European Journal of Human Genetics (2014) 22, 369–373 & 2014 Macmillan Publishers Limited All rights reserved 1018-4813/14 www.nature.com/ejhg ARTICLE An unusual clinical severity of 16p11.2 deletion syndrome caused by unmasked recessive mutation of CLN3 Ce´line Pebrel-Richard*,1,2, Anne Debost-Legrand3, Ele´onore Eymard-Pierre1,2, Victoria Greze3, Ste´phan Kemeny1,2, Mathilde Gay-Bellile1,2, Laetitia Gouas1,2, Andreı¨Tchirkov1,2, Philippe Vago1,2, Carole Goumy1,2 and Christine Francannet3 With the introduction of array comparative genomic hybridization (aCGH) techniques in the diagnostic setting of patients with developmental delay and congenital malformations, many new microdeletion syndromes have been recognized. One of these recently recognized microdeletion syndromes is the 16p11.2 deletion syndrome, associated with variable clinical outcomes including developmental delay, autism spectrum disorder, epilepsy, and obesity, but also apparently normal phenotype. We report on a 16-year-old patient with developmental delay, exhibiting retinis pigmentosa with progressive visual failure from the age of 9 years, ataxia, and peripheral neuropathy. Chromosomal microarray analysis identified a 1.7-Mb 16p11.2 deletion encompassing the 593-kb common deletion (B29.5 to B30.1 Mb; Hg18) and the 220-kb distal deletion (B28.74 to B28.95 Mb; Hg18) that partially included the CLN3 gene. As the patient’s clinical findings were different from usual 16p11.2 microdeletion phenotypes and showed some features reminiscent of juvenile neuronal ceroid-lipofuscinosis (JNCL, Batten disease, OMIM 204200), we suspected and confirmed a mutation of the remaining CLN3 allele. This case further illustrates that unmasking of hemizygous recessive mutations by chromosomal deletion represents one explanation for the phenotypic variability observed in chromosomal deletion disorders. European Journal of Human Genetics (2014) 22, 369–373; doi:10.1038/ejhg.2013.141; published online 17 July 2013 Keywords: 16p11.2 deletion syndrome; juvenile neuronal ceroid-lipofuscinosis; hemizygous CLN3 mutation INTRODUCTION in the CLN3 gene located on chromosome 16p11.2 and characterized by progressive visual failure from the early school years and Common 16p11.2 microdeletion is defined as the presence of a deterioration in the early teenage years together with the onset of 593-kb deletion at map position B29.5 to B30.1 Mb (Hg18), seizures, behavioral difficulties, until dementia. To the best of our between two segmental duplications, suggesting NAHR as the knowledge, this is the first 16p11.2-deletion patient in whom causative mechanism.1 Adjacent and more distal to this 16p11.2 unmasking of autosomal recessive gene mutation by a hemizygous deletion, there is a less frequently reported 220-kb 16p11.2 deletion deletion is demonstrated. (B28.74 to B28.95 Mb;Hg18) that was referred to as the ‘atypical 16p11.2 deletion’2 or ‘distal 16p11.2 deletion’.3 Larger 16p11.2 deletions were also reported, including the distal deletion but not MATERIALS AND METHODS the common 16p11.2 deletion.4–6 Finally, few cases encompassing Case history both the distal and the common deletions were described in the The patient was the second child of non-consanguineous and healthy parents, literature.4,7–9 with no relevant family history. The pregnancy and delivery were uneventful. Recurrent 16p11.2 deletions are associated with variable clinical His birthweight was 2830 g ( À2 SD), length was 49 cm ( À0.5 SD) and features, including delayed language development, learning difficulties/ occipital-frontal circumference was 34 cm ( À0.5 SD). He was hypotonic, was intellectual disability, social impairments with or without autism able to hold his head at 4 months, sat alone at 13 months, and was able to walk spectrum disorder and minor dysmorphic facial features without a after 2 years. Speech development was also delayed. At the age of 9 years, acute visual impairment appeared with retinis pigmentosa and progressive visual consistent pattern. They can also be associated with a normal loss. He presented recent ataxia and peripheral neuropathy. phenotype. On examination at the age of 16 years, his weight was 64.4 kg ( þ 1SD),his Here, we present a patient who harbors an uncommon 16p11.2 size was 1.68 m (median), and his head circumference was 55 cm (median). microdeletion with some features reminiscent of juvenile neuronal The patient had gynecoid obesity with purple stretch marks on the pelvic ceroid-lipofuscinosis (JNCL) or Batten disease (OMIM 204200), a bones. No dysmorphic features was described. He reported sleeping troubles progressive neurodegenerative disorder, caused by recessive mutations with very early wake-up. There was a bulimic symptomatology and he had 1Cytoge´ ne´ tique Me´dicale, Univ Clermont1, UFR Me´decine, CHU Estaing, Clermont-Ferrand, France; 2ERTICa, EA 4677, Univ Clermont1, UFR Me´ decine, Clermont-Ferrand, France; 3Ge´ne´tique Me´dicale, CHU Estaing, Clermont-Ferrand, France *Correspondence: Dr C Pebrel-Richard, Cytoge´ne´tique Me´dicale, Univ Clermont1, UFR Me´decine, CHU Estaing, 1 Place Lucie et Raymond Aubrac, Cedex1, Clermont-Ferrand 63003, France. Tel: +33 4 73 750 709; Fax: +33 4 73 750 704; E-mail: [email protected] Received 23 February 2013; revised 29 May 2013; accepted 3 June 2013; published online 17 July 2013 370 European Journal of Human Genetics Table 1 Clinical features of our patient compared with previously reported cases of 16p11.2 deletions and patients with classic JNCL Common proximal Atypical 16p11.2 Classic JNCL (1.02 kb 16p11.2 deletion deletion deletion on CLN3 gene) Large 16p11.2 deletion Ghebranious et al., Bachmann-Gagescu Ballif et al., Bochukova et al., Bochukova et al., Hanson et al., Sampson Sampson et al., 20071 Bijlsma et al., 20106 Baarge- Our Clinical spectrum 20074 20107 20107 20108 et al., 20109 20109 et al.20092 Schaapveld et al., 2011 Haltia, 200315 patient Progression of vision loss until blindness na na na Patient too young to na na ÀÀ þþ evaluate manifestations (Onset B2–5 years) (Onset 9 Recessive mutation of reliably years) Deterioration in cognitive skills, speech and mobility na na na na na ÀÀ þþ Seizures na na na þ na þ þþÀ (Onset 1 year) (Onset 9–18 years) Premature death na na na na na ÀÀ þna Behavioral problems, extrapyramidal signs, and sleep na na na þþ þ þ þ þ disturbance (Onset 410 years) Attention-deficit disorder na na na þ na þþ þ Autism spectrum disorder na na na na na þþ ÀÀ CLN3 Developmental delay (learning difficulties/ þþ þ þna þþ Àþ intellectual disability, delayed language development) in a 16p11.2 deletion Unusual facial morphology na na na þ na Àþ ÀÀC Pebrel-Richard Obesity þþ þ ÀÀ þ þ À þ Neonatal hypotonia na na na na na Àþ Àþ Congenital anomalies of the kidney and urinary tract na na na þ na Àþ ÀÀ Other major finding na na na þ a þ b ÀÀ ÀÀ Abbreviation: na, data not available. aSevere kyphosis. et al bHirschprung disease and congenital joint contractures. and 2.3INTF7 (5 primer CLN3mut756R (5 designed using the genomic X99832). the presence of 5 pmol of primersdNTP, 0.004 2.3LR3 U (5 per 4 l of SuperTaq (HT Biotechnology Ltd, Cambridge, UK) in Twenty microliter of PCR samples were analyzed on a 2% agarose gel. amplification with denaturation for 1 min at 94 56 25 (Figure 2a). Briefly, 50 ng of(2.3LR3) genomic and DNA another was primer amplified spanning in thethe a deletion deletion total junction (CLN3mut756R) volume (2.3INTF7) of in combination with one primer within the deletion this locus, indicating a probe showed no 16p11.2 deletionwith or aCGH other rearrangement results. involving a Parental hemizygous karyotype deletion of and chromosome FISH 16p11.2, using which isprojects.tcag.ca/variation) the (data consistent not same shown). population according to thenumber Database of variations Genomicexcluded Variants (CNV) the (http:// presence previously ofA_16_P20443172, any described the other genomic last-deleted in imbalance, oligonucleotideA_16_P40598212, except the (Figure copy first-deleted the oligonucleotide, to 1a), oligonucleotide normal and (28 399 426–30 098 210 – Hg18), stretching from oligonucleotide protocols. Fluorescence metaphases prepared from cultured peripheral blood according toChromosome the standard analysis wasClassical performed and molecular on cytogenetics GTG-banded and RHG-banded other hematological abnormalities (Table 1). retina. Vacuolated leukocytes werenarrowing discovered of on the blood vesselsreveal cell and any count bone anomaly. spicular without Retinal pigmentations examination in showed the a peripheral from severe pale fatigability and optic chronicbehavioral constipation. disc difficulties with with aggressive crisis a in case of frustration. He suffered revealed a have a normalBy 46,XY using karyotype GTG and at RHGClassical 550 bandings, and the band molecular patient cytogenetics was level. initiallyRESULTS aCGH judged to analysis gene was performed according to Taschner Allele-specific PCR for detection ofMolecular genetics the major 1.02-kb deletion in the rithm of DNA analytics 4.0.76Genomic-copy-number (Agilent aberrations Technologies). were identifiedsisted using of a the sex-matched pool ADM-II ofFeature algo- genomic Extraction DNA (Promega, 10.5 Madison, WI, software USA). SantaTechnologies, (Agilent Clara, CA, Technologies). USA). Control The array DNA wasprotocol con- scanned (Agilent and 180 analyzed K with Whole Human180K genome Oligo oligonucleotide Microarray microarray kit,Nucleospin Agilent system, Blood L, according Macherey-Nagel, Eurl, toperformed