Sequence of thyroxine-binding globulin gene in a Korean family with complete TBG deficiency

Genomic DNAs from an 11 year-old boy with suspected complete thyroxine-binding globulin deficiency (TBG-CD) and a normal individual were subjected to polymerase chain reactions and sequenced. The entire coding region and exon/intron boundary of TBG gene from a normal individual showed no base change in exons as reported, However, sequence of the TBG gene from the suspected individual revealed a single nucleotide deletion at codon 352 in axon 4. The mutation was further confirmed by allele-specific amplification of genomic DNAs from the affected hemizygous boy, a hemizygous normal male, and the heterozygous boy's mother with primers containing 3' end nucleotide missing in TBG-CD or normal sequence. Several distinct mutations in the coding regions of the TBG gene have been shown to be associated with TBG-CD. The Korean type identified in this study was found to be the same mutation type of TBG-CD in Japanese, In addition, we identified 3 more base changes in introns both in normal and TBG-CD subjects.