Angiogenin loss-of-function mutations in amyotrophic lateral sclerosis

Department of Pathology, Brigham and Women's Hospital, Boston, MA 02114, USA.
Annals of Neurology (Impact Factor: 9.98). 12/2007; 62(6):609-17. DOI: 10.1002/ana.21221
Source: PubMed


Heterozygous missense mutations in the coding region of angiogenin (ANG), an angiogenic ribonuclease, have been reported in amyotrophic lateral sclerosis (ALS) patients. However, the role of ANG in motor neuron physiology and the functional consequences of these mutations are unknown. We searched for new mutations and sought to define the functional consequences of these mutations.
We sequenced the coding region of ANG in an independent cohort of North American ALS patients. Identified ANG mutations were then characterized using functional assays of angiogenesis, ribonucleolysis, and nuclear translocation. We also examined expression of ANG in normal human fetal and adult spinal cords.
We identified four mutations in the coding region of ANG from 298 ALS patients. Three of these mutations are present in the mature protein. Among the four mutations, P(-4)S, S28N, and P112L are novel, and K17I has been reported previously. Functional assays show that these ANG mutations result in complete loss of function. The mutant ANG proteins are unable to induce angiogenesis because of a deficiency in ribonuclease activity, nuclear translocation, or both. As a correlate, we demonstrate strong ANG expression in both endothelial cells and motor neurons of normal human spinal cords from the developing fetus and adult.
We provide the first evidence that ANG mutations, identified in ALS patients, are associated with functional loss of ANG activity. Moreover, strong ANG expression, in normal human fetal and adult spinal cord neurons and endothelial cells, confirms the plausibility of ANG dysfunction being relevant to the pathogenesis of ALS.

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    • "On the other hand, low expression levels, mislocalization and/or cellular inclusions have been shown in neurodegenerative cells; all of which may negatively affect the normal amount of certain RBPs in a specific subcellular location. Furthermore, loss-offunction has been demonstrated for ANG mutants involved in neurodegeneration (Wu et al. 2007). "
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    • "So far , no human disease has been associated with mutations in Dnmt2 , but similar to NSun2 , also mutations in angiogenin are linked to neurological disorders ( van Es et al , 2011 ) . Neuro - develop - mental and intellectual disabilities are further commonly associated with oxidative stress ( Wu et al , 2007 ; De Felice et al , 2012 ; Lintas et al , 2012 ) . "
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    • "In addition, several rare mutations have also been discovered in the ANG gene; however, it is not yet known whether these are instrumental in causing ALS 7. The human ANG gene encodes a 14.1 kDa long monomeric ANG protein that induces neovascularization, maintains the physiology and health of motor neurons by inducing angiogenesis, stimulates neurite outgrowth and path-finding and protects motor neurons from hypoxia-induced death and hence acts as a neuroprotective factor 8– 12. ANG binds to its target cells and undergoes nuclear translocation due to the presence of two functional sites such as the receptor-binding site ( 60NKNGNPHREN 68) and the nuclear localization signal ( 29IMRRRGL 35) respectively. Another important function of ANG is the ribonucleolytic activity governed by the catalytic triad residues His13, Lys40 and His114 8, 9. Several reports on laboratory-based functional assay experiments 9– 12 and molecular dynamics (MD) simulations 6, 7, 13 have shown that loss of either ribonucleolytic activity or nuclear translocation activity or both of these functions due to missense mutations in ANG cause ALS. "
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    ABSTRACT: ANGDelMut is a web-based tool for predicting the functional consequences of missense mutations in the angiogenin (ANG) protein, which is associated with amyotrophic lateral sclerosis (ALS). Missense mutations in ANG result in loss of either ribonucleolytic activity or nuclear translocation activity or both of these functions, and in turn cause ALS. However, no web-based tools are available to predict whether a newly identified ANG mutation will possibly lead to ALS. More importantly, no web-implemented method is currently available to predict the mechanisms of loss-of-function(s) of ANG mutants. In light of this observation, we developed the ANGDelMut web-based tool, which predicts whether an ANG mutation is deleterious or benign. The user selects certain attributes from the input panel, which serves as a query to infer whether a mutant will exhibit loss of ribonucleolytic activity or nuclear translocation activity or whether the overall stability will be affected. The output states whether the mutation is deleterious or benign, and if it is deleterious, gives the possible mechanism(s) of loss-of-function. This web-based tool, freely available at, is the first of its kind to provide a platform for researchers and clinicians, to infer the functional consequences of ANG mutations and correlate their possible association with ALS ahead of experimental findings.
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