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Title: Direct mutation analysis of 495 patients for fragile X carrier status/proband diagnosis

Abstract

With the cloning of the FMR-1 gene, direct mutation analysis is possible for fragile X syndrome. We have analyzed 495 patients using the StB12.3 probe/EcoRI/EagI system of Rousseau et al. and 167 of these also with PCR analysis according to Brown et al. For 28 patients requesting carrier status due to a family history of fragile X, 10 were shown to have either premutations or full mutations; for the remainder with varied backgrounds, 1 in 182 was shown to carry a premutation. For proband diagnosis, 7 of 14 with a fragile X family history carried a full mutation; 11 of 271 with other family histories carried the full mutation. 13 refs., 1 tab.

Authors:
; ; ;  [1]
  1. Vivigen/Integrated Genetics, Santa Fe, NM (United States)
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
62055
Resource Type:
Journal Article
Resource Relation:
Journal Name: American Journal of Medical Genetics; Journal Volume: 51; Journal Issue: 4; Other Information: PBD: 15 Jul 1994
Country of Publication:
United States
Language:
English
Subject:
55 BIOLOGY AND MEDICINE, BASIC STUDIES; HUMAN X CHROMOSOME; CHROMOSOMAL ABERRATIONS; GENE MUTATIONS; GENES; DNA-CLONING; PATIENTS; HEREDITARY DISEASES; MENTAL DISORDERS; PHENOTYPE; DNA; POLYMERASE CHAIN REACTION

Citation Formats

Kaplan, G., Kung, M., McClure, M., and Cronister, A. Direct mutation analysis of 495 patients for fragile X carrier status/proband diagnosis. United States: N. p., 1994. Web. doi:10.1002/ajmg.1320510441.
Kaplan, G., Kung, M., McClure, M., & Cronister, A. Direct mutation analysis of 495 patients for fragile X carrier status/proband diagnosis. United States. doi:10.1002/ajmg.1320510441.
Kaplan, G., Kung, M., McClure, M., and Cronister, A. Fri . "Direct mutation analysis of 495 patients for fragile X carrier status/proband diagnosis". United States. doi:10.1002/ajmg.1320510441.
@article{osti_62055,
title = {Direct mutation analysis of 495 patients for fragile X carrier status/proband diagnosis},
author = {Kaplan, G. and Kung, M. and McClure, M. and Cronister, A.},
abstractNote = {With the cloning of the FMR-1 gene, direct mutation analysis is possible for fragile X syndrome. We have analyzed 495 patients using the StB12.3 probe/EcoRI/EagI system of Rousseau et al. and 167 of these also with PCR analysis according to Brown et al. For 28 patients requesting carrier status due to a family history of fragile X, 10 were shown to have either premutations or full mutations; for the remainder with varied backgrounds, 1 in 182 was shown to carry a premutation. For proband diagnosis, 7 of 14 with a fragile X family history carried a full mutation; 11 of 271 with other family histories carried the full mutation. 13 refs., 1 tab.},
doi = {10.1002/ajmg.1320510441},
journal = {American Journal of Medical Genetics},
number = 4,
volume = 51,
place = {United States},
year = {Fri Jul 15 00:00:00 EDT 1994},
month = {Fri Jul 15 00:00:00 EDT 1994}
}
  • The cloning of the FMR-1 gene and the identification of an expanded CGG repeat in DNA of fragile X patients has made reliable DNA diagnosis feasible. Southern blotting and PCR assays of the CGG repeat in an unselected series of 236 mentally retarded subjects resulted in the identification of 10 new fragile X families. Reevaluation of previously assessed fragile X families resulted in the first observation of the presence of a reversal of mutation in the FMR-1 gene. 21 refs., 1 fig., 1 tab.
  • The Collaborative Prospective Fragile X Study was established to collect information on the pregnancy outcome of women known to be carriers of the fragile X syndrome. The prospective design of this study allows collection of ascertainment-free data and, thereby, avoids biases caused by sampling problems encountered in retrospective family studies. The results of 337 submitted cases are summarized. These data show that the segregation of the fragile X mutation is normal and the sex ratio of conceptuses is as expected for a prenatal sample. There is no excess of dizygotic twinning among the pre- or full mutation carrier females. Datamore » are limited at this time but provide a suggestion that the risk of expansion to the full mutation may be correlated with maternal age and to the parental origin of premutation of carrier women. More data are needed to confirm these suggested trends. The prospective data base provides a valuable resource to continue to examine factors in an unbiased fashion. 21 refs., 5 tabs.« less
  • The authors report the results of a 14-center collaborative study of genotype-phenotype correlations in 318 fragile X families; these families comprised 2,253 individuals, 1,344 of whom carried a fragile X mutation and 693 of whom had a typical full fragile X mutation. This study demonstrates that direct DNA diagnosis establishes the genotype at the FRAXA-FMR-1 locus. There was a significantly higher prevalence of [open quotes]mosaic[close quotes] cases among males who carry a full mutation (12%) than among females who carry a full mutation (6%); the mosaic males had a larger expansion than did the mosaic females. Mental status of premutatedmore » individuals did not differ from that of those with a normal genotype. Both the abnormal methylation of the FMR-1-EagI site and the size of the expansion were highly correlated with cytogenetics, facial dysmorphism, macroorchidism, and mental retardation (MR). Among female carriers of a full mutation, those with MR had significantly larger expansion than did those without MR. Among 164 independent couples, 3 unrelated husbands carried a premutation that suggests that the prevalence of fragile X premutations in the general population is [approximately] 0.9% of the X chromosomes. The data validate the use of direct DNA testing for fragile X diagnosis as well as for carrier identification and support and complete the established relationships among the DNA results and the cytogenetic, physical, and psychological aspects of the disease. 38 refs., 1 fig., 9 tabs.« less
  • Fragile X syndrome is the most common inherited form of mental retardation. In fragile X syndrome, the underlying mutation is caused by an expansion of the CTG triplet in the 5{prime} untranslated region of the FMR-1 gene located at Xq27.3 and diagnosed by methylation of the associated CpG island. This disorder becomes clinically manifested when the mutation is caused by an expansion of (CGG)n reaching a threshold of about 600bp (200 repeats). The number of inserted repeats increases through the generation. We have analyzed fragile X syndrome by 4 different methods: Southern blot, radioactive PCR, polyacrylamide gel and DIG DNAmore » labeling/detection techniques. Southern blot and DIG DNA labeling/detection by double DNA digestion with EcoRI and EagI reveals both the presence of the mutation and the methylation status. Radioactive PCR and silver-stained polyacrylamide gel is a rapid and sensitive technique to define the unaffected carriers and NTMs, but it is difficult to amplify such a highly GC-rich sequence. Further testing in other fragile X patients is currently in progress.« less
  • Notwithstanding the use of comparable molecular protocols, description and measurement of the fra(X) (fragile X) mutation may vary according to its appearance as a discrete band, smear, multiple bands, or mosaic. Estimation of mutation size may also differ from one laboratory to another. We report on the description of a mutation size estimate for a large sample of individuals tested for the fra(X) pre- or full mutation. Of 63 DNA samples evaluated, 45 were identified previously as fra(X) pre- or full mutations. DNA from 18 unaffected individuals was used as control. Genomic DNA was extracted from peripheral blood, and DNAmore » fragments from each of four laboratories were sent to a single center where Southern blots were prepared and hybridized with the pE5.1 probe. Photographs from autoradiographs were returned to each site, and raters blind to the identity of the specimens were asked to evaluate them. Raters` estimates of mutation size compared favorably with a reference test. Intrarater reliability was good to excellent. Variability in mutation size estimates was comparable across band types. Variability in estimates was moderate, and was significantly correlated with absolute mutation size and band type. 9 refs., 1 fig., 3 tabs.« less