Xie Wen, Dolzhanskaya Natalia, LaFauci Giuseppe, Dobkin Carl, Denman Robert B
New York State Institute for Basic Research in Developmental Disabilities, Department of Molecular Biology, 1050 Forest Hill Road, Staten Island, NY 10314, USA.
Neurobiol Dis. 2009 Jul;35(1):52-62. doi: 10.1016/j.nbd.2009.03.015. Epub 2009 Apr 9.
The pre-mRNA of the fragile X mental retardation 1 gene (FMR1) is subject to exon skipping and alternative splice site selection, which can generate up to 12 isoforms. The expression and function of these variants in vivo has not yet been fully explored. In the present study, we investigated the distribution of Fmr1 exon 12 and exon 15 isoforms. Exon 12 encodes an extension of KH(2) domain, one of the RNA binding domains in the FMR1 gene product (FMRP) and we show that exon 12 variant proteins differentially interact with kissing complex RNA. Alternative splicing at exon 15 produces FMRPs differing in RNA binding ability and each is distinguished by unique post-translational modifications. Using semiquantitative RT-PCR and Northern blotting, we found that particular Fmr1 exon 12 and exon 15 isoforms change during neuronal differentiation. Interestingly, Fmr1 exon 12 variants display tissue-specific and developmental differences, while exon 15-containing transcripts vary less. Altogether, the spatio-temporal plasticity of FMR1 mRNA is consistent with complex RNA processing that is mis-regulated in fragile X syndrome.
脆性X智力低下1基因（FMR1）的前体mRNA会发生外显子跳跃和可变剪接位点选择，这最多可产生12种异构体。这些变体在体内的表达和功能尚未得到充分研究。在本研究中，我们调查了Fmr1外显子12和外显子15异构体的分布。外显子12编码KH(2)结构域的延伸，KH(2)结构域是FMR1基因产物（FMRP）中的RNA结合结构域之一，我们发现外显子12变体蛋白与吻状复合体RNA有不同的相互作用。外显子15处的可变剪接产生了RNA结合能力不同的FMRP，每个FMRP都有独特的翻译后修饰。通过半定量RT-PCR和Northern印迹法，我们发现特定的Fmr1外显子12和外显子15异构体在神经元分化过程中会发生变化。有趣的是，Fmr1外显子12变体表现出组织特异性和发育差异，而含外显子15的转录本变化较小。总之，FMR1 mRNA的时空可塑性与脆性X综合征中失调的复杂RNA加工过程一致。
