Data from: Here and there, but not everywhere: repeated loss of uncoupling protein 1 in amniotes

Endothermy is an evolutionary innovation in eutherian mammals and birds. In eutherian mammals, UCP1 is a key protein in adaptive nonshivering thermogenesis (NST). Although ucp1 arose early in the vertebrate lineage, the loss of ucp1 was previously documented in several reptile species (including birds). Here we determine that ucp1 was lost at the base of the reptile lineage, as we fail to find ucp1 in every major reptile lineage. Furthermore, though UCP1 plays a key role in mammalian NST, we confirm that pig has lost several exons from ucp1 and conclude that pig is not a sole outlier as the only eutherian mammal lineage to do so. Through similarity searches and synteny analysis, we show that ucp1 has also been lost/pseudogenized in Delphinidae (dolphin, orca) and potentially Xenarthra (sloth, armadillo) and Afrotheria (hyrax). These lineages provide models for investigating alternate mechanisms of thermoregulation and energy metabolism in the absence of functional UCP1. Further, the repeated losses of a functional UCP1 suggest the pervasiveness of NST via UCP1 across the mammalian lineage needs re-evaluation.恒温性（Endothermy）是真兽类哺乳动物与鸟类的一项演化创新。在真兽类哺乳动物中，解偶联蛋白1（UCP1）是适应性非颤抖性产热（adaptive nonshivering thermogenesis，NST）的关键蛋白。尽管ucp1基因在脊椎动物谱系中起源较早，但此前已有研究在多个爬行动物物种（包括鸟类）中报道了ucp1基因的丢失事件。本研究通过对各主要爬行动物谱系的检索发现，ucp1基因在所有类群中均未检出，由此确定ucp1基因在爬行动物谱系的基部即发生了丢失。此外，尽管UCP1在哺乳动物的适应性非颤抖性产热过程中发挥关键作用，但本研究证实猪的ucp1基因已丢失了数个外显子，且得出结论：猪并非唯一出现该情况的真兽类哺乳动物谱系。通过序列相似性搜索与共线性分析，本研究进一步发现，ucp1基因在海豚科（Delphinidae，包含海豚、虎鲸）中同样发生了丢失或假基因化，在异关节总目（Xenarthra，包含树懒、犰狳）和非洲兽总目（Afrotheria，包含蹄兔）中也存在类似的潜在丢失或假基因化情况。这些谱系为探究缺乏功能性UCP1时的体温调节与能量代谢的替代机制提供了理想的研究模型。进一步而言，功能性UCP1的多次独立丢失现象提示，跨哺乳动物谱系中依赖UCP1的适应性非颤抖性产热的普遍性需要被重新评估。