Haplotype analysis at the FRAXA locus in an Indian population

Abstract

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.

DXS998–DXS548–FRAXAC1 represents a novel informative haplotype at the FMR1 locus in the Iranian population

“…The frequency distribution of the DXS548 alleles was compared with the data from other populations (Chakraborty et al, 2008;Daneberga et al, 2011;Đokic et al, 2008;Drozd et al, 2003b;Felix-López et al, 2006;Haataja et al, 1994;Larsen et al, 2001;Malmgren et al, 1993;Mingroni-Netto et al, 2002;Oudet et al, 1993;Pekarik et al, 1999). Allele 40 at the DXS548 locus was the most common allele (0.69) in the Iranian population which was similar (with slightly different frequencies) to those have been reported from Latvia, Russia, Sweden, Finland, France, Norway, Croatia, Mexico, Brazil, India and Czech Republic.…”

“…There is no information on this allele from other populations: The 40 bp allele was the most common allele in India (Chakraborty et al, 2008), Norway (Larsen et al, 2001), Czech Republic (Pekarik et al, 1999) and Croatia (Đokic et al, 2008). The observed heterozygosity for these three markers was less than most of the populations, which could indicate that the genetic differentiation to some extent is influenced by inbreeding in the Iranian population (Papiha et al, 1992).…”

Nucleosomal occupancy and CGG repeat expansion: a comparative analysis of triplet repeat region from mouse and human fragile X mental retardation gene 1

“…In the context of CGG instability and fragile X syndrome, differential frequency of polymorphic alleles of microsatellite markers FRAXAC1 and FRAXAC2 and DX548 linked to FRAXA locus is reported in fragile X patients (Richards et al 1991;Oudet et al 1993;Chakraborty et al 2008). These markers have been used to trace the founder effect in fragile X syndrome, indirectly implying that the frequency of repeat instability is higher in specific allelic background.…”

Populationsgenetik des humanen X-Chromosoms

“…So war z. B. in einer ostindischen Population eine Gründermutation erkennbar [1], in Thailand aber nicht [10].…”