Ontogenez

The present study focuses on the potential component structure of prenerve transmitter systems in cells of pre-implantation mammalian embryos. A number of classical neurotransmitters have been shown to exhibit functional activity at the early stages of the development of multicellular organisms, including mammals. The present study provides analysis of the expression of key neurotransmitter systems components during early mouse development using accessible next-generation sequencing and transcriptomics data. The findings indicate the presence of receptors and other components of numerous transmitter systems in oocytes and embryos, encompassing serotoninergic, dopaminergic, adrenergic, cholinergic, GABAergic systems, as well as glutamate and histamine systems. The observed diversity suggests the possible convergence of different transmitter systems in the regulation of cell proliferation, differentiation and morphogenesis at the level of common terminal elements of intracellular signalling cascades and effectors. These results offer novel insights and directions for further research, particularly concerning the interactions between diverse transmitters and their function in regulating cellular differentiation and morphogenesis.

In Drosophila melanogaster, as in all Opisthokonta, the evolutionary conserved protein NXF1 (Nuclear eXport Factor 1) is responsible for nuclear export of mRNA from the nucleus to the cytoplasm. Traditionally, it is thought that after leaving the nuclear pore, the NXF1 leaves the mRNP complex and returns to the nucleus. We have shown for the first time that in Drosophila the NXF1 protein presents in the cytoplasm of various cells, including nerve cells. The cytoplasmic localisation of the NXF1 indicates that nuclear export function is not the only function of this protein. The Nxf1 gene in Drosophila has the historically established name sbr (small bristles). A number of mutations in the sbr are characterised by dominant phenotypic effects. In particular, the sbr¹² mutant allele leads to abnormalities in Drosophila brain formation. Characteristic morphological defects in the neuropils of the optic lobe suggest that the NXF1 (SBR) is involved in the regulation of the spatial architecture of the fly brain, including the formation of neuropil boundaries. The evolutionary conservatism of Nxf1 opens up the possibility of studying the role of the NXF1 protein in the development of the nervous system using Drosophila as a model.

The pineal complex and associated brain structures make up the epithalamus. In embryonic development, they form as an evaginations of the diencephalon roof. The structures of the epithalamus are of great interest among scientists due to their involvement in vital physiological functions of mammalian and other vertebrates. Of particular interest are animals in which the pineal complex has a photoreceptor function and includes a parapineal organ (parietal eye). It is described in lampreys, some teleosts, anurans and reptiles in which it is particularly complex. For the first time, we described the early stages of the development of the paraphysis and epiphysis in a representative of the family Diplodactylidae, the gecko Correlophus ciliatus. These primordia are evaginations of the roof of diencephalon, localized on its anterior and posterior borders. At the same time with epithalamic structures in this area of the brain, a network of blood vessels develops. The formation of a blood sinus in the parietal region of the embryo occurs by the 33rd stage of development, before the appearance of the skull. An analysis of the literature showed that the features of the development of the primordia of epithalamic structures in C. ciliatus are similar to the development of these structures in turtles, in which, like in gecko, the pineal complex does not have a parapineal organ.

In vertebrates, oogonial stem cells (OSCs) contribute to oogenesis in some fish, amphibians, and reptiles, enabling the production of new oocytes during each reproductive cycle. Classical literature from the 19th and 20th centuries established the prevailing notion that, in mammals and birds, the ovarian reserve is formed exclusively during embryogenesis, with OSCs absent in postnatal and adult ovaries. However, in 2004, OSCs were first identified in the ovaries of adult female mice, challenging the long-standing dogma that postnatal neo-oogenesis is impossible in mammals. Despite an increasing number of studies, this issue remains controversial. Advances in molecular and cellular techniques have significantly expanded our understanding of oogenesis across various animal groups. Notably, a recent study of adult chicken ovaries identified the presence of OSCs, further questioning traditional assumptions about ovarian biology in birds. In this review, we examine the evidence for postnatal oogenesis in this group of vertebrates.