Functional characterization of the schizophrenia associated gene AS3MT identifies a role in neuronal development

Abstract

Genome-wide association studies (GWAS) have identified multiple genomic regions associated with schizophrenia, although many variants reside in noncoding regions characterized by high linkage disequilibrium (LD) making the elucidation of molecular mechanisms challenging. A genomic region on chromosome 10q24 has been consistently associated with schizophrenia with risk attributed to the AS3MT gene.Although AS3MT is hypothesized to play a role in neuronal development and differentiation, work to fully understand the function of this gene has been limited. In this study we explored the function of AS3MT using a neuronal cell line (SH-SY5Y). We confirm previous findings of isoform specific expression of AS3MT during SH-SY5Y differentiation toward neuronal fates. Using CRISPR-Cas9 gene editing we generated AS3MT knockout SH-SY5Y cell lines and used RNA-seq to identify significant changes in gene expression in pathways associated with neuronal development, inflammation, extracellular matrix formation, and RNA processing, including dysregulation of other genes strongly implicated in schizophrenia. We did not observe any morphological changes in cell size and neurite length following neuronal differentiation and MAP2 immunocytochemistry. These results provide novel insights into the potential role of AS3MT in brain development and identify pathways through which genetic variation in this region may confer risk for schizophrenia.

Arsenite methyltransferase 3 regulates hepatic energy metabolism which dictates the hepatic response to arsenic exposure

“…Transcriptomic analysis uncovered a novel and essential role for As3mt in regulating mitochondrial function, specifically the electron transport chain, the TCA and ROS generation, with a prediction that oxidative phosphorylation and ATP generation are disrupted. This analysis also pointed to ribosome biogenesis and function as downregulated in as3mt -/mutants, but the functional significance of that finding is not yet clear, but it is interesting that neurons depleted of AS3MT also show deregulation of the same pathways (22). Overall, this study indicates that the high levels of As3mt detected in hepatocytes is important for maintaining hepatic metabolism in the absence of iAs.…”

“…This same pattern was detected in the shared, positively correlated DEGs (Figure S3B). Interestingly, ribosome function and translation were also enriched in AS3MT deficient neurons (22). This suggests that loss of As3mt during development deregulates ribosome function, protein translation and mitochondrial function.…”

“…Several lines of evidence suggest an alternative: AS3MT is highly conserved, is expressed in a tissue specific fashion in the absence of iAs, and As3mt KO mice have metabolic changes (17,18), with differences in the levels of specific phosphatidylcholine (PC) species (18) and cultured cells with AS3MT knockdown decreases proliferation (19). Moreover, other genome-wide association studies have found that variants of an AS3MT isoform correlates with schizophrenia (20,21) and depletion of AS3MT in neurons resulted in the differential expression of over 1,400 genes (22). However, in the decades since AS3MT was discovered, aside from these few studies, its role in cellular homeostasis has not been investigated.…”

Cell-type and dynamic state govern genetic regulation of gene expression in heterogeneous differentiating cultures

“…5E). While this triangulation of variant, gene, and context has previously been reported 50,51 , such efforts have historically required scanning large-scale databases of regulatory effects in adult or immune contexts, then establishing an in vitro platform to evaluate expression during differentiation into a single cell-type selected a priori . The unification of an expansive set of cellular contexts at various stages of differentiation has the potential to accelerate this process, particularly when it is feasible to explore population-level genetic differences.…”