Pathogenesis of PARK-7 knocked out Parkinson’s disease in vitro using isogenic induced pluripotent stem cells

Abstract

DJ-1 is a multifunctional protein, that is found to be involved in the pathogenesis of several types of cancers, neurodegenerative diseases, and other diverse disorders, which reflects its association with dozens of generally vital pathways for cell survival, growth, and proliferation regulation. Particularly, in the context of Parkinson’s disease (PD), mutations in PARK-7 gene, that encodes DJ-1, were found to be associated with autosomal recessive (AR) early onset phenotype of PD (EOPD) in different kindreds.

A compounding body of evidence suggests the precedence of mitochondrial damage to dopaminergic midbrain neuronal loss; the main pathological hallmark of PD. As an oxidative stress buffer, and autophagy lysosomal pathway (ALP) regulator, DJ-1 is proposed to protect against excessive reactive oxygen species (ROS) mediated mitochondrial damage, and mitochondrial autophagy (mitophagy) regulation, respectively.

In a bid to reach an exact definition of DJ-1 role in protection against PD, there have been several models of PARK-7 K.O induced PD, for instance transgenic rats, mice, zebrafish, C.elegans, and Drosophila Melanogaster. Although they could give some clues about DJ-1 functionality, they could not imitate the overall view, since they lack the complexity of human brain. To that end, the development in induced pluripotent stem cells (iPSCs) reprogramming technology provided a relatively powerful tool to allow for closer mimicry.

In this work, zinc finger nuclease (ZFN) technology was used to induce a bi-allelic K.O in PARK-7 in one of the two isogenic iPSCs cell lines which were further differentiated to their dopaminergic midbrain neurons counterparts in order to have a clearer view to DJ-1 functionality in tackling PD. We showed the vulnerability of Dopaminergic neurons (DN) to mitochondrial damage mediated necrotic cell death in PARK-7 K.O cell line, and disturbed mitochondrial clearance that results in accumulation of the dysfunctional mitochondria contributing to the pathology of PD.