Gillyoung Koh

Pronouns: she/her/hers

Bryn Mawr College Class of 2024

Biochemistry and Molecular Biology Major

From Broomall, PA

Fun Fact: My favorite Disney character is Olaf because of how adorable and funny he is.

In the lab: joined us for the summer research program 2022

Investigation of Long-Term Diversifying Evolution In TAS2R14, A Promiscuous Bitter Taste Receptor In Primates

T2R or TAS2R are Type II taste receptors that are G protein-coupled receptors. When a bitter agonist binds to the receptor, the organism perceives the bitter taste. Bitter-tasting genes code for the proteins which are the bitter-tasting receptors. It is important to perceive bitterness to protect organisms from eating potentially harmful substances, such as cyanide. The receptor encoded from TAS2R14 is very promiscuous. It can bind to more than 150 known, diverse bitter agonists, roughly two-fold more than the second-highest number of known ligands a receptor encoded from a T2R gene can bind to. Possibly, TAS2R14 could have been subjected to long-term balancing selection. In the Bitarello lab, we are exploring whether there is evidence for long-term diversifying evolution in TAS2R14 in the primate lineage. If we can find evidence supporting this, is the long-term diversifying evolution targeting codons in TAS2R14 corresponding to portions of the receptor interacting with the bitter agonists? We hypothesize that this may be true given that certain vertebrate genes have great diversity and that major histocompatibility (MHC) complex genes show balancing selection in certain codons encoding for the binding of antigens. Finally, we will also test whether different subgroups of primates have experienced different selective pressures.

To answer the research question, we are exploring whether we can find evidence on a phylogenetic scale. We will use publicly available protein-coding data for humans and other primates. Phylogenetic approaches will be used to study the evolution of TASR14 in primates. A phylogenetic tree will be created after performing a multiple sequence alignment. Then, codon substitution models implemented in HyPhy and PAML will be used. Diversifying selection, or adaptive evolution, includes positive and balancing selection but not purifying selection. We are testing whether there has been adaptive evolution in TAS2R14 and if so, whether certain codons have been the target of selection, i.e, those more linked to binding specificities of the receptor. If this is true, we would observe elevated dN/dS (rate of nonsynonymous mutations to the rate of synonymous mutations) in codons that correspond to amino acids that recognize and/or bind the agonists compared to other codons in the gene. We are also testing whether different taxonomic groups (Great Apes, New World Monkeys, Old World Monkeys) or groupings based on dietary habits (herbivore, carnivore, omnivore) have experienced different selective pressures.

Bitter taste receptors are not just found in taste buds, but they can also be found in some areas of human airways. These receptors bind to bitter compounds generated by bacteria and can lead to narrowing of the airways to avoid inhaling the potentially toxic substances. This suggests that bitter taste receptors may fulfill roles that we have not discovered yet and learning more about these bitter taste receptors may aid the healthcare and pharmaceutical industries. Along with protecting airways from bacterial infection, bitter taste receptors may have influenced primates’ diet to avoid eating certain foods which may have been potentially toxic, affecting primate evolution.

BMC Summer Research Program Webpage