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Neurogenesis is the process by which new brain cells are formed. This crucial event emerges during embryonic life and proceeds in adulthood, and it could be influenced by environmental pollution. Non-combustion-derived magnetite represents a portion of the coarse particulate matter (PM) contributing to air and water pollution in urban settings. Studies on humans have reported that magnetite and other iron oxides have significant damaging effects at a central level, where these particles accumulate and promote oxidative stress. Similarly, magnetite nanoparticles can cross the placenta and damage the embryo brain during development, but the impact on neurogenesis is still unknown. Furthermore, an abnormal Fe cation concentration in cells and tissues might promote reactive oxygen species (ROS) generation and has been associated with multiple neurodegenerative conditions. In the present study, we used zebrafish as an in vivo system to analyze the specific effects of magnetite on embryonic neurogenesis. First, we characterized magnetite using mineralogical and spectroscopic analyses. Embryos treated with magnetite at sub-lethal concentrations showed a dose-response increase in ROS in the brain, which was accompanied by a massive decrease in antioxidant genes ( sod2 , cat , gsr , and nrf2 ). In addition, a higher number of apoptotic cells was observed in embryos treated with magnetite. Next, interestingly, embryos exposed to magnetite displayed a decrease in neural staminal progenitors ( nestin , sox2 , and pcna markers) and a neuronal marker ( elavl3 ). Finally, we observed significative increases in apoeb (specific microglia marker) and interleukin-1b ( il1b ), confirming a status of inflammation in the brain embryos treated with magnetite. Our study represents the very first in vivo evidence concerning the effects of magnetite on brain development.

In vertebrates, neurotrophins and their receptors play a fundamental role in the central and peripheral nervous systems. Several studies reported that each neurotrophin/receptor signalling pathway can perform various functions during axon development, neuronal growth, and plasticity. Previous investigations in some fish species have identified neurotrophins and their receptors in the spinal cord under physiological conditions and after injuries, highlighting their potential role during regeneration. In our study, for the first time, we used an excellent animal model, the zebrafish ( Danio rerio ), to compare the mRNA localization patterns of neurotrophins and receptors in the spinal cord. We quantified the levels of mRNA using qPCR, and identified the transcription pattern of each neurotrophin/receptor pathway via in situ hybridization. Our data show that ngf/trka are the most transcribed members in the adult zebrafish spinal cord., Competing Interests: The authors declare no conflict of interest.

Simple Summary: Fertility, in males and females, is linked to the correct formation of sexual line cells (spermatozoa and oocytes) through a physiological process called meiosis. In all vertebrates, meiosis is orchestrated by different molecular effectors, and among these, we focused our attention on CLASP2, a protein involved in cytoskeleton function. In several animal models, such as mice, flies, or frogs, this protein is known to participate in spermatozoa maturation. However, in fish, nothing was known about the presence of CLASP2 in sexual organs or whether it could have a role in spermatozoa formation. To investigate this point, we used two excellent vertebrate aquatic models: guppy and zebrafish. Our results open a window to knowledge about male sex cell formation effectors in fish. Considering the great affinity between zebrafish and humans, the study of CLASP2 in fish spermatogenesis could uncover a new target of male fertility in humans. Cytoplasmic linker-associated protein-2 (CLASP2) is a member of the CLIP-associating proteins (CLASPs) family involved in the structure and function of microtubules and Golgi apparatus. Several studies performed using different mammalian and non-mammalian model organisms reported that CLASP2 controls microtubule dynamics and the organization of microtubule networks. In Drosophila and mice, an important role of CLASP2 during the development of germ cell lines has been uncovered. However, no study has clearly defined its role during fish germ cell differentiation. In the present study, we used two excellent aquatic animal models among teleost fish: zebrafish (Danio rerio) and guppy (Poecilia reticulata). Using qPCR, we found that the clasp2 transcript level is significantly high in the testis of both fish. Then, by in situ hybridization, we localized the clasp2 transcript in the spermatozoa of zebrafish and the spermatozeugmata of guppy. Our data suggest a potential role for this gene in the last stage of spermiogenesis in fish. [ABSTRACT FROM AUTHOR]