Ontogenez

Tandem repeating elements that form extended polypurine/polypyrimidine tract sequences have been found in the genomes of various species. Their structural properties bend the DNA helix and cause a transition to non-canonical DNA secondary structures. The modern scientific literature describes many examples of the involvement of such elements in the regulation of gene expression and the formation of alternative transcripts in cells of different types of differentiation (Matos-Rodrigues et al., 2023). Previously, we described the (GGAAA)n repeating element of chicken (Gallus gallus domesticus), which is predominantly localized on the sex chromosome W and makes up about 1% of the female genome (Komissarov et al., 2018). Here we describe the localization peculiarities of this tandem repeat in the chicken genome within autosomes and the sex chromosome Z. The study identified a number of genes carrying tandemly repeated (GGAAA)n elements within non-coding transcribed regulatory regions that can influence expression intensity and the formation of alternative transcripts. Functional characterization of genes carrying stacks of (GGAAA)n allowed us to suggest the involvement of these tandem repeats in regulating the differential activity of genes important for the development of sexual dimorphism traits in chicken.

The paradigm within which the scientific community views animal adult stem cells (ASCs) and the concept of “stemness” itself was changed significantly over the past five years. According to the previously dominant paradigm, formed during the study of mammals, adult stem cells are extremely few in number, committed lineage-specific cells; their fates are limited to the tissues/organs in which they are located. However, studies performed on aquatic invertebrates have shown that ASCs, on the contrary, are very numerous, morphologically diverse, and demonstrate a wide range of states and levels of “stemness”. Moreover, ASCs of a number of invertebrates can arise de novo by transdifferentiation from differentiated somatic cells. One of the key roles in the formation of the new paradigm was played by the study of representatives of the phylum Porifera. This brief review examines the state of the arts of the modern concept of stem cells and the role of spongiology in the formation of the new paradigm.

On November 11, Dmitry Antonovich Sakharov (1930–2024), a unique person, mentor, scientist and poet, passed away. This year, the world community celebrates the 50th anniversary of the publication of his book “Genealogy of Neurons”, which had a profound influence on several generations of neuroscientists. The hypotheses, strategies and experimental approaches presented in this book remain relevant and inspiring today. We outline Sakharov’s hypotheses on neuronal polyphyly and the functional significance of neuronal heterogeneity in light of recent comparative, genomics, and single-cell transcriptomic data.