Faculty of Nursing, School of Medicine, Tokai University, Kanagawa 259-1193, Japan.
Center for Experimental Animals, Institute of Research, Tokyo Medical and Dental University (TMDU), Tokyo 113-8510, Japan.
Biomolecules. 2023 Sep 22;13(10):1436. doi: 10.3390/biom13101436.
Eutherians have 11 retrotransposon Gag-like (RTL)/sushi-ichi retrotransposon homolog (SIRH) genes presumably derived from a certain retrovirus. Accumulating evidence indicates that the RTL/SIRH genes play a variety of roles in the current mammalian developmental system, such as in the placenta, brain, and innate immune system, in a eutherian-specific manner. It has been shown that the functional role of () in placental formation is unique to the therian mammals, as are the eutherian-specific roles of and in maintaining the fetal capillary network and the endocrine regulation of (aka ()) in the placenta. In the brain, is expressed in the corticospinal tract and hippocampal commissure, mammalian-specific structures, and in the corpus callosum, a eutherian-specific structure. Unexpectedly, at least three RTL/SIRH genes, , , and , play important roles in combating a variety of pathogens, namely viruses, bacteria, and fungi, respectively, suggesting that the innate immunity system of the brain in eutherians has been enhanced by the emergence of these new components. In this review, we will summarize the function of 10 out of the 11 RTL/SIRH genes and discuss their roles in eutherian development and evolution.
真兽类动物拥有 11 个假定来源于某种逆转录病毒的逆转录转座子 Gag 样（RTL）/ sushi-ichi 逆转录转座子同源（SIRH）基因。越来越多的证据表明，这些 RTL/SIRH 基因以真兽类动物特有的方式，在胎盘、大脑和先天免疫系统等哺乳动物的当前发育系统中发挥着多种作用。已经表明，（）在胎盘形成中的功能作用是有袋类哺乳动物所特有的，而（）在维持胎儿毛细血管网络中的作用以及（）在胎盘内分泌调节中的作用（又名（））也是真兽类动物所特有的。在大脑中，（）在皮质脊髓束和海马连合中表达，这些是哺乳动物特有的结构，而在胼胝体中表达，这是真兽类动物特有的结构。出人意料的是，至少有三个 RTL/SIRH 基因，即（）、（）和（），分别在对抗各种病原体（病毒、细菌和真菌）方面发挥着重要作用，这表明这些新成分的出现增强了真兽类动物大脑的先天免疫系统。在这篇综述中，我们将总结这 11 个 RTL/SIRH 基因中的 10 个的功能，并讨论它们在真兽类动物发育和进化中的作用。
