To determine the pathway responsible for activating MEF2C during lymphoid lineage specification, lineage negative (lin-) cells were treated with small molecule inhibitors targeting either p38 MAPK (SB203580, PubChem176155, or p38i) or ERK5 (U0216, PubChem3006531, or ERKi) (Fig 5A without viral infection). The gene discussed is MEF2C; the disease is viral infectious disease.