Genetic Spectrum and Clinical Heterogeneity of Chinese Frontotemporal Dementia Patients: Data from PUMCH Dementia Cohort

GRN mutation spectrum and genotype-phenotype correlation in Chinese dementia patients: data from PUMCH dementia cohort

BACKGROUND

METHODS: The GRN mutations, especially of the loss of function type, are causative of frontotemporal dementia (FTD). However, several GRN variants can be found in other neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease. So far, there have been over 300 GRN mutations reported globally. However, the genetic spectrum and phenotypic characteristics have not been fully elucidated in Chinese population.The participants were from the dementia cohort of Peking Union Medical College Hospital (n=1945). They received history inquiry, cognitive evaluation, brain imaging and exome sequencing. The dementia subjects carrying the rare variants of the GRN were included in this study. Those with the pathogenic or likely pathogenic variants of other dementia-related genes were excluded.

RESULTS

14 subjects carried the rare variants of GRN. They were clinically diagnosed with behavioural variant of FTD (n=2), non-fluent/agrammatic variant primary progressive aphasia (PPA, n=3), semantic variant PPA (n=1), AD (n=6) and mixed dementia (n=2). 13 rare variants of GRN were found, including 6 novel variants (W49X, S226G, M152I, A91E, G79E and A303S). The most prevalent symptom was amnesia (85.7%, 12/14), followed by psychiatric and behavioural disorder (78.6%, 11/14). In terms of lobar atrophy, temporal atrophy/hypometabolism was the most common (85.7%, 12/14), followed by parietal atrophy/hypometabolism (78.6%, 11/14).

CONCLUSION

The novel GRN variants identified in this study contribute to enrich the GRN mutation repertoire. There is phenotypic similarity and diversity among Chinese patients with the GRN mutations.

Primary progressive aphasia: six questions in search of an answer

Here, we review recent progress in the diagnosis and management of primary progressive aphasia-the language-led dementias. We pose six key unanswered questions that challenge current assumptions and highlight the unresolved difficulties that surround these diseases. How many syndromes of primary progressive aphasia are there-and is syndromic diagnosis even useful? Are these truly 'language-led' dementias? How can we diagnose (and track) primary progressive aphasia better? Can brain pathology be predicted in these diseases? What is their core pathophysiology? In addition, how can primary progressive aphasia best be treated? We propose that pathophysiological mechanisms linking proteinopathies to phenotypes may help resolve the clinical complexity of primary progressive aphasia, and may suggest novel diagnostic tools and markers and guide the deployment of effective therapies.

Valosin containing protein (VCP): initiator, modifier, and potential drug target for neurodegenerative diseases

The AAA+ ATPase valosin containing protein (VCP) is essential for cell and organ homeostasis, especially in cells of the nervous system. As part of a large network, VCP collaborates with many cofactors to ensure proteostasis under normal, stress, and disease conditions. A large number of mutations have revealed the importance of VCP for human health. In particular, VCP facilitates the dismantling of protein aggregates and the removal of dysfunctional organelles. These are critical events to prevent malfunction of the brain and other parts of the nervous system. In line with this idea, VCP mutants are linked to the onset and progression of neurodegeneration and other diseases. The intricate molecular mechanisms that connect VCP mutations to distinct brain pathologies continue to be uncovered. Emerging evidence supports the model that VCP controls cellular functions on multiple levels and in a cell type specific fashion. Accordingly, VCP mutants derail cellular homeostasis through several mechanisms that can instigate disease. Our review focuses on the association between VCP malfunction and neurodegeneration. We discuss the latest insights in the field, emphasize open questions, and speculate on the potential of VCP as a drug target for some of the most devastating forms of neurodegeneration.

Progranulin Gene Mutations in Chinese Patients with Frontotemporal Dementia: A Case Report and Literature Review

BACKGROUND

Progranulin (GRN) mutations in frontotemporal dementia (FTD) have been less frequently reported in China than in Western countries.

OBJECTIVE

This study reports a novel GRN mutation and summarizes the genetic and clinical features of patients with GRN mutations in China.

METHODS

Comprehensive clinical, genetic, and neuroimaging examinations were conducted on a 58-year-old female patient diagnosed with semantic variant primary progressive aphasia. A literature review was also conducted and clinical and genetic features of patients with GRN mutations in China were summarized.

RESULTS

Neuroimaging revealed marked lateral atrophy and hypometabolism in the left frontal, temporal, and parietal lobes. The patient was negative for pathologic amyloid and tau deposition by positron emission tomography. A novel heterozygous 45-bp deletion (c.1414-14_1444delCCCTTCCCCGCCAGGCTGTGTGCTGCGAGGATCGCCAGCACTGCT) was detected by whole-exome sequencing of the patient's genomic DNA. Nonsense-mediated mRNA decay was presumed to be involved in the degradation of the mutant gene transcript. The mutation was deemed pathogenic according to American College of Medical Genetics and Genomics criteria. The patient had a reduced plasma GRN level. In the literature, there were reports of 13 Chinese patients - mostly female - with GRN mutations; the prevalence was 1.2% -2.6% and patients mostly had early disease onset.

CONCLUSION

Our findings expand the mutation profile of GRN in China, which can aid the diagnosis and treatment of FTD.