ORIGINAL ARTICLE WWOX-related encephalopathies: delineation of the phenotypical spectrum and emerging genotype-phenotype correlation Cyril Mignot, 1 Laetitia Lambert, 2 Laurent Pasquier, 3 Thierry Bienvenu, 4 Andrée Delahaye-Duriez, 5 Boris Keren, 1 Jérémie Lefranc, 6 Aline Saunier, 7 Lila Allou, 8 Virginie Roth, 7 Mylène Valduga, 7 Aissa Moustaïne, 7 Stéphane Auvin, 9 Catherine Barrey, 10 Sandra Chantot-Bastaraud, 11 Nicolas Lebrun, 4 Marie-Laure Moutard, 12 Marie-Christine Nougues, 12 Anne-Isabelle Vermersch, 13 Bénédicte Héron, 12,14 Eva Pipiras, 5 Delphine Héron, 1 Laurence Olivier-Faivre, 15 Jean-Louis Guéant, 8 Philippe Jonveaux, 7,8 Christophe Philippe 7,8 ▸ Additional material is published online only. To view please visit the journal online (http://dx.doi.org/10.1136/ jmedgenet-2014-102748). For numbered affiliations see end of article. Correspondence to Dr Christophe Philippe, Laboratoire de génétique médicale, Centre Hospitalier Régional et Universitaire, Rue du Morvan, Vandoeuvre-les- Nancy 54511 cedex 1, France; c.philippe@chu-nancy.fr Received 28 August 2014 Revised 17 October 2014 Accepted 30 October 2014 To cite: Mignot C, Lambert L, Pasquier L, et al. J Med Genet Published Online First: [ please include Day Month Year] doi:10.1136/jmedgenet- 2014-102748 ABSTRACT Background Homozygous mutations in WWOX were reported in eight individuals of two families with autosomal recessive spinocerebellar ataxia type 12 and in two siblings with infantile epileptic encephalopathy (IEE), including one who deceased prior to DNA sampling. Methods By combining array comparative genomic hybridisation, targeted Sanger sequencing and next generation sequencing, we identified five further patients from four families with IEE due to biallelic alterations of WWOX. Results We identified eight deleterious WWOX alleles consisting in four deletions, a four base-pair frameshifting deletion, one missense and two nonsense mutations. Genotype-phenotype correlation emerges from the seven reported families. The phenotype in four patients carrying two predicted null alleles was characterised by (1) little if any psychomotor acquisitions, poor spontaneous motility and absent eye contact from birth, (2) pharmacoresistant epilepsy starting in the 1st weeks of life, (3) possible retinal degeneration, acquired microcephaly and premature death. This contrasted with the less severe autosomal recessive spinocerebellar ataxia type 12 phenotype due to hypomorphic alleles. In line with this correlation, the phenotype in two siblings carrying a null allele and a missense mutation was intermediate. Conclusions Our results obtained by a combination of different molecular techniques undoubtedly incriminate WWOX as a gene for recessive IEE and illustrate the usefulness of high throughput data mining for the identification of genes for rare autosomal recessive disorders. The structure of the WWOX locus encompassing the FRA16D fragile site might explain why constitutive deletions are recurrently reported in genetic databases, suggesting that WWOX-related encephalopathies, although likely rare, may not be exceptional. INTRODUCTION The human WW domain-containing oxidoreduc- tase (WWOX) gene was cloned in 2000. 1 It is located on chromosome 16q23.1-q23.2 and crosses the second most common fragile site in the human genome (FRA16D). 2 Several functions were ascribed to WWOX, including a proapoptotic activity and a tumour sup- pressor function. 3–5 Various animal models (see online supplementary table S1) confirmed the role of WWOX in fundamental cellular processes, including survival, growth, bone and steroid metab- olism, and in neoplastic transformation. 6–10 In humans, WWOX is one of the most frequently altered genes in cancer cell lines 11 and in tumours 12 in which it may harbour heterozygous or homozygous deletions, translocations or hyper- methylation of the promotor. Deciphering the role of WWOX in brain development started with the finding that a null WWOX genotype induces sei- zures in rats, 13 which proved to be also the case in mice and humans. 14 Epileptic encephalopathies are a heterogeneous group of disorders characterised by epilepsy with lasting deleterious impact in the developing brain. 15 When the underlying cause is unknown, the extent of this impact is often difficult to dem- onstrate. Thus, conditions with epileptic syndromes associated with deleterious effects on development, such as West syndrome, and conditions with phar- macoresistant epilepsy in the foreground are often considered as epileptic encephalopathies. Recent studies 16 17 and reviews 18 19 underlined the great genetic heterogeneity of infantile epileptic enceph- alopathies (IEEs). Few genes are known to underlie recessive forms of IEE. WWOX has been pointed as one of them in one family study to date. 20 We provide data substantially confirming this finding in five patients from four families. PATIENTS AND METHODS Patients We initially tested by chromosomal microarray ana- lysis (CMA) a panel of 18 girls with typical or con- genital Rett syndrome and negative for mutations in MECP2, CDKL5, FOXG1 and MEF2C. This project was supported by a grant from the Mignot C, et al. J Med Genet 2014;0:1–10. doi:10.1136/jmedgenet-2014-102748 1 Developmental defects JMG Online First, published on November 19, 2014 as 10.1136/jmedgenet-2014-102748 Copyright Article author (or their employer) 2014. Produced by BMJ Publishing Group Ltd under licence. group.bmj.com on November 25, 2014 - Published by http://jmg.bmj.com/ Downloaded from