Biology subjects

Tilahun, K.

Publications and source records attributed to Tilahun, K..

4 recordsLinked to original sources

bioRxiv2026

TMEM106B C-terminal fragments drive nucleocytoplasmic transport failure and TDP-43 mislocalization in the aging human brain

TMEM106B is a lysosomal membrane protein and major genetic modifier of multiple neurodegenerative diseases, including frontotemporal lobar degeneration, Alzheimers disease, and amyotrophic lateral sclerosis. Proteolytically generated C-terminal fragments of TMEM106B assemble into amyloid fibrils that accumulate in the brains of individuals with neurodegenerative disease and in cognitively normal aged adults, yet how these fibrils produce neuronal dysfunction has remained unclear. Here, we show that cytosolic and lysosome-directed TMEM106B C-terminal fragments (CTF and gCTF) form detergent-insoluble amyloid aggregates, drive redistribution of endogenous TDP-43 from the nucleus to the cytoplasm, and accelerate neuronal death. Unbiased proximity proteomics identified the inner nuclear membrane LAP1-TorsinA axis as a fragment-specific interactome, and co-immunoprecipitation confirmed a direct physical interaction between gCTF and LAP1 that was not observed with full-length TMEM106B. Fragment expression disrupted Lamin B1 organization, mislocalized the nuclear import machinery KPNB1 and RanGAP1, and impaired importin-dependent nuclear transport in primary cortical neurons. Critically, neurons harboring endogenous TMEM106B fibrillar pathology in aged human frontal cortex exhibited the same phenotypes, namely disrupted Lamin B1 and LAP1 localization and cytoplasmic redistribution of TDP-43, whereas fibril-negative neurons from the same cases and younger control tissue retained intact nuclear envelope organization. These findings define TMEM106B proteinopathy as an upstream driver of nuclear envelope disruption and nucleocytoplasmic transport failure, linking a widespread feature of brain aging to a central mechanism of neurodegeneration.

neuroscience↗

bioRxiv2023

Cross-species transcriptomic analysis identifies mitochondrial dysregulation as a functional consequence of the schizophrenia-associated 3q29 deletion

Recent advances in the genetics of schizophrenia (SCZ) have identified rare variants that confer high disease risk, including a 1.6 Mb deletion at chromosome 3q29 with a staggeringly large effect size (O.R. > 40). Understanding the impact of the 3q29 deletion (3q29Del) on the developing CNS may therefore lead to insights about the pathobiology of schizophrenia. To gain clues about the molecular and cellular perturbations caused by the 3q29 deletion, we interrogated transcriptomic effects in two experimental model systems with complementary advantages: isogenic human forebrain cortical organoids and isocortex from the 3q29Del mouse model. We first created isogenic lines by engineering the full 3q29Del into an induced pluripotent stem cell line from a neurotypical individual. We profiled transcriptomes from isogenic cortical organoids that were aged for 2 months and 12 months, as well as day p7 perinatal mouse isocortex, all at single cell resolution. Differential expression analysis by genotype in each cell-type cluster revealed that more than half of the differentially expressed genes identified in mouse cortex were also differentially expressed in human cortical organoids, and strong correlations were observed in mouse-human differential gene expression across most major cell-types. We systematically filtered differentially expressed genes to identify changes occurring in both model systems. Pathway analysis on this filtered gene set implicated dysregulation of mitochondrial function and energy metabolism, although the direction of the effect was dependent on developmental timepoint. Transcriptomic changes were validated at the protein level by analysis of oxidative phosphorylation protein complexes in mouse brain tissue. Assays of mitochondrial function in human heterologous cells further confirmed robust mitochondrial dysregulation in 3q29Del cells, and these effects are partially recapitulated by ablation of the 3q29Del gene PAK2. Taken together these data indicate that metabolic disruption is associated with 3q29Del and is conserved across species. These results converge with data from other rare SCZ-associated variants as well as idiopathic schizophrenia, suggesting that mitochondrial dysfunction may be a significant but overlooked contributing factor to the development of psychotic disorders. This cross-species scRNA-seq analysis of the SCZ-associated 3q29 deletion reveals that this copy number variant may produce early and persistent changes in cellular metabolism that are relevant to human neurodevelopment.

genomics↗

bioRxiv2022

Antisense, but not sense, repeat expanded RNAs activate PKR/eIF2α-dependent integrated stress response in C9orf72 FTD/ALS

GGGGCC (G4C2) hexanucleotide repeat expansion in the C9orf72 gene is the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). The repeat is bidirectionally transcribed and confers gain of toxicity. However, the underlying toxic species is debated, and it is not clear whether antisense CCCCGG (C4G2) repeat expanded RNAs contribute to disease pathogenesis. Our study shows that C9orf72 (C4G2) antisense repeat expanded RNAs trigger the activation of the PKR/eIF2-dependent integrated stress response independent of dipeptide repeat proteins that are produced through repeat-associated non-AUG initiated translation, leading to global translation inhibition and stress granule formation. Increased phosphorylation of PKR/eIF2 is also observed in the frontal cortex of C9orf72 FTD/ALS patients. Finally, only antisense (C4G2), but not sense (G4C2), repeat expanded RNAs can activate the PKR/eIF2 pathway. These results provide a mechanism by which antisense repeat expanded RNAs elicit neuronal toxicity in FTD/ALS caused by C9orf72 repeat expansions.

neuroscience↗

bioRxiv2021

The functions of SARS-CoV-2 neutralizing and infection-enhancing antibodies in vitro and in mice and nonhuman primates

SARS-CoV-2 neutralizing antibodies (NAbs) protect against COVID-19. A concern regarding SARS-CoV-2 antibodies is whether they mediate disease enhancement. Here, we isolated NAbs against the receptor-binding domain (RBD) and the N-terminal domain (NTD) of SARS-CoV-2 spike from individuals with acute or convalescent SARS-CoV-2 or a history of SARS-CoV-1 infection. Cryo-electron microscopy of RBD and NTD antibodies demonstrated function-specific modes of binding. Select RBD NAbs also demonstrated Fc receptor-{gamma} (Fc{gamma}R)-mediated enhancement of virus infection in vitro, while five non-neutralizing NTD antibodies mediated Fc{gamma}R-independent in vitro infection enhancement. However, both types of infection-enhancing antibodies protected from SARS-CoV-2 replication in monkeys and mice. Nonetheless, three of 31 monkeys infused with enhancing antibodies had higher lung inflammation scores compared to controls. One monkey had alveolar edema and elevated bronchoalveolar lavage inflammatory cytokines. Thus, while in vitro antibody-enhanced infection does not necessarily herald enhanced infection in vivo, increased lung inflammation can occur in SARS-CoV-2 antibody-infused macaques.

immunology↗