Unraveling the Genetic Mysteries of Semantic and Right Temporal Variant of FTD

Published on December 8, 2022

Imagine you have two siblings, one with an uncanny knack for understanding meanings and the other with a remarkable talent for recognizing patterns in time. These unique abilities are analogous to the rare clinical phenotypes known as semantic variant of frontotemporal dementia (svFTD) and right temporal variant of frontotemporal dementia (rtvFTD). The underlying pathology of these disorders often involves a protein called TDP-43, but their genetic basis has remained elusive. In a groundbreaking study, scientists performed genetic analysis on a cohort of svFTD and rtvFTD patients to identify associated genetic variants. By scrutinizing a panel of 73 dementia candidate genes, the researchers found intriguing mutations in autophagy and inflammation-related pathways. These findings suggest that molecular analysis should be a standard procedure for all svFTD and rtvFTD patients to unlock the genotype-phenotype correlation and shed light on the pathogenetic mechanisms driving these clinical phenotypes in frontotemporal dementia. Dive into this captivating research to delve deeper into the intricate genetic mysteries of semantic and right temporal variants of FTD!

Semantic and right temporal variant of frontotemporal dementia (svFTD and rtvFTD) are rare clinical phenotypes in which, in most cases, the underlying pathology is TDP-43 proteinopathy. They are usually sporadic disorders, but recent evidences suggest a higher frequency of genetic mutations for the right temporal versus the semantic variant. However, the genetic basis of these forms is not clear. In this study we performed a genetic screening of a single-center cohort of svFTD and rtvFTD patients, aiming at identifying the associated genetic variants. A panel of 73 dementia candidate genes has been analyzed by NGS target sequencing including both causal and risk/modifier genes in 23 patients (15 svFTD and 8 rtvFTD) and 73 healthy age-matched controls. We first performed a single variant analysis considering rare variants and then a gene-based aggregation analysis to evaluate the cumulative effects of multiple rare variants in a single gene. We found 12 variants in nearly 40% of patients (9/23), described as pathogenic or classified as VUS/likely pathogenic. The overall rate was higher in svFTD than in rtvFTD. Three mutations were located in MAPT gene and single mutations in the following genes: SQSTM1, VCP, PSEN1, TBK1, OPTN, CHCHD10, PRKN, DCTN1. Our study revealed the presence of variants in genes involved in pathways relevant for the pathology, especially autophagy and inflammation. We suggest that molecular analysis should be performed in all svFTD and rtvFTD patients, to better understand the genotype–phenotype correlation and the pathogenetic mechanisms that could drive the clinical phenotypes in FTD.

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