Eddarkaoui, S. | bioRxiv Science

bioRxiv2021

Functional analyses of two novel LRRK2 pathogenic variants in familial Parkinson's disease

BackgroundPathogenic variants in the LRRK2 gene are a common monogenic cause of Parkinsons disease. However, only seven variants have been confirmed to be pathogenic. ObjectivesWe identified two novel LRRK2 variants (H230R and A1440P) and performed functional testing. MethodsWe transiently expressed wildtype, the two new variants, or two known pathogenic mutants (G2019S and R1441G), in HEK-293T cells, with or without LRRK2 kinase inhibitor treatment. We characterized the phosphorylation and kinase activity of the mutants by western blotting. Thermal shift assays were performed to determine the folding and stability of the LRRK2 proteins. ResultsThe two variants were found in two large families and segregate with the disease. They display altered LRRK2 phosphorylation and kinase activity. ConclusionsWe identified two novel LRRK2 variants which segregate with the disease. The results of functional testing lead us to propose these two variants as novel causative mutations for familial Parkinsons disease.

genetics↗

bioRxiv2021

Alzheimer's brain inoculation in Aβ-plaque bearing mice: synaptic loss is linked to tau seeding and low microglial activity

Alzheimers disease (AD) is characterized by intracerebral accumulations of extracellular amyloid-{beta} (A{beta}) plaques and intracellular tau pathology that spread in the brain. Tau lesions occur in the form of neuropil threads, neurofibrillary tangles, and neuritic plaques i.e. tau aggregates within neurites surrounding A{beta} deposits. The cascade of events linking these lesions and synaptic or memory impairments are still debated. Intracerebral infusion of human AD brain extracts in A{beta} plaque-bearing mice that do not overexpress pathological tau proteins induces tau pathologies following heterotopic seeding of mouse tau protein. There is however little information regarding the downstream events including synaptic or cognitive repercussions of tau pathology induction in these models. In the current study, human AD brain extracts (ADbe) and control-brain extracts (Ctrlbe) were infused in the hippocampus of A{beta} plaque-bearing APPswe/PS1dE9 mice. Memory, synaptic density, as well as A{beta} plaque and tau aggregate loads, microgliosis, astrogliosis at the inoculation site and in connected regions (perirhinal/entorhinal cortex) were evaluated 4 and 8 months post-inoculation. ADbe inoculation induced memory deficit. It increased deposition of A{beta} plaques close to the inoculation site. Tau pathology was also induced in ADbe-inoculated mice. Neuropil threads and neurofibrillary tangles occurred next to the inoculation site and spread to connected regions notably the perirhinal/entorhinal cortex. Neuritic plaque pathology was detected in both ADbe- and Ctrlbe- inoculated animals but ADbe inoculation increased the severity close and at distance of the inoculation site. Finally, ADbe inoculation reduced synaptic density close to the inoculation site and in connected regions as the perirhinal/entorhinal cortex. Synaptic impairments were correlated with increased severity of neuritic plaques but not of other tau lesions or A{beta} lesions, which suggests that neuritic plaques are a culprit for synaptic loss. Synaptic density was also associated with microglial load. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=182 HEIGHT=200 SRC="FIGDIR/small/438654v4_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@791f29org.highwire.dtl.DTLVardef@1ecf87corg.highwire.dtl.DTLVardef@adb3a0org.highwire.dtl.DTLVardef@1ebef93_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2021

A β-secretase modulator decreases Tau pathology and preserves short-term memory in a mouse model of neurofibrillary degeneration

A structure-activity relationship has enabled us to identify two molecules, MAGS02-14 and PEL24-199, sharing a {beta}-secretase modulatory effect but having or not a lysosomotropic activity, respectively. More importantly, MAGS02-14 and PEL24-199 only differ from each other by a single nitrogen atom. However, which of the lysosomotropic and/or {beta}-secretase modulating activities is necessary for the pharmacological effect in vivo remains ill-defined. To address this question, the THY-Tau22 transgenic model of NFD was treated for 6 weeks in a curative paradigm and short-term memory, Tau burden, and inflammatory processes were studied. PEL24-199, possessing only the {beta}-secretase modulatory activity, was shown to restore the short-term memory and to reduce NFD. This effect was associated with reduced phosphorylation of Tau, increased phosphatase expression, and a decrease of astrogliosis. Our results therefore suggest that the lysosomotropic activity may be dispensable for the effect on both A{beta} and Tau pathologies.

pharmacology and toxicology↗