Eisenberg C A, Eisenberg L M
Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Dev Dyn. 1999 Sep;216(1):45-58. doi: 10.1002/(SICI)1097-0177(199909)216:1<45::AID-DVDY7>3.0.CO;2-L.
Cardiac tissue in the bird is derived from paired regions of lateral mesoderm within the anterior half of the embryo (Rawles [1943] Physiol. Zool. 16:22-42; Stalsberg and DeHaan [1969] Dev. Biol. 19:128-159). Previously, we reported that WNT11 is expressed in early avian mesoderm in a pattern that overlaps with the precardiac regions. To examine whether this molecule may play a role in promoting cardiogenesis, we cultured tissue explants from microdissected HH stage 4, 5, and 6 quail embryos. The isolated tissue consisted of both the mesoderm and endoderm layers from either anterior precardiac or posterior noncardiogenic regions of the embryo. As a necessary control for examining the ability of WNT11 to convert noncardiogenic mesoderm to cardiac tissue, we compared the cardiogenic potential of anterior and posterior regions. For stages 5 and 6, our results were consistent with what has been previously reported (Rawles [1943] Physiol. Zool. 16:22-42; Sugi and Lough [1994] Dev. Dyn. 200:155-162); as anterior mesoderm becomes contractile, while posterior mesoderm does not produce cardiac tissue. Surprisingly, when we examined stage 4 embryos both anterior and posterior regions gave rise to cardiac tissue in culture. To determine whether WNT11 could promote cardiac differentiation in tissue that was noncardiogenic, this molecule was ectopically expressed or added to mesoderm/endoderm explants obtained from stage 5 or 6 posterior tissue. Transfection of stage 5 posterior tissue with a WNT11 expression plasmid provoked the appearance of cardiomyocytes in 33% of the explants; half of which were contractile. Similarly transfected stage 6 posterior explants did not demonstrate cardiac differentiation. More dramatic results were obtained when noncardiogenic tissue was exposed to conditioned media containing soluble WNT11; as 63% and 33% of posterior stage 5- or stage 6-derived explants underwent cardiac differentiation. Together, these results indicate that WNT11 can promote cardiac development within noncardiac tissue. The expression of WNT11 in anterior mesoderm of early gastrula stage embryos suggests it may play a role in the formation of the vertebrate heart. Dev Dyn 1999;216:45-58.
鸟类的心脏组织源自胚胎前半部分中胚层的成对区域（罗尔斯[1943年]《生理动物学》16:22 - 42；斯塔尔伯格和德哈恩[1969年]《发育生物学》19:128 - 159）。此前，我们报道WNT11在早期鸟类中胚层中的表达模式与心脏前体区域重叠。为了研究该分子是否可能在促进心脏发生中起作用，我们培养了从HH 4期、5期和6期鹌鹑胚胎显微解剖得到的组织外植体。分离出的组织由胚胎心脏前体区域或非心脏后体区域的中胚层和内胚层组成。作为检测WNT11将非心脏中胚层转化为心脏组织能力的必要对照，我们比较了前后区域的心脏发生潜能。对于5期和6期，我们的结果与先前报道一致（罗尔斯[1943年]《生理动物学》16:22 - 42；杉和洛夫[1994年]《发育动力学》200:155 - 162）；即前中胚层开始收缩，而后中胚层不产生心脏组织。令人惊讶的是，当我们检测4期胚胎时，前后区域在培养中都产生了心脏组织。为了确定WNT11是否能促进非心脏组织中的心脏分化，将该分子异位表达或添加到从5期或6期后体组织获得的中胚层/内胚层外植体中。用WNT11表达质粒转染5期后体组织，33%的外植体中出现了心肌细胞；其中一半具有收缩性。同样转染的6期后体外植体未表现出心脏分化。当非心脏组织暴露于含有可溶性WNT11的条件培养基中时，得到了更显著的结果；5期或6期后体来源的外植体分别有63%和33%发生了心脏分化。总之，这些结果表明WNT11可以促进非心脏组织中的心脏发育。原肠胚早期胚胎前中胚层中WNT11的表达表明它可能在脊椎动物心脏形成中起作用。《发育动力学》1999年；216:45 - 58。
