Biology subjects

Aldridge, G.

Publications and source records attributed to Aldridge, G..

3 recordsLinked to original sources

bioRxiv2023

Enhanced spine stability and survival lead to increases in dendritic spine density as an early response to local alpha-synuclein overexpression in mouse prefrontal cortex

Lewy Body Dementias (LBD), including Parkinsons disease dementia and Dementia with Lewy Bodies, are characterized by widespread accumulation of intracellular alpha-Synuclein protein deposits in regions beyond the brainstem, including in the cortex. Patients with LBDs develop cognitive changes, including abnormalities in executive function, attention, hallucinations, slowed processing, and cognitive fluctuations. The causes of these non-motor symptoms remain unclear; however, accumulation of alpha-Synuclein aggregates in the cortex and subsequent interference of synaptic and cellular function could contribute to psychiatric and cognitive symptoms. It is unknown how the cortex responds to local pathology in the absence of significant secondary effects of alpha-Synuclein pathology in the brainstem. To investigate this, we employed viral overexpression of human alpha-Synuclein protein targeting the mouse prefrontal cortex (PFC). We then used in vivo 2-photon microscopy to image awake head-fixed mice via an implanted chronic cranial window to assess the early consequences of alpha-Synuclein overexpression in the weeks following overexpression. We imaged apical tufts of Layer V pyramidal neurons in the PFC of Thy1-YFP transgenic mice at 1-week intervals from 1-2 weeks before and 9 weeks following viral overexpression, allowing analysis of dynamic changes in dendritic spines. We found an increase in the relative dendritic spine density following local overexpression of alpha-Synuclein, beginning at 5 weeks post-injection, and persisting for the remainder of the study. We found that alpha-Synuclein overexpression led to an increased percentage and longevity of newly-persistent spines, without significant changes in the total density of newly formed or eliminated spines. A follow up study utilizing confocal microscopy revealed that the increased spine density is found in cortical cells within the alpha-Synuclein injection site, but negative for alpha-Synuclein phosphorylation at Serine-129, highlighting the potential for effects of dose and local circuits on spine survival. These findings have important implications for the physiological role and early pathological stages of alpha-Synuclein in the cortex.

neuroscience↗

bioRxiv2023

Mice expressing A53T / A30P mutant alpha-synuclein in dopamine neurons do not display behavioral deficits

Alpha-synuclein has been implicated in neurodegenerative diseases such as Parkinsons disease and Dementia with Lewy bodies, with A53T and A30P mutations shown to be disease-causing. It has been reported that transgenic mice with tyrosine hydroxylase promotor-driven expression of A53T / A30P mutant alpha-synuclein in dopamine neurons provide a useful preclinical model of these conditions by virtue of developing dopaminergic neuronal cell death and related behavioral deficits. Here, we report a lack of replication of this finding. Despite detecting robust overexpression of A53T / A30P mutant alpha-synuclein in dopamine neurons, we observed neither cell death or related behavioral deficits in these mice. Our results demonstrate that preclinical models of synucleinopathy need careful validation in the field.

animal behavior and cognition↗

bioRxiv2021

Cortical alpha-synuclein preformed fibrils do not affect interval timing in mice

One hallmark feature of Parkinsons disease (PD) is Lewy body pathology associated with misfolded alpha-synuclein. Previous studies have shown that striatal injection of alpha-synuclein preformed fibrils (PFF) can induce misfolding and aggregation of native alpha-synuclein in a prion-like manner, leading to cell death and motor dysfunction in mouse models. Here, we tested whether alpha-synuclein PFFs injected into the medial prefrontal cortex results in cognitive deficits in mouse models as measured by interval timing, which is reliably disrupted in PD patients and in rodent models. We injected human alpha-synuclein PFF or monomers in the medial prefrontal cortex pre-injected with adeno-associated virus (AAV) overexpressing human alpha-synuclein. Despite notable medial prefrontal cortical synucleinopathy, we did not observe consistent deficits in fixed-interval timing. These results suggest that cortical alpha-synuclein does not reliably disrupt interval timing in rodent models. HighlightsCortical injection of alpha-synuclein preformed fibrils (PFF) induces diffuse synucleinopathy Cortical injection of PFFs does not affect interval timing in mice Medial prefrontal cortical synucleinopathy does not reliably disrupt interval timing

neuroscience↗