The deletion of Stat3 leads to a decrease in the percentage of long-term marrow repopulating hematopoietic stem cells (LT-HSCs) along with dysregulated mitochondrial function, contributing to a shortened lifespan and a blood phenotype with similarities to the human diseases myelodysplastic syndrome and myeloproliferative neoplasms 10, implying that mitochondrial STAT3 could impair HSC development. The gene discussed is STAT3; the disease is myelodysplastic syndrome.