Role of PAX3 in the conotruncal septation of the developing heart

1.给妊娠7.5天的ICR小鼠一次性注射双二胺，用半定量RT-PCR方法检测胚胎神经系统PAX3 m-RNA的表达。对照胚胎显示，PAX3在胚胎第8.5天开始在中枢神经系统表达，11.5天达到最高水平，13.5天表达减弱。结果表明：1.处理组胚胎的表达模式与对照胚胎相同，m-RNA的量在对照胚胎和处理胚胎之间没有显著差异。在用双二胺处理的小鼠胚胎中，评估了对中枢神经系统发育至关重要的转录因子的表达。与对照组相比，双二胺处理组胚胎脑中EMX-1的表达在10.5ED和11.5ED显著降低。双二胺对WNT-3和AP-2的表达无明显影响。SOX4是一个Sry-box转录因子家族，仅在胚胎心脏的流出道脊和房室管中表达。小鼠的基因突变会导致半月瓣的异常发育，导致漏斗状室间隔缺损和持续性动脉干等心脏畸形。胚胎大脑和心脏中SOX4的表达被双二胺下调。本研究显示m-RNA的表达模式表明，双二胺影响中枢神经系统的发育，从而扰乱神经脊细胞向心脏的迁移。在本研究中，PAX3在圆锥干隔中的作用尚不清楚。SOX4可能参与了神经脊细胞的迁移和向血管平滑肌细胞的分化。

1. A single dose of bis-diamine was administered to pregnant ICR mice on 7.5 days of gestation and the expression of PAX3 m-RNA in the embryonic nervous system was examined using semi-quantitative RT-PCR method. The control embryos showed PAX3 expression in the central nervous system was first detected on 8.5 embryonic day (ED), reached the maximum level on 11.5 and diminished on 13.5 ED. The treated embryos demonstrated the same expressional pattern of the control embryos and no significant difference in the amount of m-RNA was seen between the control and treated embryos.2. Expressions of transcriptional factors important for the development of the central nervous system were evaluated in the mice embryos treated with bis-diamine. Expression of EMX-1 was significantly reduced on 10.5 and 1 1.5 ED in the embryonic brain treated with bis-diamine, compared with that in control embryos. Expressional patterns of Wnt-3 and AP-2 were not affected by bis-diamine administration.3. Sox4 is a Sry-box family of transcriptional factors and exclusively expressed in the conal ridge of the outflow tract and the atrioventricular canal of embryonic hearts. The gene disruption in mice causes abnormal development of the semilunar valves, resulting in cardiac anomalies such as infundibular ventricular septal defect and persistent truncus arteriosus. Sox4 expressions in the embryonic brain and heart were down-regulated by bis-diamine administration.Expressional pattern of m-RNA shown in this study indicated that bis-diamine affected the development of the central nervous system and, subsequently, disturbed migration of neural crest cells into the heart. The contribution of PAX3 to the conotruncal septaion was not clear in this study. Sox4 may be involved in the migration of neural crest cells and the differentiation to the vascular smooth muscle cells.