Evolutionary biologist receives early career award from NSF
An evolutionary biologist at The University of Texas at Arlington has received a prestigious award from the National Science Foundation (NSF) aimed at early-career faculty who have the potential to serve as academic role models.
Sen Xu, assistant professor of biology, received a Faculty Early Career Development Award, known as CAREER, approaching $1.2 million over a five-year period. Through his project, titled “CAREER: Understanding the Evolution and Genetic Basis of Meiotic Recombination Rate,” Xu seeks to understand how genetic diversity occurs at the molecular level.
“I am very grateful that NSF funds this innovative research direction,” Xu said. “Personally, it is a great honor to be recognized with this award.”
In his research, Xu examines how the process of recombination in sexual organisms is modified by genetic variants and through interaction with environmental changes. Recombination is a process in which parts of DNA are broken and recombined to produce new combinations, creating genetic diversity. Recombination is a fundamental part of meiosis, a special type of cell division that gives rise to sperm and eggs and is essential for safeguarding the integrity of genomes of sperm and eggs, Xu said.
Xu’s CAREER project will address an important yet understudied question in evolutionary biology: whether recombination rates evolve in response to natural selection in animals and plants, and what genes control the variation of recombination rates.
“What recombination does is to shuffle the DNA sequences of a pair of chromosomes—for example, between our two copies of chromosome 1,” Xu said. “We humans inherit half of our genomes from our father and half from our mother.
“Interestingly, what we inherit from our parents is a shuffled combination of genes from our grandfather and grandmother, thanks to recombination that happens in meiosis. It is also interesting to note that recombination rate varies extensively between individuals, populations, and species.”
Despite recombination being such an important process, relatively little is known about what evolutionary processes govern the evolution of recombination rates.
“This stems from the current limitation of how we estimate recombination rates,” he said. “Estimating the recombination rate through constructing a genetic map for a species is tedious and labor intensive, often requiring us to sample hundreds of individuals in a crossing experiment and collect information on hundreds of molecular markers. All these efforts in the end would give us just one genetic/recombination map.”
Xu’s project will develop a novel approach of whole-genome sequencing of single sperm. Building on his previous work, this approach will allow Xu and his research group to sequence the entire genome of hundreds of sperm with thousands of molecular markers in a rapid and economical way.
Xu and his team will use this approach with their chosen model organism, the microcrustacean Daphnia, a water flea that lives in freshwater habitats around the world.
“Hopefully, this approach will stimulate researchers working on other species to use this technology for studying recombination rate as well,” Xu said.
The funded research project will also take advantage of this single sperm sequencing approach to estimate recombination rate for multiple populations in two Daphnia species.
“In each population, we will build genetic maps for multiple individuals, which would yield hundreds of genetic maps for each species,” he said. “This large number of genetic maps will then empower us to understand whether the divergence of recombination rates between populations and between species is driven by natural selection.”
Lastly, Xu will perform genome-wide association analyses to pinpoint the genes and genetic variants that contribute to the recombination rate among individuals, populations, and species. He and his team will use a gene-editing technique called the Crispr-Cas9 approach to introduce these genetic variants to a common genetic background to test their effects on recombination rates in Daphnia.
In 2019, Xu was awarded a five-year, $1.89 million grant from the National Institutes of Health for a study that also utilizes Daphnia to investigate fundamental biological processes that can lead to fertility problems in humans.
Xu is the third College of Science faculty member to receive a national early career award in the past four years. He Dong, associate professor of chemistry and biochemistry, received an NSF CAREER award in 2018, and Matt Walsh, associate professor of biology, received an NSF Presidential Early Career Award for Scientists and Engineers in 2019.
College of Science Dean Morteza Khaledi said Xu’s award is a fitting recognition of the quality of his research and its importance in his field.
“This is a tremendous achievement for Dr. Xu and shows again the high level of research and teaching being done in the College of Science,” Khaledi said. “Dr. Xu’s work has the potential to make significant advances in our knowledge of evolutionary processes and how they affect genetic diversity.”
- Written by Greg Pederson, College of Science