[Hox Genes and Animal Regeneration].

The concept of regeneration is intimately associated with ideas about positional information, that is, the distribution of various signals prescribing cells their location in an embryo or an adult organism. Hox genes are perfect candidates for the role of factors creating positional information. Their main function is thought to be regionalization of the embryo and the determination of the anterior/posterior (A/P) axis of the bilaterian body according to the rules of temporal and spatial colinearity. At the same time, Hox genes are also expressed postembryonically and may participate in various processes in the adult body. In particular, Hox genes are involved in regeneration, as shown on animals from different evolutionary clades. During reparation Hox genes are responsible for regionalization and specification of the newly formed structures, which reflects their embryonic role. This is not all, however. Hox transcription patterns in some adult organisms and their expression dynamics after damage suggest that Hox genes are involved in creating positional information in the adult body. This information is necessary for consistent reparation, while its fast reorganization may accelerate the reparative process.

[Regulatory evolution, Hox-genes, and larvae of bilateral animals].

This review presents the contemporary views on the evolutionary nature of the trochophore-like larva of bilateral animals.

[Hox-cluster and evolution of morphogeneses].

Comparative studies of genomes of lower Metazoa showed that many classes of transcription factors important for the development of bilateral animals appeared before the divergence of modem branches of the animal kingdom. The genes of the Hox-cluster appeared late, in the last common ancestor of Cnidaria and Bilateria. Structural expansion and perfection of mechanisms which integrate the Hox-cluster can be traced in the morphogenesis of modern bilateral animals. It is now evident that different strategies of using this regulator instrument led Bilateria to absolute domination in number and diversity of species among all Metazoa animals.