SQSTM1 variant in disorders of the frontotemporal dementia-amyotrophic lateral sclerosis spectrum: identification of a novel heterozygous variant and a review of the literature

Primary progressive aphasia and motor neuron disease: A review

Background

This study aims at reviewing, within the framework of motor neuron disease-frontotemporal degeneration (MND-FTD)-spectrum disorders, evidence on the co-occurrence between primary progressive aphasia (PPA) and MND in order to profile such a complex at pathological, genetic and clinical levels.

Methods

This review was pre-registered (osf.io/ds8m4) and performed in accordance with the 2020 PRISMA guidelines. Case reports/series and group studies were included if addressing (1) progressive non-fluent aphasia (PNFA) or semantic dementia (SD) with MND or (2) MND patients with co-morbid PNFA/SD.

Results

Out of 546 initial records, 56 studies were included. As to case reports/series (N = 35), which included 61 PPA-MND patients, the following findings yielded: (1) PNFA is more frequent than SD in PPA-MND; (2) in PPA-MND, the most prevalent motor phenotypes are amyotrophic lateral sclerosis and predominant-upper MND, with bulbar involvement being ubiquitous; (3) extrapyramidal features are moderately frequent in PPA-MND; (4) PPA-MND patients usually display frontotemporal, left-greater-than-right involvement; (5) TDP-43-B is the typical pathological substrate of PPA-MND; (6) TBK1 mutations represent the most frequent genetic risk factors for PPA-MND.

As to group studies, including 121 patients, proportional meta-analytic procedures revealed that: (1) the lifetime prevalence of MND in PPA is 6%; (2) PPA occurs in 19% of patients with co-morbid MND and FTD; (3) MND is more frequent in PNFA (10%) than in SD patients (3%).

Discussion

Insights herewith delivered into the clinical, neuropathological and genetic features of PPA-MND patients prompt further investigations aimed at improving clinical practice within the MND-FTD spectrum.

The NRF2-Dependent Transcriptional Regulation of Antioxidant Defense Pathways: Relevance for Cell Type-Specific Vulnerability to Neurodegeneration and Therapeutic Intervention

Oxidative stress has been implicated in the etiology and pathobiology of various neurodegenerative diseases. At baseline, the cells of the nervous system have the capability to regulate the genes for antioxidant defenses by engaging nuclear factor erythroid 2 (NFE2/NRF)-dependent transcriptional mechanisms, and a number of strategies have been proposed to activate these pathways to promote neuroprotection. Here, we briefly review the biology of the transcription factors of the NFE2/NRF family in the brain and provide evidence for the differential cellular localization of NFE2/NRF family members in the cells of the nervous system. We then discuss these findings in the context of the oxidative stress observed in two neurodegenerative diseases, Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS), and present current strategies for activating NFE2/NRF-dependent transcription. Based on the expression of the NFE2/NRF family members in restricted populations of neurons and glia, we propose that, when designing strategies to engage these pathways for neuroprotection, the relative contributions of neuronal and non-neuronal cell types to the overall oxidative state of tissue should be considered, as well as the cell types which have the greatest intrinsic capacity for producing antioxidant enzymes.

Expanding the clinical and genetic spectrum of SQSTM1-related disorders in family with personality disorder and frontotemporal dementia

Objective: SQSTM1-variants associated with frontotemporal lobar degeneration have been described recently. In this study, we investigated a heterozygous in-frame duplication c.436_462dup p. (Pro146_Cys154dup) in the SQSTM1 gene in a family with a new phenotype characterized by a personality disorder and behavioral variant frontotemporal dementia (bvFTD). We review the literature on frontotemporal dementia (FTD) associated with SQSTM1. Methods: The index case and relatives were described, and a genetic study through Whole Exome Sequencing was performed. The literature was reviewed using Medline and Web of Science. Case reports, case series, and cohort studies were included if they provided information on SQSTM1 mutations associated with FTD. Results: Our patient is a 70-year-old man with a personality disorder since youth, familial history of dementia, and personality disorders with a 10-year history of cognitive decline and behavioral disturbances. A diagnosis of probable bvFTD was established, and the in-frame duplication c.436_462dup in the SQSTM1 gene was identified. Segregation analysis in the family confirmed that both affected sons with personality disorder were heterozygous carriers, but not his healthy 65-year-old brother. A total of 14 publications about 57 patients with SQSTM1-related FTD were reviewed, in which the bvFTD subtype was the main phenotype described (66.6%), with a predominance in men (63%) and positive family history in 61.4% of the cases. Conclusions: We describe a heterozygous in-frame duplication c.436_462dup p.(Pro146_Cys154dup) in the SQSTM1 gene, which affects the zinc-finger domain of p62, in a family with a personality disorder and bvFTD, expanding the genetics and clinical phenotype related to SQSTM1.