No, that’s not a bird’s-eye view of the Earth at night. Those glowing green lines connecting each dot aren’t highways. And the big dots aren’t cities or towns either. But there are power lines and, in a way, it is still a map. What you’re looking at is a close-up view of neural circuits deep inside a region of the brain called the hypothalamus. The image comes to us from the lab of Cold Spring Harbor Laboratory Associate Professor Jessica Tollkuhn.
The hypothalamus is the almond-sized control center of the brain. It keeps the body in a stable state called homeostasis. It does this by coordinating involuntary functions like body temperature, heart rate, and even sex drive. The hypothalamus also releases hormones to trigger processes like muscle and bone growth, ovulation, and sperm production. But this isn’t a one-way street. Hormones from other parts of the body have their own effects on the brain as well.
The sex hormones estrogen and testosterone play essential roles during early brain development. They shape neural circuitry, the “power lines” seen above, helping to define brain sex differences soon after birth. Estrogen in particular helps set the stage for energy balance, mood, and behavior throughout life. However, levels of these hormones naturally decrease over time. This has been linked to cognitive decline and age-related neurodegenerative diseases like Alzheimer’s and Parkinson’s.
In 2022, Tollkuhn and her team discovered the genes in mice that estrogen targets during early development. Both male and female brains contain estrogen. But in males, it’s generated by a surge of testosterone that causes certain regions of the brain to grow larger and contain more cells than in females. This difference affects various behaviors in adulthood like mating, parenting, and aggression.
Tollkuhn and her team are now working to identify the genes testosterone regulates in the brain. And they’re tracking the roles of hormone-regulated genes later in life. Their work could lead to better hormone replacement therapies and new strategies to protect against age-related neurodegenerative diseases.
Written by: Nick Wurm, Communications Specialist | wurm@cshl.edu | 516-367-5940
