Day 2 Keynote: The Underlying Basis of Parenting and Socialization
Sunday's events finally finished with a keynote lecture from Catherine Dulac, a distinguished professor and former chair of Molecular and Cellular Biology at Harvard. Before becoming a professor, she studied pheromones at Columbia under Richard Axel (who advised my mentor as well).
At Harvard, she has spent most of her career studying two topics that naturally dovetail with pheromones: social interaction and sex-specific behavior. I can hardly recount all the topics she covered in their true depth and breadth, and summarizing them while doing them justice is near-impossible. However, I can give the most important takeaways from her most impactful work over the years, which I will try (and likely fail) to do below.
First, the vomeronasal organ (VNO) controls sex-specific behavior in mice. The VNO is a specialized structure in mice that allows them to smell pheromones, which animals emit as reproductive and social signals: for example, a female in heat attracts males by giving off specific pheromones, making them aware of their reproductive availability. These perceptions are dependent on one gene, TRP2, and its absence causes both males and females to lose their sex-specific behavior. Males will try to court and mate with other males, and females will attempt to mount other females.
The vomeronasal organ.
However, females will also stop lactating and lose their ability to care for their children, instead opting to kill their children, something males tend to do instead. This leads to another important insight. While males can only perform male-specific behaviors, females can do both. The vomeronasal organ ensures they act like females, but without it, they fall back on male behaviors.
Second, actual control is exerted in the brain using just a few hormones. A hormone called oxytocin is required for females to prefer male mates, even if the vomeronasal organ works: if oxytocin signaling is lost, females lose their preference for males, no matter what. Further, if oxytocin signaling is manipulated in males, their mate choices change as well. Sexual and mating behavior also depends on LHRH, a hormone controlling the reproductive system. When LHRH activity changes, so does mating behavior as well.
Third and finally, these functions can be localized to a few regions of the brain. Later research clarified that oxytocin is required in the medial amygdala for these effects, not the entire brain. All of the required hormones were also released from the hypothalamus: an understanding of the hypothalamus could then allow understanding of these behaviors as well.
A map of the median preoptic hypothalamus using MERFISH.
As a result, she has most recently been studying the molecular and spatial composition of the hypothalamus. Using single cell RNA-sequencing, her lab was able to identify all of the major cell types in the median preoptic hypothalamus, which controls the release of many different hormones. They then used MERFISH, a massively multiplexed RNA detection method, to look at these cells spatially. Through these methods, they were able to produce this complete map of this part of the hypothalamus.
Over the course of Dulac’s career, she has contributed so much to neuroscience, in behavior, anatomy, and molecular biology. Her lecture serves to make this more salient than ever, while communicating these key findings in one of the most effective manners I have ever seen.