Using the novel genome editing technique, CRISPR, a team of researchers at the Wellcome Sanger Institute have isolated the genes involved in regulating T helper cell activation. The study, conducted in mice using T helper type 2 (Th2) cell lines, was recently published in the journal Cell.
The immune system is the body’s protection mechanism against infectious organisms and foreign invaders. T cells are central players in determining a successful outcome in response to such organisms, and therefore the ability to manipulate and even enhance their activation has a wide spread application in the field of medicine.
In order to provide the appropriate immune response, T helper cells must differentiate into one of two subtypes, T helper 1 (Th1) and T helper 2 (Th2). “Until now, there has been no systematic understanding of T cell activation and differentiation, processes which are crucial for the immune system.” explains Sarah Teichmann, from the Wellcome Sanger Institute and senior author of the paper.
Why has determining the processes underlying T cell differentiation proven so challenging up until now? "In the past, immunologists have been investigating Th2 mostly one gene at time.” comments Xi Chen, joint first author from the Wellcome Sanger Institute, in a recent press release. CRISPR technology enables scientists to target and cut a cell’s genome at a desired location, providing the unique opportunity to remove and explore the role of all the specific genes within one cell. “In this study, we developed a new retroviral CRISPR library, which has enabled us to efficiently knock-out each individual gene in mouse T helper cells for the first time.”, Chen adds.
The research team created a genome-wide CRISPR library of 88,000 guides, enabling them to effectively regulate each of the 20,000 genes in mouse Th2 cells. They then subjected the cultured Th2 cells to a mimicked infection and observed the response when switching off individual genes. Their findings highlight a variety of genes involved in regulating Th2 development, both verifying the role of those recognized in previous work, and identifying novel factors, such as Pparg and Bhlhe40.
“The actual screening was carried out in just 6 months. This technology can now be used to investigate other targets very efficiently.” says Teichmann. Thus, in addition to fulfilling their research aim of exploring immune system regulation, the scientists have further refined the experimental processes in CRISPR methods.
Teichmann adds that there are plans to continue this work beyond the scope of animal models and in a variety of cell types. “My current team has now mainly focused on human studies. Henriksson will be using this technology to model how T cells (not just Th2) behave during immune response in different infection models. Chen will utilize this library to combine CRISPR screening with single cell ATAC-seq to study key factors that affect chromatin accessibility during cellular differentiation.”
Sarah Teichmann was speaking to Molly Campbell, Science Writer for Technology Networks.
Henriksson, J., Chen, X., Gomes, T., Ullah, U., Meyer, K., Miragaia, R., Duddy, G., Pramanik, J., Yusa, K., Lahesmaa, R. and Teichmann, S. (2019). Genome-wide CRISPR Screens in T Helper Cells Reveal Pervasive Crosstalk between Activation and Differentiation. Cell. DOI:https://doi:10.1016/j.cell.2018.11.044.