A new mutation of GCH1 in triplets family with dopa-responsive dystonia

Early-onset autosomal dominant GTP-cyclohydrolase I deficiency: Diagnostic delay and residual motor signs

OBJECTIVE

Autosomal dominant (AD) guanosine triphosphate cyclohydrolase 1 (GCH1) deficiency is the most common cause of dopa-responsive dystonia (DRD). Patients with GCH1 deficiency are likely to experience diagnostic delay, but its consequences have not been described thoroughly in patients with early-onset disease. We describe the diagnostic delay and residual motor signs (RMS) observed in patients with early-onset (before 15 years of age) disease.

METHODS

Twelve patients with early-onset AD GCH1 deficiency from a single center were included in the case series analysis. For the meta-analysis, the PubMed database was searched for articles on early-onset AD GCH1 deficiency published from 1995 to 2019.

RESULTS

In the case series, the mean duration of diagnostic delay was 5.6 years. Two patients exhibited RMS, and four patients underwent orthopedic surgery. The literature search yielded 137 AD GCH1 deficiency cases for review; gait disturbance was reported in 92.7% of patients, diurnal fluctuation of symptoms in 91.9%, and RMS in 39%. The mean duration of diagnostic delay was 14.6 years overall: 12.0 years in RMS-negative patients and 21.2 years in RMS-positive patients.

CONCLUSIONS

Diagnostic delay in early-onset AD GCH1 deficiency is more closely associated with later RMS. Early clinical suspicion, timely diagnosis, and levodopa treatment may reduce the occurrence of RMS in patients with early-onset AD GCH1 deficiency.

Dopa-responsive dystonia: functional analysis of single nucleotide substitutions within the 5' untranslated GCH1 region

Background

Mutations in the GCH1 gene are associated with childhood onset, dopa-responsive dystonia (DRD). Correct diagnosis of DRD is crucial, given the potential for complete recovery once treated with L-dopa. The majority of DRD associated mutations lie within the coding region of the GCH1 gene, but three additional single nucleotide sequence substitutions have been reported within the 5’ untranslated (5’UTR) region of the mRNA. The biologic significance of these 5’UTR GCH1 sequence substitutions has not been analyzed.

Methodology/Principal Findings

Luciferase reporter assays, quantitative real time PCR and RNA decay assays, combined with bioinformatics, revealed a pathogenic 5’UTR GCH1 substitution. The +142C>T single nucleotide 5’UTR substitution that segregates with affected status in DRD patients, substantially attenuates translation without altering RNA expression levels or stability. The +142C>T substitution disrupts translation most likely by creating an upstream initiation start codon (uAUG) and an upstream open reading frame (uORF).

Conclusions/Significance

This is the first GCH1 regulatory substitution reported to act at a post-transcriptional level, increasing the list of genetic diseases caused by abnormal translation and reaffirming the importance of investigating potential regulatory substitutions in genetic diseases.