Scientist Stories: Roser Vento, Adaptation of Immune Cells

We will move to the next speaker, who will be the first in-person speaker, Rosa Rento. Thank you, Sarah. Do you, Ryan, are you going to project from up there, or does she need to— you'll do it? Okay. Oh, it's there. It's there. Great. I can't see it on Zoom. I can't see the presentation on Zoom yet. Oh, now I can.

Yeah, great.

Okay.

Is there a way of— Yeah.

Lovely. Thank you, Ryan. That's awesome. Can you move the mic a bit closer to your face?

Yeah. Now?

Yeah.

Yeah.

That's better.

So I selected this work on the development of the gonads because I became passionate about development when I joined as a postdoc in 2016 in Sarah's team. And we started together also with Maz Hanifa and Sam Behati this developmental cell atlas. And it was a nice experience. I spent some time in Newcastle dissecting the first embryos. It was great fun. And also Going back also to Cambridge, I also had the opportunity to meet the developmental community here, from which I have learned a lot, including Ashley Moffett but also Asim Surani from the Gordon Institute now. So, yeah, so especially the gonad is quite a unique organ because it really has the germline cells. So those are the cells that will pass the genetic information to the offspring. And it is also such an interesting organ in terms of development. So, it originates from a bipotent gonad and then during development, depending if the males express the SRY gene from the Y chromosome, then they will diverge completely and the tissue architecture is quite different as you can see from this image. And this really has an impact on the biology of the tissue, as I will try to explain. So, in a more general level, what we do in the lab, we are interested in development, regeneration, and the role of immune cells in these two processes. And to do that, we use in vivo and in vitro models, which we can perturb, and then we use single-cell genomics as a readout. But going back to the gonads, so as I was mentioning, this is— I don't know if there is— So as I was mentioning, this is such an interesting organ because it really develops from here, from the gonadal ridge, and with the entry of the PGCs, which are the precursors of the gametes, then this gonadal ridge, which will start the sex-specific specification, and by default you will have an ovary. And if the SRY gene is expressed in the males, then you will have a testis. And then these two organs are quite distinct. So the ovary is really an open structure, more or less, and then you will have these germ cells which are surrounded by the granulosa. And it is important to mention that in humans, so all the number of the gametes in females is determined at birth. So then development is quite an interest— quite an important step. While in the testes, you have these closed structures in the seminiferous tubules. And that is important because actually in males you have these progenitors of the gametes proliferating and doing meiosis step in the adult life. So, you need to protect these structures from the immune response. And there are multiple differences between mouse and humans in terms of the time, also the cellular composition and the regulatory programs. And actually, this has consequences in the development of in vitro gametogenesis in humans. So, we know that the protocols that are developed in mouse do not work in in humans and we don't have good protocols for humans. So that really was our intention and to study how the human gonadal development occurs in humans and really compare to what we know in mouse to see what is different and what we can also change in vitro in the future. So to do that, what we did is to profile the gonads in both mouse and human in the same protocol able to compare. And then we cover stages of sex specification and differentiation. And we did this in more than 50 gonads. And then we did multi-ome and spatial analysis. And what we did here is a harmonized annotation. And that was really difficult because the cell types are quite different. And to do that, what we did is to really look at the regulatory programs, at the driver transcription factors, and also at the location of these cell types in space. So then we annotated the same cell types across the different modalities and also across the different species. And that was important to start comparing them. So we— here what we did is to use support vector machines, and we train a reference using the human cell types, and we projected into the mouse cell types. And what we can see is that there are a lot of similarities between human and mouse in a lot of cell types, as you can see for the high probability. And that even includes the germ cells. But then there are some cell types that are the supporting cell types in males and females, which have very low probability, just showing how divergent they are. So it's important to understanding the supporting cells because the germ cells and the supporting cells are in constant dialogue. And this dialogue is important for the development of these two cell types, and we wanted to understand how this happens. So then, what we did is to analyze the supporting cells on its own, again human and mouse. And this, again, we annotated the cells, and here they are so divergent. So to annotate them, we look also for the location and also the trajectories and where the cell types are coming. And we came up with a common annotation also looking for the main transcription factors driving this process. And what was really interesting, and one of the things that I decided to select here, was that we discovered these progenitor populations that we called early supporting, which connect the columnar epithelium where all cells derive into the Sertoli in males and the granulosa in females. And actually, this is the population that for the first time express this SRY and determines the sex specification. And again, I want to highlight how this population has really specific markers in humans that are not found in mouse. And the only way to look for these similarities was by using these omics approaches. So, it is quite complicated as in development, there are multiple waves of development. I described the first wave, but then there second waves, and here is the ovary. And what we know in mouse is that these waves also have a different location. And actually, we showed that in our case is the same in humans. We also have different locations for the first wave and the second wave, despite again, the second wave having completely different markers and regulatory programs in humans. So, okay, so we have a gradient on this granulosa. And because of interest of time, I didn't show you, but also we also show that there is a gradient of the germ cells as they differentiate. And what we know, what we want to understand is how cells communicate to each other while this dynamics occurs. And to do that, we investigate, we use CellphoneDB, which is a computational tool that Mirjana and I developed during our postdoc in Sarah. And then that my team has bring it to the next steps, just using also spatial data and also multi-ome to link this the cell-cell communication with downstream signaling. And I am not going to go into a lot of details for this, but just looking for the cell-cell communication and regulatory programs, we have done this recipe to understand how germ cells develop. And we are quite excited because we think it's a first step to build the artificial gametes. And just to finish, I am an immunologist by heart, so we also wanted to look at the immune cells in this tissue. And what we found is the majority of immune cells are macrophages. So then we decided to integrate with other macrophages in other fetal tissues. And what we found is that there are two novel testicular macrophages, one that really has a microglia signature and the other one that has an osteoclast signature, which was a bit weird because we don't have bones and we don't have nerves inside the testis. So then this means that this transcriptomic signature means more than being a macrophage in the brain and the osteoclasts. And to look for what that means, we decided to stain for these macrophages together with the structural markers. And here I'm just showing the results for the osteoclasts. Osteoclasts also have a role in remodeling, chondrocyte remodeling. And indeed, we can see our osteoclast-like in the testis close to the endothelial cells. And also, they peak at 14 postconceptional weeks, which is when all this endothelial remodeling happens in the testis and not the ovaries. So, what was also quite interesting is that the microglial-like are really trapped here in the seminiferous tubules, which is the first time that we see an immune cell there. So, those are Jokszak-derived macrophages that maybe became retained here during development. And we think that there, they can be phagocytosing some germ cells that are unwanted for whatever reason. And really, just to conclude and to link into future directions, we are quite excited about all these protocols for in vitro gametogenesis. To be honest, not only in humans, but also to look for cross-species comparisons and start developing this for other animals as well. Then we are also interested in looking for the developmental programs that coexist between features and the disease, such as ovarian cancer, and then to explore more the tolerogenic microenvironment in the adult testis. And with this, I just want to conclude by acknowledging Luz García Alonso and Valentina Lorenzi from my team, who have been really pushing this work together with other collaborators in Cambridge and also in Newcastle. Thank you.