JNNP Online First, published on February 22, 2018 as 10.1136/jnnp-2017-317581 PostScript J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp-2017-317581 on 22 February 2018. Downloaded from

Letter 606350), TDP1 (MIM: 607198) and Clinical features PNKP (MIM: 605610), respectively.1 Patient 1 was the eldest of three healthy Recently, compound heterozygous siblings from a consanguineous relation- Mutations in XRCC1 cause mutations in XRCC1 were identified ship (first cousins) (figure 1A). He walked cerebellar ataxia and in one individual with ocular motor independently at 15 months. Aged 3 apraxia, cerebellar ataxia and axonal years, he had a persistent ataxic gait and peripheral neuropathy neuropathy.2 However, as this study recurrent falls. He experienced impaired only identified a single case, the causal fine motor skills and upper limb ataxia. Letter role of XRCC1 in Autosomal Recessive In school, he had mild learning disabil- Mutations in involved in single- Cerebellar Ataxia (ARCA) remained in ities, dysarthria and difficulties playing strand break repair (SSBR) have been question and required replication in sports with painful cramps particularly linked to hereditary cerebellar ataxias. additional cases. Here we recapitulate after prolonged exertion. His examina- Notably, Ataxia-oculomotor apraxia 1 and broaden this phenotype in two tion was notable for prominent bilateral (AOA1 (MIM: 2 08 920)), Spinocere- patients of Pakistani decent who were calf wasting and pes planus with impaired bellar ataxia with axonal neuropathy not known to be related. This confirms coordination and dysdiadochokinesis. 1 (SCAN1 (MIM: 6 07 250)) and Atax- the role of XRCC1 in cerebellar ataxia. Aged 15 years, he underwent an MRI ia-oculomotor apraxia 4 (AOA4 (MIM: brain, which was unremarkable. Nerve 616267616267616267)) are associ- conduction studies and electromyo- ated with mutations in APTX (MIM: gram (EMG) showed a length-dependent copyright. http://jnnp.bmj.com/ on September 29, 2021 by guest. Protected

Figure 1 (A) Pedigree of the family of patient 1. Open symbols represent unaffected individuals and filled symbols represent the affected individual.T he proband is indicated by an arrow. Sanger sequencing chromatograms surround the symbols and show segregation of mutations. Blue boxes encompass the sites of interest. (B) Structural conservation of the mutated amino acid residue in XRCC1 across six species. Conservation among species of the amino acid residues was determined using Clustal W2 Software for multiple sequence alignment and plotted with BOXSHADE. (C) Pedigree of the family of patient 2. Open symbols represent unaffected individuals and filled symbols represent the affected individual.T he proband is indicated by an arrow. Sanger sequencing chromatograms surround the symbols and show segregation of mutations. Blue boxes encompass the sites of interest. (D) Patient 1 : MRI examination of the brain demonstrating preservation of the supratentorial and upper cervical spinal cord neuroparenchymal volumes but disproportionate volume loss of the cerebellum and pons on the on the coronal FLAIR (i) and sagittal T1-weighted (ii) sequences. The axial T2-weighted sequences demonstrate associated volume loss of the middle (iii) and superior (iv) cerebellar peduncles (E) MRI examination of the brain and upper spinal cord. The coronal FLAIR (i) and sagittal T1-weighted (ii) sequences demonstrate mild cortical and subcortical supratentorial and upper spinal cord neuroparenchymal volume loss but disproportionate volume loss of the cerebellum. There is also subtle mild asymmetrical volume loss of the head of the right hippocampus. The axial T2-weighted sequences demonstrate associated volume loss of the middle (iii) and superior (iv) cerebellar peduncles. Sagittal T2-weighted (v) and axial Multiple Echo Recombined Gradient Echo (MERGE) (vi) sequences demonstrate diminution of cervical spinal cord volume for age, particularly evident in the axial anterior–posterior dimension. FLAIR, fluid-attenuated inversion recovery.

J Neurol Neurosurg Psychiatry Month 2018 Vol 0 No 0 1 Copyright Article author (or their employer) 2018. Produced by BMJ Publishing Group Ltd under licence. PostScript J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp-2017-317581 on 22 February 2018. Downloaded from moderately severe sensorimotor neurop- programmes. This identified a homozy- progressive cerebellar ataxia accompanied athy of axonal type (online supplementary gous mutation, c.G1293C (p.K431N), in by sensorimotor neuropathy. Expression table 1). exon 11 of XRCC1 (NM_006297) in the analysis together with our findings suggest Currently, aged 22, he continues to affected individuals. This mutation lies that male infertility may also be a feature ambulate independently however is prone within a shared haplotype on chromo- of this condition. However, alternative to frequent falls. Eye examination shows some 19 and was predicted as deleterious causes have not been ruled out. Therefore, slow saccadic initiation, hypometria, by Sorting Intolerant From Tolerant (SIFT) further genotype–phenotype correlation in jerky pursuit and horizontal nystagmus and possibly damaging by polyphen. The a larger cohort is warranted. Finally, this on extreme gaze. He has a broad based missense mutation c.G1293C (p.K431N) variant likely exists at a higher frequency gait, dysmetria and dysdiadochokinesis. forms part of the donor site of intron 11. than previously described, particularly in Reflexes are absent in the lower limbs Whole exome sequencing was used to estab- the South Asian population, and should and planters are extensor on the left and lish intrafamilial segregation and confirmed be considered in patients with cerebellar equivocal on the right. Sensation to light with Sanger sequencing. atrophy and peripheral neuropathy from touch and pain is normal with impaired these regions. vibration sense and proprioception. His recent MRI revealed cerebellar atrophy Comment Emer O'Connor,1 Jana Vandrovcova,1 (figure 1D). XRCC1 is a scaffold that enables Enrico Bugiardini,1 Viorica Chelban,1 Patient 2 was also born to consanguin- SSBR through interactions with a number Andreea Manole,1 Indran Davagnanam,2 1 1 1 eous parents (figure 1C). He had recur- of single-strand repair enzymes. Struc- Sarah Wiethoff, Alan Pittman, David S Lynch, Stephanie Efthymiou,1 Silvia Marino,3 rent falls and excessive clumsiness as an turally, it comprises three globular 4 5 Adnan Y Manzur, Mark Roberts, infant. Throughout his childhood, he domains, an N-terminal and a C-ter- Michael G Hanna,6 Henry Houlden,1 experienced muscle cramps and stiffness minal BRCT domain which interact Emma Matthews,6 Nicholas W Wood1,7 in his lower limbs. He was dysarthric and with DNA polymerase and DNA ligase 1 3 Department of Molecular Neuroscience, Institute of had mild learning difficulties. Diffuse 3α, respectively. The variant c.G1293C Neurology, University College London, London, UK myotonia, predominantly in his hands, (p.K431N) is within the highly conserved 2Department of Brain Repair and Rehabilitation, led to a diagnosis of myotonia congenita central domain (BRCTa) which facilitates Institute of Neurology, University College London, which was confirmed by the identification the binding of XRCC1 to ribosylated London, UK 3 of a homozygous deletion of exons 17–22 poly-ADP-ribose polymerase 1 (PARP1) Department of Neuropathology, Barts and The London School of Medicine and Dentistry, Queen Mary of the CLCN1 (MIM: 118425) . activating partner at sites of University of London, London, UK Now aged 30, he walks without assis- single-strand breaks. A loss of functional 4 Department of Neurology, Great Ormond Street copyright. tance however requires rest after short XRCC1 results in hyperactivation of Hospital for Children, London, UK distances. He has an ataxic waddling PARP.2 This likely impedes the access of 5Department of Neurology, Salford Royal NHS Foundation Trust, Manchester, UK gait with diffuse muscle hypertrophy, DNA repair proteins to the break, leading 6 particularly in the calves and bilateral to defective repair and loss of cerebellar Medical Research Council Center for Neuromuscular Diseases, University College London and National pes cavus. He has moderate hand and . A mouse model with a condi- Hospital for Neurology and Neurosurgery, London, UK eyelid myotonia. Examination of his eye tional XRCC1 deletion illustrated the crit- 7Neurogenetics Laboratory, The National Hospital for movements reveal jerky pursuit with ical physiological role of XRCC1 in the Neurology and Neurosurgery, London, UK 4 nystagmus on lateral gaze. He is areflexic development of cerebellar interneurons. Correspondence to Dr Emer O’Connor, Department throughout with flexor plantar responses The variant, c.G1293C, exists in the of Molecular Neuroscience, UCL Institute of and impaired sensation in the lower limbs heterozygote state in four individuals Neurology, London WC1N 3BG, UK; ​e.​oconnor@​ucl.​ below the knee. In addition to his neuro- of South Asian decent with an allele ac.​uk http://jnnp.bmj.com/ logical symptoms, he is infertile due to frequency of 0.0002449 in ExAC. Our Acknowledgements The authors would like to thank hypogonadism and azoospermia. EMG patients presented with a slowly progres- the participants and their families for their essential and MRI revealed a sensorimotor axonal sive cerebellar ataxia and sensorimotor help with this work. neuropathy (online supplementary table axonal neuropathy, in concordance with Contributors EO: design, data analysis and 1) and cerebellar atrophy (figure 1E). the previously described case.2 Notably, interpretation, writing of manuscript and overall our patients had a younger age of onset guarantor. JV, AM, AP, ID, SM, SE: analysis and with observable signs at 3 years. Also, interpretation of data. DSL, SW, AM, MR: acquisition

and interpretation of clinical data. MGH, HH, EM, on September 29, 2021 by guest. Protected Whole exome sequencing their examination elicited comparably NWW: critical revision of the manuscript for important The patients and their unaffected parents subtle ocular signs with slightly prolonged intellectual content. were recruited with informed consent. latency in saccadic initiation in only one Funding The Brain Research Trust, The Medical DNA was extracted from peripheral blood case. Research Council (MRC UK), The Wellcome Trust and whole exome sequencing was carried XRCC1 is highly expressed in brain (equipment and the Synaptopathies strategic award out on the affected individuals and their particularly in the cerebellum on the GTEX (104033)) and the EU FP7/2007D2013 under grant parents. Homozygosity mapping was portal, however it is most highly expressed agreement number 2012D305121 (NEUROMICS), The performed identifying three regions of in the pituitary and gonads. This is inter- MDA USA, Muscular Dystrophy UK, Rosetrees Trust, Ataxia UK and the British Neurological Surveillance homozygosity shared between the affected esting considering the finding of infertility Unit (BNSU). The National Institute for Health also individuals including 1 (236 in patient 2, as in vitro studies of mouse supported. 645 670–237024414), chromosome 8 (90 and human sertoli cells demonstrate the Competing interests None declared. 995 019–95 182 986) and involvement of XRCC1 and PARP1 (MIM: (42 595 163–45 989 473). Variants within 173870) in DNA repair which is essential to Patient consent Obtained. these regions were filtered for rare, homo- the survival of these quiescent cells.5 Ethics approval Ethics Committee of UCLH, London. zygous, mutations that were described as In conclusion, homozygous mutations in Provenance and peer review Not commissioned; deleterious by in silico protein prediction XRCC1 result in a core phenotype of slowly externally peer reviewed.

2 J Neurol Neurosurg Psychiatry Month 2018 Vol 0 No 0 PostScript J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp-2017-317581 on 22 February 2018. Downloaded from

►► Additional material is published online only. To References view please visit the journal online (http://​dx.​doi.​org/​ 1 Caldecott KW. Single-strand break repair and genetic 10.1136/​ ​jnnp-2017-​ ​317581). disease. Nat Rev Genet 2008;9:619–31. 2 Hoch NC, Hanzlikova H, Rulten SL, et al. XRCC1 mutation is associated with PARP1 hyperactivation and cerebellar ataxia. Nature 2017;541. Open Access This is an Open Access article distributed 3 Cuneo MJ, London RE. Oxidation state of the XRCC1 in accordance with the terms of the Creative Commons To cite O’Connor E, Vandrovcova J, Bugiardini E, et al. N-terminal domain regulates DNA polymerase Attribution (CC BY 4.0) license, which permits others to J Neurol Neurosurg Psychiatry Epub ahead of print: beta binding affinity. Proc Natl Acad Sci U S A distribute, remix, adapt and build upon this work, for [please include Day Month Year]. doi:10.1136/jnnp- 2010;107:6805–10. commercial use, provided the original work is properly 2017-317581 4 Lee Y, Katyal S, Li Y, et al. The genesis of cerebellar cited. See: http://creativecommons​ .​org/licenses/​ ​by/4.​ ​0/ interneurons and the prevention of neural Received 3 November 2017 © Article author(s) (or their employer(s) unless DNA damage require XRCC1. Nat Neurosci Revised 19 January 2018 2009;12:973–80. otherwise stated in the text of the article) 2018. All Accepted 24 January 2018 rights reserved. No commercial use is permitted unless 5 Ahmed EA, Rijbroek ADB-van, Kal HB, et al. otherwise expressly granted. J Neurol Neurosurg Psychiatry 2018;0:1–3. Proliferative activity in vitro and DNA repair indicate doi:10.1136/jnnp-2017-317581 that adult mouse and human sertoli cells are not terminally differentiated, quiescent cells1. Biol Reprod 2009;80:1084–91. copyright. http://jnnp.bmj.com/ on September 29, 2021 by guest. Protected

J Neurol Neurosurg Psychiatry Month 2018 Vol 0 No 0 3