# Regeneration-Associated Factors in the Regulation of Adult and Post-Traumatic Neurogenesis in the Forebrain of Fish and Other Vertebrates

## TL;DR

This review explores how adult and post-traumatic neurogenesis is regulated in fish and other vertebrates, highlighting differences in regenerative abilities between species.

## Contribution

The paper presents new findings on neurogenesis in non-model salmon species and compares regenerative mechanisms across vertebrates.

## Key findings

- Salmon progenitor cells can differentiate into neurons after injury, unlike in mammals.
- Fish show restored neuronal conduction after TBI, while mammals form glial scars.
- Pax genes and molecular markers like vimentin and GFAP show functional specificity in neurogenesis.

## Abstract

This review summarizes a growing collection of data on adult neurogenesis in various vertebrate species, with a focus on teleost fish and mammals. Teleost fish serve as exceptional models for studying the dynamics of the cell cycle and the functions of adult neural stem progenitor cells (aNSPCs) throughout the central nervous system (CNS). New information about the characteristics of cells in various areas of the telencephalon of non-model objects—juvenile masu salmon Oncorhynchus masou and chum salmon Oncorhynchus keta—during postembryonic ontogenesis and after traumatic injury expands the current understanding of the issue. The expression of molecular markers of adult-type glial precursors in the model zebrafish and non-model objects, juveniles O. masou and O. keta, was presented. Immunohistochemical (IHC) verification of BrdU and PCNA made it possible to identify a population of rapidly and slowly proliferating cells in the pallium of intact O. masou and after traumatic brain injury (TBI). In salmonids, unlike in mammals, progenitor cells are able to differentiate into neurons after injury. The expression of vimentin and GFAP in the aNSCPs has functional specificity. A comparative analysis of the expression of Pax transcription factors in various vertebrates and juveniles O. masou is presented. Pax genes maintain cells in an undifferentiated state and ensure the spatiotemporal formation of mature cell types in changing developing neurogenic niches. The functions of glutamine synthetase (GS) and H2S in the brains of vertebrates and juvenile chum salmon under intact conditions and after TBI are characterized. In fish, unlike mammals, as a result of TBI, neuronal conduction is restored in the injury area, whereas in mammals the regenerative process is complicated by neuroinflammation and culminates in the formation of a glial scar.