CRISPR screen unveils enzyme target for inflammatory diseases

Researchers at Vanderbilt University, US, have been using the CRISPR-based screen Sugiura to explore multiple sets of genes in various disease models and recently discovered that inhibiting or genetically deleting the enzyme, called MTHFD2, reduced disease severity in multiple inflammatory disease models. 

In the study, published in Immunity, the team focused on “one-carbon” metabolism, a series of reactions that generates chemical building blocks for the biosynthesis of DNA and other molecules. “One-carbon metabolism has been a target for drug development for years and years, but it really has not been explored in an unbiased way,” explained Professor Jeffrey Rathmell who led the study. 

To systematically study the pathway in T cells, researcher Dr Ayaka Sugiura developed a screening strategy using CRISPR. She designed CRISPR “guides” to selectively inactivate each gene in the one-carbon metabolism pathway and introduced this “library” into isolated T cells, controlling the experimental conditions so that each cell had only one or no inactivated gene. 

By studying the modified cells in an animal model of asthma, Sugiura was able to identify genes important to T cell function. She then examined the expression of each identified gene during T cell development and in patients with a variety of inflammatory diseases. 

MTHFD2 stood out as it was highly expressed in disease states and during embryonic development, but it was expressed at low levels, or not at all, in adult tissues. “MTHFD2 is important for nucleotide synthesis not only for DNA, but also for proper signalling required for T cell function,” Sugiura continued. Inhibiting MTHFD2 with a drug or genetically eliminating it reduced overall proliferation of CD4 T cells and blunted immune responses. 

Furthermore, the researchers discovered that the effects of MTHFD2 inhibition were different for subsets of CD4 T cells that are generated in response to antigen stimulation. Inhibiting MTHFD2 also promoted the activity of regulatory CD4 T cells (Treg) and blocked inflammatory CD4 T cells (Th17) and converted them to an anti-inflammatory phenotype. 

In animal models for multiple sclerosis, inflammatory bowel disease, and a general allergic response, inhibiting or eliminating MTHFD2 reduced disease severity. According to the researchers, these findings support its potential as a therapeutic target for anti-inflammatory drug development.