Extant species have wildly different chromosome numbers, even among taxa with relatively similar genome size (e.g., insects). Humans have 23 pairs of chromosomes, while chimpanzee and other apes have 24. One human chromosome is a fusion product of the ancestral state. The jack jumper ant has the smallest chromosome number possible, with only one pair of chromosomes. This raises the interesting question: How well can a species tolerate a change in “n” without significant changes to genome content? Yeast is easy to engineer, and its 16 chromosomes have been fused before, but only up to 12. We have pushed the limits of chromosome fusion from 12 to two in Saccharomyces cerevisiae using CRISPR-Cas9. Surprisingly, the strain with only two chromosomes grows without major defects compared to wild type. In heterotypic crosses (n=8 X n=16), sporulation was arrested, with drastically reduced full tetrad formation detected and under 1% spore viability. These results indicate that as few as eight chromosome-chromosome fusion events suffice to isolate strains reproductively. The set of strains with varying chromosome number described here may be useful to tackle various and distinct biological questions; for example, aspects of recombination during meiosis, replication origin timing, or the role of yeast 3-D nuclear structure in transcriptional regulation or recombination donor preference, to name a few. I did the fusion chromosome project in the lab of Dr. Jef Boeke.
Questions & Answers
Why did you choose Johns Hopkins for your work?
The Johns Hopkins University School of Medicine is an internationally recognized research institute, having made major biological and medical research discoveries. The Biochemistry, Cellular and Molecular Biology Graduate Program was the best fit for my research interests and my skill set, providing training of a multidisciplinary approach to science.
What does receiving this award mean to you personally and professionally? Do you have any connection with the particular award you received?
When I was in my junior year of graduate school, I enjoyed listening to talks and posters presented at Young Investigators’ Day. The winners have done excellent work at Johns Hopkins, and I admire them as my peer role models. By receiving this award, I feel honored to be among them. In addition, my work is being recognized, which gives me a lot of motivation moving forward in my career.
What contributed to your project’s success (special skills, interests, opportunities, guidance, etc.)?
Many factors contributed to my project’s success. The first and most important one is guidance from my mentor, Jef Boeke. His enthusiasm and good sense for science, as well as patience and support of his students, inspired and guided me through my graduate studies.Equally appreciated, he always gives me opportunities to learn and grow, such as giving talks. In addition, the input of my committee members was vital. This project started because of an interesting question raised by one of my committee members, Brendan Cormack. Without that question, we may have not been working on this right now. Finally, Jef’s lab is full of people tackling big ideas using a multidisciplinary approach—nowhere else could this research happen.
What thoughts do you have about Young Investigators’ Day itself, as a celebration of the roles student and fellows play in research at Johns Hopkins?
I think it’s a very exciting and meaningful event, where students and fellows have this opportunity to get together to share their latest scientific discoveries and celebrate cool findings. I feel like the best moment in science is when you can finally share your results with others.
What has been your best/most memorable experience while at Johns Hopkins?
Early in my graduate work, I had a tough situation of having to switch labs and then moving to New York with Jef. Thanks go to my committee members at that time and my program director, Carolyn, for helping me and encouraging me to chase my dreams. I definitely made the right decision. Not only this, but during my time at Johns Hopkins, I always felt supported by the program.
What are your plans over the next year or so?
I’m graduating this year. I will wrap up my other projects in the Boeke lab and look for a postdoctoral position.
Tell us something interesting about yourself that makes you unique. Do you have any special hobbies, interests or life experiences?
In my spare time, I do Chinese painting. My dream is one day to publish my scientific work in a good journal with my Chinese painting as the cover. I also like traveling and living in different cities, to experience being a local rather than a tourist.