Tough as Eggs

Roughly 300,000 – that’s how many eggs the average female has at puberty. Most won’t even make it as far as being released from the ovaries but they need to be equipped to survive the journey in case they are released. One way eggs protect themselves is through their outer layer called the zona pellucida. It contains four proteins, ZP1–4. The first three have been studied in mice to uncover their function. However, mice don’t have ZP4, so to investigate its function researchers turned to rabbits. They created mutants lacking ZP4 in their eggs. Microscopy revealed the mutant eggs had thinner, rougher zonae pellucidae. What’s more, they were less robust when prodded, deforming easily as captured using video microscopy (pictured, bottom) compared to normal eggs (top) that quickly regained their shape. The mutant rabbits were also much less fertile. More digging into ZP4 may, therefore, provide insights into human infertility.

Written by Lux Fatimathas

Lux Fatimathas

Writer

Having pursued science through a career in research, communications and publishing, she is currently a writer and editor for a healthcare marketing agency and also juggles freelance science writing.

• Video from work by Ismael Lamas-Toranzo and colleagues
• Animal Reproduction Department, INIA, Madrid, Spain
• Image originally published under a Creative Commons Licence (BY 4.0)
• Published in eLife, October 2019