Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA.
Department of Biological Sciences, North Dakota State University, Fargo, ND 58108, USA.
Proc Biol Sci. 2022 Feb 23;289(1969):20212278. doi: 10.1098/rspb.2021.2278.
The insulin and insulin-like signalling (IIS) network plays an important role in mediating several life-history traits, including growth, reproduction and senescence. Although insulin-like growth factors (IGFs) 1 and 2 are both key hormones in the vertebrate IIS network, research on IGF2 in juveniles and adults has been largely neglected because early biomedical research on rodents found negligible IGF2 postnatal expression. Here, we challenge this assumption and ask to what degree IGF2 is expressed during postnatal life across amniotes by quantifying the relative gene expression of and using publicly available RNAseq data for 82 amniote species and quantitative polymerase chain reaction on liver cDNA at embryonic, juvenile and adult stages for two lizard, bird and mouse species. We found that (i) is expressed postnatally across amniote species and life stages-often at a higher relative expression than , contradicting rodent models; (ii) the lack of rodent postnatal expression is due to phylogenetic placement, not inbreeding or artificial selection; and (iii) adult expression is sex-biased in some species. Our results demonstrate that expression is typical for amniotes throughout life, suggesting that a comprehensive understanding of the mechanisms mediating variation in life-history traits will require studies that measure both IGFs.
胰岛素和胰岛素样信号（IIS）网络在介导多种生活史特征方面发挥着重要作用，包括生长、繁殖和衰老。尽管胰岛素样生长因子（IGF）1 和 2 都是脊椎动物 IIS 网络中的关键激素，但 IGF2 在幼体和成体中的研究在很大程度上被忽视了，因为早期对啮齿动物的生物医学研究发现 IGF2 出生后表达可忽略不计。在这里，我们通过量化 82 种羊膜动物物种的 和 相对基因表达，以及对两种蜥蜴、鸟类和鼠类物种的胚胎、幼体和成年阶段的肝 cDNA 进行定量聚合酶链式反应，挑战了这一假设，并询问 IGF2 在多大程度上在羊膜动物的整个生命过程中表达。我们发现：（i） 在羊膜动物物种和生命阶段都有表达，通常比 表达更高，与啮齿动物模型相反；（ii） 缺乏啮齿动物出生后表达是由于系统发育位置，而不是近亲繁殖或人工选择；（iii） 在一些物种中， 表达在成年阶段存在性别偏倚。我们的结果表明， 在整个生命过程中都是羊膜动物的典型表达，这表明要全面了解介导生活史特征变化的机制，将需要测量两种 IGF 的研究。
