On May 24, 2021, Assistant Professor Ruilin Tian from the School of Medicine at the Southern University of Science and Technology (SUSTech), Martin Kampmann from the University of California, San Francisco (UCSF), and others published a paper entitled “Genome-wide CRISPRi/a screens in human neurons link lysosomal failure to ferroptosis” in Nature Neuroscience. Their research systematically explored the mechanism by which human neurons regulate ROS levels and respond to oxidative stress and discovered a neuron-specific ferroptosis pathway.

As the longest-living cells in the body, neurons are challenged by various cellular stresses during aging, of which oxidative stress is a major one. Oxidative stress is caused by the excessive accumulation of reactive oxygen species (ROS) in cells. Excessive ROS can cause damages to DNA, proteins, and lipids, leading to cell death. The brain is particularly sensitive to ROS because it consumes a lot of oxygen and contains a large number of metals with high redox activity (such as iron and copper) and polyunsaturated fatty acids that are susceptible to oxidative damage, while the amount of antioxidants in the brain is relatively limited.

Oxidative stress is implicated in neurodegenerative diseases. Clinically, the brain of patients with neurodegenerative diseases has higher ROS levels and oxidative damages. In vitro studies using induced pluripotent stem cell models have also confirmed that neurons carrying genetic mutations in neurodegenerative diseases are more sensitive to oxidative stress.

In this paper, the authors conducted multiple large-scale CRISPRi/a screens in human neurons derived from induced pluripotent stem cells (iPSC) to uncover genes regulating oxidative stress response in human neurons (Figure 1). Surprisingly, they identified PSAP, a gene encoding the lysosomal protein prosaposin, as a key ROS regulator in neurons, and loss of PSAP can lead to neuronal ferroptosis (Figure 2).

Figure 1. Genome-wide CRISPR screens in human neurons

Figure 2. Loss of PSAP leads to neuronal ferroptosis

Through in-depth mechanistic studies, they elucidated that loss of PSAP leads to glycosphingolipids accumulation in lysosomes and lipofuscin formation, which traps iron, generating reactive oxygen species and triggering ferroptosis (Figure3). They also determined transcriptomic changes in neurons after perturbation of genes linked to neurodegenerative diseases. To enable the systematic comparison of gene function across different human cell types, they established a data commons named CRISPRbrain that allows researchers to explore gene functions in different cell types (Figure 4).

Figure 3. Mechanism of ferroptosis caused by the loss of PSAP

Figure 4. CRISPRbrain data commons

Assistant Professor Ruilin Tian at SUSTech is the first and co-corresponding author of this paper.

Paper link: https://doi.org/10.1038/s41593-021-00862-0