Enhanced neurite outgrowth and branching precede increased amyloid-β-induced neuronal apoptosis in a novel Alzheimer's disease model

Though it is widely accepted that amyloid-β (Aβ) is a key factor in Alzheimer's disease (AD) pathology, its underlying mechanism remains unclear. In order to study the association between Aβ and neural circuitry dysfunction, we developed a primary culture preparation derived from the nervous system of transgenic Drosophila melanogaster larvae expressing human Aβ_1-42 (Aβ₄₂). Cultured neurons undergo a consistent developmental process, culminating in an elaborate neuronal network with distinct functional and morphological characteristics. Throughout this development, a time-dependent increase in intracellular expression levels of Aβ₄₂ was detected, followed by extracellular staining at a later time point. When compared to controls, Aβ₄₂ cultures exhibited enhanced levels of apoptosis, resulting in reduced cell viability. Moreover, as primary culture preparations enable high resolution monitoring of neuronal phenotypes, we were able to detect subtle morphological changes in neurons expressing Aβ₄₂, namely an enhancement in neurite outgrowth and arborization, which preceded the effect of neurodegeneration. Our results establish D. melanogaster primary neuronal cultures as a rapid, accessible and cost-effective platform for AD molecular studies and drug screening, and suggest a possible role for Aβ₄₂ in the organization of neuronal processes.