Genetic Diversity at the FMR1 Locus in Mexican Population

Rosales-Reynoso, Mónica Alejandra; Mendoza-Carrera, Francisco; Troyo-Sanromán, Rogelio; C, Medina; Barros‐Núñez, Patricio

doi:10.1016/j.arcmed.2004.05.005

Cited by 11 publications

(10 citation statements)

References 27 publications

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“…Most of the analyzed populations display modal number with 29 or 30 repeats; instead, alleles of 30, 32, and 34 repeats were more frequently observed among the Mexican mestizos. To validate these unexpected results, eight randomly taken samples were sequenced (five included in Rosales-Reynoso et al, 2005); with an exception in which there was one repeat different, all the analyzed samples showed identical number of triplets, suggesting that results from PCR on modified DNA are safe and reliable.…”

Section: Discussionmentioning

confidence: 91%

“…Although several explanations could be proposed in relation to these unusual allelic patterns, an attractive hypothesis seem to be the existence of alleles with different number of repeats among the native ethnic groups that gave rise to the modern Mexican mestizo population (Rosales-Reynoso et al, 2005). With this premise, we decided to study the repeat patterns in some Mexican Amerindian populations.…”

Section: Discussionmentioning

confidence: 99%

“…Significantly, a modal distribution of alleles with 30, 32, and 34 repeats was observed (Rosales-Reynoso et al, 2005). In addition, a tendency for larger alleles was remarkable in this population (Díaz-Gallardo et al, 1995;Rosales-Reynoso et al, 2005).…”

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confidence: 90%

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Genetic variation of the FMR1 gene among four Mexican populations: Mestizo, Huichol, Purepecha, and Tarahumara

Barros‐Núñez

Rosales-Reynoso

Sandoval

et al. 2008

American J Hum Biol

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Fragile X syndrome is the most common cause of inherited mental retardation; it is caused by expansion of CGG repeats in the first exon of the FMR1 gene. The number of CGG repeats varies between 6 and 50 triplets in normal individuals; the most common alleles have 29 or 30 repeats. Allelic patterns in the global populations are similar; however; some reports show statistical differences among several populations. In Mexico, except by a single report on a western Mestizo population, the allelic frequencies of the FMR1 gene are unknown. In this study, we analyze 207, 140, 138, and 40 chromosomes from Mestizos, Tarahumaras, Huichols, and Purepechas respectively. After PCR amplification on DNA modified by sodium bisulfite treatment, molecular analysis of the FMR1 gene showed 30 different alleles among the 525 chromosomes evaluated. Trinucleotide repeat number in the different Mexican populations varied from 15 to 87, with modal numbers of 32 and 30 in Mestizos and Tarahumaras, 29 and 32 in Purepechas and 30 among Huichols. Together, these allelic patterns differ significantly from those reported for Caucasian, Chinese, African, Indonesian, Brazilian, and Chilean populations. The increased number of the unusual allele of 32 repeats observed in the Mexican mestizo population can be explained from its frequency in at least two Mexican native populations.

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

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Genetic variation of the FMR1 gene among four Mexican populations: Mestizo, Huichol, Purepecha, and Tarahumara

Barros‐Núñez

Rosales-Reynoso

Sandoval

et al. 2008

American J Hum Biol

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“…Similarly in other world populations, 30 and 29 repeats were the most common in Caucasians (Malmgren et al , 1994a, Haataja et al , 1994, Kunst et al , 1996, Chiurazzi et al , 1996b), South Americans comprising Brazilians with varied ancestry (Mingroni-Netto et al , 2002), Chilean populations (Jara et al , 1998), several Asian populations including Chinese, Malays (Zhou et al , 2006) and Taiwanese (Chiu et al , 2008). However, this pattern is not always the case: in a Japanese sample, 27 repeat alleles were the most common (Otsuka et al , 2009) and in a Mexican sample, 32 repeats were the most common (Rosales-Reynoso et al , 2005), However these populations also contained the 30 and 29 peaks in lower frequencies. Thus, although it is likely that the 29 or 30 repeat allele is the ancestral allele, founder effects due geographic and cultural isolation or complex interactions of populations have altered the frequency distributions (Eichler & Nelson, 1996b).…”

Section: Discussionmentioning

confidence: 91%

Genetic Diversity of the Fragile X Syndrome Gene (FMR1) in a Large Sub‐Saharan West African Population

Peprah

Allen

Williams

et al. 2010

Annals of Human Genetics

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Fragile X-associated disorders (FAD) are caused by the expansion of a CGG trinucleotide repeat found in the 5′ untranslated region of the X-linked FMR1 gene. Although examinations of characteristics associated with repeat instability and expansion of the CGG repeat upon transmission from parent to offspring has occurred in various world populations, none has been conducted in large Sub-Saharan African populations. We have examined the FMR1 CGG repeat structure in a sample of general population males drawn from Ghana. We found that Ghanaians and African Americans have similar allele frequency distributions of CGG repeat and its flanking STR markers, DXS548 and FRAXAC1. However, the distribution of the more complex marker, FRAXAC2, is significantly different. The haplotype structure of the FMR1 locus indicated that Ghanaians share several haplotypes with African Americans and Caucasians that are associated with the expanded full mutation. In Ghanaians, the majority of repeat structures contained two AGG interruptions, however, the majority of intermediate alleles (35-49) lacked AGG interruptions. Overall, we demonstrate that allelic diversity of the FMR1 locus among Ghanaians is comparable to African Americans, but includes a minority of CGG array structures not found in other populations.

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“…Therefore, 1 in 353 women carried a premutation repeat. The observed premutation allele frequency (0.14%) in Tamil Nadu is lower compared with Mexican (1.7%), Brazilian (1.0%), Israeli (0.67%), Basque (0.63%), Indonesian (0.38%), and American Caucasian (0.24%) populations (Brown et al, 1996;Sucharov et al, 1999;Faradz et al, 2000;Toledano-Alhadef et al, 2001;Penagarikano et al, 2004;Rosales-Reynoso et al, 2005). No premutation alleles were reported among Chinese, Africans, Eskimo, and Mixtec (Chiurazzi et al, 1996;Kunst et al, 1996;Larsen et al, 1999;Poon et al, 2000) populations.…”

Section: Premutation Carrier Frequencymentioning

confidence: 97%

Fragile X CGG Repeat Variation in Tamil Nadu, South India: A Comparison of Radioactive and Methylation-Specific Polymerase Chain Reaction in CGG Repeat Sizing

Nagarathinam

Singh²,

Chong³

et al. 2012

Genetic Testing and Molecular Biomarkers

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Fragile X syndrome is the most frequent hereditary cause of mental retardation after Down syndrome. Expansion of CGG repeats in the 5¢ UTR of the fragile X mental retardation gene 1 (FMR1) causes gene inactivation in most of the cases. The FMR1 gene is classified into normal 5-44; gray zone 45-54; premutation 55 to < 200; and full mutation ‡ 200 repeats. Precise sizing of FMR1 alleles is important to understand their variation, predisposition, and for genetic counseling. Meta-analysis reveals prevalence of premutation carriers as 1 in 259. No such reports are available in India. About 705 women from Tamil Nadu, South India, were screened for the FMR1 allelic variation by using radioactive polymerase chain reaction-polyacrylamide gel electrophoresis (PAGE) analysis. The women who were homozygous by radioactive polymerase chain reaction (rPCR) were reanalyzed by methylation-specific polymerase chain reaction (Ms-PCR) and GeneScan analysis. The techniques were validated and compared to arrive at a correction factor. Among 122 genotypes, 35 repeat variants ranging in size from 16 to 57 were observed. The most common repeat is 30 followed by 29. One in 353 women carried the premutation. No full mutations were observed. Screening populations with low frequency of premutations may not be applicable. Ms-PCR is more suitable for routine screening and clinical testing compared with rPCR-PAGE analysis.

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Genetic Diversity at the FMR1 Locus in Mexican Population

Cited by 11 publications

References 27 publications

Genetic variation of the FMR1 gene among four Mexican populations: Mestizo, Huichol, Purepecha, and Tarahumara

Genetic variation of the FMR1 gene among four Mexican populations: Mestizo, Huichol, Purepecha, and Tarahumara

Genetic Diversity of the Fragile X Syndrome Gene (FMR1) in a Large Sub‐Saharan West African Population

Fragile X CGG Repeat Variation in Tamil Nadu, South India: A Comparison of Radioactive and Methylation-Specific Polymerase Chain Reaction in CGG Repeat Sizing

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