排泄是一个重要的生理过程,由所有生物体进行,无论它们的大小或复杂性如何。1-3两种原虫(例如,苍蝇和扁虫)和子宫造口术(例如,人类和海胆)拥有专门的排泄器官。这些器官表现出惊人的多样性,范围从由几个不同的单元组成的单元(例如,protronephridia)到复杂的结构,由数百万个形态和功能不同的多种类型的细胞构建(例如,脊椎动物肾脏).4,5尽管据报道,脊椎动物肾脏的发育与扁形蠕虫的质子神经再生之间存在一些分子相似性,6,7排泄器官发育的分子基础从未在比较背景下进行过系统研究。4这里,我们证明了一组转录因子(eya,six1/2pou3sall,lhx1/5和osr)和结构蛋白(nephrin,Kirre,和zo1)在类星体的排泄器官中表达,腕足动物,annelid,onychophoran,priapulid,代表主要的原生质体谱系和非脊椎动物氘代。我们证明,在脊椎动物肾脏和扁虫原肾6,7中观察到的分子相似性也可见于这些动物的发育排泄器官中。我们的结果表明,所有类型的基于超滤的排泄器官都被一组保守的发育基因图案化,支持它们同源性的观察结果。我们认为,原虫和氘代的最后一个共同祖先已经拥有一个基于超滤的器官,后来产生了现存排泄器官的巨大多样性,包括原虫和后脑虫。
Excretion is an essential physiological process, carried out by all living organisms, regardless of their size or complexity.1-3 Both protostomes (e.g., flies and flatworms) and deuterostomes (e.g., humans and sea urchins) possess specialized excretory organs serving that purpose. Those organs exhibit an astonishing diversity, ranging from units composed of just few distinct cells (e.g., protonephridia) to complex structures, built by millions of cells of multiple types with divergent morphology and function (e.g., vertebrate kidneys).4,5 Although some molecular similarities between the development of kidneys of vertebrates and the regeneration of the protonephridia of flatworms have been reported,6,7 the molecular underpinnings of the development of excretory organs have never been systematically studied in a comparative context.4 Here, we show that a set of transcription factors (eya, six1/2, pou3, sall, lhx1/5, and osr) and structural proteins (nephrin, kirre, and zo1) is expressed in the excretory organs of a phoronid, brachiopod, annelid, onychophoran, priapulid, and hemichordate that represent major protostome lineages and non-vertebrate deuterostomes. We demonstrate that the molecular similarity observed in the vertebrate kidney and flatworm protonephridia6,7 is also seen in the developing excretory organs of those animals. Our results show that all types of ultrafiltration-based excretory organs are patterned by a conserved set of developmental genes, an observation that supports their homology. We propose that the last common ancestor of protostomes and deuterostomes already possessed an ultrafiltration-based organ that later gave rise to the vast diversity of extant excretory organs, including both proto- and metanephridia.