Stress-induced phosphorylation of eIF2α inhibits global protein synthesis to conserve energy for repair of stress-induced damage. Stress-induced translational arrest is observed in cells expressing a nonphosphorylatable eIF2α mutant (S51A), which indicates the existence of an alternative pathway of translational control. In this paper, we show that arsenite, heat shock, or ultraviolet irradiation promotes transfer RNA (tRNA) cleavage and accumulation of tRNA-derived, stress-induced small RNAs (tiRNAs). We show that angiogenin, a secreted ribonuclease, is required for stress-induced production of tiRNAs. Knockdown of angiogenin, but not related ribonucleases, inhibits arsenite-induced tiRNA production and translational arrest. In contrast, knockdown of the angiogenin inhibitor RNH1 enhances tiRNA production and promotes arsenite-induced translational arrest. Moreover, recombinant angiogenin, but not RNase 4 or RNase A, induces tiRNA production and inhibits protein synthesis in the absence of exogenous stress. Finally, transfection of angiogenin-induced tiRNAs promotes phospho-eIF2α–independent translational arrest. Our results introduce angiogenin and tiRNAs as components of a phospho-eIF2α–independent stress response program.

/pdf/angiogenin-cleaves-trna-and-promotes-stress-induced-7iques48lq.pdf

Angiogenin cleaves tRNA and promotes stress-induced translational repression.

Amyotrophic lateral sclerosis (ALS) is a motor neuron disease that has sporadic and inherited forms. ALS is the most common neurodegenerative disorder of young and middle-aged adults, and few treatments are available. Although the degeneration predominantly affects the motor system, cognitive and behavioural symptoms have been described for over a century, and there is evidence that ALS and frontotemporal dementia overlap clinically, radiologically, pathologically, and genetically. Cognitive decline in ALS is characterised by personality change, irritability, obsessions, poor insight, and pervasive deficits in frontal executive tests. This presentation is consistent with the changes to character, social conduct, and executive function in frontotemporal dementia. We highlight genetic, imaging, and neuropathological evidence that non-motor systems are affected in ALS and explain the importance of recent discoveries. We review studies of cognitive impairment in ALS and common neuropsychological test results. We also provide advice about clinical assessment of frontotemporal dysfunction in patients with ALS, and suggest future research. Understanding of cognitive impairment in ALS will improve care for patients and their families and provide valuable insights into the pathogenesis of neurodegeneration.

https://www.thelancet.com/pdfs/journals/laneur/PIIS1474-4422(07)70265-X.pdf

Cognitive impairment in amyotrophic lateral sclerosis

Mutations in the cytosine-5 RNA methyltransferase NSun2 cause microcephaly and other neurological abnormalities in mice and human. How post-transcriptional methylation contributes to the human disease is currently unknown. By comparing gene expression data with global cytosine-5 RNA methylomes in patient fibroblasts and NSun2-deficient mice, we find that loss of cytosine-5 RNA methylation increases the angiogenin-mediated endonucleolytic cleavage of transfer RNAs (tRNA) leading to an accumulation of 5′ tRNA-derived small RNA fragments. Accumulation of 5′ tRNA fragments in the absence of NSun2 reduces protein translation rates and activates stress pathways leading to reduced cell size and increased apoptosis of cortical, hippocampal and striatal neurons. Mechanistically, we demonstrate that angiogenin binds with higher affinity to tRNAs lacking site-specific NSun2-mediated methylation and that the presence of 5′ tRNA fragments is sufficient and required to trigger cellular stress responses. Furthermore, the enhanced sensitivity of NSun2-deficient brains to oxidative stress can be rescued through inhibition of angiogenin during embryogenesis. In conclusion, failure in NSun2-mediated tRNA methylation contributes to human diseases via stress-induced RNA cleavage.

https://www.embopress.org/doi/epdf/10.15252/embj.201489282

Aberrant methylation of tRNAs links cellular stress to neuro‐developmental disorders

Angiogenin-induced tRNA-derived Stress-induced RNAs Promote Stress-induced Stress Granule Assembly

The scientific landscape surrounding amyotrophic lateral sclerosis (ALS) continues to shift as the number of genes associated with the disease risk and pathogenesis, and the cellular processes involved, continues to grow. Despite decades of intense research and over 50 potentially causative or disease-modifying genes identified, etiology remains unexplained and treatment options remain limited for the majority of ALS patients. Various factors have contributed to the slow progress in understanding and developing therapeutics for this disease. Here, we review the genetic basis of ALS, highlighting factors that have contributed to the elusiveness of genetic heritability. The most commonly mutated ALS-linked genes are reviewed with an emphasis on disease-causing mechanisms. The cellular processes involved in ALS pathogenesis are discussed, with evidence implicating their involvement in ALS summarized. Past and present therapeutic strategies and the benefits and limitations of the model systems available to ALS researchers are discussed with future directions for research that may lead to effective treatment strategies outlined.

/pdf/als-genetics-mechanisms-and-therapeutics-where-are-we-now-g2xe5fjrbn.pdf

ALS Genetics, Mechanisms, and Therapeutics: Where Are We Now?

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that typically presents in the fifth to sixth decades of life with upper and lower motor neuron signs. Initially, there are symptoms that include distal muscle weakness and wasting, increased muscle tone with hyperreflexia, and at times diaphragmatic and/or bulbar weakness. Atypical forms can include symptoms of dementia, parkinsonism, or both. All forms of ALS inexorably progress to generalized amyotrophy, culminating in respiratory failure and death after an average duration of 3 to 5 years.1

The incidence of ALS is estimated at 0.4 to 1.8 per 100,000 people.2,3 Approximately 80 to 90% of ALS cases occur in individuals with no known family history, whereas the remaining cases are attributable to familial inheritance in either an autosomal dominant or recessive manner.3,4 Mutations in the Cu/Zn superoxide dismutase gene 1 (ALS1; SOD1; OMIM 147450), have been identified in 12 to 23% of familial5–7 and in 0 to 7% of sporadic8–10 ALS patients. Currently, SOD1 is the only known autosomal dominant gene in which mutations have been functionally associated with ALS, although three other loci have been identified for typical autosomal dominant ALS by linkage (ALS3, 18q21, OMIM 606640; ALS6, 16q12, OMIM 608030; and ALS7, 20ptel-p13, OMIM 608031).2,3 Other dominantly inherited genetic loci, associated with an atypical ALS phenotype, have also been identified (ALS with dementia/parkinsonism, MAPT, OMIM 157140; progressive lower motor neuron disease, DCTN1, OMIM 601143; and ALS8, VAPB, OMIM 608627). In autosomal dominant ALS with frontotemporal dementia (OMIM 105550), genetic linkage has been reported to 9q21-q22.11 Mutations in the SETX gene (OMIM 608465) have been identified in juvenile-onset autosomal dominant ALS. Lastly, genetic loci identified for juvenile-onset autosomal recessive disease include ALS2 (ALS2, 2q33, OMIM 606352) and linkage for ALS5 to 15q15.1-q21.2,3

Recent linkage analysis in Irish and Scottish ALS populations identified chromosome 14q11.2 as a candidate region and then angiogenin (ANG), a 14.1kDa angiogenic ribonuclease (RNase), as an ALS candidate gene.12,13 Seven heterozygous missense mutations in ANG were identified by sequence screening of 1,629 patients with ALS.13 Analysis of the ANG crystal structure suggested that these mutations may disrupt the structure and result in functional loss. However, the functional consequences of these mutations are unknown.13 We now report herein the identification of four mutations in the coding region of the ANG gene on screening an independent cohort of 298 SOD1-negative ALS patients. Three of these mutations occur in the mature protein and one in the signal peptide sequence. Using angiogenesis, ribonucleolysis, and nuclear translocation assays, we demonstrate that these mutations result in complete loss of function. Moreover, we show ANG expression in both endothelial cells and motor neurons of normal human fetal and adult spinal cord. Our data suggest that ANG plays a role in motor neuron health and provide evidence that ANG mutations, identified in ALS patients, are associated with functional loss of angiogenic activity.

/pdf/angiogenin-loss-of-function-mutations-in-amyotrophic-lateral-5eksz9krle.pdf

Angiogenin Loss-of-Function Mutations in Amyotrophic Lateral Sclerosis

Morphologic determination of the malignant potential of adrenal pheochromocytoma is a challenging problem in surgical pathology. A multiparameter Pheochromocytoma of the Adrenal Gland Scaled Score (PASS) was recently developed based on a comprehensive study of a single institutional cohort of 100 cases. Assignment of a PASS was proposed to be useful for identifying pheochromocytomas with potential to metastasize, which defines malignancy according to the current World Health Organization terminology. A PASS is derived by evaluating multiple morphologic parameters to obtain a scaled score based on the summed weighted importance of each. Despite the proposal of this system several years ago, few studies have since examined its robustness and, in particular, the potential for observer variation inherent in the interpretation and assessment of these morphologic criteria. We further examined the utility of PASS by reviewing an independent single institutional cohort of adrenal pheochromocytomas as evaluated by 5 multi-institutional pathologists with at least 10 years experience in endocrine pathology. We found significant interobserver and intraobserver variation in assignment of PASS with variable interpretation of the underlying components. We consequently suggest that PASS requires further refinement and validation. We cannot currently recommend its use for clinical prognostication.

Observer variation in the application of the Pheochromocytoma of the Adrenal Gland Scaled Score.

Background: Missense heterozygous mutations in the coding region of angiogenin (ANG) gene, encoding a 14 kDa angiogenic RNase, were recently found in patients of amyotropic lateral sclerosis (ALS). Functional analyses have shown that these are loss-of-function mutations, implying that angiogenin deficiency is associated with ALS pathogenesis and that increasing ANG expression or angiogenin activity could be a novel approach for ALS therapy. Objective: Review the evidence showing the involvement of angiogenin in motor neuron physiology and function, and provide a rationale for targeting angiogenin in ALS therapy. Methods: Review the current understanding of the mechanism of angiogenin action in connection with ALS genetics, pathogenesis and therapy. Conclusion: ANG is the first gene whose loss-of-function mutations are associated with ALS pathogenesis. Therapeutic modulation of angiogenin level and activity in the spinal cord, either by systemic delivery of angiogenin protein or through retrograde transpor...

Targeting angiogenin in therapy of amyotropic lateral sclerosis

Dysregulated JAK2 signaling has been shown to play a significant role in the pathogenesis of myeloproliferative disorders. Recently, our work comparing gene expression signatures of primary mediastinal large B-cell lymphomas (PMLBCL) versus nodal diffuse large B-cell lymphomas (DLBCL) revealed a relative increase in JAK2 transcripts in the former suggesting a role for increased JAK2 signaling in a subset of these tumors. Given the likelihood of increased JAK2 signaling in PMLBCL, we sought to determine whether JAK2 activating mutations were an alternative mechanism for increased JAK2 signaling in untreated PMLBCLs. We performed amplification refractory mutation analysis for the JAK2 (V617F) mutation and bi-directional sequencing for the recently described JAK2 exon 12 mutations on genomic DNA isolated from a well characterized cohort of PMLBCLs. No evidence of the mutant JAK2 (V617F) allele or JAK2 exon 12 mutations was detected in 31 PMLBCL cases tested. Analysis using cell lines derived from PMLBCLs (n=1) and from the molecularly similar classical Hodgkin lymphoma (n=4) also failed to reveal involvement of this mutant JAK2 allele. Taken together, these results suggest that JAK2 signaling in PMLBCLs occurs by mechanisms distinct from JAK2 (V617F) or JAK2 exon 12 activating mutations.

No Evidence for the JAK2 (V617F) or JAK2 Exon 12 Mutations in Primary Mediastinal Large B-Cell Lymphoma

Concerns about the large-scale European crisis of bovine spongiform encephalopathy, the finding of 1 infected cow in Alberta, Canada, in 2003, and the theoretical concern of prion transmissibility in blood have renewed interest in the development of rapid, minimally invasive diagnostic assays for prion diseases. Herein we review the pathologic features, clinical manifestations, diagnostic criteria, and recent developments that may lead to new diagnostic screening assays for prion diseases.

David Wu

Papers

Angiogenin Loss-of-Function Mutations in Amyotrophic Lateral Sclerosis

Observer variation in the application of the Pheochromocytoma of the Adrenal Gland Scaled Score.

Targeting angiogenin in therapy of amyotropic lateral sclerosis

No Evidence for the JAK2 (V617F) or JAK2 Exon 12 Mutations in Primary Mediastinal Large B-Cell Lymphoma

Prion diseases: recent developments toward diagnostic tests.