Novel P-TEN-induced putative kinase 1 (PINK1) variant in Indian Parkinson's disease patient

Abstract

Loss-of-function mutation in PINK1 is known for causing autosomal recessive early onset Parkinsonism accounting approximately 6.5% of PD cases. Recently, PINK1 has also been shown to cause Parkinson's disease (PD) in eastern India. Present study is aimed to see its contribution in north-Indian PD patients. A total of 106 PD patients and 60 ethnically matched healthy controls were included in the study. All the patients were screened for mutation in PINK1 by direct DNA sequence analysis of the PCR amplicons covering all exons and exon-intron boundaries. Identified novel variant was reconfirmed by DNA sequencing of 10 randomly selected TA clones containing the variant amplicon. In vitro functional assay of the mutant protein was performed by transfecting COS-7 cell line with wild type and mutant (created by site-directed-mutagenesis) cDNA construct of PINK1 fused to N' terminal GFP followed by western blot analysis. Two potentially pathogenic, one being novel (p.Q267X) and 6 other apparently non-pathogenic variants were identified. Western blot analysis reveals production of truncated PINK1 fusion protein of ∼55kDa in p.Q267X mutant instead of 82/93kDa of wild type PINK1 fusion protein (molecular weight of GFP is ∼27kDa). Our study concludes that PINK1 variants are prevalent for causing Parkinson's disease (PD) in India, as revealed by the occurrence of 1.8% (2/106) in PD patients from north Indian population. The novel homozygous variant of PINK1 (c.799C>T) reported here is the plausible cause for disease manifestation in this patient. Future study, however, would be helpful to understand the functional mechanism how this premature PINK1 protein (p.Q267X) responds to cellular stress leading to the PD pathophysiology.

Keywords: ClinVar: rs30882053; Haploinsufficiency; Mutation; Parkinson’s disease; Site-directed-mutagenesis; Truncated PINK1.