Supported in part by Grant NSC 94-2627-H-195-001 (ML) and Grant NSC 94-2320-B-002-088 (LCY) from the National Science Council, Taiwan.
A novel IGnT allele responsible for the adult i phenotype
Article first published online: 27 OCT 2006
Volume 46, Issue 11, pages 1982–1987, November 2006
How to Cite
Lin, M., Hou, M.-J. and Yu, L.-C. (2006), A novel IGnT allele responsible for the adult i phenotype. Transfusion, 46: 1982–1987. doi: 10.1111/j.1537-2995.2006.01006.x
- Issue published online: 27 OCT 2006
- Article first published online: 27 OCT 2006
- Received for publication December 22, 2005; revision received April 8, 2006, and accepted April 12, 2006.
BACKGROUND: The adult i phenotype has been characterized as the presence of a very low level of I antigen but a high quantity of I antigen on red blood cells (RBCs). It has been noted that this rare phenotype is partially associated with congenital cataracts. It has been demonstrated that the human I locus expresses three IGnT forms, IGnTA, IGnTB, and IGnTC, and that the IGnTC gene is responsible for the I antigen expression on RBCs. This report describes molecular genetic analysis of a Taiwanese person with the adult i phenotype but without congenital cataracts.
STUDY DESIGN AND METHODS: The five exon regions of the IGnT gene of the adult i individual were amplified by polymerase chain reaction (PCR) and cloned, and the sequences were determined. The activity of the IGnT enzyme expressed from the mutant IGnTC gene identified in this i adult was analyzed.
RESULTS: The presented adult i individual possesses wild-type IGnTA and IGnTB genes but a mutant IGnTC gene with a 243T>A nucleotide substitution, which predicts an amino acid alteration of Asn81Lys. PCR-restriction fragment length polymorphism analysis has been used to show that this IGnTC*243A allele is uncommon in the general Taiwanese population. The activity of the IGnT enzyme expressed from the mutant IGnTC*243A gene was significantly reduced when compared with that expressed from the wild-type IGnTC gene.
CONCLUSION: A novel IGnTC allele with a 243T>A missense mutation was demonstrated in our adult i Taiwanese without congenital cataracts. The molecular basis revealed for this adult i case agrees with the proposed molecular genetic mechanism, accounting for the partial association of the adult i phenotype with congenital cataracts.