Park M, Lewis C, Turbay D, Chung A, Chen J N, Evans S, Breitbart R E, Fishman M C, Izumo S, Bodmer R
Department of Biology, University of Michigan, 830 N. University, Ann Arbor, MI 48109-1048, USA.
Proc Natl Acad Sci U S A. 1998 Aug 4;95(16):9366-71. doi: 10.1073/pnas.95.16.9366.
tinman, a mesodermal NK2-type homeobox gene, is absolutely required for the subdivision of the early Drosophila mesoderm and for the formation of the heart as well as the visceral muscle primordia. Several vertebrate relatives of tinman, many of which are predominately expressed in the very early cardiac progenitors (and pharyngeal endoderm), also seem to promote heart development. Here, we show that most of these vertebrate tinman-related genes can readily substitute for Drosophila tinman function in promoting visceral mesoderm-specific marker gene expression, but much less in promoting cardiac-specific gene expression indicative of heart development. In addition, another mesodermal NK2-type gene from Drosophila, bagpipe, which is normally only needed for visceral mesoderm but not heart development, cannot substitute for tinman at all. These data indicate that the functional equivalence of the tinman-related subclass of NK2-type genes (in activating markers of visceral mesoderm development in Drosophila) is specific to this subclass and distinct from other homeobox genes. Despite the apparent overall conservation of heart development between vertebrates and invertebrates, the differential rescue of visceral mesoderm versus heart development suggests that some of the molecular mechanisms of organ formation may have diverged during evolution.
tinman是一种中胚层NK2型同源框基因，对于早期果蝇中胚层的细分以及心脏和内脏肌肉原基的形成是绝对必需的。tinman的几个脊椎动物同源基因，其中许多主要在非常早期的心脏祖细胞（和咽内胚层）中表达，似乎也促进心脏发育。在这里，我们表明，这些脊椎动物中与tinman相关的大多数基因在促进内脏中胚层特异性标记基因表达方面能够很容易地替代果蝇tinman的功能，但在促进指示心脏发育的心脏特异性基因表达方面则效果要差得多。此外，果蝇的另一个中胚层NK2型基因bagpipe，通常仅在内脏中胚层而不是心脏发育中需要，根本不能替代tinman。这些数据表明，NK2型基因的tinman相关亚类（在激活果蝇内脏中胚层发育标记方面）的功能等效性是该亚类特有的，并且与其他同源框基因不同。尽管脊椎动物和无脊椎动物之间心脏发育明显总体保守，但内脏中胚层与心脏发育的差异拯救表明，器官形成的一些分子机制在进化过程中可能已经发生了分歧。
