My primary interest is to study evolutionary dynamics of genetic variation and the underlying mechanisms in natural populations. I am broadly interested in studying a variety of topics including theoretical and statistical population genetics, genome evolution, conservation genetics, host-parasite co-evolution, and genetic basis of phenotypic adaptation or deficiency (e.g., genetic diseases in humans).
Human population genomics
Disease susceptibility may arise as a consequence of adaptation to other environmental stress. Recent findings have suggested that higher rates of kidney disease in African Americans may be attributed to several risk alleles at the APOL1 gene. These risk alleles may have provided resistance to trypanosoma infection (African sleeping sickness) in the ancestors of African Americans. I am currently studying nucleotide variation of the APOL1 gene from diverse African populations and discovered several haplotypes that cause amino acid changes at the functional domains required to lyse trypanosoma parasites in human serum. I have conducted a genomic approach to identify signatures of recent selection on these haplotypes and found that different alleles may be favored by selection in different human populations. This pattern of spatially heterogeneity in selection toward alternative alleles may be relevant to the distinct distributions of two trypanosoma subspecies or the possibility of the deleterious effects of these haplotypes in kidney function.
My research also focused on identification of genetic variants relevant to susceptibility of infectious diseases in human populations. I studied genetic variation of glycophorin A and B, two major erythrocyte-surface receptors that interact with the malaria-causing parasites, Plasmodium falciparum, across diverse human ethnic groups in Africa and obtained several novel and exciting findings. We identified signatures of balancing and positive selection on different extracellular domains of glycophorin A. We also showed that MN blood-type polymorphisms encoded by glycophorin A have been maintained jointly by balancing selection and gene conversion in many malaria-endemic populations in Africa. In addition, we identified a haplotype causing three amino acid changes in the extracellular domain of glycophorin B.
Molecular evolution and phylogeny in Drosophila
Before joining Sarah’s lab, my doctoral studies with Dr. Hiroshi Akashi at Penn State University focused on molecular phylogeny and evolution of Drosophila melanogaster and its closely related species (D. simulans, teissieri, yakuba, erecta, and orena). Although the phylogeny among these species was thought well established, we found strong molecular evidence supporting an alternative tree topology (Ko et al. 2003). We also studied patterns and rates of molecular evolution among these lineages and the underlying evolutionary forces. We inferred nucleotide changes on the tree branches among these species and found prevalence of non-stationary nucleotide evolution and weak selection at synonymous sites (Akashi et al. 2006). We also identified striking regional heterogeneity in patterns and rates of base composition evolution in D. yakuba and orena (Ko et al. 2006). These results illustrate that temporal (on a gene tree) and spatial (near telemetric chromosomal regions) fluctuations in evolution parameters may be frequent even among closely related species, and imply that stationarity assumptions in modeling DNA evolution for phylogenetic reconstruction or in detecting footprints of natural selection (e.g., dN/dS test) may be often violated.
Burroughs Wellcome Travel Scholarship for Ecology and Evolution of Infectious Diseases (EEID) Meeting
Postdoctoral Research Travel Award for the Society of Molecular Biology and Evolution (SMBE)
Trainee Research Award for the American Society of Human Genetics (ASHG)
Platform Moderator for the session of Evolutionary and Population Genetics in the American Society of Human Genetics (ASHG)
Biology Graduate Student Research Excellence Awards
Postdoctoral Researcher, Department of Genetics, University of Pennsylvania School of Medicine
Research Associate, Department of Biology, University of Maryland
Teaching Assistant, Department of Biology, Pennsylvania State University
Research Assistant, Section of Integrative Biology, University of Texas at Austin, July 1999 - May 2000
Research Assistant, Department of Biology, Tunghai University, Taiwan, January - June 1999
Research Assistant, Molecular Oncology Laboratory, Department of Education and Research, Taichung Veterans General Hospital, Taichung, Taiwan, 1997 - 1998
Research Assistant, Wildlife Ecology Laboratory, Forestry Department, National Pintung University of Science and Technology, 1993 - 1995
Ko, W.-Y. and S.A. Tishkoff, Effects of gene conversion and natural selection on the evolution of human glycophorins coding for MNS polymorphism in malaria endemic African populations. Young Researchers Conference On Evolutionary Genomics, Tokyo, Japan, August 1-2 2011 Invited talk
Ko, W.-Y., F. Gomez, and S.A. Tishkoff, Spatially heterogeneous selection on human ApoL1 variants among diverse African populations in trypanosomiasis endemic areas. The annual meeting of the Society for Molecular Biology and Evolution (SMBE), Kyoto, Japan, July 26 - 30, 2011 Platform presentation
Ko, W.-Y., K. Kaercher, and S.A. Tishkoff (2010) Adaptive evolution of human glycophorin loci in malaria endemic African populations. The 60th annual meeting of the American Society of Human Genetics (ASHG), Washington DC, Nov 2 - 6, 2010 Platform presentation with trainee research award (selected as the featured research in a press briefing session at the Meeting on the latest advances in evolutionary and population genetics research)
Ko, W.-Y., K. Kaercher, and S.A. Tishkoff (2010) Adaptive evolution of human glycophorin loci in malaria endemic African populations. The annual meeting of the Society for Molecular Biology and Evolution (SMBE), Lyon, France, July 4 - 8 2010 Platform presentation with travel award
Ko, W.-Y., F. Gomez, and S.A. Tishkoff, An evolutionary and population genetic approach to malaria susceptibility in Africa. The 79th Annual Meeting of the American Association of Physical Anthropologists (AAPA), Albuquerque, New Mexico, Apr 14 - 17, 2010 Invited talk
Ko, W.-Y., K. Kaercher, and S.A. Tishkoff, Population genetic analysis of erythrocyte surface glycoproteins in malaria-endemic human populations of Africa.
Ko, W.-Y., K. Kaercher, and S.A. Tishkoff (2007) Population genetic analysis of erythrocyte surface glycoproteins in malaria-endemic human populations of Africa. Ecology and Evolution of Infectious Disease PI Meeting, Albuquerque, New Mexico, Dec 02 - 05, 2007. Poster presentation
Ko, W.-Y., S. Piao, and H. Akashi, Strong regional heterogeneity in base composition evolution on the Drosophila X chromosome.
Ko, W.-Y., R. David, J. Anoop, C.-F. Lin, S. Piao, and H. Akashi (2004) Lineage-specific molecular evolution in the Drosophila melanogaster species subgroup. Genome and Evolution conference for the Society for Molecular Biology and Evolution at Pennsylvania State University, University Park, PA, June 17 - 20 2004. Poster presentation
Ko, W.-Y., R. David, and H. Akashi, Molecular phylogeny of the Drosophila melanogaster species subgroup.
Ko, W.-Y., F. Gomez, and S.A. Tishkoff (2012) Spatially heterogeneous selection on human ApoL1 variants among diverse African populations in trypanosomiasis endemic areas (In preparation for submission)
Gomez, F., W.-Y. Ko, and S.A. Tishkoff (2012) An evolutionary and population genetic approach to malaria susceptibility in Africa. (An invited review article in an edited volume for the conference of the American Association of Physical Anthropologists (AAPA), scheduled to be in press in 2012)
Ko, W.-Y., and S.A. Tishkoff, Disease and Evolution. Evolution of human erythrocyte-specific genes involved in malaria susceptibility, In "Evolution In The Fast Lane: Rapidly Evolving Genes and Genetic Systems". Singh R.S., Xu J. and Kulathinal R. J. Ed. Oxford University Press, Oxford. (Scheduled to be in press in 2012)
Ko, W.-Y., K. Kaercher, E. Giombini et al. 2011 Effects of gene conversion and natural selection on the evolution of human glycophorins coding for MNS polymorphism in malaria endemic African populations. Am J Hum Genet 88: 741-754 (Selected as the featured article)
Ko, W.-Y., S. Piao, and H. Akashi (2008) With- and between-species sequence variation in Drosophila teissieri and Drosophila yakuba: evolutionary mechanisms of Codon Bias and protein Evolution. (in preparation for submission to Genetics)
Iida, K., D. L. Cox-Foster, X. Yang, W.-Y. Ko, D. R. Cavener (2007) Expansion and evolution of insect GMC oxidoreductases. BMC Evolutionary Biology 7:75
Ko, W.-Y., S. Piao, and H. Akashi (2006) Strong regional heterogeneity in base composition evolution on the Drosophila X chromosome. Genetics 174:349-362
Akashi, H., W.-Y. Ko, S. Piao, A. John, P. Goel, C. F. Lin, and A. Vitins (2006) Molecular evolution in the Drosophila melanogaster species subgroup: Frequent parameter fluctuations on the time-scale of molecular divergence. Genetics 172:1711-1726
Ko, W.-Y., R. David, and H. Akashi (2003) Molecular phylogeny of the Drosophila melanogaster species subgroup. J. Mol. Evol. 57:562-573
Ko, W.-Y., A note on the playing-dead Behavior of Pipistrellus abramus. Notes of Wildlifers and Newsletter of Wildlifers 4(2):10 (in Chinese)
Ko, W.-Y. (1995) Reproductive cycle of the house bat, Pipistrellus abramus, in South Taiwan. A Tunghai University Publication (Master's thesis, in English).
Graduate Affairs Committee of Biology Department, Pennsylvania State University, 2006