Deciphering donor- and cell-type-specific interactions between schizophrenia risk variants

• Applicant: Dr. Kristina Rehbach
• Subject Area: Biological Psychiatry ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2020 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 446148624

Schizophrenia (SZ) has a lifetime prevalence of 1%, in addition to symptoms of psychosis, the disorder also frequently leads to an inability to maintain relationships, unemployment, addiction, and homelessness. Treatment resistance occurs in approximately one-third of cases; even when effective, antipsychotics address hallucinations and delusions, but fail to tackle social disengagement or cognitive symptoms. SZ is a highly heritable polygenic disorder; risk arises through interactions between over 145 SZ common risk loci of small effect in several distinct brain cell types. Scientific Premise: Although the impact of penetrant rare variants to brain disease risk has been highly explored, such mutations are found in a minority of patients; in fact, a substantial portion of SZ risk is conferred by common SNPs with small effect sizes. Our overarching hypothesis is that the additive impact of any common risk variant is dependent upon the existing risk factors already present in a given individual. Here, our short-term goal is to explore the extent to which the functional impact of one such variant, FURIN rs4702, varies between donors and neural cell types. We propose to engineer a single risk variant, rs4702, in human pluripotent stem cells (hiPSCs) with high and low polygenic risk score (PRS) donor backgrounds. Our long-term objective is to improve our overall understanding of the functional impact of the myriad risk variants linked to SZ. We propose to apply a validated CRISPR-based strategy to edit rs4702, a SZ-GWAS SNP located in the 3’UTR of FURIN, in three low and three high PRS hiPSCs. Our preliminary data demonstrated the functional effect of allelic conversion of rs4702 in hiPSC-derived neurons from two control donors with average PRS (Aim 1) . With these isogenic pairs, we will generate the neural subtypes most strongly associated with SZ, namely glutamatergic neurons, GABAergic neurons and astrocytes, in order to investigate the impact of rs4702 on FURIN expression during neural development and maturation. Our preliminary data suggests that the effect of rs4702 on FURIN expression is cell type-specific and maturation dependent (Aim 2).We propose to contrast the functional effects of FURIN rs4702 in low and high PRS donor backgrounds using MEA analysis, high-content imaging and RNA-seq analysis. Our preliminary data suggests that the impact of rs4702 on neuronal activity is greatest in high PRS neurons (Aim 3).Combining hiPSC disease modeling and genome editing makes functional genomic studies of common risk variants across donor backgrounds possible. Our proposal will not only uncover the effect of common variant rs4702 across neural cell types, but also explore the extent to which interactions between risk variants alters the functional impact of rs4702. The translational impact of our work is to improve diagnostics, predict clinical trajectories and develop novel therapeutic interventions to prevent or reverse disease course.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professorin Kristen Brennand, Ph.D.