Dopaminergic neurons of the substantia nigra exist in a persistent state of vulnerability resulting from high baseline oxidative stress, high energy demand, and broad unmyelinated axonal arborizations. Impairments in the storage of dopamine compound this stress due to cytosolic reactions that transform the vital neurotransmitter into an endogenous neurotoxicant, and this toxicity is thought to contribute to the dopamine neuron degeneration that occurs Parkinson’s disease. We have previously identified synaptic vesicle glycoprotein 2C (SV2C) as a modifier of vesicular dopamine function, demonstrating that genetic ablation of SV2C in mice results in decreased dopamine content and evoked dopamine release in the striatum. Here, we adapted a previously published in vitro assay utilizing false fluorescent neurotransmitter 206 (FFN206) to visualize how SV2C regulates vesicular dopamine dynamics and determined that SV2C promotes the uptake and retention of FFN206 within vesicles. In addition, we present data indicating that SV2C enhances the retention of dopamine in the vesicular compartment with radiolabeled dopamine in vesicles isolated from immortalized cells and from mouse brain. Further, we demonstrate that SV2C enhances the ability of vesicles to store the neurotoxicant 1-methyl-4-phenylpyridinium (MPP+) and that genetic ablation of SV2C results in enhanced 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced vulnerability in mice. Together, these findings suggest that SV2C functions to enhance vesicular storage of dopamine and neurotoxicants, and helps maintain the integrity of dopaminergic neurons.

Numerous methods for evaluation of global fibrinolytic activity in whole blood or plasma have been proposed, with the majority based on tissue-type plasminogen activator (t-PA) addition to initiate fibrinolysis. We propose that such an approach is useful to reveal hypofibrinolysis, but t-PA concentrations should be kept to a minimum. In this paper, we describe a low-concentration t-PA plasma turbidity assay to evaluate several congenital factor deficiencies, including plasminogen activator inhibitor-1 (PAI-1) and plasminogen deficiency, as well as hemophilia A and B. In addition, we demonstrate a threshold dependency on endogenous PAI-1 levels. To assess endogenous hyperfibrinolysis, we suggest that assays that avoid t-PA addition are preferable, with assays based on euglobulin fractionation remaining a viable choice. We describe a euglobulin fraction clot lysis time (ECLT) assay with spectrophotometric readout and other modifications, and evaluate it as a tool to measure hyperfibrinolysis in inherited clotting factor deficiency states. We demonstrate that the ECLT is predominantly driven by residual amounts of PAI-1, t-PA, and α2-antiplasmin. These assays should be further evaluated for the detection of hypo- or hyperfibrinolysis in acquired thrombotic or hemorrhagic disorders.

The Joint Outcome Study (JOS), a randomized controlled trial, demonstrated that children with severe hemophilia A (HA) initiating prophylactic factor VIII (FVIII) prior to age 2.5 years had reduced joint damage at age 6 years compared with those treated with episodic FVIII for bleeding. The Joint Outcome Continuation Study (JOS-C) evaluated early vs delayed prophylaxis effects on long-term joint health, following JOS participants to age 18 years in an observational, partially retrospective study. Index joint magnetic resonance imaging (MRI) scores of osteochondral (OC) damage (primary outcome), joint physical examination scores, and annualized rates of joint/other bleeding episodes (secondary outcomes) were collected. Thirty-seven of 65 JOS participants enrolled in JOS-C, including 15 randomized to prophylaxis at mean age 1.3 years ("early prophylaxis"); 18 initially randomized to episodic treatment, starting "delayed prophylaxis"at mean age 7.5 years; and 4 with high-titer inhibitors. At JOS-C exit, MRI OC damage was found in 77% of those on delayed and 35% of those on early prophylaxis for an odds ratio of OC damage, in the delayed vs early prophylaxis group, of 6.3 (95% confidence interval, 1.3, 29.9; P 5 .02). Annualized bleeding rates were higher with delayed prophylaxis (mean plus or minus standard deviation, 10.6 6 6.6 vs 3.562.1; P<.001), including when only comparing time periods on prophylaxis (6.26 5.3 vs 3.3 6 1.9; P <.05). In severe HA, early initiation of prophylaxis provided continued protection against joint damage throughout childhood compared with delayed initiation, but early prophylaxis was not sufficient to fully prevent damage.

The synaptic vesicle glycoprotein 2C (SV2C) is an undercharacterized protein with enriched expression in phylogenetically old brain regions. Its precise role within the brain is unclear, though various lines of evidence suggest that SV2C is involved in the function of synaptic vesicles through the regulation of vesicular trafficking, calcium-induced exocytosis, or synaptotagmin function. SV2C has been linked to multiple neurological disorders, including Parkinson's disease and psychiatric conditions. SV2C is expressed in various cell types—primarily dopaminergic, GABAergic, and cholinergic cells. In mice, it is most highly expressed in nuclei within the basal ganglia, though it is unknown if this pattern of expression is consistent across species. Here, we use a custom SV2C-specific antiserum to describe localization within the brain of mouse, nonhuman primate, and human, including cell-type localization. We found that the immunoreactivity with this antiserum is consistent with previously-published antibodies, and confirmed localization of SV2C in the basal ganglia of rodent, rhesus macaque, and human. We observed strongest expression of SV2C in the substantia nigra, ventral tegmental area, dorsal striatum, pallidum, and nucleus accumbens of each species. Further, we demonstrate colocalization between SV2C and markers of dopaminergic, GABAergic, and cholinergic neurons within these brain regions. SV2C has been increasingly linked to dopamine and basal ganglia function. These antisera will be an important resource moving forward in our understanding of the role of SV2C in vesicle dynamics and neurological disease.