Background: Fragile X syndrome (FXS) is the most common inherited form of mental retardation, affecting approximately 1 in 1250 males and 1 in 2500 females, with estimated premutation carriers of 1/600 in males and 1/300 in females. It is resulted from an unstable expansion of triplet CGG repeats at promoter region of the FMR1 gene, which consequently silences FMR1 gene expression. Our earlier study has determined that FXS accounts for 3.2% of the Chinese mental retarded population. Recently, FMR1 mutation has been found in autism patients. In this report, we present a pilot study of molecular screening of FMR1 mutation in a subset of Chinese autism patients.

Methods: A total of 235 DNA samples, including 185 samples from autism patients (174 males and 11 females) and 50 samples from mental retardation (MR) patients (36 males and 14 females), which had been banked earlier, were included. PCR based approach was employed for analyzing CGG repeat size. PCR products were detected on 6% denaturated PAGE electrophoresis and detected with silver staining.

Results: Among 235 samples screened, 226 (49 MR and 177 autism) samples showed normal patterns. No normal pattern could be detected among the remaining 9 samples including 1 MR and 8 autism cases.

Conclusions: We have developed a simple, easy, rapid and economical PCR-based molecular screening approach for detecting FMR1 CGG repeats. Using this approach, we have detected 9 subjects from our previously banked MR and autism DNA samples. We suggest the use of this approach in clinical practice for screening FXS high-risk population among pregnant women and MR children whose genetic etiology is yet unknown.

Key words: fragile X syndrome; FMR1; autism; Chinese; molecular screening

World J Pediatr 2006;4:285-287