Fig 1: Blm was knocked down by siRNAs. a) 20 nM of each Blm siRNA was transfected into KY1.1. At 48 h after transfection, the Blm mRNA level was measured by quantitative RT-PCR using two primer sets. b) The expression level of Blm protein was determined by western blot. Blm is indicated by an arrowhead. As a control for Blm knockdown, the Blm conditional knockdown ESC line, Blmtet/tet [14], was used. Tubulin was used as an internal control for protein content. Si (–), no siRNA; siC-L, siRNA Negative Control Low Duplex; siC-M, Medium Duplex; Tet, Tetracycline c. Blm was knocked down by a mixture of siBlm-2 and siBlm-3 in KY1.1. This protocol was used for the gene targeting experiments. Blm expression was determined by quantitative RT-PCR (upper panel) and western blot (lower panel). All data are presented as the mean ± SE.