Scientists Hear Cell Conversation For First Time

A cutting edge technique that allows scientists to monitor communication between cells could transform the way laboratory medical experiments are conducted. The method is likely to make laboratory studies of cancers and other human diseases, and assessment of new drugs to target them, more accurate.

The study was completed by Dr Rune Linding, head of the Cellular and Molecular Logic Team at The Institute of Cancer Research (ICR) in the UK, along with UK and Canadian-based colleagues. The research is published in the latest edition of the journal Science.

Dr Linding says that understanding communication between cells is crucial, as many cancers and other diseases are caused by a breakdown in communications systems.

"Organs and tissues are composed of many different cell types with distinct roles to play," Dr Linding says. "To function properly, the cells must communicate with each other, which they do through a network of specialised proteins known as signalling molecules. When cells are unable to send or receive the correct signals, they can behave abnormally and this can lead to disease."

Until now, scientists have generally studied cell communication by taking a single population of cells, adding a molecule to stimulate the cells and measuring the level of signalling molecules produced. But this technique does not take into account that cells respond to the signals they receive and feedback to each other, like a conversation between people.

"In our latest study, we have developed a way to more accurately replicate what's happening in the body - before scientists could only hear a monologue, but now for the first time we can assess the outcome of a conversation," Dr Linding says.

The new method involves growing cells in media containing labelled amino acids (the fundamental building blocks of proteins) that are incorporated into the cells' proteins. Two cell types, grown with different labels, are then combined for a short time to allow them to talk to each other, and then the cells are broken open so the proteins produced can be examined. A technique called mass spectrometry is then used to measure the level of each label, showing from which cell type the proteins originated.

The team then looked for genes that were involved in the conversation. They tested about 10 per cent of all human genes by blocking them within the cells one by one, using small interfering RNA molecules, and measured whether the cells behaved differently. Information about the proteins and genes was used to make a computer model of the signalling networks involved - effectively highlighting the important points in the conversation.

The research team first used this technique to study a key communications system known as EphB2, which is used to position cells precisely within the body and is important for maintaining boundaries between tissues. Cancer cells need to cross tissue boundaries to spread throughout the body, so a mutation in this system can promote metastasis.

Co-author Dr Claus Jørgensen from The Samuel Lunenfeld Research Institute of Mount Sinai Hospital in Canada says: "Many types of cancers - including colorectal cancer, lung, prostate and breast cancer and glioma - have an abnormality in the Eph communications system, and it may also play a role in other diseases. However, until now it has not been possible to study this network during cell-to-cell contact, the most crucial time".

"Our study identified several new molecules involved in this system, knowledge that may play a role in future network biology-based drug development at the ICR. Perhaps most importantly, we found that the two cell types we studied responded differently to the conversation, which shows that previous experiments on just one cell type could well be inaccurate. This means that if you want to measure how cells will respond to signals - including signals that trigger cancer, or signals from drugs - you need to look at how they will respond when they are with other cell populations, not just one cell type alone."

Co-author Dr Tony Pawson, also from The Samuel Lunenfeld Research Institute, says: "This technique, which lets us consider two cell populations at once, is a major step towards more accurate laboratory research. We will adopt this approach to study how distinct cell populations talk to one another in diseases like cancer; the next stage is to find a way to take even more cell types and molecules into account. We can't mimic what goes on in the body yet, but we are getting closer."

Funding for this project came from the ICR, the Medical Research Council, Genome Canada through the Ontario Genomics Institute, a Terry Fox Programme grant from the Canadian Cancer Society, the Canadian Institutes for Health Research, the Canada Foundation for Innovation, the Human Frontiers Science Program and The Lundbeck Foundation.

Source
The Institute of Cancer Research

EMBL Scientists Uncover The Gene Responsible For Keeping Females Female

Is it a boy or a girl? Expecting parents may be accustomed to this question, but contrary to what they may think, the answer doesn't depend solely on their child's sex chromosomes. Scientists at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany and the Medical Research Council's National Institute for Medical Research (NIMR) at Mill Hill, UK discovered that if a specific gene located on a non-sex chromosome is turned off, cells in the ovaries of adult female mice turn into cells typically found in testes. Their study, published in Cell, challenges the long-held assumption that the development of female traits is a default pathway. At the same time, it grants a valuable insight into how sex determination evolved.

In humans and most other mammals, an individual's sex is determined by its sex chromosomes: females have two X chromosomes, males have one X and one Y. Scientists had long assumed that the female pathway - the development of ovaries and all the other traits that make a female - was a kind of default: if it had a gene called Sry, which is located on the Y chromosome, an embryo would develop into a male, if not, then the result would be a female. But in adult animals it is the male pathway that needs to be actively suppressed, as Mathias Treier and his team at EMBL discovered.

A gene called Foxl2, which is located on an autosome - a chromosome other than the sex chromosomes - and therefore present in both sexes, was known to play an important role in the female pathway, but its precise function remained elusive. To elucidate the matter, Treier and colleagues ablated, or 'turned off', this gene in the ovaries of adult female mice.

"We were surprised by the results," says Treier, "We expected the mice to stop producing oocytes, but what happened was much more dramatic: somatic cells which support the developing egg took on the characteristics of the cells which usually support developing sperm, and the gender-specific hormone-producing cells also switched from a female to a male cell type."

Thus, the scientists discovered that Foxl2 plays a crucial role in keeping female mice female.

Teaming up with the group of Robin Lovell-Badge at the NIMR, they were able to decipher together the underlying molecular mechanism. They showed that FOXL2 and estrogen receptor act together by repressing a DNA element called TESCO that Lovell-Badge's group had previously identified to regulate expression of the testes-promoting gene Sox9. Sox9 was known to function in the embryo to make the early gonads become testes rather than ovaries, but the new studies suggest that it can perform the same task in the adult. FOXL2 is therefore critical to keep Sox9 turned off in ovaries throughout life.

"As most vertebrates have Foxl2, estrogen receptors and Sox9," Lovell-Badge explains, "this mechanism for maintaining female traits probably appeared early on in the evolution of vertebrates, while Sry and the mammalian Y chromosome are relatively new inventions."

These findings will have wide-ranging implications for reproductive medicine and may, for instance, help to treat sex differentiation disorders in children, for example where XY individuals develop as females or XX as males, and understand the masculinising effects of menopause on some women.

The study is discussed by author Mathias Treier in an online video in Cell's 'PaperFlicks' series, which is also available on YouTube.

Source: Sonia Furtado
European Molecular Biology Laboratory