Comprehensive analysis of the FMR1 locus transcriptional landscape

描述(由申请人提供)：脆性X综合征(FXS)是最常见的遗传性智力低下形式(Oostra，1996)。这是由于FMR1基因5‘非编码区的CGG扩增导致脆性X智力低下蛋白(FMRP)缺失。然而，对脆性X患者的纵向临床观察表明，FXS的认知、行为和形态症状的严重程度具有高度的可变性。因此，我们寻找了FMR1基因表达的新的功能转录本，并鉴定了FMR4，一种具有很强的生物学(抗凋亡)活性的长非编码RNA。另一个小组发现了第二个来自FMR1基因座的非编码转录本ASFMR1，但尚不清楚它是否具有任何生物活性。有趣的是，FMR4和ASFMR1，类似于FMR1，在脆性X患者中都是沉默的，在突变前携带者中上调。表达分析表明，FMR4和ASFMR1在人类成体和胚胎组织中广泛表达。原位杂交研究表明，FMR4定位于细胞核，提示FMR4发挥核作用方式。由于FMR4具有显著的生物学活性，并且在FXS中被沉默，因此FMR4是参与FXS及其相关疾病的一个新的候选基因。FMR4、ASFMR1和尚未鉴定的FMR1来源的非编码RNA的活性是否与FMR1在FXS中的表达和沉默有关尚不清楚。以前已经证明，非编码RNA可以作为染色质修饰复合体的界面，而短的非编码RNA，如microRNAs，可以通过与哺乳动物细胞中启动子相关的RNA相互作用来引导表观遗传修饰，从而诱导或抑制基因的转录。因此，探索FMR1启动子是否存在这种调控，以及是否可以操纵这种调控来恢复脆性X患者的FMR1表达，是很有意义的。 公共卫生相关性：智力低下被定义为儿童时期对基本运动和语言技能的持续缓慢学习，以及成年后明显低于正常的智力能力。近613,000名6至21岁的美国儿童患有不同程度的智力障碍，需要在学校接受特殊教育(美国教育部向国会提交的第24份年度报告，2002年)。脆性X综合征是导致智力低下的主要遗传原因；它影响着1/4000男孩和1/6000女孩。我们的初步研究(发现了一种在脆性X综合征中沉默的新基因)和这项应用的拟议目标将为理解脆性X综合征和一般的心理健康提供重要的一步。这个新的转录本(FMR4)和FMR1基因上的其他潜在转录本可能与脆性X综合征和/或相关疾病具有临床相关性。

DESCRIPTION (provided by applicant): Fragile X syndrome (FXS) is the most common form of inherited mental retardation (Oostra, 1996). It is caused by a CGG expansion in the 5' UTR of FMR1, which leads to the absence of the fragile X mental retardation protein (FMRP). However, longitudinal clinical observations of fragile X patients have shown that the severity of the cognitive, behavioral and morphological symptoms of FXS is highly variable. Therefore we searched for novel functional transcripts expressed from the FMR1 locus and identified FMR4, a long non-coding RNA with a strong biological (anti-apoptotic) activity. Another group identified a second long non-coding transcript originating from the FMR1 locus, ASFMR1, but it is yet unclear if it has any biological activity. Interestingly, both FMR4 and ASFMR1, similar to FMR1, are silenced in fragile X patients and up-regulated in pre-mutation carriers. Expression analyses have shown that FMR4 and ASFMR1 are expressed in a wide range of human adult and embryonic tissues. In situ hybridization studies demonstrated that FMR4 is localized to the nucleus suggesting that FMR4 exerts a nuclear mode of action. Since FMR4 has pronounced biological activity and is silenced in FXS, FMR4 is a new candidate gene for involvement in FXS and related disorders. It is unresolved if the activity of FMR4, ASFMR1, and yet uncharacterized FMR1-derived non-coding RNAs is linked to expression and silencing of FMR1 in FXS. It has been previously demonstrated that non-coding RNAs can serve as an interface for chromatin- modifying complexes and that short non-coding RNAs, e.g. microRNAs, can induce or repress the transcription of genes by directing epigenetic modifications via interaction with promoter-associated RNAs in mammalian cells. It is therefore of interest to explore whether such regulation exists at the FMR1 promoter and whether such regulation can be manipulated to restore FMR1 expression in fragile X patients. PUBLIC HEALTH RELEVANCE: Mental retardation is defined as a persistent slow learning of basic motor and language skills during childhood, and a significantly below-normal intellectual capacity as an adult. Nearly 613,000 American children ages 6 to 21 have some level of mental retardation and need special education in school (Twenty-fourth Annual Report to Congress, U.S. Department of Education, 2002). Fragile X syndrome is the leading genetic cause of mental retardation; it affects 1/4,000 boys and 1/6,000 girls. Our preliminary studies (discovery of a new gene that is silenced in fragile X syndrome) and the proposed aims of this application will provide a significant step toward the understanding of fragile X syndrome and mental health in general. This new transcript (FMR4) and other potential transcripts in the FMR1 locus may have clinical relevance to fragile X syndrome and/or related disorders.