EPAC基因突变对突触传递在自闭症社会行为活动中的调控作用和机理

Recently, we applied target gene technology combined with electrophysiological recording to study the effect of Epac gene mutation on the autistic neural functional activities. Epac includes Epac1 and Epac2, which is also known as guanine nucleotide exchange factor that is directly activated by cAMP. Previously, we have constructed Epac2 gene knockout mice (Epac2-/-). We found that in Epac2-/- mice, the expression of Epac1 increased. Later, we constructed Epac1 and Epac2 double knockout mice (Epac-/- mice). We found that the excitatory synaptic transmission in frontal cortex of double knockout mice weakened, accompanied by social behavioral deficits. The gene arrays found that Epac gene mutation lowered the expression of Svb2. Svb2 is an important synaptic protein which is involved in excitatory synaptic transmission. Therefore, we hypothesize that the Epac gene mutation lowers Svb2 expression, thereby weakening the excitatory synaptic transmission and leading to autistic social behavior, we will test this hypothesis in this project, thus providing a new theoretical basis and molecular target for the treatment of autism.

最近，我们应用靶基因技术结合电生理记录研究自闭症Epac基因突变对神经功能活动的影响。Epac包括Epac1和Epac2，又称为鸟苷酸交换因子，由cAMP直接激活。之前我们已经构建Epac2基因敲除小鼠 (Epac2-/-)。我们发现在Epac2-/-小鼠,Epac1的表达增多。随后又构建Epac1与Epac2双敲除鼠（Epac-/-小鼠）。我们发现双敲老鼠额叶皮层兴奋性突触传递减弱，同时伴有社交行为缺陷。基因组学分析发现Epac基因突变下调Svb2表达。Svb2是一重要突触蛋白，参与兴奋性突触传递。因此我们假设Epac基因突变下调Svb2表达，从而减弱兴奋性突触传递，并导致自闭症的社会行为障碍，本项目将阐明这一自闭症分子假说，从而，为自闭症治疗提供新的理论基础和分子靶标。

EPAC-/-小鼠大脑额叶皮层环路兴奋性突触传递出现减弱，而抑制性突触传递有一定程度增强，相关实验结果缺乏稳定性，同时，我们发现EPAC无效突变导致小鼠繁殖能力缺陷及肠道发育异常。血小板源性生长因子D（PDGF-D）在神经发育及肿瘤的发生发展中具有重要作用，其对肠道病变的作用尚需进一步研究。我们的研究表明EPAC无效突变可通过影响神经嵴细胞增殖，从而影响肠道神经系统的发育，在肠道功能中发挥重要作用。红景天苷可促进神经细胞增殖及神经干细胞分化，抑制神经细胞凋亡，从而促进神经细胞再生。PDGF-D在肠道病变组织中高表达，并与临床病理特征呈正相关。PDGF-D的下调可在体内体外抑制细胞系SW480的增殖、迁移和血管生成。而上调PDGF-D可促进HCT116细胞的恶性生物学行为。此外，PDGF-D可上调Notch1和Twist1的表达，并促进EMT转化（上皮标志Ecad下调，而间质标志Vimentin上调）。与此同时，TGF-β1可促使HCT116细胞上调Notch1和Twist1的表达，上调Notch1可逆转PDGF-D和Twist1的表达下调。另外Twist1可促进EMT和侵袭能力。综合上述结果表明PDGF-D可促进结直肠恶性病变的增殖和侵袭，下调PDGF-D可抑制Notch1/Twist1通路，从而逆转EMT进程，抑制恶性病变的发生发展。