Frequency of the fragile X syndrome in Chinese mentally retarded populations is similar to that in Caucasians

Abstract

Fragile X syndrome is recognized as the most common inherited cause of mental retardation in western countries. The prevalence of the fragile X syndrome in Asian populations is uncertain. We report a multi-institutional collaborative study of molecular screening for the fragile X syndrome from 1,127 Chinese mentally retarded (MR) individuals. We found that 2.8% of the Chinese MR population screened by DNA analysis had the fragile X full mutation. Our screening indicated that the fragile X syndrome prevalence was very close to that of Caucasian subjects. In addition, we found that 62.5% of fragile X chromosomes had a single haplotype for DXS548-FRAXAC1 (21-18 repeats) which was present in only 9.7% of controls. This unique distribution of microsatellite markers flanking the FMR1 CGG repeats suggests that the fragile X syndrome in Chinese populations, as in the Caucasian, may also be derived from founder chromosomes.

FMR1 haplotype analyses among Indians: a weak founder effect and other findings

“…(3) With exception of the Pacific Asian populations of Japan, China and Thailand (Richards et al 1994;Zhong et al 1999;Limprasert et al 2001), all the other reported ethnic groups, including ours, show FRAXAC1-3 to be the modal allele among control X chromosomes Macpherson et al 1994;Bonaventure et al 1998;Crawford et al 2000). Our population reveals a high prevalence of the FRAXAC1-3 allele among the fragile X cohort also, a finding similar to that seen among the Finns and the Danes (Zhong et al 1996;Larsen et al 2000).…”

“…However, the majority of these studies have been limited to the Western (White) Caucasian ethnic groups derived primarily from North America, Europe and Australia. These studies have concluded that a few founder mutations are responsible for a majority of the extant fragile X pedigrees and the present day fragile X chromosomes are thus lineage descendants of these original founder mutational events (Richards et al , 1994Zhong et al 1999). These studies have concluded that a few founder mutations are responsible for a majority of the extant fragile X pedigrees and the present day fragile X chromosomes are thus lineage descendants of these original founder mutational events (Richards et al , 1994Zhong et al 1999).…”

“…Allele frequency distributions at these polymorphic loci have been investigated among control and fragile X chromosomes from diverse ethnic populations worldwide (Haataja et al 1994;Macpherson et al 1994;Richards et al 1994;Syrrou et al 1996;Bonaventure et al 1998;Zhong et al 1999;Crawford et al 2000). However, the majority of these studies have been limited to the Western (White) Caucasian ethnic groups derived primarily from North America, Europe and Australia.…”

Fragile X Syndrome: Prevalence, Treatment, and Prevention in China

“…Zhong et al (11) performed a multi-institutional collaborative study utilizing molecular screening for FXS among 1,127 Chinese patients diagnosed with ID; 2.8% of patients with ID were screened for the full mutation based on the DNA analysis. The prevalence of FXS in China is equivalent to the prevalence among Caucasians, which ranges from 2.6 to 8.7% among individuals with ID.…”

A Japanese Case of Fragile-X-Associated Tremor/ataxia Syndrome (FXTAS)

“…Fragile X syndrome occurs when the number of CGG repeats at 5'UTR of the FMR1 gene exceed 200 (full mutation), which triggers methylation in the promoter region (15) and the subsequent silencing of the FMR1 gene, resulting in failure to produce the translational product FMR protein (16 (22,23 …”