Hox genes, their conserved derivatives, and the pathways responsible for their expression have been extensively studied in the fruit fly, Drosophila melanogaster;the experimentation done in the Drosophila model system has given developmental biologists tools to better understand the role and significance of Hox genes and their derivatives in anterior-posterior axis determination in the Drosophila embryo. Along with this, Drosophila research opened up the door to investigation on the conservation of Hox genes between vertebrates and invertebrates. Comparative embryology in mice, chickens, pufferfish, and zebrafish have shown conserved Hox gene expression patterns specifically along the anterior-posterior axis. Recently, comparative analysis performed on dorsal-ventral axis formation showed that patterning and segmentation of the spinal cord is influenced by the action of Hox genes as well. This review will briefly consider the evolution of the vertebrate brain and the evolution and conservation of Hox genes in regulating hindbrain patterning and spinal cord development. Show less

Mammalian Rbm45 is predominately expressed in neuronal tissue and is integral in brain development and neuronal differentiation under physiological conditions. Dysregulation of Rbm45 has been strongly associated with neurodegenerative disorders in humans and can drive hepatocellular carcinoma through reprogramming lipid metabolism. Intriguingly, Rbm45 is an ancient protein, evolutionarily conserved throughout metazoans, including in sponges which lack a nervous system. Curiously, the evolution of Rbm45 gene structure and protein domain conservation across kingdom Animalia is largely unknown. We performed phylogenetic analysis of Rbm45 nucleotide and amino acid sequences from 36 species representing 9 phyla: Porifera, Cnidaria, Priapulida, Mollusca, Brachiopoda, Arthropoda, Echinodermata, Hemichordata, and Chordata. While the tree from Rbm45 nucleotide sequence data resulted in clades Protostomia and Deuterostomia showing paraphyly, the phylogeny derived from Rbm45 amino acid sequence largely recapitulated known monophyletic relationships among metazoans. Human RBM45 protein structure includes three RNA-binding domains (RBD), a homo-oligomerization association (HOA) domain, a nuclear localization sequence (NLS), and a nuclear export sequence (NES). Multiple sequence alignment across the same 36 taxa used for phylogenetic analysis revealed conservation of all three RBDs, the HOA, and NLS; in contrast the NES was only detected in clade Craniata and not in clades Ambulacraria and Protostomia. Rbm45 gene structure analysis revealed increasing gene complexity concomitant with increasing evolutionary complexity. Rbm45 from non-bilaterian taxa had from 2 to 4 large exons, while bilaterian taxa had between 6 to17 small exons. These findings demonstrate that Rbm45 is an ancient, highly conserved gene among metazoans suggesting a function in a breadth of neural/sensory systems. Show less

A new type of mutations-dominant lethals with a facultative manifestation -were discovered in D. melanogaster in 2000. These mutations were named conditional mutations. Under restrictive genetic conditions, the mutations manifest themselves as dominant lethals, whereas dominant lethality disappears under permissive conditions, displaying a set of other manifestations. The genes responsible for the emergence of conditional mutations were named ontogenes. The experiments with mutations in ontogenes have revealed the following processes: (1) genome editing in germline cells; (2) induction of high mutagenesis rates in germline cells of the mutants for ontogenes; (3) zygotic selection; (4) isolation of mutants; and (5) alterations in the lethality of mutants with time. The specific features in the manifestation of ontogenes together with the listed processes formed the background for construction of the model of speciation named the regeneration model. The event of speciation is represented as the regeneration of the working state of a genetic system disturbed by the emergence of a mutation in an ontogene. According to the model, it is ontogenes that are in charge of speciation and, eventually, the structure of living matter in the form of individual species. The significance of Mendelian protein-coding genes and Darwinian selection of the fittest according to these genes are doubtless but not paramount. Show less