expression of genes associated with atrial left-right morphogenesis in mouse embryos treated with retinoic acid

孕鼠在胚胎日龄（艾德）6.5天时用维甲酸（RA）处理，可在约30%的胚胎中诱导右异构、异常成环和AV垫发育不良，其中常伴有单侧心室发育不良。在这些胚胎中，由于室间隔和AV垫之间的排列不齐，发育不全心室的AV口通常狭窄。典型病例的房室垫为三叶，而非正常病例的两大二小叶。在本研究中，我们评估了心室运动在RA处理的胚胎在体内观察和心室面积测量，然后进行形态学检查。活胚胎的心脏运动的体内观察使我们能够准确地评估心室容积，不受固定状态的影响，如在标准形态学检查，并将其与心室动力学相关联。单侧心室发育不良的进展与特征性的流入道异常和流入道障碍有关。此外，在A类病例中，1例仅出现单侧流入延迟，另外5例同时出现单侧脑室发育不良和流入延迟，表明流入障碍可能先于脑室发育不良的进展。因此，左心室发育不全伴无脾综合征可能是由于左心室血流受限伴房室垫发育不良所致。接下来，我们检测了用维甲酸处理的母鼠的体节期胚胎中nodal和lefty的表达。这两个基因表达在左侧和/或右侧，并在一个spted和马赛克模式，在正常的胚胎谁表达的基因在左侧的连续模式。表达的时期是改变的和可变的。总之，维甲酸诱导的心脏异常是由基因表达和心内血流动力学改变引起的。

Retinoic acid (RA) treatment of pregnant mouse at embryonic day (ED) 6.5 induces right isomerism, anomalous looping and AV cushion dysplasia in about 30% of the embryos, in which unilateral ventricular hypoplasia was often associated. In such embryos, AV orifice to the hypoplastic ventricle was usually stenotic because of malalignment between the interventriclar septum and AV cushion. AV cushion has three lobes in the typical cases, instead of two major and two minor lobes in the normal ones. In the present study, we evaluated the ventricular motion in the RA-treated embryos by in-vivo observation and ventricular area measurement followed by morphological examination. In-vivo observation of the cardiac motion of live embryos enabled us to accurately evaluate the ventricular volume, not influenced by fixation state as in the standard morphological examination, and to correlate it with the ventricular dynamics. The progress of unilateral ventricular hypoplasia was associated with characteristic inflow tract anomaly and inflow disturbance. Furthermore, among cases of category A, one case had only unilateral inflow delay and the other 5 cases had both unilateral ventriclar hypoplasia and inflow delay, suggesting that inflow disturbance is likely to precede the progress of ventriclar hypoplasia. Thus, left ventricular hypoplasia with asplenia syndrome might be caused by inflow restriction to the left venrticle associated with AV cushion dysplasia. Next, we examined the expression of nodal and lefty in the somite stage embryos from dams treated with retinoic acid. Both genes were expressed on left and/or right side and in a sptted and mosaic pattern, in contrast to normal embryos who express the genes on the left side in a continuous pattern. The period of expression was altered and variable. In summary, retinoic acid-induced cardiac anomaly was caused by altered gene expression and intracardiac hemodynamics.