PhD defence: Deconstructing the Mammalian Sperm’s Molecular Motor

PLEASE NOTE: The candidate gives a layman's talk, therefore the livestream will start fifteen minutes earlier.

Mammalian sperm cells are biological marvels designed for one mission: traveling vast distances to fertilize an egg. To navigate viscous fluids and reach their target, they rely on a specialized tail called a flagellum that acts like a powerful propeller.

This research mapped the tail's microscopic architecture using advanced imaging at the molecular level. The study discovered that these tails vary between species and possess complex internal asymmetries essential for generating the right waveform and torque to propel the cell forward. Furthermore, the flagellum interior contains over 60 different proteins acting as internal braces, reinforcing it against swimming stresses.

However, before sperm enter the female reproductive tract, they must first "learn" to swim. Though appearing fully formed when leaving the testis, they are initially motionless. During epididymal maturation, their internal engines activate. Surprisingly, the research found that as sperm gain the ability to move, their overall energy consumption actually decreases. To understand this paradox, scientists examined the tiny motor proteins (dyneins) responsible for movement. They discovered that these motors shift from a "locked" state to a "primed," ready-to-go state as sperm mature, enabling swimming.

This thesis establishes a multi-scale structural blueprint of the mammalian sperm flagellum, linking microscopic anatomy to atomic-scale protein interactions. By revealing how the sperm's molecular motor is built and refined, these findings provide a foundation for understanding male infertility and identifying novel targets for contraception.