Objective: In this study we investigate the cellular mechanism underlying the Parkinson’s disease (PD)-associated mutation c.192G>C in PARK7 and present a compound treatment that rescues the cellular phenotype in a patient-based cell model.

Background: Homozygous loss-of-function mutations in the DJ-1 gene PARK7 cause a rare form of inherited early-onset Parkinson’s disease (PD). DJ-1 covers a wide range of biological functions. It acts as sensor of oxidative stress, as chaperone, glyoxylase and as transcriptional regulator. Patient-derived cellular models harboring the homozygous c.192G>C mutation display specific cellular phenotypes due to loss of function of DJ-1. This mutation was predicted to cause an E64D amino acid change, however, using patient-based material we show a different mechanism leading to loss of DJ-1.

Methods: Patient’s fibroblasts were obtained from skin biopsy and reprogrammed into induced pluripotent stem cells (iPSCs). Fibroblasts and iPSC-derived neurons, were used to study the effect of the mutation and to identify compounds that rescue cellular phenotypes.

Results: We identified the c.192G>C mutation to cause mis-splicing of DJ-1 pre-mRNA instead of an amino acid change. We identified impaired U1 mediated recognition of the splice-donor site at exon 3 of PARK7 leading to skipping of exon 3 (ΔEx3). Although the levels of ΔEx3 mRNA in patient cells are comparable to wild-type DJ-1 mRNA in control cells, DJ-1 protein levels in patient cells are dramatically reduced.

Genetic intervention restored DJ-1 protein levels only when cells were transduced with full-length DJ-1 vectors. Translation of full-length mutant DJ-1 could be rescued when patient cells were transduced with genetically engineered U1 snRNA in patient cells.

Moreover, we identified a combination of two compounds that rescues mis-splicing of DJ-1 mRNA and cellular function in patient-derived cell models.

Conclusions: In contrast to current notion we have discovered that the c.192G>C mutation in PARK7 does not cause an E>D missense mutation but a loss of protein due to exon skipping and provide strategies for genetic and pharmacological rescue.

Treatment with a combination of two compounds rescues correct splicing of mutant DJ-1 mRNA as well as cellular function in patient cells.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/genetic-and-pharmacological-rescue-of-dj-1-loss-of-function-caused-by-a-c-192gc-mutation-in-park7/