Frequency of FMR1 premutation carriers and rate of expansion to full mutation in a retrospective diagnostic FMR1 Korean sample

Authors

  • J.-H. Jang,

    1. Green Cross Laboratories, Yongin-si, Gyeonggi-do, Republic of Korea
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    • These authors contributed equally to this work.

  • K. Lee,

    1. Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
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    • These authors contributed equally to this work.

  • E.-H. Cho,

    Corresponding author
    1. Green Cross Laboratories, Yongin-si, Gyeonggi-do, Republic of Korea
    • Corresponding authors: Dr Eun-Hae Cho, Medical Genome Research Center, Green Cross Laboratories, 314 Bojung-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-913, Republic of Korea.

      Tel.: +82 31 260 9216;

      fax: +82 31 260 9638;

      e-mail: ehcho@gclabs.co.kr

      and

      Dr Chang-Seok Ki, Department of Laboratory Medicine and Genetics, Samsung Medical Center, 81 Irwon-ro, Gangnam-gu, Seoul 135-710, Republic of Korea.

      Tel.: +82 2 3410 2709;

      fax: +82 2 3410 2719;

      e-mail: changski@skku.edu

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  • E.-H. Lee,

    1. Green Cross Laboratories, Yongin-si, Gyeonggi-do, Republic of Korea
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  • J.-W. Kim,

    1. Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
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  • C.-S. Ki

    Corresponding author
    1. Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
    • Corresponding authors: Dr Eun-Hae Cho, Medical Genome Research Center, Green Cross Laboratories, 314 Bojung-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-913, Republic of Korea.

      Tel.: +82 31 260 9216;

      fax: +82 31 260 9638;

      e-mail: ehcho@gclabs.co.kr

      and

      Dr Chang-Seok Ki, Department of Laboratory Medicine and Genetics, Samsung Medical Center, 81 Irwon-ro, Gangnam-gu, Seoul 135-710, Republic of Korea.

      Tel.: +82 2 3410 2709;

      fax: +82 2 3410 2719;

      e-mail: changski@skku.edu

    Search for more papers by this author

  • There is no conflict of interest with any financial organization.

Abstract

Detection of female premutation (PM) carriers of fragile X syndrome may be important in that a PM allele from the mother can expand to a full mutation (FM) when transmitted to the fetus. Although the PM carrier frequency might be different in varying populations, there is a little data on the Korean population. Furthermore, the risks of expansion to FM have not been studied in Korean PM carriers. In this retrospective study, we estimated the female PM carrier frequency and the risks of expansion to FM in Korean diagnostic samples collected for FMR1 gene testing. Of 10,241 pre-conceptional or pregnant women, 13 PM [1 in 788; 95% confidence interval (CI), 1/1 250–1/455] and 75 intermediate allele carriers (1 in 137; 95% CI, 1/172–1/110) were identified. In 26 prenatal diagnoses cases, the PM allele was transmitted to the fetus in 13 pregnancies (50%), and five of these expanded to FM. All of the maternal alleles exceeding 70 repeats expanded to FM. In conclusion, the PM frequency in Korean diagnostic samples was lower than that reported in Western populations, while the risk for FM expansion in alleles exceeding 70 repeats might be higher than expected based upon previous reports.

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