J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp-2013-306483 on 11 November 2013. Downloaded from Neurogenetics RESEARCH PAPER Autosomal-recessive cerebellar ataxia caused by a novel ADCK3 mutation that elongates the protein: clinical, genetic and biochemical characterisation Yo-Tsen Liu,1,2,3,4 Joshua Hersheson,2 Vincent Plagnol,5 Katherine Fawcett,2 Kate E C Duberley,2 Elisavet Preza,2 Iain P Hargreaves,6 Annapurna Chalasani,6 Open Access 1,2 2 1,2 1,2 Scan to access more Matilde Laurá, Nick W Wood, Mary M Reilly, Henry Houlden free content ▸ Additional material is ABSTRACT potentially treatable causes of ARCA as the symp- published online only. To view Background The autosomal-recessive cerebellar ataxias toms in many patients improve with CoQ10 sup- please visit the journal online 45 (http://dx.doi.org/10.1136/ (ARCA) are a clinically and genetically heterogeneous plementation. CoQ10 is a lipid-soluble jnnp-2013-306483). group of neurodegenerative disorders. The large number component located in the inner mitochondrial of ARCA genes leads to delay and difficulties obtaining membrane. It plays a pivotal role in the oxidative 1MRC Centre for Neuromuscular Diseases, an exact diagnosis in many patients and families. phosphorylation system (OXPHOS) by shuttling UCL Institute of Neurology Ubiquinone (CoQ10) deficiency is one of the potentially electrons derived from mitochondrial respiratory and National Hospital for treatable causes of ARCAs as some patients respond to chain (MRC) complexes I (NADH ubiquinone Neurology and Neurosurgery, CoQ10 supplementation. The AarF domain containing oxidoreductase) and II (succinate ubiquinone oxi- London, UK 2Department of Molecular kinase 3 gene (ADCK3) is one of several genes doreductase) to complex III (ubiquinol cytochrome Neuroscience, UCL Institute of associated with CoQ10 deficiency. ADCK3 encodes a c oxidoreductase), and also participates in other Neurology and National mitochondrial protein which functions as an electron- cellular processes as a potent antioxidant, and by Hospital for Neurology and transfer membrane protein complex in the mitochondrial influencing pyrimidine metabolism.67 Neurosurgery, London, UK respiratory chain (MRC). The AarF domain containing kinase 3 gene 3Section of Epilepsy, Methods We report two siblings from a consanguineous (ADCK3, MIM_606980) is one of the genes Department of Neurology, copyright. Neurological Institute, Taipei Pakistani family who presented with cerebellar ataxia and involved in the biosynthetic pathway of CoQ10, Veterans General Hospital, severe myoclonus from adolescence. Whole exome thus, their mutations can cause CoQ10 deficiency Taipei, Taiwan fi 4 sequencing and biochemical assessment of broblasts where most mutations are at loss of function. National Yang-Ming University ADCK3 School of Medicine, Taipei, were performed in the index patient. is the homologue of the yeast Coq8 gene Taiwan Results A novel homozygous frameshift mutation in and encodes a mitochondrial protein which func- 5University College London, ADCK3 (p.Ser616Leufs*114), was identified in both tions in an electron-transferring membrane protein Genetics Institute, London, UK 8 ADCK3 6 siblings. This frameshift mutation results in the loss of complex in the MRC. Patients with muta- Neurometabolic Unit, National the stop codon, extending the coding protein by 81 tions usually have disease onset in infancy or early Hospital of Neurology and fi fi Neurosurgery, London, UK amino acids. Signi cant CoQ10 de ciency and reduced childhood and can present with pure cerebellar MRC enzyme activities in the index patient's fibroblasts ataxia or a complex phenotype with additional fea- Correspondence to suggested that the mutant protein may reduce the tures, such as seizures, cognitive impairment, Professor Henry Houlden, efficiency of mitochondrial electron transfer. CoQ10 depression, peripheral neuropathy, strabismus or http://jnnp.bmj.com/ Department of Molecular 8–11 Neuroscience and MRC Centre supplementation was initiated following these genetic exercise intolerance. for Neuromuscular Diseases, and biochemical analyses. She gained substantial In this study, we report two affected siblings in UCL Institute of Neurology and improvement in myoclonic movements, ataxic gait and their 20 s, from a consanguineous family of National Hospital for dysarthric speech after treatment. Pakistani origin, who both presented with cerebel- Neurology and Neurosurgery, Conclusion This study highlights the importance of lar ataxia, myoclonus and dysarthria. Whole exome Queen Square House, Queen fi Square, London WC1N 3BG, diagnosing ADCK3 mutations and the potential bene t sequencing (WES) performed in the index patient UK; [email protected] of treatment for patients. The identification of this new identified a homozygous frameshift mutation in on September 26, 2021 by guest. Protected mutation broadens the phenotypic spectrum associated ADCK3. This mutation results in the loss of the Received 8 August 2013 with ADCK3 mutations and provides further stop codon and extension of the protein by 81 Revised 7 October 2013 Accepted 14 October 2013 understanding of their pathogenic mechanism. amino acids. CoQ10 level and the MRC enzyme Published Online First activities in the index patient’s fibroblasts were also 11 November 2013 investigated and CoQ10 supplementation was given to her based on the genetic and functional results. INTRODUCTION Significant improvements in all symptoms men- Autosomal-recessive cerebellar ataxias (ARCA) are tioned above were observed after treatment. a group of inherited neurodegenerative disorders characterised primarily by cerebellar ataxia, but are frequently associated with other neurological mani- PATIENTS AND METHODS festations including spasticity, peripheral neur- Patients To cite: Liu Y-T, Hersheson J, Plagnol V, opathy, seizures and optic atrophy. ARCAs are With informed consent, we clinically evaluated and et al. J Neurol Neurosurg genetically heterogeneous with more than 20 causa- obtained blood samples from the index patient and – Psychiatry 2014;85: tive genes currently recognised.1 3 Coenzyme Q10 the affected sibling. A skin biopsy was also obtained – 493 498. (CoQ10) deficiency (MIM_607426) is one of the from the index patient. This study was approved by Liu Y-T, et al. J Neurol Neurosurg Psychiatry 2014;85:493–498. doi:10.1136/jnnp-2013-306483 493 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp-2013-306483 on 11 November 2013. Downloaded from Neurogenetics the joint ethics committee of UCL Institute of Neurology and The C4 (150 mm×3 mm, 3 mm) with a Gold C4 guard column (3, National Hospital for Neurology and Neurosurgery, London, UK. 10 mm length, 3 mm) operated at 40°C at a flow rate of 0.4 mL/ min. The mobile phases consisted of methanol, 4 mM ammo- WES and variant calling nium acetate 0.1% formic acid and methanol:isopropanol:formic In an attempt to rapidly identify the underlying genetic muta- acid (45:55:0.5, v/v/v) containing 5 mM methylamine as an ion tion, WES was carried out on the index patient at the NIH pair reagent. Isocratic delivery of the mobile phase ensured (Bethesda, USA). Nimblegen SeqCap EZ Exome kit (in solution elution of the CoQ10 methylammonium adduct at approximately capture) was used for the exome capture. Shotgun sequencing 8 min. D6-CoQ10 was used as an internal standard. libraries were generated from 3 mg genomic DNA which was extracted from peripheral blood using Flexigene extraction kit MRC enzyme activities and Autopure LS (Qiagen) extraction system. Sequencing was Activities of MRC complex I, complex II–III, complex IV (cyto- performed on a Genome Analyzer IIx, according to the manu- chrome c oxidase) and citrate synthase (CS) were determined in facturer’’s instruction. FASTQ files were aligned to the hg19 ref- the fibroblast cells according to methods previously described.13 erence sequence using Novoalign V.2.07.19, including hard and Results were expressed as a ratio to CS activity and were nor- soft clipping, quality calibration and adapter trimming. malised against protein. Protein quantification was determined Duplicate reads were excluded using the PICARD tool using the Lowry method using bovine serum albumin as a MarkDuplicates. Calling was performed using SAMtools V.0.18 standard.14 and single sample calling. The resulting calls were annotated with ANNOVAR. Candidate variants were filtered based on RESULTS function: frameshift, premature stop, non-synonymous or Clinical features potential splice-altering variants (defined as being within 5 bp of This 35-year-old lady started to experience myoclonus and jerky the actual splice site) and frequency (<0.5% in the 1000 tremor in the head and limbs at 10 years old. Slurred speech Genomes and the National Heart, Lung, and Blood Institute and unsteady gait developed subsequently in her second decade. (NHLBI) Exome Sequencing Project database (http://evs.gs. There was no response to levodopa. By 30 years of age, she had washington.edu/EVS/) for homozygous and compound hetero- become wheelchair-dependent because of the ataxic myoclonic zygous variants, and absent from both of these databases for gait. She also had difficulty in writing and holding objects due heterozygous variants). VCF tools were used to annotate gene to ataxia and involuntary movements. Her speech fatigued information for the remaining novel variants. The Integrative easily, was often tremulous and dysarthric and she also com- Genomics Viewer (IGV) was used to inspect variants. plained of