Transcriptomes in avian and mammalian brains: tackling evolutionary debates

“The thorniest problem” in comparative neurobiology is the identification of the particular brain region of birds and reptiles that corresponds to the neocortex, a structure unique to mammals. Anatomical, hodological, embryological and gene expression data (based on few select genes) provide conflicting answers. Studies of embryonic neurogenesis and cell migration have informed homology of developmental territories but the striking similarities in lamination, connectivity and physiological properties observed between adult forms derived from non-corresponding pallial regions remain unexplained. Using RNA-seq, we explored which genes are actively transcribed in these regions of controversial ancestry in a representative bird (chicken) and mammal (mouse) at adult stages.

比较神经生物学（comparative neurobiology）领域最棘手的难题，是鉴定鸟类与爬行类中对应哺乳动物独有结构——新皮层（neocortex）的特定脑区。解剖学、神经通路追踪（hodological）、胚胎学以及基因表达数据（基于少量筛选基因）给出了相互矛盾的结论。胚胎神经发生与细胞迁移相关研究，曾为发育区域的同源性判定提供了佐证，但源自非对应脑皮区域的成年脑区结构，其分层结构、连接特性与生理属性却呈现出显著相似性，这一现象至今仍未得到合理解释。本研究借助RNA测序（RNA-seq）技术，针对成年阶段代表性鸟类（家鸡）与哺乳动物（小鼠）中演化起源存在争议的上述脑区，对其活跃转录的基因展开了探究。