Abstract
Fragile X syndrome is a genetic disorder caused by abnormal function of the FMR-1 gene. The majority of fragile X syndrome patients carry an expansion of the CGG tri-nucleotide repeat in the FMR-1 gene, whereas others have a deletion or a point mutation in the FMR-1 structural gene. In this report, we analyzed a typical family with three male patients. RNA from Epstein-Barr virus transformed lymphoblastoid cells was used for RNase protection assay and reverse transcription-polymerase chain reaction (RT-PCR) analysis. Five normal individuals and one asymptomatic heterozygote from this family expressed detectable FMR-1 transcripts, whereas three fragile X patients showed no sign of expression with either assay. To extend the application of this PCR-based assay to laboratory diagnosis of fragile X syndrome, we confirmed that dried blood samples collected on screening filter papers for newborns are an adequate source of RNA for RTPCR. Moreover, fragile X patients from the study family and another family were reliably identified by the absence of the FMR-1-specific PCR product from the dried blood specimens. Our studies indicate that this simple assay can be used to diagnose the fragile X syndrome for the majority of male patients.
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Pai, JT., Tsai, SF., Horng, CJ. et al. Absence of FMR-1 gene expression can be detected with RNA extracted from dried blood specimens. Hum Genet 93, 488–493 (1994). https://doi.org/10.1007/BF00202810
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DOI: https://doi.org/10.1007/BF00202810