Overexpression of wild type or mutant <i>COL4A3</i> chains induces XBP1 splicing in AB8/13 cells.

<p>(a) Representative experiment of reverse transcription-PCR using XBP1 mRNA as template, from AB8/13 cells transiently expressing <i>COL4A3</i>-WT (A3/WT) or the mutant chains G1334E, G871C, G484R (<i>COL4A3</i>). PCR products were run on 3% agarose gel. It is apparent that over-expression of all chains induces XBP1 splicing, as evidenced by the appearance of the spliced band (s) when the PCR product is cut with the restriction enzyme Pst1. (h) hybrid, (u) unspliced (b) RT-PCR is quantified via densitometric analysis of the bands after PstI digestion as follows: ratio of the spliced band and the sum of the two PstI digest bands (s/(u1+u2), with PstI digestion. Hybrid band (h) was considered as equally contributing to unspliced and spliced bands. There is statistically significant XBP1 splicing when either WT or any of the mutant chains is overexpressed in AB8/13 cells. L19 was used as an internal PCR control. Data are means ± SEM of three independent experiments.