Altered striatal dopamine levels in Parkinson’s disease VPS35 D620N mutant transgenic aged mice

Abstract

Vacuolar protein sorting 35 (VPS35) is a major component of the retromer complex that mediates the retrograde transport of cargo proteins from endosomes to the trans-Golgi network. Mutations such as D620N in the VPS35 gene have been identified in patients with autosomal dominant Parkinson’s disease (PD). However, it remains poorly understood whether and how VPS35 deficiency or mutation contributes to PD pathogenesis; specifically, the studies that have examined VPS35 thus far have differed in results and methodologies. We generated a VPS35 D620N mouse model using a Rosa26-based transgene expression platform to allow expression in a spatial manner, so as to better address these discrepancies. Here, aged (20-months-old) mice were first subjected to behavioral tests. Subsequently, DAB staining analysis of substantia nigra (SN) dopaminergic neurons with the marker for tyrosine hydroxylase (TH) was performed. Next, HPLC was used to determine dopamine levels, along with levels of its two metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in the striatum. Western blotting was also performed to study the levels of key proteins associated with PD. Lastly, autoradiography (ARG) evaluation of [3H]FE-PE2I binding to the striatal dopamine transporter DAT was carried out. We found that VPS35 D620N Tg mice displayed a significantly higher dopamine level than NTg counterparts. All results were then compared with that of current VPS35 studies to shed light on the disease pathogenesis. Our model allows future studies to explicitly control spatial expression of the transgene which would generate a more reliable PD phenotype.

VPS35, the core component of the retromer complex, and Parkinson's disease

“…Vanan et al used a Rosa26‐based transgene expression platform to generate a VPS35 D620N mouse model. The study found that the dopamine level of VPS35 D620N mice was significantly higher than that of nontransgenic control mice 41 …”

“…The study found that the dopamine level of VPS35 D620N mice was significantly higher than that of nontransgenic control mice. 41 F I G U R E 1 Cellular processes affected by the VPS35 mutation. VPS35, which is the core component of the retromer, along with VPS26 and VPS29, sits at the endosomal membrane and recognizes cargo to be sorted.…”

Neuroprotective potential of Mentha piperita extract prevents motor dysfunctions in mouse model of Parkinson’s disease through anti-oxidant capacities

“…The mixture of mobile phase was 0.01% EDTA (adjusted to pH 4.0, 100% acetic acid), 2% methanol (v/v), and 7% acetonitrile (v/v). All solutions for HPLC analysis were double filtered through 0.2 μm membranes and degassed before use as described previously [ 34 ]. The flow rate of mobile phase was 0.8 ml per minute and UV detector was set at 340 nm.…”

“…The flow rate of mobile phase was 0.8 ml per minute and UV detector was set at 340 nm. The final dopamine level was represented as μg/mg of brain tissue [ 34 ].…”

Beware of Misdelivery: Multifaceted Role of Retromer Transport in Neurodegenerative Diseases

“…Based on these results, genetically engineered animal models harboring D620N VPS35 have been created, and they have variable phenotypes. In a viral-mediated gene transfer rat model, the expression of human D620N VPS35 in the SNpc resulted in prominent dopaminergic neuron loss with axonal pathology, whereas D620N VPS35 Tg aged mice generated via Rosa26-based transgenesis did not exhibit apparent motor impairment or neurodegeneration (Tsika et al, 2014;Vanan et al, 2020). On the contrary, Tg flies expressing human D620N VPS35 or P316S VPS35 displayed a detrimental phenotype including dopaminergic neuron loss, locomotor dysfunction, a shortened lifespan, and susceptibility toward PD-linked environmental toxins (Wang et al, 2014).…”