob L JL Schüle Rebecca R Züchner Stephan S Benatar Michael M Taylor J Paul JP Nalls Michael M Gotkine Marc M Shaw Pamela J PJ Morrison Karen E KE Al-Chalabi Ammar A Traynor Bryan B Shaw Christopher E CE Goldstein David B DB Harms Matthew B MB Daly Mark J MJ Neale Benjamin M BM

Nature neuroscience 20191125 12

To discover novel genes underlying amyotrophic lateral sclerosis (ALS), we aggregated exomes from 3,864 cases and 7,839 ancestry-matched controls. We observed a significant excess of rare protein-truncating variants among ALS cases, and these variants were concentrated in constrained genes. Through gene level analyses, we replicated known ALS genes including SOD1, NEK1 and FUS. We also observed multiple distinct protein-truncating variants in a highly constrained gene, DNAJC7. The signal in DNAJ ...[more]

PMID: 31768050

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Project description:Amyotrophic lateral sclerosis (ALS) is a progressive neurological disease characterised by the degeneration of motor neurons, which are responsible for voluntary movement. There remains limited understanding of disease aetiology, with median survival of ALS of three years and no effective treatment. Identifying genes that contribute to ALS susceptibility is an important step towards understanding aetiology. The vast majority of published human genetic studies, including for ALS, have used samples of European ancestry. The importance of trans-ethnic studies in human genetic studies is widely recognised, yet a dearth of studies of non-European ancestries remains. Here, we report analyses of novel whole-exome sequencing (WES) data from Chinese ALS and control individuals.WES data were generated for 610 ALS cases and 460 controls drawn from Chinese populations. We assessed evidence for an excess of rare damaging mutations at the gene level and the gene set level, considering only singleton variants filtered to have allele frequency less than 5?×?10-5 in reference databases. To meta-analyse our results with a published study of European ancestry, we used a Cochran-Mantel-Haenszel test to compare gene-level variant counts in cases vs controls.No gene passed the genome-wide significance threshold with ALS in Chinese samples alone. Combining rare variant counts in Chinese with those from the largest WES study of European ancestry resulted in three genes surpassing genome-wide significance: TBK1 (p?=?8.3?×?10-12), SOD1 (p?=?8.9?×?10-9) and NEK1 (p?=?1.1?×?10-9). In the Chinese data alone, SOD1 and NEK1 were nominally significantly associated with ALS (p?=?0.04 and p?=?7?×?10-3, respectively) and the case/control frequencies of rare coding variants in these genes were similar in Chinese and Europeans (SOD1: 1.5%/0.2% vs 0.9%/0.1%, NEK1 1.8%/0.4% vs 1.9%/0.8%). This was also true for TBK1 (1.2%/0.2% vs 1.4%/0.4%), but the association with ALS in Chinese was not significant (p?=?0.14).While SOD1 is already recognised as an ALS-associated gene in Chinese, we provide novel evidence for association of NEK1 with ALS in Chinese, reporting variants in these genes not previously found in Europeans.

Project description:Detergent-resistant, ubiquitinated and hyperphosphorylated Tar DNA binding protein 43 (TDP-43, encoded by TARDBP) neuronal cytoplasmic inclusions are the pathological hallmark in ∼95% of amyotrophic lateral sclerosis and ∼60% of frontotemporal lobar degeneration cases. We sought to explore the role for the heat shock response in the clearance of insoluble TDP-43 in a cellular model of disease and to validate our findings in transgenic mice and human amyotrophic lateral sclerosis tissues. The heat shock response is a stress-responsive protective mechanism regulated by the transcription factor heat shock factor 1 (HSF1), which increases the expression of chaperones that refold damaged misfolded proteins or facilitate their degradation. Here we show that manipulation of the heat shock response by expression of dominant active HSF1 results in a dramatic reduction of insoluble and hyperphosphorylated TDP-43 that enhances cell survival, whereas expression of dominant negative HSF1 leads to enhanced TDP-43 aggregation and hyperphosphorylation. To determine which chaperones were mediating TDP-43 clearance we over-expressed a range of heat shock proteins (HSPs) and identified DNAJB2a (encoded by DNAJB2, and also known as HSJ1a) as a potent anti-aggregation chaperone for TDP-43. DNAJB2a has a J domain, allowing it to interact with HSP70, and ubiquitin interacting motifs, which enable it to engage the degradation of its client proteins. Using functionally deleted DNAJB2a constructs we demonstrated that TDP-43 clearance was J domain-dependent and was not affected by ubiquitin interacting motif deletion or proteasome inhibition. This indicates that TDP-43 is maintained in a soluble state by DNAJB2a, leaving the total levels of TDP-43 unchanged. Additionally, we have demonstrated that the levels of HSF1 and heat shock proteins are significantly reduced in affected neuronal tissues from a TDP-43 transgenic mouse model of amyotrophic lateral sclerosis and patients with sporadic amyotrophic lateral sclerosis. This implies that the HSF1-mediated DNAJB2a/HSP70 heat shock response pathway is compromised in amyotrophic lateral sclerosis. Defective refolding of TDP-43 is predicted to aggravate the TDP-43 proteinopathy. The finding that the pathological accumulation of insoluble TDP-43 can be reduced by the activation of HSF1/HSP pathways presents an exciting opportunity for the development of novel therapeutics.

Dataset Information

Exome sequencing in amyotrophic lateral sclerosis implicates a novel gene, DNAJC7, encoding a heat-shock protein.

Publications

Exome sequencing in amyotrophic lateral sclerosis implicates a novel gene, DNAJC7, encoding a heat-shock protein.

Similar Datasets

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