Department of Molecular and Cell Biology, Division of Genetics, Genomics, and Development, Center for Integrative Genomics, University of California, Berkeley, Berkeley, CA 94720-3204, USA.
Dev Biol. 2010 Mar 15;339(2):429-38. doi: 10.1016/j.ydbio.2010.01.002. Epub 2010 Jan 11.
Lymph hearts are pulsatile organs, present in lower vertebrates, that function to propel lymph into the venous system. Although they are absent in mammals, the initial veno-lymphatic plexus that forms during mammalian jugular lymph sac development has been described as the vestigial homologue of the nascent stage of ancestral anterior lymph hearts. Despite the widespread presence of lymph hearts among vertebrate species and their unique function, extremely little is known about lymph heart development. We show that Xenopus anterior lymph heart muscle expresses skeletal muscle markers such as myoD and 12/101, rather than cardiac markers. The onset of lymph heart myoblast induction can be visualized by engrailed-1 (en1) staining in anterior trunk somites, which is dependent on Hedgehog (Hh) signaling. In the absence of Hh signaling and upon en1 knockdown, lymph heart muscle fails to develop, despite the normal development of the lymphatic endothelium of the lymph heart, and embryos develop edema. These results suggest a mechanism for the evolutionary transition from anterior lymph hearts to jugular lymph sacs in mammals.
淋巴心是一种搏动性器官，存在于低等脊椎动物中，其功能是将淋巴液推进静脉系统。虽然哺乳动物中没有淋巴心，但在哺乳动物颈淋巴囊发育过程中形成的最初的静脉淋巴丛，已被描述为前淋巴心原始阶段的退化同源物。尽管淋巴心在脊椎动物物种中广泛存在，并且具有独特的功能，但对其发育过程却知之甚少。我们发现，非洲爪蟾前淋巴心肌肉表达肌肉骨骼标志物，如 myoD 和 12/101，而不是心脏标志物。通过在头胸部体节中对 engrailed-1 (en1)进行染色，可以观察到淋巴心成肌细胞的诱导起始，这依赖于 Hedgehog (Hh)信号。在没有 Hh 信号的情况下，并且在 en1 敲低的情况下，尽管淋巴心的淋巴管内皮正常发育，但淋巴心肌肉仍无法发育，胚胎会出现水肿。这些结果表明了哺乳动物从前淋巴心到颈淋巴囊的进化转变的一种机制。
