A role of the frontotemporal lobar degeneration risk factor TMEM106B in myelination.
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ABSTRACT:
SUBMITTER: Feng T
PROVIDER: S-EPMC7363491 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Recently, the first genome-wide association (GWA) study in frontotemporal lobar degeneration (FTLD) identified common genetic variability at the TMEM106B gene on chromosome 7p21.3 as a potential important risk-modifying factor for FTLD with pathologic inclusions of TAR DNA-binding protein (FTLD-TDP), the most common pathological subtype in FTLD. To gather additional evidence for the implication of TMEM106B in FTLD risk, multiple replication studies in geographically distinct populations were set up. In this review, we revise all recent replication and follow-up studies of the FTLD-TDP GWA study and summarize the growing body of evidence that establish TMEM106B as a bona fide risk factor for FTLD. With the TMEM106B gene, a new player has been identified in the pathogenic cascade of FTLD which could hold important implications for the future development of disease-modifying therapies.
| S-EPMC3207134 | biostudies-literature
Project description:Haploinsufficiency of Progranulin (PGRN), a gene encoding a secreted glycoprotein, is a major cause of frontotemporal lobar degeneration with ubiquitin (FTLD-U) positive inclusions. Single nucleotide polymorphisms in the TMEM106B gene were recently discovered as a risk factor for FTLD-U, especially in patients with PGRN mutations. TMEM106B is also associated with cognitive impairment in amyotrophic lateral sclerosis patients. Despite these studies, little is known about TMEM106B at molecular and cellular levels and how TMEM106B contributes to FTLD. Here, we show that TMEM106B is localized in the late endosome/lysosome compartments and TMEM106B levels are regulated by lysosomal activities. Ectopic expression of TMEM106B induces morphologic changes of lysosome compartments and delays the degradation of endocytic cargoes by the endolysosomal pathway. Furthermore, overexpression of TMEM106B correlates with elevated levels of PGRN, possibly by attenuating lysosomal degradation of PGRN. These results shed light on the cellular functions of TMEM106B and the roles of TMEM106B in the pathogenesis of FTLD-U with PGRN mutations.
| S-EPMC3554197 | biostudies-literature
Project description:TMEM106B was identified as a major risk factor in a genome-wide association study for frontotemporal lobar degeneration (FTLD) with TAR DNA-binding protein (TDP)-43 pathology. The most significant association of TMEM106B single nucleotide polymorphisms with risk of FTLD-TDP was observed in patients with progranulin (GRN) mutations. Subsequent studies suggested an inverse correlation between TMEM106B expression and GRN levels in patient serum. However, in this study, this was not confirmed as we failed to detect a significant alteration of GRN levels upon knockdown or exogenous expression of TMEM106B in heterologous cells. To provide a basis for understanding TMEM106B function in health and disease, we investigated the membrane orientation and subcellular localization of this completely uncharacterized protein. By differential membrane extraction and sequential mutagenesis of potential N-glycosylation sites, we identified TMEM106B as a type 2 integral membrane protein with a highly glycosylated luminal domain. Glycosylation is partially required for the transport of TMEM106B beyond the endoplasmic reticulum to late cellular compartments. Endogenous as well as overexpressed TMEM106B localizes to late endosomes and lysosomes. Interestingly, the inhibition of vacuolar H(+)-ATPases significantly increased the levels of TMEM106B, a finding that may provide an unexpected biochemical link to GRN, because this protein is also strongly increased under the same conditions. Our findings provide a biochemical and cell biological basis for the understanding of the pathological role of TMEM106B in FTLD, an incurable neurodegenerative disorder.
| S-EPMC3365973 | biostudies-literature
Project description:In a genome-wide association study of frontotemporal lobar degeneration with pathological inclusions of TAR DNA-binding protein, significant association was obtained with three single nucleotide polymorphisms at 7p21.3, in a region encompassing the gene TMEM106B. This study also suggested a potential modifying effect of TMEM106B on disease since the association was strongest in progranulin mutation carriers. Further, the risk effect seemed to correlate with increased TMEM106B expression in patients. In the present study, we sought to replicate these three findings using an independent Flanders-Belgian cohort of primarily clinically diagnosed patients with frontotemporal lobar degeneration (n = 288). We were able to confirm the association with TMEM106B with a P-value of 0.008 for rs1990622, the top marker from the genome-wide association study [odds ratio 0.75 (95% confidence interval 0.61-0.93)]. Further, high-density single nucleotide polymorphism mapping suggested that the association was solely driven by the gene TMEM106B. Homozygous carriers of the TMEM106B protective alleles had a 50% reduced risk of developing frontotemporal lobar degeneration. However, we were unable to detect a modifying effect of the TMEM106B single nucleotide polymorphisms on onset age in progranulin mutation carriers belonging to an extended, clinical and pathological well-documented founder family segregating a progranulin null mutation. Also, we could not observe significant differences in messenger RNA expression between patients and control individuals in lymphoblast cell lines and in brain frontal cortex. In conclusion, we replicated the genetic TMEM106B association in a primarily clinically diagnosed cohort of patients with frontotemporal lobar degeneration from Flanders-Belgium. Additional studies are needed to unravel the molecular role of TMEM106B in disease onset and pathogenesis.
| S-EPMC3044834 | biostudies-literature
Project description:Hexanucleotide repeat expansions in chromosome 9 open reading frame 72 (C9orf72) have recently been linked to frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis, and may be the most common genetic cause of both neurodegenerative diseases. Genetic variants at TMEM106B influence risk for the most common neuropathological subtype of FTLD, characterized by inclusions of TAR DNA-binding protein of 43 kDa (FTLD-TDP). Previous reports have shown that TMEM106B is a genetic modifier of FTLD-TDP caused by progranulin (GRN) mutations, with the major (risk) allele of rs1990622 associating with earlier age at onset of disease. Here, we report that rs1990622 genotype affects age at death in a single-site discovery cohort of FTLD patients with C9orf72 expansions (n = 14), with the major allele correlated with later age at death (p = 0.024). We replicate this modifier effect in a 30-site international neuropathological cohort of FTLD-TDP patients with C9orf72 expansions (n = 75), again finding that the major allele associates with later age at death (p = 0.016), as well as later age at onset (p = 0.019). In contrast, TMEM106B genotype does not affect age at onset or death in 241 FTLD-TDP cases negative for GRN mutations or C9orf72 expansions. Thus, TMEM106B is a genetic modifier of FTLD with C9orf72 expansions. Intriguingly, the genotype that confers increased risk for developing FTLD-TDP (major, or T, allele of rs1990622) is associated with later age at onset and death in C9orf72 expansion carriers, providing an example of sign epistasis in human neurodegenerative disease.
| S-EPMC4003885 | biostudies-literature
Project description:Frontotemporal lobar degeneration (FTLD) is now recognised as a common form of early onset dementia. Up to 40% of patients have a family history of disease demonstrating a large genetic component to its etiology. Linkage to chromosome 9p21 has recently been reported in families with this disorder. We undertook a large scale two-stage linkage disequilibrium mapping approach of this region in the Manchester FTLD cohort. We identified association of ubiquitin associated protein 1 (UBAP1; OR 1.42 95% CI 1.08-1.88, P=0.013) with FTLD in this cohort and we replicated this finding in an additional two independent cohorts from the Netherlands (OR 1.33 95% CI 1.04-1.69, P=0.022), the USA (OR 1.4 95% CI 1.02-1.92, P=0.032) and a forth Spanish cohort approached significant association (OR 1.45 95% CI 0.97-2.17, P=0.064). However, we failed to replicate in a fifth cohort from London (OR 0.99 95% CI 0.72-1.37, P=0.989). Quantitative analysis of UBAP1 mRNA extracted from tissue from the Manchester cases demonstrated a significant reduction of expression from the disease-associated haplotype. In addition, we identified a case of familial FTLD that demonstrated colocalisation of UBAP1 and TDP-43 in the neuronal cytoplasmic inclusions in the brain of this individual. Our data for the first time identifies UBAP1 as a genetic risk factor for FTLD and suggests a mechanistic relationship between this protein and TDP-43.
| S-EPMC2753870 | biostudies-literature
Project description:BackgroundFrontotemporal lobar degeneration (FTLD) is the second most common cause of dementia in individuals under 65 years old and manifests as alterations in behavior, personality, or language secondary to degeneration of the frontal and/or temporal lobes. FTLD-TDP, the largest neuropathological subset of FTLD, is characterized by hyperphosphorylated, ubiquitinated TAR DNA-binding protein 43 (TDP-43) inclusions. Mutations in progranulin (GRN), a neuroprotective growth factor, are one of the most common Mendelian genetic causes of FTLD-TDP. Moreover, a recent genome-wide association study (GWAS) identified multiple SNPs within the uncharacterized gene TMEM106B that significantly associated with FTLD-TDP, suggesting that TMEM106B genotype confers risk for FTLD-TDP. Indeed, TMEM106B expression levels, which correlate with TMEM106B genotype, may play a role in the pathogenesis of disease.ResultsSince little is known about TMEM106B and its expression in human brain, we performed immunohistochemical studies of TMEM106B in postmortem human brain samples from normal individuals, FTLD-TDP individuals with and without GRN mutations, and individuals with other neurodegenerative diseases. We find that TMEM106B protein is cytoplasmically expressed in both histopathologically affected and unaffected areas of the brain by neurons, glia, and endothelial cells/pericytes. Furthermore, we demonstrate that TMEM106B expression may differ among neuronal subtypes. Finally, we show that TMEM106B neuronal expression is significantly more disorganized in FTLD-TDP cases with GRN mutations, compared to normal and disease controls, including FTLD-TDP cases without GRN mutations.ConclusionsOur data provide an initial neuropathological characterization of the newly discovered FTLD-TDP-associated protein TMEM106B. In addition, we demonstrate that FTLD-TDP cases with GRN mutations exhibit a loss of neuronal TMEM106B subcellular localization, adding to evidence that TMEM106B and progranulin may be pathophysiologically linked in FTLD-TDP.
| S-EPMC3893524 | biostudies-literature
Project description:We assessed the significance and nature of delusions in frontotemporal lobar degeneration (FTLD), an important cause of young-onset dementia with prominent neuropsychiatric features that remain incompletely characterised. The case notes of all patients meeting diagnostic criteria for FTLD attending a tertiary level cognitive disorders clinic over a three year period were retrospectively reviewed and eight patients with a history of delusions were identified. All patients underwent detailed clinical and neuropsychological evaluation and brain MRI. The diagnosis was confirmed pathologically in two cases. The estimated prevalence of delusions was 14%. Delusions were an early, prominent and persistent feature. They were phenomenologically diverse; however paranoid and somatic delusions were prominent. Behavioural variant FTLD was the most frequently associated clinical subtype and cerebral atrophy was bilateral or predominantly right-sided in most cases. We conclude that delusions may be a clinical issue in FTLD, and this should be explored further in future work.
| S-EPMC2756566 | biostudies-other
Project description:Frontotemporal lobar degeneration (FTLD) includes a spectrum of disorders characterized by changes of personality and social behavior and, often, a gradual and progressive language dysfunction. In the last years, several efforts have been fulfilled in identifying both genetic mutations and pathological proteins associated with FTLD. The molecular bases undergoing the onset and progression of the disease remain still unknown. Recent literature prompts an involvement of RNA metabolism in FTLD, particularly microRNAs (miRNAs). Dysregulation of miRNAs in several disorders, including neurodegenerative diseases, and increasing importance of circulating miRNAs in different pathologies has suggested to implement the study of their possible application as biological markers and new therapeutic targets; moreover, miRNA-based therapy is becoming a powerful tool to deepen the function of a gene, the mechanism of a disease, and validate therapeutic targets. Regarding FTLD, different studies showed that miRNAs are playing an important role. For example, several reports have evaluated miRNA regulation of the progranulin gene suggesting that it is under their control, as described for miR-29b, miR-107, and miR-659. More recently, it has been demonstrated that TMEM106B gene, which protein is elevated in FTLD-TDP brains, is repressed by miR-132/212 cluster; this post-transcriptional mechanism increases intracellular levels of progranulin, affecting its pathways. These findings if confirmed could suggest that these microRNAs have a role as potential targets for some related-FTLD genes. In this review, we focus on the emerging roles of the miRNAs in the pathogenesis of FTLD.
| S-EPMC4746266 | biostudies-literature
Project description:The term frontotemporal lobar degeneration (FTLD) refers to a group of progressive brain diseases, which preferentially involve the frontal and temporal lobes. Depending on the primary site of atrophy, the clinical manifestation is dominated by behavior alterations or impairment of language. The onset of symptoms usually occurs before the age of 60 years, and the mean survival from diagnosis varies between 3 and 10 years. The prevalence is estimated at 15 per 100,000 in the population aged between 45 and 65 years, which is similar to the prevalence of Alzheimer's disease in this age group. There are two major clinical subtypes, behavioral-variant frontotemporal dementia and primary progressive aphasia. The neuropathology underlying the clinical syndromes is also heterogeneous. A common feature is the accumulation of certain neuronal proteins. Of these, the microtubule-associated protein tau (MAPT), the transactive response DNA-binding protein, and the fused in sarcoma protein are most important. Approximately 10% to 30% of FTLD shows an autosomal dominant pattern of inheritance, with mutations in the genes for MAPT, progranulin (GRN), and in the chromosome 9 open reading frame 72 (C9orf72) accounting for more than 80% of familial cases. Although significant advances have been made in recent years regarding diagnostic criteria, clinical assessment instruments, neuropsychological tests, cerebrospinal fluid biomarkers, and brain imaging techniques, the clinical diagnosis remains a challenge. To date, there is no specific pharmacological treatment for FTLD. Some evidence has been provided for serotonin reuptake inhibitors to reduce behavioral disturbances. No large-scale or high-quality studies have been conducted to determine the efficacy of non-pharmacological treatment approaches in FTLD. In view of the limited treatment options, caregiver education and support is currently the most important component of the clinical management.
| S-EPMC3928059 | biostudies-literature