Features of F9 nonsense mutations selected for recombinant expression. (A) Features of HB-causing nonsense mutations listed according to the number of patients and type of nonsense triplet. The induced-readthrough score, ranging from 0 (unfavorable sequence) to 10 (highly favorable) was adapted from in vitro studies on G418-induced readthrough by Manuvakhova et al.14 (B) Schematic representation of FIX organization and relative position of nonsense mutations (top) and of predicted missense changes arising from readthrough (bottom). Rectangles highlight the most readthrough-responsive PTCs in our in vitro expression platform. The sequence alignments of the selected amino acid positions among the homologous FIX (NP_000124.1), FVII (NP_000122.1), FX (NP_000495.1), and protein C (NP_000303.1) are indicated below the corresponding missense variants. The asterisk indicates that readthrough over the W240X(TGAC) is expected to reinsert the authentic residue (tryptophan). The catalytic triad residues (black circles) are also numbered. EGF, epidermal growth factor–like domain.
