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PArkin Co-Regulated Gene (PACRG) is a novel gene which is transcriptionally co-regulated with the parkin gene (PRKN) by a shared bi-directional promoter. To determine whether mutations in PACRG are associated with early-onset Parkinson's disease (EO-PD), we performed sequence and dosage analysis of 76 EO-PD patients from a Taiwanese-Ethnic Chinese cohort. This analysis identified two novel nucleotide variants in the non-coding region of PACRG. One patient had an IVS2+247851T>C heterozygous change and two patients had an IVS4+78A>G heterozygous alteration. Neither of these variants was present in the 91 controls tested. A third intronic polymorphism (IVS1+85744insC) was present in cases and controls at an equivalent frequency (approximately 0.25). To facilitate gene dosage analysis, we identified cell lines with a heterozygous deletion or duplication of the entire PACRG locus. Three patients with heterozygous dosage alterations were identified, including two patients with an exon 2 duplication and one patient with an exon 3 deletion of PACRG. No dosage alterations were observed in the 91 controls analyzed (chi(2)=3.66, P=0.056). Our results suggest that point mutations in PACRG are not a common cause of EO-PD but haploinsufficiency for PACRG may be associated with disease.

Mutations in parkin are a common cause of early-onset autosomal recessive Parkinson's disease (PD). A single nucleotide polymorphism in the parkin promoter (rs9347683, -258T/G) has been reported to be associated with PD and shown to functionally affect gene transcription in luciferase reporter assays. In addition, homozygosity for the minor allele of rs9347683 may significantly reduce the age of onset of PD. We investigated the polymorphism in a cohort of cases with early-onset PD previously excluded for mutations in PD associated loci. We did not observe any differences in allele or genotype frequencies between the cases and the controls and there was no evidence for an effect on age of disease onset. Our results do not support a role for this variant in early-onset PD.

We screened for mutations in the PARKIN, DJ-1, and PINK1 genes in a Taiwanese cohort (68 probands; 58 sporadic and 10 familial) with early-onset parkinsonism (EOP, onset <50 years of age). We identified 9 patients harboring mutations in PARKIN (three compound heterozygous and six single heterozygous carriers), 3 patients with heterozygous PINK1 mutations (including two novel substitutions M341I and P209A), and no DJ-1 mutations. Our frequencies of PARKIN (two allele mutation, 4.4%; single allele, 8.8%) and PINK1 (single heterozygous, 4.4%) mutations in Taiwanese-Chinese are similar to those in Caucasian and other Asian EOP patients. Although the role of heterozygosity of recessive genes in EOP remains to be resolved, molecular analysis and functional imaging will play a decisive role in differential diagnosis and determined therapeutic strategy.