Elevated FMR1 mRNA in premutation carriers is due to increased transcription

Relative FMR1 mRNA and transcript levels in premutation versus normal lymphoblastoid cell lines. (A) Analysis of spliced message using primers located in exons 3 and 4, with the probe spanning the intron/exon junction. (B) Analysis of pre- or partially spliced transcripts using primers located in introns 2 and 3 (MM₁) or in exon 3 and intron 4 (MM₂). GM, hypermethylated, full mutation allele (∼600 CGG repeats); AG, normal allele (female; 16, 29 CGG repeats); MM, large premutation allele (160 CGG repeats). Error bars reflect measurements performed in triplicate.