Genetics of Amyotrophic Lateral Sclerosis

Peer reviewedPublisher PD

Oncogenic transformation of Drosophila somatic cells induces a functional piRNA pathway.

Germline genes often become re-expressed in soma-derived human cancers as "cancer/testis antigens" (CTAs), and piRNA (PIWI-interacting RNA) pathway proteins are found among CTAs. However, whether and how the piRNA pathway contributes to oncogenesis in human neoplasms remain poorly understood. We found that oncogenic Ras combined with loss of the Hippo tumor suppressor pathway reactivates a primary piRNA pathway in Drosophila somatic cells coincident with oncogenic transformation. In these cells, Piwi becomes loaded with piRNAs derived from annotated generative loci, which are normally restricted to either the germline or the somatic follicle cells. Negating the pathway leads to increases in the expression of a wide variety of transposons and also altered expression of some protein-coding genes. This correlates with a reduction in the proliferation of the transformed cells in culture, suggesting that, at least in this context, the piRNA pathway may play a functional role in cancer.We thank the Cold Spring Harbor Laboratory Microscopy Shared Resources for assistance, which are funded in part by Cancer Center Support Grant 5P30CA045508. This work was supported in part by a grant from the STARR Cancer Consortium, grants from the National Institutes of Health (NIH MERIT Award, R37GM062534 to G. J.H.), and a generous gift from Kathryn W. Davis to G.J.H. N.P. and G.J.H. are or were Investigators of the Howard Hughes Medical Institute. Stocks obtained from the Bloomington Drosophila Stock Center (NIH P40OD018537) were used in this study. Cell lines have been deposited by A.S. at the Drosophila Genomics Resource Center (NIH 2P40OD010949-10A1). G.J.H. is supported by Cancer Research UK and is a Wellcome Trust Investigator.This is the final version of the article. It first appeared from Cold Spring Harbor Press at http://dx.doi.org/10.1101/gad.284927.116

Unexpected similarities between C9ORF72 and sporadic forms of ALS/FTD suggest a common disease mechanism

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) represent two ends of a disease spectrum with shared clinical, genetic and pathological features. These include near ubiquitous pathological inclusions of the RNA-binding protein (RBP) TDP-43, and often the presence of a GGGGCC expansion in the C9ORF72 (C9) gene. Previously, we reported that the sequestration of hnRNP H altered the splicing of target transcripts in C9ALS patients. Here, we show that this signature also occurs in half of 50 postmortem sporadic, non-C9 ALS/FTD brains. Furthermore, and equally surprisingly, these ‘like-C9’ brains also contained correspondingly high amounts of insoluble TDP-43, as well as several other disease-related RBPs, and this correlates with widespread global splicing defects. Finally, we show that the like-C9 sporadic patients, like actual C9ALS patients, were much more likely to have developed FTD. We propose that these unexpected links between C9 and sporadic ALS/FTD define a common mechanism in this disease spectrum

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

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

TDP-43 loss and ALS-risk SNPs drive mis-splicing and depletion of UNC13A

Variants of UNC13A, a critical gene for synapse function, increase the risk of amyotrophic lateral sclerosis and frontotemporal dementia1-3, two related neurodegenerative diseases defined by mislocalization of the RNA-binding protein TDP-434,5. Here we show that TDP-43 depletion induces robust inclusion of a cryptic exon in UNC13A, resulting in nonsense-mediated decay and loss of UNC13A protein. Two common intronic UNC13A polymorphisms strongly associated with amyotrophic lateral sclerosis and frontotemporal dementia risk overlap with TDP-43 binding sites. These polymorphisms potentiate cryptic exon inclusion, both in cultured cells and in brains and spinal cords from patients with these conditions. Our findings, which demonstrate a genetic link between loss of nuclear TDP-43 function and disease, reveal the mechanism by which UNC13A variants exacerbate the effects of decreased TDP-43 function. They further provide a promising therapeutic target for TDP-43 proteinopathies

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STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Compensasomes Do Not Spread from the X Chromosome onto Autosomal Regions Inserted on the X

<div><p>(A) Females expressing MSL-2 from an <i>msl2Δ3–21</i> transgene and bearing a reciprocal translocation between the X and second chromosome (line XIII) do not show additional bands in the regions of the 2L arm juxtaposed to X chromosome material.</p> <p>(B) MSL binding pattern on the X chromosome of a wild-type male.</p> <p>(C and D) The autosomal region 81F–82F10–11 does not show MSL binding when inserted at 3D in the single X of a male (line XV) (C) or in MSL-2-expressing females heterozygous for the same transposition (D). Note that the MSL binding pattern on the X chromosome is not altered by the insertion. The light band (arrow) maintained on the wild-type unpaired region of the X of a female heterozygous for the transposition is also present next to the same insertion at 3D on the unique X chromosome of a male (compare C and D).</p></div

MSL Binding to Pieces of X Chromosome Inserted into Autosomes

<div><p>Salivary glands from males heterozygous for each transposition were fixed (47% acetic acid in phosphate-buffered saline, then lactic acid/water/acetic acid [1:2:3]), squashed on slides, treated with anti-MSL-1 antibodies and a secondary Cy3 anti-rabbit immunoglobulin G antibody, then counterstained with DAPI and viewed using a Zeiss Axiophot microscope. Both duplications and transpositions were able to attract compensasomes, whether or not they contained predicted entry sites.</p> <p>(A) Line II.</p> <p>(B) Line I, which contains the <i>roX1</i> gene.</p> <p>(C) Line X shows one to two bands on the smallest transposition we studied; the intensity of the second band was variable even on the X chromosome.</p> <p>(D) Line IV.</p> <p>(E) Line IX.</p> <p>(F) Line XI.</p> <p>Breakpoints (described in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0020341#pbio-0020341-t001" target="_blank">Table 1</a>) were verified by cytology when possible and/or with specific probes by in situ hybridization. Gray value images were pseudo-colored and merged.</p></div