BICD2基因在家族性扩张型心肌病发生中的作用研究

The pathophysiological mechanisms of dilated cardiomyopathy are still poorly understood. Recent studies indicated that gene mutation was involved in the familial dilated cardiomyopathy. Our previous results from whole exome sequencing and whole genome sequencing demonstrated that BICD2 gene mutation (c.G2429A, p.R810H) was presented in two familial dilated cardiomyopathy characterized by autosomal recessive heredity. Until now, no report is found in which dilated cardiomyopathy was induced by BICD2 gene mutation. Our preliminary research manifested abnormal cardiac fractional shortening, which is similar to human dilated cardiomyopathy, in the zebrafish embryo after bicd2 gene was knocked down. Therefore, the present project intends to investigate the role of BICD2 gene in dilated cardiomyopathy using knockdown zebrafish, mouse knockout model and anthropogenic embryonic stem cell models. Accordingly, the abnormal nuclear pore complexes and MKL-1/SRF signaling will be studied and the involved pathophysiological mechanism of familial dilated cardiomyopathy will be expected to elucidation.

扩张型心肌病（扩心病）病因未明。近年来的研究表明家族性扩心病与基因突变有关。申请人对家族性扩心病家系成员进行全外显子组/全基因组测序分析发现两个扩心病家系中存在BICD2基因突变（c.G2429A, p.R810H），表现为常染色体隐性遗传方式。目前国内外均未见该基因突变导致扩张型心肌病的报道。申请人前期研究工作表明：敲降斑马鱼bicd2基因的表达，出现心室缩短分数降低等与人类扩心病类似的特征。本项目拟利用BICD2基因敲降斑马鱼和基因敲除小鼠模型，以及人胚胎干细胞体外模型，研究BICD2基因是否通过影响核孔复合体的异常分布以及调控MKL-1/SRF信号通路导致扩心病的发生，从而确认BICD2基因突变在家族性扩心病发生中的作用与病理机制。

我们通过对临床收集到的1个近亲婚配扩心病家系进行外显子测序检测到一个常染色体隐性和进化保守的错义突变，BICD2c.2429G>A: p.Arg810His，该突变与近亲婚配扩心病家系的疾病表型共分离。我们进一步证实210个散发扩心病群体中的3扩心病患者存在BICD2突变，表明BICD2可能是扩心病致病基因。我们接下来构建了BICD2基因敲除的斑马鱼模型，并利用斑马鱼模型研究BICD2在胚胎阶段和成鱼阶段的相关功能。我们发现bicd2基因敲除会导致纯合子的部分胚胎死亡，表明bicd2在胚胎发育中有重要作用。我们利用超声心动图来检测成年斑马鱼的心室大小和功能的相关指标。我们分析发现bicd2基因敲除的斑马鱼表现出心脏扩张，射血分数、心输出量和每搏输出量下降的表型，与人类扩心病表型相一致。此外，RNA-seq证实了bicd2纯合敲除鱼有最大的转录谱改变。bicd2纯合敲除鱼的基因集富集分析结果，揭示钙离子信号通路和线粒体能量代谢通路等基因集有显著的基因上调表达。综上所述，我们首次发现并报道，常染色体隐性BICD2突变与家族性扩心病有关，有助于深入理解扩心病的分子病理机制。