Interactome analysis reveals ZNF804A, a schizophrenia risk gene, as a novel component of protein translational machinery critical for embryonic neurodevelopment
Open Access
- Author:
- Zhou, Yijing
- Graduate Program:
- Molecular, Cellular and Integrative Biosciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- August 21, 2017
- Committee Members:
- Yingwei Mao, Dissertation Advisor/Co-Advisor
Yingwei Mao, Committee Chair/Co-Chair
Timothy J Jegla, Committee Member
Gong Chen, Committee Member
Wendy Hanna-Rose, Outside Member - Keywords:
- schizophrenia
- Abstract:
- Schizophrenia (SCZ) is a chronic, debilitating mental disorder that affects approximately 1% of the population. The symptoms of SCZ fall into three categories: positive, negative, and cognitive. Current understanding attributes SCZ to both genetic and environmental determinants, supported by clinical and experimental evidence. Earlier genetic studies of SCZ have focused on monogenetic factors and family studies. Entering the new millennium, genome-wide association studies (GWASs) started to be used to find the disease-associated loci on the meta-genomic scale. Single nucleotide polymorphism (SNP) rs1344706, localized in the gene ZNF804A, was the first SNP identified to achieve genome-wide significance for psychosis. Several follow-up GWASs have validated the association of rs1344706 with SCZ and other psychosis in different populations. Although the association with SCZ has been reported since 2008, the molecular function of ZNF804A remains largely unclear. In our study, we found that ZFP804A (the rodent homolog of ZNF804A) expression is high in the embryonic mouse brain but decreased in the adulthood. We proved that proper expression level of ZFP804A is essential for normal neuronal migration. We also noticed decreased neural progenitor cell (NPC) proliferation and differentiation caused by insufficient ZFP804A. To unbiasedly elucidate its molecular functions, we conducted a yeast two-hybrid (Y2H) screening and identified novel proteins that interact with ZNF804A. The gene ontology (GO) enrichment analysis revealed two major functions of ZNF804A interacting proteins: cellular adhesion/cytoskeleton regulation and translation control. In sucrose gradient fractionation assay, ZNF804A co-fractionates with translational machinery and modulates the translational efficiency potentially through the mechanistic target of rapamycin (mTOR) pathway. Using Duolink® proximity ligation assay (PLA), we confirmed the interaction between ZNF804A and ribosomal protein SA (RPSA). A proper level of RPSA is critical for optimal translation efficiency. Overexpression of RPSA rescues the migration and translation defects caused by Zfp804a knockdown. On the other hand, RPSA also serves as a receptor for laminin and presence of laminin in the extracellular matrix (ECM) augments the interaction between RPSA and ZNF804A. This implies that the function of ZNF804A might be regulated by extracellular cues. In addition, ZFP804A target RNA was identified with RNA-immunoprecipitation - RNA sequencing (RIP-seq). ZFP804A is physically associated with transcripts involved in ribosomal and mitochondrial functions. This suggests that ZFP804A might regulate translation through multiple mechanisms: direct involvement as a part of translational machinery; indirect contribution by regulating the expression level of other components of translational machinery. The role of ZNF804A in regulating translation efficiency of target transcripts is confirmed by Duolink® PLA. Among the ZNF804A bound transcripts, neurogranin (Nrgn) has been associated with SCZ in previous GWAS study (S. W. G. o. t. P. G. Consortium, 2014). Nrgn has been implicated in regulating post-synaptic signals and synaptic plasticity (Pak et al., 2000). Overexpressing NRGN in utero successfully reversed the migration defect caused by Zfp804a knockdown. Taken together, by analyzing the transcriptome, we revealed a novel role of SCZ risk gene ZNF804A in translational regulation. In addition, by profiling the associated genes with ZNF804A, we provided new insights into the mechanism ZNF804A regulates neurodevelopment and contribute the risk of SCZ.