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/lp/springer-journals/failure-to-detect-the-22q11-2-duplication-syndrome-rearrangement-among-w9wss6mKAg
- Publisher
- Springer Journals
- Copyright
- Copyright © 2008 by Brunet et al; licensee BioMed Central Ltd.
- Subject
- Biomedicine; Neurosciences; Neurology; Behavioral Therapy; Psychiatry
- eISSN
- 1744-9081
- DOI
- 10.1186/1744-9081-4-10
- pmid
- 18284679
- Publisher site
- See Article on Publisher Site
Abstract
Chromosome aberrations have long been studied in an effort to identify susceptibility genes for schizophrenia. Chromosome 22q11.2 microdeletion is associated with DiGeorge and Velocardiofacial syndromes (DG/VCF) and provides the most convincing evidence of an association between molecular cytogenetic abnormality and schizophrenia. In addition, this region is one of the best replicated linkage findings for schizophrenia. Recently, the reciprocal microduplication on 22q11.2 has been reported as a new syndrome. Preliminary data indicates that individuals with these duplications also suffer from neuropsychiatric disorders. In this study we have investigated the appropriateness of testing schizophrenia patients for the 22q11.2 microduplication. We used multiplex ligation-dependent probe amplification (MLPA) to measure copy number changes on the 22q11.2 region in a sample of 190 patients with schizophrenia. Our results corroborate the prevalence of the 22q11.2 microdeletion in patients with schizophrenia and clinical features of DG/ VCFS and do not suggest an association between 22q11.2 microduplication and schizophrenia. learning difficulties and relatively high frequency of severe Findings Low copy repeats (LCRs) on chromosome 22q11.2 medi- mental illness like schizophrenia. The majority of human ate chromosomal rearrangements leading to recurrent chromosome 22q11.2 microdeletions (87%) are ~3 Mb deletions, duplications and translocations [1]. The in size, whereas a small proportion (8%) involve smaller 22q11.2 microdeletion is responsible for the DiGeorge nested 1.5 Mb microdeletion [2]. The reciprocal microdu- and Velocardiofacial Syndromes (DG/VCFS) (OMIM plication has been reported in several individuals [3]. This #188400 and #192430). These syndromes are associated new chromosomal syndrome was identified in patients with variable phenotypic features that includes cardiac ascertained on the basis of to DG/VCFS-like features and defects, palate anomalies, characteristic physiognomy, up to 48 cases of the 22q11.2 microduplication have been Page 1 of 5 (page number not for citation purposes) Behavioral and Brain Functions 2008, 4:10 http://www.behavioralandbrainfunctions.com/content/4/1/10 reported [4]. The clinical presentation of 22q11.2 micro- disorders reported in 33% of cases [6]. In this study we duplication cases is highly variable, ranging from severe decided to investigate the appropriateness of testing schiz- congenital malformations that lead to early death, to iso- ophrenia patients for 22q11.2 microduplication. We used lated mild learning disabilities. Most of the reported indi- multiplex ligation-dependent probe amplification viduals are infants or children at present, in who the (MLPA) to measure copy number changes on 22q11.2 existence of neuropsychiatry disorders has not yet been region in a set of patients with schizophrenia. fully assessed. However, preliminary data show that indi- viduals with duplications also suffer from neuropsychiat- A total of 190 Caucasian, unrelated patients with schizo- ric disorders. Furthermore, characteristic traits of phrenia (153 men and 40 women; age 33,3 ± 8,6 years) impulsivity, aggression, oppositional defiant disorder, were included in the study. Educational levels were social immaturity, short attention spans, attention deficit divided into the following categories: 54% of patients disorder, and cognitive deficits have been reported in have primary school (1–11 years), 26% secondary school cases of 22q11.2 microduplication [3,5-8]. (12–16 years), 7% high school (17–18 years), 7% univer- sity level and finally 6% can only read and write. Patients Chromosome 22q11.2 region provides the most convinc- were diagnosed according to DSM-IV criteria as follow: ing evidence of an association between molecular cytoge- 126 paranoid, 14 disorganized, 13 undifferentiated, 9 netic abnormality and schizophrenia. residual, 13 schizoaffective disorder, 13 schizophreni form disorder and 2 cases were not specificated. All cases Although 22q11.2 microdeletion occurs in the popula- have been recruited at the department of mental health of tion at a rate of 0.016%, it has been found in up to 2% of two hospitals, from Sabadell and Terrassa, after written adult schizophrenic patients and in up to 6% of cases of informed consent approved by the ethics board of the early onset schizophrenia [9,10]. Several reports suggest Fundació Parc Taulí Health Corporation. that dosage changes in 22q11.2 genes could disrupt proc- esses required for proper brain development and/or func- A set of MLPA probes to screen copy number changes in tion, and contribute to increase schizophrenia the 22q11.2 region was developed according to the proce- susceptibility [11,12]. Several studies have suggested link- dures described elsewhere [21]. The set consists of 30 dif- age between 22q11 and schizophrenia [13-15] and it is ferent oligonucleotides that correspond to 15 different one of the best replicated linkage findings among schizo- probes, 4 of which interrogate the 3 Mb region that is typ- phrenia patients. Meta-analysis of genome scans for bipo- ically deleted in cases of DG/VCFS and the remaining 11 lar disorder and schizophrenia have also identified probes match to other regions of chromosome 22 and to chromosome 22q11-13 as one of the strongest linkage other autosomal region on chromosome 10 (Table 1). regions for both syndromes [16]. One hundred and sixty patients were analyzed with this These linkage findings indicate that mutations of genes on mix of probes. Another group of 30 individuals were also 22q11 are likely to contribute to susceptibility to schizo- analyzed using the commercial SALSA P023 MLPA- phrenia. In the same direction association studies have DiGeorge syndrome test kit (MRC-Holland, Nether- reported several genes of this region associated with risk to lands). This commercial kit consists of 39 cloned probes develop schizophrenia and bipolar disorder, including that interrogate different chromosomal regions associated PRODH, COMT, ZNF74, PCQAP, UFD1L, ZDHHC8, to DG/VCFS and Cat Eye Syndrome. In this case, the DGCR2 and SNAP29 [17,18]. In addition, neuroimaging microdeletion region is covered by seven specific probes studies revealed that 22q11.2 deletion patients exhibit a and a subtelomeric 22q13 control probe. All our MLPA pattern of cortical gray matter reduction similar to schizo- experiments contained the corresponding positive con- phrenic subjects [19]. Finally, mouse models provide evi- trols (DNA from individuals previously diagnosed as car- dences that this region is associated with schizophrenia. A riers of 22q11.2 duplications or deletions) to ensure the murine model overexpressing the mouse orthologs of sev- reliable detection of copy number gains and loses (Figure eral genes in this region (CDCrel, GP1Bβ, TBX1 and 1). WDR14) exhibits behavioral abnormalities consistent with schizophrenia traits [20]. The MLPA reactions were performed essentially as described by Schouten et al. [22]. For the data analysis we It seems extremely likely that the 22q11.2 region harbours calculated the relative probe signals using the peak heights genes that alone, or in combination, could be causally of PCR products. Briefly, the tracing data was normalized implicated in schizophrenia. Nowadays the phenotype of by dividing each probe's peak height by the average height individuals with 22q11.2 microduplication shows a wide of all peaks of the sample and then dividing this value by range of severity but some consistent findings have been the average normalized peak's height of the correspond- dysmorphic features, cognitive deficits and psychiatric ing locus of all the samples. The product of this calcula- Page 2 of 5 (page number not for citation purposes) Behavioral and Brain Functions 2008, 4:10 http://www.behavioralandbrainfunctions.com/content/4/1/10 Table 1: Probes, genes and MLPA outcome in the analysis of the 22q11.2 duplication syndrome rearrangement among patients with schizophrenia Probe Location Gene Chrom Start End Length (nt) MLPA result HIRA 22q11.21 HIRA 22 17698971 17699021 93 Del (EZ-117 and EZ-238) TBX-1 22q11.21 TBX1 22 18150824 18150883 104 Del (EZ-117 and EZ-238) COMT 22q11.21 COMT 22 18335516 18335575 110 Del (EZ-117 and EZ-238) ZDHHC8 22q11.21 ZDHHC8 22 18513602 18513661 113 Del (EZ-117 and EZ-238) RP11-307O16 22q11.22 22 20838313 20838371 101 Dup (EZ-18) RP11-722K16 22q11.22 IGLC1 22 20999611 20999670 132 Dup (EZ-149) RP11-757F24 22q11.22 IGLC1 22 21157367 21157421 97 RP11-281O23 22q11.22 IGLC1 22 21292358 21292410 95 RP11-50L23 22q11.22 IGLC1 22 21439794 21439859 124 Dup (EZ-6) RP11-264C20 22q11.22 IGLC1 22 21526749 21526796 90 Dup (EZ-6), Del (EZ-105) RP11-165G05 22q11.22 22 21655494 21655558 107 Dup (EZ-6) CARD10 22q13.1 CARD10 10 36236312 36236371 128 CXCL12 10q11.23 CXCL12 10 44192388 44192461 116 Del (EZ-96 and EZ-125) C10orf10 10q11.23 RASSF4 C10orf10 10 44792765 44792844 122 ZWINT 10q21 ZWINT 10 57789521 57789580 120 Del, deletion; Dup, duplication; EZ, schizophrenia sample. tion is termed dosage quotient (DQ). A calculated DQ Our study indicates that MLPA is a suitable, easy, rapid value below 0.65 was considered as indicative of a dele- and cost-effective method to seek for copy number varia- tion, and values above 1.3 are indicative of duplications. tions (microdeletions and microduplications) in patients suffering from psychiatric disorders. Furthermore, our Among the 190 schizophrenic patients analyzed, we iden- results confirm the prevalence of the 22q11.2 microdele- tify two cases (EZ-117 and EZ-238) with the 22q11.2 tion in patients with schizophrenia and other clinical fea- microdeletion. This incidence of about 1% is in agree- tures of DG/VCFS, but do not indicate any association ment with previous estimates in the literature [23,24]. We with the 22q11.2 microduplication. We conclude that did not detect the reciprocal 22q11.2 microduplication. screening for 22q11 microduplication in patients with The deleted samples were analyzed with both the in- schizophrenia is not indicated. house and commercial MLPA assays, with similar DQ val- ues below the 0.65 threshold. A confirmatory FISH analy- Abbreviations sis was also performed (data not shown). Both patients LCRs: Low copy repeats, DG/VCFS: DiGeorge and Velo- showed common manifestations associated with DG/ cardiofacial Syndromes, MLPA: Multiplex ligation- VCFS, including malformations of the cardiovascular sys- dependent probe amplification, FISH: Flourescence in tem (aberrant origin of subclavian artery/pulmonary sten- situ hybridization, ADHD: Attention-deficit hyperactivity osis), facial dysmorphic features (long face, small ears, disorder narrow palpebral fissures, prominent tubular nose), velo- pharingeal insufficiency with severe hipernasality, motor Competing interests delay, cognitive deficit and mild mental retardation. The author(s) declare that they have no competing inter- These two patients with the 22q11.2 microdeletion were ests. girls that were noted to have history of learning and behavioural problems in the school. Both cases are diag- Authors' contributions nosed as hebephrenic schizophrenia with early age of ABparticipates in the design of the study, carried out the onset (12–13 years). molecular genetic studies and drafted the manuscript. LLAparticipate in the design of the study and helped to Subsequent family analyses in the parents showed the draft the manuscript. TPcontributed with samples collec- 22q11.2 microdeletion in the mother of one patient. The tion of patients and clinical characterization. RGand mother with same facial appearance than her daughter VVmembers of the Psychiatric Genetics Network Group showed paranoid schizophrenia and mild mental retarda- participated in the conception, design of the study; data tion. This family has another offspring, a boy who was analysis and drafting of the manuscript. EGcontributed diagnosed with attention-deficit hyperactivity disorder with clinical characterization of patients with 22q11.2 (ADHD) during childhood. He proved to be normal by microdeletion. XEand MGparticipated in the conception, FISH analyses (not shown). design and coordination of the study; data analysis and drafting of the manuscript. Page 3 of 5 (page number not for citation purposes) Behavioral and Brain Functions 2008, 4:10 http://www.behavioralandbrainfunctions.com/content/4/1/10 syndrome Figure 1 MLPA electropherograms showing the peaks from the probes set used in the analysis of the chromosome 22q11.2 duplication MLPA electropherograms showing the peaks from the probes set used in the analysis of the chromosome 22q11.2 duplication syndrome. Specific probes for the chromosome 22q11.2 region (HIRA, TBX-1, COMT and ZDHHC8) are indicated with arrows. A: A 22q11.2 microdeletion trace. B: A normal sample trace. C: A 22q11.2 microduplication trace. All the authors read and approved the final manuscript. References 1. Edelmann L, Pandita RK, Spiteri E, Funke B, Goldberg R, Palanisamy N, Chaganti RS, Magenis E, Shprintzen RJ, Morrow BE: A common Acknowledgements molecular basis for rearrangement disorders on chromo- The authors thank Dr. Heather McDermid and Twila M. Yobb for providing some 22q11. Hum Mol Genet 1999, 8(7):1157-1167. sample with the 22q11.2 microduplication. We thank also all the patients 2. Edelmann L, Pandita RK, Morrow BE: Low-copy repeats mediate the common 3-Mb deletion in patients with velo-cardio- for participation in the study and all clinicians for their valuable contribu- facial syndrome. Am J Hum Genet 1999, 64(4):1076-1086. tion. 3. 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Proc Natl Acad Sci U S A 2005, available free of charge to the entire biomedical community 102(52):19132-19137. 21. [http://www.mrc-holland.com]. peer reviewed and published immediately upon acceptance 22. Schouten JP, McElgunn CJ, Waaijer R, Zwijnenburg D, Diepvens F, cited in PubMed and archived on PubMed Central Pals G: Relative quantification of 40 nucleic acid sequences by multiplex ligation-dependent probe amplification. Nucleic yours — you keep the copyright Acids Res 2002, 30(12):e57. BioMedcentral Submit your manuscript here: http://www.biomedcentral.com/info/publishing_adv.asp Page 5 of 5 (page number not for citation purposes)
Journal
Behavioral and Brain Functions – Springer Journals
Published: Feb 19, 2008