Project 14. Regulation and function of R-loops in auto-immunity and sex-bias.

Figure 1. Initial cascade of immune recruitment.

Multiple sclerosis is an autoimmune disease characterized by the immune system’s misguided attack on myelinating neurons, with an onset appearance around midlife, which causes a progressive disruption of the normal central nervous system function. Over the past few years, its incidence has increased and the ratio of female to male cases has widened from 2.3 to 3.5:1. Generally, the activation of the type 1 interferon response is associated with the initiation and perpetuation of many of the reported autoimmune responses, leading to chronic inflammation and tissue damage. The cooperative function of nucleic acid-sensing proteins can trigger this cascade. Recent findings have shown that the activation of the cGAS response can extend beyond its conventional role in combating viral infections and it can serve as a sensor against the accumulation of cytosolic DNA in various contexts. Also, research conducted by the Cimprich lab has established a connection between RNA-DNA hybrids and their immunogenic properties. These hybrids aberrantly accumulate in the cytoplasm following R-loop processing, thereby linking R-loop accumulation to cancer cell death by activating the innate immune response. Intriguingly mutations within the two endonuclease genes (RNASE H1 and H2)  responsible for specifically processing RNA within the RNA-DNA hybrid cause Aicardi-Goutières syndrome, a pathology with progressive neurological deterioration similar to Multiple sclerosis but with a pediatric onset.

The project builds upon the research conducted in project 10, which aims at dissecting the vulnerability of neurons to R-loop formation as a consequence of their distinct way of employing post-transcriptional processes (e.g. splicing). Based on this, we now propose to investigate the downstream effects of excessive R-loop formation and processing in neurons in the context of pro-inflammatory responses of autoimmunity (scheme).

Specifically, we will explore the following questions:

  1. Are there differences in the hyperactivation of the cGAS pathway when R-loops are formed in neurons and can this trigger an altered self-recognition?
  2. Can a chromosomal bias in the formation of the DNA/RNA hybrids explain the sex differences in susceptibility to multiple sclerosis?
  3. What is the impact of the nutritional state on the formation and resolution of R-loops in degenerating cell types?

In our experiments, we will make use of existing gRNA/CRISPR constructs, hybrid co-cultures systems which we have established in the lab and in vivo models. With this approach, we hope to gain insights into the underlying mechanisms driving the exaggerated immune response triggered by and towards neurons and open up to understanding general principles of autoimmune disorders and sex bias.

This project will be pursued in collaboration with the Keller-Valsecchi group at the Institute of Molecular Biology (Mainz).