Prenatal detection of Fra(X)(q27.3) in female identical twins: Reliability of low level cytogenetic prenatal expression in females

Jenkins, Edmund C.; Brown, W. Ted; Schonberg, Steven; Krawczun, Michael S.; Goldberg, James D.; Golbus, Mitchell S.

doi:10.1002/ajmg.1320430120

Am. J. Med. Genet.

1992

DOI: 10.1002/ajmg.1320430120

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Prenatal detection of Fra(X)(q27.3) in female identical twins: Reliability of low level cytogenetic prenatal expression in females

Edmund C. Jenkins

W. Ted Brown

Steven Schonberg

et al.

Abstract: 1. Low frequencies, perhaps 1 or 2%, or a few positive cells in AFCs, are likely to increase in magnitude when confirmed in whole blood cultures either pre- or postnatally. 2. It appears likely that the risk is low for false positive results in AFCs when low frequencies of fra(X)(q27.3) are encountered.

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Cited by 5 publications

(1 citation statement)

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“…The X chromosome inactivation ratio has also been argued as being of importance (Abrams et al 1994). Low levels of cytogenetic expression of fragile X syndrome in identical female twin foetuses were found to be reliable for prenatal detection (Jenkins et al 1992). The importance of a psychosocial contribution to the fragile X clinical phenotype is suggested in a study of monozygotic twin girls with fragile X syndrome but discordant for cognitive ability (Mazzocco et al 1994).…”

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Monozygotic boys with fragile X syndrome

Sheldon

Turk

2000

Develop Med Child Neuro

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Monozygotic twin boys with fragile X syndrome underwent thorough genetic, psychiatric, neurological, and language evaluations at 10 years of age. They both demonstrated physical features, speech and language difficulties, social problems, and attentional deficits that characterize the behavioural phenotype of fragile X syndrome. Despite identical genetic constitutions, there were important developmental and behavioural heterogeneities. Twin A showed less social interaction and symbolic play and more speech and language dysfunction than twin B. Twin A also had significantly larger caudate volumes. It is suggested that the Xq27.3 anomaly may not be sufficient to account for all the behavioural phenotypic and neuroanatomical features of fragile X syndrome.

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confidence: 99%

Monozygotic boys with fragile X syndrome

Sheldon

Turk

2000

Develop Med Child Neuro

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Reverse mutations in the fragile X syndrome

et al. 1996

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Three females were identified who have apparent reversal of fragile X premutations. Based on haplotype analysis of nearby markers, they were found to have inherited a fragile X chromosome from their premutation carrier mothers, and yet had normal size FMR1 repeat alleles. The changes in repeat sizes from mother to daughter was 95 to 35 in the first, 145 to 43 in the second, and 82 to 33 in the third. In the first family, mutations of the nearby microsatellites FRAXAC2 and DXS548 were also observed. In the other two, only mutations involving the FMR1 repeats were found. We suggest differing mutational mechanisms such as gene conversion versus DNA replication slippage may underlie such reversions. We estimate that such revertants may occur among 1% or less of premutation carrier offspring. Our results indicate that women identified to be carriers by linkage should be retested by direct DNA analysis. © 1996 Wiley‐Liss, Inc.

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Fragile X induction systems in CVS cultures: Effect on cytogenetic, PCR, and genomic southern blot DNA analyses of the FMR‐1 gene

et al. 1994

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Low fragile X frequencies have been commonly observed in chorionic villus sample (CVS) cultures, compared to subsequent analysis in whole blood or products of conception (POC). To investigate possible mechanisms for this effect, CVS cultures from a previously identified fragile X positive male, were restudied and compared to subsequent POC cultures from lung, muscle, skin, and thymus. Cultures were exposed, for the last 24 hours before harvesting, to FUdR, excess thymidine, and a combination of both. For CVS, only those cultures that were exposed to a combination of FUdR and excess thymidine showed positive cytogenetic findings (1/90 or 1.1%), agreeing with our original positive cytogenetic results (2/86 or 2.3%) for cultures exposed to excess thymidine. Fragile X frequencies in the POC tissues from this fetus increased to an average of 14%. PCR analyses showed full mutations (> 200 CGG repeats) in uninduced CVS cultures but induced cultures exhibited apparently smaller sizes in the range of 120-180 repeats. The results showed variability. In one instance, the banding pattern from one of the uninduced cultures was similar to the results where cultures were exposed to a double induction system. When PCR analyses were conducted on induced POC cultures, full mutations were observed in virtually all samples. Southern blot genomic analysis using probe StB12.3 showed an unmethylated full mutation in CVS cultures. Southern blot patterns from cultures of muscle revealed size variations of DNA bands in the premutation range representing unmethylated DNA as well as methylated full mutations. Finally, variations were also observed in lung and skin cultures, compared to CVS and muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

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Prenatal detection of Fra(X)(q27.3) in female identical twins: Reliability of low level cytogenetic prenatal expression in females

Cited by 5 publications

References 17 publications

Monozygotic boys with fragile X syndrome

Monozygotic boys with fragile X syndrome

Reverse mutations in the fragile X syndrome

Fragile X induction systems in CVS cultures: Effect on cytogenetic, PCR, and genomic southern blot DNA analyses of the FMR‐1 gene

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