Department of Clinical Genetics and Experimental Medicine, 900th Hospital of the Joint Logistics Force, Xiamen University School of Medicine, 156 Xi'erhuanbei Road, Fuzhou City, Fujian Province, 350025, People's Republic of China.
Present addresses: Department of Laboratory Medicine, Zhongshan Hospital, Fudan University, Shanghai, 200032, China.
BMC Genet. 2020 Jun 18;21(1):63. doi: 10.1186/s12863-020-00870-2.
The disease gene of fragile X syndrome, FMR1 gene, encodes fragile X mental retardation protein (FMRP). The alternative splicing (AS) of FMR1 can affect the structure and function of FMRP. However, the biological functions of alternatively spliced isoforms remain elusive. In a previous study, we identified a new 140bp exon from the intron 9 of human FMR1 gene. In this study, we further examined the biological functions of this new exon and its underlying signaling pathways.
qRT-PCR results showed that this novel exon is commonly expressed in the peripheral blood of normal individuals. Comparative genomics showed that sequences paralogous to the 140 bp sequence only exist in the genomes of primates. To explore the biological functions of the new transcript, we constructed recombinant eukaryotic expression vectors and lentiviral overexpression vectors. Results showed that the spliced transcript encoded a truncated protein which was expressed mainly in the cell nucleus. Additionally, several genes, including the BEX1 gene involved in mGluR-LTP or mGluR-LTD signaling pathways were significantly influenced when the truncated FMRP was overexpressed.
our work identified a new exon from amid intron 9 of human FMR1 gene with wide expression in normal healthy individuals, which emphasizes the notion that the AS of FMR1 gene is complex and may in a large part account for the multiple functions of FMRP.
脆性 X 综合征的致病基因 FMR1 基因编码脆性 X 智力低下蛋白（FMRP）。FMR1 的选择性剪接（AS）可以影响 FMRP 的结构和功能。然而，选择性剪接异构体的生物学功能仍不清楚。在之前的研究中，我们从人类 FMR1 基因的内含子 9 中鉴定出一个新的 140bp 外显子。在本研究中，我们进一步研究了这个新外显子及其潜在的信号通路的生物学功能。
qRT-PCR 结果表明，这个新外显子在正常个体的外周血中普遍表达。比较基因组学表明，与 140bp 序列相似的序列仅存在于灵长类动物的基因组中。为了探索新转录本的生物学功能，我们构建了重组真核表达载体和慢病毒过表达载体。结果表明，剪接转录本编码的截断蛋白主要表达在细胞核中。此外，当截断的 FMRP 过表达时，包括涉及 mGluR-LTP 或 mGluR-LTD 信号通路的 BEX1 基因在内的几个基因显著受到影响。
我们的工作从人类 FMR1 基因的内含子 9 中鉴定出一个新的外显子，在正常健康个体中有广泛的表达，这强调了 FMR1 基因的 AS 是复杂的，可能在很大程度上解释了 FMRP 的多种功能。
