Department of Embryology, Faculty of Biology, Saint Petersburg State University, Saint Petersburg, Russia.
Institute of Cytology, Russian Academy of Sciences, Saint Petersburg, Russia.
Open Biol. 2022 Feb;12(2):210336. doi: 10.1098/rsob.210336. Epub 2022 Feb 23.
Sponges (phylum Porifera) are early-branching animals, whose outwardly simple body plan is underlain by a complex genetic repertoire. The transition from a mobile larva to an attached filter-feeding organism occurs by metamorphosis, a process accompanied by a radical change of the body plan and cell transdifferentiation. The continuity between larval cells and adult tissues is still obscure. In a previous study, we have produced polyclonal antibodies against the major protein of the flagellated cells covering the larva of the sponge , used them to trace the fate of these cells and shown that the larval flagellated cells transdifferentiate into the choanocytes. In the present work, we identified the sequence of this novel protein, which we named ilborin. A search in the open databases showed that multiple orthologues of the newly identified protein are present in sponges, cnidarians, flatworms, ctenophores and echinoderms, but none of them has been described yet. Ilborin has two conserved domains: triosephosphate isomerase-barrel, which has enzymatic activity against macroergic compounds, and canonical EF-hand, which binds calcium. mRNA of ilborin is expressed in the larval flagellated cells. We suggest that the new protein is involved in the calcium-mediated regulation of energy metabolism, whose activation precedes metamorphosis.
海绵动物（多孔动物门）是早期分支的动物，其外在简单的身体结构由复杂的遗传组成所支撑。从游动的幼虫到附着的滤食生物的转变是通过变态发生的，这个过程伴随着身体结构和细胞转分化的根本变化。幼虫细胞和成年组织之间的连续性仍然不清楚。在之前的一项研究中，我们制备了针对覆盖海绵幼虫的鞭毛细胞的主要蛋白质的多克隆抗体，用它们来追踪这些细胞的命运，并表明幼虫的鞭毛细胞会转分化为领细胞。在本工作中，我们鉴定了这种新蛋白的序列，我们将其命名为 ilborin。在开放数据库中的搜索表明，新鉴定的蛋白质在海绵动物、刺胞动物、扁形动物、栉水母和棘皮动物中存在多个直系同源物，但它们尚未被描述。Ilborin 有两个保守结构域：三磷酸甘油醛异构酶桶，它对宏观能化合物具有酶活性，以及经典的 EF 手，它可以结合钙。ilborin 的 mRNA 在幼虫的鞭毛细胞中表达。我们认为，这种新蛋白参与了钙介导的能量代谢调节，其激活先于变态发生。
