Male infertility affects millions worldwide, but its underlying causes remain poorly understood. Now, an international team led by Hiroki Shibuya at Japan’s RIKEN Center for Biosystems Dynamics Research (BDR) has identified a crucial structure in male mouse germ cells. When disrupted, this structure causes defects in the sperm flagellum—the tail that allows sperm to swim.
This discovery was made possible through ultrastructure expansion microscopy, which allowed the first detailed observation of the mouse flagellar base. Researchers say it could help explain some forms of male infertility in humans. The study was published in Science Advances.
Understanding Male Infertility
Infertility often results from abnormalities in egg or sperm cells during development. In males, sperm develop through a process called spermatogenesis, which continues throughout life after puberty. While scientists understand parts of this process, the detailed molecular events at the subcellular level remain largely unknown.
“Female infertility has been studied extensively,” Shibuya says, “but male infertility—which accounts for about half of all infertility cases—remains poorly understood.”
To tackle this, the team used ultrastructure expansion microscopy, a technique that combines aspects of fluorescent and electron microscopy. Electron microscopy can capture detailed cellular images but cannot track specific proteins over time. Fluorescent microscopy can label proteins but usually cannot resolve fine subcellular structures.
Expansion microscopy solves this by embedding cells in a gel that is then physically enlarged several times. This allows researchers to use fluorescent labeling to study
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