Embryonic Liver Fodrin Research Articles

Expression of embryonic liver fodrin (ELF) and stem cell markers in CD13 liver cancer stem cells.

Investigating the molecular signaling pathways using CD13 as a marker for Cancer Stem Cells (CSCs) in human liver cancer. In the present study, liver carcinoma biopsies were obtained from the liver cancer patients, as well as healthy controls. Immunohistochemistry and Immunoblotting experiments were performed accordingly to conclude the data. Immunohistochemistry along with immunoblot data showed the expression of Oct-4, STAT3 and interestingly Embryonic Liver Fodrin (ELF) in the CD13 positive liver cancer stem cells. Though embryonic liver fodrin (ELF) is a pro-differentiation protein, it was expressed in the CD13 positive liver cancer stem cells along with stem cell markers such as Oct-4 and STAT3. Our finding concludes that an association of ELF expression was noted in liver cancer patients. Hence, ELF may have value as prognostic indicators and may facilitate the development of novel therapeutics for liver cancer.

SIRT-1expression is associated with expression of NANOG in patients with colorectal adenocarcinoma.

The study aimed to investigate the quantitative expression of NANOG, p38 α , NCF2, ELF and TGF-β genes in patients with colorectal adenocarcinoma, adenoma and normal colonic tissue and their correlation with SIRT-1 protein level expression. This study enrolled one hundred sixty seven patients; group A: 87 patients with colonoscopic findings of no adenoma or adenocarcinoma and group B: 80 patients with colorectal mass. Consecutive colonoscopic examinations were conducted, and tissue samples were taken from the colonic lesions/masses. Total RNA was isolated and mRNA expression level of NANOG, mitogen activated p38α , Neutrophil Cytosol Factor 2 (NCF2), Embryonic Liver Fodrin (ELF) and Transforming Growth Factor Beta (TGF-β) genes were quantified by qRT-PCR. Sirt-1 protein expression level was assessed by quantitative western blot. There were significantly high level of mRNA transcripts expression of the genes studied in patients with adenocarcinoma and adenoma compared with normal tissue (P value < 0.01), NANOG, NCF2, ELF and TGF-β at a cut of > 0.314, > 0.392, 0.349 and 0.333 respectively showed sensitivity (96.5%, 98.8%, 95.3%, 98.8%) and specificity of (95.3%, 92.6%, 89.5%, 93.8%) respectively in diagnosing colonic adenocarcinoma. Sirt-1 protein level was significantly highly expressed in colorectal adenocarcinoma compared to normal and adenoma colonic tissue and positively correlated with NANOG. Over expression of NANOG, p38α , NCF2, ELF and TGF-β genes in both cases of adenocarcinoma and adenoma could have a diagnostic value. SIRT-1 and NANOG are high correlated biological markers for diagnosis and prognosis follow up in patients with adenocarcinoma.

The prognostic value of combined TGF-β1 and ELF in hepatocellular carcinoma.

BackgroundTumor suppression of Transforming Growth Factor (TGF-β) signaling pathway requires an adaptor protein, Embryonic Liver Fodrin (ELF). Disruption of ELF expression resulted in miscolocalization of Smad3 and Smad4, then disruption of TGF-β signaling. However, the prognostic significance of ELF for hepatocellular carcinoma (HCC) hasn’t been clarified. This study aimed to investigate whether measuring both TGF-β1 and ELF provides a more powerful predictor for HCC prognosis than either marker alone.MethodsTGF-β1 and ELF protein were detected by immunohistochemistry. The relationship between TGF-β1/ELF expression and patients’ clinicopathologic factors was analyzed. The association between TGF-β1/ELF expression and disease-free survival and overall survival was analyzed by Kaplan-Meier curves, the log-rank test, and Multivariate Cox regression analyses.ResultsThe expression of TGF-β1 in HCC tissues was significantly higher than that in normal liver tissues. Conversely, the expression of ELF in HCC tissues declined markedly. ELF protein was correlated with HBsAg, tumor size, tumor number, TNM and recurrence. Data also indicated a significant negative correlation between ELF and TGF-β1. Patients with high TGF-β1 expression or/and low ELF expression appeared to have a poor postoperative disease-free survival and overall survival compared with those with low TGF-β1 expression or/and high ELF expression. Furthermore, the predictive range of ELF combined with TGF-β1 was more sensitive than that of either one alone.ConclusionsTGF-β1 and ELF protein are potential and reliable biomarkers for predicting prognosis in HCC patients after hepatic resection. Our current study has demonstrated that the prognostic accuracy of testing can be enhanced by their combination.

Embryonic liver fodrin involved in hepatic stellate cell activation and formation of regenerative nodule in liver cirrhosis

Transforming growth factor (TGF) β1 plays a critical role in liver fibrosis. Previous studies demonstrated embryonic liver fodrin (ELF), a β-spectrin was involved in TGF-β/Smad signalling pathway as Smad3/4 adaptor. Here we investigate the role of ELF in pathogenesis of liver cirrhosis. In carbon tetrachloride (CCl4)-induced mice model of liver cirrhosis, ELF is up-regulated in activated hepatic stellate cells (HSCs), and down-regulated in regenerative hepatocytes of cirrhotic nodules. In activated HSCs in vitro, reduction of ELF expression mediated by siRNA leads to the inhibition of HSC activation and procollagen I expression. BrdU assay demonstrates that down-regulation of ELF expression does not inhibit proliferation of activated HSCs in vitro. Immunostaining of cytokeratin 19 and Ki67 indicates that regenerative hepatocytes in cirrhotic liver are derived from hepatic progenitor cells (HPC). Further study reveals that HPC expansion occurs as an initial phase, before the reduction of ELF expression in regenerative hepatocytes. Regenerative hepatocytes in cirrhotic liver show the change in proliferative activity and expression pattern of proteins involved in G1/S transition, which suggests the deregulation of cell cycle in regenerative hepatocytes. Finally, we find that ELF participates in TGF-β/Smad signal in activated HSCs and hepatocytes through regulating the localization of Smad3/4. These data reveal that ELF is involved in HSC activation and the formation of regenerative nodules derived from HPC in cirrhotic liver.

Abstract LB-110: CDK4 activation is a key step in ELF alteration and haploinsufficeny of cdk4 prevents HCC formation in elf+/− mice

Abstract Transforming growth factor (TGF-) is an important regulator of cell growth and the loss of TGF- signaling occurs early in carcinogenesis. Embryonic liver fodrin (ELF), an interaction protein of Smads, is involved in TGF- signaling. Significantly, elf+/− mice spontaneously developed the hepatocellular cancer (HCC) and lots of human HCC exhibited decreased or absent ELF expression. Here, we investigated how alteration of ELF led the deregulation of cell cycle progression and eventually formed the HCC. Up regulation of ELF expression led the decreased phosphorylation of Rb protein with the remarkable reduction of CDK4 than other CDKs and cyclins. Then, inhibition and downregulation of CDK4 by inhibitor and siRNA rescued the abnormality of G1/S transition and over-activation of Rb phosphorylation caused by infection of ELF shRNA in SNU475 HCC cell line. We further demonstrated the biochemical communications using immunoprecipitation that ELF interacted CDK4, and Smad3 in competitive way and TGF-ß-dependent manner. In addition, haploinsufficieny of cdk4 in elf+/− mice displayed the dramatic decrement of HCC formation than elf+/− mice with decreased Ki-67 and c-myc expressed hepatocyte in liver tissue. Thus, in response to ELF deficiency, the activation of CDK4 contributes to the phosphorylation of Rb protein, which leading to facilitated G1/S transition. Our data highlight CDK4 as an attractive target for pharmacologic inhibition and importance of elf+/− model to demonstrate pre-clinical efficacy in the treatment of HCC with ELF alteration. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-110.

Hepatocellular cancer arises from loss of transforming growth factor beta signaling adaptor protein embryonic liver fodrin through abnormal angiogenesis†

We have previously demonstrated that 40%-70% of elf(+/-) mice spontaneously develop hepatocellular cancer (HCC) within 15 months, revealing the importance of the transforming growth factor-beta (TGF-beta) signaling pathway in suppressing tumorigenesis in the liver. The current study was carried out to investigate mechanisms by which embryonic liver fodrin (ELF), a crucial Smad3/4 adaptor, suppresses liver tumor formation. Histological analysis of hyperplastic liver tissues from elf(+/-) mice revealed abundant newly formed vascular structures, suggesting aberrant angiogenesis with loss of ELF function. In addition, elf(+/-) mice displayed an expansion of endothelial progenitor cells. Ectopic ELF expression in fetal bovine heart endothelial (FBHE) cells resulted in cell cycle arrest and apoptosis. Further analysis of developing yolk sacs of elf(-/-) mice revealed a failure of normal vasculature and significantly decreased endothelial cell differentiation with embryonic lethality. Immunohistochemical analysis of hepatocellular cancer (HCC) from the elf(+/-) mice revealed an abnormal angiogenic profile, suggesting the role of ELF as an angiogenic regulator in suppressing HCC. Lastly, acute small interfering RNA (siRNA) inhibition of ELF raised retinoblastoma protein (pRb) levels nearly fourfold in HepG2 cells (a hepatocellular carcinoma cell line) as well as in cow pulmonary artery endothelial (CPAE) cells, respectively. Taken together these results, ELF, a TGF-beta adaptor and signaling molecule, functions as a critical adaptor protein in TGF-beta modulation of angiogenesis as well as cell cycle progression. Loss of ELF in the liver leads the cancer formation by deregulated hepatocyte proliferation and stimulation of angiogenesis in early cancers. Our studies propose that ELF is potentially a powerful target for mimetics enhancing the TGF-beta pathway tumor suppression of HCC.

Transforming growth factor- signaling and ubiquitinators in cancer

Transforming growth factor-beta (TGF-beta) represents a large family of growth and differentiation factors that mobilize complex signaling networks to regulate cellular differentiation, proliferation, motility, adhesion, and apoptosis. TGF-beta signaling is tightly regulated by multiple complex mechanisms, and its deregulation plays a key role in the progression of many forms of cancer. Upon ligand binding, TGF-beta signals are transduced by Smad proteins, which in turn are tightly dependent on modulation by adaptor proteins such as embryonic liver fodrin, Smad anchor for receptor activation, filamin, and crkl. A further layer of regulation is imposed by ubiquitin-mediated targeting and proteasomal degradation of specific components of the TGF-beta signaling pathway. This review focuses on the ubiquitinators that regulate TGF-beta signaling and the association of these ubiquitin ligases with various forms of cancer. Delineating the role of ubiquitinators in the TGF-beta signaling pathway could yield powerful novel therapeutic targets for designing new cancer treatments.

Progenitor/stem cells give rise to liver cancer due to aberrant TGF-β and IL-6 signaling

Cancer stem cells (CSCs) are critical for the initiation, propagation, and treatment resistance of multiple cancers. Yet functional interactions between specific signaling pathways in solid organ "cancer stem cells," such as those of the liver, remain elusive. We report that in regenerating human liver, two to four cells per 30,000-50,000 cells express stem cell proteins Stat3, Oct4, and Nanog, along with the prodifferentiation proteins TGF-beta-receptor type II (TBRII) and embryonic liver fodrin (ELF). Examination of human hepatocellular cancer (HCC) reveals cells that label with stem cell markers that have unexpectedly lost TBRII and ELF. elf(+/-) mice spontaneously develop HCC; expression analysis of these tumors highlighted the marked activation of the genes involved in the IL-6 signaling pathway, including IL-6 and Stat3, suggesting that HCC could arise from an IL-6-driven transformed stem cell with inactivated TGF-beta signaling. Similarly, suppression of IL-6 signaling, through the generation of mouse knockouts involving a positive regulator of IL-6, Inter-alpha-trypsin inhibitor-heavy chain-4 (ITIH4), resulted in reduction in HCC in elf(+/-) mice. This study reveals an unexpected functional link between IL-6, a major stem cell signaling pathway, and the TGF-beta signaling pathway in the modulation of mammalian HCC, a lethal cancer of the foregut. These experiments suggest an important therapeutic role for targeting IL-6 in HCCs lacking a functional TGF-beta pathway.

Haploinsufficiency of CDK4 prevents hepatocarcinogenesis in mice deficient in ELF, a mediator of TGF-beta signaling

10608 Background: The transforming growth factor-β (TGF-β) has a dual role in cancer, but in the prevention of tumorigenesis, TGF-β signaling inhibits cell cycle progression through an increase in cell cycle inhibitors and decrease in cell cycle activators. The adaptor protein embryonic liver fodrin (ELF) is crucial for normal TGF-β signaling. ELF facilitates the association and nuclear translocation of the TGF-β signaling proteins, Smad3 and Smad4. We have demonstrated that elf± mice develop hepatocellular cancers (HCC) spontaneously within 12 months. We have also shown that most human HCCs demonstrate a decreased expression of ELF. Our goal was to assess the interaction between ELF and cyclin dependent kinase 4 (CDK4), which is overexpressed in most human cancers. Methods: We compared the expression of CDK4 and ELF by immunohistochemistry and analyzed the interaction between CDK4 and ELF, in vitro by immunoprecitpitation and western blot. Finally, we assessed the development of HCC in intercrossed elf± and CDK4+/neo mice. Results: CDK4 and ELF expression are inversely correlated in HCCs from elf± mice. Furthermore, ELF interacts with CDK4 by forming a complex that includes Smad3 in COS-7 and HepG2 cells. ELF is phosphorylated upon overexpression of CDK4, revealing a possible mechanism by which CDK4 may inhibit ELF-dependent TGF-β signaling. To further assess whether the development of HCC in elf± mice is dependent upon CDK4 expression, we have intercrossed elf± and CDK4+/neo mice. At 12 months, only 17% of the elf±/CDK4+/neo mice developed HCC, compared to 40% of our historical control elf± mice. This initial data strongly suggests that haploinsufficiency of CDK4 can prevent the HCCs seen in elf± mice, and provides the genetic foundation for further exploring the benefits of specific inhibitors of CDK4 in the treatment of HCC. Conclusions: These results demonstrate the molecular interactions between ELF and CDK4, and suggest a mechanism by which CDK4 may render cells unresponsive to the growth inhibitory effects of TGF-β signaling. Furthermore, haploinsufficiency of CDK4 prevents the formation of HCC, and thus targeted-inhibition of CDK4 activity may be a logical treatment for HCC in humans. No significant financial relationships to disclose.

Disruption of transforming growth factor-β signaling through β-spectrin ELF leads to hepatocellular cancer through cyclin D1 activation

Transforming growth factor-beta (TGF-beta) signaling members, TGF-beta receptor type II (TBRII), Smad2, Smad4 and Smad adaptor, embryonic liver fodrin (ELF), are prominent tumor suppressors in gastrointestinal cancers. Here, we show that 40% of elf(+/-) mice spontaneously develop hepatocellular cancer (HCC) with markedly increased cyclin D1, cyclin-dependent kinase 4 (Cdk4), c-Myc and MDM2 expression. Reduced ELF but not TBRII, or Smad4 was observed in 8 of 9 human HCCs (P<0.017). ELF and TBRII are also markedly decreased in human HCC cell lines SNU-398 and SNU-475. Restoration of ELF and TBRII in SNU-398 cells markedly decreases cyclin D1 as well as hyperphosphorylated-retinoblastoma (hyperphosphorylated-pRb). Thus, we show that TGF-beta signaling and Smad adaptor ELF suppress human hepatocarcinogenesis, potentially through cyclin D1 deregulation. Loss of ELF could serve as a primary event in progression toward a fully transformed phenotype and could hold promise for new therapeutic approaches in human HCCs.

Cancer stem cells

The Sixteenth International Symposium of the Hiroshima Cancer Seminar (HCS) Foundation was held on October 22 2006 at the International Conference Center, Hiroshima. The symposium consisted of 10 special lectures and 23 free paper presentations for a poster session. About 230 people were present and actively discussed cancer stem cells. Prior to this symposium, an Open Lecture to the public by HCS and the Japan Society for Dying with Dignity was held on October 21 where Shigehito Yamawaki (Hiroshima University, Hiroshima) and Kazuko Hamanaka (Hamanaka Dermatological Clinic, Hiroshisma) spoke about Psycho-oncology and Breast Cancer to more than 260 people. Eiichi Tahara (Hiroshima Cancer Seminar Foundation), Chairman of the Organizing Committee of the Sixteenth International Symposium, and Chairman of the HCS Foundation, gave an opening address. Tahara introduced a brief background and the purpose of this series of symposia. Since the establishment of the HCS Foundation in 1992, annual international symposia are organized to create an opportunity for basic scientists and clinical researchers to exchange ideas for cancer research, cancer prevention and cancer therapy. This year, the organizing committee planned to explore the important issue of cancer stem cells. Stem cells have a critical role not only in the generation of new populations of normal cells but also in the development of tumors. The balance between self-renewal and differentiation is strictly regulated to maintain normal stem cell pools and to generate the required supply of fully differentiated cells. Recent evidence has suggested that a subset of cancer cells within the tumor, so-called cancer stem cells, may drive the growth and progression of the tumor. Eradication of cancer stem cells may be essential to a cure for cancer. Advances in our knowledge that regulate proliferation, self-renewal, survival and differentiation of cancer stem cells and normal stem cells may shed light on the mechanism that leads to cancer and perhaps improve cancer treatment. The participants will be able to profit by exchanging ideas and learning from the informative presentations and discussions, and will contribute to our understanding of stem cells in relation to cancer development and treatment.

Cell cycle deregulation and loss of stem cell phenotype in the subventricular zone of TGF-β adaptor elf−/− mouse brain

The mammalian forebrain subependyma contains neural stem cells and other proliferating progenitor cells. Recent studies have shown the importance of TGF-β family members and their adaptor proteins in the inhibition of proliferation in the nervous system. Previously, we have demonstrated that TGF-β induces phosphorylation and association of ELF (embryonic liver fodrin) with Smad3 and Smad4 resulting in nuclear translocation. Elf −/− mice manifest abnormal neuronal differentiation, with loss of neuroepithelial progenitor cell phenotype in the subventricular zone (SVZ) with dramatic marginal cell hyperplasia and loss of nestin expression. Here, we have analyzed the expression of cell cycle-associated proteins cdk4, mdm2, p21, and pRb family members in the brain of elf −/− mice to verify the role of elf in the regulation of neural precursor cells in the mammalian brain. Increased proliferation in SVZ cells of the mutant mice coincided with higher levels of cdk4 and mdm2 expression. A lesser degree of apoptosis was observed in the mutant mice compared to the wild-type control. Elf −/− embryos showed elevated levels of hyperphosphorylated forms of pRb, p130 and p107 and decreased level of p21 compared to the wild-type control. These results establish a critical role for elf in the development of a SVZ neuroepithelial stem cell phenotype and regulation of neuroepithelial cell proliferation, suggesting that a mutation in the elf locus renders the cells susceptible to a faster entry into S phase of cell cycle and resistance to senescence and apoptotic stimuli.

Critical interactions between TGF-β signaling/ELF, and E-cadherin/β-catenin mediated tumor suppression

Inactivation of the transforming growth factor-beta (TGF-beta) pathway occurs often in malignancies of the gastrointestinal (GI) system. However, only a fraction of sporadic GI tumors exhibit inactivating mutations in early stages of cancer formation, suggesting that other mechanisms play a critical role in the inactivation of this pathway. Here, we show a wide range of GI tumors, including those of the stomach, liver and colon in elf+/- and elf+/- / Smad4+/- mutant mice. We found that embryonic liver fodrin (ELF), a beta-Spectrin originally identified in endodermal stem/progenitor cells committed to foregut lineage, possesses potent antioncogenic activity and is frequently inactivated in GI cancers. Specifically, E-cadherin accumulation at cell-cell contacts and E-cadherin-beta-catenin-dependent epithelial cell-cell adhesion is disrupted in elf+/- / Smad4+/- mutant gastric epithelial cells, and could be rescued by ectopic expression of full-length elf, but not Smad3 or Smad4. Subcellular fractionation revealed that E-cadherin is expressed mainly at the cell membrane after TGF-beta stimulation. In contrast, elf+/- / Smad4+/- mutant tissues showed abnormal distribution of E-cadherin that could be rescued by overexpression of ELF but not Smad3 or Smad4. Our results identify a group of common lethal malignancies in which inactivation of TGF-beta signaling, which is essential for tumor suppression, is disrupted by inactivation of the ELF adaptor protein.

RING finger-dependent ubiquitination by PRAJA is dependent on TGF-β and potentially defines the functional status of the tumor suppressor ELF

In gastrointestinal cells, biological signals for transforming growth factor-beta (TGF-beta) are transduced through transmembrane serine/threonine kinase receptors that signal to Smad proteins. Smad4, a tumor suppressor, is often mutated in human gastrointestinal cancers. The mechanism of Smad4 inactivation, however, remains uncertain and could be through E3-mediated ubiquitination of Smad4/adaptor protein complexes. Disruption of ELF (embryonic liver fodrin), a Smad4 adaptor protein, modulates TGF-beta signaling. We have found that PRAJA, a RING-H2 protein, interacts with ELF in a TGF-beta-dependent manner, with a fivefold increase of PRAJA expression and a subsequent decrease in ELF and Smad4 expression, in gastrointestinal cancer cell lines (P < 0.05). Strikingly, PRAJA manifests substantial E3-dependent ubiquitination of ELF and Smad3, but not Smad4. Delta-PRAJA, which has a deleted RING finger domain at the C terminus, abolishes ubiquitination of ELF. A stable cell line that overexpresses PRAJA exhibits low levels of ELF in comparison to a Delta-PRAJA stable cell line, where ELF expression is high compared to normal controls. The alteration of ELF and/or Smad4 expression and/or function in the TGF-beta signaling pathway may be induced by enhancement of ELF degradation, which is mediated by a high-level expression of PRAJA in gastrointestinal cancers. In hepatocytes, half-life (t(1/2)) and rate constant for degradation (k(D)) of ELF is 1.91 h and 21.72 min(-1) when coupled with ectopic expression of PRAJA in cells stimulated by TGF-beta, compared to PRAJA-transfected unstimulated cells (t(1/2) = 4.33 h and k(D) = 9.6 min(-1)). These studies reveal a mechanism for tumorigenesis whereby defects in adaptor proteins for Smads, such as ELF, can undergo degradation by PRAJA, through the ubiquitin-mediated pathway.

Orofacial and gastrointestinal hyperplasia and neoplasia in smad4+/− and elf+/−/smad4+/− mutant mice

Smad4 is vital to the roles of Smads 2 and 3 in transforming growth factor-beta (TGF)-beta signal transduction, and inactivated Smad4 is common to human gastrointestinal cancers. The embryonic liver fodrin (ELF) is a beta-spectrin that facilitates the nuclear translocation of activated Smad4. Smad4+/- mice, known to develop gastrointestinal cancer, were crossbred with elf+/- mice. The smad4+/- and smad4+/-/elf+/- offspring were autopsied as abnormalities developed. In addition to polyps and adenocarcinomas of the stomach and duodenum, the smad4+/- mice developed squamous cell carcinomas of the skin, oral mucosa and forestomach, benign neoplasms of connective tissue and lacrimal gland, and a lymphoma. The smad4+/-/elf+/- mice developed extensive hyperplasia and neoplasia of the gastric mucosa. These findings indicate that investigating interactions among smad4, elf, and other genes involved in TGF-beta signaling should be useful in further delineating the processes of neoplasia in a wide variety of tissues.

Loss of cooperative function of transforming growth factor‐β signaling proteins, smad3 with embryonic liver fodrin, a β‐spectrin, in primary biliary cirrhosis

Modulation of fibrogenesis, epithelial, and mesenchymal cell fates are prominent effects of transforming growth factor-beta (TGF-beta) signaling by Smad proteins. We have previously shown that Smad2 and Smad3 insufficiency leads to a loss of bile ducts. In addition, Smad3/4 activity is mediated by embryonic liver fodrin (ELF), a beta-Spectrin. In mouse elf(-/-) mutants and in liver explant cultures, loss of ELF function results in T lymphocytic proliferation and absent intrahepatic bile ducts. A similar phenotype is seen in a number of cholestatic diseases with progressive loss of intrahepatic bile ducts and fibrosis. However, the expression patterns of Smads or role of ELF in cholestatic and fibrotic liver diseases are not yet known. We investigated the role of ELF in primary biliary cirrhosis (PBC), autoimmune hepatitis C, chronic viral hepatitis and in livers from mice deficient in Smad2/Smad3. We generated elf(+/-) mutant mice and analyzed for chronic liver disease and hepatocellular cancer (HCC) from 6 to 12 months. Perturbations in ELF expression were consistently seen only in PBC tissues. ELF expression was similarly aberrant in tissues from Smad2(+/-)/Smad3(+/-) mutant mice. Further studies indicated that ELF mislocalization is correlated with aberrant localization of Smad3 in some PBC tissues. Thirteen of 17 elf(+/-) mutant mice developed steatosis, fibrosis, hepatic dysplasia, with HCC in two mice. These results suggest that a compromised cytoarchitecture and polarized trafficking of TGF-beta signaling molecules, ELF and Smad3 are involved in the pathogenesis of PBC as well as HCC.

Identification of elf1, a beta-spectrin, in early mouse liver development.

Beta-spectrins play essential roles in cell-cell interactions and in the maintenance of cell polarity. Our aim was to identify beta-spectrin genes important for the establishment of hepatocyte polarity and differentiation. Using subtractive screening of cDNA libraries from early embryonic mouse livers (post-coital days 10, 11, and 12), we have isolated elf1 (embryonic liver fodrin 1), a differentially expressed beta-spectrin or fodrin (betaSpIIsigmaI). Elf1 encodes a 220-amino acid protein with an NH2 terminal actin-binding domain. In situ hybridization studies demonstrate elf1 expression initially in day 10 embryonic heart tissue, then in day 11-11.5 hepatic tissue. These studies suggest that elf1 may play a role in the emergence of hepatocyte polarity during liver development.