Absence of FMR-1 gene expression can be detected with RNA extracted from dried blood specimens.
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 RT-PCR. 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.
Pai
J T
JT
Institute of Genetics, National Yang-Ming Medical College, Taipei, Taiwan, ROC.
Tsai
S F
SF
Horng
C J
CJ
Chiu
P C
PC
Cheng
M Y
MY
Hsiao
K J
KJ
Wuu
K D
KD
D001483:Base Sequence; D001793:Blood Preservation; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D017931:DNA Primers / Q000737:chemistry / Q000235:genetics; D005260:Female; D051860:Fragile X Messenger Ribonucleoprotein 1; D005600:Fragile X Syndrome / Q000097:blood* / Q000235:genetics*; D017353:Gene Deletion; D015870:Gene Expression; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics*; D010375:Pedigree; D016133:Polymerase Chain Reaction; D012313:RNA / Q000097:blood* / Q000302:isolation & purification; D016601:RNA-Binding Proteins / Q000235:genetics*
D017931:DNA Primers; D051860:Fragile X Messenger Ribonucleoprotein 1; D009419:Nerve Tissue Proteins; D012313:RNA; D016601:RNA-Binding Proteins; C497683:FMR1 protein, human