Un Kyung Kim

Genetics of Human Taste Perception

Genetic approaches are rapidly yielding new information about our sense of taste. This information comes from both molecular studies of genes encoding taste receptors and other taste-signaling components, and from studies of inherited variation in taste abilities. Our understanding of bitter taste has advanced by combined information from discovery and study of the TAS2R family of taste receptor genes, hand in hand with genetic linkage and positional cloning studies, notably on the ability to taste phenylthiocarbamide (PTC). Sweet and umami tastes, mediated by TAS1R receptors, are becoming well-characterized at the molecular genetic level, and these taste classes are now targets for linkage, positional cloning, and genetic association strategies. Salty and sour tastes are still poorly characterized in genetic terms, and represent opportunities for the future.

Genetics of individual differences in bitter taste perception: lessons from the PTC gene.

The ability or inability to taste the compound phenylthiocarbamide (PTC) is a classic inherited trait in humans and has been the subject of genetic and anthropological studies for over 70 years. This trait has also been shown to correlate with a number of dietary preferences and thus may have important implications for human health. The recent identification of the gene that underlies this phenotype has produced several surprising findings. This gene is a member of the T2R family of bitter taste receptor genes. It exists in seven different allelic forms, although only two of these, designated the major taster and major non‐taster forms, exist at high frequency outside sub‐Saharan Africa. The non‐taster allele resides on a small chromosomal region identical by descent, indicating that non‐tasters are descended from an ancient founder individual, and consistent with an origin of the non‐taster allele preceding the emergence of modern humans out of Africa. The two major forms differ from each other at three amino acid positions, and both alleles have been maintained at high frequency by balancing natural selection, suggesting that the non‐taster allele serves some function. We hypothesize that this function is to serve as a receptor for another, as yet unidentified toxic bitter substance. At least some of the remaining five haplotypes appear to confer intermediate sensitivity to PTC, suggesting future detailed studies of the relationships between receptor structure and taste function.

Characterization of microsatellite markers closely linked with PKD loci in the Korean population

Abstract Autosomal Dominant Polycystic Kidney Disease (ADPKD) is one of the most common inherited renal disorders in the world. Mutations in PKD1 located on chromosome 16p13.3 are responsible for 85% of all the ADPKD patients whereas mutations in PKD2 on chromosome 4q21–23 are responsible for the rest of the cases. Genetic heterogeneity and the problems of mutation detection in PKD1 suggest that linkage analysis is an important approach to study the genetics of ADPKD. To evaluate the availability of six (CA)n microsatellite markers for the linkage analysis of ADPKD in the Korean population, we examined the allele frequencies and heterozygosities of the markers. With the exception of KG8, five markers were highly informative, with PIC values over 0.5, but the PIC value of KG8 marker was less informative than other five markers because of the low number of alleles. Therefore, this study will be useful in linkage analysis for ADPKD families in the Korean population.