Investigating impact of schizophrenia-associated non-coding variants on enhancer activity using brain organoids

ended

What makes us susceptible to a genetic disease is a central question in human genetics. Although, coding mutations have revealed the mechanisms of many genetic diseases, the same approach is not adequate to unravel the etiology of complex diseases such as schizophrenia (SCZ). Genome wide association studies revealed that the majority of SCZ-associated polymorphisms map to the non-coding regions and possibly alter gene expression. However, the functional consequence of these polymorphisms on gene regulation remains largely unknown. Although the onset of SCZ symptoms occurs in late adolescence, SCZ patients show differential expression of neurodevelopmental genes and defects in neuronal maturation. Therefore, it is postulated that the SCZ phenotype is a late manifestation of defects in neurogenesis and neuronal maturation. Based on the neurodevelopmental model of SCZ, I hypothesize that these SCZ-associated non-coding variants disrupt the function of enhancers active during neurogenesis/ neuronal maturation. Therefore, using cortical organoids as an experimental system, I plan to investigate 1) Which SCZ-associated non-coding polymorphisms are located in neurodevelopmentally active enhancers. 2) Whether and how these non-coding variants affect enhancer function. To this end, I will perform massively parallel reporter assay to inspect the enhancer activity of both control and mutant sequences of SCZ-linked cis regulatory elements in the neural progenitors and neurons of the developing cortical organoids. This assay will reveal any effect of non-coding variants on the level, cell type or developmental stage of reporter transcription. This effect can be then verified by analyzing the expression of associated genes to reveal how common, low disease-risk alleles contribute to SCZ-susceptibility. Furthermore, this novel combination of organoids and functional genomics will pave the way for investigation of non-coding variation for diverse human diseases and traits.