Biology subjects

Unni, V. K.

Publications and source records attributed to Unni, V. K..

7 recordsLinked to original sources

bioRxiv2026

The Parkinson's disease-associated A53E mutation decreases alpha-synuclein aggregation and phosphorylation in vivo

Abnormal -synuclein aggregation is the defining feature of Parkinson's disease (PD) and related synucleinopathies. Rare disease-causing alpha-synuclein mutations either accelerate or slow fibrillization in vitro, however their effects in vivo are less well understood. Interestingly, the A53E mutation slows fibrillization in vitro but causes a more virulent form of PD. We use an in vivo model to examine the aggregation dynamics of disease-causing A53E and E46K alpha-synuclein mutations. Fluorescence recovery after photobleaching within presynaptic terminals shows that A53E-alpha-synuclein is significantly more mobile than E46K- or wild-type (WT)-alpha-synuclein. Longitudinal analysis in vivo reveals that E46K- and WT-alpha-synuclein become progressively less mobile over days, while A53E maintains high mobility, suggesting delayed progression toward aggregated states. We also find that A53E-alpha-synuclein lacks detectable disease-relevant phosphorylation at serine-129, unlike E46K-and WT-alpha-synuclein. To mechanistically test whether this unique lack of phosphorylation drives its high mobility, we genetically modified A53E-alpha-synuclein to mimic S129 phosphorylation, and show that this manipulation indeed decreases its mobility, directly implicating the phosphorylation status of this residue in mobility.

neuroscience↗

bioRxiv2025

The Christchurch point mutation in mouse APOE reduces Aβ-induced tau and α-synuclein pathologies

Apolipoprotein E (APOE) genotype is well known to influence both amyloid-{beta} (A{beta}) and tau pathologies and risk for Alzheimers disease (AD), but it also affects -synuclein (-syn) levels, Lewy pathology and risk of dementia in Parkinsons disease (PD) and dementia with Lewy bodies (DLB). The APOE-R136S (Christchurch, CC) point mutation has been shown to protect against AD pathology and dementia, however, the molecular mechanisms underlying this protection and its effects on -syn pathology are not well understood. Using CRISPR/Cas9 technology, we created a CC arginine-to-serine point mutation at the conserved location in mouse APOE (R128S) to understand its effects on A{beta}, tau and -syn pathologies. We crossed these APOE CC mice to 5xFAD, PS19 and A53T-Syn-GFP (A53T) mice. Using these various double mutant mice, we tested the effect of mouse APOE CC on different proteinopathies, including A{beta}, tau, A{beta}-induced tau after paired helical filament (PHF)-tau intracortical injections, and -syn after preformed fibril (PFF) intracortical and intramuscular injections. We used immunohistochemical, biochemical and behavioral measures to test for protective effects of APOE CC on these different proteinopathies. Heterozygous (Het) and homozygous (Hom) APOE CC mice showed increased plasma cholesterol and triglyceride levels, as seen in humans, but no differences in body or brain weight, or life expectancy. APOE CC decreased A{beta}-induced tau pathologies in PHF-tau injected 5xFAD;Hom mice but did not change A{beta}-plaque pathology in 5xFAD mice or tau pathology in PS19 mice. Although A{beta} levels, tau levels and mouse sex correlated strongly with the behavioral performance, we only detected subtle effects of APOE CC on anxiety-like behaviors in crosses with 5xFAD, PS19 and PHF-tau injected 5xFAD mice. Interestingly, Het and Hom APOE CC mice both showed reduced formation and spread of Lewy pathology in brain after intracortical -syn PFF injection and reduced formation in spinal cord after -syn PFF injection into the hindlimb gastrocnemius muscle in A53T mice. Our study emphasizes the protective effects of the APOE CC variant against different proteinopathies important for dementia and movement disorders, including A{beta} plaque, tau and -syn, and suggests that targeting APOE CC could provide new therapeutic strategies for AD, DLB and PD. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=123 SRC="FIGDIR/small/686857v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@1104377org.highwire.dtl.DTLVardef@bd6c70org.highwire.dtl.DTLVardef@1a4e44org.highwire.dtl.DTLVardef@1087d7f_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2024

Alpha-synuclein knockout impairs melanoma development and alters DNA damage repair in the TG3 mouse model in a sex-dependent manner

Strong evidence suggests links between Parkinsons Disease (PD) and melanoma, as studies have found that people with PD are at an increased risk of developing melanoma and those with melanoma are at increased risk of developing PD. Although these clinical associations are well-established, the cellular and molecular pathways linking these diseases are poorly understood. Recent studies have found a previously unrecognized role for the neurodegeneration-associated protein alpha-synuclein (Syn) in melanoma; the overexpression of Syn promotes melanoma cell proliferation and metastasis. However, to our knowledge, no studies have investigated the role of Syn in in vivo melanoma models outside of a xenograft paradigm. Our study created and characterized Snca knockout in the spontaneously developing melanoma TG3 mouse line, TG3+/+Snca-/-. We show that Syn loss-of-function significantly delays melanoma onset and slows tumor growth in vivo. Furthermore, decreased tumor volume is correlated with a decreased DNA damage signature and increased apoptotic markers, indicating a role for Syn in modulating the DNA damage response (DDR) pathway. Overall, our study provides evidence that targeting Syn and its role in modulating the DDR and melanomagenesis could serve as a promising new therapeutic target.

cancer biology↗

bioRxiv2024

Aquaporin-4 mis-localization slows glymphatic clearance of α-synuclein and promotes α-synuclein pathology and aggregate propagation

The appearance of misfolded and aggregated proteins is a pathological hallmark of numerous neurodegenerative diseases including Alzheimers disease and Parkinsons disease. Sleep disruption is proposed to contribute to these pathological processes and is a common early feature among neurodegenerative disorders. Synucleinopathies are a subclass of neurodegenerative conditions defined by the presence of -synuclein aggregates, which may not only enhance cell death, but also contribute to disease progression by seeding the formation of additional aggregates in neighboring cells. The mechanisms driving intercellular transmission of aggregates remains unclear. We propose that disruption of sleep-active glymphatic function, caused by loss of precise perivascular AQP4 localization, inhibits -synuclein clearance and facilitates -synuclein propagation and seeding. We examined human post-mortem frontal cortex and found that neocortical -synuclein pathology was associated with AQP4 mis-localization throughout the gray matter. Using a transgenic mouse model lacking the adapter protein -syntrophin, we observed that loss of perivascular AQP4 localization impairs the glymphatic clearance of -synuclein from intersititial to cerebrospinal fluid. Using a mouse model of -synuclein propogation, using pre-formed fibril injection, we observed that loss of perivascular AQP4 localization increased -synuclein aggregates. Our results indicate -synuclein clearance and propagation are mediated by glymphatic function and that AQP4 mis-localization observed in the presence of human synucleinopathy may contribute to the development and propagation of Lewy body pathology in conditions such as Lewy Body Dementia and Parkinsons disease. SummaryIn a human postmortem case series, we observe that neocortical Lewy body pathology is associated with mis-localization of the astroglial water channel aquaporin-4 (AQP4). In mice, -synuclein is cleared from the brain along perivascular pathways, while loss of perivascular AQP4 localization impairs glymphatic -synuclein clearance to the CSF. Furthermore, loss of perivascular AQP4 localization promotes the development and propagation of -synuclein aggregates.

neuroscience↗

bioRxiv2024

Alpha-synuclein regulates the repair of genomic DNA double-strand breaks in a DNA-PKcs-dependent manner

-synuclein (Syn) is a presynaptic and nuclear protein that aggregates in important neurodegenerative diseases such as Parkinsons Disease (PD), Parkinsons Disease Dementia (PDD) and Lewy Body Dementia (LBD). Our past work suggests that nuclear Syn may regulate forms of DNA double-strand break (DSB) repair in HAP1 cells after DNA damage induction with the chemotherapeutic agent bleomycin1. Here, we report that genetic deletion of Syn specifically impairs the non-homologous end-joining (NHEJ) pathway of DSB repair using an extrachromosomal plasmid-based repair assay in HAP1 cells. Importantly, induction of a single DSB at a precise genomic location using a CRISPR/Cas9 lentiviral approach also showed the importance of Syn in regulating NHEJ in HAP1 cells and primary mouse cortical neuron cultures. This modulation of DSB repair is dependent on the activity of the DNA damage response signaling kinase DNA-PKcs, since the effect of Syn loss-of-function is reversed by DNA-PKcs inhibition. Using in vivo multiphoton imaging in mouse cortex after induction of Syn pathology, we find an increase in longitudinal cell survival of inclusion-bearing neurons after Polo-like kinase (PLK) inhibition, which is associated with an increase in the amount of aggregated Syn within inclusions. Together, these findings suggest that Syn plays an important physiologic role in regulating DSB repair in both a transformed cell line and in primary cortical neurons. Loss of this nuclear function may contribute to the neuronal genomic instability detected in PD, PDD and DLB and points to DNA-PKcs and PLK as potential therapeutic targets.

neuroscience↗

bioRxiv2024

Alpha-synuclein regulates nucleolar DNA double-strand break repair in melanoma

Although an increased risk of the skin cancer melanoma in people with Parkinsons Disease (PD) has been shown in multiple studies, the mechanisms involved are poorly understood, but increased expression of the PD-associated protein alpha-synuclein (Syn) in melanoma cells may be important. Our previous work suggests that Syn can facilitate DNA double-strand break (DSB) repair, promoting genomic stability. We now show that Syn is preferentially enriched within the nucleolus in the SK-MEL28 melanoma cell line, where it colocalizes with DNA damage markers and DSBs. Inducing DSBs specifically within nucleolar ribosomal DNA (rDNA) increases Syn levels near sites of damage. Syn knockout increases DNA damage within the nucleolus at baseline, after specific rDNA DSB induction, and prolongs the rate of recovery from this induced damage. Syn is important downstream of ATM signaling to facilitate 53BP1 recruitment to DSBs, reducing micronuclei formation and promoting cellular proliferation, migration, and invasion.

cell biology↗

bioRxiv2020

Antisense oligonucleotides targeting alpha-synuclein reduce pre-formed fibril-induced Lewy pathology and improve some domains of cognitive and motor performance

Alpha-synuclein (syn) is a small protein involved in neurodegenerative diseases known as synucleinopathies. The phosphorylated form (psyn) is the primary component of protein aggregates known as Lewy bodies (LBs), which are the hallmark of diseases such as Parkinsons disease (PD) and Dementia with Lewy bodies (DLB). Synucleinopathies might spread in a prion-like fashion, leading to a progressive emergence of symptoms over time. syn pre-formed fibrils (PFFs) induce LB-like pathology in wild-type (WT) mice, but there are remaining questions about the progressive "spreading" of pathology and the cognitive and behavioral effects. Here, we induced LB-like pathology in the bilateral motor cortex of WT mice and assessed behavioral and cognitive performance. As there are no long-term effective treatments for synucleinopathies, and no therapies slow or reduce the spreading of LBs, we also assessed the effects of a mouse syn-targeted antisense oligonucleotides (ASOs) on pathology and behavioral and cognitive performance starting 5 weeks after ASO treatment. At 3 months post-PFF injection (mpi), mice injected with PFFs showed cognitive impairments and mild motor impairments. At 6 mpi, PFF-injected mice showed further cognitive and motor impairments that were partially ameliorated by the ASO. ASO treatment also reduced LB-like pathology, and pathology was significantly correlated with cognitive measures. However, the particular mouse ASO used in these assays was also associated with some possible off-target effects, defined as effects not involving lowering of syn, such as a decline in body weight. These results add to what is known about the progressive nature of the PFF model of synucleinopathies. These data also support the therapeutic potential of ASOs to improve Lewy pathology and associated behavioral and cognitive phenotypes.

neuroscience↗