A dominant 59.6kD band and faint 87.6kD band for both the Hela wild type and knock out lysates were observed (3ug/ml PSEN1) vs the predicted size of 52.7kD. The molecular weight discrepancy could be due a post-translationally modified form of the target protein, a splice-variant form of the target protein, or an unrelated protein which shares the antibody-reactive epitope. The presence of bands in the knock out lysates suggest incomplete knockout of the target gene.