J Genet Med.  2016 Jun;13(1):14-19. 10.5734/JGM.2016.13.1.14.

Carrier screening for (CGG)n repeat expansion of FMR1 gene in Korean women

Affiliations
  • 1Genetics Laboratory, Fertility Center of CHA Gangnam Medical Center, Seoul, Korea. shshim@cha.ac.kr
  • 2Department of Obstetrics and Gynecology, CHA Gangnam Medical Center, Seoul, Korea.
  • 3Department of Biomedical Science, College of Life Science, CHA University, Seoul, Korea.

Abstract

PURPOSE
We examined the prevalence and CGG/AGG repeat structure of expanded alleles of the FMR1 gene in preconceptional and pregnant Korean women.
MATERIALS AND METHODS
The CGG repeats in the FMR1 genes of 1,408 women were analyzed by polymerase chain reaction and Southern blot analysis. To estimate the prevalence of expansion alleles, the individuals were divided into low risk and high risk group.
RESULTS
Within this population, 98.4% had normal alleles and 1.6% had abnormal alleles including intermediate (0.6%), premutation (0.5%), full mutation (0.1%), and hemizygous (0.4%) alleles. There were 2 premutation alleles (1:666, 95% confidence interval [CI] 1:250-1,776) in the low risk group and 5 premutation alleles (1:15, 95% 1:6-36) in the high risk group. There were 8 intermediate alleles (1:167, 95% CI 1:130-213) in the low risk group and 1 intermediate alleles (1:76, 95% CI 1:11-533) in the high group. Six of the 7 premutation alleles did not contain AGG interruptions within the repeats and 1 had a single AGG interruption. Four of the 9 intermediate alleles contained 2-3 AGG, 4 had a single AGG, and 1 had no AGG interruptions.
CONCLUSION
Our study demonstrates the prevalence and CGG/AGG structure of expansion alleles in Korean women. The identified premutation prevalence is higher than that of other Asian populations and lower than that of Caucasian populations. Although our study is limited by size and population bias, our findings could prove useful for genetic counseling of preconceptional or pregnant women.

Keyword

Fragile X syndrome; Trinucleotide repeat expansion; Primary ovarian failure; Gene frequency; Carrier state
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