All issues > Volume 42(7); 1999

Original Article

J Korean Pediatr Soc. 1999;42(7):900-910. Published online July 15, 1999.

Characterization of Molecular Defects in Korean Families with Inherited Ornithine Transcarbamylase Deficiency and Their Genotype-Phenotype Correlations

Han-Wook HW Yoo¹

¹Department of Pediatrics, Asan Medical Center, School of Medicine, Ulsan University, Seoul, Korea

Correspondence Han-Wook HW Yoo ,Email: 1

Abstract

Purpose
: This study was undertaken to characterize molecular defects in Korean families with ornithine transcarbamylase(OTC) deficiency, correlate it with phenotype using in vitro expression study, and utilize it for making prenatal molecular diagnosis.
Methods
: To investigate molecular lesions resulting in OTC deficiency in 15 unrelated Korean families, the OTC genes of probands were amplified exon by exon and analyzed by direct sequencing of double stranded DNA. Based on their molecular lesions, prenatal monitoring of six fetuses at risk from four unrelated families was performed using genomic DNA from chorionic villi sampling(CVS). To analyze expression in vitro, mutant OTC cDNAs were constructed and cotransfected with β-galactosidase gene into COS-1 cells by using lipofection. After transient expression, OTC activity was measured by colorimetric method.
Results
: Nine different mutations were identified in 10 out of 15 families ; six mutations were novel, involving well-conserved nucleotide sequences across species or CpG hot spot : T44I, M205T, H214Y, D249G, F281S, R320X. In vitro expression study revealed that the H214Y mutant showed a residual enzyme activity(13% vs 0% for D249G, 0% for R320X). However, clinical phenotype for H214Y was severe with neonatal onset. Three mutations were previously reported in other ethnic groups : R26Q, R141Q, R277W. Prenatal evaluation of 6 fetuses including one fraternal twins were successfully made. We predicted the outcome of all fetuses prenatally. They were also tested postnatally for the mutations to be unaffected.
Conclusion
: The genotypes of Korean patients with OTC deficiency are genetically heterogeneous. Therefore, molecular diagnosis should be individualized in each family with OTC deficiency.

Keywords :Ornithine transcarbamylase(OTC) deficiency, Molecular defects, Genotype-phenotype, Expression, Prenatal diagnosis