BACKGROUND: In late-onset Alzheimer's disease (LOAD), the causal mechanisms of synaptic dysfunction underlying memory deficits that lead to dementia remain unclear. Genetic studies of LOAD patients identified gene variants associated with AD. Now it is necessary to translate the genotype into the mechanism of synaptic dysfunction. Here we investigated the impact of the putative LOAD risk factor CD2AP loss of function. We hypothesized that CD2AP might regulate spinal actin since CD2AP is a regulator of actin dynamics in non-neuronal cells, and the actin cytoskeleton dynamics is essential for spine plasticity. METHOD: We have used wild-type mouse primary cortical neurons after differentiation for 15-21 DIV. To knockdown CD2AP, we infected primary neurons with lentivirus expressing GFP and shCD2AP or non-targeting shRNA as control. We used immunofluorescence microscopy, using epifluorescence and confocal microscopy, and quantitative morphologic and subcellular analysis using ICY and Imaris software to analyze CD2AP synaptic localization, synapses and spines density, as well as spinal F-actin. RESULT: We discovered that CD2AP is present in spines. CD2AP knockdown reduced spines density. In contrast, CD2AP overexpression increased spine density. Morphologically, CD2AP overexpression enlarged spine heads. Synapses density was, like spines, reduced by CD2AP knockdown. Mechanistically, we found that spinal F-actin decreased by CD2AP knockdown and increased upon CD2AP overexpression. CONCLUSION: These results indicate that CD2AP regulates spine morphology and thus synapses, likely by regulating actin dynamics at spines. Overall CD2AP variants may contribute to LOAD development by directly interfering with synapses.
|Journal||Alzheimer's & dementia : the journal of the Alzheimer's Association|
|Publication status||Published - 1 Dec 2021|