sentence: We chose three candidates ( CCAR1 , HNRNPDL and SRSF6 genes ) for RT-PCR validation , each with different modalities of AS-NMD : a ) skipping of exon 13 from CCAR1 mRNA which leads to a frameshift that triggers NMD b ) inclusion of exon 8 in the HNRNPDL mRNA introduces a PTC that induces NMD and c ) inclusion of exon 3 in the SRSF6 mRNA which introduces a PTC and induces NMD .