POSITIONAL SPECIFICATION OF VENTRICULAR MYOSIN LIGHT CHAIN-2 EXPRESSION IN THE PRIMITIVE MURINE HEART TUBE
POSITIONAL SPECIFICATION OF VENTRICULAR MYOSIN LIGHT CHAIN-2 EXPRESSION IN THE PRIMITIVE MURINE HEART TUBE
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DOI：
10.1073/pnas.90.11.5157
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发表时间：
1993-06-01
影响因子：
11.1
通讯作者：
CHIEN, KR
中科院分区：
文献类型：
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作者：
OBRIEN, TX;LEE, KJ;CHIEN, KR
为了研究心脏发生过程中心室规范的过程，我们检测了小鼠胚胎发生过程中心室肌球蛋白轻链 2 (MLC-2v) mRNA 的原位表达。通过与特定 MLC-2v 核糖核酸探针杂交进行评估，性交后第 8.0 天 (pc) 在心室区域可以发现 mRNA 表达。 MLC-2v 在心管心室部分表达较高，在心房或窦静脉区域未检测到表达。此时，心管的近端流出道也以最低可检测水平表达 MLC-2v mRNA，但随后显示出时间和空间上不同的模式，在第 9-10 天时，在邻近心室段的近端流出道区域中很好地建立了表达，最终达到与小梁心室心肌相当的水平。到第11天，在间隔完成之前，表达随后变得仅限于房室垫水平及其以下的心室区域。含有与荧光素酶报告基因融合的 250 个碱基对 MLC-2v 启动子片段的转基因小鼠至少从第 9 天起就表现出报告基因活性。通过免疫荧光和显微解剖心房和心室肌肉样本中报告基因活性的直接测定来评估，荧光素酶报告基因在胚胎心脏中的心室区域限制性表达至少从PC的第15天起得到证实。总而言之，这为原始心管中 MLC-2v 基因表达的早期位置规范提供了证据，并表明部分心室肌基因程序的区域规范可以在哺乳动物心脏发生过程中发生在心室间隔之前。由于 250 个碱基对的启动子片段在转基因小鼠中处于发育活跃状态，因此将其确立为发育中心管中心室规范过程的分子靶标。
To study the process of ventricular specification during cardiogenesis, we examined the in situ expression of cardiac ventricular myosin light chain 2 (MLC-2v) mRNA during murine embryogenesis. As assessed by hybridization with a specific MLC-2v riboprobe, mRNA expression can be found in the ventricular region at day 8.0 postcoitum (pc). MLC-2v expression is high in the ventricular portion of the heart tube, with no detectable expression in the atrial or sinus venosus regions. The proximal outflow tract of the heart tube also expresses MLC-2v mRNA at minimally detectable levels at this time but then displays a temporally and spatially distinct pattern with expression well established in the proximal out-flow tract region adjacent to the ventricular segment by days 9-10 pc, eventually reaching levels comparable to the trabeculated ventricular myocardium. By day 11 pc, prior to the completion of septation, expression then becomes restricted to the ventricular region at and below the level of the atrioventricular cushion. Transgenic mice harboring a 250-base-pair MLC-2v promoter fragment fused to a luciferase reporter gene demonstrate reporter gene activity from at least day 9 pc. Ventricular region-restricted expression of the luciferase reporter in the embryonic heart, as assessed by immunofluorescence and direct assay of reporter activity in microdissected atrial and ventricular muscle specimens, was confirmed from at least day 15 pc on. Taken together, this provides evidence for early positional specification of MLC-2v gene expression in the primitive heart tube and indicates regional specification of part of the ventricular muscle gene program can precede ventricular septation during mammalian cardiogenesis. Since the 250-base-pair promoter fragment is active developmentally in transgenic mice, this establishes it as a molecular target for the process of ventricular specification in the developing heart tube.