Biology subjects

Borchelt, D. R.

Publications and source records attributed to Borchelt, D. R..

7 recordsLinked to original sources

bioRxiv2025

Progressive Supranuclear Palsy PERK haplotype B selectively translates DLX1 promoting tau toxicity

The unfolded protein response (UPR) sensor PERK exists in two haplotypes termed A and B. PERK-B uniquely confers increased risk for tauopathies like progressive supranuclear palsy (PSP), but the mechanisms distinguishing its function from PERK-A and contributing to its association with tau pathology are not known. Here, we developed a controlled cellular model for a pair-wise comparison of the two PERK haplotypes, finding their UPR functions nearly indistinguishable. However, a careful examination employing puromycin-based proteomics revealed that a subset of mRNA translation events were permissible under PERK-B, but not PERK-A, dependent UPR. Critically, one of the targets that escaped PERK-B suppression was the transcription factor DLX1, which has been genetically linked to PSP risk. Here, we found a shift in the solubility of DLX1 in human PSP brain tissue, and report that silencing of DLX-1 reduced the aggregation of tau in mammalian cells. Furthermore, silencing of the fly homolog of DLX1 was sufficient to decrease tau-induced toxicity, in vivo. Our results detail the haplotype-specific PERK-B/DLX-1 pathway as a novel driver of tau pathology in cells, flies, and likely human brain, revealing new insights into PSP pathogenesis and potential therapeutic targets.

neuroscience↗

bioRxiv2024

A combinatorial approach to ALS therapies in the PrP.TDP43-315 model of ALS; complications and tribulations

Effective treatment for sporadic amyotrophic lateral sclerosis has been steadily advancing towards combinatorial therapies. For many years, riluzole was the only approved drug and it offered modest benefits. In 2017, edaravone was approved for ALS and became the first drug to be used in combination with riluzole. In the present study, we have attempted to build on the concepts of combinatorial therapy by testing novel drug combinations in a transgenic mouse model. Mice that express A315T mutant TDP43, using the mouse prion promoter, have been reported to develop many of the symptoms of ALS, including paralysis. Aberrant TDP43 function is a common feature in sporadic ALS, and thus TDP43 transgenic models may recapitulate disease processes that occur in humans with sporadic ALS. Although the PrP.TDP43-A315T model has been reported to develop abnormalities in gut motility that contribute to early mortality, recent studies indicated that gut motility issues could be mitigated by feeding mice with gel-based diets rather than the standard dry chow. In the present study, we have attempted to use the PrP.TDP43-A315T model to test whether we could identify a drug combination that synergized to extend life span in this model substantially. The drug combinations were built around the existing drug modalities, adding additional drugs that had indications of utility from the literature. To mitigate gut motility issues, we fed the mice gel-based diets with or without added drug combinations. Although the gel-based diets extended life expectancy in PrP.TDP43-A315T mice, most of the animals still developed gut motility abnormalities that may have contributed to early mortality. None of the drug combinations we tested extended life expectancy in this model substantially.

neuroscience↗

bioRxiv2024

Human APOE allelic variants suppress the formation of diffuse and fibrillar Aβ deposits relative to mouse Apoe in transgenic mouse models of Alzheimer amyloidosis

BackgroundApolipoprotein E (apoE) modulates the deposition of amyloid {beta} (A{beta}) aggregates in Alzheimers disease (AD) in an isoform-dependent manner. In transgenic mouse models of AD-amyloidosis, replacing mouse Apoe alleles with human APOE variants suppresses fibrillar A{beta} deposits. In the PD-APP transgenic mouse model, deletion of the Apoe gene led to selective reduction of fibrillar deposits with increased diffuse deposits. This finding suggested that apoE may have differential effects on different types of amyloid pathology. MethodsHere, we investigated the interaction between the type of A{beta} pathology in the brain and human apoE isoforms in different transgenic mouse models. ResultsIn the APPsi model that develops predominantly diffuse A{beta} plaques late in life, we determined that replacing mouse Apoe with human APOE3 or APOE4 genes potently suppressed diffuse amyloid formation, with apoE3 exhibiting a greater activity relative to apoE4. Relative to apoE4, apoE3 appeared to suppress A{beta} deposition in the cerebral vasculature. In a second cohort, we accelerated the deposition of diffuse A{beta} pathology by seeding, finding that seeded APPsi mice harboring APOE4 or APOE3 developed equal burdens of diffuse parenchymal A{beta}. Finally, in the recently developed SAA-APP model that has a mix of dense-core and fibrous A{beta} plaques, we found that replacing mouse apoE with human apoE suppressed deposition significantly, with the amyloid burden following the trend of Apoe>>APOE4> APOE3[~]APOE2. In the SAA-APP and seeded APPsi models, we found evidence of apoE protein associated with A{beta} plaques. ConclusionsOverall, these observations demonstrate a capacity for human apoE to suppress the deposition of both diffuse and fibrillar-cored deposits, relative to mouse apoE. Notably, in the seeded paradigm, the suppressive activity of human apoE3 and apoE4 appeared to be overwhelmed. Taken together, this study demonstrates that APOE genotype influences the deposition of both cored-fibrillar and diffuse amyloid.

neuroscience↗

bioRxiv2024

Hyperacetylation mimetics within the tau filament core inhibits prion-like propagation of misfolded tau

The two most prominent post-translational modifications of pathologic tau are Ser/Thr/Tyr phosphorylation and Lys acetylation. Whether acetylation impacts the susceptibility of tau to templated seeding in diseases like Alzheimers disease (AD) and Progressive Supranuclear Palsy (PSP) is largely uncharacterized. Towards this, we examined how acetylation mimicking or nullifying mutations on five sites of tau (K311, K353, K369, K370, K375), located within the tau filament core, influenced the susceptibility of P301L (PL) tau to seeds from AD (AD-tau) or PSP (PSP-tau) in HEK293T cells. Acetyl-mimicking substitutions of individual Lys sites to Glutamine as well as mutation of all 5 sites together (PL+5K-Q and PL+5K-R) had inconsistent effects on tau seeding by AD-tau or PSP-tau seeds. Unexpectedly, mutating all 5 sites to Alanine (PL+5K-A) resulted in a tau variant that spontaneously aggregated. These aggregates were amorphous and yet able to propagate to naive cells expressing P301L tau but not wild-type tau. Previously, we reported that a phospho-mimetic S305E mutation in PL tau abrogated seeding by AD-tau but not PSP-tau seeds in the HEK293T cells. To assess how changes in acetylation and phosphorylation together could influence seeding, we combined the S305E and the 5K-Q mutations in P301L tau, creating a variant that retained specificity for PSP-tau seeds over AD-tau seeds. Our findings indicate that phosphorylation of tau at Ser305 is a strong determinant of disease-specific tau templating, even in the presence of hyperacetylation within the fibril core domain. Overall, our findings suggest that acetylation could be a secondary modifier of misfolded hyperphosphorylated tau seeds.

neuroscience↗

bioRxiv2023

Aβ Amyloid Scaffolds the Accumulation of Matrisome and Additional Proteins in Alzheimer's Disease

We report a highly significant correlation between human Alzheimers disease (AD) brain proteome changes and those in CRND8 APP695NL/F transgenic mice. Comparing protein changes observed in the CRND8 mice with co-expression networks derived from human Alzheimers disease (AD), reveals both conserved and divergent module changes. Many proteins in the most highly conserved module (M42, matrisome) accumulate in plaques, cerebrovascular amyloid (CAA), dystrophic neuronal processes, or a combination thereof. Overexpression of two M42 proteins, midkine (Mdk) and pleiotrophin (PTN), in CRND8 mice brains leads to increased accumulation of A{beta} in plaques and in blood vessels; further, recombinant MDK and PTN enhance A{beta} aggregation into amyloid structures. Multiple M42 proteins bind to fibrillar A{beta}42 and a non-human amyloid fibril in vitro. Supporting this binding data, MDK and PTN co-accumulate with transthyretin (TTR) amyloid in the heart. Notably, our findings establish that proteomic changes in modules observed in human AD brains define an A{beta} amyloid "responsome" that is well conserved from mouse models to humans. Further, distinct amyloid structures appear to serve as scaffolds, facilitating the co-accumulation of proteins with signaling functions, and this co-accumulation may contribute to downstream pathological sequalae. Overall, this contextualized understanding of proteomic changes and their interplay with amyloid deposition provides valuable insights into the complexity of AD pathogenesis and potential biomarkers and therapeutic targets.

neuroscience↗

bioRxiv2023

Assessment of levamisole HCl and thymosin α1 in two mouse models of amyotrophic lateral sclerosis

Amyotrohpic lateral sclerosis (ALS) is a progressive neurodegenerative disease that causes generalized muscle weakness and atrophy. Neuropathologically, ALS is defined by severe loss of upper and lower motor neurons with a robust neuroinflammatory response. In the present study, we have examined the potential utility of two drugs that have indications as immune modulators, levamisole HCl and thymosin 1. These drugs were tested in two models models that reproduce aspects of ALS. We conducted a 14 week dosing study of these two drugs in the SOD1G93A and Prp-TDP43A315T models of ALS. The drugs were given once daily for two weeks and then every other day for 6 weeks for a total of 8 weeks of treatment. Outcome measurements included efficacy assessment on the neuromuscular phenotypes, and pathological analyses of ubiquitin load and neuro-inflammatory markers in spinal motor neurons. Neither of these drug treatments produced significant extensions in survival; however, there were changes in ubiquitin load in SOD1G93A mice that suggest the drugs could be beneficial as additions to other therapies.

neuroscience↗

bioRxiv2018

Enhanced Neurite Outgrowth and Regeneration in ALS Resistant Motor Neurons from SOD1 Mutant Mouse Models

Amyotrophic lateral sclerosis (ALS) is a progressive, fatal neurodegenerative disease characterized by motor neuron cell death. However, not all motor neurons are equally susceptible. Most of what we know about the surviving motor neurons comes from gene expression profiling, less is known about their functional traits. We found that resistant motor neurons cultured from SOD1 ALS mouse models have enhanced axonal outgrowth and dendritic branching. They also have an increase in the number and size of actin-based structures like growth cones and filopodia. These phenotypes occur in cells cultured from presymptomatic mice and mutant SOD1 models that do not develop ALS, but not in embryonic motor neurons. Enhanced outgrowth and upregulation of filopodia can be induced in wild-type adult cells by expressing mutant SOD1. These results demonstrate that mutant SOD1 can enhance the regenerative capability of ALS resistant motor neurons. Capitalizing on this mechanism could lead to new therapeutic strategies.

neuroscience↗