News from the Department of Genetics

In a study in mice, researchers have identified genes associated with the dramatic transformation of the mammary gland in pregnancy, breastfeeding, and after breastfeeding as it returns to its resting state.

Their results form the most detailed atlas of genetic expression ever produced for the adult developmental cycle of the mammary gland. They are published today in the journal Nucleic Acids Research.

The mammary gland is made up of different cell types, each with a different function - such as fat cells that provide structural support, and basal cells that are crucial for milk ejection.

The team analysed the cellular composition of the mammary gland at ten different time-points from before the first pregnancy, during pregnancy, during breastfeeding, and during a process called involution when the breast tissue is remodelled to its resting state. The mix of cell types changes dramatically through this cycle.

By measuring gene expression in the mammary gland over the same time-points, the researchers were able to link specific genes to their functions at different stages of the developmental cycle.

“Our atlas is the most detailed to date, allowing us to see which genes are expressed in which cell types at each stage of the adult mammary gland cycle,” said Dr Geula Hanin, a researcher in the University of Cambridge’s Department of Genetics, first author of the report. 

The team found that genes associated with breastfeeding disorders such as insufficient milk supply are active not only in the breast cells that produce milk, but also in other cells such as basal cells - which squeeze out the milk as the infant is suckling. This suggests that in some instances, a mechanical problem - rather than a milk production problem - could be the cause and provides a new cell target for investigation.

The study also found that genes associated with postpartum breast cancer become active immediately after weaning in various cell types - including in fat cells, which have previously been overlooked as contributors to breast cancer linked to childbirth. This offers a future potential target for early detection or prevention strategies.

Hanin said: “We’ve found that genes associated with problems in milk production, often experienced by breastfeeding mothers, are acting in breast cells that weren’t previously considered relevant for milk production. We’ve found genes associated with postpartum breast cancer acting in cells that have been similarly overlooked.

“This work provides many potential new ways of transforming maternal and infant health, by using genetic information to both predict problems with breastfeeding and breast cancer, and to tackle them further down the line.”

Breastfeeding affects lifelong health, for example breast-fed babies are less likely to become obese and diabetic. Yet one in twenty women have breastfeeding difficulties, and despite its importance this is a greatly understudied area of women’s health.

Postpartum breast cancer occurs within five to ten years of giving birth and is linked to hormonal fluctuations, natural tissue remodelling, and the changing environment of the mammary gland during involution that makes it more susceptible to malignancy.

The researchers also focused on ‘imprinted genes’- that is, genes that are switched on or off depending on whether they are inherited from the mother or the father. Imprinted genes in the placenta are known to regulate growth and development of the baby in the womb.

The team identified 25 imprinted genes that are active in the adult mammary gland at precise times during the development cycle. These appear to orchestrate a tightly controlled system for managing milk production and breast tissue changes during motherhood.

Some functions of the genes themselves have been identified in previous studies. This new work provides a detailed understanding of when, and where, the genes become active to cause changes in mammary gland function during its adult development cycle.

“Breastfeeding is a fundamental process that’s common to all mammals; we wouldn’t have survived without it. I hope this work will lead to new ways to support mothers who have issues with breastfeeding, so they have a better chance of succeeding,” said Hanin.

The research was funded primarily by the Medical Research Council.

Hanin co-leads the Cambridge Lactation Network and is a member of Cambridge Reproduction. 

Reference: Hanin, G. et al: ‘Dynamic Allelic Expression in Mouse Mammary Gland Across the Adult Developmental Cycle.’ Nucleic Acids Research, September 2025. DOI: 10.1093/nar/gkaf804

Learn more about the University's research into Women's Health.

A University of Cambridge study of adult mammary gland development has revealed new genes involved in breastfeeding, and provided insights into how genetic changes may be associated with breastfeeding disorders and postpartum breast cancers.

This work provides many potential new ways of transforming maternal and infant health, by using genetic information to both predict problems...and to tackle them further down the line.Geula HaninAlexandr Kolesnikov, GettyMother breastfeeding her baby

The text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

YesLicence type: Attribution

A new study suggests that our ancestors’ close cohabitation with domesticated animals and large-scale migrations played a key role in the spread of infectious diseases.

The team, led by Professor Eske Willerslev at the Universities of Cambridge and Copenhagen, recovered ancient DNA from 214 known human pathogens in prehistoric humans from Eurasia.

They found that the earliest evidence of zoonotic diseases – illnesses transmitted from animals to humans, like COVID in recent times – dates back to around 6,500 years ago, with these diseases becoming more widespread approximately 5,000 years ago.

The study detected the world’s oldest genetic trace of the plague bacterium, Yersinia pestis, in a 5,500-year-old sample. The plague is estimated to have killed between one-quarter and one-half of Europe’s population during the Middle Ages.

In addition, the researchers found traces of many other diseases including:

Malaria (Plasmodium vivax) – 4,200 years ago

Leprosy (Mycobacterium leprae) – 1,400 years ago

Hepatitis B virus – 9,800 years ago

Diphtheria (Corynebacterium diphtheriae) – 11,100 years ago

This is the largest study to date on the history of infectious diseases and is published today in the journal Nature.

The researchers analysed DNA from over 1,300 prehistoric humans, some up to 37,000 years old. The ancient bones and teeth have provided a unique insight into the development of diseases caused by bacteria, viruses, and parasites.

“We’ve long suspected that the transition to farming and animal husbandry opened the door to a new era of disease – now DNA shows us that it happened at least 6,500 years ago,” said Willerslev.

He added: “These infections didn’t just cause illness – they may have contributed to population collapse, migration, and genetic adaptation.”

The significant increase in the incidence of zoonoses around 5,000 years ago coincides with a migration to north-western Europe from the Pontic Steppe – that is from parts of present-day Ukraine, south-western Russia and western Kazakhstan. The people embarking on this migration – and who to a large extent passed on the genetic profile found among people in north-western Europe today – belonged to the Yamnaya herders.

The findings could be significant for the development of vaccines and for understanding how diseases arise and mutate over time.

“If we understand what happened in the past, it can help us prepare for the future. Many of the newly emerging infectious diseases are predicted to originate from animals,” said Associate Professor Martin Sikora at the University of Copenhagen, and first author of the report.

Willerslev added: “Mutations that were successful in the past are likely to reappear. This knowledge is important for future vaccines, as it allows us to test whether current vaccines provide sufficient coverage or whether new ones need to be developed due to mutations.”

The sample material was primarily provided by museums in Europe and Asia. The samples were partly extracted from teeth, where the enamel acts as a lid that can protect the DNA against degradation as a result of the ravages of time. The rest of the DNA was primarily extracted from petrosa bones - the hardest bone in humans - located on the inside of the skull.

The research was funded by the Lundbeck Foundation.

Reference

Sikora, M. et al: ‘The spatiotemporal distribution of human pathogens in ancient Eurasia.’ Nature, July 2025. DOI: 10.1038/s41586-025-09192-8

Adapted from a press release by the University of Copenhagen.

Researchers have mapped the spread of infectious diseases in humans across millennia, to reveal how human-animal interactions permanently transformed our health today.

We’ve long suspected that the transition to farming and animal husbandry opened the door to a new era of disease – now DNA shows us that it happened at least 6,500 years agoEske WillerslevMarie Louise JørkovLate Neolithic skull from Madesø

The text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

YesLicence type: Attribution-Noncommerical

A team at Cambridge is helping to drive biological discovery through innovation in microscope technologies