Article

Microduplication and Triplication of 22q11.2: A Highly Variable Syndrome

Department of Biological Sciences, University of Alberta, Edmonton, Canada.
The American Journal of Human Genetics (Impact Factor: 10.99). 06/2005; 76(5):865-76. DOI: 10.1086/429841
Source: PubMed

ABSTRACT 22q11.2 microduplications of a 3-Mb region surrounded by low-copy repeats should be, theoretically, as frequent as the deletions of this region; however, few microduplications have been reported. We show that the phenotype of these patients with microduplications is extremely diverse, ranging from normal to behavioral abnormalities to multiple defects, only some of which are reminiscent of the 22q11.2 deletion syndrome. This diversity will make ascertainment difficult and will necessitate a rapid-screening method. We demonstrate the utility of four different screening methods. Although all the screening techniques give unique information, the efficiency of real-time polymerase chain reaction allowed the discovery of two 22q11.2 microduplications in a series of 275 females who tested negative for fragile X syndrome, thus widening the phenotypic diversity. Ascertainment of the fragile X-negative cohort was twice that of the cohort screened for the 22q11.2 deletion. We also report the first patient with a 22q11.2 triplication and show that this patient's mother carries a 22q11.2 microduplication. We strongly recommend that other family members of patients with 22q11.2 microduplications also be tested, since we found several phenotypically normal parents who were carriers of the chromosomal abnormality.

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Available from: Francois P Bernier, Aug 24, 2015
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    • "[1] and 22q11.21 [2]. These syndromes, like the corresponding microdeletion syndromes at these locations, appear to be driven by nonallelic homologous recombination (NAHR) involving low-copy repeats (LCRs or segmental duplications) [3] [4] [5] [6] [7] [8]. "
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    ABSTRACT: Concurrent cryptic microdeletion and microduplication syndromes have recently started to reveal themselves with the advent of microarray technology. Analysis has shown that low-copy repeats (LCRs) have allowed chromosome regions throughout the genome to become hotspots for nonallelic homologous recombination to take place. Here, we report a case of a 7.5-year-old girl who manifests microcephaly, developmental delay, and mild dysmorphic features. Microarray analysis identified a microduplication in chromosome 17q21.31, which encompasses the CRHR1, MAPT, and KANSL1 genes, as well as a microdeletion in chromosome 7q31.33 that is localised within the GRM8 gene. To our knowledge this is one of only a few cases of 17q21.31 microduplication. The clinical phenotype of patients with this microduplication is milder than of those carrying the reciprocal microdeletions, and suggests that the lower incidence of the former compared to the latter may be due to underascertainment.
    02/2014; 2014:658570. DOI:10.1155/2014/658570
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    • "Furthermore, the chromosomal mechanism leading to the transition of a duplication in the father to a triplication in the proband is uncertain. Non-allelic homologous recombination leading to the expansion of a copy number variation during meiosis has already been described [Yobb et al., 2005]. Nevertheless, no low-copy repeats have been found at the 4q31.23 locus, suggesting that this hypothesis is unlikely. "
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    ABSTRACT: Congenital diaphragmatic hernia (CDH) has an incidence of around 1/3,000 births. The pathogenesis of this developmental anomaly remains largely unknown and the description of small chromosomal imbalances in cases of CDH is of major interest for the identification of candidate genes. We report on a tandem 4q31.23 triplication encompassing the EDNRA gene identified by array-CGH in a male presenting an isolated left postero-lateral CDH. This copy number variation was inherited from the asymptomatic father, carrier of a size-identical duplication. We demonstrate that EDNRA mRNA is over-expressed in the proband in blood tissue. Consistent with the expression of EDNRA in the developing diaphragm and the observation that the endothelin system is up-regulated in human and animal models of CDH, we conclude that the EDNRA triplication may be the cause of CDH in our patient. © 2013 Wiley Periodicals, Inc.
    American Journal of Medical Genetics Part A 01/2014; 164(1):208-12. DOI:10.1002/ajmg.a.36216 · 2.05 Impact Factor
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    • "Many aspects of the clinical phenotype of this patient, including dysmorphic features [6] [10] [12] [16], congenital heart defects [4] [7], and motor, cognitive, and behavioral disturbances, have been previously described in individuals with 22q11.2 microduplication syndrome. "
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    ABSTRACT: Chromosome 22q11.2 microduplication syndrome is characterized by a variable and usually mild phenotype and by incomplete penetrance. Neurological features of the syndrome may entail intellectual or learning disability, motor delay, and other neurodevelopmental disorders. However, seizures or abnormal EEG are reported in a few cases. We describe a 6-year-old girl with microduplication of chromosome 22q11.2 and epilepsy with continuous spikes and waves during sleep (CSWS). Her behavioral disorder, characterized by hyperactivity, impulsiveness, attention deficit, and aggressiveness, became progressively evident a few months after epilepsy onset, suggesting a link with the interictal epileptic activity characterizing CSWS. We hypothesize that, at least in some cases, the neurodevelopmental deficit seen in the 22q11.2 microduplication syndrome could be the consequence of a disorder of cerebral electrogenesis, suggesting the need for an EEG recording in affected individuals. Moreover, an array-CGH analysis should be performed in all individuals with cryptogenic epilepsy and CSWS.
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