SOD1 D91A variant in the southernmost tip of Europe: a heterozygous ALS patient resident on the island of Gozo

Updates on Disease Mechanisms and Therapeutics for Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS), or Lou Gehrig's disease, is a motor neuron disease. In ALS, upper and lower motor neurons in the brain and spinal cord progressively degenerate during the course of the disease, leading to the loss of the voluntary movement of the arms and legs. Since its first description in 1869 by a French neurologist Jean-Martin Charcot, the scientific discoveries on ALS have increased our understanding of ALS genetics, pathology and mechanisms and provided novel therapeutic strategies. The goal of this review article is to provide a comprehensive summary of the recent findings on ALS mechanisms and related therapeutic strategies to the scientific audience. Several highlighted ALS research topics discussed in this article include the 2023 FDA approved drug for SOD1 ALS, the updated C9orf72 GGGGCC repeat-expansion-related mechanisms and therapeutic targets, TDP-43-mediated cryptic splicing and disease markers and diagnostic and therapeutic options offered by these recent discoveries.

A survey of current practice in genetic testing in amyotrophic lateral sclerosis in the UK and Republic of Ireland: implications for future planning

Objective: To determine the current practice in genetic testing for patients with apparently sporadic motor neurone disease/amyotrophic lateral sclerosis (MND/ALS) and asymptomatic at-risk relatives of familial MND/ALS patients seen in specialized care centers in the UK. Methods: An online survey with 10 questions distributed to specialist healthcare professionals with a role in requesting genetic testing working at MND/ALS care centers. Results: Considerable variation in practice was found. Almost 30% of respondents reported some discomfort in discussing genetic testing with MND/ALS patients and a majority (77%) did not think that all patients with apparently sporadic disease should be routinely offered genetic testing at present. Particular concerns were identified in relation to testing asymptomatic at-risk individuals and the majority view was that clinical genetics services should have a role in supporting genetic testing in MND/ALS, especially in asymptomatic individuals at-risk of carrying pathogenic variants. Conclusions: Variation in practice in genetic testing among MND/ALS clinics may be driven by differences in experience and perceived competence, compounded by the increasing complexity of the genetic underpinnings of MND/ALS. Clear and accessible guidelines for referral pathways between MND/ALS clinics and clinical genetics may be the best way to standardize and improve current practice, ensuring that patients and relatives receive optimal and geographically equitable support.

Genetic landscape of ALS in Malta based on a quinquennial analysis

Genetic risk for amyotrophic lateral sclerosis (ALS) is highly elevated in genetic isolates, like the island population of Malta in the south of Europe, providing a unique opportunity to investigate the genetics of this disease. Here we characterize the clinical phenotype and genetic profile of the largest series of Maltese ALS patients to date identified throughout a 5-year window. Cases and controls underwent neuromuscular assessment and analysis of rare variants in ALS causative or risk genes following whole-genome sequencing. Potentially damaging variants or repeat expansions were identified in more than 45% of all patients. The most commonly affected genes were ALS2, DAO, SETX and SPG11, an infrequent cause of ALS in Europeans. We also confirmed a significant association between ATXN1 intermediate repeats and increased disease risk. Damaging variants in major ALS genes C9orf72, SOD1, TARDBP and FUS were however either absent or rare in Maltese ALS patients. Overall, our study underscores a population that is an outlier within Europe and one that represents a high percentage of genetically explained cases.

Whole Genome Sequencing Unravels New Genetic Determinants of Early-Onset Familial Osteoporosis and Low BMD in Malta

Background: Osteoporosis is a skeletal disease with a strong genetic background. The study aimed to identify the genetic determinants of early-onset familial osteoporosis and low bone mineral density (BMD) in a two-generation Maltese family. Methods: Fifteen relatives aged between 28–74 years were recruited. Whole genome sequencing was conducted on 12 relatives and shortlisted variants were genotyped in the Malta Osteoporotic Fracture Study (MOFS) for replication. Results: Sequential variant filtering following a dominant inheritance pattern identified rare missense variants within SELP, TGF-β2 and ADAMTS20, all of which were predicted to be likely pathogenic and participate in osteoimmunology. TGF-β2 c.1136C>T was identified in five individuals from the MOFS in heterozygosity, four of whom had osteopenia/osteoporosis at the lumbar spine and hip, and/or had sustained a low-trauma fracture. Heterozygosity for the ADAMTS20 c.4090A>T was accompanied by lower total hip BMD (p = 0.018) and lower total serum calcium levels in MOFS (p < 0.01), recapitulating the findings from the family. Women carrying at least one copy of the alternative allele (TC/CC) for SELP c.2177T>C exhibited a tendency for lower lumbar spine BMD and/or wrist fracture history relative to women with TT genotype. Conclusions: Our findings suggest that the identified variants, alone or in combination, could be causal factors of familial osteoporosis and low BMD, requiring replication in larger collections.

Individual Oligogenic Background in p.D91A-SOD1 Amyotrophic Lateral Sclerosis Patients

The p.D91A is one of the most common ALS-causing SOD1 mutations and is known to be either recessive or dominant. The homozygous phenotype is characterized by prolonged survival and slow progression of disease, whereas the affected heterozygous phenotypes can vary. To date, no genetic protective factors located close to SOD1 have been associated with the mild progressive homozygous phenotype. Using Next Generation Sequencing (NGS), we characterized a small cohort of sporadic and familial p.D91A-SOD1 heterozygous (n = 2) or homozygous (n = 5) ALS patients, to reveal any additional contributing variant in 39 ALS-related genes. We detected unique sets of non-synonymous variants, four of which were of uncertain significance and several in untranslated regions of ALS-related genes. Our results supported an individual oligogenic background underlying both sporadic and familial p.D91A cases irrespective of their p.D91A mutant alleles. We suggest that a comprehensive genomic view of p.D91A-SOD1 ALS patients may be useful in identifying emerging variants and improving disease diagnosis as well as guiding precision medicine.