Transcriptomic Profiling Revealed Signaling Pathways Associated with the Spawning of Female Zebrafish under Cold Stress

Functional and Genetic Analyses Unveil the Implication of CDC27 in Hemifacial Microsomia

Hemifacial microsomia (HFM) is a rare congenital genetic syndrome primarily affecting the first and second pharyngeal arches, leading to defects in the mandible, external ear, and middle ear. The pathogenic genes remain largely unidentified. Whole-exome sequencing (WES) was conducted on 12 HFM probands and their unaffected biological parents. Predictive structural analysis of the target gene was conducted using PSIPRED (v3.3) and SWISS-MODEL, while STRING facilitated protein-to-protein interaction predictions. CRISPR/Cas9 was applied for gene knockout in zebrafish. In situ hybridization (ISH) was employed to examine the spatiotemporal expression of the target gene and neural crest cell (NCC) markers. Immunofluorescence with PH3 and TUNEL assays were used to assess cell proliferation and apoptosis. RNA sequencing was performed on mutant and control embryos, with rescue experiments involving target mRNA injections and specific gene knockouts. CDC27 was identified as a novel candidate gene for HFM, with four nonsynonymous de novo variants detected in three unrelated probands. Structural predictions indicated significant alterations in the secondary and tertiary structures of CDC27. cdc27 knockout in zebrafish resulted in craniofacial malformation, spine deformity, and cardiac edema, mirroring typical HFM phenotypes. Abnormalities in somatic cell apoptosis, reduced NCC proliferation in pharyngeal arches, and chondrocyte differentiation issues were observed in cdc27-/- mutants. cdc27 mRNA injections and cdkn1a or tp53 knockout significantly rescued pharyngeal arch cartilage dysplasia, while sox9a mRNA administration partially restored the defective phenotypes. Our findings suggest a functional link between CDC27 and HFM, primarily through the inhibition of CNCC proliferation and disruption of pharyngeal chondrocyte differentiation.

Carbon quantum dot-induced developmental toxicity in Daphnia magna involves disturbance of symbiotic microorganisms

With the increasing synthesis and application of carbon quantum dots (CQDs), their prevalence as pollution in water environments has increased. However, the toxic effects of CQDs on aquatic organisms are unclear, and their environmental safety must be evaluated. Herein, Daphnia magna was used as a model organism to explore the developmental toxicity of CQDs under a full life-cycle exposure. It was found that the feeding rate and offing number of D. magna decreased with increasing CQD concentration, and the body length of D. magna showed a trend of first increasing and then decreasing. These results indicated that long-term exposure to CQDs has evident toxic effects on D. magna development. Symbiosis analysis showed that the composition of the symbiotic microbial community of D. magna was disturbed by CQDs. The abundance of microorganisms involved in the immune response of D. magna such as Rhodobacter, decreased; those involved in the inflammation such as Gemmobacter, increased; and those involved in the nitrogen cycle, such as Hydrogenophaga and Paracoccus, decreased. When D. magna was subjected to environmental pressure, host-microflora interactive immune regulation was induced. The abundance of probiotics in D. magna, such as Rhodococcus, increased in response to environmental pressure. The results of KEGG function prediction showed that the abundance of symbiotic microorganisms involved in energy absorption and metabolism was affected by CQDs. In addition, the correlation analysis showed that there was a correlation between the changes in the symbiotic microbial community and the damage to D. magna after exposure to CQDs. Thus, it is appealed that as a potential environmental pollutant, CQDs have aquatic environmental risks, and their safe application deserves attention.

Acute cold stress leads to zebrafish ovarian dysfunction by regulating miRNA and mRNA

Temperature is a critical factor that regulates the reproduction processes in teleost. However, the gonadal response mechanism to cold stress in fish remains largely unknown. In the present study, female zebrafish were exposed to different extents of low temperatures at 18 °C and 10 °C for 48 h. The ovarian histology was remarkably damaged after cold stress exposure. Integrated analysis of miRNA-mRNA was used to investigate the ovarian response to acute cold stress. A large number of mRNAs and miRNAs were altered by cold stress, which are involved in extensive biological processes. It is indicated that the signal transduction of MAPK and Calcium signaling pathway is highly engaged in zebrafish ovary to adapt to cold stress. The immune system was dysregulated by cold stress while the ovarian autophagy was activated. Remarkably increased gene number related to reproductive functions was identified in the cold stress at 10 °C compared to the control. The cold stress-induced dysregulated reproductive genes include star, hsd3b1, hsd17b1, inha, insl3, amh, nanos1 and foxl2. Combined with the dysregulated insulin, IGF and progesterone signaling, it is suggested that cold stress affects ovarian function in multiple aspects, including oocyte meiosis, folliculogenesis, final maturation and ovarian maintenance. On the other hand, the ovarian miRNA-mRNA regulatory network response to cold stress was also constructed. Overall, our result revealed the ovarian response to cold stress in zebrafish and provided insight into the fish adaptation mechanism to acute temperature change.

Transcriptome Analysis Reveals the Molecular Basis of Overfeeding-Induced Diabetes in Zebrafish

Diabetes has gradually become a serious disease that threatens human health. It can induce various complications, and the pathogenesis of diabetes is quite complex and not yet fully elucidated. The zebrafish has been widely acknowledged as a useful model for investigating the mechanisms underlying the pathogenesis and therapeutic interventions of diabetes. However, the molecular basis of zebrafish diabetes induced by overfeeding remains unknown. In this study, a zebrafish diabetes model was established by overfeeding, and the molecular basis of zebrafish diabetes induced by overfeeding was explored. Compared with the control group, the body length, body weight, and condition factor index of zebrafish increased significantly after four weeks of overfeeding. There was a significant elevation in the fasting blood glucose level, accompanied by a large number of lipid droplets accumulated within the liver. The levels of triglycerides and cholesterol in both the serum and liver exhibited a statistically significant increase. Transcriptome sequencing was employed to investigate changes in the livers of overfed zebrafish. The number of up-regulated and down-regulated differentially expressed genes (DEGs) was 1582 and 2404, respectively, in the livers of overfed zebrafish. The DEGs were subjected to KEGG and GO enrichment analyses, and the hub signaling pathways and hub DEGs were identified. The results demonstrate that sixteen genes within the signal pathway associated with fatty acid metabolism were found to be significantly up-regulated. Specifically, these genes were found to mainly participate in fatty acid transport, fatty acid oxidation, and ketogenesis. Furthermore, thirteen genes that play a crucial role in glucose metabolism, particularly in the pathways of glycolysis and glycogenesis, were significantly down-regulated in the livers of overfed zebrafish. These results indicate insulin resistance and inhibition of glucose entry into liver cells in the livers of overfed zebrafish. These findings elucidate the underlying molecular basis of zebrafish diabetes induced by overfeeding and provide a model for further investigation of the pathogenesis and therapeutics of diabetes.

Molecular Research on Reproductive Toxicity

Fertility rates in animals have shown a progressive decrease in recent decades, and reproductive toxicity is considered an important regulatory endpoint in health hazard assessment [...].

Comparative Transcriptome Analysis Provides Novel Molecular Events for the Differentiation and Maturation of Hepatocytes during the Liver Development of Zebrafish

The liver plays an essential role in multiple biological functions including metabolism, detoxification, digestion, coagulation, and homeostasis in vertebrates. The specification and differentiation of embryonic hepatoblasts, the proliferation of hepatocytes, and the hepatic tissue architecture are well documented, but molecular events governing the maturation of hepatocytes during liver development remain largely unclear. In this study, we performed a comparative transcriptome analysis of hepatocytes that were sorted by flow cytometry from developing zebrafish embryos at 60, 72, and 96 hpf. We identified 667 up-regulated and 3640 down-regulated genes in hepatocytes between 60 and 72 hpf, 606 up-regulated and 3924 down-regulated genes between 60 and 96 hpf, and 1693 up-regulated genes and 1508 down-regulated genes between 72 and 96 hpf. GO enrichment analysis revealed that key biological processes, cellular components, and molecular functions in hepatocytes between 60 to 72 hpf, such as cell cycle, DNA replication, DNA repair, RNA processing, and transcription regulation, are mainly associated with the proliferation of hepatocytes. In addition to biological processes, cellular components, and molecular functions for cell proliferation, molecular functions for carbohydrate metabolism were enriched in hepatocytes during 72 to 96 hpf. KEGG enrichment analysis identified key signaling pathways, such as cell cycle, RNA degradation, ubiquitin-mediated proteolysis, ErbB and Hedgehog signaling, basal transcription factors, Wnt signaling, and glycan degradation, which are closely associated with cell proliferation or carbohydrate metabolism in hepatocytes between 60 to 72 hpf. Newly enriched signaling pathways in hepatocytes during 72 to 96 hpf include metabolisms of pyrimidine, purine, nicotinate and nicotinamide, caffeine, glycine, serine and threonine, ABC transporters, and p53 signaling that function in metabolisms of lipid, protein and energy, cellular secretion, or detoxification, indicating the functional maturation of hepatocytes between 72 to 96 hpf. These findings provide novel clues for further understanding the functional differentiation and maturation of hepatocytes during liver development.