Hereditary persistence of alpha-fetoprotein and H19 expression in liver of BALB/cJ mice is due to a retrovirus insertion in the Zhx2 gene

A natural loss-of-function deletion of the cytohesin 1 (Cyth1) gene in BALB/cByJ mice does not impact cardiomyocyte polyploidy

Mammalian cardiomyocytes (CMs) mostly become polyploid shortly after birth. Because this feature may relate to several aspects of heart biology, including regeneration after injury, the mechanisms that cause polyploidy are of interest. BALB/cJ and BALB/cByJ mice are highly related sister strains that diverge substantially in CM ploidy. We identified a large deletion in the Cyth1 gene that arose uniquely in BALB/cByJ mice that creates a null allele. The deletion also results in ectopic transcription of the downstream gene Dnah17, although this transcript is unlikely to encode a protein. By evaluating the natural null allele from BALB/cByJ and an engineered knockout allele in the C57BL/6J background, we determined that absence of Cyth1 does not by itself influence CM ploidy. The ready availability of BALB/cByJ mice may be helpful to other investigations of Cyth1 in other biological processes.

"Idiopathic" minimal change nephrotic syndrome: a podocyte mystery nears the end

The discovery of zinc fingers and homeoboxes (ZHX) transcriptional factors and the upregulation of hyposialylated angiopoietin-like 4 (ANGPTL4) in podocytes have been crucial in explaining the cardinal manifestations of human minimal change nephrotic syndrome (MCNS). Recently, uncovered genomic defects upstream of ZHX2 induce a ZHX2 hypomorph state that makes podocytes inherently susceptible to mild cytokine storms resulting from a common cold. In ZHX2 hypomorph podocytes, ZHX proteins are redistributed away from normal transmembrane partners like aminopeptidase A (APA) toward alternative binding partners like IL-4Rα. During disease relapse, high plasma soluble IL-4Rα (sIL-4Rα) associated with chronic atopy complements the cytokine milieu of a common cold to displace ZHX1 from podocyte transmembrane IL-4Rα toward the podocyte nucleus. Nuclear ZHX1 induces severe upregulation of ANGPTL4, resulting in incomplete sialylation of part of the ANGPTL4 protein, secretion of hyposialylated ANGPTL4, and hyposialylation-related injury in the glomerulus. This pattern of injury induces many of the classic manifestations of human minimal change disease (MCD), including massive and selective proteinuria, podocyte foot process effacement, and loss of glomerular basement membrane charge. Administration of glucocorticoids reduces ANGPTL4 upregulation, which reduces hyposialylation injury to improve the clinical phenotype. Improving sialylation of podocyte-secreted ANGPTL4 also reduces proteinuria and improves experimental MCD. Neutralizing circulating TNF-α, IL-6, or sIL-4Rα after the induction of the cytokine storm in Zhx2 hypomorph mice reduces albuminuria, suggesting potential new therapeutic targets for clinical trials to prevent MCD relapse. These studies collectively lay to rest prior suggestions of a role of single cytokines or soluble proteins in triggering MCD relapse.

Elongation of very long chain fatty acids-3 (Elovl3) is activated by ZHX2 and is a regulator of cell cycle progression

Zinc fingers and homeoboxes 2 (Zhx2) are transcriptional regulators of liver gene expression with key functions in embryonic development as well as tissue regeneration in response to damage and disease, presumably through its control of target genes. Previous microarray data suggested that elongation of very long chain fatty acids-3 (Elovl3), a member of the ELOVL family of enzymes that synthesize very long chain fatty acids (VLCFAs), is a putative Zhx2 target gene. VLCFAs are core component of ceramides and other bioactive sphingolipids that are often dysregulated in diseases and regulate key cellular processes including proliferation. Since several previously identified Zhx2 targets become dysregulated in liver damage, we investigated the relationship between Zhx2 and Elovl3 in liver development, damage, and regeneration. Here, using mouse and cell models, we demonstrate that Zhx2 positively regulates Elovl3 expression in the liver and that male-biased hepatic Elovl3 expression is established between 4 and 8 wk of age in mice. Elovl3 is dramatically repressed in mouse models of liver regeneration, and the reduced Elovl3 levels in the regenerating liver are associated with changes in hepatic VLCFAs. Human hepatoma cell lines with forced Elovl3 expression have lower rates of cell growth; analysis of synchronized cells indicates that this reduced proliferation correlates with cells stalling in S-phase and lower mRNA levels of cell cyclins. Taken together, these data indicate that Elovl3 expression helps regulate cellular proliferation during liver development and regeneration, possibly through control of VLCFAs.NEW & NOTEWORTHY Numerous targets of the transcription factor Zhx2 are dysregulated in liver disease. We show that the elongase Elovl3 is a novel Zhx2 target. Elovl3 and Zhx2 expression change during liver regeneration, which is associated with changes in very long chain fatty acids. Forced Elovl3 expression reduces cell growth and blocks cell cycle progression. This suggests that Elovl3 may account, at least in part, for the relationship between Zhx2 and proliferation during liver development and disease.

ZHX2 emerges as a negative regulator of mitochondrial oxidative phosphorylation during acute liver injury

Mitochondria dysfunction contributes to acute liver injuries, and mitochondrial regulators, such as PGC-1α and MCJ, affect liver regeneration. Therefore, identification of mitochondrial modulators may pave the way for developing therapeutic strategies. Here, ZHX2 is identified as a mitochondrial regulator during acute liver injury. ZHX2 both transcriptionally inhibits expression of several mitochondrial electron transport chain genes and decreases PGC-1α stability, leading to reduction of mitochondrial mass and OXPHOS. Loss of Zhx2 promotes liver recovery by increasing mitochondrial OXPHOS in mice with partial hepatectomy or CCl4-induced liver injury, and inhibition of PGC-1α or electron transport chain abolishes these effects. Notably, ZHX2 expression is higher in liver tissues from patients with drug-induced liver injury and is negatively correlated with mitochondrial mass marker TOM20. Delivery of shRNA targeting Zhx2 effectively protects mice from CCl4-induced liver injury. Together, our data clarify ZHX2 as a negative regulator of mitochondrial OXPHOS and a potential target for developing strategies for improving liver recovery after acute injuries.

ZHX2 deficiency enriches hybrid MET cells through regulating E-cadherin expression

Growing evidence indicates that the epithelial to mesenchymal (E/M) hybrid state plays a key role in tumorigenesis. Importantly, a hybrid mesenchymal to epithelial transition (MET) state in which individual cells express both epithelial and mesenchymal markers was recently identified in vivo, further strengthening the bonds between the hybrid EMT state and cancer progression. However, the role and the molecular mechanisms by which the hybrid MET state is maintained in triple-negative breast cancer cells (TNBC) remain elusive. Here, we find that loss of ZHX2 expression results in the hybrid MET phenotype in mesenchymal TNBC cells. Mechanistically, through directly binding to the CDH1 promoter, depletion of ZHX2 specifically reactivates expression of CDH1 encoding E-cadherin, an epithelial marker that is crucial for maintaining epithelial phenotype. Functionally, loss of ZHX2 expression enriches the hybrid MET cells and inhibits the migration and dissemination of TNBC cells or organoids, which could be reversed by restoration of E-cadherin. Moreover, depletion of ZHX2 suppresses lung metastasis in preclinical models of TNBC. In patients with TNBC, ZHX2 expression was amplified and negatively correlated with the expression of E-cadherin. These findings suggest that loss of ZHX2 promotes the hybrid MET state to impair TNBC progression.

Cytokine storm-based mechanisms for extrapulmonary manifestations of SARS-CoV-2 infection

Viral illnesses like SARS-CoV-2 have pathologic effects on nonrespiratory organs in the absence of direct viral infection. We injected mice with cocktails of rodent equivalents of human cytokine storms resulting from SARS-CoV-2/COVID-19 or rhinovirus common cold infection. At low doses, COVID-19 cocktails induced glomerular injury and albuminuria in zinc fingers and homeoboxes 2 (Zhx2) hypomorph and Zhx2+/+ mice to mimic COVID-19-related proteinuria. Common Cold cocktail induced albuminuria selectively in Zhx2 hypomorph mice to model relapse of minimal change disease, which improved after depletion of TNF-α, soluble IL-4Rα, or IL-6. The Zhx2 hypomorph state increased cell membrane to nuclear migration of podocyte ZHX proteins in vivo (both cocktails) and lowered phosphorylated STAT6 activation (COVID-19 cocktail) in vitro. At higher doses, COVID-19 cocktails induced acute heart injury, myocarditis, pericarditis, acute liver injury, acute kidney injury, and high mortality in Zhx2+/+ mice, whereas Zhx2 hypomorph mice were relatively protected, due in part to early, asynchronous activation of STAT5 and STAT6 pathways in these organs. Dual depletion of cytokine combinations of TNF-α with IL-2, IL-13, or IL-4 in Zhx2+/+ mice reduced multiorgan injury and eliminated mortality. Using genome sequencing and CRISPR/Cas9, an insertion upstream of ZHX2 was identified as a cause of the human ZHX2 hypomorph state.

Mitochondrial dysfunction reactivates α-fetoprotein expression that drives copper-dependent immunosuppression in mitochondrial disease models

Signaling circuits crucial to systemic physiology are widespread, yet uncovering their molecular underpinnings remains a barrier to understanding the etiology of many metabolic disorders. Here, we identified a copper-linked signaling circuit activated by disruption of mitochondrial function in the murine liver or heart that resulted in atrophy of the spleen and thymus and caused a peripheral white blood cell deficiency. We demonstrated that the leukopenia was caused by α-fetoprotein, which required copper and the cell surface receptor CCR5 to promote white blood cell death. We further showed that α-fetoprotein expression was upregulated in several cell types upon inhibition of oxidative phosphorylation. Collectively, our data argue that α-fetoprotein may be secreted by bioenergetically stressed tissue to suppress the immune system, an effect that may explain the recurrent or chronic infections that are observed in a subset of mitochondrial diseases or in other disorders with secondary mitochondrial dysfunction.

Zinc fingers and homeoboxes 2 is required for diethylnitrosamine-induced liver tumor formation in C57BL/6 mice

Liver cancer, comprised primarily of hepatocellular carcinoma (HCC), is the third leading cause of cancer deaths worldwide and increasing in Western countries. We previously identified the transcription factor zinc fingers and homeoboxes 2 (Zhx2) as a regulator of hepatic gene expression, and many Zhx2 target genes are dysregulated in HCC. Here, we investigate HCC in Zhx2-deficient mice using the diethylnitrosamine (DEN)-induced liver tumor model. Our study using whole-body Zhx2 knockout (Zhx2KO ) mice revealed the complete absence of liver tumors 9 and 10 months after DEN exposure. Analysis soon after DEN treatment showed no differences in expression of the DEN bioactivating enzyme cytochrome P450 2E1 (CYP2E1) and DNA polymerase delta 2, or in the numbers of phosphorylated histone variant H2AX foci between Zhx2KO and wild-type (Zhx2wt ) mice. The absence of Zhx2, therefore, did not alter DEN bioactivation or DNA damage. Zhx2KO livers showed fewer positive foci for Ki67 staining and reduced interleukin-6 and AKT serine/threonine kinase 2 expression compared with Zhx2wt livers, suggesting that Zhx2 loss reduces liver cell proliferation and may account for reduced tumor formation. Tumors were reduced but not absent in DEN-treated liver-specific Zhx2 knockout mice, suggesting that Zhx2 acts in both hepatocytes and nonparenchymal cells to inhibit tumor formation. Analysis of data from the Cancer Genome Atlas and Clinical Proteomic Tumor Consortium indicated that ZHX2 messenger RNA and protein levels were significantly higher in patients with HCC and associated with clinical pathological parameters. Conclusion: In contrast to previous studies in human hepatoma cell lines and other HCC mouse models showing that Zhx2 acts as a tumor suppressor, our data indicate that Zhx2 acts as an oncogene in the DEN-induced HCC model and is consistent with the higher ZHX2 expression in patients with HCC.

ZHX2 in health and disease

As a transcriptional factor and the negative regulator of alpha fetal protein (AFP), Zinc fingers and homeoboxes 2 (ZHX2) has a well-established role in protection against hepatocellular carcinoma (HCC). However, recent studies have suggested ZHX2 as an oncogene in clear cell renal cell carcinoma (ccRCC) and triple-negative breast cancer (TNBC). Moreover, mounting evidence has illustrated a much broader role of ZHX2 in multiple cellular processes, including cell proliferation, cell differentiation, lipid metabolism, and immunoregulation. This comprehensive review emphasizes the role of ZHX2 in health and diseases which have been more recently uncovered.

Zinc Fingers and Homeobox Family in Cancer: A Double-Edged Sword

The zinc fingers and homeobox (ZHX) family includes ZHX1, ZHX2, and ZHX3, and their proteins have similar unique structures, containing two C2H2-type zinc finger motifs and four or five HOX-like homeodomains. The members of the ZHX family can form homodimers or heterodimers with each other or with a subunit of nuclear factor Y. Previous studies have suggested that ZHXs can function as positive or negative transcriptional regulators. Recent studies have further revealed their biological functions and underlying mechanisms in cancers. This review summarized the advances of ZHX-mediated functions, including tumor-suppressive and oncogenic functions in cancer formation and progression, the molecular mechanisms, and regulatory functions, such as cancer cell proliferation, migration, invasion, and metastasis. Moreover, the differential expression levels and their association with good or poor outcomes in patients with various malignancies and differential responses to chemotherapy exert opposite functions of oncogene or tumor suppressors. Therefore, the ZHXs act as a double-edged sword in cancers.

Zhx2 Is a Candidate Gene Underlying Oxymorphone Metabolite Brain Concentration Associated with State-Dependent Oxycodone Reward

Understanding the pharmacogenomics of opioid metabolism and behavior is vital to therapeutic success, as mutations can dramatically alter therapeutic efficacy and addiction liability. We found robust, sex-dependent BALB/c substrain differences in oxycodone behaviors and whole brain concentration of oxycodone metabolites. BALB/cJ females showed robust state-dependent oxycodone reward learning as measured via conditioned place preference when compared with the closely related BALB/cByJ substrain. Accordingly, BALB/cJ females also showed a robust increase in brain concentration of the inactive metabolite noroxycodone and the active metabolite oxymorphone compared with BALB/cByJ mice. Oxymorphone is a highly potent, full agonist at the mu opioid receptor that could enhance drug-induced interoception and state-dependent oxycodone reward learning. Quantitative trait locus (QTL) mapping in a BALB/c F2 reduced complexity cross revealed one major QTL on chromosome 15 underlying brain oxymorphone concentration that explained 32% of the female variance. BALB/cJ and BALB/cByJ differ by fewer than 10,000 variants, which can greatly facilitate candidate gene/variant identification. Hippocampal and striatal cis-expression QTL (eQTL) and exon-level eQTL analysis identified Zhx2, a candidate gene coding for a transcriptional repressor with a private BALB/cJ retroviral insertion that reduces Zhx2 expression and sex-dependent dysregulation of cytochrome P450 enzymes. Whole brain proteomics corroborated the Zhx2 eQTL and identified upregulated CYP2D11 that could increase brain oxymorphone in BALB/cJ females. To summarize, Zhx2 is a highly promising candidate gene underlying brain oxycodone metabolite levels. Future studies will validate Zhx2 and its site of action using reciprocal gene editing and tissue-specific viral manipulations in BALB/c substrains. SIGNIFICANCE STATEMENT: Our findings show that genetic variation can result in sex-specific alterations in whole brain concentration of a bioactive opioid metabolite after oxycodone administration, reinforcing the need for sex as a biological factor in pharmacogenomic studies. The cooccurrence of female-specific increased oxymorphone and state-dependent reward learning suggests that this minor yet potent and efficacious metabolite of oxycodone could increase opioid interoception and drug-cue associative learning of opioid reward, which has implications for cue-induced relapse of drug-seeking behavior and for precision pharmacogenetics.

ZHX2 inhibits thyroid cancer metastasis through transcriptional inhibition of S100A14

Background

Thyroid cancer is the most common malignant endocrine tumour, and metastasis has become the main reason for treatment failure. However, the underlying molecular mechanism of thyroid cancer metastasis remains poorly understood. We investigated the role of the tumour suppressor zinc fingers and homeoboxes 2 (ZHX2) in the metastasis of thyroid cancer.

Methods

To study the role of ZHX2 in thyroid cancer metastasis, we evaluated the EMT process using cell migration, wound healing and lung metastatic tumour formation in vitro and in vivo models.

Results

ZHX2 expression was significantly decreased in thyroid cancer tissues, which correlated with poor prognosis of thyroid cancer patients. ZHX2 knockdown significantly promoted the migration of thyroid cancer cells. Mechanistically, ZHX2 associated with the S100 calcium binding protein A14 (S100A14) promoter to decrease the transcription of S100A14. Moreover, S100A14 was highly expressed in human thyroid cancer samples, and its expression negatively correlated with ZHX2 expression.

Conclusions

Inhibition of S100A14 attenuated the ZHX2 knockdown-induced enhanced metastasis of thyroid cancer cells both in vitro and in vivo. The evidence presented here suggests that ZHX2 inhibits the progression of thyroid cancer by blocking S100A14-mediated metastasis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02499-w.

Genetic basis of thermal nociceptive sensitivity and brain weight in a BALB/c reduced complexity cross

Thermal nociception involves the transmission of temperature-related noxious information from the periphery to the CNS and is a heritable trait that could predict transition to persistent pain. Rodent forward genetics complement human studies by controlling genetic complexity and environmental factors, analysis of end point tissue, and validation of variants on appropriate genetic backgrounds. Reduced complexity crosses between nearly identical inbred substrains with robust trait differences can greatly facilitate unbiased discovery of novel genes and variants. We found BALB/cByJ mice showed enhanced sensitivity on the 53.5°C hot plate and mechanical stimulation in the von Frey test compared to BALB/cJ mice and replicated decreased gross brain weight in BALB/cByJ versus BALB/cJ. We then identified a quantitative trait locus (QTL) on chromosome 13 for hot plate sensitivity (LOD = 10.7; p < 0.001; peak = 56 Mb) and a QTL for brain weight on chromosome 5 (LOD = 8.7; p < 0.001). Expression QTL mapping of brain tissues identified H2afy (56.07 Mb) as the top transcript with the strongest association at the hot plate locus (FDR = 0.0002) and spliceome analysis identified differential exon usage within H2afy associated with the same locus. Whole brain proteomics further supported decreased H2AFY expression could underlie enhanced hot plate sensitivity, and identified ACADS as a candidate for reduced brain weight. To summarize, a BALB/c reduced complexity cross combined with multiple-omics approaches facilitated identification of candidate genes underlying thermal nociception and brain weight. These substrains provide a powerful, reciprocal platform for future validation of candidate variants.

ZHX2 promotes HIF1α oncogenic signaling in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive and highly lethal disease, which warrants the critical need to identify new therapeutic targets. We show that Zinc Fingers and Homeoboxes 2 (ZHX2) is amplified or overexpressed in TNBC cell lines and patients. Functionally, depletion of ZHX2 inhibited TNBC cell growth and invasion in vitro, orthotopic tumor growth, and spontaneous lung metastasis in vivo. Mechanistically, ZHX2 bound with hypoxia-inducible factor (HIF) family members and positively regulated HIF1α activity in TNBC. Integrated ChIP-seq and gene expression profiling demonstrated that ZHX2 co-occupied with HIF1α on transcriptionally active promoters marked by H3K4me3 and H3K27ac, thereby promoting gene expression. Among the identified ZHX2 and HIF1α coregulated genes, overexpression of AP2B1, COX20, KDM3A, or PTGES3L could partially rescue TNBC cell growth defect by ZHX2 depletion, suggested that these downstream targets contribute to the oncogenic role of ZHX2 in an accumulative fashion. Furthermore, multiple residues (R491, R581, and R674) on ZHX2 are important in regulating its phenotype, which correspond with their roles on controlling ZHX2 transcriptional activity in TNBC cells. These studies establish that ZHX2 activates oncogenic HIF1α signaling, therefore serving as a potential therapeutic target for TNBC.

Patterns of proliferation and cell differentiation during hepatic ontogeny in the alpaca

The liver has multiple functions that change throughout ontogeny. South American camelids (SAC) have unique characteristics related to adaptation to extreme environments and metabolism. However, the process of hepatic cell differentiation has not been studied in any SAC. We study the patterns of cell differentiation and proliferation in the liver of the alpaca at different times of the ontogeny, excluding the hematopoietic components. Immunohistochemical techniques were performed in 66 specimens, including embryos, fetuses, neonates and adults. Supplementary analyses were performed by lectinhistochemistry. The hepatocytic differentiation was performed by the identification of Hepatocyte (Clone: ​​OCH1ES Dako®). It began in the specimens of 1.8-2.5 cm of crown to rump length (CRL), from Days 25-29 (ovulation = Day 0), continued during gestation and intensified towards its end. The cholangiocytic differentiation was performed by the identification of cytokeratin 7 (CK7, Dako®). It was manifested at the final of gestation (specimens of 28.4 cm CRL, from Day 223 onwards). Parenchymal cells underwent a process of gradual differentiation (differentiation of hepatocytes preceded that of cholangiocytes). Cell proliferation was observed along gestation using the nuclear proliferation antigen (PCNA) and Ki-67. Hepatic organogenesis in the alpacas shares similar differentiation and proliferation mechanisms with other altricial, but phylogenetically distant, species.

Upregulation of ZHX2 predicts poor prognosis and is correlated with immune infiltration in gastric cancer

The transcriptional repressor zinc finger homeobox 2 (ZHX2) is reported to regulate tumor progression in several human cancers, although little is known about its role in gastric cancer (GC). In the present study, we investigated the expression of ZHX2 and its relationship with the clinicopathological characteristics and prognosis of GC patients, and we also examined the effect of ZHX2 overexpression in GC cell lines. We used UALCAN (http://ualcan.path.uab.edu) and the Tumor Immune Estimation Resource (http://cistrome.org/TIMER) to examine ZHX2 mRNA expression, and also used Kaplan–Meier Plotter (https://kmplot.com) to determine whether ZHX2 expression was related to GC prognosis. Expression of ZHX2 protein was detected using immunohistochemical staining assays. Cell proliferation was evaluated using a cell counting kit‐8 and colony formation assays, whereas apoptosis was examined by flow cytometry. Wound healing and transwell assays were used to detect cell migration and invasion. We also performed Gene Set Enrichment Analysis (https://www.gsea‐msigdb.org) and used The Cancer Genome Atlas database (https://www.genome.gov/Funded‐Programs‐Projects/Cancer‐Genome‐Atlas) to examine the correlation of ZHX2 with immune infiltration. We report that ZHX2 is highly expressed in GC tissues and is significantly associated with clinical characteristics. Upregulation of ZHX2 predicted poor prognosis in GC. Furthermore, ZHX2 overexpression can promote the proliferation, invasion and migration, but inhibit apoptosis, of GC cells. High expression of ZHX2 in GC is correlated with the presence of infiltrating immune cells, including B cells, CD4⁺ T cells, macrophages and dendritic cells. Our data suggest that high expression of ZHX2 in GC predicts poor prognosis. In addition, ZHX2 may promote malignant behaviors of GC cells, and immune infiltration might be related to the oncogenic role of ZHX2 in GC.

Long noncoding RNA H19 - a new player in the pathogenesis of liver diseases

The liver is a vital organ that controls glucose and lipid metabolism, hormone regulation, and bile secretion. Liver injury can occur from various insults such as viruses, metabolic diseases, and alcohol, which lead to acute and chronic liver diseases. Recent studies have demonstrated the implications of long noncoding RNAs (lncRNAs) in the pathogenesis of liver diseases. These newly discovered lncRNAs have various functions attributing to many cellular biological processes via distinct and diverse mechanisms. LncRNA H19, one of the first lncRNAs being identified, is highly expressed in fetal liver but not in adult normal liver. Its expression, however, is increased in liver diseases with various etiologies. In this review, we focused on the roles of H19 in the pathogenesis of liver diseases. This comprehensive review is aimed to provide useful perspectives and translational applications of H19 as a potential therapeutic target of liver diseases.

Regulation of Fetal Genes by Transitions among RNA-Binding Proteins during Liver Development

Transcripts of alpha-fetoprotein (Afp), H19, and insulin-like growth factor 2 (Igf2) genes are highly expressed in mouse fetal liver, but decrease drastically during maturation. While transcriptional regulation of these genes has been well studied, the post-transcriptional regulation of their developmental decrease is poorly understood. Here, we show that shortening of poly(A) tails and subsequent RNA decay are largely responsible for the postnatal decrease of Afp, H19, and Igf2 transcripts in mouse liver. IGF2 mRNA binding protein 1 (IMP1), which regulates stability and translation efficiency of target mRNAs, binds to these fetal liver transcripts. When IMP1 is exogenously expressed in mouse adult liver, fetal liver transcripts show higher expression and possess longer poly(A) tails, suggesting that IMP1 stabilizes them. IMP1 declines concomitantly with fetal liver transcripts as liver matures. Instead, RNA-binding proteins (RBPs) that promote RNA decay, such as cold shock domain containing protein E1 (CSDE1), K-homology domain splicing regulatory protein (KSRP), and CUG-BP1 and ETR3-like factors 1 (CELF1), bind to 3' regions of fetal liver transcripts. These data suggest that transitions among RBPs associated with fetal liver transcripts shift regulation from stabilization to decay, leading to a postnatal decrease in those fetal transcripts.

Functional long non-coding RNAs in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a prevalent human malignancy with high morbidity worldwide. Hepatocarcinogenesis is a complex multistep process, and its underlying molecular mechanisms remain largely unknown. Recently, long non-coding RNAs (lncRNAs), a class of newly discovered molecules, have been revealed as essential regulators in the development of HCC. HCC-associated lncRNAs affect multiple malignant phenotypes by modulating gene expression or protein activity. Moreover, the dysregulation of lncRNAs in the liver is also associated with diseases predisposing to HCC, such as chronic viral infection, nonalcoholic steatohepatitis, and liver fibrosis/cirrhosis. A deeper understanding of the lncRNA regulatory network in the multistep processes of HCC development will provide new insights into the diagnosis and treatment of HCC. In this review, we introduce the biogenesis and function of lncRNAs and summarize recent knowledge on how lncRNAs regulate the malignant hallmarks of HCC, such as uncontrolled cell proliferation, resistance to cell death, metabolic reprogramming, immune escape, angiogenesis, and metastasis. We also review emerging insights into the role of lncRNAs in HCC-associated liver diseases. Finally, we discuss the potential applications of lncRNAs as early diagnostic biomarkers and therapeutic targets.

ZHX2 inhibits SREBP1c-mediated de novo lipogenesis in hepatocellular carcinoma via miR-24-3p

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. Lipogenesis has been considered as a critical player in HCC initiation and progression. However, the underlying mechanism is still not fully understood. Here, we identified zinc fingers and homeoboxes 2 (ZHX2), an HCC-associated tumor suppressor, as an important repressor of de novo lipogenesis. Ectopic expression of ZHX2 significantly inhibited de novo lipogenesis in HCC cells and decreased expression of FASN, ACL, ACC1, and SCD1. In accordance with this, ZHX2 was negatively associated with SREBP1c, the master regulator of de novo lipogenesis, in HCC cell lines and human specimens. Results from silencing and overexpression demonstrated that ZHX2 inhibited de novo lipogenesis and consequent HCC progression via repression of SREBP1c. Furthermore, treatment with the SREBP1c inhibitor fatostatin dampened the spontaneous formation of tumors in liver-specific Zhx2 knockout mice. Mechanistically, ZHX2 increased expression of miR-24-3p transcriptionally, which targeted SREBP1c and led to its degradation. In conclusion, our data suggest a novel mechanism through which ZHX2 suppresses HCC progression, which may provide a new strategy for the treatment of HCC. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Impact of mouse strain and sex when modeling radiation necrosis

Background

Murine models are among the most common type of preclinical animal models used to study the human condition, but a wide selection of different mice is currently in use with these differences potentially compromising study results and impairing the ability to reconcile interstudy results. Our goal was to determine how the strain and sex of the mice selection would affect the development of radiation necrosis in our murine model of radiation-induced cerebral necrosis.

Methods

We generated this model by using a preclinical irradiator to irradiate a sub-hemispheric portion of the brain of mice with single-fraction doses of 80 Gy. Eight possible combinations of mice made up of two different with two substrains each (BALB/cN, BALB/cJ, C57BL/6 N, and C57BL/6 J) and both sexes were irradiated in this study. Radiation necrosis development was tracked up to 8 weeks with a 7 T Bruker MRI utilizing T2-weighted and post-contrast T1-weighted imaging. MRI results were compared to and validated with the use of histology which utilized a scale from 0 to 3 in ascending order of damage.

Results

Both time post-irradiation and strain (BALB/c vs C57BL/6) were significant factors affecting radiation necrosis development. Sex was in general not a statistically significant parameter in terms of radiation necrosis development.

Conclusion

Mouse strain thus needs to be considered when evaluating the results of necrosis models. However, sex does not appear to be a variable needing major consideration.

Evolutionary Analysis of the Zinc Finger and Homeoboxes Family of Proteins Identifies Multiple Conserved Domains and a Common Early Chordate Ancestor

The Zinc Fingers and Homeoboxes (Zhx) proteins, Zhx1, Zhx2, and Zhx3, comprise a small family of proteins containing two amino-terminal C₂–H₂ zinc fingers and four or five carboxy-terminal homeodomains. These multiple homeodomains make Zhx proteins unusual because the majority of homeodomain-containing proteins contain a single homeodomain. Studies in cultured cells and mice suggest that Zhx proteins can function as positive or negative transcriptional regulators. Zhx2 regulates numerous hepatic genes, and all three Zhx proteins have been implicated in different cancers. Because Zhx proteins contain multiple predicted homeodomains, are associated with interesting physiological traits, and seem to be only present in the vertebrate lineage, we investigated the evolutionary history of this small family by comparing Zhx homologs from a wide range of chordates. This analysis indicates that the zinc finger motifs and homeodomains are highly similar among all Zhx proteins and also identifies additional Zhx-specific conserved regions, including a 13 amino acid amino-terminal motif that is nearly identical among all gnathostome Zhx proteins. We found single Zhx proteins in the sea lamprey (Petromyzon marinus) and in the nonvertebrate chordates sea squirt (Ciona intestinalis) and lancelet (Branchiostoma floridae); these Zhx proteins are most similar to gnathostome Zhx3. Based on our analyses, we propose that a duplication of the primordial Zhx gene gave rise to Zhx3 and the precursor to Zhx1 and Zhx2. A subsequent tandem duplication of this precursor generated Zhx1 and Zhx2 found in gnathostomes.

ZHX2 restricts hepatocellular carcinoma by suppressing stem cell-like traits through KDM2A-mediated H3K36 demethylation

Background

Liver cancer stem cells (CSCs) are critical determinants of HCC relapse and therapeutic resistance, but the mechanisms underlying the maintenance of CSCs are poorly understood. We aimed to explore the role of tumor repressor Zinc-fingers and homeoboxes 2 (ZHX2) in liver CSCs.

Methods

CD133⁺ or EPCAM⁺ stem-like liver cancer cells were sorted from tumor tissues of HCC patients and HCC cell lines by flow cytometry. In addition, sorafenib-resistant cells, tumor-sphere forming cells and side population (SP) cells were respectively cultured and isolated as hepatic CSCs. The tumor-initiating and chemoresistance properties of ZHX2-overexpressing and ZHX2-knockdown cells were analyzed in vivo and in vitro. Microarray, luciferase reporter assay, chromatin immunoprecipitation (ChIP) and ChIP-on-chip analyses were performed to explore ZHX2 target genes. The expression of ZHX2 and its target gene were determined by quantitative RT-PCR, western blot, immunofluorescence and immunohistochemical staining in hepatoma cells and tumor and adjacent tissues from HCC patients.

Results

ZHX2 expression was significantly reduced in liver CSCs from different origins. ZHX2 deficiency led to enhanced liver tumor progression and expansion of CSC populations in vitro and in vivo. Re-expression of ZHX2 restricted capabilities of hepatic CSCs in supporting tumor initiation, self-renewal and sorafenib-resistance. Mechanically, ZHX2 suppressed liver CSCs via inhibiting KDM2A-mediated demethylation of histone H3 lysine 36 (H3K36) at the promoter regions of stemness-associated transcription factors, such as NANOG, SOX4 and OCT4. Moreover, patients with lower expression of ZHX2 and higher expression of KDM2A in tumor tissues showed significantly poorer survival.

Conclusion

ZHX2 counteracts stem cell traits through transcriptionally repressing KDM2A in HCC. Our data will aid in a better understanding of molecular mechanisms underlying HCC relapse and drug resistance.

The zinc fingers and homeoboxes 2 protein ZHX2 and its interacting proteins regulate upstream pathways in podocyte diseases

Zinc fingers and homeoboxes (ZHX) proteins are heterodimeric transcriptional factors largely expressed at the cell membrane in podocytes in vivo. We found ZHX2-based heterodimers in podocytes, with ZHX2-ZHX1 predominantly at the cell membrane of the podocyte cell body, and ZHX2-ZHX3 at the slit diaphragm. In addition to changes in overall ZHX2 expression, there was increased podocyte nuclear ZHX3 and ZHX2 in patients with focal segmental glomerulosclerosis, and increased podocyte nuclear ZHX1 in patients with minimal change disease. Zhx2 deficient mice had increased podocyte ZHX1 and ZHX3 expression. Zhx2 deficient mice and podocyte specific Zhx2 overexpressing transgenic rats develop worse experimental focal segmental glomerulosclerosis than controls, with increased nuclear ZHX3 and ZHX2, respectively. By contrast, podocyte specific Zhx2 overexpressing transgenic rats develop lesser proteinuria during experimental minimal change disease due to peripheral sequestration of ZHX1 by ZHX2. Using co-immunoprecipitation, the interaction of ZHX2 with aminopeptidase A in the podocyte body cell membrane, and EPHRIN B1 in the slit diaphragm were noted to be central to upstream events in animal models of minimal change disease and focal segmental glomerulosclerosis, respectively. Mice deficient in Enpep, the gene for aminopeptidase A, and Efnb1, the gene for ephrin B1 developed worse albuminuria in glomerular disease models. Targeting aminopeptidase A in Zhx2 deficient mice with monoclonal antibodies induced albuminuria and upregulation of the minimal change disease mediator angiopoietin-like 4 through nuclear entry of ZHX1. Thus, podocyte ZHX2 imbalance is a critical factor in human glomerular disease, with minimal change disease disparities mediated mostly through ZHX1, and focal segmental glomerulosclerosis deviations through ZHX3 and ZHX2.

Tumor suppressor ZHX2 inhibits NAFLD-HCC progression via blocking LPL-mediated lipid uptake

Non-alcoholic fatty liver disease (NAFLD) leads to hepatocellular carcinoma (HCC). However, the underlying mechanism remains largely unclear. Here, we investigated the role of the tumor suppressor Zinc fingers and homeoboxes 2 (ZHX2) in the progression of NAFLD to HCC. ZHX2 expression was significantly decreased in fatty liver tissues, especially in the liver with NAFLD–HCC. ZHX2 overexpression disturbed lipid homeostasis of cultured HCC cells, and inhibited lipid deposition in hepatocytes both in vitro and in vivo. Moreover, ZHX2 inhibited uptake of exogenous lipids through transcriptional suppression of lipid lipase (LPL), leading to retarded proliferation of HCC cells. Importantly, LPL overexpression significantly reversed ZHX2-mediated inhibition of HCC cell proliferation, xenograft tumor growth, lipid deposition, and spontaneous liver tumor formation. Consistently, IHC staining demonstrated a negative correlation of ZHX2 with LPL in an HCC cohort. Collectively, ZHX2 protects hepatocytes from abnormal lipid deposition in NAFLD through transcriptional repression of LPL, which subsequently retards cell growth and NAFLD–HCC progression. These findings illustrate a novel mechanism of NAFLD progression into HCC.

Liver size and lipid content differences between BALB/c and BALB/cJ mice on a high-fat diet are due, in part, to Zhx2

BALB/cJ mice exhibit considerable phenotypic differences with other BALB/c substrains. Some of these traits involve the liver, including persistent postnatal expression of genes that are normally expressed only in the fetal liver and reduced expression of major urinary proteins. These traits are due to a mutation that dramatically reduces expression of the gene encoding the transcription factor Zinc fingers and homeoboxes 2 (Zhx2). BALB/cJ mice also exhibit reduced serum lipid levels and resistance to atherosclerosis compared to other mouse strains when placed on a high-fat diet. This trait is also due, at least in part, to the Zhx2 mutation. Microarray analysis identified many genes affecting lipid homeostasis, including Lipoprotein lipase, that are dysregulated in BALB/cJ liver. This led us to investigate whether hepatic lipid levels would be different between BALB/cJ and BALB/c mice when placed on a normal chow or a high-fat chow diet. On the high-fat chow, BALB/cJ mice had increased weight gain, increased liver:body weight ratio, elevated hepatic lipid accumulation and markers of liver damage when compared to BALB/c mice. These traits in BALB/cJ mice were only partially reversed by a hepatocyte-specific Zhx2 transgene. These data indicate that Zhx2 reduces liver lipid levels and is hepatoprotective in mice on a high-fat diet, but the partial rescue by the Zhx2 transgene suggests a contribution by both parenchymal and non-parenchymal cells. A model to account for the cardiovascular and liver phenotype in mice with reduced Zhx2 levels is provided.

Polycomb Repressive Complex 2 Proteins EZH1 and EZH2 Regulate Timing of Postnatal Hepatocyte Maturation and Fibrosis by Repressing Genes With Euchromatic Promoters in Mice

BACKGROUND & AIMS

Little is known about mechanisms that underlie postnatal hepatocyte maturation and fibrosis at the chromatin level. We investigated the transcription of genes involved in maturation and fibrosis in postnatal hepatocytes of mice, focusing on the chromatin compaction the roles of the Polycomb repressive complex 2 histone methyltransferases EZH1 and EZH2.

METHODS

Hepatocytes were isolated from mixed background C57BL/6J-C3H mice, as well as mice with liver-specific disruption of Ezh1 and/or Ezh2, at postnatal day 14 and 2 months after birth. Liver tissues were collected and analyzed by RNA sequencing, H3K27me3 chromatin immunoprecipitation sequencing, and sonication-resistant heterochromatin sequencing (a method to map heterochromatin and euchromatin). Liver damage was characterized by histologic analysis.

RESULTS

We found more than 3000 genes differentially expressed in hepatocytes during liver maturation from postnatal day 14 to month 2 after birth. Disruption of Ezh1 and Ezh2 in livers caused perinatal hepatocytes to differentiate prematurely and to express genes at postnatal day 14 that would normally be induced by month 2 and differentiate prematurely. Loss of Ezh1 and Ezh2 also resulted in liver fibrosis. Genes with H3K27me3-postive and H3K4me3-positive euchromatic promoters were prematurely induced in hepatocytes with loss of Ezh1 and Ezh2-these genes included those that regulate hepatocyte maturation, fibrosis, and genes not specifically associated with the liver lineage.

CONCLUSIONS

The Polycomb repressive complex 2 proteins EZH1 and EZH2 regulate genes that control hepatocyte maturation and fibrogenesis and genes not specifically associated with the liver lineage by acting at euchromatic promoter regions. EZH1 and EZH2 thereby promote liver homeostasis and prevent liver damage. Strategies to manipulate Polycomb proteins might be used to improve hepatocyte derivation protocols or developed for treatment of patients with liver fibrosis.

Retrotransposon elements among initial sites of hepatitis B virus integration into human genome in the HepG2-NTCP cell infection model

Integration of hepatitis B virus (HBV) DNA into host's genome is evident in all stages and models of HBV infection. Investigations of the initial virus-host junctions have been just recently initiated since their nature may promote liver oncogenesis immediately following infection. We examined the time-frame and host sites at which HBV integrates in HepG2 cells overexpressing sodium taurocholate co-transporting polypeptide (NTCP) receptor mediating HBV entry. HepG2-NTCP cells were analyzed from 15 min to 13 days post-infection (p.i.). The results showed that except for 15 min p.i., HBV-host integrations were detected at all time points thereafter. At 30 min p.i., virus junctions with retrotransposon SINE and with neuroblastoma breakpoint family member 1 gene were detected. At one-hour p.i., HBV integration with retrotransposon THE-1B-LTR was identified, while virus insertions into proline-rich protein and protein kinase cGMP-dependent type 1 encoding genes were found at 3 h p.i. Fusion with runt-related transcription factor 1 was detected at 24 h p.i. and merges with 9 different genes at 13 day p.i. The data showed that retrotransposon elements are frequent among first-hit sites of HBV insertion. This may suggest a mechanism by which HBV DNA may spread across host's genome from earliest stages of infection.

Mouse germ line mutations due to retrotransposon insertions

Transposable element (TE) insertions are responsible for a significant fraction of spontaneous germ line mutations reported in inbred mouse strains. This major contribution of TEs to the mutational landscape in mouse contrasts with the situation in human, where their relative contribution as germ line insertional mutagens is much lower. In this focussed review, we provide comprehensive lists of TE-induced mouse mutations, discuss the different TE types involved in these insertional mutations and elaborate on particularly interesting cases. We also discuss differences and similarities between the mutational role of TEs in mice and humans.

HBV suppresses ZHX2 expression to promote proliferation of HCC through miR-155 activation

Initiation of hepatocellular carcinoma (HCC) by chronic hepatitis B virus (HBV) infection is a complex process that includes both oncogene activation and tumor suppressor inhibition. The HBV X (HBx) protein has an important and complex role in processes leading to HCC. We previously identified the mammalian Zinc fingers and homeoboxes 2 (ZHX2) gene as an HCC-associated tumor suppressor gene. In the present study, we investigated whether the oncogenic properties of HBV and, more specifically, HBx, involved ZHX2 silencing. Our data indicates that ZHX2 expression is significantly decreased in tumor tissues from HBV-positive HCC patients and livers from HBV transgenic mice. In vitro and in vivo studies confirmed that HBV-encoded proteins, particularly HBx, inhibits both the expression and tumor suppression properties of ZHX2. Further analyses identified miR-155, a well-known oncomiR in various cancers, as an important link between HBx and ZHX2 inhibition. Increased miR-155 levels were found in HBV-positive tumors, livers of HBV transgenic mice and HBx-overexpressing hepatoma cell lines. MiR-155 overexpression reduced ZHX2 levels via miR-155 seed sites in the ZHX2 3'UTR, whereas blocking miR-155 levels led to increased ZHX2 levels. Taken together, our data indicate that HCC-promoting properties of HBV may include ZHX2 silencing via a miR-155 dependent pathway and suggests a novel therapy for HBV-related HCC.

The role of Zhx2 transcription factor in bipolar cell differentiation during mouse retinal development

We found that the Zhx2 gene (whose product is known to act as a tumor suppressor in hepatocellular carcinoma) is expressed in embryonic retinal progenitors and in developing cone bipolar cells in the postnatal retina, as well as in Müller glia in the mature retina. To examine the functions of Zhx2 protein during retinal development, we performed loss- and gain-of-function analyses using a retinal explant culture system. We introduced a plasmid encoding Zhx2 shRNA into isolated mouse retinas at E17.5, and the retinas were cultured as explants. After 3 days of culture, proliferation was slightly enhanced, leading to retinas thicker than in the control, but this phenomenon was observed only transiently. After 14 days of the culture, the thickness and gross morphology of retinas expressing sh-Zhx2 were indistinguishable from those of the control. The numbers of rod cells, amacrine cells, and Müller glia were the same in both groups. However, although the total number of bipolar cells was the same, the experimental group saw an increased population of ON bipolar cells, and decreased numbers of a subset of OFF bipolar cells. We also examined the effects of overexpression of Zhx2. Although Zhx2 acts as a tumor suppressor, its overexpression in developing retinas did not lead to any discernible difference in retinal thickness, suggesting that proliferation activity was not affected. After 14 days of explant culture, the total number of bipolar cells decreased, and subset composition was altered. Taken together, these results suggest that Zhx2 plays roles in the regulation of bipolar cell subset fate determination during retinal development.

Transcription Factor Zhx2 Deficiency Reduces Atherosclerosis and Promotes Macrophage Apoptosis in Mice

Objective- The objective of this study was to determine the basis of resistance to atherosclerosis of inbred mouse strain BALB/cJ. Approach and Results- BALB/cJ mice carry a naturally occurring null mutation of the gene encoding the transcription factor Zhx2, and genetic analyses suggested that this may confer resistance to atherosclerosis. On a hyperlipidemic low-density lipoprotein receptor null background, BALB/cJ mice carrying the mutant allele for Zhx2 exhibited up to a 10-fold reduction in lesion size as compared with an isogenic strain carrying the wild-type allele. Several lines of evidence, including bone marrow transplantation studies, indicate that this effect of Zhx2 is mediated, in part, by monocytes/macrophages although nonbone marrow-derived pathways are clearly involved as well. Both in culture and in atherosclerotic lesions, macrophages from Zhx2 null mice exhibited substantially increased apoptosis. Zhx2 null macrophages were also enriched for M2 markers. Effects of Zhx2 on proliferation and other bone marrow-derived cells, such as lymphocytes, were at most modest. Expression microarray analyses identified >1000 differentially expressed transcripts between Zhx2 wild-type and null macrophages. To identify the global targets of Zhx2, we performed ChIP-seq (chromatin immunoprecipitation sequencing) studies with the macrophage cell line RAW264.7. The ChIP-seq peaks overlapped significantly with gene expression and together suggested roles for transcriptional repression and apoptosis. Conclusions- A mutation of Zhx2 carried in BALB/cJ mice is responsible in large part for its relative resistance to atherosclerosis. Our results indicate that Zhx2 promotes macrophage survival and proinflammatory functions in atherosclerotic lesions, thereby contributing to lesion growth.

CRL4DCAF8 Ubiquitin Ligase Targets Histone H3K79 and Promotes H3K9 Methylation in the Liver

Transcription from chromosomes is regulated by posttranslational modifications to histones, such as methylation and ubiquitination. Monoubiquitination of histones H2A and H2B influences H3 methylation to reinforce the activation or repression of gene expression. Here, we provide evidence that H3 polyubiquitination represses transcription of fetal and cell-cycle genes in postnatal mouse liver by crosstalk with H3K9 methylation. We found that the CRL4 ubiquitin ligase targets H3 for polyubiquitination at K79 via the DCAF8 substrate receptor in hepatocytes. Genetic inactivation of DCAF8 and overexpression of an H3K79 mutant in cells or inducible deletion of CRL4 in mouse liver abrogates H3 ubiquitination, reactivates the expression of fetal liver and cell-cycle genes by interfering with methylated H3K9 occupancy, and leads to cell senescence. Restoring CRL4^DCAF8 expression in cells with decreased H3 ubiquitination reinstates the epigenetic gene silencing. Our results suggest that progressive H3 ubiquitination plays an important role in postnatal liver maturation.

Alpha-Fetoprotein: From a Diagnostic Biomarker to a Key Role in Female Fertility

Alpha-fetoprotein (AFP) is a well-known diagnostic biomarker used in medicine to detect fetal developmental anomalies such as neural tube defects or Down's syndrome, or to follow up the development of tumors such as hepatocellular carcinomas. However, and despite the fact that the protein was discovered almost half a century ago, little was known about its physiological function. The study of Afp knock-out mice uncovered a surprising function of AFP: it is essential for female fertility and for expression of normal female behaviors, and this action is mediated through its estrogen binding capacity. AFP sequestrates estrogens and by so doing protects the female developing brain from deleterious (defeminizing/masculinizing) effects of these hormones.

Long Non-coding RNA in Liver Metabolism and Disease: Current Status

Long non-coding RNAs (lncRNAs) are comprised of RNA transcripts exceeding 200 nucleotides in length but lacking identifiable open reading frames (with rare exceptions). Herein, we highlight emerging evidence demonstrating that lncRNAs are critical regulators of liver metabolic function and diseases. We summarize current knowledges about dysregulated lncRNAs and outline the underlying molecular mechanisms by which lncRNAs control hepatic lipid ad glucose metabolism, as well as cholestatic liver disease. lncLSTR, Lnc18q22.2, SRA, HULC, MALAT1, lncLGR, MEG3, and H19, lncHR1, lnc-HC, APOA1-AS, DYNLRB2-2, and LeXis are included in the discussion.

Targeting H19, an Imprinted Long Non-Coding RNA, in Hepatic Functions and Liver Diseases

H19 is a long non-coding RNA regulated by genomic imprinting through methylation at the locus between H19 and IGF2. H19 is important in normal liver development, controlling proliferation and impacting genes involved in an important network controlling fetal development. H19 also plays a major role in disease progression, particularly in hepatocellular carcinoma. H19 participates in the epigenetic regulation of many processes impacting diseases, such as activating the miR-200 pathway by histone acetylation to inhibit the epithelial-mesenchymal transition to suppress tumor metastasis. Furthermore, H19's normal regulation is disturbed in diseases, such as hepatocellular carcinoma. In this disease, aberrant epigenetic maintenance results in biallelic expression of IGF2, leading to uncontrolled cellular proliferation. This review aims to further research utilizing H19 for drug discovery and the treatment of liver diseases by focusing on both the epigenetic regulation of H19 and how H19 regulates normal liver functions and diseases, particularly by epigenetic mechanisms.

Zhx2 (zinc fingers and homeoboxes 2) regulates major urinary protein gene expression in the mouse liver

The mouse major urinary proteins (Mups) are encoded by a large family of highly related genes clustered on chromosome 4. Mups, synthesized primarily and abundantly in the liver and secreted through the kidneys, exhibit male-biased expression. Mups bind a variety of volatile ligands; these ligands, and Mup proteins themselves, influence numerous behavioral traits. Although urinary Mup protein levels vary between inbred mouse strains, this difference is most pronounced in BALB/cJ mice, which have dramatically low urinary Mup levels; this BALB/cJ trait had been mapped to a locus on chromosome 15. We previously identified Zhx2 (zinc fingers and homeoboxes 2) as a regulator of numerous liver-enriched genes. Zhx2 is located on chromosome 15, and a natural hypomorphic mutation in the BALB/cJ Zhx2 allele dramatically reduces Zhx2 expression. Based on these data, we hypothesized that reduced Zhx2 levels are responsible for lower Mup expression in BALB/cJ mice. Using both transgenic and knock-out mice along with in vitro assays, our data show that Zhx2 binds Mup promoters and is required for high levels of Mup expression in the adult liver. In contrast to previously identified Zhx2 targets that appear to be repressed by Zhx2, Mup genes are positively regulated by Zhx2. These data identify Zhx2 as a novel regulator of Mup expression and indicate that Zhx2 activates as well as represses expression of target genes.

Expression kinetics of hepatic progenitor markers in cellular models of human liver development recapitulating hepatocyte and biliary cell fate commitment

Due to the limitations of research using human embryos and the lack of a biological model of human liver development, the roles of the various markers associated with liver stem or progenitor cell potential in humans are largely speculative, and based on studies utilizing animal models and certain patient tissues. Human pluripotent stem cell-based in vitro multistage hepatic differentiation systems may serve as good surrogate models for mimicking normal human liver development, pathogenesis and injury/regeneration studies. Here, we describe the implications of various liver stem or progenitor cell markers and their bipotency (i.e. hepatocytic- and biliary-epithelial cell differentiation), based on the pluripotent stem cell-derived model of human liver development. Future studies using the human cellular model(s) of liver and biliary development will provide more human relevant biological and/or pathological roles of distinct markers expressed in heterogeneous liver stem/progenitor cell populations.

Clinicopathologic and immunohistochemical characteristics of gastric adenocarcinoma with enteroblastic differentiation: a study of 29 cases

BACKGROUND

Gastric adenocarcinoma with enteroblastic differentiation (GAED) has been recognized as a variant of alpha-fetoprotein (AFP)-producing gastric carcinoma, although its clinicopathologic and immunohistochemical features have not been fully elucidated.

METHODS

To elucidate the clinicopathologic and immunohistochemical features of GAED, we analyzed 29 cases of GAED, including ten early and 19 advanced lesions, and compared these cases with 100 cases of conventional gastric adenocarcinoma (CGA). Immunohistochemistry for AFP, glypican 3, SALL4, and p53 was performed, and the phenotypic expression of the tumors was evaluated by immunostaining with antibodies against MUC5AC, MUC6, MUC2, CD10, and caudal-type homeobox 2 (CDX2).

RESULTS

Lymphatic and venous invasion was more frequent in GAED (76 and 72 %) than in CGA (41 and 31 %; P ≤ 0.001). Lymph node metastasis was more frequently observed in GAED (69 %) than in CGA (38 %; P = 0.005), as were synchronous or metachronous liver metastases (GAED, 31 %; CGA, 6 %; P ≤ 0.001). Immunohistochemically, all GAED were positive for at least one of three enteroblastic linage markers (AFP, glypican 3, and SALL4). Glypican 3 was the most sensitive marker (83 %) for GAED, followed by SALL4 (72 %) and AFP (45 %), whereas no CGA was positive. Furthermore, the rate of positive p53 staining was 59 % in GAED. Regarding the mucin phenotype, CD10 and CDX2 were diffusely or focally expressed in all GAED cases. Invasive areas with hepatoid or enteroblastic differentiation were negative for CD10 and CDX2.

CONCLUSIONS

Clinicopathologic features of GAED differ from those of CGA. GAED shows aggressive biological behavior, and is characteristically immunoreactive to AFP, glypican 3, or SALL4.

Zinc Fingers and Homeoboxes 2 (Zhx2) Regulates Sexually Dimorphic Cyp Gene Expression in the Adult Mouse Liver

The mammalian cytochrome P450 (Cyp) gene family encodes a large number of structurally related enzymes that catalyze a variety of metabolic and detoxification reactions. The liver is the primary site of Cyp expression in terms of expression levels and number of expressed genes, consistent with this organ's essential role in metabolism of endogenous and xenobiotic compounds. Many Cyp genes exhibit sexually dimorphic expression. For example, Cyp2a4 is expressed significantly higher in the adult liver of female mice compared to male mice. An exception to this pattern is seen in BALB/cJ mice, where male hepatic Cyp2a4 mRNA levels are substantially elevated compared to male mice of other strains. The Zinc fingers and homeoboxes 2 (Zhx2) protein governs the silencing of several genes in the postnatal liver, including α-fetoprotein, H19, and glypican 3. Zhx2 also regulates numerous hepatic genes that govern lipid homeostasis. We previously showed that the Zhx2 gene is mutated in BALB/cJ mice, which led us to consider whether elevated male hepatic Cyp2a4 levels in this strain are due to this Zhx2 mutation. Using mice with a conditional Zhx2 deletion, we show here that the absence of Zhx2 in hepatocytes results in increased Cyp2a4 expression in adult male liver. We extend this finding to show that additional Cyp genes are disregulated in the absence of Zhx2. We also show that mRNA levels of Cyp2a4 and several other female-biased Cyp genes are increased, and male-biased Cyp4a12 is decreased in mouse liver tumors. These data indicate that Zhx2 is a novel regulator of sex-biased Cyp gene expression in the normal and diseased liver.

ZHX2 enhances the cytotoxicity of chemotherapeutic drugs in liver tumor cells by repressing MDR1 via interfering with NF-YA

We previously reported the tumor suppressor function of Zinc-fingers and homeoboxes 2 (ZHX2) in hepatocellular carcinoma (HCC). Other studies indicate the association of increased ZHX2 expression with improved response to high dose chemotherapy in multiple myeloma. Here, we aim to test whether increased ZHX2 levels in HCC cells repress multidrug resistance 1(MDR1) expression resulting in increased sensitivity to chemotherapeutic drugs. We showed evidence that increased ZHX2 levels correlated with reduced MDR1 expression and enhanced the cytotoxicity of CDDP and ADM in different HCC cell lines. Consistently, elevated ZHX2 significantly reduced ADM efflux in HepG2 cells and greatly increased the CDDP-mediated suppression of liver tumor growth in vivo. Furthermore, immunohistochemical staining demonstrated the inverse correlation of ZHX2 and MDR1 expression in HCC tissues. Luciferase report assay showed that ZHX2 repressed the MDR1 promoter activity, while knockdown of NF-YA or mutating the NF-Y binding site eliminated this ZHX2-mediated repression of MDR1 transcription. Co-IP and ChIP assay further suggested that ZHX2 interacted with NF-YA and reduced NF-Y binding to the MDR1 promoter. Taken together, we clarify that ZHX2 represses NF-Y-mediated activation of MDR1 transcription and, in doing so, enhances the effects of chemotherapeutics in HCC cells both in vitro and in vivo.

ZBTB20 is a sequence-specific transcriptional repressor of alpha-fetoprotein gene

Alpha-fetoprotein (AFP) represents a classical model system to study developmental gene regulation in mammalian cells. We previously reported that liver ZBTB20 is developmentally regulated and plays a central role in AFP postnatal repression. Here we show that ZBTB20 is a sequence-specific transcriptional repressor of AFP. By ELISA-based DNA-protein binding assay and conventional gel shift assay, we successfully identified a ZBTB20-binding site at −104/−86 of mouse AFP gene, flanked by two HNF1 sites and two C/EBP sites in the proximal promoter. Importantly, mutation of the core sequence in this site fully abolished its binding to ZBTB20 in vitro, as well as the repression of AFP promoter activity by ZBTB20. The unique ZBTB20 site was highly conserved in rat and human AFP genes, but absent in albumin genes. These help to explain the autonomous regulation of albumin and AFP genes in the liver after birth. Furthermore, we demonstrated that transcriptional repression of AFP gene by ZBTB20 was liver-specific. ZBTB20 was dispensable for AFP silencing in other tissues outside liver. Our data define a cognate ZBTB20 site in AFP promoter which mediates the postnatal repression of AFP gene in the liver.

Zinc fingers and homeoboxes family in human diseases

The zinc-fingers and homeoboxes (ZHX) family is a group of nuclear homodimeric transcriptional repressors that interact with a subunit of nuclear factor-Y (NF-YA) and contain two C2H2-type zinc fingers and five homeobox DNA-binding domains. The members of ZHX family form homodimers or heterodimers with other members or a subunit of NF-YA to repress transcription. ZHX family members function in hematopoietic cell development and differentiation, and neural progenitor maintenance. Dysfunction of ZHX family members correlates with the development and progression of various diseases, including hepatocellular carcinoma (HCC), hematological diseases, neurological diseases and glomerular diseases. Furthermore, low expression of ZHX is associated with poor prognosis in malignancies. This review provides an update on the role of ZHX family in development and its function in cancer, with special emphasis on HCC and hematological malignant diseases.

Nanoparticle-formulated siRNA targeting integrins inhibits hepatocellular carcinoma progression in mice

Integrins play an important role during development, regulating cell differentiation, proliferation and survival. Here we show that knockdown of integrin subunits slows down the progression of hepatocellular carcinoma (HCC). Using nanoparticulate delivery of short interfering RNAs targeting β1 and αv integrin subunits we downregulate all integrin receptors in hepatocytes. Short-term integrin knockdown (two weeks) does not cause apparent structural or functional perturbations of normal liver tissue. Alterations in liver morphology accumulate upon sustained integrin downregulation (seven weeks). The integrin knockdown leads to significant retardation of HCC progression, reducing proliferation and increasing tumour cell death. This tumour retardation is accompanied by reduced activation of MET oncogene as well as expression of its mature form on the cell surface. Our data suggest that transformed proliferating cells from HCC are more sensitive to knockdown of integrins than normal quiescent hepatocytes, highlighting the potential of siRNA-mediated inhibition of integrins as an anti-cancer therapeutic approach.

ZBTB20 is involved in liver regeneration after partial hepatectomy in mouse

BACKGROUND

A better understanding of the molecular mechanisms in liver regeneration holds promise for exploring the new potential therapy for liver failure. The present study was to investigate the role of zinc finger and BTB domain-containing protein 20 (ZBTB20), a potential factor associated with liver regeneration, in a model of 70% hepatectomy in mice.

METHODS

Parameters for liver proliferation such as liver/body ratio and BrdU positivity were obtained via direct measurement and immunohistochemistry. The levels of zinc fingers and homeoboxes 2 (ZHX2), ZBTB20, alpha-fetoprotein (AFP) and glypican 3 (GPC3) transcripts in the regenerating liver tissue of a 70% hepatectomy rodent model were monitored by real-time PCR analysis at different time points. Knockdown of ZBTB20 was performed to characterize its regulatory function.

RESULTS

A negatively regulating relationship between ZHX2, ZBTB20 and AFP, GPC3 was revealed from 24 to 72 hours after 70% hepatectomy. ZBTB20 appears to negatively regulate AFP and GPC3 transcription since the knockdown of ZBTB20 promoted the proliferation of hepatocytes and the expression of AFP and GPC3.

CONCLUSION

In addition to AFP, GPC3 and ZHX2, ZBTB20 is a new regulator in liver regeneration and the decrease of ZBTB20 expression following 70% hepatectomy promotes AFP and GPC3 expression.

Construction of a recombinant eukaryotic human ZHX1 gene expression plasmid and the role of ZHX1 in hepatocellular carcinoma

The zinc-fingers and homeoboxes protein 1 (ZHX1) consists of 873 amino acid residues, is localized in the cell nucleus and appears to act as a transcriptional repressor. Previous studies have shown that ZHX1 interacts with nuclear factor Y subunit α (NF-YA), DNA methyltransferases (DNMT) 3B and ZHX2, all of which are involved in tumorigenesis. However, the exact role of ZHX1 in tumorigenesis remains unknown. The aim of the current study was to construct a recombinant eukaryotic expression plasmid containing the human ZHX1 (hZHX1) gene and to investigate the biological activities of ZHX1 in hepatocellular carcinoma (HCC). Reverse transcription-polymerase chain reaction (RT‑PCR) was used to amplify the N- and C-terminal fragments (ZHX1‑N and ZHX1‑C, respectively) of the hZHX1 gene. The two PCR fragments were cloned into the pEASY-T1 vector and subcloned into the pcDNA3 plasmid to generate a recombinant pcDNA3‑ZHX1 plasmid. Following identification by enzyme digestion and DNA sequencing, the recombinant pcDNA3‑ZHX1 plasmid was transfected into SMMC-7721 cells. The level of ZHX1 expression was detected by RT-PCR and western blot analysis. Cell growth curve assays were used to evaluate the effect of ZHX1 on cell proliferation. Moreover, the differential expression of ZHX1 between cancer and adjacent cirrhotic liver tissue was investigated by quantitative PCR (qPCR). Enzyme digestion and DNA sequencing confirmed the successful construction of the recombinant plasmid, pcDNA3‑ZHX1. qPCR and western blot analysis demonstrated that ZHX1 was efficiently expressed in SMMC-7721 cells and overexpression of ZHX1 may inhibit the proliferation of SMMC-7721 cells. In addition, reduced ZHX1 expression is widespread among cancer tissues from HCC patients. In conclusion, a recombinant eukaryotic expression plasmid, pcDNA3‑ZHX1, was successfully constructed. In addition, the current results indicate that a low expression of ZHX1 may be responsible for hepatocarcinogenesis.

Recent topics on α-fetoprotein

Zinc-fingers and homeoboxes 2 (ZHX2) and zinc-finger and BTB domain containing 20 (ZBTB20) repress the postnatal expression of α-fetoprotein (AFP) by interacting with the AFP gene promoter regions. ZHX2 inhibits the expression of AFP and cyclins A and E. ZBTB20 is negatively regulated by CUX1, which promotes cell-cycle progression, suggesting that AFP reactivation is closely linked to hepatocyte proliferation. A slight elevation in the serum AFP level often occurs in patients with chronic hepatitis C in the absence of hepatocellular carcinoma (HCC) and is an independent risk factor for HCC development to complement the fibrosis stage. In addition, the sustained elevation of AFP after interferon therapy is a risk factor of HCC development. AFP levels are clinically useful in predicting the outcomes of liver transplantation and sorafenib therapy for HCC patients. A low preoperative AFP level is a predictor of long-term survival and is associated with a low recurrence rate of HCC after liver transplantation. AFP response (≥20% decrease in AFP during 6-8 weeks of treatment) rather than radiological outcomes is a significant prognostic factor for survival in sorafenib-treated HCC patients. Highly sensitive Lens culinaris agglutinin-reactive AFP (AFP-L3) is 5-10 times more sensitive than conventional AFP-L3, and useful for early detection of HCC in patients with total AFP below 20 ng/mL.