○ shRNA of both SMC1A and STAG2 caused enlarged spleen, myeloid hyperplasia, lymphopenia.○ Differentiation into erythroid and lymphoid lineages affected. Self-renewal increased.○ No chromosomal instability○ Altered GATA1 motif accessibility after shRNA-STAG2 in HSPC.○ Splenic morphology, bone marrow hyperplasia seen in shRNA-SMC1A mice. Myeloid lineage cells found in high numbers. The gene discussed is STAG2; the disease is lymphopenia.