#egg cells

Gathered about MOS

Cell division that results in an egg (and the same for sperm) from the germ cell is called meiosis (different from mitotic division that all other body cells undergo). Here in a mouse study, an enzyme called MOS has been found to be key to normal meiotic cell division. The image shows structures in a normal cell (left) undergoing meiosis – the midbody with a 'ring and cap' highlighted in magenta (DNA in white and tubulin in green) – and in a cell without MOS (right) revealing the midbody's 'cap' is absent

Read the published research article here

Image from work by Gisela Cairo, Muhammad A. Haseeb and colleagues

Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Journal of Cell Science, March 2026

Conserving Eggs

Defining sexual reproduction are germ cells – cells which, after dividing by meiosis (different from the division by all other body cells, mitosis) and maturation, become either the female's egg cells or the male's sperm. A structure involved in egg-producing meiosis called the fusome was discovered in the fruit fly decades ago, and now a similar structure has been discovered in mice. It's thought that the fusome is part of an ancient conserved process that ultimately leads to uniform egg cell production

Video made using Leica Microsystems microscopy

Read the published research article here

Video from work by Madhulika Pathak and Allan C Spradling

Howard Hughes Medical Institute Research Laboratories, Carnegie Institution for Science, DC, USA

Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in eLife, March 2026

Eggs and Oil

The role of lipid droplets in egg cell development and fertility revealed in a fruit fly model

Read the published research paper here

Image from work by Michelle S. Giedt and Jonathon M. Thomalla, and colleagues

Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA and Department of Biology, University of Rochester, Rochester, NY, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Development, June 2023

The Eggs Factor

Fertilised eggs contain hundreds of molecular ‘protein-building’ instructions called mRNAs. They need to be followed precisely in the right place, at the right time to create embryos. As egg cells, or oocytes, mature, they produce these mRNAs in preparation, but here’s the problem: accumulating these mRNAs before they're needed can hinder development. Quite a conundrum, but researchers have identified a protein that can balance being ready to spring into action with successful embryo development. Nanog is known to amplify mRNA messages in the early embryo. Now researchers have found that it helps silence pre-made mRNAs in eggs and how that impacts development. By injecting a dye (red) into fertilised oocytes, they followed how cells move during normal development (pictured). In oocytes without Nanog, this movement was more sluggish so embryos don’t develop properly. While the full extent of Nanog’s hidden talent needs to be uncovered, it’s clear that it is important for successful development.

Written by Sophie Arthur

Video from work by Mudan He and Shengbo Jiao, and colleagues

State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Wuhan, China

Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Development, December 2022

Miscounting Chromosomes

Egg cells or oocytes have unique characteristics that make them different from other cells. One of the main differences is the number of chromosomes – condensed structures of DNA. Most human cells have 46 – 23 pairs – but eggs (and sperm) have only 23. This number is critical because any more or less can lead to infertility and miscarriages. These errors occur during meiosis; specialised cell division that generates egg cells, and these errors become more common as women age, but we didn’t know why. By imaging oocytes from younger women (left) and older women (right), researchers have found that a protein called Sgo 2 (green) is vital to helping the chromosome pairs to line up correctly before being pulled apart by microtubules (orange). In older women, Sgo2 doesn’t localise to the right locations meaning that the chromosomes are not lined up correctly for the big divide, increasing the chances of older eggs not meeting that magic number of chromosomes.

Written by Sophie Arthur

Image from work by Bettina P Mihalas and colleagues

The Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh, UK

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in bioRxiv, January 2023 (not peer reviewed)

From Biomedical Picture of the Day; March 8, 2017:

Over Egged

It’s a complex business, making ovaries – the organs that hold female egg cells. It’s important to get the right balance of egg cells to supporting cells, and this is controlled by a number of genes all working together. These images show two very different ovaries, both taken from tiny fruit flies and viewed down a microscope. The one on the left is healthy, with the developing eggs stained blue and the supporting cells colored green. But the one on the right comes from a fly that has an overactive version of a gene called c-Fos. Rather than neat rows of maturing egg cells, it’s a mess of green supporting cells surrounding degraded and useless eggs. Unsurprisingly, these flies are infertile. Figuring out how c-Fos works together with other genes to create egg cells is an important step in understanding infertility, not just in flies but maybe also in humans too.