# APP Deficiency Ameliorates FAD Presenilin 1 F105C and A246E Mutations-induced Mitochondrial Dysfunction in Human Cortical Neurons

## TL;DR

Reducing APP levels helps fix mitochondrial problems caused by FAD-linked PS1 mutations in human brain cells.

## Contribution

The study shows APP deficiency can alleviate PS1 mutation-induced mitochondrial dysfunction in human cortical neurons.

## Key findings

- Mitochondrial dysfunction is a key pathway altered in sporadic AD cortex.
- APP knockout reduces mitochondrial defects and AD-related phenotypes in PS1 mutant neurons.
- Findings highlight APP's role in linking PS1 mutations to mitochondrial dysfunction in AD.

## Abstract

Mitochondrial dysfunction is widely regarded as a central and early feature of Alzheimer's disease (AD) pathology. Prior studies suggest that the accumulation of amyloid precursor protein (APP) within mitochondria contributes to this dysfunction. Mutations in presenilin-1 (PS1), which account for most cases of early-onset familial AD (FAD), have also been shown to impair mitochondrial function. In this study, we investigated how APP influences PS1 mutation-induced mitochondrial dysfunction in human cortical neurons derived from patient induced pluripotent stem cells (iPSCs).

We analyzed transcriptomic and proteomic datasets from postmortem sporadic AD cortex to identify key dysregulated pathways. To functionally interrogate selected mechanisms, we established a panel of CRISPR/Cas9-engineered human iPSC lines, including PS1 mutant lines (PS1+/F105C and PS1+/A246E), an APP knockout derivative (APP-/-_PS1+/F105C), and their isogenic wild-type controls. These iPSCs were differentiated into cortical neurons for functional studies. Following directed differentiation into cortical neurons, biochemical analyses and super-resolution imaging were conducted to evaluate mitochondrial and neuronal phenotypes.

Analyses of sporadic AD cortical transcriptomes and proteomes identified mitochondrial dysfunction as a prominently altered pathway. In agreement, cortical neurons differentiated from FAD PS1 mutant (F105C and A246E) iPSCs displayed mitochondrial defects and AD-related phenotypes, both of which were mitigated by APP knockout.

These findings provide critical insights into the bridging role of APP in FAD PS1 mutant-mediated mitochondrial dysfunction, advancing our understanding of the cellular mechanisms underlying AD.