First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping researchers promote themselves alongside their papers. Antoine Canat is first author on ‘ DAXX safeguards heterochromatin formation in embryonic stem cells’, published in JCS. Antoine conducted the research described in this article while a PhD student in Emmanuelle Fabre's lab at Insitut de Recherche St Louis, Université de Paris, France. He is now a postdoc in the lab of Maria-Elena Torres-Padilla at the Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany, investigating nuclear organization and chromatin regulation during totipotency and pluripotency.

Antoine Canat

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

A large part of the genome is made of repetitive DNA sequences that do not code for proteins. A common example of such repeated DNA sequences are the dense foci in mouse cells called chromocenters, which contain pericentromeric regions of chromosomes. These pericentromeric regions are enriched in DNA and histone modifications that maintain their inactivate state, defined as heterochromatin. Heterochromatin integrity is crucial for genome stability and cell identity and is commonly altered in many cancers or during aging. However, the mechanisms regulating heterochromatin formation are not fully understood. Here, using different embryonic stem cell (ESC) culture media, we discovered that DAXX, a chaperone protein that binds to the histone variant H3.3, is essential for cell survival in the ground state of pluripotency. Indeed, the absence of DAXX results in major alterations of heterochromatin integrity, ultimately leading to cell death.

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

In a broad sense, this project was not clearly defined from the beginning. It was mostly constructed day by day after experiments, ideas and errors. This led to a number of negative results and closed paths. I think this taught me the resilience and motivation to work in the lab. On the experimental side, it is always challenging to set up new techniques. This project involved applying some live-imaging techniques. What I learned from challenges in these moments is to ask for help. There is always someone that can help you. And I hope that, at some point, I can help others in return.

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

As often in science, this specific project was not my main focus at the beginning of my PhD work. I generated an ESC knockout line for DAXX and was interested in testing the effects in 2i medium, which lowers the levels of DNA methylation. After only a few days in culture, I realized that the number of cells in the plate was drastically reducing, until no cells remained. This effect was striking, and thus I thought that I did something wrong. I asked my supervisor to repeat the experiment himself to make sure this was not a mistake. When the effect turned out to be reproducible, the project began. And from then it became like a game to understand what was going on here; the fun part started.

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

Journal of Cell Science is part of a not-for-profit organization that publishes many papers important to the fields of cell and developmental biology. In addition, another PhD student from the lab, Fabiola García Fernández, recently published one of her papers in Journal of Cell Science. It thus seemed a like the perfect fit for our story.

Immunofluorescence showing DAXX and PML localizing at H3K9me3-marked chromocenters in pluripotent embryonic stem cells cultured in 2i medium supplemented with vitamin C (2iV).

Immunofluorescence showing DAXX and PML localizing at H3K9me3-marked chromocenters in pluripotent embryonic stem cells cultured in 2i medium supplemented with vitamin C (2iV).

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

My PhD work was supervised by Pierre Therizols, at the time a permanent researcher in the lab and corresponding author on this paper. He has been a great mentor to me, and he kept my passion for science intact after four years in the lab. Of course, everyone from the lab was very important, and having a nice lab atmosphere was clearly an invaluable advantage, as it was a nice feeling to go to work every day. Apart from those in my lab in Paris, I am also grateful to Rodney Rothstein at Columbia University. I did my master's degree internship in his lab, and he kept acting as a mentor to me after my time there ended, giving me insightful advice on the scientific world.

What motivated you to pursue a career in science, and what have been the most interesting moments on the path that led you to where you are now?

As a kid, I did not really know anything about science and research. This came by chance at university, where I realized that I loved biology. At the beginning of my master's degree in Paris, we had a seminar on chromatin organization. That's when I decided I had to work in this field.

Who are your role models in science? Why?

I grew up with the images of many French scientists, including the Curie family with Marie and Irène, but also François Jacob and Jacques Monod. They notably paved the way to multiple fields that emerged from crucial genetics experiments. Furthermore, they all reached outside of the scientific community in their own way, with books, speeches or political engagement, reflecting on science and its role in society. They were inspiring people.

What's next for you?

I am now working as a postdoc in the lab of Maria-Elena Torres-Padilla, at Helmholtz Zentrum München, where I am investigating nuclear organization in early mouse embryos.

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

I am a regular visitor of thrift shops and any secondhand store in general. I like to find old items, such as vinyl albums.

Antoine Canat's contact details: Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany.

E-mail: antoine.canat@helmholtz-munich.de

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(
2023
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DAXX safeguards heterochromatin formation in embryonic stem cells
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J. Cell Sci.
136
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jcs261092
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