The importance of the ZBED6-IGF2 axis for metabolic regulation in mouse myoblast cells

Distinct transcriptomic profiles in children prior to the appearance of type 1 diabetes-linked islet autoantibodies and following enterovirus infection

Although the genetic basis and pathogenesis of type 1 diabetes have been studied extensively, how host responses to environmental factors might contribute to autoantibody development remains largely unknown. Here, we use longitudinal blood transcriptome sequencing data to characterize host responses in children within 12 months prior to the appearance of type 1 diabetes-linked islet autoantibodies, as well as matched control children. We report that children who present with insulin-specific autoantibodies first have distinct transcriptional profiles from those who develop GADA autoantibodies first. In particular, gene dosage-driven expression of GSTM1 is associated with GADA autoantibody positivity. Moreover, compared with controls, we observe increased monocyte and decreased B cell proportions 9-12 months prior to autoantibody positivity, especially in children who developed antibodies against insulin first. Lastly, we show that control children present transcriptional signatures consistent with robust immune responses to enterovirus infection, whereas children who later developed islet autoimmunity do not. These findings highlight distinct immune-related transcriptomic differences between case and control children prior to case progression to islet autoimmunity and uncover deficient antiviral response in children who later develop islet autoimmunity.

Single-base editing in IGF2 improves meat production and intramuscular fat deposition in Liang Guang Small Spotted pigs

BACKGROUND

Chinese indigenous pigs are popular with consumers for their juiciness, flavour and meat quality, but they have lower meat production. Insulin-like growth factor 2 (IGF2) is a maternally imprinted growth factor that promotes skeletal muscle growth by regulating cell proliferation and differentiation. A single nucleotide polymorphism (SNP) within intron 3 of porcine IGF2 disrupts a binding site for the repressor, zinc finger BED-type containing 6 (ZBED6), leading to up-regulation of IGF2 and causing major effects on muscle growth, heart size, and backfat thickness. This favorable mutation is common in Western commercial pig populations, but absent in most Chinese indigenous pig breeds. To improve meat production of Chinese indigenous pigs, we used cytosine base editor 3 (CBE3) to introduce IGF2-intron3-C3071T mutation into porcine embryonic fibroblasts (PEFs) isolated from a male Liang Guang Small Spotted pig (LGSS), and single-cell clones harboring the desired mutation were selected for somatic cell nuclear transfer (SCNT) to generate the founder line of IGF2T/T pigs.

RESULTS

We found the heterozygous progeny IGF2C/T pigs exhibited enhanced expression of IGF2, increased lean meat by 18%-36%, enlarged loin muscle area by 3%-17%, improved intramuscular fat (IMF) content by 18%-39%, marbling score by 0.75-1, meat color score by 0.53-1.25, and reduced backfat thickness by 5%-16%. The enhanced accumulation of intramuscular fat in IGF2C/T pigs was identified to be regulated by the PI3K-AKT/AMPK pathway, which activated SREBP1 to promote adipogenesis.

CONCLUSIONS

We demonstrated the introduction of IGF2-intron3-C3071T in Chinese LGSS can improve both meat production and quality, and first identified the regulation of IMF deposition by IGF2 through SREBP1 via the PI3K-AKT/AMPK signaling pathways. Our study provides a further understanding of the biological functions of IGF2 and an example for improving porcine economic traits through precise base editing.

Loss of ZBED6 Protects Against Sepsis-Induced Muscle Atrophy by Upregulating DOCK3-Mediated RAC1/PI3K/AKT Signaling Pathway in Pigs

Sepsis-induced muscle atrophy often increases morbidity and mortality in intensive care unit (ICU) patients, yet neither therapeutic target nor optimal animal model is available for this disease. Here, by modifying the surgical strategy of cecal ligation and puncture (CLP), a novel sepsis pig model is created that for the first time recapitulates the whole course of sepsis in humans. With this model and sepsis patients, increased levels of the transcription factor zinc finger BED-type containing 6 (ZBED6) in skeletal muscle are shown. Protection against sepsis-induced muscle wasting in ZBED6-deficient pigs is further demonstrated. Mechanistically, integrated analysis of RNA-seq and ChIP-seq reveals dedicator of cytokinesis 3 (DOCK3) as the direct target of ZBED6. In septic ZBED6-deficient pigs, DOCK3 expression is increased in skeletal muscle and myocytes, activating the RAC1/PI3K/AKT pathway and protecting against sepsis-induced muscle wasting. Conversely, opposite gene expression patterns and exacerbated muscle wasting are observed in septic ZBED6-overexpressing myotubes. Notably, sepsis patients show increased ZBED6 expression along with reduced DOCK3 and downregulated RAC1/PI3K/AKT pathway. These findings suggest that ZBED6 is a potential therapeutic target for sepsis-induced muscle atrophy, and the established sepsis pig model is a valuable tool for understanding sepsis pathogenesis and developing its therapeutics.

Effect of Zbed6 Single-Allele Knockout on the Growth and Development of Skeletal Muscle in Mice

ZBED6, a key transcription factor, plays an important role in skeletal muscle and organ growth. ZBED6 knockout (ZBED6^-/-) leads to the upregulation of IGF2 in pig and mice muscle, thereby increasing muscle mass. However, the effects and mechanism of Zbed6 single-allele knockout (Zbed6^+/-) on mice muscle remain unknown. Here, we reported that Zbed6^+/- promotes muscle growth by a new potential target gene rather than Igf2 in mice muscle. Zbed6^+/- mice showed markedly higher muscle mass (25%) and a markedly higher muscle weight ratio (18%) than wild-type (WT) mice, coinciding with a larger muscle fiber area (28%). Despite a significant increase in muscle growth, Zbed6^+/- mice showed similar Igf2 expression with WT mice, indicating that a ZBED6-Igf2-independent regulatory pathway exists in Zbed6^+/- mice muscle. RNA-seq of muscle between the Zbed6^+/- and WT mice revealed two terms related to muscle growth. Overlapping the DEGs and C2C12 Chip-seq data of ZBED6 screened out a potential ZBED6 target gene Barx2, which may regulate muscle growth in Zbed6^+/- mice. These results may open new research directions leading to a better understanding of the integral functions of ZBED6 and provide evidence of Zbed6^+/- promoting muscle growth by regulating Barx2 in mice.

Efficient Editing of the ZBED6-Binding Site in Intron 3 of IGF2 in a Bovine Model Using the CRISPR/Cas9 System

Background: Insulin-like growth factor 2 is a growth-promoting factor that plays an important role in the growth and development of mammals. A nucleotide substitution in intron 3 of IGF2—which disrupts the ZBED6-binding site—affects muscle mass, organ size, and fat deposition in pigs. The ZBED6-binding site is also conserved in cattle. Methods: In the present study, we introduced mutations in the ZBED6-binding site in intron3 of IGF2 in bovine fetal fibroblasts using the CRISPR/Cas9 system, and investigated the effect of disruption of ZBED6 binding on IGF2 expression. Results: Eleven biallelic-mutant single-cell clones were established, three of which contained no foreign DNA residues. Single-cell clones 93 and 135 were used to produce cloned embryos. Dual-luciferase reporter assay in C2C12 cells demonstrated that the mutation in the ZBED6-binding site increases the promoter 3 activity of bovine IGF2. A total of 49 mutant cloned embryos were transplanted into surrogate cows. Unfortunately, all cloned embryos died before birth. IGF2 was found to be hypomethylated in the only fetus born (stillborn), which may have been due to the incomplete reprogramming. Conclusions: We efficiently constructed IGF2-edited cell lines and cloned embryos, which provided a theoretical basis and experimental materials for beef cattle breeding.

[Dihydromyricetin reverses Herceptin resistance by up-regulating miR-98-5p and inhibiting IGF1R/HER2 dimer formation in SKBR3 cells]

OBJECTIVE

To explore the effect of dihydromyricetin on the expression of miR-98-5p and its mechanism in the development of Herceptin resistance in SKBR3 cells.

METHODS

The expression of IGF2 and miR-98-5p and their interaction relationship were analyzed by bioinformatics analysis through TargetScan online databases. SKBR3 cells and drug-resistant SKBR3-R cells were cultured in cell experiments. Xenograft tumor mice were constructed by SKBR3 and SKBR3-R cells. Proteins were detected by western blotting and immunohistochemistry. Transfected cells were constructed by shRNA lentivirus vectors. RT-QPCR was used to detect RNA. Cell proliferation was detected by MTS method. Cell jnvasion was detected by Transwell assay. Luciferase reporting assays were used to verify RNA interactions. IGF-1R/HER2 heterodimer was determined by immunocoprecipitation.

RESULTS

The expression of IGF2, p-IGF1R, p-Akt and p-S6K in SKBR3-R cells were significantly higher than those in SKBR3 cells, while the expression of PTEN protein was lower in SKBR3-R cells (P < 0.05). IGF1R/HER2 heterodimer in SKBR3-R cells was significantly increased (P < 0.01).The expression of IGF2 and invasion ability were significantly reduced while transfected with miR-98-5p in SKBR3-R cells (P < 0.05), but the IGF2 mRNA were no difference in both cells (P > 0.05). The expression of miR-98-5p was up-regulated and IGF2 was decreased in drug-resistant xenograft tumor mice after feeding with dihydromyricetin, and the tumor became more sensitivity to Herceptin (P < 0.05).

CONCLUSION

Dihydromyricetin could induce the expression of miR-98-5p, which binds to IGF2 mRNA to reduce IGF2 expression, inhibit the IGF-1R/HER2 formation, thereby reversing cell resistance to Herceptin in SKBR3-R cells.

ZBED6 counteracts high-fat diet-induced glucose intolerance by maintaining beta cell area and reducing excess mitochondrial activation

AIMS/HYPOTHESIS

ZBED6 (zinc finger, BED-type containing 6) is known to regulate muscle mass by suppression of Igf2 gene transcription. In insulin-producing cell lines, ZBED6 maintains proliferative capacity at the expense of differentiation and beta cell function. The aim was to study the impact of Zbed6 knockout on beta cell function and glucose tolerance in C57BL/6 mice.

METHODS

Beta cell area and proliferation were determined in Zbed6 knockout mice using immunohistochemical analysis. Muscle and fat distribution were assessed using micro-computed tomography. Islet gene expression was assessed by RNA sequencing. Effects of a high-fat diet were analysed by glucose tolerance and insulin tolerance tests. ZBED6 was overexpressed in EndoC-βH1 cells and human islet cells using an adenoviral vector. Beta cell cell-cycle analysis, insulin release and mitochondrial function were studied in vitro using propidium iodide staining and flow cytometry, ELISA, the Seahorse technique, and the fluorescent probes JC-1 and MitoSox.

RESULTS

Islets from Zbed6 knockout mice showed lowered expression of the cell cycle gene Pttg1, decreased beta cell proliferation and decreased beta cell area, which occurred independently from ZBED6 effects on Igf2 gene expression. Zbed6 knockout mice, but not wild-type mice, developed glucose intolerance when given a high-fat diet. The high-fat diet Zbed6 knockout islets displayed upregulated expression of oxidative phosphorylation genes and genes associated with beta cell differentiation. In vitro, ZBED6 overexpression resulted in increased EndoC-βH1 cell proliferation and a reduced glucose-stimulated insulin release in human islets. ZBED6 also reduced mitochondrial JC-1 J-aggregate formation, mitochondrial oxygen consumption rates (OCR) and mitochondrial reactive oxygen species (ROS) production, both at basal and palmitate + high glucose-stimulated conditions. ZBED6-induced inhibition of OCR was not rescued by IGF2 addition. ZBED6 reduced levels of the mitochondrial regulator PPAR-γ related coactivator 1 protein (PRC) and bound its promoter/enhancer region. Knockdown of PRC resulted in a lowered OCR.

CONCLUSIONS/INTERPRETATION

It is concluded that ZBED6 is required for normal beta cell replication and also limits excessive beta cell mitochondrial activation in response to an increased functional demand. ZBED6 may act, at least in part, by restricting PRC-mediated mitochondrial activation/ROS production, which may lead to protection against beta cell dysfunction and glucose intolerance in vivo.

ZBED6 regulates Igf2 expression partially through its regulation of miR483 expression

The expression of Igf2 in mammals shows a complex regulation involving multiple promoters and epigenetic mechanisms. We previously identified a novel regulatory mechanism based on the interaction between the transcriptional factor ZBED6 and Igf2 intron. Disruption of the ZBED6-Igf2 interaction leads to a dramatic up-regulation of IGF2 expression postnatally. In the current study we characterize an additional layer of regulation involving miR483 encoded by another Igf2 intron. We found a highly significant up-regulation of miR483 expression when the ZBED6-Igf2 axis is disrupted in transgenic mice. Furthermore, CRISPR/Cas9 mediated knock-out of miR483 in C2C12 myoblast cells, both wild-type and cells with disrupted ZBED6-Igf2 axis (Igf2dGGCT), resulted in down-regulation of Igf2 expression and a reduced proliferation rate. This was further validated using miR483 mimics and inhibitors. RNA-seq analysis revealed a significant enrichment of genes involved in the PI3K-Akt signaling pathway among genes down-regulated in miR483-/- cells, including Igf2 down-regulation. The opposite pattern was observed in Igf2dGGCT cells, where Igf2 is up-regulated. Our data suggest a positive feedback between miR483 and Igf2 promoter activity, strongly affecting how ZBED6 controls Igf2 expression in various cell types.

Knockdown of insulin-like growth factor 2 gene disrupts mitochondrial functions in the liver

Even though insulin-like growth factor 2 (IGF2) has been reported to be overexpressed in nonalcoholic fatty liver disease (NAFLD), its role in the progression of NAFLD and the potential mechanism remain largely unclear. Using in vitro models, we found that IGF2 was the key overexpressed gene in steatosis, suggesting a possible association between IGF2 and NAFLD. Interestingly, loss-of-function experiments revealed that inhibition of IGF2 protein impaired mitochondrial biogenesis and respiration. It additionally disrupted the expression changes of mitochondrial fusion and fission-related proteins necessary in maintaining mitochondrial homeostasis. Consistently, IGF2 knockdown reduced the mitochondrial membrane potential and increased the production of reactive oxygen species. Mechanistically, IGF2 regulates mitochondrial functions by modulating the expression of SIRT1 and its downstream gene PGC1α. This research opens a new frontier on the role of IGF2 in energy metabolism, which potentially participates in the development of NAFLD. As such, IGF2 is a potential therapeutic target against NAFLD.

Liver Expression of IGF2 and Related Proteins in ZBED6 Gene-Edited Pig by RNA-Seq

Simple Summary

Zinc finger BED-type containing 6 (ZBED6), as a regulatory factor, has different regulatory mechanisms in animal development. The intron of insulin-like growth factor 2 (IGF2) regulates the development of animal muscle and adipose by combining with the binding site of ZBED6. As a member of the insulin-like growth factor family, IGF2 plays an important role in embryonic growth and development, cell proliferation, muscle growth and genome imprinting. In order to further study the regulatory mechanism of ZBED6 on IGF2, we detected the expression of IGF2 and related genes in ZBED6 single allele knockout (ZBED6-SKO) pig tissues and analyzed differently expressed genes of the transcriptome of ZBED6-SKO pig liver. The results showed that the partial knockout of ZBED6 could affect the secretion of IGF2 in pig liver but had no significant difference at the protein level. This research provides a new idea for the interaction between IGF2 and ZBED6.

Abstract

Zinc finger BED-type containing 6 (ZBED6), a highly conservative transcription factor of placental mammals, has conservative interaction of insulin-like growth factor 2 (IGF2) based on the 16 bp binding sites of ZBED6 on the IGF2 sequence. IGF2 is related to embryo growth and cell proliferation. At the same time, its functions in muscle and adipose in mammals have been widely mentioned in recent studies. To further investigate the mechanism of ZBED6 on IGF2, we detected the expression of IGF2 and related genes in ZBED6 single allele knockout (ZBED6-SKO) pig tissues and analyzed the transcriptome of ZBED6-SKO pig liver. Through RNA-seq, we captured nine up-regulated genes and eight down-regulated genes which related to lipid metabolism. The results showed that the mRNA of IGF2 had an upward trend after the partial knockout of ZBED6 in liver and had no significant difference in protein expression of IGF2. In summary, ZBED6-SKO could affect the secretion of IGF2 in pig liver and its own lipid metabolism. Our research has provided basic information for revealing the regulatory mechanism of the interaction between ZBED6 and IGF2 in mammals.