As with people, identity is vital to cells. When a cell loses its identity, it can stop working properly and a range of illnesses can result. The immune system, which protects our bodies from disease, includes cells with many different identities. When these cells lose their identity it can cause certain cancers or increase the risk of infections.

Complex networks of signals and genes create and maintain the identity of different cells. New research from the Babraham Institute, Cambridge and the University of Birmingham has revealed how a protein called ZFP36L1 helps cells known as marginal zone B cells (MZ B cells) to maintain their identity.

For cells, identity describes how they are adapted to have a specialised function. Blood cells are specialised for transportation, nerve cells for communication and the immune system fights infections. Each cell becomes specialised to do its job as a result of unique combinations of genetic instructions, which influence how the cell works.

MZ B cells play an important role in the early stages of preventing infection, by screening blood that passes through the spleen for signs of invading germs that might cause an illness. Without these cells, our body would be at much greater risk of illness.

In a paper in the journal Nature Immunology, the team, led by Dr Martin Turner showed that, by blocking the translation of certain genetic instructions, ZFP36L1 helps MZ B cells to keep the correct identity. By working together with Professor Gurdyal Besra and Dr Adam Cunningham in Birmingham, the team have shown that ZFP36L1 ensures MZ B cells continue to communicate, move and interact correctly.

Many proteins that control the identity of cells act by interacting with DNA to switch genes on or off – silencing key genetic instructions. ZFP36L1 is different, it doesn’t shut down the genes but instead it stops their messages getting through to the rest of the cell.

Genes act as stores of information, but to have an effect on the cell they must be switched on. These active genes produce molecular messages called mRNA, which carry their instructions to other parts of the cell, where the instructions they carry are used to make proteins. Through proteins, genes influence how cells work. In MZ B cells, ZFP36L1 stops certain mRNA messages from getting through. This means the cells don’t produce certain proteins that could change their identity.

As lead author on the paper Rebecca Newman, now a post–doctoral scientist at the Francis Crick Institute in London explained: “ZFP36L1 plays an important role in MZ B cells by controlling the levels of mRNA from genes such as IRF8 and KLF2. If ZFP36L1 is lost, MZ B cells leave the marginal zone of the spleen and many of them die.”

The paper’s senior author and Head of the Lymphocyte Signalling and Development research programme at the Babraham Institute, Martin Turner said: “Our immune system contains many different types of cells with unique roles. Extremely complex processes govern the development and function of each of these cell types. This study adds to our understanding of the multi–level control over cellular identity for cells in the immune system.”

This work highlights the importance of proteins like ZFP36L1, which regulate multiple mRNA messages. Further understanding how ZFP36L1 and other similar proteins function and are controlled in MZ B cells could be important in autoimmune diseases – where the immune system attacks the rest of the body – and certain types of lymphoma.