Validation of a PCR-based Test for the Genetic Diagnosis of Filipino Patients with X-Linked Dystonia Parkinsonism (Xdp)

Paul Matthew D. Pasco, Toshitaka Kawarai, Catherine Lynn T. Silao,
Daffodil M. Canson, Lillian V. Lee and Ryuji Kaji

Background and Objective: X-linked dystonia parkinsonism (XDP, DYT3, MIM #314250) is a neurodegenerative movement disorder found endemically in the Philippines. An SVA retrotransposon insertion mutation has been described in patients with XDP, which requires Southern analysis for detection. However, this method is costly and time-consuming. Hence we developed a PCR-based method and validated it among our local population.

Methods and Results: A total of 58 samples from 58 patients with a clinical diagnosis of XDP were collected. Other samples were from an obligate female carrier, two unaffected male relatives, and two patients with typical Parkinson’s disease. Primers designed to amplify the SVA retrotransposon found in the DYT3-TAF1 gene (NCBI Accession Number AB191243) were used. All patients were positive for the expected 3229-bp product after PCR amplification. The normal control showed a 599-bp product, while the female carrier showed both the 3229 and 599-bp product. Subsequent RFLP analysis using BamHI verified the presence of the SVA retrotransposon insertion mutation.

Conclusion: Our results show that large-scale PCR-based testing to screen for genetic diseases with a relatively high prevalence such as XDP is possible in our setting. When followed by RFLP analysis, this can provide genetic confirmation of the diagnosis of XDP and facilitate proper genetic counselling and therapy.

Key Words: X-linked dystonia-parkinsonism, PCR, SVA retrotransposon