Resistance to inflammation underlies enhanced fitness in clonal hematopoiesis [II]

Clonal hematopoiesis (CH) results from enhanced fitness of a mutant hematopoietic stem and progenitor cell (HSPC), but how such clones expand is unclear. Here, we developed a technique that combines mosaic mutagenesis with color labeling of HSPCs to study how acquired mutations affect clonal fitness in a native environment. Mutations in CH-associated genes, like asxl1, promoted clonal dominance. Single-cell transcriptional analysis revealed that mutations stimulated expression of proinflammatory genes in mature myeloid cells and anti-inflammatory genes in progenitor cells of the mutant clone. Biallelic loss of one such immunomodulator, nr4a1, abrogated the ability of asxl1-mutant clones to establish clonal dominance. These results support a model where clonal fitness of mutant clones is driven by enhanced resistance to inflammatory signals from their mutant mature cell progeny. To analyze the effect of germline runx1 homozygous mutant hematopoiesis compared to runx1 heterozygous hematopoiesis. Embryos from runx1 heterozygous incross were grown to adulthood. Whole kidney marrow cells from 4 runx1 heterozygous and 4 runx1 homozygous mutant zebrafish were collected for preparation for 10x single cell RNA sequencing.