Publications

α-Synuclein (αSyn) is a presynaptic protein of unestablished physiological function that plays a central role in Parkinson's disease neuropathology. To date, the reported effects of αSyn expression on the kinetics of axonal synaptic vesicle exocytosis and membrane cycling have been relatively small. In contrast, we report that αSyn is the major modulator of substantia nigra somatodendritic dopamine release, a little-understood form of neurotransmission that is central to sensorimotor and basal ganglia circuitry. This regulation is due to a previously unknown role for αSyn in controlling the activity of the L-type calcium ion channels (LTCC), which are also implicated in Parkinson's pathogenesis. αSyn-deficient neurons further display decreased spike frequency adaptation, hippocampal LTCC-dependent long-term potentiation, and immediate early gene induction, functions that are essential for synaptic adaptation and neuronal plasticity.

Alzheimer's disease is a prominent chronic neurodegenerative condition characterized by a gradual decline in memory leading to dementia. Growing evidence suggests that Alzheimer's disease is associated with accumulating various amyloid-β oligomers in the brain, influenced by complex genetic and environmental factors. The memory and cognitive deficits observed during the prodromal and mild cognitive impairment phases of Alzheimer's disease are believed to primarily result from synaptic dysfunction. Throughout life, environmental factors can lead to enduring changes in gene expression and the emergence of brain disorders. These changes, known as epigenetic modifications, also play a crucial role in regulating the formation of synapses and their adaptability in response to neuronal activity. In this context, we highlight recent advances in understanding the roles played by key components of the epigenetic machinery, specifically DNA methylation, histone modification, and microRNAs, in the development of Alzheimer's disease, synaptic function, and activity-dependent synaptic plasticity. Moreover, we explore various strategies, including enriched environments, exposure to non-invasive brain stimulation, and the use of pharmacological agents, aimed at improving synaptic function and enhancing long-term potentiation, a process integral to epigenetic mechanisms. Lastly, we deliberate on the development of effective epigenetic agents and safe therapeutic approaches for managing Alzheimer's disease. We suggest that addressing Alzheimer's disease may require distinct tailored epigenetic drugs targeting different disease stages or pathways rather than relying on a single drug.

BACKGROUND: Parkinson's disease (PD) affects millions of people worldwide, but only 5-10% of patients suffer from a monogenic form of the disease with Mendelian inheritance. SNCA, the gene encoding for the protein alpha-synuclein (aSyn), was the first to be associated with familial forms of PD and, since then, several missense variants and multiplications of the SNCA gene have been established as rare causes of autosomal dominant forms of PD.

AIM AND METHODS: A patient carrying aSyn missense mutation and his family members were studied. We present the clinical features, genetic testing - whole exome sequencing (WES), and neuropathological findings. The functional consequences of this aSyn variant were extensively investigated using biochemical, biophysical, and cellular assays.

RESULTS: The patient exhibited a complex neurodegenerative disease that included generalized myocloni, bradykinesia, dystonia of the left arm and apraxia. WES identified a novel heterozygous SNCA variant (cDNA 40G>A; protein G14R). Neuropathological examination showed extensive atypical aSyn pathology with frontotemporal lobar degeneration (FTLD) and nigral degeneration pattern with abundant ring-like neuronal inclusions, and few oligodendroglial inclusions. Sanger sequencing confirmed the SNCA variant in the healthy, elderly parent of the patient patient suggesting incomplete penetrance. NMR studies suggest that the G14R mutation induces a local structural alteration in aSyn, and lower thioflavin T binding in in vitro fibrillization assays. Interestingly, the G14R aSyn fibers display different fibrillar morphologies as revealed by cryo-electron microscopy. Cellular studies of the G14R variant revealed increased inclusion formation, enhanced membrane association, and impaired dynamic reversibility of serine-129 phosphorylation.

SUMMARY: The atypical neuropathological features observed, which are reminiscent of those observed for the G51D aSyn variant, suggest a causal role of the SNCA variant with a distinct clinical and pathological phenotype, which is further supported by the properties of the mutant aSyn, compatible with the strain hypothesis of proteinopathies.

α-Synuclein (αS) is a 140 amino-acid neuronal protein highly enriched in presynaptic nerve terminals. Its progressive accumulation in Lewy bodies and neurites is the hallmark of Parkinson's disease (PD). A growing number of studies highlights a critical interplay between lipid metabolism and αS biology. Some of these works postulate a physical interaction between αS and lipid droplets (LDs), but further clarity is needed, not least because typically exogenous αS and/or heterologous systems have been studied. Here, we investigated the effects of acute LD accumulation on endogenous wild-type αS in primary rat cortical neurons. To induce robust LD accumulation within hours, we inhibited the neuronal triacylglycerol hydrolase DDHD2, a phospholipase, using the compound KLH45. KLH45-induced LD accumulation did not affect total levels, phosphoserine-129 status, or solubility of αS, and no co-localization between LDs and αS was observed under these conditions. These findings suggest that a "second hit" and/or a specific LD lipid composition may be necessary for lipid excess to affect αS homeostasis. Our work thus contributes to the debate on αS structure and lipid interaction.

Alpha-synuclein (αSyn) is an intrinsically disordered protein that accumulates in the brains of patients with Parkinson's disease (PD). Through a high-throughput screen, we recently identified 38 genes whose knockdown modulates αSyn propagation. Here, we show that, among those, TAX1BP1 regulates how αSyn interacts with lipids, and ADAMTS19 modulates how αSyn phase separates into inclusions, adding to the growing body of evidence implicating those processes in PD. Through RNA sequencing, we identify several genes that are differentially expressed after knockdown of TAX1BP1 or ADAMTS19 and carry an increased frequency of rare risk variants in patients with PD versus healthy controls. Those differentially expressed genes cluster within modules in regions of the brain that develop high degrees of αSyn pathology. We propose a model for the genetic architecture of sporadic PD: increased burden of risk variants across genetic networks dysregulates pathways underlying αSyn homeostasis and leads to pathology and neurodegeneration.

Mutations and multiplications in the SNCA gene, encoding alpha-synuclein (aSyn), are associated with familial forms of Parkinson's disease (PD). We report the identification of a novel SNCA missense mutation (NM_000345.4, cDNA 174G>C; protein K58N) in a PD patient using whole exome sequencing, and describe comprehensive molecular and cellular analysss of the effects of this novel mutation. The patient exhibited typical sporadic PD with early onset and a benign disease course. Biophysical studies revealed that the K58N substitution causes local structural effects, disrupts binding to membranes, and enhances aSyn in vitro aggregation. K58N aSyn produces fewer inclusions per cell, and fails to undergo condensate formation. The mutation increases the cytoplasmic distribution of the protein, and has minimal effect on the dynamic reversibility of serine-129 phosphorylation. In total, the identification of this novel mutation advances our understanding of aSyn biology and pathobiology.

INTRODUCTION: Early episodic memory impairment in Alzheimer's disease (AD) is linked to synaptic dysfunction from amyloid β-protein oligomers (oAβ), particularly affecting the dentate gyrus mossy fiber-CA3 pathway. The APPNL-G-F mouse model exhibits early deficits in mossy fiber long-term potentiation (mf-LTP).

METHODS: We administered the β-adrenergic receptor agonist isoproterenol (ISO) in vivo and phosphodiesterase type 4 inhibitor GSK356278 in vitro to assess their impact on mf-LTP and contextual fear memory. Fluorescence lifetime imaging (FLIM)-Förster resonance energy transfer (FRET) microscopy was used to visualize impaired and rescued cyclic adenosine monophosphate (cAMP) signaling in dentate gyrus neurons.

RESULTS: ISO prevented mf-LTP impairment at 3-4 mo and improved memory by 7 mo. GSK356278 inhibited mf-LTP deficits in a dose-dependent manner. ISO also reduced hyperphosphorylation of synapsin I and microgliosis.

DISCUSSION: These findings suggest that β-AR activation and phosphodiesterase 4 (PDE4) inhibition mitigate oAβ-induced memory deficits, supporting enhanced cAMP signaling as a therapeutic target for early AD.

HIGHLIGHTS: Early episodic memory deficits in AD linked to oAβ-induced synaptic dysfunction. Isoproterenol and GSK356278 improve mossy fiber-LTP and fear memory deficits. FLIM-FRET shows treatments restore cAMP signaling in dentate gyrus neurons. Isoproterenol reduces synapsin I hyperphosphorylation and microgliosis. Enhancing cAMP signaling may help mitigate early memory deficits in AD.

BACKGROUND: Diffusible Aβ oligomers (oAβ) confer cytotoxicity in Alzheimer's disease. The dynamic complexity of this hydrophobic analyte means few immunoassays exist to quantify oAβ in CSF and plasma.

METHODS: We characterized antibody 71A1 to a cyclized dimer of Aβ9-18 for oAβ preference over monomers by surface plasmon resonance. We improved an earlier bead-based immunoassay by using 71A1 streptavidin plates for capture and N-terminal antibody 3D6 for detection. Numerous controls systematically validated accuracy.

RESULTS: 71A1 showed highly selective binding kinetics to Aβ oligomers over monomers. It enriched bioactive oligomers from AD brain that altered neuronal excitatory currents and calcium transients. 71A1/3D6 immunoassay exhibited specificity and reproducibility in human biofluids. CSF oAβ levels correlated positively with CSF tau and phosphorylated-tau-181. APP and PS1 FAD mutations increased oAβ levels in human neuronal media.

CONCLUSIONS: CSF oAβ levels rise in concert with rising tau levels. A new plate-based ELISA offers improved consistency, less sample volume, and lower cost, thus better suited to quantify this challenging analyte.

BACKGROUND: Parkinson's disease (PD) is a complex multifactorial disorder with a genetic component in about 15% of cases. Multiplications and point mutations in SNCA gene, encoding α-synuclein (aSyn), are linked to rare familial forms of PD.

OBJECTIVE: Our goal was to assess the clinical presentation and the biological effects of a novel K58N aSyn mutation identified in a patient with PD.

METHODS: We describe the clinical presentation associated with the novel mutation, together with genetic testing through whole exome sequencing (WES). Furthermore, we conducted extensive biophysical and cellular assays to assess the functional consequences of this novel variant.

RESULTS: The patient exhibited typical features of sporadic PD with early onset and a benign disease course. WES showed a novel heterozygous missense variant in SNCA (NM_000345.4, c.174G>C; p.K58N). A positive family history of PD was evident, because both a parent and a grandparent had been diagnosed with PD but were deceased. The patient underwent deep brain stimulation surgery 13 years postdiagnosis, showing stable, long-term improvements in motor symptoms. Biophysical studies demonstrated K58N substitution causes local structural effects, disrupts membrane binding, and enhances aSyn in vitro aggregation. In cellular systems, K58N aSyn produces fewer inclusions per cell and does not form condensates. The variant increases aSyn cytoplasmic distribution and displays aberrant activity-dependent dynamic serine-129 phosphorylation.

CONCLUSIONS: The clinical presentation associated with the novel K58N aSyn mutation suggests a relatively benign PD course consistent with the phenotypic spectrum of idiopathic PD. Overall, our molecular studies provide novel insight into the biology and pathobiology of aSyn. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.