Mutation analysis of the MECP2 gene in British and Italian Rett syndrome females

Vacca, Marcella; Filippini, F.; Budillon, Alberta; Rossi, Valeria; Mercadante, Grazia; Manzati, Elisa; Gualandi, Francesca; Bigoni, Stefania; Trabanelli, Cecilia; Pini, Giorgio; Calzolari, Elisa; Ferlini, Alessandra; Meloni, Ilaria; Hayek, Joussef; Zappella, Michele; Renieri, Alessandra; D’Urso, Michele; D’Esposito, Maurizio; Macdonald, Fiona; Kerr, Alison; Dhanjal, Seema; Hultén, Maj

doi:10.1007/s001090000155

Cited by 52 publications

(36 citation statements)

References 22 publications

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“…Mutations were identified in nine of 13 cases (Table I), yielding a mutation rate of 69%, which is consistent with previous reports [De Bona et al, 2000;Auranen et al, 2001;Bourdon et al, 2001;Laccone et al, 2001;Nicolao et al, 2001;Vacca et al, 2001]. Eight of the nine mutations (89%) were C to T transitions at CpG dinucleotides.…”

Section: Resultssupporting

confidence: 85%

Balanced X chromosome inactivation patterns in the Rett syndrome brain

Shahbazian¹,

Sun²,

Zoghbi³

2002

Am. J. Med. Genet.

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In Rett syndrome (RTT), an X-linked disorder essentially limited to females, neurological development goes awry. Causing this disarray in neuronal function is a mutated form of a protein known as methyl-CpG-binding protein 2 (MeCP2). Because the MECP2 gene is subject to X chromosome inactivation (XCI) in females, a number of studies have addressed whether the percentage of cells inactivating the normal vs. mutant chromosome in heterozygous females influences the phenotypic outcome of MECP2 mutations. Because most of these studies measured XCI in peripheral blood, however, interpretation of the results requires the assumption that XCI patterns in blood are representative of those in the brain, the primarily affected tissue. Here, we have analyzed the MECP2 sequence and XCI status in 13 brains of RTT patients. Mutations were identified in nine of the cases, with eight of these representing C to T transitions at CpG dinucleotides, and one being a novel frameshift mutation (765delA). Patterns of XCI were balanced in 10 of 10 cases for which the assay was informative. As previous studies have shown that a majority of RTT patients have balanced XCI patterns in peripheral blood, our results suggest that the pattern in blood is an accurate indicator of XCI patterns in the brain for a majority of cases, but there are some notable exceptions that this study may help explain. Given the correlation between balanced XCI and classic RTT, these results suggest that a certain percentage of neurons expressing the mutant MECP2 gene may be required for RTT to become manifest.

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Section: Resultssupporting

confidence: 85%

Balanced X chromosome inactivation patterns in the Rett syndrome brain

Shahbazian¹,

Sun²,

Zoghbi³

2002

Am. J. Med. Genet.

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“…We investigated eight cases of classical RTT and six cases of PSV, all negative for the MECP2 mutation [De Bona et al, 2000;Vacca et al, 2001]. All the girls with classical RTTwere diagnosed according to the international criteria based on the Rett Syndrome Diagnostic Criteria Work Group [Trevathan and Moser, 1988].…”

Section: Materials and Methods Patientsmentioning

confidence: 99%

Real-time quantitative PCR as a routine method for screening large rearrangements in Rett syndrome: Report of one case of MECP2 deletion and one case of MECP2 duplication

et al. 2004

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Mutations in the X-linked methyl-CpG-binding protein 2 gene (MECP2) are found in 70-80% of cases of classical Rett syndrome (RTT) and in about 50% of cases of preserved speech variant (PSV). This high percentage of MECP2 mutations, especially in classical RTT cases, suggests that another major RTT locus is unlikely. Missed mutations may be due to the limited sensitivity of the methodology used for mutation scanning and/or the presence of intronic mutations. In a double-copy gene, such as MECP2 in females, current methodologies (e.g., DGGE, SSCP, DHPLC, direct sequencing) are prone to miss gross rearrangements. Three previous reports during 2001-2003 have shown the presence of large deletions in a fraction of MECP2-negative classical RTT patients. We developed a reliable, single tube, quantitative PCR assay for rapid determination of MECP2 gene dosage. This method involves a multiplex reaction using a FAM labeled TaqMan probe with a TAMRA quencher derived from MECP2 exon 4 and two primers derived from the same exon and RNAaseP as an internal reference. The copy number of the MECP2 gene was determined by the comparative threshold cycle method (ddCt). Each sample was run in quadruplicate. We validated this assay through the analysis of 30 healthy controls (15 female and 15 male) and we then applied this method to eight classical RTT and six PSV patients, all negative for MECP2 mutations. We identified gross rearrangements in two patients: a deletion in a classical RTT patient and a duplication in a PSV patient. Our results confirm that a fraction of MECP2-negative RTT cases have MECP2 gross rearrangements and we propose real-time quantitative PCR as a simple and reliable method for routine screening of MECP2 in addition to DHPLC analysis.

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“…It is characterized by mental retardation, loss of acquired skills (especially hand use and communicative language), and deceleration of head growth. Mutations in the MECP2 (MIM# 300005) gene have been detected in a large proportion of Rett patients and have been reported worldwide Bienvenu et al, 2000;Cheadle et al, 2000;Hoffbuhr et al, 2001;Laccone et al, 2001;Vacca et al, 2001; Van den Veyver and Zoghbi, 2000;Wan et al, 1999]. The MECP2 gene comprises four exons and three introns [Reichwald et al, 2000].…”

Section: Introductionmentioning

confidence: 98%

Large deletions of the MECP2 gene detected by gene dosage analysis in patients with Rett syndrome

et al. 2004

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MECP2 mutations are responsible for Rett syndrome (RTT). Approximately a quarter of classic RTT cases, however, do not have an identifiable mutation of the MECP2 gene. We hypothesized that larger deletions arising from a deletion prone region (DPR) occur commonly and are not being routinely detected by the current PCR-mediated screening strategies. We developed and applied a quantitative PCR strategy (qPCR) to samples referred for diagnostic assessment from 140 patients among whom RTT was strongly suspected and from a second selected group of 31 girls with classical RTT. Earlier MECP2 mutation screening in both groups of patients had yielded a wild-type result. We identified 10 large deletions (7.1%) within the first group and five deletions in the second group (16.1%). Sequencing of the breakpoints in 11 cases revealed that eight cases had one breakpoint within the DPR. Among seven cases, the breakpoint distant to the DPR involved one of several Alu repeats. Sequence analysis of the junction sequences revealed that eight cases had complex rearrangements. Examination of the MECP2 genomic sequence reveals that it is highly enriched for repeat elements, with the content of Alu repeats rising to 27.8% in intron 2, in which there was an abundance of breakpoints among our patients. Furthermore, a perfect chi sequence, known to be recombinogenic in E. coli, is located in the DPR. We propose that the chi sequence and Alu repeats are potent factors contributing to genomic rearrangement. We suggest that routine mutation screening in MECP2 should include quantitative analysis of the genomic sequences flanking the DPR.

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Mutation analysis of the MECP2 gene in British and Italian Rett syndrome females

Cited by 52 publications

References 22 publications

Balanced X chromosome inactivation patterns in the Rett syndrome brain

Balanced X chromosome inactivation patterns in the Rett syndrome brain

Real-time quantitative PCR as a routine method for screening large rearrangements in Rett syndrome: Report of one case of MECP2 deletion and one case of MECP2 duplication

Large deletions of the MECP2 gene detected by gene dosage analysis in patients with Rett syndrome

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