Neuroendocrine Regulations in Fish: Role of Environmental and Internal Factors

Editorial

15 August 2024

Editorial: Neuroendocrine regulations in fish: role of environmental and internal factors

Romain Fontaine

Paula Gabriela Vissio

and

Dianne M. Baker

722 views

0 citations

Editors

Romain Fontaine

Norwegian University of Life Sciences

Paula Gabriela Vissio

University of Buenos Aires

Impact

Double-labeled pituitaries from transgenic tilapia with labeled LH [(A, I, E, M) magenta] and FSH cells [(F, N) green] and immunofluorescence-stained for GH [(B, J) yellow] were used for in situ hybridization chain reaction (HCR) (v3.0) to determine co-localization of mRNA expression of different sstr genes [(C) sstr2a; (K) sstr5b; (G) sstr3a; (O) sstr3b; cyan). Nuclei are stained with DAPI [(D, L, H, P) blue]. In the merged box, magenta arrows show LH cells, green arrows show FSH, and yellow arrows show GH cells. Scale bar, 10 µm.

Original Research

21 June 2024

Characterization of the somatostatin system in tilapia: implications for growth and reproduction

Naama Mizrahi

, 4 more and

Berta Levavi-Sivan

2,099 views

1 citations

Methods

09 October 2023

Simultaneous extraction and detection of peptides, steroids, and proteins in small tissue samples

Chunyu Lu

, 4 more and

Vance L. Trudeau

3,014 views

5 citations

In primary growth oocytes, Aqp1ab1 is phosphorylated at Ser253 by protein kinase A (PKA), which is activated by a yet unknown signaling pathway, to bind YwhazLa and -zLb. The complex is then slowly transported to the oocyte cortical region during the vitellogenic period, where it is retained just below the oocyte plasma membrane in postvitellogenic oocytes, while some of Aqp1ab1 enters the basal region of the oocyte microvilli. The release of circulating hypohysial Avp and luteinizing hormone (Lh) from capillaries in the theca layer at the time of oocyte maturation activate the Avpr2aa in theca and granulosa cells, as well as the Lh/choriogonadotropin receptor (Lhcgr) in the granulosa cells. In the theca and granulosa, the Avp-stimulated Avpr2aa triggers PKA activation, which mediates the phosphorylation of Thr262 in Aqp1ab2 promoting the binding to YwhazLb and the trafficking of the channel to the plasma membrane of these cells. The activation of the Lhcgr-PKA pathway in granulosa cells drives the synthesis of the progestagen 17,20β-P, through a switch in the steroidogenic (StG) pathway from estrogen to progestagen production. The 17,20β-P, in turn stimulates the local synthesis of Avp through a genomic mechanism mediated by the nuclear progestin receptor (nPgr). The resulting release of Avp and 17,20β-P from the granulosa cells respectively activates the Avpr2aa and the membrane progestin receptor (mPgr) in the oocyte surface. The mPr triggers meiosis resumption (oocyte maturation), whereas the Avpr2aa-PKA signaling regulates the trafficking of Aqp1ab2 as in follicle cells, and a secondary phosphorylation of Ser156 in the loop D of Aqp1ab1 channels already complexed with YwhazLa/b. The secondary phosphorylation of Aqp1ab1 further shuttles the channel to the most distal region of the oocyte microvilli. Finally, systemic (circulating) and/or local levels of Avp, or a possible Lh-mediated production of Oxt, may potentially activate the protein kinase C (PKC) signaling pathway in the epithelium, through a yet unidentified receptor, to induce the recycling of Aqp1aa. This model integrates both the systemic and paracrine vasopressinergic regulation of the intracellular trafficking of Aqp1ab-type paralogs in the seabream oocyte, such that competitive plasma membrane spatial occupancy by both channels is avoided and bulk water influx is augmented during oocyte hydration.

Original Research

11 August 2023

Neurohypophysial and paracrine vasopressinergic signaling regulates aquaporin trafficking to hydrate marine teleost oocytes

Alba Ferré

, 4 more and

Joan Cerdà

2,346 views

2 citations

Test females (n=14-16 pairs) are displayed on the left (A, C, E) and test males (n=16-23 pairs) are displayed on the right (B, D, F). Mann-Whitney U (A, C), Student’s T (E), One-Way ANOVA (B) and Kruskal Wallis (D, F) tests were performed. Horizontal lines represent mean or median values, boxes represent interquartile ranges, and whiskers represent min-max values. Key to genotypes: A=cyp19a1a, B=cyp19a1b. Asterisks denote p<0.05 (*), p<0.01 (**), p<0.0001 (****).

Original Research

23 June 2023

Mutation of brain aromatase disrupts spawning behavior and reproductive health in female zebrafish

Katherine Shaw

, 3 more and

Vance L. Trudeau

Aromatase (Cyp19a1) is the steroidogenic enzyme that converts androgens into bioactive estrogens, and hence is in a pivotal position to mediate reproduction and sexual behavior. In teleosts, there are two aromatase paralogs: cyp19a1a that is highly expressed in granulosa and Leydig cells in the gonads with critical function in sexual differentiation of the ovary, and cyp19a1b that is highly expressed in radial glial cells in the brain with unknown roles in reproduction. Cyp19a1^-/- mutant zebrafish lines were used to investigate the importance of the cyp19a1 paralogs for spawning behavior and offspring survival and early development. Mutation of cyp19a1b was found to increase the latency to the first oviposition in females. Mutation of cyp19a1b in females also increased the number of eggs spawned; however, significantly more progeny died during early development resulting in no net increase in female fecundity. This finding suggests a higher metabolic cost of reproduction in cyp19a1b^-/- mutant females. In males, the combined mutation of both cyp19a1 paralogs resulted in significantly lower progeny survival rates, indicating a critical function of cyp19a1 during early larval development. These data establish the specific importance of cyp19a1b for female spawning behavior and the importance of the cyp19a1 paralogs for early larval survival.