BRPF1基因在儿童智力障碍发生中的分子机制

The prevalence of intellectual disability in children or adolescents is about 2%. Intellectual disability is not only a heavy burden on individuals and families, but also brings a series of problems to society and education. Most intellectual disabilities are caused by genetic factors. So far, hundreds of genes have been associated with intellectual disability. Within them, epigenetic regulators are one of the most important categories. Bromodomain and PHD Finger-containing protein 1 (BRPF1) is a scaffold protein and an activator of the three acetyltransferase KAT6A / KAT6B / KAT7 complexes. Two recent reports published in the American Journal of Human Genetics found 16 cases of BRPF1 heterozygous mutations leading to intellectual disability in children. Our published work explained the molecular mechanisms of some symptoms such as growth retardation, white matter abnormality and spinal fusion. To further understand the neurobiological basis of intellectual disability caused by BRPF1 mutations, this proposal is based on the Brpf1 transgenic mouse models. Firstly, effect of haploinsufficiency of Brpf1 gene on the occurrence of intellectual disability will be studied. Secondly, molecular and regulatory mechanisms of Brpf1 gene on the morphology and function of GABAergic interneurons and hippocampal CA1 pyramidal neurons will be explored. Through this project we can better understand the molecular mechanisms of acetylation activator BRPF1 on regulation of intelligence development, and establish intellectual disability mouse models mimicking BRPF1 mutations in human for further drug screening and development.

智力障碍在儿童或青少年中的患病率达2%。不仅造成患者个人和家庭的沉重负担，也给社会和教育带来一系列问题。大多数的智力障碍由遗传因素造成。至今发现的数百个智力障碍相关基因中，表观遗传调控剂是其中重要的一类。溴结构域和PHD锌指蛋白1（BRPF1）是三个乙酰化酶KAT6A/KAT6B/KAT7复合物的支架蛋白和激活剂。近期两篇报道发现16例BRPF1杂合突变导致儿童智力障碍。我们已发表的工作解释了患者出现生长发育迟缓、白质异常和脊椎融合等症状的分子机制。为了理解BRPF1突变造成智力障碍的神经生物学基础，本课题使用Brpf1转基因小鼠模型，研究该基因单倍剂量不足对智力障碍发生的影响；探索该基因调控GABA能中间神经元和海马CA1锥体神经元形态和功能的分子机制。预期通过本课题的研究更好地理解BRPF1这一类乙酰化激活剂调控智力发育的分子机制，建立BRPF1智力障碍小鼠模型用于后期药物筛选和开发。

智障影响2%儿童并致学习认知功能异常。作为表观调控剂，BRPF1突变患者常呈现智障和发育迟缓。我们前期发现Brpf1基因在胚胎、前脑发育和造血干细胞的关键作用，部分解释了该基因突变患者发育迟缓、白质异常和脊椎融合的分子机制。为了更深入理解其突变造成智障的神经生物学基础，本课题采用体外神经元培养结合转基因小鼠模型，分别研究该基因调控GABA能中间神经元和海马CA1锥体神经元形态和功能的分子机制。首先，通过AAV-shBrpf1感染内侧神经节隆起来源GABA能中间神经元，结合免疫荧光染色、全细胞膜片钳、MGE移植和mRNA-Seq，探究对神经元分化、树突形态、电生理、迁移和基因调控的影响。结果表明敲减导致GABA能神经元分化为小白蛋白神经元呈减少趋势；神经元放电阈值增加、诱发动作电位数减少、微型抑制性突触后电流振幅降低；体内迁移无变化；与神经元发育和突触传递有关基因表达失调。接着，通过AAV-shBrpf1感染围产期海马神经元和立体定位注射成年海马CA1，结合免疫荧光、全细胞膜片钳、mRNA-seq和Morris水迷宫研究对神经元形态、电生理、基因调控和空间记忆的影响。结果表明敲减致海马微型兴奋性突触后电流频率降低，CA1特异敲减后空间记忆呈受损趋势；与学习记忆和突触传递相关基因表达失调。最后，通过海马CA1锥体神经元特异敲除的Brpf1转基因小鼠模型, 结合急性脑片电生理、行为学评估 (旷场、水迷宫，条件恐惧，新事物偏好)和单细胞多组学研究对海马CA1锥体神经元电生理、转录调控和学习记忆及社交的影响。结果表明条件敲除致mEPSC频率下降；空间学习记忆，条件和声音恐惧记忆进展性受损；敲除影响其它神经元亚类甚至胶质细胞基因表达和转录调控。总之，课题深入阐释了BRPF1基因突变导致智障的神经生物学机制，海马条件性敲除模型有望作为BRPF1智障模型用于后续药物筛选开发。