title: FMR1 CGG repeat distribution and linked microsatellite-SNP haplotypes in normal Mexican Mestizo and indigenous populations.
abstract: The (CGG)n repeat size distribution in the FMR1 gene was studied in healthy individuals: 80 X chromosomes of Mexican Mestizos from Mexico City and 33 X chromosomes of Mexican Amerindians from three indigenous communities (Purepechas, Nahuas, and Tzeltales), along with alleles and haplotypes defined by two microsatellite polymorphic markers (DXS548 and FRAXAC1) and two single nucleotide polymorphisms (FMRA and FMRB). Genetic frequencies of Mestizo and Amerindian subpopulations were statistically similar in almost all cases and thus were considered one population for comparisons with other populations. Sixteen (CGG)n alleles in the 17-38 size range were observed, and the most common were the 25 (38.0%), 26 (28.3%), and 24 (12.3%) repeat alleles. This pattern differs from most other populations reported, but a closer relation to Amerindian, European, and African populations was found, as expected from the historical admixture that gave rise to Mexican Mestizos. The results of the CA repeats analysis at DXS548-FRAXAC1 were restricted to nine haplotypes, of which haplotypes 7-4 (52.2%), 8-4 (23.8%), and 7-3 (11.5%) were predominant. The modal haplotype 7-4, instead of the nearly universal haplotype 7-3, had been reported exclusively in Eastern Asian populations. Likewise, only seven different FRAXAC1-FMRA-FMRB haplotypes were observed, including five novel haplotypes (3TA, 4TA, 3 - A, 4 - A, and 5 - A), compared with Caucasians. Of these, haplotypes - A (78.7%) and 3 - A (13.2%) were the most common in the Mexican population. These data suggest a singular but relatively low genetic diversity at FMR1 in the studied Mexican populations that may be related to the recent origin of Mestizos and the low admixture rate of Amerindians.
authors.affiliation: Unidad de Investigación Médica en Genética Humana, Hospital de Pediatría, CMN Siglo XXI-IMSS, 06725 Mexico City, Mexico, USA.
authors.forename: Xóchitl Adriana
authors.initials: XA
authors.lastname: Felix-López
authors.forename: Raúl
authors.initials: R
authors.lastname: Argüello-García
authors.forename: Ricardo M
authors.initials: RM
authors.lastname: Cerda-Flores
authors.forename: Rosenda I
authors.initials: RI
authors.lastname: Peñaloza-Espinoza
authors.forename: Leonor
authors.initials: L
authors.lastname: Buentello-Malo
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Estrada-Mena
authors.forename: Manuel
authors.initials: M
authors.lastname: Ramos-Kuri
authors.forename: Fabio Salamanca
authors.initials: FS
authors.lastname: Gómez
authors.forename: Diego Julio
authors.initials: DJ
authors.lastname: Arenas-Aranda
mesh_terms: D001483:Base Sequence; D005260:Female; D005600:Fragile X Syndrome / Q000453:epidemiology* / Q000235:genetics; D005787:Gene Frequency; D005828:Genetics, Population; D006239:Haplotypes; D006801:Humans; D007198:Indians, North American / Q000235:genetics*; D008297:Male; D008800:Mexico; D018895:Microsatellite Repeats