New advances in Amyotrophic Lateral Sclerosis genetics: Towards gene therapy opportunities for familial and young cases

MAPT mutations in amyotrophic lateral sclerosis: clinical, neuropathological and functional insights

BACKGROUND

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are part of a well-established disease continuum, underpinned by TDP43-pathology. In contrast, the clinical manifestations of Tau-linked disorders are typically limited to cognitive phenotypes or atypical parkinsonism, although few reports describe motor neuron involvement associated with MAPT (microtubule-associated protein Tau) mutations. This study aimed to investigate the contribution of MAPT to the ALS phenotype.

METHODS

We analyzed a whole-exome sequencing database comprising 470 ALS patients and explored the pathogenicity of the identified variants through familial, clinical, neuropathological, and cellular studies.

RESULTS

We identified two missense variants in the Tau repeat domains: the novel p.I308T variant, in a patient with early-onset ALS, and the p.P364S mutation in three families with spinal- or respiratory-onset ALS. Segregation of this mutation with disease could be confirmed in two affected cousins. The observation of p.P364S patient's tissue showed accumulations of hyperphosphorylated Tau in various brain regions, prominent in the motor cortex with Lewy body-like inclusions, along with a C-terminal cleaved form of Tau in muscle. In NSC-34 motor neuron cells expressing p.I308T or p.P364S mutants, Tau was discontinuous along the neurites, with clusters of mitochondria resulting from impaired mitochondrial motility.

CONCLUSION

These findings expand the molecular understanding of ALS to include MAPT mutations. MAPT analysis should be incorporated into ALS genetic screening, particularly in patients with a familial history of the disease. Recognizing the full spectrum of MAPT-linked neurodegenerative diseases is of considerable interest, given the ongoing efforts to develop MAPT-targeted therapies.

Evidence-based consensus guidelines for ALS genetic testing and counseling

OBJECTIVE

Advances in amyotrophic lateral sclerosis (ALS) gene discovery, ongoing gene therapy trials, and patient demand have driven increased use of ALS genetic testing. Despite this progress, the offer of genetic testing to persons with ALS is not yet "standard of care." Our primary goal is to develop clinical ALS genetic counseling and testing guidelines to improve and standardize genetic counseling and testing practice among neurologists, genetic counselors or any provider caring for persons with ALS.

METHODS

Core clinical questions were identified and a rapid review performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA-P) 2015 method. Guideline recommendations were drafted and the strength of evidence for each recommendation was assessed by combining two systems: the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) System and the Evaluation of Genomic Applications in Practice and Prevention (EGAPP). A modified Delphi approach was used to reach consensus among a group of content experts for each guideline statement.

RESULTS

A total of 35 guideline statements were developed. In summary, all persons with ALS should be offered single-step genetic testing, consisting of a C9orf72 assay, along with sequencing of SOD1, FUS, and TARDBP, at a minimum. The key education and genetic risk assessments that should be provided before and after testing are delineated. Specific guidance regarding testing methods and reporting for C9orf72 and other genes is provided for commercial laboratories.

INTERPRETATION

These evidence-based, consensus guidelines will support all stakeholders in the ALS community in navigating benefits and challenges of genetic testing.

Fertility Does Not Alter Disease Progression in ALS Patients of Childbearing Age: A Three Centers Retrospective Analysis in Southern China

Background

Limited data exists on the clinical features of patients with amyotrophic lateral sclerosis (ALS) during reproductive ages.

Objective

Our study characterized the clinical features of ALS and the effects of pregnancy on disease progression in patients with ALS.

Methods

We performed a retrospective study of female patients with ALS in three ALS research centers in southern China from 2009 to 2021. Data regarding fertility status, and clinical and genetic features, were collected. Age-matched male patients with ALS served as controls. The patients were divided into the following two subgroups: patients with symptom onset within 1 year of pregnancy and patients with symptom onset over 1 year group after pregnancy.

Results

A total of 52 female and 52 matched male patients were enrolled. There were no differences in female and male patients in the mean age of symptom onset, the mean baseline ALSFRS-R score, or median reduction of ALSFRS-R score (p > 0.05). The mean age of first pregnancy was 25.57 ± 4.40) years. The mean age of first pregnancy in the over 1 year group was lower than that in the within 1 year group (p= 0.01). There was no difference in the median reduction of ALSFRS-R between the two subgroups. In the univariate analysis, diagnostic delay was highly correlated with the disease progression, with short delay representing rapid progress. No multicollinearity was found among every variable. In addition, 40.38% patients carried ALS-related gene variants. The proportion with gene mutations in the within 1 year group was higher than that in the over 1 year group (p < 0.01). Furthermore, SETX was the most frequently mutated gene in this cohort (16.67%) including 4 uncertain mutation.

Conclusion

Pregnancy and fertility were not associated with disease progression. Diagnostic delay was correlated with disease progression in this cohort. In addition, SETX might be a gene of concern for ALS patients of childbearing age.