FREQUENCY OF FMR1 PREMUTATIONS IN A CONSECUTIVE NEWBORN POPULATION BY PCR SCREENING OF GUTHRIE BLOOD SPOTS

被引:41
作者
DAWSON, AJ [1 ]
CHODIRKER, BN [1 ]
CHUDLEY, AE [1 ]
机构
[1] UNIV MANITOBA,DEPT HUMAN GENET,WINNIPEG,MB R3E 0Z2,CANADA
关键词
D O I
10.1006/bmme.1995.1057
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The fragile X(A) or FRAXA syndrome is the most common form of familial mental retardation and is associated with a fragile site at Xq27.3. The gene responsible for the FRAXA syndrome, the FMR1 gene, has been cloned. Inactivation of the FMR1 gene is associated with amplification of a trinucleotide CGG repeat sequence and methylation of an adjacent CpG island, Previous estimates for the prevalence of the FRAXA syndrome have been based on indirect methods of chromosome analysis in institutions and community workshops for the mentally handicapped. We have analyzed the frequency of premutations of the FMR1 gene in 3002 X chromosomes of 1000 male and 1000 female consecutive newborn nonautoclaved blood spots in an anonymous, unlinked survey, The CGG repeat sizes were calculated by measuring the length of products of the PCR reaction based on the molecular size of labeled markers in a denaturing sequencing gel assay. For consistent PCR amplification a DNA microextraction was necessary, including a phenol/ chloroform series. In our population, the CGG allele ranged from 9 to 106 repeats; 97% of alleles had fewer than 40 repeats, The most frequent allele was a repeat of 28. Approximately 2.3% of alleles had CGG repeats ranging from 4 to 49 and 0.37% of alleles had repeats ranging from 50 to 59. The frequency of alleles >60 repeats in the Manitoba male population is approximately 0.13%. The use of nonautoclaved Guthrie blood spots for population screening of FRAXA premutations is not recommended, The necessity of a phenol/chloroform DNA microextraction is tedious and time consuming. The low yield of DNA (250 ng) does not allow for reanalysis by Southern of apparently homozygous females with potentially unstable CGG alleles in the 40-60 repeat range and likely underestimates premutation carrier status. (C) 1995 Academic Press, Inc.
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页码:63 / 69
页数:7
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