First person – Victor Palacios

Victor Palacios

How would you explain the main findings of your paper in lay terms?

In this study, we characterized the role of a conserved gene called Importin-9 (Ipo9). Ipo9 encodes a nuclear transport protein. While most transporter proteins are essential, disruption of Ipo9 does not cause lethality; instead, it impairs fertility in female and male flies. We noticed that embryos from Ipo9-knockout (Ipo9^KO) female flies died early during embryogenesis. When we analyzed Ipo9^KO testes, we found that they have rounded cells corresponding to early developing germ cells, but they lack elongated sperm. Also, we found that Ipo9^KO male germ cells cannot remove histones and import proteasome proteins properly into the nucleus, both of which are essential for male germ cell maturation. In addition, we analyzed meiosis, which is a common process between female and male germ cells. We found that Ipo9^KO germ cells have a defect in chromosome segregation during meiosis. All these Ipo9^KO mutant phenotypes can be rescued by the expression of Ipo9 within germ cells. This evidence indicates that Ipo9 works in a cell-autonomous manner to promote Drosophila germ cell development.

Were there any specific challenges associated with this project? If so, how did you overcome them?

It is not surprising that every project has its challenges. One of the challenges that I faced in this project was identifying male germ cells at specific stages of their development. Drosophila reproductive systems are excellent models for studying germ cell development because they offer a relatively simple platform for identifying every stage of germ cell development compared with other model organisms. However, some stages happen very quickly, and they do not display discrete morphological signatures, making them hard to identify. To overcome this challenge, I used a combination of immunostaining and fluorescence in situ hybridization (FISH) techniques with confocal microscopy to accurately identify nuclei right after meiosis and examine chromosome segregation in male germ cells.

When doing the research, did you have a particular result or ‘eureka’ moment that has stuck with you?

During the process of characterizing Ipo9^KO male germ cells, I stained for histones and protamines. Histones and protamines can be used as markers to distinguish different stages of male germ cell development. The transition from histone to protamines is necessary for chromatin reorganization within sperm nuclei so that they can adopt a compact shape. In wild-type male germ cells, histones are replaced by protamines during the elongation process. Histones are almost never found together with protamines in wild-type germ cells; however, in Ipo9^KO male germ cells, histones were often seen together with protamines. This was a key result that explained why Ipo9^KO male germ cells are unable to elongate. This result also led me to identify proteasome proteins, which are involved in histone removal, as downstream targets of Ipo9.

Why did you choose Journal of Cell Science for your paper?

Members of the lab often look at the table of contents of JCS. Throughout my graduate research, I read a number of interesting papers on sperm development that were published in JCS. I like the layout of the articles and have a lot of respect for the papers published here. I thought Journal of Cell Science would be a great home for my Ipo9 story.

Have you had any significant mentors who have helped you beyond supervision in the lab? How was their guidance special?

I think that all my science mentors have made significant contributions to my professional and personal growth; however, I will focus my answer on my mentor at UT Southwestern, where I have spent more time. I want to mention the UT Southwestern community as an exceptional environment where personal growth, collaborations and healthy competition are fostered. I also want to mention my graduate school mentor Dr Michael Buszczak (Mike), who believed in me and allowed me to join his lab. Mike also trained me as a scientist; he helped me a lot in my communication skills, especially speaking and writing. I grew up in Puerto Rico, so I am used to speaking Spanish. Although many of my classmates spoke English fluently while I was growing up, for me it has always been difficult. To cut a long story short, when I need to present my science, Mike practices my presentation with me until I have mastered it. And a little bit less formally during my first years in the lab, Mike invited me to his office every Friday afternoon to talk about sports and practice my speaking and pronunciation skills (although we would always end up talking about science). I am very grateful to Mike for his dedication and efforts to improve my communication skills, which are as important as my science.

Who are your role models in science? Why?

Gregor Mendel is my role model in science. When I was in college, during my genetics course, I learned about the great Gregor Mendel and his pea plant experiments that led to the discovery of many of the rules of heredity and the introduction of terms like recessive and dominant in reference to specific characteristics (genes). I identified with Mendel's experiments, because when I was seven years old, I also realized that characteristics (genes) are transmitted from parents to the offspring with a particular pattern or frequency. Instead of pea plants, I did my mini-experiments and observations with my pet chickens. Of course, my experiments were not as controlled as they should be, but they were good enough to start my passion for science early during my childhood. Coming back to the moment when I was in college taking my genetics course and discussing Mendelian inheritance, that moment was fascinating, because it explained some of the observations that I made when I was a kid. That moment made such an impression on me that I joined the Genetics, Development and Disease graduate program at UT Southwestern.

What's next for you?

I recently received an offer for a position at Amgen. I am leaving academia and shifting to industry because I want my work to directly help improve or save people's lives.

Tell us something interesting about yourself that wouldn't be on your CV

Besides doing research, I enjoy exploring new restaurants. The Dallas area offers a wide range of cuisines, including Tex-Mex, BBQ, Louisiana Style, Latin, Turkish, Indian, Chinese, Italian, French, Japanese and Thai. For the other half of my free time, I try to burn those calories gained from all the good food by playing volleyball. Dallas offers many options for playing volleyball, from sand to indoor volleyball, and from social to more competitive leagues. There are many volleyball tournaments throughout the year.