The study identifies a genetic variant, rs17834140-T, that protects against clonal hematopoiesis (CH) and myeloproliferative malignancies by reducing the expression and function of the RNA-binding protein MSI2 in hematopoietic stem cells (HSCs).[1][2] Somatic mutations that increase HSC fitness lead to their expansion in CH and increase the risk of blood cancers. rs17834140-T variant is associated with a slower rate of CH expansion in humans and modifies the dominance of HSC clones with ASXL1 mutations in experimental models.[1][2] GWAS confirmed a protective association at the 17q22 locus, replicated in an independent study with three additional cohorts, where their major SNP was in high LD (R²=0.87) with rs80093687.[1] The rs17834140-T variant is in perfect LD (R²=1.0) with rs80093687 and acts through a reduction of the MSI2 enhancer, reducing the fitness of human HSCs.1][1] Modeling of the variant's effects in primary human hematopoietic cells revealed an MSI2-regulated RNA network important for HSC maintenance and resistance to CH.[1][2] The findings support inhibition of MSI2 or its targets as a strategy for preventing blood cancers.[1][2] The findings also support inhibition of MSI2 or its targets as a strategy for preventing blood cancers.