Genetic Basis of Morphological Transformations: Genes of the Noggin and Foxg1 Families as a Legacy of Whole Genome Duplications in Early Vertebrate Evolution

The hypothesis that whole genome duplications may have contributed to the origin and complexity of the vertebrate body plan was put forward in the 1970s. It was based on the analysis of the genome size of vertebrates and their closest relatives, the lancelets. The subsequent development of genetic technologies has confirmed this hypothesis and raised new questions—about the timing and number of these duplications/polyploidizations, about the fate of genes after duplication when the organism returns to an equilibrium diploid state (rediploidization), about the contribution of an increase in the number of specific genes to the formation of structures and traits. In this paper, we will briefly review the key issues related to genome duplication and consider the results of our work studying two gene families in phylogenetically basal groups of vertebrates. Genes of the Noggin and Foxg1 families have been described as key regulators of early ontogeny and the formation of vertebrate forebrain structures, including the telencephalon, a unique part. Historically, functional studies in classical laboratory objects (amphibians, birds, mice) have looked at one gene from each family. At the same time, we have shown that in evolutionarily ancient groups of vertebrates, such as agnathans (lampreys), cartilaginous fish and Chondrostei, these gene families are represented by several paralogues. In this context, the hypothesis that a multiple increase in the number of these key genes regulating early development could have been an important step in the formation of the body plan of modern vertebrates and the emergence of a number of their unique features that ensured the ecological stability and evolutionary success of the group seems quite reasonable.