DJ-1 deficiency in SH-SY5Y cells reveals dysregulated networks of genes and pathways involved in neuronal function and disease

Parkinsons disease (PD) is the second most common neurodegenerative disease, affecting between 2 - 3% of the population aged 65 and older. Although the etiology of idiopathic PD is still to be elucidated, the study of heritable forms of the disease can provide new understanding into disease mechanisms. Recessively inherited loss of function mutations in the PARK7/DJ-1 gene has been found to be causative for familial, early-onset PD. Importantly, PARK7/DJ-1 related forms of familial PD replicate common disease phenotypes seen in idiopathic PD, including degeneration of substantia nigra dopaminergic neurons, and Parkinsonism. In this study, we evaluate the loss of function of PARK7/DJ-1 on a human neuronal cell line, SH-SY5Y. Following ablation of the PARK7/DJ-1 gene via CRISPR-Cas9, RNA sequencing and the DESEQ2 tool kit were utilized to filter differentially expressed genes between PARK7/DJ-1 knockouts and control SH- SY5Y cells. 5684 genes were identified to be significantly differentially expressed. 3 genes from each of the top 10 upregulated (ATOH8, LAYN, TLX2) and downregulated (CACNA1B, CPLX2, SV2C) gene lists were selected and confirmed via RT-PCR. Differentially expressed gene lists were run through the WebGestalt functional enrichment analysis toolkit to identify enriched gene ontology (GO) terms for biological processes, cellular components, molecular function, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways respectively. Among the top 10 significantly enriched KEGG pathways for upregulated genes were those related to neurodegenerative diseases such as Parkinsons disease, Alzheimers disease, and Huntingtons disease (p-adj [≤] 0.05). Differentially expressed genes were run through the STRING database to predict protein-protein interactions (PPI). A highly significant PPI enrichment was observed (p < 1.0e-16). Our results indicate that loss of DJ-1 function in human neuronal cells leads to dysregulation of networks of connected genes and pathways that are implicated in neurodegenerative disease as well as neuronal function.