A Novel Splice-Acceptor Site Mutation in GRN (c.709-2 A>T) Causes Frontotemporal Dementia Spectrum in a Large Family from Southern Italy

Narcissistic Personality Disorder as Prodromal Feature of Early-Onset, GRN-Positive bvFTD: A Case Report

Background

Behavioral variant frontotemporal dementia (bvFTD) typically involves subtle changes in personality that can delay a timely diagnosis.

Objective

Here, we report the case of a patient diagnosed of GRN-positive bvFTD at the age of 52 presenting with a 7-year history of narcissistic personality disorder, accordingly to DSM-5 criteria.

Methods

The patient was referred to neurological and neuropsychological examination. She underwent 3 Tesla magnetic resonance imaging (MRI) and genetic studies.

Results

The neuropsychological examination revealed profound deficits in all cognitive domains and 3T brain MRI showed marked fronto-temporal atrophy. A mutation in the GRN gene further confirmed the diagnosis.

Conclusions

The present case documents an unusual onset of bvFTD and highlights the problematic nature of the differential diagnosis between prodromal psychiatric features of the disease and primary psychiatric disorders. Early recognition and diagnosis of bvFTD can lead to appropriate management and support for patients and their families. This case highlights the importance of considering neurodegenerative diseases, such as bvFTD, in the differential diagnosis of psychiatric disorders, especially when exacerbations of behavioral traits manifest in adults.

A case of familial frontotemporal dementia caused by a progranulin gene mutation

After Alzheimer's disease, Frontotemporal dementia (FTD) is the most common cause of early-onset dementia. Several genetic mutations have been identified in familial FTD, with mutations in progranulin (GRN) accounting for approximately 20-25% of familial FTD cases and about 10% of total FTD cases. We report the case of a familial FTD patient with atypical parkinsonism who was found to have GRN frontotemporal dementia (GRN-FTD) with a pathogenic splice site mutation (c.709-2A > G) and notable phenotypic heterogeneity among family members.

Genotyping and Plasma/Cerebrospinal Fluid Profiling of a Cohort of Frontotemporal Dementia-Amyotrophic Lateral Sclerosis Patients

Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are part of the same pathophysiological spectrum and have common genetic and cerebrospinal fluid (CSF) biomarkers. Our aim here was to identify causative gene variants in a cohort of Greek patients with FTD, ALS and FTD-ALS, to measure levels of CSF biomarkers and to investigate genotype-phenotype/CSF biomarker associations. In this cohort of 130 patients (56 FTD, 58 ALS and 16 FTD-ALS), we performed C9orf72 hexanucleotide repeat expansion analysis, whole exome sequencing and measurement of “classical” (Aβ₄₂, total tau and phospho-tau) and novel (TDP-43) CSF biomarkers and plasma progranulin. Through these analyses, we identified 14 patients with C9orf72 repeat expansion and 11 patients with causative variants in other genes (three in TARDBP, three in GRN, three in VCP, one in FUS, one in SOD1). In ALS patients, we found that levels of phospho-tau were lower in C9orf72 repeat expansion and MAPT c.855C>T (p.Asp285Asp) carriers compared to non-carriers. Additionally, carriers of rare C9orf72 and APP variants had lower levels of total tau and Aβ₄₂, respectively. Plasma progranulin levels were decreased in patients carrying GRN pathogenic variants. This study expands the genotypic and phenotypic spectrum of FTD/ALS and offers insights in possible genotypic/CSF biomarker associations.

Exploring dementia and neuronal ceroid lipofuscinosis genes in 100 FTD-like patients from 6 towns and rural villages on the Adriatic Sea cost of Apulia

Frontotemporal dementia (FTD) refers to a complex spectrum of clinically and genetically heterogeneous disorders. Although fully penetrant mutations in several genes have been identified and can explain the pathogenic mechanisms underlying a great portion of the Mendelian forms of the disease, still a significant number of families and sporadic cases remains genetically unsolved. We performed whole exome sequencing in 100 patients with a late-onset and heterogeneous FTD-like clinical phenotype from Apulia and screened mendelian dementia and neuronal ceroid lipofuscinosis genes. We identified a nonsense mutation in SORL1 VPS domain (p.R744X), in 2 siblings displaying AD with severe language problems and primary progressive aphasia and a near splice-site mutation in CLCN6 (p.S116P) segregating with an heterogeneous phenotype, ranging from behavioural FTD to FTD with memory onset and to the logopenic variant of primary progressive aphasia in one family. Moreover 2 sporadic cases with behavioural FTD carried heterozygous mutations in the CSF1R Tyrosin kinase flanking regions (p.E573K and p.R549H). By contrast, only a minority of patients carried pathogenic C9orf72 repeat expansions (1%) and likely moderately pathogenic variants in GRN (p.C105Y, p.C389fs and p.C139R) (3%). In concert with recent studies, our findings support a common pathogenic mechanisms between FTD and neuronal ceroid lipofuscinosis and suggests that neuronal ceroid lipofuscinosis genes should be investigated also in dementia patients with predominant frontal symptoms and language impairments.

Characterization of novel progranulin gene variants in Italian patients with neurodegenerative diseases

Loss-of-function mutations in the gene encoding for the protein progranulin (PGRN), GRN, are one of the major genetic abnormalities involved in frontotemporal lobar degeneration. However, genetic variations, mainly missense, in GRN have also been linked to other neurodegenerative diseases. We found 12 different pathogenic/likely pathogenic variants in 21 patients identified in a cohort of Italian patients affected by various neurodegenerative disorders. We detected the p.Thr272SerfsTer10 as the most frequent, followed by the c.1179+3A>G variant. We characterized the clinical phenotype of 12 patients from 3 pedigrees carrying the c.1179+3A>G variant, demonstrated the pathogenicity of this mutation, and detected other rarer variants causing haploinsufficiency (p.Met1?, c.709-2A>T, p.Gly79AspfsTer39). Finally, by applying bioinformatics, neuropathological, and biochemical studies, we characterized 6 missense/synonymous variants (p.Asp94His, p.Gly117Asp, p.Ala266Pro, p.Val279Val, p.Arg298His, p.Ala505Gly), including 4 previously unreported. The designation of variants is crucial for genetic counseling and the enrollment of patients in clinical studies.

Peripheral GRN mRNA and Serum Progranulin Levels as a Potential Indicator for Both the Presence of Splice Site Mutations and Individuals at Risk for Frontotemporal Dementia

Progranulin (GRN) gene mutations are a major cause of frontotemporal dementia (FTD). Most mutations identified to date are null mutations, which are predicted to cause the pathology via haploinsufficiency. Decreased peripheral progranulin protein (PGRN) levels are associated with the presence of GRN null mutations and are accepted as reliable biomarkers. In this study, our aim was to test whether the presence of specific GRN splice site mutations (c.- 8+2T>G and c.708+6_9del), could be predicted by peripheral mRNA or protein GRN levels, by studying affected and asymptomatic individuals from FTD families. We also tested four missense GRN variants to assess if altered GRN levels depended on the type of mutation.Our results confirmed a reduction in both mRNA and protein PGRN levels in the splice site mutation carriers, which is consistent with previous reports for null mutations. Our results also suggested that both decreased peripheral GRN mRNA and serum PGRN levels indicate the presence of pathogenic mutations in affected individuals, and identify the asymptomatic individuals at risk, without previous knowledge of genetic status. Both inferences suggest a potential use of peripheral GRN mRNA or serum PGRN levels as biomarkers for families with FTD.

Genotype-phenotype links in frontotemporal lobar degeneration

Frontotemporal lobar degeneration (FTLD) represents a group of neurodegenerative brain diseases with highly heterogeneous clinical, neuropathological and genetic characteristics. This high degree of heterogeneity results from the presence of several different underlying molecular disease processes; consequently, it is unlikely that all patients with FTLD will benefit from a single therapy. Therapeutic strategies for FTLD are currently being explored, and tools are urgently needed that enable the selection of patients who are the most likely to benefit from a particular therapy. Definition of the phenotypic characteristics in patients with different FTLD subtypes that share the same underlying disease processes would assist in the stratification of patients into homogeneous groups. The most common subtype of FTLD is characterized by TAR DNA-binding protein 43 (TDP43) pathology (FTLD-TDP). In this group, pathogenic mutations have been identified in four genes: C9orf72, GRN, TBK1 and VCP. Here, we provide a comprehensive overview of the phenotypic characteristics of patients with FTLD-TDP, highlighting shared features and differences among groups of patients who have a pathogenic mutation in one of these four genes.

RNA Degradation in Neurodegenerative Disease

Ribonucleic acid (RNA) homeostasis is dynamically modulated in response to changing physiological conditions. Tight regulation of RNA abundance through both transcription and degradation determines the amount, timing, and location of protein translation. This balance is of particular importance in neurons, which are among the most metabolically active and morphologically complex cells in the body. As a result, any disruptions in RNA degradation can have dramatic consequences for neuronal health. In this chapter, we will first discuss mechanisms of RNA stabilization and decay. We will then explore how the disruption of these pathways can lead to neurodegenerative disease.

Clinical and genetic analyses of familial and sporadic frontotemporal dementia patients in Southern Italy

INTRODUCTION

We investigated the clinical differences between familial and sporadic frontotemporal dementia (FTD), screening for mutations in known FTD genes.

METHODS

We diagnosed 22 affected individuals belonging to eight families and 43 sporadic cases with FTD in Apulia, Southern Italy, in 2 years. Mutations in common causative FTD genes (GRN, MAPT, VCP, and TARDBP) and C9ORF72 expansions were screened.

RESULTS

Behavioral variant of FTD was the most common clinical subtype (50% and 69% in familial and sporadic cases, respectively). Social conduct impairment/disinhibition, loss of insight, and inflexibility were the most frequent clinical features observed at onset. One new mutation was identified in GRN in family A.

DISCUSSION

Disease onset in sporadic FTD was more frequently characterized by a clustering of behavioral symptoms with apathy and loss of personal hygiene. Mutations in common causative FTD genes are not a major cause of familial and sporadic FTD in the Southern Italian population.