Gąsiorowski Ludwik, Andrikou Carmen, Janssen Ralf, Bump Paul, Budd Graham E, Lowe Christopher J, Hejnol Andreas
Department of Biological Sciences, University of Bergen, Thormøhlensgate 55, 5006 Bergen, Norway.
Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, 75236 Uppsala, Sweden.
Curr Biol. 2021 Aug 23;31(16):3629-3638.e2. doi: 10.1016/j.cub.2021.05.057. Epub 2021 Jun 23.
Excretion is an essential physiological process, carried out by all living organisms, regardless of their size or complexity. 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). Although some molecular similarities between the development of kidneys of vertebrates and the regeneration of the protonephridia of flatworms have been reported, the molecular underpinnings of the development of excretory organs have never been systematically studied in a comparative context. 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 protonephridia 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.
排泄是所有生物体都要进行的基本生理过程，无论其大小或复杂程度如何。原口动物（如苍蝇和扁虫）和后口动物（如人类和海胆）都拥有专门用于排泄的器官。这些器官呈现出惊人的多样性，从仅由少数不同细胞组成的单位（如原肾管）到由数百万个具有不同形态和功能的多种类型细胞构建的复杂结构（如脊椎动物的肾脏）。尽管已经报道了脊椎动物肾脏发育与扁虫原肾管再生之间的一些分子相似性，但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。在这里，我们表明一组转录因子（eya、six1/2、pou3、sall、lhx1/5和osr）和结构蛋白（nephrin、kirre和zo1）在帚虫、腕足动物、环节动物、有爪动物、鳃曳动物和半索动物的排泄器官中表达，这些动物代表了主要的原口动物谱系和非脊椎动物后口动物。我们证明，在脊椎动物肾脏和扁虫原肾管中观察到的分子相似性在这些动物发育中的排泄器官中也可见。我们的结果表明，所有类型的基于超滤的排泄器官都由一组保守的发育基因形成模式，这一观察结果支持了它们的同源性。我们提出，原口动物和后口动物的最后一个共同祖先已经拥有一个基于超滤的器官，该器官后来产生了现存排泄器官的巨大多样性，包括原肾管和后肾管。
