MECHANISMS OF SPERM-SR INTERACTIONS

There are many interacting factors at play between insemination and fertilization that can influence reproductive success, including the physical, chemical (together, physicochemical), or molecular features of the female reproductive tract (FRT) and seminal fluid. My long-term goal is to understand the physicochemical, environmental, and genetic regulation of sperm movement within the FRT. Despite their critical role in reproduction, dynamic communications between sperm and FRT tissues are difficult to unravel, due to challenges both in direct visualization of sperm in live adult females, and in experimentally isolating the male- and female-derived factors that regulate gamete interaction. To overcome these challenges, I have assembled a team of biologists (Cassandra Extavour) and engineers (Megan Leftwich, Zhenyu Li) to develop in vitro and in vivo models of sperm motility within the female reproductive tract.

With these models, we will identify factors that affect sperm motility and behavior, characterize the fluid dynamic environment of the FRT, and observe sperm dynamics over time within the living fly. These novel methods will allow us to develop an investigative framework to iteratively generate, test, and refine hypotheses about the mathematical, structural, physicochemical, and genetic principles that govern how sperm swim in their natural environment.

We will develop and test in vitro and in vivo models of the FRT. We will use microfluidic chips to identify and characterize structural FRT parameters critical for sperm function (Model 1) and use enlarged 3D printed models to elucidate how FRT structure drives fluid dynamics (Model 2). We will also perform long-term observations of sperm dynamics within the FRT, using the Bellymount system for long-term live imaging of functioning adult organs in situ (Model 3). These innovative approaches will allow us to systematically characterize the male and female factors that regulate these interactions, with a focus on how sperm behave within the SR to understand mechanisms of post-copulatory sperm selection.