Abstract
Background and Objectives Amyotrophic lateral sclerosis (ALS) is characterized by upper and lower motor neuron degeneration, with juvenile ALS (jALS) defined as disease with age at onset (AAO) before 25 years. We aimed to identify the genetic basis of 2 unrelated patients with jALS with very rapid deterioration and early age intellectual disability (ID) and to assess association of genetic findings with both phenotypes in a large cohort of patients with ALS and controls, and in the literature.
Methods Exome sequencing was performed in 2 unrelated probands and their parents. Trio analyses included de novo, rare homozygosity, and compound heterozygosity analyses. A TaqMan genotyping assay was used to genotype ALS cohorts. A systematic literature review was conducted and additional information from authors obtained to assess prevalence of fused in sarcoma (FUS)-ALS associated with ID.
Results A de novo mutation FUS-P525L was identified in both patients. Additional variations were identified in other genes related to intellectual disabilities. Among 8 additional unrelated juvenile patients, one carried the same FUS mutation and had a similar medical history of mild ID and fulminant ALS, whereas the others did not carry any FUS coding mutations and had no reported learning or intellectual disabilities (p = 0.0083). In addition, 486 patients with ALS with AAO ≥25 years were negative for this mutation. An extensive literature review showed that among all patients with FUS-related ALS with full phenotype reports, 10.3% exhibited additional learning/intellectual disabilities.
Discussion FUS-P525L mutation was identified in 3 among 10 patients with jALS (30%) in our clinical cohort, all with a very aggressive disease course and ID. Together with literature reports, these results support a novel association between mutations in FUS and early life ID. Additional variations identified in genes related to ID and brain development in our patients (GPT2, DNAH10, and SCUBE2) may suggest a complex oligogenic inheritance for this phenotype. We propose that this mutation should be screened in patients with ALS with very early AAO, aggressive disease course, and sporadic occurrence, especially when ALS is accompanied by ID.
Glossary
- AAO=
- age at onset;
- ACMG=
- American College of Medical Genetics and Genomics;
- ALS=
- amyotrophic lateral sclerosis;
- ASD=
- autism spectrum disorder;
- CADD=
- Combined Annotation-Dependent Depletion;
- CH=
- compound heterozygosity;
- fALS=
- familial ALS;
- FTD=
- frontotemporal dementia;
- FUS=
- fused in sarcoma;
- gnomAD=
- Genome Aggregation Database;
- jALS=
- juvenile ALS;
- LMN=
- lower motor neuron;
- LoF=
- loss of function;
- NLS=
- nuclear localization signal;
- PY=
- proline-tyrosine;
- sALS=
- sporadic ALS;
- UMN=
- upper motor neuron;
- WES=
- whole-exome sequencing
Footnotes
Go to Neurology.org/NG for full disclosures. Funding information is provided at the end of the article.
The Article Processing Charge was funded by Medical Research Fund, Tel Aviv Sourasky Medical Center.
↵* These authors contributed equally to this work.
Submitted and externally peer reviewed. The handling editor was Raymond P. Roos, MD, FAAN.
- Received March 23, 2022.
- Accepted in final form May 10, 2022.
- Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.
This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND), which permits downloading and sharing the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.
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