PMC4911217_01
PMC4911217_02
Pedigrees for families 1 and 2. a The affected proband (III:6), her affected brother (III:7) and mother (II:3), her two affected aunts (II:1 and II:2), and her four affected cousins (III:1, III:2, III:4, III:5) are shown along with their p.I314T variant status. b In family 2, the affected proband (II:1), his two unaffected parents (I:1 and I:2), and sibling (II:2) are shown along with the de novo variant p.T226R present in the proband. The square represents a male individual, a circle represents a female individual, and the arrow indicates the probands. Filled symbols represent clinically affected individuals
nihms793785f1.jpg
PMC4911217_02_nihms793785f1.jpg
F1
Sanger sequencing confirmed that all affected members of the family (except III:1 who did not enroll) carried the variant, while the only unaffected family member (III:3) did not carry it (Fig. 1a). This SNP has been previously clinically associated with EA1 (Fig. 1b).
Molecular modeling of KCNA1 (KV1.1) variants. a Molecular structure of rat KCNA2 (KV1.2) (PDB code: 3LUT), a protein very similar to KCNA1, and for which crystal structure is available. The structural modeling and illustration were prepared by the software PyMOL (The PyMOL Molecular Graphics System, Version 1.7.4 Schrodinger, LLC). The channel forms a tetramer, with Thr226 residue in red and Ile314 colored in purple (marked by arrows). b, c WT Thr226 residue (b) and variant Thr226Arg (c) modeling. c The variant Thr226Arg conflicts with a Phe residue on the same helix (marked by arrow) and likely affects the hydrophobic packing with another helix through the interaction with the aromatic residues. d, e WT Ile314 residue (d) and variant Ile314Thr (e) modeling. e The variant Ile314Thr likely disrupts the hydrophobic packing between two transmembrane helices (marked by arrow)
nihms793785f2.jpg
PMC4911217_02_nihms793785f2.jpg
F2
Molecular modeling was performed for both protein variants as shown in Fig. 2. The wild-type KCNA1 and the location of both the variants are shown in Fig. 2a. Thr226Arg variant present in family 2 conflicted with a Phe residue on the same helix likely affecting the hydrophobic packing with another helix through interaction with the aromatic residues (Fig. 2b, c). The variant Ile314Thr present in family 1 likely disrupts the hydrophobic packing between two transmembrane helices (Fig. 2d, e).