CHIP patient blood is a mixture of normal and mutated cells. Genotyping mutations (@AnnaEnim@landau_lab) is difficult in peripheral blood because DNMT3A and TET2 are not well expressed.
Utilizing mitochondrial DNA SNPs, pioneered by @vangalenlab, @CalebLareau and @bloodgenes, we were able to identify genomic mutational status at the individual cell level
We confirmed the link between CHIP mutation & mitochondrial mutation using two methods: clonal expansion and @MissionBio Tapestri platform
This enabled previously impossible comparisons between mutated and wildtype cells from the same person, solving several riddles:
How does such a small fraction of blood cause significant heart disease? We find that most CD14+ monocytes in patients with large CHIP clones are mutated.
Why do different CHIP genes confer different disease risk? In CD14+ monos, the TET2 mutant cells are highly inflammatory compared to non-mutated cells from the same patient... but not in DNMT3A
Further, macrophage migration inhibitory factor (MIF) was found to be upregulated in TET2 but not DNMT3A, a finding that was supported by human genetics data from the UKB.
Finally, we used phospo-specific flow cytometry to demonstrate the cell-intrinsic nature of TET2 mutated CD14 monocytes in response to IL-6 stimulation.
In summary, we find mutation-specific patterns in RNA expression across CD14 monos in TET2 and DNMT3A patients which could explain divergent risk profiles in CHIP and identify new therapeutic targets in TET2 CHIP.