摘要: Olfaction, the sense of smell, is vital for the survival of many species and serves as an excellent system for investigating the molecular basis of behavior. Fishes possess a well-developed olfactory system that governs various behaviors related to feeding, reproduction, and fear. However, the cellular diversity and heterogeneity of the fish olfactory epithelium remains largely unexplored. This study presents a single-cell atlas of the zebrafish olfactory epithelium using single-cell RNA sequencing (scRNA-seq). Through scRNA-seq analysis of approximately 10,587 cells, we identified nine distinct cell types with unique transcriptional profiles, including immature and mature olfactory sensory neurons (OSNs), horizontal basal cells, globose basal cells, and sustentacular cells, as well as lymphocyte and myeloid cells expressing immune signals. Further subcluster analysis revealed selective and combinatorial expression of key components in odorant-mediated signal transduction by distinct OSN populations. Additionally, we discovered transcriptional changes specific to certain OSN populations following exposure to a conspecific alarm substance. The single-cell transcriptional atlas of the zebrafish olfactory epithelium provided in this study serves as a valuable tool for exploring cell diversity and assessing genetic profiles from functional and behavioral perspectives in fish.

摘要: Recent cold waves and abrupt seasonal temperature drops have significantly impacted aquaculture, slowing fish growth and causing mass mortality. The intestine plays a crucial role in digestion, nutrient absorption, metabolism, and physiological regulation. However, studies on the molecular mechanisms of fish intestinal response to low-temperature stress and methods to mitigate damage are limited. This study investigated the intestinal response of Danio rerio to low temperatures with three groups: a control group at 28 degrees C (CT28), a cryogenic group at 18 degrees C (ST18), and an extreme cryogenic group at 10 degrees C (LT10), with time points of 0, 12, 24, and 48 h. Results showed significant structural changes in the 18 degrees C group, with inflammatory infiltration starting at 24 h. Damage worsened in the 10 degrees C group, showing severe inflammation. Tunel staining revealed increased cell apoptosis with lower temperatures and longer exposure, peaking at 10 degrees C and 48 h following exposure (p < 0.05). Alcian blue periodic acid-schiff stain revealed that lower temperatures promote an increase in the number of goblet cells. Metabolomics analysis compared intestinal metabolites between CT28 vs. ST18 and CT28 vs. LT10. Fifty-three metabolites were shared between the CT28_ST18 and CT28_LT10 groups in positive ion mode, and 16 in negative mode, with 22 and 9 metabolites showing linear changes. These 31 metabolites could serve as potential indicators for low-temperature stress in D. rerio. Specifically, eight metabolites from the lysophosphatidylcholine (LPC) group increased significantly, while antioxidant alanylglutamine (AGD) decreased. Supplementing the diet with 0.5% AGD reduced intestinal damage, and 1.0% AGD improved low-temperature tolerance. This study provides new insights into the molecular mechanisms of fish response to cold stress and lays the foundation for future research.

摘要: Competing endogenous RNAs (ceRNAs) are a novel epigenetic regulatory mechanism implicated in sex determination and differentiation in teleosts, which exhibit a diversity of sex-determining mechanisms. In this study, based on whole transcriptome sequencing data, a ceRNA regulatory network composed of sex-inclined miRNAs (miR-456), lncRNAs (ASTR), circRNAs (circklhl29), and target mRNAs (spire1 and sox11) was uncovered in the gonadal tissues of Seriola dumerili, an oceanic species with lagged gonadal development. MiRNA-456 was identified as the core of the ceRNA regulatory network and suppressed the expression of spire1 and sox11, interacting with the ncRNAs including circklhl29 and ASTR. Co-localization of these sex-biased ncRNAs and mRNAs in the gonads suggests that this ceRNA network modulated the gonadal differentiation in both sexes of S. dumerili. In vivo injection in the gonads of S. dumerili suggested the miR-456 agonist could significantly inhibit expression of sox11 and spire1 in male testes, while significant regulatory effects of the miR-456 agonist and antagonist on sox11 and spire1 targets were not observed in female ovaries. The conserved binding sites for sequences of miR-456 and spire1/sox11 targets in various fish species were aligned and dual luciferase reporter gene experiments clarified the universality of the mechanism by which miR-456 bound to inhibit sox11/spire1 targets in large yellow croaker (Larimichthys crocea), half-smooth tongue sole (Cynoglossus semilaevis), and zebrafish (Danio rerio). These results further support the notion that ceRNA networks may be a universal regulatory system in teleosts despite their highly divergent sex regulation programs.

摘要: Seahorses are specialized teleosts due to their unique male pregnancy and reproductive physiology. In particular, they have distinct gonad structures and different patterns of gametogenesis development in both sexes. However, the molecular mechanism of germ cell development in seahorses remains unknown. Nanos, which encodes conserved zinc-finger RNA-binding proteins, play essential roles for germline development in both vertebrates and invertebrates. In this study, we characterized the nanos gene family members and their potential roles in germline development in the lined seahorse, Hippocampus erectus. We showed that the nanos family members in the seahorse are the nanos1a, nanos1b, and nanos3 genes, while nanos2, a key germline stem cell (GSC) maintenance factor, is intriguingly absent. More interestingly, nanos3, which is reported to be a female-specific gene, was also highly expressed in male gonads, as well as in the early developmental stages of testes and ovaries. Our results also showed that nanos3 was highly expressed in early meiotic germ cells, and that expression levels of nanos3 were lower in the gonad after TBT exposure. These findings suggest that nanos3 may function during male germ cell development, and in female initial germ cell production - processes which are regulated by nanos2 in other teleosts. This is the first research into how nanos governs germ cell development in an ovoviviparous fish. Our study provides insights into the regulatory mechanisms of germ cells development, as well as the early events during gametogenesis in the family Syngnathidae.

摘要: Contamination by dexamethasone (DEX) in aquatic environments is expected to rise significantly as it is used in the treatment of inflammation, allergies, and autoimmune disorders, especially COVID-19. However, the underlying effects and mechanisms of DEX in leading to metabolic or infectious diseases have remained largely unexplored in teleosts. Here, we used zebrafish (Danio rerio) as a model to study the effects of DEX exposure on metabolic and infectious diseases. We found that DEX-induced hepatobiliary syndrome significantly increased susceptibility to type II grass carp reovirus (GCRV-II), which causes severe hemorrhagic disease in aquaculture. Comparative transcriptomic analysis demonstrated the shared and disease-specific immunometabolic responses among zebrafish larvae with hepatobiliary syndrome and/or GCRV-II infection. Moreover, compared with those of wild-type zebrafish, zebrafish larvae with DEX-induced hepatobiliary syndrome and/or GCRV-II infection presented increased expression of inflammatory markers (il1b), coagulation markers (fibrinogens and antithrombin III), and genes involved in autophagy, including hsp90aa. In vivo inhibition of autophagy via 3-MA and Hsp90 activity via geldanamycin markedly suppressed hepatic lipid deposition and reactive oxygen species accumulation caused by hepatobiliary syndrome and/or GCRV-II infection, thus significantly reducing the severity of disease and level of mortality induced by DEX and/or GCRV-II infection. In conclusion, our findings establish that the inhibition of autophagy and Hsp90 activity are promising therapeutic targets for DEX-induced hepatobiliary syndrome, GCRV-II infection, and DEX-induced hepatobiliary syndrome complicated with GCRV-II infection.