Fragile X syndrome in Calcutta, India

Saha, Sharmila; Karmakar, Parimal; Chatterjee, Chandrahas; Banerjee, Dalia; Das, Shyamal Kumar; Dasgupta, Uma B.

doi:10.1258/0004563011900498

Cited by 10 publications

(6 citation statements)

References 29 publications

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“…All samples were ascertained from the Canadian population, which is predominantly Caucasian with Asians as the main minority population; therefore, population stratification may exist in the patient and control groups. Although some groups have reported an increase specifically in alleles of 36 repeats in Chinese (Tzeng et al 1999;Pang et al 1999), this is not common to all Asian populations (Saha et al 2001;Sharma et al 2001), and alleles of 36 repeats are not substantially increased in our patient population compared with our controls.…”

Section: Samplescontrasting

confidence: 67%

FMR1 repeat sizes in the gray zone and high end of the normal range are associated with premature ovarian failure

2005

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Premature ovarian failure (POF) is the occurrence of menopause before the age of 40 and affects 1% of the female population. Whereas the etiology of POF is largely unexplained, FMR1 premutation carriers are known to be at increased risk of POF compared with the general population. The FMR1 premutation alleles have 55-200 copies of a CGG repeat in the 5' untranslated region of the FMR1 gene. However, functional effects on gene expression may occur even for repeat sizes in what has been considered the "normal" range. To evaluate the role of the FMR1 repeat in POF, repeat sizes were examined in 53 women with idiopathic POF, 161 control women from the general population, and 21 women with proven fertility at an advanced maternal age. A significant increase in the number of FMR1 alleles between and including 35 and 54 CGG repeats was found in the POF patient population; 15 of 106 (14.2%) POF alleles were between and including 35 and 54 repeats, whereas only 21 of 322 (6.5%) alleles in the general population (P=0.02) and 2 of 42 (4.8%) alleles from women with proven late fertility (P=0.09) were of this size (P=0.01 versus combined controls). The effect was also significant for comparisons of genotype repeat size (repeat size weighted by the relative activity of the two FMR1 alleles) and biallelic mean (average size of the two alleles). These results are clinically relevant and suggest that the FMR1 gene plays a more significant role in the incidence of POF than has previously been thought.

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Section: Samplescontrasting

confidence: 67%

FMR1 repeat sizes in the gray zone and high end of the normal range are associated with premature ovarian failure

2005

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“…Both kinds of alleles are meiotically unstable and mosaicism in individuals suggests mitotic instability as well. Extensive polymorphism of the CGG repeat has been observed in the normal individuals, varying from 6 to 54 in the Caucasians [Fu et al, 1991] and 8 to 50 in the Indian population [Baskaran et al, 1998; Saha et al, 2001; Sharma et al, 2001]. Reports on this disorder from the Indian population, employing DNA diagnostics method revealed a frequency of 7–8% from the various parts of the country [Baskaran et al, 1998; Saha et al, 2001; Sharma et al, 2001].…”

Section: Introductionmentioning

confidence: 99%

Haplotype analysis at the FRAXA locus in an Indian population

Chakraborty

Mondal

Das

et al. 2008

American J of Med Genetics Pt A

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The FRAXA locus is flanked by three polymorphic STR markers DXS548, FRAXAC1, and FRAXAC2. Allele frequencies of these markers were determined on a population representing the eastern part of India comprising of 69 normal controls and 69 unrelated subjects with mental retardation, among whom 21 were fragile X patients. These frequencies were compared with published data on other Indian population and the major populations of the world. The allele and haplotype distribution of the studied population were significantly different in some respects from the major populations of the world. The increase of heterozygosities in fragile X samples (DXS548 67.5%, FRAXAC1 63.5%, FRAXAC2 68.5%) relative to the controls (DXS548 63.3%, FRAXAC1 51.0%, FRAXAC2 67.2%) suggests a multimodal distribution of fragile X associated alleles. Haplotype analyses with DXS548 and FRAXAC1 markers revealed that haplotype distribution in the normal controls and fragile X groups were significantly different, suggesting a weak founder effect.

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“…The allele with 29 CGG repeats is also the most frequent allele in the Asian populations (Cheng et al, 1997), although other studies suggest the allele with 28 CGG repeats to be the most common allele in China (Chiang et al, 1999). The 29 CGG allele is also the most frequently reported in India (Saha et al, 2001). Since our study was performed on a population with mental retardation of unknown etiology, it could be argued that this could lead to a bias in the ascertainment of X chromosomes.…”

Section: Resultsmentioning

confidence: 96%

“…The CGG repeats are polymorphic, their mode of distribution varying according to the population studied (Brown et al, 1996;Chiurazzi et al, 1996b;Tzeng et al, 1999;Chiang et al, 1999;Saha et al, 2001). Similar to several other diseases involving dynamic mutations, there is evidence of a founder effect based on the demonstration of linkage disequilibrium between the fragile X locus and its flanking polymorphic markers (Richards et al, 1992;Buyle et al, 1993;Oudet et al, 1993;Macpherson et al, 1994;Zhong et al, 1994a;Zhong et al, 1994b;Chiurazzi et al, 1996c;Syrrou et al, 1996;Jara et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

Fragile X founder effect and distribution of CGG repeats among the mentally retarded population of Andalusia, South Spain

et al. 2002

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Fragile X syndrome is the most common inherited form of mental retardation. We investigated the prevalence of the Fragile X syndrome in the population with mental retardation of unknown etiology in Andalusia, South Spain. We analyzed 322 unrelated patients (280 males and 42 females), and found a fragile X syndrome frequency of 6.5%. Among the non-fragile X chromosomes, the 29 CGG repeat was the most common allele. At the linked microsatellite DXS548 locus, we found a new allele which we called "allele 10" (17 CA). Similar to other south European populations, allele 2 (25 CA) at the DXS548 locus and the fragile X allele were in linkage disequilibrium supporting the idea of a common founder chromosome predisposing to the CGG expansion.

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Fragile X syndrome in Calcutta, India

Cited by 10 publications

References 29 publications

FMR1 repeat sizes in the gray zone and high end of the normal range are associated with premature ovarian failure

FMR1 repeat sizes in the gray zone and high end of the normal range are associated with premature ovarian failure

Haplotype analysis at the FRAXA locus in an Indian population

Fragile X founder effect and distribution of CGG repeats among the mentally retarded population of Andalusia, South Spain

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