Context-specific expression quantitative trait loci dynamics uncover genetic pleiotropy in schizophrenia

Area of Science:

• Neurogenetics
• Psychiatric Disorders
• Genomics

Background:

• Schizophrenia (SCZ) is highly heritable, but the genetic mechanisms driving its development are not fully understood.
• Non-coding genetic variants play a significant role in SCZ susceptibility, yet their functional impact remains largely unclear.
• Understanding gene regulatory dynamics in specific cellular contexts is crucial for dissecting complex genetic disorders.

Purpose of the Study:

• To investigate context-specific gene regulatory alterations in schizophrenia using expression quantitative trait loci (eQTL) analysis.
• To identify novel schizophrenia-associated genes and regulatory mechanisms, particularly those involving non-coding variants.
• To explore the role of genetic pleiotropy and chromatin modifications in schizophrenia pathogenesis.

Main Methods:

• Context-specific eQTL analysis on the BrainSeq Phase 1 dataset comparing schizophrenia cases and controls.
• Identification of differential regulatory associations and consistent eQTLs.
• Integration of eQTL data with genome-wide association studies (GWAS) and Mendelian Randomization (MR).
• Analysis of transcription factor binding sites and chromatin states (H3K27me3).
• Functional validation of candidate risk genes (e.g., ANKRD45) in neuronal differentiation models.

Main Results:

• Widespread changes in gene regulatory associations (loss and gain) were observed in schizophrenia.
• A target gene switching phenomenon, mediated by single nucleotide polymorphisms (SNPs) competing for regulatory elements, was identified.
• Pleiotropic SNPs associated with schizophrenia were enriched in repressive chromatin domains (H3K27me3) and implicated EZH2.
• Mendelian randomization prioritized ANKRD45 as a risk gene, showing disease-context regulation and affecting neuronal differentiation.
• Overexpression of ANKRD45 inhibited neuronal differentiation, while knockdown promoted it.

Conclusions:

• Context-specific eQTL dynamics are critical in the genetic architecture of schizophrenia.
• This study enhances the understanding of non-coding risk variants and their functional impact in mental illness.
• The findings highlight the importance of utilizing context-specific eQTL data to unravel complex genetic disorders like schizophrenia.