Xiongwei Fan

Abnormal cardiac valve development may lead to functional impairment in adulthood. BMPR2 , a highly conserved receptor of the BMP family, exists in two subtypes ( bmpr2a and bmpr2b ) in zebrafish. However, the roles of bmpr2a and bmpr2b in valve development remain unclear. In this study, we generated three bmpr2a/b mutant zebrafish strains, namely, bmpr2a - and bmpr2b -knockout zebrafish ( bmpr2a ^−/− and bmpr2b ^−/− , respectively) using CRISPR/Cas9 and bmpr2a and bmpr2b double-knockout zebrafish ( bmpr2a ^−/− ;bmpr2b ^−/− ) according to bmpr2a ^−/− and bmpr2b ^−/− hybridization. Using cardiac function assessment (M-mode), we characterized the cardiac developmental phenotypes of the three zebrafish mutant strains. Transcriptomic profiling (RNA-seq) was combined with whole-mount in situ hybridization (WISH) and qRT-PCR to validate gene-expression changes. The results indicated that bmpr2a ^−/− , bmpr2b ^−/− , and bmpr2a ^−/− ;bmpr2b ^−/− mutant zebrafish strains exhibited valve developmental defects at 52 hours post-fertilization (hpf), followed by cardiac contractile dysfunction. RNA-seq revealed upregulation of cardiac markers ( myl9a , myl9b , tnnc1a , cmlc1 , myl7 , and nppa ) and valve-related genes ( fn1b , has2 , and nfatc1 ), along with the downregulation of klf2a , as validated by WISH and qRT-PCR. Pathway analysis identified the ECM-receptor interaction as a key regulatory axis of bmpr2a/b -mediated valve development. In this study, we demonstrate that bmpr2a and bmpr2b cooperatively regulate cardiac contractile function and valve development in zebrafish, providing insights into BMPR2-mediated cardiovascular morphogenesis in humans.

The asb5 gene, a member of the Asb protein subfamily characterized by six ankyrin repeat domains, is highly conserved and comprises two subtypes, asb5a and asb5b, in zebrafish. Our previous research has demonstrated that a deficiency of the asb5 gene significantly impairs early cardiac contractile function, highlighting its close relationship with heart development. Zebrafish asb5 expression was disrupted by both morpholino (MO) antisense oligomer-mediated knockdown and a CRISPR-Cas9 system. A high-throughput RNA-Seq analysis was used to analyze the possible molecular regulatory mechanism of asb5 gene deletion leading to left–right (L-R) asymmetry defects in the heart. Whole-mount in situ hybridization (WISH) was conducted to evaluate gene expression patterns of Nodal signaling components and the positions of heart organs. Heart looping was defective in zebrafish asb5 morphants. Rescue experiments in the asb5-deficiency group (inactivating both asb5a and asb5b) demonstrated that the injection of either asb5a-mRNA or asb5b-mRNA alone was insufficient to rectify the abnormal L-R asymmetry of the heart. In contrast, the simultaneous injection of both asb5a-mRNA and asb5b-mRNA successfully rescued the morphological phenotype. A high-throughput RNA-Seq analysis of embryos at 48 h post fertilization (hpf) revealed that numerous genes associated with L-R asymmetry exhibited expression imbalances in the asb5-deficiency group. WISH further confirmed that the expression of genes such as fli1a, acta1b, hand2, has2, prrx1a, notch1b, and foxa3 were upregulated, while the expression of mei2a and tal1 was downregulated. These results indicated that loss of the asb5 gene in zebrafish led to the disordered development of L-R asymmetry in the heart, resulting in an imbalance in the expression of genes associated with the regulation of L-R asymmetry. Subsequently, we examined the expression patterns of classical Nodal signaling pathway-related genes using WISH. The results showed that the midline barrier factor gene lefty1 was downregulated at early stages in the asb5-deficiency group, and the expression of spaw and lefty2, which are specific to the left lateral plate mesoderm (LPM), was disrupted. This study reveals that the two subtypes of the asb5 gene in zebrafish, asb5a and asb5b, interact and jointly regulate the establishment of early cardiac L-R asymmetry through the Nodal-spaw-lefty signaling pathway.

Identifying the mechanism by which lipid metabolism regulates cancer may offer a novel approach for therapeutic intervention. It has previously been identified that a lipid metabolism‑related factor, namely fatty acid hydroxylase domain containing 2 (FAXDC2), is downregulated in various types of cancer, and inhibits the proliferation and migration of liver cancer cells through a mechanism associated with ERK. The liver is important for lipid metabolism, and FAXDC2 is involved in the synthesis of cholesterol and sphingomyelin. However, the functional mechanism by which FAXDC2 influences liver cancer cells through metabolic processes and ERK signaling remains unclear. Therefore, the present study induced the overexpression of FAXDC2 in HepG2 liver cancer cells and performed a metabolomics analysis. This identified guanosine diphosphate (GDP) as a significantly altered metabolite. Using AlphaFold3, a robust interaction was predicted between FAXDC2 and GDP, which lead to the hypothesis that GDP may mediate the inhibitory effects of FAXDC2 on liver cancer cells by directly modulating the functional properties of the cells, thereby influencing their behavior and progression. Cell Counting Kit‑8 assays were used to study the impact of elevated GDP concentrations on HepG2 cell growth. The results revealed a gradual reduction in the viability of HepG2 cells as the GDP concentration increased. In addition, western blotting showed that GDP treatment was accompanied by a significant downregulation of cyclin dependent kinase 4 and cyclin D1 expression levels, and Transwell experiments revealed that GDP treatment significantly decreased the invasion of HepG2 cells. Treatment with GDP also significantly inhibited the expression of ERK. In summary, the present study is the first to indicate that GDP is a metabolic small molecule with inhibitory activity in cancer cells, which has previously been overlooked in tumor metabolic reprogramming. The study findings offer new insights and strategies for the diagnosis and treatment of liver cancer, and potentially other types of cancer.

Background: General control nonderepressible 5 (Gcn5) is a lysine acetyltransferase (KAT) that is evolutionarily conserved across eukaryotes, with two homologs (Kat2a and Kat2b) identified in humans and one (Gcn5) in Drosophila. Gcn5 contains a P300/CBP-associated factor (PCAF) domain, a Gcn5-N-acetyltransferase (GNAT) domain, and a Bromodomain, allowing it to regulate gene expression through the acetylation of both histone and non-histone proteins. In Drosophila, Gcn5 is crucial for embryonic development, with maternal Gcn5 supporting early development. However, the functional mechanisms of Gcn5 after the depletion of maternal deposits remain unclear. Methods: Our study employed the Gal4/UAS-RNAi system to achieve whole-body or heart-specific Gcn5 knockdown in Drosophila and selected 96-hour-old surviving larvae for transcriptomic and metabolomic analyses. Results: Omics results revealed that Gcn5 knockdown significantly impacts various metabolic pathways, as well as lysosomes, non-homologous end-joining, Toll and Imd signaling pathways, and circadian rhythms, among others. Furthermore, defects in chitin synthesis may be associated with impaired pupation. Additionally, heart-specific Gcn5 knockdown affected cardiac physiology but appeared to have a potential protective effect against age-related cardiac decline. Conclusions: These findings deepen our understanding of Gcn5’s roles in Drosophila development and provide valuable insights for developing Gcn5-targeted therapies, particularly considering its involvement in various human diseases.

The reprogramming of lipid metabolism serves an important role in occurrence and development of liver cancer. Fatty acid hydroxylase domain containing 2 (FAXDC2) is a hydroxylase involved in the synthesis of cholesterol and sphingomyelin and downregulated in various types of cancer. There are no reports on the relationship between FAXDC2 and liver carcinogenesis. The present study used multiple portals and publicly available tools to explore its correlation with liver cancer. The results showed that the expression of FAXDC2 decreased in liver cancer and the methylation level near the promoter increased. Patients with liver cancer and with low expression of FAXDC2 had a poor prognosis. Gain of function and loss of function strategies were performed to evaluate its roles in liver cancer cells. CCK‑8 assay showed that overexpression of FAXDC2 inhibited the viability of liver cancer cells (HepG2). Flow cytometry analysis indicated that HepG2 cells with overexpressing FAXDC2 showed an S phase arrest, associated with cyclin‑dependent kinase 2 decreased. Transwell experiments showed that increasing FAXDC2 inhibited HepG2 cell invasion ability, accompanied by the upregulation of E‑cadherin. Notably, knockdown of FAXDC2 had no significant effect on cell cycle and invasion functions. Based on the cBioPortal platform, FAXDC2 was predicted to closely correlate to the ERK signal in tumorigenesis. Western blotting results showed that overexpression of FAXDC2 decreased the phosphorylation level of ERK in liver cancer cells. The present study first identified FAXDC2 as a liver cancer suppressor, which might inhibit the proliferation and invasion of liver cancer cells through the mechanism associated with ERK signaling. The present study provided a possible new target for the diagnosis and treatment of liver cancer.

Ankyrin repeat and suppression-of-cytokine-signaling box (Asb) proteins, a subset of ubiquitin ligase E3, include Asb5 with six ankyrin-repeat domains. Zebrafish harbor two asb5 gene isoforms, asb5a and asb5b. Currently, the effects of asb5 gene inactivation on zebrafish embryonic development and heart function are unknown. Using CRISPR/Cas9, we generated asb5a-knockout zebrafish, revealing no abnormal phenotypes at 48 h post-fertilization (hpf). In situ hybridization showed similar asb5a and asb5b expression patterns, indicating the functional redundancy of these isoforms. Morpholino interference was used to target asb5b in wild-type and asb5a-knockout zebrafish. Knocking down asb5b in the wild-type had no phenotypic impact, but simultaneous asb5b knockdown in asb5a-knockout homozygotes led to severe pericardial cavity enlargement and atrial dilation. RNA-seq and cluster analyses identified significantly enriched cardiac muscle contraction genes in the double-knockout at 48 hpf. Moreover, semi-automatic heartbeat analysis demonstrated significant changes in various heart function indicators. STRING database/Cytoscape analyses confirmed that 11 cardiac-contraction-related hub genes exhibited disrupted expression, with three modules containing these genes potentially regulating cardiac contractile function through calcium ion channels. This study reveals functional redundancy in asb5a and asb5b, with simultaneous knockout significantly impacting zebrafish early heart development and contraction, providing key insights into asb5’s mechanism.