We sorted young (CD62Lhi) and senescent (CD62Llow) neutrophils from β-actin-DsRed MPN mice and co-cultured them with megakaryocytes genetically labelled with enhanced green fluorescent protein expressed under the regulatory elements of Von Willebrand factor (VWF-eGFP mice)44 (supplemental Figure 4E). The gene discussed is ACTB; the disease is myeloproliferative disorder.