“Today, the human genome is easier to sequence but harder to interpret. That’s where statistical genetics comes in.”
And that’s also where Dajiang J. Liu comes in. Now an assistant professor in the Department of Public Health Sciences in the College of Medicine at Penn State University, Liu earned his Ph.D. in statistics (STAT) from Rice University in 2011.
“He is one of the best students we ever had. He is a statistician but with a deep knowledge of mathematics. He finally chose statistical genetics and genetic epidemiology, and does a lot of work with the so-called ‘rare variants,’” said Marek Kimmel, professor of STAT at Rice and Liu’s doctoral co-adviser.
With the aid of two active grants from the National Institutes of Health (NIH) totaling $2.7 million, Liu pursues what he calls his “central theme”: developing statistical methods for analyzing large data sets. With the larger grant he studies genetic variants that alter gene function and occur sparsely in a population, but may play a significant role in various diseases. With the other, Liu analyzes the “genetic architecture” for smoking addiction and nicotine dependence.
“Despite the common view,” Kimmel said of Liu’s work, “many genetic diseases are not caused by one sledgehammer blow to the gene, but by many smaller alternative mutations acting separately or in concert. Rare variants cause statistical problems if you want to detect then. A given variant can cause disease in only five families, so the sample size is small.”
Liu became interested in rare genetic variants thanks to his other doctoral adviser, Suzanne Margaret Leal, professor of molecular and human genetics at Baylor College of Medicine and adjunct professor of STAT at Rice. His doctoral thesis was titled “Statistical Methods for Mapping Complex Traits Due to Rare Variants Using Sequencing Data.”
“I was very fortunate at Rice with the people who worked with me. Combined, Professor Kimmel and Professor Leal gave me excellent preparation for the area that has become my specialization,” said Liu, whose other research projects have included investigations of lipids and lupus.
In 2003, he earned his B.S. in applied mathematics and economics at Peking University, followed by an M.A. in mathematics from Rice in 2006. After getting his Ph.D., Liu spent two years as a postdoctoral researcher at the University of Michigan, before joining the Penn State faculty in 2014. Last year he received the Penn State College of Medicine Distinguished Early Stage Investigator Award.
Liu is now the principal investigator of a lab with four Ph.D. students, a postdoctoral research fellow and two rotation students. “My lab at Penn State is very busy,” Liu said. “We’ve been generating datasets using high throughput genotyping and sequencing. At the same time, we are developing cutting edge computational approaches to effectively and efficiently analyze these datasets. What this all is leading up to is personalized medicine, customizing diagnosis and treatment to the individual patient.”