Sensory differences on the basis of sex: why research in all-male cohorts is passé.
Dr. Manon Bohic is a postdoctoral associate at Rutgers University who studies the neuroscience of touch and pain. Manon completed her graduate studies at Aix-Marseille Université, France, and has now moved to the US to further her training in neurobiology, behaviour, and molecular genetics. Earlier this year, Manon published a first author manuscript based on her PhD research, titled “Loss of bhlha9 impairs thermotaxis and formalin-evoked pain in a sexually dimorphic manner” in Cell Reports. You can read the article here.
Congratulations on the publication of your first author paper! I always like to start by asking about the backstory for all of this work, and of course, what the major findings were.
The lab where I did my graduate studies is interested in the sensory neurons of the skin. My graduate advisor (Aziz Moqrich) did his postdoctoral training in San Diego in Ardem Patapoutian’s lab, where he found some really interesting genes that are differentially expressed in different skin sensory neurons. So when he started his lab, he was basically using all of that data that he accumulated during his postdoc to try and investigate that a bit more. In particular, there is one subset of skin sensory neurons that are a little different from the others. Usually, we classify them based on their electrical properties, or their diameter, or their role in what we feel. The neurons we look at in this paper are kind of at the crossroads between different populations. We have, for example, a lot of neurons in the skin that are specialized for touch - and they allow us to feel different types of touch. They are usually pretty big neurons, so that we are really aware of what’s happening around us... what we are touching, and what is touching us. The neurons that we were interested in are within that touch subset, but they are the smallest and the slowest ones, so they are a little strange. Other small neurons are usually neurons that transmit information about pain. But these small neurons don’t detect pain, so they are strange little neurons that we don’t know much about yet apart from human studies showing they allow us to feel human touch.
bhlha9 is specifically expressed in these particular skin sensory neurons. There is very little expression elsewhere in the body, which makes it an attractive tool to manipulate our neurons of interest. This gene is a transcription factor, which basically allows the neuron to acquire its identity. So we thought if you knock out this kind of gene, there is a good chance you change the identity of the neuron. This allows us to figure out the functional role of that neuron. That’s the strategy that we used. I had a molecular genetics background, and I was working on generating other mutant mice, so I tried to make my own mouse where I silenced the gene. But an Israeli team that was also working on it for a whole different reason beat us to the punch. They generated the mouse and they were willing to share it with us. So long story short, I got the mouse from Israel, in Marseille, and that was already an exciting aspect of research right there, international collaborations, and I started studying their behavior. We do a lot of behavioral studies in the lab, because of our interest in sensory neurons. We try to figure out how mice feel touch, temperature, and what underlies the transition from acute to chronic pain. What I found was that two different aspects of the behavior of the mice seemed to be affected when you silence bhlha9. One is that mice are not as sensitive to changes in temperature, and the other one is that they feel inflammation more intensely. The lab had noticed across different projects that sometimes there was a different effect in males and females, what is called sexual dimorphism. So, I looked into whether the effect was the same in males and females, and it turns out that the silencing of bhlha9 does not affect the females at all, and only the males become hypersensitive and feel temperature differently. I thought that that was really cool. Once you have a global behaviour like that, you try to figure out exactly how it’s happening, because you don’t know for sure that it’s happening in the skin, or the spinal cord, or the brain. We have a lot of really great collaborators across Europe, including in Italy, and across France. So with a team effort we figured out that what had changed specifically in the male mice and not in the females was the amount of GABA - a type of inhibitory neurotransmitter. In fact, there was a huge change in GABA in the male and not in the female. That was why the males became hypersensitive to inflammation and less sensitive to variations in temperature than the females that seem to compensate differently for the absence of bhlha9. Those were basically the major findings: inflammatory pain can work differently in males and females.
Cool. So you found a pretty major difference when you deleted this gene, and this difference was in male and not female mice. I was wondering if you think that in terms of all sensory neuroscience, if you think that the effects of sex are too often overlooked?
That’s a good question. I think more and more people are starting to look into it. For example, here in research in the US, most NIH grants require that we look at both males and females. It seems this is the necessary way to get people to do this because it is a lot more work. It doubles everything. Until now, most studies focused on males and not females because even to this day, a lot of people still think in research that male mice are more ‘stable’ in their behavior, and ‘more consistent’ whenever you test them which would reduce variability in your results. That’s really a big misconception. We have known for a while now that, due to surges in testosterone, the behavior of male mice tends to be more variable than that of females. They just fight all the time! The females, even across the estrus cycle, are actually a lot more stable in the way that they behave. So ‘behavioral stability’ is not even a good justification anymore for studying only males. All of the findings until probably very recently were from studies in male mice, and there are a lot of things that should be checked just to see if it’s actually true for both males and females. Never mind all of the implications for potential drug therapies and whether they would actually work in both human males and females. There is still a lot of work to be done.
How was the review process for your paper, from submitting it to seeing it online?!
I think it went pretty well. I was really worried, thinking, “Is my study good enough? Is it going to make it into that journal?”. I was just really surprised that they didn’t straight up reject it (laughs). So that was cool. But then, I realised that we actually had some really cool data that would be of interest to a lot of people. It only got better after we had answered the reviewers’ questions. Actually, we had already thought about some of their questions, and I had already started on those experiments to address those remaining questions. It was pretty fair. They gave us enough time to do the extra work which was good, because sometimes these things take at least six months. It was an interesting process. We first submitted the paper two months before I graduated. So I finished the revision process with a lot of help from my grad studies lab. I was already in the US starting my postdoc, so there were a lot of interesting long nights working on the revisions to avoid interfering with my work here. I was really lucky to have a grad advisor who assured me that I was going to stay first author. It was mostly input from me on the design and interpretation of the experiments, rephrasing the paper, putting together the figures, but most of the experiments were people from the lab doing them for me. So that was a really nice team effort again.
That’s awesome. And when you first saw your paper published and online, how did you feel?
Yes, that was crazy (laughs). I think I took a screenshot right away, told my family and my friends. That was really nice.
It’s your first, first author!
Yes, I had been on a couple before, but only as a middle author, so this was my first one. It was a big, big deal for me.
So exciting. I like to ask people why they do what they do. Being a neuroscientist is a very specific kind of job. What made you decide to do a PhD? You also have a genetics background, so I was wondering what got you interested in genetics as well?
Why a PhD… I guess it started with med school in the beginning. That lasted a couple of years. What I learned from that was that I really loved physiology and developmental biology, figuring out how things work. So yeah, I guess I moved on from med school to biology because I was fascinated by things as small as what is inside a single cell, or as big as the neural networks that make us who we are and make us feel what we feel. During my undergraduate studies in Marseille and in London, I met a couple of people who were really passionate about their work, including the person who first introduced me to my graduate studies advisor, who is a researcher and a teacher in France. She is the one that was the link for me between classes - where it is all very theoretical - and actually doing research. It’s thanks to her that I did my first internship in the lab. Once I was exposed to a research lab, that’s when I decided that it was really what I wanted to do. I had been a little disappointed in myself for being not all that interested in med school. I wanted to make sure that research and biology was really what I was interested in. That went really well, I was really passionate about it, it didn’t feel like work. Then I went on to do my master’s degree, and also because I have a competitive side, I guess, I wanted to be one of the best. I got a fellowship, got into a PhD program, and then I did my grad studies. I just kept getting more interested in what I was doing, and I thought, maybe I can have a job in that field? Even though it is competitive, scary, really difficult, that is still my dream!
The genetics background… when I was an undergrad we had a lot of genetics classes, ‘molecular biology’ it was called. I didn’t like it all that much! It didn’t seem all that interesting to me. It wasn’t my favourite class. I learned it, but it was because I had to. Then, once you start doing experiments, you figure out that an understanding of how genetics work allows you to generate the tools to answer the questions that you have. And that is really exciting, to have a question, and to be able to answer at least part of that question. I learned a lot more about genetics once I was doing my PhD, than I did in class. That’s how I got there.
So you already answered my next question, which was going to be, did you always know you wanted to be a scientist? To which the answer was no, you wanted to be a doctor first. Do you think one of the key differences between the kind of person that wants to be a medical doctor versus the kind of person who wants to be a scientist, on a basic level, is wanting to know how stuff works?
Yeah I guess. You go into more detail when you are a researcher and to me it’s as much about curiosity as it is about trying to fix things. But like everyone I was also guided by personal life experience. My grandmother had pancreatic cancer when I was in senior high school, so that’s also partly why I wanted to go into med school. I spent a lot of time at the hospital with her that last year, and I felt comfortable there. I saw the amazing job that was being done by the medical team there. But once I was in med school I realized I was really interested in biology, understanding physiology first to better treat pathologies. Mostly I switched to biology because I had the liberty to make that decision. My parents gave me the freedom to choose what I wanted to do. I’m sure for some people there is not as much freedom. Other parents could be like, “Well, med school was really good because it gave you good stability, a good job, a good salary, so maybe you should try and be a lawyer or something?”. My parents never told me that. They said, “You’re interested in that? You should go for that!”. There was never the question “Are you going to make a life out of this?”. So I am really lucky that way.
Was there a key moment in there that you can remember, where you realized “Oh, it’s not medicine, it’s going to be science!”. Was there a key moment or was it a gradual progression over time?
It was a progression. I was mostly just really disappointed in myself that I didn’t just figure out right away what I wanted to do. That was a challenging year. That one year where I was thinking to myself “Wow, I am failing here. I have never failed at anything before. And now, no matter how hard I try, this is just not something I want to do.”. That was really scary. What am I going to do? For some time, I felt like I had lost a year, that I wasted a year. But then, I got into the Erasmus program that allowed me to do one year of my undergraduate studies in London instead of doing it in Marseille. That is really because, as hard as med school is, it allows you to go way further into cell biology, molecular biology, all kinds of courses that allowed me to get really good grades when I was an undergrad in biology. Those grades allowed me to study abroad for a year at King's College London. So, in hindsight, it was a really good thing for me. It gave me some time to grow a little bit, and the opportunity to live in a different country.
So you are into your first postdoc now, at Rutgers. Since this is still fresh in your mind, what would be your advice to women scientists making this transition from being a graduate student to being a postdoc?
This will sound cliché but I guess, just believe in yourself. One thing you have to remember is that it’s not random if you got all the way here. If you graduated, got into grad school, got your PhD, and are looking for a postdoc, it means that you are good at what you do. You know what you’re doing, you have made decisions, and are going through with it. There is no reason to think that you’re not as good as anyone else. You are as good as anyone else. So yeah, don’t be afraid to look around. I think when I was looking for a postdoc I mostly focussed on Europe and the US. But I feel like, that’s a really exciting time, maybe I should have looked all the way to Australia, or Canada, or way more countries, Japan or something?! So just believe in yourself. This is not random if you got all the way there.
I love that. It’s not random!
So you’re from France, and you moved to the USA for your postdoctoral training. For you, what kind of draw or reputation does the USA have for postdoctoral training, coming from a European perspective? What were the key factors in making your decision to train here?
The first thing to know is that to get a research position in France you have to show you can adapt and grow during your postdoc, so either you change research fields or you go abroad. Twenty years ago, it was a big thing in Europe (and especially in France) to do a postdoc in the US. Right now, I think only two or three of my friends (out of the group of eight to ten friends that I had that all graduated at the same time), were really interested in the US. All of the others wanted to stay in Europe. Whereas ten years ago, everyone wanted to come to the US, because it was the “big place” to do research, then you could come back to Europe and hopefully get a position. So it’s an interesting shift, I’m not sure exactly what happened. Maybe because research just keeps getting better in Europe. So it was really a personal choice, because right now you don’t have to go to the US anymore. I could also have done a postdoc in Germany, Sweden, or the UK - in really nice institutions. The US has a reputation for being really tough, really competitive, with hard-working people, but also really good funding. As a grad student, I didn’t know much about funding and grants in Europe but I feel like here, you can apply and propose research on almost anything, maybe a little more than in Europe. Right now, because of the economic crisis it’s becoming a bit more restrictive, which is sad. I think personally, I was interested in coming to the US. I had always thought about doing that. I was also interested in Europe because I really liked the UK. It would have been nice to go back there, and I would have been closer to my family. But I thought, if I’m being honest with myself, I really want to move to the US and see what life is like there, so I think I will try it now. I had put myself in the perfect position to be able to do it and I thought I would regret it if I didn't try it now.
At the moment, it’s kind of crazy, especially being an international person in the USA. So, I was wondering if you had any advice for other early career scientists that are feeling a bit overwhelmed, in terms of still being expected to be doing science at a high level and publishing.
Right, yes. I think we’re all feeling a bit overwhelmed. I don’t see how anyone could not be. There is the pandemic, everything had to stop or slow down. But the expectations are still the same. If you want to get a career, if you want a position later on you still need to push through, keep producing data, and try to get it published. I think, when I start to doubt a little bit, I try to remember why I like science. Why is it interesting to me? Because it’s exciting. It’s a lot of work, but the one or two times in the year that you get positive results that are really interesting, that is such a rush of adrenaline. You are addicted to that, and you want to keep on doing it. The other part of it is that this is a really cool job to discover new countries and talk to so many people from different places. I wonder if there is any other job where there is such a huge international network, where you can talk to so many people who share the same passion, ask questions and answer them together? That’s a big drive for me, to know that there are so many people doing this and going through this together. Otherwise, having good friends. Even for those who live not too far from their family, this is such a demanding job that if your family are not also scientists, they don’t always get why you are spending Saturday or Sunday, or your evenings until midnight at a microscope. So… friends, especially in research, make a world of difference.
If someone said to you “I think you are so cool! You’re a scientist and I want to be exactly like you!”. What advice would you give to them?
That would be so flattering (laughs)! I think I would tell them to figure out what they are really interested in, because there are so many different things that you can work on in research. It took me a little bit of time to figure out that I was really interested in neuroscience, for example. During my master’s degree, I could have gone into a program that was focussed on neuroscience, but instead I chose one that would also allow me to look into stem cells, which I was also super interested in at the time, and developmental biology, like how embryos form and all of that. I just really took my time. I could have just gone ahead with neuroscience and always wondered if that was really what I was supposed to do. So, figure out what you are passionate about, because that is what drives you to keep going when it is stressful and tiring.
How do you hope to see the scientific landscape change for women in the future? Maybe even beyond our career time?
That’s a really good question. I’ve noticed so many differences for example between women in science in the US and in France. I remember when I first interviewed with my current postdoc advisor. Right after meeting her, we were already talking about collaborators that I would be working with if I were to join the lab. Between her and the four or five collaborators that she talked to me about, most of them were women. As opposed to in France, when you graduate, you have a public presentation, they ask you questions and everything. On the committee, there are supposed to be as many women as men, either full professor or team leader, but they all have to be specialized in your topic. It was really hard to find a woman professor or PI, in France, who specialized in my topic, and who was available at that time. Whereas in the US, I could have found someone right away. I was really shocked by that, at the time. When I was an undergraduate student, there were a majority of women, and then during my master’s degree there were twenty women and five men. In grad school, all of a sudden there were just as many men as women. I feel like that trend keeps going when you are a postdoc. I don’t know what happens at that level. I know that now that I’m thinking about becoming a PI someday, I can see how that will be hard to have a family. To take some time just to have them, never mind raise them, just have them to start with. That’s an obvious problem once you are in your thirties, for sure. But why between undergraduate and graduate studies, how there are so many women at first and then so few? That I wonder if it’s not more of a cultural problem, before even getting into having kids and everything. I don’t have the solution, but I see the problem for sure.
For undergraduates and junior scientists, is it a matter of visuals? For me when I joined the lab as an undergraduate, there was a young female postdoc, one of the PIs I was working under was a woman, we had a really cool research assistant Hannah who is a technical wizard, and then there was me. I could see it, so I thought I could be that. If you go into a lab where you are the only woman, or you can’t see all the steps, that would be really hard.
My graduate advisor was male, but his lab was mostly women, so that was really nice! It wasn’t for any reason, he is not biased, he is a really open-minded, cool guy. The female postdoc at the time was really successful. She got an academic position in France which is really, really hard. You have to be among the top 5 at the national level to get a position and she came second... so she did really, really well. She was a really good example. But in terms of PIs in my institute, there were four women to twenty men or something. I also find it interesting that the one female postdoc who managed to get a research position, everyone was saying things to her, like “You got the research position, you should aim to become a PI right away!”. She was not necessarily interested in doing that or not right away, so why is there so much pressure on the women who make it there? It’s almost like, “You have to be the example”. Male scientists don’t have to justify themselves or their choices as much. So it’s harder to begin with, and then you have the pressure to be an example for other women. I think that’s really hard. I think I was even guilty of that, you know, saying things like, “You have been so successful, why don’t you aim for even more?!”. She doesn’t have to do that, she doesn’t have to be an example. She should just live her life and that’s it! There is something that they must be doing differently here and so at least in that one way, there is something we can learn from the US so that there will be more women PIs in France like there are in the US.
Do you have anything else you would like to add?
There are two people I would like to acknowledge. Aziz Moqrich was a really great graduate advisor who allowed me to do research without all the pressure of publishing in particular journals. I feel that a lot more here - and I should - because as a postdoc you need to publish well if you are going to progress along this career path into an academic position. But that was not a pressure that I had to deal with when I was a grad student. That allowed me to focus on “Do I like research? Yes.”, and “What do I find interesting in research?”. I just had to come up with the biological questions, without thinking, “Is that high risk, high impact?” or whatever, which I have to think about more now. And the first person who introduced me to research, Irène Marics, she is a developmental biology teacher in Aziz’s lab, who manages to teach and do research, a pretty impressive feat. So those were two people that showed me the beauty in research. And my family who allowed me to do this! Even though to this day, I don’t know if this is going to be my career. I hope so!