Figure 7. Co-knockdown of I_Kr and I_Na by hERG transcript-specific shRNA.

(A) Effects of hERG1a or hERG1b silencing on channel mRNA expression levels detected by RT-qPCR (mean ±95% CI) in iPSC-CMs. A non-targeting shRNA (scrambled shRNA) is used as a control. (B) Effects of specific hERG1a or hERG1b silencing on ion channel mRNAs expressed alone in HEK293 cells. (C) Representative family of traces show I_Kr in presence of control (upper) or hERG1b shRNA (lower). (D) Summary of steady-state current density vs. test potential shows effect of hERG1b shRNA (mean ±SE). (E) Effects of 1b shRNA on peak tail current vs. pre-pulse potential (mean ±SE). (F) Representative family of traces recorded from iPSC-CMs showing effects of hERG1b-specific shRNA compared to control shRNA on peak I_Na. (G) Summary current-voltage plot of peak I_Na vs. test potential (mean ±SE). (H) Summary conductance (G)-voltage plot based on data from G (mean ±SE). (I) Late sodium current representative trace in control and 1b shRNA-transfected cells, measured by applying a single pulse protocol of 800 ms. (J) Summary statistics of peak I_Na showed a decrease upon transfection with hERG1b shRNA (mean ±SE). (K) Late I_Na measured as the integral from 50 to 800 ms from the beginning of the pulse showed a decrease upon transfection with hERG1b shRNA (mean ±SE).

Figure 7—figure supplement 1. Co-knockdown of hERG and SCN5A mRNAs by hERG transcript-specific shRNA.

(A) Representative confocal images of smFISH for hERG1a and SCN5A transcripts in iPSC-CMs transfected with either a control or hERG1b shRNA. (B) Histogram of the average number of transcripts detected per cell for hERG1a or SCN5A transcripts in presence of hERG1b shRNA compared to a scrambled shRNA (mean ±SE). (C) Histogram of the mean number of hERG1a transcript colocalized with SCN5A transcript in cells silenced for hERG1b compared with control (mean ±SE).