Cell type profiling in salamanders identifies innovations in vertebrate forebrain evolution [E4]. Cell type profiling in salamanders identifies innovations in vertebrate forebrain evolution [E4]

The evolution of advanced cognition in vertebrates is associated with the expansion of specialized areas in the forebrain (the six-layered neocortex in mammals and the dorsal ventricular ridge in birds and reptiles). Both areas exhibit complementary higher order brain functions, but it remains debated whether they developed convergently, or descended from a brain region already present in the last common ancestor of amniotes. To reconcile these views, we investigated the development, molecular identity, and connectivity of telencephalic neuron types in the Spanish newt, Pleurodeles waltl. These reveal that major neuron classes are conserved in tetrapods. Additionally, a glutamatergic neuron type in the ventral pallium displays key characteristics similar to the reptilian dorsal ventricular ridge (aDVR) and the mammalian piriform cortex (PC), suggesting that brain areas for advanced cognition evolved independently in mammals and reptiles and birds. Overall design: scRNAseq of Pleurodeles Waltl telencephalon

脊椎动物高级认知的演化过程，与前脑特化区域的扩张密切相关：哺乳动物的对应区域为六层新皮层（six-layered neocortex），鸟类与爬行类则为背侧室嵴（dorsal ventricular ridge）。两类区域均展现出互补的高阶脑功能，但二者究竟是通过趋同演化形成，还是起源于羊膜动物（amniotes）最后共同祖先中已存在的脑区，目前仍存在学术争议。为调和这两种观点，本研究对西班牙肋突螈（Pleurodeles waltl）端脑（telencephalon）的神经元类型的发育过程、分子特征及连接模式进行了探究。研究结果显示，主要的神经元类别在四足动物（tetrapods）中具有保守性。此外，腹侧皮层板（ventral pallium）中的一类谷氨酸能神经元，展现出与爬行类背侧室嵴（aDVR）及哺乳类梨状皮层（piriform cortex，PC）相似的关键特征，这表明负责高级认知的脑区在哺乳类与爬行类、鸟类中是独立演化而来的。实验整体设计：西班牙肋突螈端脑的单细胞RNA测序（scRNAseq）