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At the Lab Episode 19: Brain sex

image of Cold Spring Harbor campus from across the harbor with At the Lab podcast logo and portrait of Jessica Tollkuhn

Depending on where your head’s at, the phrase “brain sex” might not mean what you think. On the other hand, this week’s podcast is all about hormones. In our latest edition of At the Lab, we hear from CSHL Associate Professor Jessica Tollkuhn about the role of estrogen in brain development.

Read the related story: How hormones define brain sex differences


Transcript

Caroline Cosgrove: You’re now At the Lab with Cold Spring Harbor Laboratory. I’m Caroline Cosgrove and this week At the Lab, “Brain sex.”

CC: When it comes to sex hormones, most people associate men with testosterone and women with estrogen. And there is some truth to that. But, according to CSHL neuroscientist Jessica Tollkuhn, the whole truth isn’t so black and white. In fact, it’s not really pink or blue, either. Here’s Tollkuhn:

Jessica Tollkuhn: A lot of people, even neuroscientists, are not familiar with this idea that in rodents, estrogen is actually masculinizing for the brain. This is really counterintuitive. The testes make testosterone. The ovaries make estradiol, which is the principal estrogen. But you can treat females with estradiol on the first day of birth, and they will grow up and will be territorial like the males. They still have female physiology. They’re still cycling. They can still have babies. But their brain is permanently masculinized by seeing estrogen early.

CC: This has been known for decades. What scientists didn’t understand is how a temporary hormone surge can have lifelong effects. Today’s advanced technologies have made it possible to see what’s going on at the cellular level. Tollkuhn’s team zeroed in on a particular part of the mouse brain and then went even deeper.

JT: So, there’s kind of two questions. Where are the hormone receptors binding? And then how does this relate to sex differences in the brain?

CC: Tollkun’s team was able to identify the specific genes under estrogen’s control, including many involved in brain development.

CC: Now she’s exploring the roles these genes play later in life. Her work may one day lead to new hormone replacement therapies or treatments for neurodegenerative diseases like Alzheimer’s. But it’s also eye-opening in another way. It suggests that brain sex is the product of fluctuating hormones rather than unchanging sex chromosomes.

JT: If you consider that there’s variation in hormone receptors and hormone levels and the target genes of hormones just across individuals, then you can imagine there’s this whole rainbow of different ways that the brain can be differentiated. There’s always a question of what can we learn about ourselves? Where does personality come from? So yeah, I’m excited to keep working on hormones and how they affect different aspects of the brain.

CC: And we’re excited to see what she comes up with next, At the Lab.

CC: Thanks again for listening. If you like what you heard, please subscribe wherever you get your podcasts. And visit us at CSHL.edu to get more fascinating science stories like this one. For Cold Spring Harbor Laboratory, I’m Caroline Cosgrove. And I’ll see you next time At the Lab.