Sac in Time

Every pregnant woman knows that her waters breaking are a definite sign a baby is coming. Up until then a bag of nourishing chemicals, known as the amniotic sac, surrounds the new life. The sac bursts just before labour, but how it first develops is a little mysterious. Grown in a dish from human pluripotent stem cells, this 'embryoid' mimics cellular changes that happen when an embryo first implants in the womb. Cells (with their nuclei stained blue) organise themselves into a hollow ball shape called a cyst. The red-coloured cells are using a tell-tale embryonic gene called Oct4 – similar cells in the womb contribute to the embryo itself. At the top of the cyst (with its inner surface stained green) cells form a tough skin of amnion, defining the shape of the amniotic sac and producing a model that scientists can use to study development and fertility.

Written by John Ankers

John Ankers

Writer

A former researcher in systems biology, John is now an online biology tutor and professional coach supporting the wellbeing of scientists and NHS professionals. He's writing, too, of course.

Website

• Image from work by Yue Shao and Kenichiro Taniguchi, and colleagues, University of Michigan
• Departments of Mechanical Engineering and Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
• Image copyright held by the original authors
• Research published in Nature Communications, August 2017