Fmr1 exon 14 skipping in late embryonic development of the rat forebrain.

The forebrain in the third embryonic week of the rat development is a period with significant skipping of Fmr1 exon 14. This alternative splicing event chronologically precedes a reduction of total Fmr1 mRNA, suggesting that it may be part of combinatorial mechanisms downregulating the gene's expression in the late embryonic period. The decay of FMR1 mRNA without exon 14 should be mediated by a pathway different from NMD. Finally, we provide evidence of FMR1 mRNA stabilization by UPF1, likely depending on FMRP.