HNRNPU在神经发育障碍发生中的分子机制研究

Neurodevelopmental disorders are one of the key threats to child health. Continuous genome-wide association studies (GWAS) found HNRNPU gene mutation is highly associated with neurodevelopmental disorders, however, the molecular mechanism is largely unknown. HNRNPU was characterized as a component of heterogeneous nuclear ribonucleoprotein (RNP) particles or as a nuclear scaffold attachment factor A (SAF-A). HNRNPU has been implicated in diverse pathways, including transcription regulation and non-coding RNA localization. Our preliminary data indicated HNRNPU preferentially associates with genes in the function of nervous system development on chromatin. We hypothesize that the regulation of neurodevelopmental gene expression by HNRNPU may be the mechanism of neurodevelopmental disorders. Additionally, our early investigation on the RNA interactome of HNRNPU found that HNRNPU directly binds diverse classes of non-coding RNAs. Mechanistically, we hypothesize that HNRNPU may build an interaction network between non-coding RNAs and chromatin and maintain the gene expression for neurodevelopment. Based on this hypothesis, we will study the function of HNRNPU in neurodevelopmental gene expression, and employ new techniques, GRID-seq (capture in situ Global RNA Interaction with DNA by deep sequencing) and GRO-seq (Global nuclear Run-On sequencing) to investigate HNRNPU-mediated global interaction network between non-coding RNAs and neurodevelopmental genes as well as the mechanism of gene expression regulation. The results obtained may give us new insights into the molecular mechanism of neurodevelopmental disorders and provide theoretical basis for the diagnosis and therapeutics of the disease.

神经发育障碍威胁儿童健康。研究发现，神经发育障碍与HNRNPU基因突变高度关联，但分子机制还知之甚少。HNRNPU是核不均一核糖核蛋白成员之一或核基质蛋白A，参与了转录和非编码RNA定位等多个方面的调控。我们初步研究发现，在染色质上HNRNPU选择性结合神经系统发育相关基因。我们认为，HNRNPU调控该类基因表达可能是其在神经发育障碍发生中的分子机制。我们前期的研究发现，HNRNPU广泛结合各种非编码RNA。我们推测，HNRNPU可能通过构建非编码RNA与染色质互作网络来维持神经系统发育相关基因的正常表达。根据该假说，本项目将调查HNRNPU对神经系统发育相关基因的表达调控功能，并运用新技术GRID-seq和GRO-seq，系统研究HNRNPU介导的非编码RNA与神经系统发育相关基因的互作网络和基因表达调控机制。项目研究结果可为神经发育障碍发生提供分子机理，并为其诊疗提供必要的理论依据。

HNRNPU基因与神经发育障碍高度关联。鉴于HNRNPU为核不均一核糖核蛋白成员之一或核基质蛋白A，我们想从转录、染色质结构和非编码RNA-染色质互作网络调控等方面研究其功能以及在神经发育中的作用。通过优化ChIP-seq技术，我们在基因组中鉴定到了HNRNPU近11万个高可信度的结合位点，它们广泛分布于基因启动子和外显子等区域，结合的基因在功能上富集于神经发育相关基因；此外，HNRNPU高度富集于染色质拓扑结构域的边界处，但仅有少量结合位点与绝缘因子CTCF结合位点重合；在功能上，我们通过GRO-seq和Hi-C技术发现，HNRNPU不仅抑制Pol II的暂停释放，还介导染色质远距离相互作用，并在三维基因组构建中显示出独立于CTCF的作用；同时，这些结果还提示HNRNPU介导的转录调控以及三维基因组结构可能有助于神经发育相关基因表达。此外，我们在以上工作的启发下，大胆地拓展了该项目，运用ChIP-seq大规模地探索了RNA结合蛋白与染色质的相互作用，意外地发现RNA结合蛋白与染色质结合的广谱性，以及直接参与转录调控的新规律，并以RBM25为例，研究了其在转录因子YY1的染色质结合，以及其介导的转录和启动子-增强子互作等方面的调控作用。