Characterization of a maintainable human myeloid model of VEXAS syndrome with enhanced TNF-induced cell death and DAMP release
Background: VEXAS syndrome is an adult-onset autoinflammatory disorder caused by somatic UBA1 mutations. UBA1-mutated myeloid cells have been reported to exhibit increased susceptibility to inflammatory cell death; however, the mechanisms underlying this phenotype and the extracellular consequences of enhanced cell death remain incompletely understood. Methods: Disease-associated UBA1 M41…
VEXAS syndrome is an autoinflammatory disorder brought on by UBA1 genetic mutations. Myeloid cells from patients with this condition are observed to be more vulnerable to inflammatory cell death. However, the mechanisms behind this enhanced susceptibility and the extracellular effects of heightened cell death are not entirely clear.
Scientists introduced a UBA1 M41 mutation into human myeloid U937 cells using a technique called CRISPR/Cas9 genome editing. These edited cells were then compared to normal cells through a variety of tests, with a focus on the cellular changes caused by the mutation, cell death pathways, and the release of certain molecules into the surrounding environment.
The edited cells not only maintained their viability under normal culture conditions but also displayed characteristics similar to those seen in patients with VEXAS syndrome. Sequencing of the cells showed that one copy of the UBA1 gene had the intended M41 mutation, while the other copy had a deletion caused by the CRISPR/Cas9 editing process.
The cells harbored reduced levels of UBA1b and higher amounts of UBA1c protein, had visible clumps of cellular material within them, showed reduced ability to multiply, and were more prone to dying in general.
Likewise, these mutated cells were found to be more susceptible to dying when exposed to a particular inflammatory protein called TNF. This death could occur through two different pathways: apoptosis or necroptosis. The scientists discovered that two proteins, RIPK1, RIPK3, and MLKL, were present at higher levels in the mutated cells. When the activity of these proteins was blocked, it reduced the extent of cell death in response to TNF exposure.
Furthermore, the edited cells released larger amounts of certain molecules into the surrounding fluid compared to normal cells. These molecules, known as damage-associated molecular patterns (DAMPs), include ATP, HMGB1, and S100A8/A9. The findings of this study provide a better understanding of the cellular impacts of UBA1 dysfunction and establish a reliable experimental setup for further research into the underlying mechanisms of VEXAS syndrome.
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