The B cell line Daudi was washed and resuspended in 1Â Hanks Balanced Salt Solution (HBSS) to a cell density of 2 Â 10 7 cells/ml. The neuronal cell line SK-N was trypsinized and resuspended in 1Â phosphate-buffered saline (PBS) with 2% FBS at a density of 10 7 cells/ml. Thee-hundred microliters of the Daudi cells or 500 ml of the SK-N cells were transfected with 10 mg of the alternative splicing minigene construct, the minigene construct with the ESE site deleted or mutated, the minigene construct plus SF2/ASF expression vector, or the ESE deleted construct plus SF2/ASF expression vector. Electroporation was performed with square waves of 700 V, 99 ms pulse length for four pulses for Daudi and square waves of 200 V, 70 ms pulse length for one pulse for SK-N using T820 ElectroSquarePorator (BTX). Both Daudi and SK-N cells were cultured in 5 ml of pre-warmed complete medium for 48 h before harvesting.