How a dating podcast made me question sperm’s epigenetic integrity

by Nichole Holm


I recently heard one of my favorite journalists, Mona Chalabi, discuss one of my least favorite subjects: how men are often encouraged to date younger women.

It’s true—the effect of age on women’s reproductive success is widely known. We’ve all heard of the “biological clock ticking” metaphor, and there’s over a century of data to correlate advanced maternal age with increased risk of genetic abnormalities in children.

However, Chalabi points out that this same encyclopedia of information does not exist for men. In fact, it’s only in the last few decades that any paternal characteristics were considered in fertility studies. Of course, this neglects a significant source of potential research, particularly given how many questions still exist in health and development, such as the causes of infertility, autism, cancer, and many other diseases.

There are a few known facts: respectively, men and women date, marry, and have children at very different ages. The average age for a woman to have her first child is 26 years old, while the average age for a man is 31 years old.

This disparity made me wonder if researchers are considering the father when studying the parental relationships between children and developmental risks. And naturally, because I am a genetics PhD candidate and self-proclaimed nerd, I became curious about the sperm—specifically, whether anyone has noted differences in sperm for men of different lifestyles, which could indicate transmitting different genetics to their children.

Such differences would be seen in the sperm’s epigenetic material. Epigenetics is a field of genetics, which studies the environment around our DNA that controls how genes are expressed.

If we think about our DNA as an instruction manual, it would have all the instructions to grow and keep a human alive. But epigenetic markers on top of our genes act like highlighters and sharpies, marking up the manual to highlight the areas that are important and redacting areas that don’t need to be read, effectively turning genes on and off.

Most of these epigenetic markers develop while we are still a developing embryo—which is why research suggests the maternal environment is crucial for the future health of a baby. Everything from maternal stress, pollution, smoking, and nutrition has been linked to significantly different epigenetic marks on their babies.

But one key difference in the epigenetics of males and females is how their sperm and eggs develop; females develop all of their eggs before they are even born, and release them one at a time once they hit puberty. According to Dr. Janine LaSalle at UC Davis, this means that the epigenetic marks on each egg are likely set in the time that an egg is released, so approximately within a 30-day window before fertilization.

Males, however, do not even produce sperm until they begin puberty, and that sperm is constantly created afterwards.

It was recently revealed that sperm epigenetics are not as stable as we once thought, leaving each newly created sperm susceptible to changes in its epigenetic marks. Recent studies looking into this have confirmed that the lifestyle and exposures of men significantly alters their own sperm’s epigenetics.

Smoking, cocaine, stress, obesity, and even exercise before conception can change not only the epigenetics of sperm, but also increase the risk of their children developing psychiatric and metabolic disorders. This means men’s experiences can change how their genes are expressed in their sperm, and possibly transmit to future children.

Since sperm are constantly generated throughout a man’s lifetime, they are also susceptible to new changes in their genes, called mutations. As men age, they can accumulate more mutations over time, and lead to what is called the Paternal Age Effect (PAE).

A number of syndromes such as Apert Syndrome, Achondroplasisa (also known as dwarfism), thanatophoric dysplasia, and Costello Syndrome are all associated with PAE. In addition, children are at an increased risk of developing some cancers, schizophrenia, and bipolar disorder as paternal age increases.

Even still, not enough research has been done to determine the age at which PAE becomes a concern. Sperm banks limit the age of donors to 40 years old, but it is not nearly as well characterized in men as it is for women. And in spite of the data to support increased risks with paternal ages and exposures, paternal factors are still rarely discussed or considered as much as maternal age.

Overall, the script we have heard and probably repeated to ourselves is based on a great deal of one-sided data.

A mother’s contribution to a child’s health and epigenetics is clear, but data on how the father contributes is not as well known. This field is new, and could hold many of the keys scientists and families have been looking for as to why adverse birth events happen.

Ultimately, equal research into paternal genetics as well as maternal genetics is necessary to understand all components of development and disease. Reducing gender bias in research needs to go in both directions, ensuring the male and female characteristics are understood to better advance the field as a whole.

While men may be selective in a woman’s age, should women be equally as selective in a man’s lifestyle or age? With regards to the data skew highlighted by Chalabi, could further research into paternal epigenetics advance more than just science, but also society?

Time and research will tell.




Thank you to Dr. Janine LaSalle and Dr. Tom Glaser for sharing your time and expertise on maternal and developmental epigenetics, which enabled clarity on this report.

***Do you want to know a more advanced concept in prenatal epigenetics?

After an egg and sperm fuse [to form a fertilized zygote], most of the epigenetic marks are erased. Some are maintained, and the rest are reset according to the needs of the zygote throughout development. The amount to which these differently marked genes in sperm and eggs are remembered (without being erased) is still unknown, but definitely worth more research to understand.


Science Distilled: March Preview

This past Wednesday, March 15 we heard from Dr. Lauren Camp of UC Davis Entomology & Nematology and Hung Doan of UC Davis Plant Pathology. They both spoke about parasite diversity, the many different hosts parasites attack, and the way parasites can hide. Here’s a quick interview for you to meet the people behind the science!


What inspired you to study science?

Hung: Curiosity. As a child I was always curious about how things work. At first I wanted to study medicine, but it turned out I was afraid of blood, and didn’t like harming rats for research. Plants don’t get hurt so I realized I could enjoy research on plants.

Lauren: When I was a kid I realized it was something that I liked. It was also something that I was good at. I would look at my hair, fingers, and toys under a microscope. And my dad is a scientist. While it wasn’t a path he pushed me toward, my siblings and I would go to the lab with him during the summers. I started with an interest in human research and medicine, then realized I didn’t quite fit in with the premed crowd. I took an invertebrate biology class and was so excited by it. You look at animals and think they are all just fuzzy things with spines- but there is so much interesting variation in animals beyond that. And then I started to study parasites and I was done. They were so fascinating evolutionarily, in terms of what they can do and how common they are.

Do you have any affection for your study organism?

Lauren: It’s hard to have affection for something that is harming people and animals, and plants that we depend on for food. My study organism is a parasite that does relatively little to hurt raccoons, but can get into the brains of humans. I do find them fascinating though. A parasitologist once told me, saying you like parasites is kind of inappropriate, because they are harming people all over the world. I do experience excitement when talking to other people about it.

Hung: The pathogens I study just harm plants. Whether I see it in the field or in the lab, I get excited when I recognize the diseases. During my masters’ degree I worked with a plant disease called Fusarium, which lives in the soil indefinitely. When a farmer tells you they spotted it in the field, it’s exciting. Because you can then breed resistance to the disease, and the crops can overcome the disease. I definitely have pictures of Fusarium around- it’s kind of my research baby.

When someone approaches you as a scientific expert, how do you react?

Hung: When you speak with people who don’t have training in science, so many things can surprise them. Just the idea that plants can get disease can be surprising. I grew up in San Jose, where there is lots of biotech, but a disconnect in the way people don’t really know where their food comes from. Plenty of people I know studied a little biology in school, but sort of missed the big picture. It’s also good to have an outlet of friends and family where you don’t have to talk about science all the time.

Lauren: My dad has a PhD, and also studies parasites. So I didn’t have to be the scientist of the family- my dad already had that covered. And it often seemed like he knew about everything, how things work in the world. And that can be intimidating to hear! Now that I have my PhD as well, I’m taking that role a little more with my family. My grandfather and my mom have actually attended some of my formal science talks at meetings, and it helps me think about how I communicate my work. I make sure at the meeting that my mom can understand my science presentation, because she’s actually in the room. Among friends, if someone brings up raccoons I might talk about it. But we have lots of other interests in common- and I have non-scientist friends.

What do you like to do while you’re not doing science?

Hung: I have too many hobbies! I’m starting to scale them down. I enjoy mushroom foraging, hiking, fishing, painting. It varies by day, and I’m pretty spontaneous.

Lauren: I’m building my hobbies back up, after I had scaled them down to finish my PhD. I’m feeling motivated to start running again. I play D&D and love that. I’m reading a lot of books and listening to podcasts. Puzzles can be calming. I also really enjoy spending time talking with small groups of friends.

When people approach you as an expert due to your science background, how do you respond?

 Hung: I run a plant diagnostic lab, so this happens often with farmers. I start with a caveat that I don’t always know the answers. I can guess what the disease is, but usually have to get a sample into the lab to confirm it. Often, it’s not even a pathogen problem in plants, it’s some kind of non-biological stress from over-babying the plants. Overwatering and too much salt can look a lot like pathogens to the untrained eye. Sometimes we get plants from the bonsai industry, where a $10k plant comes in sick. 30 years of careful cultivation, and the plant looks sick because the grower has spoiled it! People can get very worried about their plants, and will text and call me for updates. I also have to be careful in how I state my conclusions – based on what I found in the lab, here is what I’m confident to tell you. But you are always free to get a second opinion. 100% certainty is rare in science.

Lauren: There’s a condition called “delusional parasitosis” in which people are convinced they have a parasite, despite all medical evidence. It’s hard to tell someone that they are  wrong about that. When I do outreach talks, sometimes people have strange ideas about parasites. I respond compassionately, but it’s important to be clear about what makes biological sense. Sometimes friends assume that all humans have parasites. We all have lots of bacteria living within us, but they are not parasites. They are “commensal”, meaning that the bacteria have no negative effect on us. Except when something really bad happens to your immune system, then the bacteria can overgrow and start to act like a pathogen,  like a parasite. But you can’t call these bacteria parasites of humans- because the vast majority of the time, they aren’t! We’re not riddled with worms or protozoans. There are parasites that are possible to get in the United States. But with sanitation and water filtration, we avoid most parasite threats. It’s more of a problem in other parts of the world.

Why is science communication important to you?

Hung: The general public needs to be aware that plants do get disease, and where their food comes from. It affects us personally, and affects politics. If people know that some areas are still under active research- then when it’s time to vote, people are more likely to really look into the issues, read about them, and come to a clear understanding. The plant disease clinic is a big outreach effort. We go to the farmers, to grower meetings. People need to know that science is not so complicated. Anyone can grasp a basic understanding of science! And if people realize that, they’ll be more supportive of research.

Lauren: We need people to understand that science isn’t so complicated. There are bits of science, some of the techniques, that are complex and difficult. But any scientist can talk to people about the basic ideas. I like to do outreach with a range of ages, from young kids up to adults. It’s personally fulfilling and lots of fun. I really enjoy how easy it is to gross people out with parasites! It’s funny to push those buttons just a little bit. I also like to break down the stereotypes, like the idea that someone who has a parasite infection is somehow “dirty”. Parasites are super common in the world. About half of ALL organisms are parasites. It’s also important that people realize when to be concerned about parasites. I also like just telling people about nematodes, which I study. Not all of those are parasites, but they are everywhere too.

Interview by Nicole Soltis of Science Says

Photography by Bobby Castagna of Sac Science Distilled

Science Distilled: HIV research recap

February’s Sac Science Distilled at Old Ironsides featured two HIV researchers from UC Davis: Dr. Lauren Hirao and Brenna Kiniry. You can learn a little more about them and their lives as scientists in our preview post here. Talking to Lauren and Brenna, they both have similar views of what it takes to communicate about hot topics like HIV. They find it important to talk to people as equals and understand where they are coming from. Without taking the time to build a background, it can be hard to bridge gaps in knowledge.


The event kicked off with the scientists sharing some FAQ about their experiences in talking about science. On the whole, the public cares a lot about HIV/AIDS, but sometimes unclear information can lead to inaccurate beliefs. By sharing these preconceptions the speakers ensured the room, full of people from myriad backgrounds, could start the talk on the same page. They also made sure the audience understood the fundamentals of the virus and its global distribution before moving onto sharing research.

Brenna began by teaching the audience about how far treatment and education have come since the virus was first identified in the 1980s. The main concept here is the “cascade of care”. This means that for HIV-positive patients to lead healthy lives, it is essential for them to: be properly diagnosed, receive consultation and care, receive ongoing care, and have continued access to antiretroviral drugs. At any of these stages, patients can lose control of the infection and progress to AIDS. So, effective treatment must take a holistic view of the process; a great anti-HIV drug isn’t going to help much if the people who need it are not getting diagnosed or entering care programs. In fact, Brenna said it is estimated that 1 in 8 HIV-positive people are not aware of their infection. She talked about how important education is in improving that number, and how historical records of infections and mortality show that education really does have a tremendous impact on saving lives from this disease.

We learned about how a perfect cure—one that is safe, effective, and affordable—has not yet been achieved, but that 16 FDA trials are currently underway to test better and better treatments. There was a lot of excitement about how new developments with CRISPR technology could even lead to patients’ own immune cells being modified to help eradicate the virus from their bodies. It’s not going to be showing up in doctor’s offices tomorrow, but it is an exciting possibility.

After Brenna’s segment, the Powerhouse Science Center led us all in an activity to meet our neighbors and see firsthand how quickly an “infection” can travel through a crowd. While we were fortunate enough to have our “infection” be a cup of slightly alkaline water, the exercise still got all the 40-odd participants up, talking, and mixing our cups. Once everyone had figured out who got infected by the original 3 carriers (most people after only 3 exchanges!), Dr. Lauren Hirao took the stage to speak about HIV vaccines.

Lauren did her PhD research on vaccines, specifically ones containing DNA that could be active against HIV, and gave us an overview of the field. Since, “science education is better when it’s anthropomorphized,” she started out with some great cartoons to illustrate the normal immune response to an infection, and how that differs for HIV. She explained a lot of the different challenges, both in biology and in financing, that researchers like her face. Although a prominent HIV researcher claimed in 1984 he believed there would be a vaccine by 1986, Lauren told us about why that has not yet happened and why they have not lost hope.

Research has uncovered more and more complexity over the years, and each new discovery leads to more potential targets. While many of these targets deserve careful study, bringing a vaccine through trials can be prohibitively expensive. Combined with the fact HIV is a rapidly-evolving virus, making a good vaccine becomes quite difficult. It means you must consider the diversity of the target, its evasion from your immune system, and the opportunity your body has to create the right response to the vaccine. Many vaccine trials have taken place over the years, and Lauren told us about some of the more noteworthy ones. While many have had little impact on people’s infection rates in the real world, new ideas are being developed and studied constantly. One class of vaccines that seems to do well across a wide diversity of HIV varieties is broadly neutralizing antibodies. These, as well as other types of vaccines like the DNA ones Lauren studied, are showing promise for the future.

Lauren closed by telling us that there was recently another claim made about the time to an effective HIV vaccine. This time it was Bill Gates suggesting it could be achieved by 2030. While it will still take a tremendous amount of hard work, the discoveries and enthusiasm shared by our speakers made it seem like an important, achievable goal.

Mark your calendars for the next talks on March 15, when we’ll hear from two UCD researchers about the hidden world of parasites in plants and animals- and check out our new location at Streets Pub and Grub!


About the author:

Eric Walters is a PhD student at the University of California in Davis. For more content from the UC Davis science communcation group “Science Says“, follow us on twitter @SciSays

Science Distilled: February Preview

Meet the Scientist, February 9 2017

We’d like you to get to know a bit about our Science Distilled speakers before the monthly talks. We’ll post short profiles to give you a glimpse of the personality and background of our featured scientists!

hirao_lauren_024brenna-kiniry-casual-pic_Left: Lauren Hirao, Right: Brenna Kiniry


We sat down with our two speakers for February’s Science Distilled: Dr. Lauren Hirao, a postdoctoral scholar in the Medical Microbiology and Immunology department, and Brenna Kiniry, a Ph.D. candidate in Microbiology. Both scientists are working on HIV research at UC Davis.

What inspired you to study science?

Brenna – I grew up on a farm and was given a microscope kit while I was in elementary school.  I would take gum, saliva, water from our llama pond, put them on slides and look at them under the microscope. The first time I saw little creatures under the slide I thought “oh my god!”  I would often talk with my father, a doctor, about science and it instilled in me from a young age just how cool science was.

Lauren – In 6th grade we had a science fair project and I got the highest grade in the class. I thought to myself “I must be kind of good at this!” In middle school I also happened to be the best in my science class, and that kept me going and interested in science. From there the rest is history.

How does audience change the way you communicate your science?

Brenna – Kids are much more open to listening to what you have to say. They get excited about something new immediately. If you can hook them in with something fascinating, you have their attention. Adults come with preconceived notions of how they think the world works. Personal beliefs can even hinder adults’ ability to look at the scientific data, or accept the findings.

Lauren – When I speak with friends who aren’t in biology, I try using the public health approach. I relate the science back to them. The politics of our science can be interesting, behind the scenes of the paper. Which means being skeptical. For example, if a press release is tied to a science conference rather than a published article, take it with a huge grain of salt.

How do you set your science workday off to a good start?

Brenna – Music is a big motivator, though the genre depends on how well my experiments are going! I also like to give myself a list of tasks I’m going to concentrate on that day, and try my best.

Lauren – On our floor we have a European style morning routine. We always start our day with coffee and chatting together.


How do you spend your time when you’re not busy working in the lab?

Brenna – I try to play an active role in science-based medicine and skepticism. If a friend brings me some new story about a new miracle food, I’ll turn them back to look critically at the data. Besides that, I fill up my time with science communication- and I love to exercise.

Lauren – I’m always searching for the next novel thing. So if it’s not in the lab, it’s outside it. Falconry, flying trapeze, or traveling. The weirder the activity the more likely I’ll do it. I like to take my nephews on fun adventures. We always do something they’ve never done before, but now the bar is set really high! Parasailing, swimming with sharks, just a few examples of trying to broaden their worldview.

Interview by Nicole Soltis and Bobby Castagna of Sac Science Distilled

Science Distilled: Geological Adventures Recap

On Wednesday, November 16, Sac Science Distilled hosted another pair of engaging public science talks at Old Ironsides. November’s themes were adventure and geology, as professors Dr. Steven Skinner and Dr. Amy Wagner (both of Sac State’s geology department) regaled a packed house with tales of swashbuckling, deep sea diving, and the science behind it all.
Steven Skinner studies paleomagnetism, which is the long-time history of Earth’s magnetic field. This may sound odd, since we think of Earth’s magentic field as constant – it’s the reason magnetic compasses work. But through studying the magnetic properties of certain volcanic rocks, and rocks in sea floor spreading zones, geologists have determined that the Earth’s magnetic field has actually flipped direction many times over the course of the planet’s history. This knowledge enables researchers to figure out how land masses have moved through history, by measuring signatures of the magnetic field that were left in rocks at the time they were formed.
If that wasn’t cool enough, Steven’s research calls him to one of the most extreme environments on earth: Antarctica. In between slides depicting magnetic fields and moving tectonic plates, Steven showed pictures and video of ice-breaking ships pounding through heavy seas, snow-covered landscapes, and steep Antarctic cliff faces. It was clear from his animated demeanor that Steven loves every part of his job, from the lab to the field and back again.
After a short demo from the Powerhouse Science Center on retracing geological history by looking at patterns in rock, we heard from Amy Wagner, whose research focuses on the ocean as it relates to climate. A key piece in understanding what’s happening to our climate right now, and how human activity impacts it, is understanding how it worked in the past. As Amy very eloquently explained, the atmosphere can have a big impact on ocean circulation via changing temperature and salinity, and ocean circulation in turn has a major effect on the atmosphere – it’s why, for instance, the UK has a temperate climate while being north of the Canadian border in latitude.
Amy’s research also takes her on fantastic adventures. To get a sense of the history of ocean circulation, Amy studies the growth behavior of deep-sea corals. These aren’t exactly the brightly colored corals that you can snorkel to off the coast of Australia – rather, they are typically much more plain-looking, smaller, and extremely slow growing. Their slow growth is the key that lets Amy see signatures of the conditions they were growing in for decades into the past.
The most impressive expedition Amy described was diving a kilometer and a half below the sea surface inside the Alvin submersible – the same vessel which discovered the wreckage of the Titanic! In addition to the fascinating technical details of the vessel and its scientific equipment, Amy showcased the human side of diving in Alvin. As with many long-standing human endeavors, diving in Alvin has its traditions – including being doused with buckets of icy water after your first dive. It was clear from the buoyancy of Amy’s account that any hypothermia has been long forgotten.
To look at the crowd, you might think you were at a standup comedy show – cheerful, attentive faces, and full glasses all around. Mark your calendars for the next talks on January 18, when we’ll hear from a pair of UCD chemists about how chemicals can be seen as tinker toys to build useful  compounds- but be sure to get there early if you want a seat!

About the Author

Jordan Snyder is a PhD student at the University of California in Davis. For more content from the UC Davis science communcation group “Science Says“, follow us on twitter @SciSays

Our Communication Projects





Content on this page has been created with full academic freedom of expression by early career scientists at the University of California. Through our projects, Science Says early career scientists are refining effective scientific communication practices under the guidance of UC faculty. We strive to present fact-based information grounded in the primary scientific literature. If you notice any facts that conflict with the primary literature on a topic in food and ag, please send us the publication and we will review our project content to make sure we are representing the current scientific consensus. Questions, comments or suggestions should be directed tosnalbers(at)ucdavis(dot)edu. Thanks!

Introducing: Science Says!

The former SPCG is now “Science Says”!! According to news headlines, science says a lot of things, but what do we really learn from scientific studies, and how do these findings impact our daily lives?

Wading through science-related news can be difficult, but science isn’t an elite league of geniuses or a collection of hard facts. Science is a process of gathering evidence from carefully controlled tests to gain understanding of the natural world. Our goal is to empower everyone to investigate how scientific findings impact their daily lives. We’re cultivating a community of science communicators to demystify the scientific process and challenge misconceptions. So what does science really say?