Biology subjects

Geier, E. G.

Publications and source records attributed to Geier, E. G..

6 recordsLinked to original sources

bioRxiv2023

Expansion of interferon signaling-associated gene (ISAG)-hi T cells in early-onset Alzheimer's disease

INTRODUCTIONAltered immune signatures are emerging as a central theme in neurodegenerative disease, yet little is known about immune responses in early-onset Alzheimers disease (EOAD). METHODSWe examined single-cell RNA-sequencing (scRNA-seq) data from peripheral blood mononuclear cells (PBMCs) and droplet digital (dd)PCR data from CD4 T cells from participants with EOAD and clinically normal controls. RESULTSWe analyzed ~182,000 PBMCs by scRNA-seq and discovered increased interferon signaling-associated gene (ISAG) expression and striking expansion of antiviral-like ISAGhi T cells in EOAD. We isolated CD4 T cells from additional EOAD cases and confirmed increased expression of ISAGhi marker genes. Publicly available cerebrospinal fluid leukocyte scRNA-seq data from late-onset mild cognitive impairment and AD also revealed increased expression of interferon-response genes. DISCUSSIONISAGhi T cells, apparently primed for antiviral activity, are expanded in EOAD. Additional research into these cells and the role of heightened peripheral IFN signaling in neurodegeneration is warranted.

neuroscience↗

bioRxiv2022

Single-cell RNA-seq reveals alterations in peripheral CX3CR1 and nonclassical monocytes in familial tauopathy

BackgroundEmerging evidence from mouse models is beginning to elucidate the brains immune response to tau pathology, but little is known about the nature of this response in humans. In addition, it remains unclear to what extent tau pathology and the local inflammatory response within the brain influence the broader immune system. MethodsTo address these questions, we performed single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) from carriers of pathogenic variants in MAPT, the gene encoding tau. ResultsAnalysis of [~]181,000 individual PBMC transcriptomes from MAPT pathogenic variant carriers (n = 8) and healthy non-carrier controls (n = 8) demonstrated striking differential expression in monocytes and natural killer (NK) cells. We observed a marked reduction in the expression of CX3CR1 - the gene encoding the fractalkine receptor that is known to modulate tau pathology in mouse models - in monocytes and NK cells. We also observed a significant reduction in the abundance of nonclassical monocytes and dysregulated expression of nonclassical monocyte marker genes, including FCGR3A. Finally, we identified reductions in TMEM176A and TMEM176B, genes thought to be involved in the inflammatory response in human microglia. We confirmed differential expression of select biologically relevant genes dysregulated in our scRNA-seq data using droplet digital PCR as an orthogonal technique for quantitative validation. ConclusionsOur results suggest that human peripheral immune cell expression and abundance are modulated by tau-associated pathophysiologic changes. CX3CR1 and nonclassical monocytes in particular will be a focus of future work exploring the role of these peripheral signals in additional tau-associated neurodegenerative diseases.

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bioRxiv2022

Radiogenomics of C9orf72 expansion carriers reveals global transposable element de-repression and enables prediction of thalamic atrophy and clinical impairment

Hexanucleotide repeat expansion (HRE) within C9orf72 is the most common genetic cause of frontotemporal dementia (FTD). Thalamic atrophy occurs in both sporadic and familial FTD but is thought to distinctly affect HRE carriers. Separately, emerging evidence suggests widespread de-repression of transposable elements (TEs) in the brain in several neurodegenerative diseases, including C9orf72 HRE-mediated FTD (C9-FTD). Whether TE activation can be measured in peripheral blood and how the reduction in peripheral C9orf72 expression observed in HRE carriers relates to atrophy and clinical impairment remain unknown. We used the FreeSurfer pipeline and its extensions to assess the effects of C9orf72 HRE and clinical diagnosis (n = 78) on atrophy of thalamic nuclei. We also generated a novel, whole-blood RNA-seq dataset to determine the relationships between peripheral C9orf72 expression, TE activation, thalamic atrophy, and clinical severity (n = 114). We confirmed global thalamic atrophy and reduced C9orf72 expression in HRE carriers. Moreover, we identified disproportionate atrophy of the right mediodorsal lateral nucleus in HRE carriers and showed that C9orf72 expression associated with clinical severity, independent of thalamic atrophy. Strikingly, we found global peripheral activation of TEs, including the human endogenous LINE-1 element, L1HS. L1HS levels were associated with atrophy of multiple pulvinar nuclei, a thalamic region implicated in C9-FTD. Integration of peripheral transcriptomic and neuroimaging data from HRE carriers revealed atrophy of specific thalamic nuclei; demonstrated that C9orf72 levels relate to clinical severity; and identified marked de-repression of TEs, including L1HS, which predicted atrophy of FTD-relevant thalamic nuclei. Significance StatementPathogenic repeat expansion in C9orf72 is the most frequent genetic cause of frontotemporal dementia and amyotrophic lateral sclerosis (C9-FTD/ALS). The clinical, neuroimaging, and pathological features of C9-FTD/ALS are well-characterized, whereas the intersections of transcriptomic dysregulation and brain structure remain largely unexplored. Herein, we utilized a novel radiogenomic approach to examine the relationship between peripheral blood transcriptomics and thalamic atrophy, a neuroimaging feature disproportionately impacted in C9-FTD/ALS. We confirmed reduction of C9orf72 in blood and found broad dysregulation of transposable elements--genetic elements typically repressed in the human genome--in symptomatic C9orf72 expansion carriers, which associated with atrophy of thalamic nuclei relevant to FTD. C9orf72 expression was also associated with clinical severity, suggesting that peripheral C9orf72 levels capture disease-relevant information.

neuroscience↗

bioRxiv2020

TSC1 loss-of-function increases risk for tauopathy by inducing tau acetylation and preventing autophagy-mediated tau clearance

Age-associated neurodegenerative disorders demonstrating tau-laden intracellular inclusions, including Alzheimers disease (AD), frontotemporal lobar degeneration (FTLD) and progressive supranuclear palsy (PSP), are collectively known as tauopathies. The vast majority of human tauopathies accumulate non-mutant tau rather than mutant forms of the protein, yet cell and animal models for non-mutant tauopathies are lacking. We previously linked a monoallelic mutation in the TSC1 gene to tau accumulation and FTLD. Now, we have identified new variants in TSC1 that predisposed to other tauopathies such as AD and PSP. These new TSC1 risk variants significantly decreased the half-life of TSC1/hamartin in vitro. Cellular and murine models of TSC1 haploinsufficiency (TSC1+/-) accumulated tau protein that exhibited aberrant acetylation on six lysine residues. Tau acetylation hindered its lysosomal degradation via chaperone-mediated autophagy leading to neuronal tau accumulation. Enhanced tau acetylation in TSC1+/- models was achieved through both an increase in p300 acetyltransferase activity and a decrease in SIRT1 deacetylase levels. Pharmacological modulation of either enzyme restored tau levels. Together, these studies substantiate TSC1 as a novel tauopathy risk gene and advance TSC1 haploinsufficiency as a new genetic model for tauopathy. In addition, these results promote acetylated tau as a rational target for diagnostic and therapeutic modalities in multiple tauopathies.

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bioRxiv2019

Non-Coding and Loss-of-Function Coding Variants in TET2 are Associated with Multiple Neurodegenerative Diseases

We conducted genome sequencing to search for rare variation contributing to early onset Alzheimers disease (EOAD) and frontotemporal dementia (FTD). Discovery analysis was conducted on 493 cases and 671 controls of European ancestry. Burden testing for rare variation associated with disease was conducted using filters based on variant rarity (less than 1 in 10,000 or private), computational prediction of deleteriousness (CADD 10 or 15 thresholds), and molecular function (protein loss-of-function only, coding alteration only, or coding plus non-coding variants in experimentally predicted regulatory regions).\n\nReplication analysis was conducted on 16,871 independent cases and 15,941 independent controls. Rare variants in TET2 were enriched in the discovery combined EOAD and FTD cohort (p=6.5x10-8, genome-wide corrected p=0.0037). Most of these variants were canonical loss-of-function or non-coding in predicted regulatory regions. This enrichment replicated across several cohorts of AD and FTD (replication only p=0.0071). The combined analysis odds ratio was 2.2 (95% CI 1.5-3.2) for AD and FTD. The odds ratio for qualifying non-coding variants considered independently from coding variants was 2.1 (95% CI 1.2-3.9). For loss-of-function variants, the combined odds ratio (for AD, FTD, and amyotrophic lateral sclerosis, which shares clinicopathological overlap with FTD) was 3.2 (95% CI 2.0-5.3). TET2 catalyzes DNA demethylation. Given well-defined changes in DNA methylation that occur during aging, rare variation in TET2 may confer risk for neurodegeneration by altering the homeostasis of key aging-related processes. Additionally, our study emphasizes the relevance of non-coding variation in genetic studies of complex disease.

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bioRxiv2019

Genome sequencing for early-onset dementia: high diagnostic yield and frequent observation of multiple contributory alleles

We assessed the utility of genome sequencing for early-onset dementia. Participants were selected from a memory disorders clinic. Genome sequencing was performed along with C9orf72 repeat expansion testing. All returned sequencing results were Sanger validated clinically. Prior clinical diagnoses included Alzheimers disease, frontotemporal dementia, and unspecified dementia. The mean age-of-onset was 54 (41-76). 50% of patients had a strong family history, 37.5% had some, and 12.5% had no known family history. Nine of 32 patients (28%) had a variant defined as pathogenic or likely pathogenic (P/LP) by American College of Medical Genetics standards, including variants in APP, C9orf72, CSF1R, and MAPT. Nine patients (including three with P/LP variants) harbored established risk alleles with moderate penetrance (odds ratios of about 2-5) in ABCA7, AKAP9, GBA, PLD3, SORL1, and TREM2. All six patients harboring these moderate penetrance variants but not P/LP variants also had one or two APOE {varepsilon}4 alleles. One patient had two APOE {varepsilon}4 alleles with no other established contributors. In total, 16 patients (50%) harbored one or more genetic variants likely to explain symptoms. We identified variants of uncertain significance (VUSs) in ABI3, ADAM10, ARSA, GRID2IP, MME, NOTCH3, PLCD1, PSEN1, TM2D3, TNK1, TTC3, and VPS13C, also often along with other variants. In summary, genome sequencing for early-onset dementia demonstrated high utility, with particular advantages where targeted testing may fail such as atypical variant-disease associations or presence of multiple moderate impact alleles. One or more established contributory alleles is often present in early-onset dementia, supporting an oligogenic model.

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