Heterozygous Mutations in SMARCA2 Reprogram the Enhancer Landscape by Global Retargeting of SMARCA4.

Mammalian SWI/SNF complexes are multi-subunit chromatin remodeling complexes associated with an ATPase (either SMARCA4 or SMARCA2). Heterozygous mutations in the SMARCA2 ATPase cause Nicolaides-Baraitser syndrome (NCBRS), an intellectual disability syndrome associated with delayed speech onset. We engineered human embryonic stem cells (hESCs) to carry NCBRS-associated heterozygous SMARCA2 K755R or R1159Q mutations. While SMARCA2 mutant hESCs were phenotypically normal, differentiation to neural progenitors cells (NPCs) was severely impaired. We find that SMARCA2 mutations cause enhancer reorganization with loss of SOX3-dependent neural enhancers and prominent emergence of astrocyte-specific de novo enhancers. Changes in chromatin accessibility at enhancers were associated with an increase in SMARCA2 binding and retargeting of SMARCA4. We show that the AP-1 family member FRA2 is aberrantly overexpressed in SMARCA2 mutant NPCs, where it functions as a pioneer factor at de novo enhancers. Together, our results demonstrate that SMARCA2 mutations cause impaired differentiation through enhancer reprogramming via inappropriate targeting of SMARCA4.

The AP-1 transcription factor component Fosl2 potentiates the rate of myocardial differentiation from the zebrafish second heart field.

The vertebrate heart forms through successive phases of cardiomyocyte differentiation. Initially, cardiomyocytes derived from first heart field (FHF) progenitors assemble the linear heart tube. Thereafter, second heart field (SHF) progenitors differentiate into cardiomyocytes that are accreted to the poles of the heart tube over a well-defined developmental window. Although heart tube elongation deficiencies lead to life-threatening congenital heart defects, the variables controlling the initiation, rate and duration of myocardial accretion remain obscure. Here, we demonstrate that the AP-1 transcription factor, Fos-like antigen 2 (Fosl2), potentiates the rate of myocardial accretion from the zebrafish SHF. fosl2 mutants initiate accretion appropriately, but cardiomyocyte production is sluggish, resulting in a ventricular deficit coupled with an accumulation of SHF progenitors. Surprisingly, mutant embryos eventually correct the myocardial deficit by extending the accretion window. Overexpression of Fosl2 also compromises production of SHF-derived ventricular cardiomyocytes, a phenotype that is consistent with precocious depletion of the progenitor pool. Our data implicate Fosl2 in promoting the progenitor to cardiomyocyte transition and uncover the existence of regulatory mechanisms to ensure appropriate SHF-mediated cardiomyocyte contribution irrespective of embryonic stage.

Effects of histone acetyltransferase inhibitors on L-DOPA-induced dyskinesia in a murine model of Parkinson's disease.

Histone acetylation is a key regulatory factor for gene expression in cells. Modulation of histone acetylation by targeting of histone acetyltransferases (HATs) effectively alters many gene expression profiles and synaptic plasticity in the brain. However, the role of HATs on L-DOPA-induced dyskinesia of Parkinson's disease (PD) has not been reported. Our aim was to determine whether HAT inhibitors such as anacardic acid, garcinol, and curcumin from natural plants reduce severity of L-DOPA-induced dyskinesia using a unilaterally 6-hydroxydopamine (6-OHDA)-lesioned PD mouse model. Anacardic acid 2 mg/kg, garcinol 5 mg/kg, or curcumin 100 mg/kg co-treatment with L-DOPA significantly reduced the axial, limb, and orofacial (ALO) score indicating less dyskinesia with administration of HAT inhibitors in 6-OHDA-lesioned mice. Additionally, L-DOPA's efficacy was not altered by the compounds in the early stage of treatment. The expression levels of c-Fos, Fra-2, and Arc were effectively decreased by administration of HAT inhibitors in the ipsilateral striatum. Our findings indicate that HAT inhibitor co-treatment with L-DOPA may have therapeutic potential for management of L-DOPA-induced dyskinesia in patients with PD.

Development of pulmonary fibrosis through a pathway involving the transcription factor Fra-2/AP-1.

Studies using genetically modified mice have revealed fundamental functions of the transcription factor Fos/AP-1 in bone biology, inflammation, and cancer. However, the biological role of the Fos-related protein Fra-2 is not well defined in vivo. Here we report an unexpected profibrogenic function of Fra-2 in transgenic mice, in which ectopic expression of Fra-2 in various organs resulted in generalized fibrosis with predominant manifestation in the lung. The pulmonary phenotype was characterized by vascular remodeling and obliteration of pulmonary arteries, which coincided with expression of osteopontin, an AP-1 target gene involved in vascular remodeling and fibrogenesis. These alterations were followed by inflammation; release of profibrogenic factors, such as IL-4, insulin-like growth factor 1, and CXCL5; progressive fibrosis; and premature mortality. Genetic experiments and bone marrow reconstitutions suggested that fibrosis developed independently of B and T cells and was not mediated by autoimmunity despite the marked inflammation observed in transgenic lungs. Importantly, strong expression of Fra-2 was also observed in human samples of idiopathic and autoimmune-mediated pulmonary fibrosis. These findings indicate that Fra-2 expression is sufficient to cause pulmonary fibrosis in mice, possibly by linking vascular remodeling and fibrogenesis, and suggest that Fra-2 has to be considered a contributing pathogenic factor of pulmonary fibrosis in humans.

Fra-2-expressing macrophages promote lung fibrosis in mice.

Idiopathic Pulmonary Fibrosis (IPF) is a deadly disease with limited therapies. Tissue fibrosis is associated with Type 2 immune response, although the causal contribution of immune cells is not defined. The AP-1 transcription factor Fra-2 is upregulated in IPF lung sections and Fra-2 transgenic mice (Fra-2tg) exhibit spontaneous lung fibrosis. Here we show that Bleomycin-induced lung fibrosis is attenuated upon myeloid-inactivation of Fra-2 and aggravated in Fra-2tg bone marrow chimeras. Type VI collagen (ColVI), a Fra-2 transcriptional target, is up-regulated in three lung fibrosis models, and macrophages promote myofibroblast activation in vitro in a ColVI- and Fra-2-dependent manner. Fra-2 or ColVI inactivation does not affect macrophage recruitment and alternative activation, suggesting that Fra-2/ColVI specifically controls the paracrine pro-fibrotic activity of macrophages. Importantly, ColVI knock-out mice (KO) and ColVI-KO bone marrow chimeras are protected from Bleomycin-induced lung fibrosis. Therapeutic administration of a Fra-2/AP-1 inhibitor reduces ColVI expression and ameliorates fibrosis in Fra-2tg mice and in the Bleomycin model. Finally, Fra-2 and ColVI positively correlate in IPF patient samples and co-localize in lung macrophages. Therefore, the Fra-2/ColVI pro-fibrotic axis is a promising biomarker and therapeutic target for lung fibrosis, and possibly other fibrotic diseases.

C-Fos expression is a molecular predictor of progression and survival in epithelial ovarian carcinoma.

Members of the Fos protein family dimerise with Jun proteins to form the AP-1 transcription factor complex. They have a central function in proliferation and differentiation of normal tissue as well as in oncogenic transformation and tumour progression. We analysed the expression of c-Fos, FosB, Fra-1 and Fra-2 to investigate the function of Fos transcription factors in ovarian cancer. A total of 101 patients were included in the study. Expression of Fos proteins was determined by western blot analysis, quantified by densitometry and verified by immunohistochemistry. Reduced c-Fos expression was independently associated with unfavourable progression-free survival (20.6, 31.6 and 51.2 months for patients with low, moderate and high c-Fos expression; P=0.003) as well as overall survival (23.8, 46.0 and 55.5 months for low, moderate and high c-Fos levels; P=0.003). No correlations were observed for FosB, Fra-1 and Fra-2. We conclude that loss of c-Fos expression is associated with tumour progression in ovarian carcinoma and that c-Fos may be a prognostic factor. These results are in contrast to the classic concept of c-Fos as an oncogene, but are supported by the recently discovered tumour-suppressing and proapoptotic function of c-Fos in various cancer types.

MiR-124-3p suppresses glioma aggressiveness via targeting of Fra-2.

Malignant glioma is the most common and deadly primary brain tumor in adults. However, the mechanisms underlying the malignancy of glioma remain unclear. In the present study, we found that Fos-related antigen-2 (Fra-2) was overexpressed in most glioma cells, and knockdown of Fra-2 prevented cell proliferation, migration, and invasion. Mechanistically, Fra-2 silencing led to a significant reduction in cell-cycle drivers (Cyclin D1 and Cyclin E1), one invasion-associated gene (MMP9), the mesenchymal marker (Vimentin), and induction of the epithelial marker (E-cadherin). Further study confirmed that miR-124-3p decreased the expression of Fra-2 via directly targeting the 3'-UTR, and transfection with miR-124-3p in glioma cells inhibited expression of the above cell-cycle and EMT promoters. Phenotypic experiments also showed that overexpression of Fra-2 weakened the inhibitory effects of miR-124-3p on the proliferation, migration, and invasion of glioma cells. In addition, Fra-2 knockdown impaired the malignant phenotypes enhanced by miR-124-3p inhibition, which suggested a crucial role for the miR-124-3p/Fra-2 pathway in glioma development. Consistently, high expression of Fra-2 was closely associated with low miR-124-3p level and indicated a poor prognosis in patients with glioma. In conclusion, this study indicates the existence of an aberrant miR-124-3p/Fra-2 pathway that results in glioma aggressiveness, which suggests novel therapeutic opportunities for this fatal disease.

Fos- and Jun-related transcription factors are involved in the signal transduction pathway of mechanical loading in condylar chondrocytes.

The chondrocytes of the articular condylar cartilage proliferate, hypertrophy and ultimately undergo apoptosis (programmed cell death), being replaced by osteoblasts. Converging results consolidate activator protein-1 (AP-1) transcription factor as the pivotal downstream effector in the early response of stress-sensitive cells to mechanical loading, and the Fra-1, Fra-2, JunB and JunD members of the AP-1 transcription factor family, as mediators in bone remodelling and apoptotic phenomena. The aim of the present study was to examine the involvement of the Fra-1, Fra-2, JunB and JunD proteins in the biochemical response of functionally loaded mandibular condylar cartilage, and the subsequent initiation of cartilage maturation and apoptotic phenomena. Thirty, female, 14-day-old Wistar rats were assigned to two groups: one group was fed a soft diet and the other a hard diet. At day 21 after weaning, experimental animals from both groups were killed at 6, 12 and 48 hours and their condyles harvested. The condylar cartilage of both groups was immunostained using specific antibodies against Fra-1, Fra-2, JunB and JunD. Statistical analysis of the data revealed over-expression of Fra-1, Fra-2, JunB and JunD proteins in all stages of differentiation of chondrocytes derived from the mandibular condylar cartilage of animals fed on a hard diet. Moreover, the involvement of these proteins significantly increased with time in both groups. Since the aforementioned proteins play key roles in remodelling phenomena of bone and cartilage tissue, influencing pivotal cellular functions such as maturation, differentiation and apoptosis, the results of the present study suggest that mandibular condylar chondrocytes sense functional loading changes and respond by induction of proteins associated with biological phenomena that ultimately influence the growth of the condylar cartilage.