Mutations identified in theIGnT gene of adult i individuals.

(A) Mutations identified in the IGnTC gene of the adult i whites. IGnTC indicates the wild-type coding sequence of theIGnTC gene. ATG and TGA correspond to the respective translation start and stop codons. The mutant alleles identified in white subjects with the adult i phenotype, designatedIGnTC*505A and IGnTC*683A, possess 505G>A and 683G>A nucleotide substitutions, respectively, which predict the respective amino acid alterations of Ala169Thr and Arg228Gln. (B) Schematic representation of the mutations identified in theIGnT gene of adult i Taiwanese with congenital cataracts. The 2 G>A changes, identified, as reported previously, at the 1043 and 1148 nucleotide positions of the IGnTB gene, locate in the common exon 3 region of the 3 IGnT forms, and, thus, the 2 mutations also contribute to form the mutant IGnTA*1049A andIGnTC*1049A as well as IGnTA*1154A andIGnTC*1154A, respectively. Exons 1A and 1C possess 6 more coding nucleotides than the exon 1B does, and thus the nucleotide numbers of the same G>A changes in the IGnTA andIGnTC transcripts are different from those in theIGnTB transcripts. The Gly-to-Glu and Arg-to-His alterations resulting from the mutations in the encoded enzyme products are shown.