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Genetic cluster of fragile X syndrome in a Colombian district

  • Saldarriaga, Wilmar1, 2, 3
  • Forero-Forero, Jose Vicente2, 3
  • González-Teshima, Laura Yuriko2, 3
  • Fandiño-Losada, Andrés3, 4
  • Isaza, Carolina1, 3
  • Tovar-Cuevas, Jose Rafael5
  • Silva, Marisol6
  • Choudhary, Nimrah S.6
  • Tang, Hiu-Tung6
  • Aguilar-Gaxiola, Sergio7
  • Hagerman, Randi J.8, 9
  • Tassone, Flora6, 8
  • 1 Universidad del Valle, School of Basics Sciences, Cali, Colombia , Cali (Colombia)
  • 2 Hospital Universitario del Valle, School of Medicine, Universidad del Valle, Cali, Colombia , Cali (Colombia)
  • 3 Universidad del Valle, Research Group in Congenital & Perinatal Malformations, Dysmorphology and Clinical Genetics (MACOS), Cali, Colombia , Cali (Colombia)
  • 4 Universidad del Valle, School of Public Health, Cali, Colombia , Cali (Colombia)
  • 5 Universidad del Valle, School of Statistics, Cali, Colombia , Cali (Colombia)
  • 6 University of California, Department of Biochemistry and Molecular Medicine, Davis, CA, USA , Davis (United States)
  • 7 University of California, Davis Health, Department of Internal Medicine, Sacramento, CA, USA , Sacramento (United States)
  • 8 Davis Medical Center, Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California, Sacramento, CA, USA , Sacramento (United States)
  • 9 Davis Medical Center, Department of Pediatrics, University of California, Sacramento, CA, USA , Sacramento (United States)
Published Article
Journal of Human Genetics
Springer Nature
Publication Date
Jan 29, 2018
DOI: 10.1038/s10038-017-0407-6
Springer Nature


Background:Fragile X syndrome (FXS) is the most common cause of inherited intellectual disabilities and autism. The reported prevalence of the full mutation (FM) gene FMR1 in the general population is 0.2–0.4 per 1000 males and 0.125–0.4 per 1000 females.Population screening for FMR1 expanded alleles has been performed in newborns and in an adult population. However, it has never been carried out in an entire town.Ricaurte is a Colombian district with 1186 habitants, with a high prevalence of FXS, which was first described by cytogenetic techniques in 1999.Methods:Using a PCR-based approach, screening for FXS was performed on blood spot samples obtained from 926 (502 males and 424 females) inhabitants from Ricaurte, accounting for 78% of total population.Results:A high prevalence of carriers of the expanded allele was observed in all FXS mutation categories. Using the Bayesian methods the carrier frequency of FM was 48.2 (95% Credibility Region CR: 36.3–61.5) per 1000 males and 20.5 (95% CR:13.5–28.6) per 1000 females; the frequency of premutation carrier was 14.1 (95% RC: 8.0–21.7) per 1000 males (95% RC: 8.0–21.7 per 1000 males) and 35.9 (95% RC: 26.5–46.2) per 1000 for females (95% RC: 26.5–46.2 per 1000 females), and gray zone carrier was 13.4 (95% RC: 7.4–20.7) per 1000 males (95% RC: 7.4–20.7 per 1000 males) and 42.2 (95% RC: 32.2–53.8) per 1000 for females (95% RC: 32.2–53.8 per 1000 females). Differences in carrier frequencies were observed for premutation and FM alleles between natives and non-natives.Conclusions:This study shows that in Ricaurte the carrier frequencies of FMR1 expanded alleles (premutations and FMs) are higher than those reported in the literature, suggesting that Ricaurte constitutes a genetic cluster of FXS.

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