Heterochrony of the Expression of Lanf and Foxg1 in the Lamprey Confirms the Appearance of the Telencephalon as an Evolutionarily Young Superstructure in the Central Nervous System of Vertebrates

One of the most important evolutionary innovations of vertebrates is a complexly structured telencephalon, which provides higher forms of nervous activity in animals and humans. This work is devoted to the study of the appearance of the telencephalon in the early stages of vertebrate evolution. At the same time, there is reason to believe that lampreys, due to their evolutionary antiquity, could retain some ancient expression patterns of genes that regulate the development of the brain in the very first vertebrates. The study of the features of spatio-temporal expression patterns of key genes that regulate the development of the forebrain in lampreys compared with other vertebrates can help to understand the molecular mechanisms underlying the appearance and evolutionary development of this unique structure of vertebrates. This paper presents the results from analyzing the gene-expression dynamics ofLanf,FoxG1,Otx2,Goosecoid, andHoxB9in the early stages of development of the European river lampreyLampetra fluviatilis. It was shown that lamprey genes involved in telencephalon differentiation (LanfandFoxG1) exhibit heterochrony of expression compared with more evolutionarily advanced representatives of vertebrates. This fact confirms the idea that the telencephalon, being evolutionarily the youngest part of the brain, could appear in vertebrate ancestors as a superstructure in the late stages of their embryonic development.