BF-1 interferes with transforming growth factor beta signaling by associating with Smad partners

High-density lipoprotein-based nanoplatform reprograms tumor microenvironment and enhances chemotherapy against pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is highly aggressive, with limited success in traditional therapies due to the fibrotic, immunosuppressive, pro-metastatic tumor microenvironment (TME), which collectively impede the drug accumulation and accelerate the tumor progression. In this work, we developed a PDAC-customized nutrient-mimicking reconstituted high-density lipoprotein (rHDL) capable of efficiently co-encapsulate versatile TME regulating cannabidiol and cytotoxic gemcitabine to simultaneously reprogram TME while suppressing PDAC progression. Specifically, a small-sized, nutrient-like rHDL was constructed to realize deep PDAC parenchyma penetration and efficient intra-tumoral uptake. Next, natural herbal compound cannabidiol was screened and incorporated into rHDL to regulate TME via attenuating fibrosis, reliving immunosuppression and mitigating metastatic tendency. At last, gemcitabine, the PDAC gold standard first-line therapy was co-delivered by the PDAC-customized rHDL to overcome drug resistance and amplify its PDAC suppression. Our findings demonstrate the feasibility of an integrated multi-stage TME regulation strategy for improved PDAC therapy, and might represent a modality in promoting chemotherapy against PDAC.

Structure, unique biological properties, and mechanisms of action of transforming growth factor β

Transforming growth factor β (TGF-β) is a ubiquitous molecule that is extremely conserved structurally and plays a systemic role in human organism. TGF-β is a homodimeric molecule consisting of two subunits joined through a disulphide bond. In mammals, three genes code for TGF-β1, TGF-β2, and TGF-β3 isoforms of this cytokine with a dominating expression of TGF-β1. Virtually, all normal cells contain TGF-β and its specific receptors. Considering the exceptional role of fine balance played by the TGF-β in anumber of physiological and pathological processes in human body, this cytokine may be proposed for use in medicine as an immunosuppressant in transplantology, wound healing and bone repair. TGFb itself is an important target in oncology. Strategies for blocking members of TGF-β signaling pathway as therapeutic targets have been considered. In this review, signalling mechanisms of TGF-β1 action are addressed, and their role in physiology and pathology with main focus on carcinogenesis are described.

FOXG1 is involved in mouse ovarian functions and embryogenesis

TGF-β superfamily has long been demonstrated to be essential for folliculogenesis and luteinization. Forkhead box G1 (FOXG1, also known as BF1), a member of the FOX family and an inhibitor of TGF-β signaling pathway, is a nucleocytoplasmic transcription factor that is essential for forebrain development. FOXG1 is involved in neurodevelopment and cancer pathology, however, little is known about the role of FOXG1 in reproduction. In this study, the spatiotemporal expression pattern of FOXG1 was examined during early mouse oocyte and embryonic development and its role during corpora luteum (CL) formation was further elucidated. The results showed that FOXG1 is localized in oocytes, theca cells (TCs) and CLs. After fertilization, FOXG1 is expressed at all stages during early embryogenesis, from zygotes to blastocysts. Following gonadotropin administration in immature mice, the expression of Foxg1 significantly increased along with steroidogenic genes, including Star, Hsd3β, Cyp11a1, as well as Cyp17a1 and Cyp19a1. The latter two first increased after pregnant mare serum gonadotropin stimulation, then decreased in response to hCG treatment. In addition, silencing of Foxg1 significantly reduced the concentration of testosterone and estrogen in cultured primary granulosa cells (GCs) and TCs (P < 0.05). Mechanistic studies demonstrated that the expression level of genes that are critical in estrogen synthesis were significantly reduced after Foxg1 silencing, including Cyp17a1 and Cyp19a1. In conclusion, FOXG1 is expressed in a stage-specific manner during folliculogenesis and embryogenesis and exerts a regulatory influence on testosterone and estrogen synthesis.

FOXG1 regulates the proliferation and apoptosis of human lung cancer cells

FOXG1, a transcriptional factor belonging to the Forkhead Box (Fox) superfamily, is highly expressed in the brain tissue during brain development and plays an important role in cellular proliferation. Recently, FOXG1 was reported to play important roles in oncogenesis, wherein its abnormal expression regulates tumor cell proliferation. However, the expression and role of FOXG1 in lung cancer remain largely unknown. This study investigated the clinical significance, expression, and role of FOXG1 in lung cancer. We found that FOXG1 was highly expressed in lung cancer tissues. MTT, CCK-8 and colony formation assays showed that FOXG1 overexpression could enhance the proliferation of A549 lung cancer cells. Flow cytometry analysis revealed that FOXG1 promoted the cell cycle and suppressed cell apoptosis. Additionally, the expression levels of PTEN, phosphorylated AKT, mTOR, p53, and Bax were significantly altered in response to changes in FOXG1 expression, indicating that FOXG1 regulated the PI3K pathway. Furthermore, in the xenograft mouse model, the upregulated FOXG1 expression strongly promoted tumor growth. In conclusion, these results suggested that FOXG1 was a critical regulator of the proliferation of lung cancer cells and enhanced tumor growth in vivo.

Transcriptional control of embryonic and adult neural progenitor activity

Neural precursors generate neurons in the embryonic brain and in restricted niches of the adult brain in a process called neurogenesis. The precise control of cell proliferation and differentiation in time and space required for neurogenesis depends on sophisticated orchestration of gene transcription in neural precursor cells. Much progress has been made in understanding the transcriptional regulation of neurogenesis, which relies on dose- and context-dependent expression of specific transcription factors that regulate the maintenance and proliferation of neural progenitors, followed by their differentiation into lineage-specified cells. Here, we review some of the most widely studied neurogenic transcription factors in the embryonic cortex and neurogenic niches in the adult brain. We compare functions of these transcription factors in embryonic and adult neurogenesis, highlighting biochemical, developmental, and cell biological properties. Our goal is to present an overview of transcriptional regulation underlying neurogenesis in the developing cerebral cortex and in the adult brain.

FOXG1 targets BMP repressors and cell cycle inhibitors in human neural progenitor cells

FOXG1 is a critical transcription factor in human brain where loss-of-function mutations cause a severe neurodevelopmental disorder, while increased FOXG1 expression is frequently observed in glioblastoma. FOXG1 is an inhibitor of cell patterning and an activator of cell proliferation in chordate model organisms but different mechanisms have been proposed as to how this occurs. To identify genomic targets of FOXG1 in human neural progenitor cells (NPCs), we engineered a cleavable reporter construct in endogenous FOXG1 and performed chromatin immunoprecipitation (ChIP) sequencing. We also performed deep RNA sequencing of NPCs from two females with loss-of-function mutations in FOXG1 and their healthy biological mothers. Integrative analyses of RNA and ChIP sequencing data showed that cell cycle regulation and Bone Morphogenic Protein (BMP) repression gene ontology categories were over-represented as FOXG1 targets. Using engineered brain cell lines, we show that FOXG1 specifically activates SMAD7 and represses CDKN1B. Activation of SMAD7 which inhibits BMP signaling may be one way that FOXG1 patterns the forebrain, while repression of cell cycle regulators such as CDKN1B may be one way that FOXG1 expands the NPC pool to ensure proper brain size. Our data reveal novel mechanisms on how FOXG1 may control forebrain patterning and cell proliferation in human brain development.

FOXG1 dose tunes cell proliferation dynamics in human forebrain progenitor cells

Heterozygous loss-of-function mutations in Forkhead box G1 (FOXG1), a uniquely brain-expressed gene, cause microcephaly, seizures, and severe intellectual disability, whereas increased FOXG1 expression is frequently observed in glioblastoma. To investigate the role of FOXG1 in forebrain cell proliferation, we modeled FOXG1 syndrome using cells from three clinically diagnosed cases with two sex-matched healthy parents and one unrelated sex-matched control. Cells with heterozygous FOXG1 loss showed significant reduction in cell proliferation, increased ratio of cells in G0/G1 stage of the cell cycle, and increased frequency of primary cilia. Engineered loss of FOXG1 recapitulated this effect, while isogenic repair of a patient mutation reverted output markers to wild type. An engineered inducible FOXG1 cell line derived from a FOXG1 syndrome case demonstrated that FOXG1 dose-dependently affects all cell proliferation outputs measured. These findings provide strong support for the critical importance of FOXG1 levels in controlling human brain cell growth in health and disease.

Paving Therapeutic Avenues for FOXG1 Syndrome: Untangling Genotypes and Phenotypes from a Molecular Perspective

Development of the central nervous system (CNS) depends on accurate spatiotemporal control of signaling pathways and transcriptional programs. Forkhead Box G1 (FOXG1) is one of the master regulators that play fundamental roles in forebrain development; from the timing of neurogenesis, to the patterning of the cerebral cortex. Mutations in the FOXG1 gene cause a rare neurodevelopmental disorder called FOXG1 syndrome, also known as congenital form of Rett syndrome. Patients presenting with FOXG1 syndrome manifest a spectrum of phenotypes, ranging from severe cognitive dysfunction and microcephaly to social withdrawal and communication deficits, with varying severities. To develop and improve therapeutic interventions, there has been considerable progress towards unravelling the multi-faceted functions of FOXG1 in the neurodevelopment and pathogenesis of FOXG1 syndrome. Moreover, recent advances in genome editing and stem cell technologies, as well as the increased yield of information from high throughput omics, have opened promising and important new avenues in FOXG1 research. In this review, we provide a summary of the clinical features and emerging molecular mechanisms underlying FOXG1 syndrome, and explore disease-modelling approaches in animals and human-based systems, to highlight the prospects of research and possible clinical interventions.

IDH1 gene mutation activates Smad signaling molecules to regulate the expression levels of cell cycle and biological rhythm genes in human glioma U87‑MG cells

Isocitrate dehydrogenase1 (IDH1) mutation is the most important genetic change in glioma. The most common IDH1 mutation results in the amino acid substitution of arginine 132 (Arg/R132), which is located at the active site of the enzyme. IDH1 Arg132His (R132H) mutation can reduce the proliferative rate of glioma cells. Numerous diseases follow circadian rhythms, and there is growing evidence that circadian disruption may be a risk factor for cancer in humans. Dysregulation of the circadian clock serves an important role in the development of malignant tumors, including glioma. Brain-Muscle Arnt-Like protein 1 (BMAL1) and Circadian Locomotor Output Cycles Kaput (CLOCK) are the main biological rhythm genes. The present study aimed to further study whether there is an association between IDH1 R132H mutation and biological rhythm in glioma, and whether this affects the occurrence of glioma. The Cancer Genome Atlas (TCGA) database was used to detect the expression levels of the biological rhythm genes BMAL1 and CLOCK in various types of tumor. Additionally, U87-MG cells were infected with wild-type and mutant IDH1 lentiviruses. Colony formation experiments were used to detect cell proliferation in each group, cell cycle distribution was detected by flow cytometry and western blotting was used to detect the expression levels of wild-type and mutant IDH1, cyclins, biological rhythm genes and Smad signaling pathway-associated genes in U87-MG cells. TCGA database results suggested that BMAL1 and CLOCK were abnormally expressed in glioma. Cells were successfully infected with wild-type and mutant IDH1 lentiviruses. Colony formation assay revealed decreased cell proliferation in the IDH1 R132H mutant group. The cell cycle distribution detected by flow cytometry indicated that IDH1 gene mutation increased the G₁ phase ratio and decreased the S phase ratio in U87-MG cells. The western blotting results demonstrated that IDH1 R132H mutation decreased the expression levels of the S phase-associated proteins Cyclin A and CDK2, and increased the expression levels of the G₁ phase-associated proteins Cyclin D3 and CDK4, but did not significantly change the expression levels of the G₂/M phase-associated protein Cyclin B1. The expression levels of the positive and negative rhythm regulation genes BMAL1, CLOCK, period (PER s (PER1, 2 and 3) and cryptochrom (CRY)s (CRY1 and 2) were significantly decreased, those of the Smad signaling pathway-associated genes Smad2, Smad3 and Smad2-3 were decreased, and those of phosphorylated (p)-Smad2, p-Smad3 and Smad4 were increased. Therefore, the present results suggested that the IDH1 R132H mutation may alter the cell cycle and biological rhythm genes in U87-MG cells through the TGF-β/Smad signaling pathway.

The Role of FoxG1 in the Inner Ear

Sensorineural deafness is mainly caused by damage to the tissues of the inner ear, and hearing impairment has become an increasingly serious global health problem. When the inner ear is abnormally developed or is damaged by inflammation, ototoxic drugs, or blood supply disorders, auditory signal transmission is inhibited resulting in hearing loss. Forkhead box G1 (FoxG1) is an important nuclear transcriptional regulator, which is related to the differentiation, proliferation, development, and survival of cells in the brain, telencephalon, inner ear, and other tissues. Previous studies have shown that when FoxG1 is abnormally expressed, the development and function of inner ear hair cells is impaired. This review discusses the role and regulatory mechanism of FoxG1 in inner ear tissue from various aspects – such as the effect on inner ear development, the maintenance of inner ear structure and function, and its role in the inner ear when subjected to various stimulations or injuries – in order to explain the potential significance of FoxG1 as a new target for the treatment of hearing loss.

Elucidating the pathogenic and biomarker potentials of FOXG1 in glioblastoma

Glioblastoma (GB) is an extremely pugnacious brain cancer originating from neural stem (NS) cell-like cells. Forkhead box G1 (FOXG1; previously recognized as BF-1, qin, Chicken Brain Factor 1, or XBF-1 and renamed FOXG1 for mouse and human, and FoxG1 for other chordates) is an evolutionary preserved transcription factor driven from the forkhead box group of proteins FOXG1 modulates the speed of neurogenesis by maintaining progenitor cells in a proliferative mode as well as obstructing their differentiation into neurons during the initial periods of cortical formation. FOXG1 has been implicated in the formation of central nervous system (CNS) tumors and precisely GBs. Pathophysiologically, joint actions of FOXG1 and phosphatidylinositol- 3-kinases (PI3K) intermediate in intrinsic resistance of human GB cells to transforming growth factor-beta (TGF-β) stimulation of cyclin-dependent kinase inhibitor 1(p21Cip1) as well as growth inhibition. FOXG1 and NOTCH signaling pathways may functionally interrelate at different stages to facilitate gliomagenesis. Furthermore, FoxG1 actively contributed to the formation of transcription suppression complexes with corepressors of the Groucho/transducin-like Enhancer of split (Gro/TLEs). Also, FOXG1 was stimulated by Gro/TLE1 and abridged by Grg6. FOXG1 silencing in brain tumor-initiating cells (BTICs) also resulted in diminished secretion of markers characteristic undifferentiated natural neural stem/progenitor cells (NSPC) states, such as Oligodendrocyte transcription factor (OLIG2), (sex determining region Y)-box 2. (SOX2) and B lymphoma Mo-MLV insertion region 1 homolog (BMI1). This review therefore focuses on the pathogenic and biomarker potentials of FOXG1 in GB.

Knockdown of Foxg1 in supporting cells increases the trans-differentiation of supporting cells into hair cells in the neonatal mouse cochlea

Foxg1 is one of the forkhead box genes that are involved in morphogenesis, cell fate determination, and proliferation, and Foxg1 was previously reported to be required for morphogenesis of the mammalian inner ear. However, Foxg1 knock-out mice die at birth, and thus the role of Foxg1 in regulating hair cell (HC) regeneration after birth remains unclear. Here we used Sox2CreER/+ Foxg1loxp/loxp mice and Lgr5-EGFPCreER/+ Foxg1loxp/loxp mice to conditionally knock down Foxg1 specifically in Sox2+ SCs and Lgr5+ progenitors, respectively, in neonatal mice. We found that Foxg1 conditional knockdown (cKD) in Sox2+ SCs and Lgr5+ progenitors at postnatal day (P)1 both led to large numbers of extra HCs, especially extra inner HCs (IHCs) at P7, and these extra IHCs with normal hair bundles and synapses could survive at least to P30. The EdU assay failed to detect any EdU+ SCs, while the SC number was significantly decreased in Foxg1 cKD mice, and lineage tracing data showed that much more tdTomato+ HCs originated from Sox2+ SCs in Foxg1 cKD mice compared to the control mice. Moreover, the sphere-forming assay showed that Foxg1 cKD in Lgr5+ progenitors did not significantly change their sphere-forming ability. All these results suggest that Foxg1 cKD promotes HC regeneration and leads to large numbers of extra HCs probably by inducing direct trans-differentiation of SCs and progenitors to HCs. Real-time qPCR showed that cell cycle and Notch signaling pathways were significantly down-regulated in Foxg1 cKD mice cochlear SCs. Together, this study provides new evidence for the role of Foxg1 in regulating HC regeneration from SCs and progenitors in the neonatal mouse cochlea.

Transcription and Beyond: Delineating FOXG1 Function in Cortical Development and Disorders

Forkhead Box G1 (FOXG1) is a member of the Forkhead family of genes with non-redundant roles in brain development, where alteration of this gene's expression significantly affects the formation and function of the mammalian cerebral cortex. FOXG1 haploinsufficiency in humans is associated with prominent differences in brain size and impaired intellectual development noticeable in early childhood, while homozygous mutations are typically fatal. As such, FOXG1 has been implicated in a wide spectrum of congenital brain disorders, including the congenital variant of Rett syndrome, infantile spasms, microcephaly, autism spectrum disorder (ASD) and schizophrenia. Recent technological advances have yielded greater insight into phenotypic variations observed in FOXG1 syndrome, molecular mechanisms underlying pathogenesis of the disease, and multifaceted roles of FOXG1 expression. In this review, we explore the emerging mechanisms of FOXG1 in a range of transcriptional to posttranscriptional events in order to evolve our current view of how a single transcription factor governs the assembly of an elaborate cortical circuit responsible for higher cognitive functions and neurological disorders.

Forkhead box (FOX) G1 promotes hepatocellular carcinoma epithelial-Mesenchymal transition by activating Wnt signal through forming T-cell factor-4/Beta-catenin/FOXG1 complex

Background

Forkhead box G1 (FOXG1) is a member of the Fox transcription factor family involved in regulation of many cancers. However, the role of FOXG1 in hepatocellular carcinogenesisis largely unclear. The present study aimed at examining the biological function and underlying mechanism of FOXG1 on hepatocellular carcinoma (HCC) tumor metastasis as well as its clinical significance.

Methods

Levels of FOXG1 were determined by immunohistochemical and real-time PCR analysis in HCC cell lines and human HCC samples. The effect of FOXG1 on cancer cell invasion and metastasis was investigated in vitro and in vivo in either FOXG1-silenced or overexpressing human HCC cell lines. Immunoprecipitation and chromatin immunoprecipitation assays were performed to investigate the interaction of FOXG1, β-catenin, TCF4 and the effect on Wnt target-gene promoters.

Results

In human HCC, the level of FOXG1 progressively increased from surrounding non tumorous livers to HCC, reaching the highest levels in metastatic HCC. Furthermore, expression levels of FOXG1 directly correlated with cancer cell epithelial-mesenchymal transition (EMT) phenotype. In FOXG1-overexpressing cells, FOXG1 promotes the stabilization and nuclear accumulation of β-catenin by directly binding to β-catenin and it associates with the lymphoid enhancer factor/T cell factor proteins (LEF/TCFs) on Wnt responsive enhancers (WREs) in chromatin.

Conclusions

The results show that FOXG1 plays a key role in mediating cancer cell metastasis through the Wnt/β-catenin pathway in HCC cells and predicts HCC prognosis after surgery. Targeting FOXG1 may provide a new approach for therapeutic treatment in the future.

FOXG1-Related Syndrome: From Clinical to Molecular Genetics and Pathogenic Mechanisms

Individuals with mutations in forkhead box G1 (FOXG1) belong to a distinct clinical entity, termed “FOXG1-related encephalopathy”. There are two clinical phenotypes/syndromes identified in FOXG1-related encephalopathy, duplications and deletions/intragenic mutations. In children with deletions or intragenic mutations of FOXG1, the recognized clinical features include microcephaly, developmental delay, severe cognitive disabilities, early-onset dyskinesia and hyperkinetic movements, stereotypies, epilepsy, and cerebral malformation. In contrast, children with duplications of FOXG1 are typically normocephalic and have normal brain magnetic resonance imaging. They also have different clinical characteristics in terms of epilepsy, movement disorders, and neurodevelopment compared with children with deletions or intragenic mutations. FOXG1 is a transcriptional factor. It is expressed mainly in the telencephalon and plays a pleiotropic role in the development of the brain. It is a key player in development and territorial specification of the anterior brain. In addition, it maintains the expansion of the neural proliferating pool, and also regulates the pace of neocortical neuronogenic progression. It also facilitates cortical layer and corpus callosum formation. Furthermore, it promotes dendrite elongation and maintains neural plasticity, including dendritic arborization and spine densities in mature neurons. In this review, we summarize the clinical features, molecular genetics, and possible pathogenesis of FOXG1-related syndrome.

FOXG1 Dose in Brain Development

Brain development is a highly regulated process that involves the precise spatio-temporal activation of cell signaling cues. Transcription factors play an integral role in this process by relaying information from external signaling cues to the genome. The transcription factor Forkhead box G1 (FOXG1) is expressed in the developing nervous system with a critical role in forebrain development. Altered dosage of FOXG1 due to deletions, duplications, or functional gain- or loss-of-function mutations, leads to a complex array of cellular effects with important consequences for human disease including neurodevelopmental disorders. Here, we review studies in multiple species and cell models where FOXG1 dose is altered. We argue against a linear, symmetrical relationship between FOXG1 dosage states, although FOXG1 levels at the right time and place need to be carefully regulated. Neurodevelopmental disease states caused by mutations in FOXG1 may therefore be regulated through different mechanisms.

FOXG1 Regulates PRKAR2B Transcriptionally and Posttranscriptionally via miR200 in the Adult Hippocampus

Rett syndrome is a complex neurodevelopmental disorder that is mainly caused by mutations in MECP2. However, mutations in FOXG1 cause a less frequent form of atypical Rett syndrome, called FOXG1 syndrome. FOXG1 is a key transcription factor crucial for forebrain development, where it maintains the balance between progenitor proliferation and neuronal differentiation. Using genome-wide small RNA sequencing and quantitative proteomics, we identified that FOXG1 affects the biogenesis of miR200b/a/429 and interacts with the ATP-dependent RNA helicase, DDX5/p68. Both FOXG1 and DDX5 associate with the microprocessor complex, whereby DDX5 recruits FOXG1 to DROSHA. RNA-Seq analyses of Foxg1^cre/+ hippocampi and N2a cells overexpressing miR200 family members identified cAMP-dependent protein kinase type II-beta regulatory subunit (PRKAR2B) as a target of miR200 in neural cells. PRKAR2B inhibits postsynaptic functions by attenuating protein kinase A (PKA) activity; thus, increased PRKAR2B levels may contribute to neuronal dysfunctions in FOXG1 syndrome. Our data suggest that FOXG1 regulates PRKAR2B expression both on transcriptional and posttranscriptional levels.

The role of FOXG1 in the postnatal development and survival of mouse cochlear hair cells

The development of therapeutic interventions for hearing loss requires a detailed understanding of the genes and proteins involved in hearing. The FOXG1 protein plays an important role in early neural development and in a variety of neurodevelopmental disorders. Previous studies have shown that there are severe deformities in the inner ear in Foxg1 knockout mice, but due to the postnatal lethality of Foxg1 knockout mice, the role of FOXG1 in hair cell (HC) development and survival during the postnatal period has not been investigated. In this study, we took advantage of transgenic mice that have a specific knockout of Foxg1 in HCs, thus allowing us to explore the role of FOXG1 in postnatal HC development and survival. In the Foxg1 conditional knockout (CKO) HCs, an extra row of HCs appeared in the apical turn of the cochlea and some parts of the middle turn at postnatal day (P)1 and P7; however, these HCs gradually underwent apoptosis, and the HC number was significantly decreased by P21. Auditory brainstem response tests showed that the Foxg1 CKO mice had lost their hearing by P30. The RNA-Seq results and the qPCR verification both showed that the Wnt, Notch, IGF, EGF, and Hippo signaling pathways were down-regulated in the HCs of Foxg1 CKO mice. The significant down-regulation of the Notch signaling pathway might be the reason for the increased numbers of HCs in the cochleae of Foxg1 CKO mice at P1 and P7, while the down-regulation of the Wnt, IGF, and EGF signaling pathways might lead to subsequent HC apoptosis. Together, these results indicate that knockout of Foxg1 induces an extra row of HCs via Notch signaling inhibition and induces subsequent apoptosis of these HCs by inhibiting the Wnt, IGF, and EGF signaling pathways. This study thus provides new evidence for the function and mechanism of FOXG1 in HC development and survival in mice.

FOXG1 Expression Is Elevated in Glioma and Inhibits Glioma Cell Apoptosis

FOXG1, a member of forkhead family transcriptional factor, is involved in telencephalon development. Recent studies showed FOXG1 was important for a variety of cellular events in cancer cells. In respect to glioma, FOXG1 has been shown to regulate cell proliferation and cell cycles. However, its impacts on other cellular events were not well studied. Here, we found FOXG1 had high expression in clinical glioma tissues, and its expression positively correlated with glioma malignancy. Moreover, we found FOXG1 played roles in glioma cell apoptosis. The expressions of caspase family members were significantly altered in response to change of FOXG1 expression, indicating a direct regulation of FOXG1 on caspase family members. These data strongly suggest FOXG1 is negative regulator of glioma cell apoptosis.

The FOXG1/FOXO/SMAD network balances proliferation and differentiation of cortical progenitors and activates Kcnh3 expression in mature neurons

Transforming growth factor β (TGFβ)-mediated anti-proliferative and differentiating effects promote neuronal differentiation during embryonic central nervous system development. TGFβ downstream signals, composed of activated SMAD2/3, SMAD4 and a FOXO family member, promote the expression of cyclin-dependent kinase inhibitor Cdkn1a. In early CNS development, IGF1/PI3K signaling and the transcription factor FOXG1 inhibit FOXO- and TGFβ-mediated Cdkn1a transcription. FOXG1 prevents cell cycle exit by binding to the SMAD/FOXO-protein complex. In this study we provide further details on the FOXG1/FOXO/SMAD transcription factor network. We identified ligands of the TGFβ- and IGF-family, Foxo1, Foxo3 and Kcnh3 as novel FOXG1-target genes during telencephalic development and showed that FOXG1 interferes with Foxo1 and Tgfβ transcription. Our data specify that FOXO1 activates Cdkn1a transcription. This process is under control of the IGF1-pathway, as Cdkn1a transcription increases when IGF1-signaling is pharmacologically inhibited. However, overexpression of CDKN1A and knockdown of Foxo1 and Foxo3 is not sufficient for neuronal differentiation, which is probably instructed by TGFβ-signaling. In mature neurons, FOXG1 activates transcription of the seizure-related Kcnh3, which might be a FOXG1-target gene involved in the FOXG1 syndrome pathology.

ZIC2 in Holoprosencephaly

The ZIC2 transcription factor is one of the most commonly mutated genes in Holoprosencephaly (HPE) probands. HPE is a severe congenital defect of forebrain development which occurs when the cerebral hemispheres fail to separate during the early stages of organogenesis and is typically associated with mispatterning of the embryonic midline. Recent study of genotype-phenotype correlations in HPE cases has defined distinctive features of ZIC2-associated HPE presentation and genetics, revealing that ZIC2 mutation does not produce the craniofacial abnormalities generally thought to characterise HPE but leads to a range of non-forebrain phenotypes. Furthermore, the studies confirm the extent of ZIC2 allelic heterogeneity and that pathogenic variants of ZIC2 are associated with both classic and middle interhemispheric variant (MIHV) HPE which arise from defective ventral and dorsal forebrain patterning, respectively. An allelic series of mouse mutants has helped to delineate the cellular and molecular mechanisms by which one gene leads to defects in these related but distinct embryological processes.

Foxd1 is an upstream regulator of the renin-angiotensin system during metanephric kidney development

BackgroundWe tested the hypothesis that Foxd1, a transcription factor essential for normal kidney development, is an upstream regulator of the renin-angiotensin system (RAS) during ureteric bud (UB)-branching morphogenesis.MethodsUB branching, RAS gene, and protein expression were studied in embryonic mouse kidneys. RAS mRNA expression was studied in mesenchymal MK4 cells.ResultsThe number of UB tips was reduced in Foxd1^-/- compared with that in Foxd1^+/+ metanephroi on embryonic day E12.5 (14±2.1 vs. 28±1.3, P<0.05). Quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) demonstrated that renin, angiotensin I-converting enzyme (ACE), and angiotensin (Ang) II receptor type 1 (AT₁R) mRNA levels were decreased in Foxd1^-/- compared with those in Foxd1^+/+ E14.5 metanephroi. Western blot analysis and immunohistochemistry showed decreased expression of AGT and renin proteins in Foxd1^-/- metanephroi compared with that in Foxd1^+/+ metanephroi. Foxd1 overexpression in mesenchymal MK4 cells in vitro increased renin, AGT, ACE, and AT₁R mRNA levels. Exogenous Ang II stimulated UB branching equally in whole intact E12.5 Foxd1^-/- and Foxd1^+/+ metanephroi grown ex vivo (+364±21% vs. +336±18%, P=0.42).ConclusionWe conclude that Foxd1 is an upstream positive regulator of RAS during early metanephric development and propose that the cross-talk between Foxd1 and RAS is essential in UB-branching morphogenesis.

Murine pluripotent stem cells with a homozygous knockout of Foxg1 show reduced differentiation towards cortical progenitors in vitro

Foxg1 is a transcription factor critical for the development of the mammalian telencephalon. Foxg1 controls the proliferation of dorsal telencephalon progenitors and the specification of the ventral telencephalon. Homozygous knockout of Foxg1 in mice leads to severe microcephaly, attributed to premature differentiation of telencephalic progenitors, mainly of cortical progenitors. Here, we analyzed the influence of a Foxg1 knockout on differentiation of murine pluripotent stem cells (mPSCs) in an in vitro model of neuronal development. Murine PSCs were prone to neuronal differentiation in embryoid body like culture with minimal medium conditions, based on the intrinsic default of PSCs to develop into cortical progenitors. Differences between Foxg1 wildtype (Foxg1^WT) and knockout (Foxg1^KO) mPSCs were analyzed. Several mPSC lines with homozygous mutations in Foxg1 were produced using the CRISPR/Cas9 system leading to loss of functional domains. Analysis of mRNA expression using quantitative Real-Time (q) PCR revealed that Foxg1^KO mPSCs expressed significantly less mRNA of Foxg1, Emx1, and VGlut1 compared to Foxg1^WT controls, indicating reduced differentiation towards dorsal telencephalic progenitors. However, the size of the derived EB-like structures did not differ between Foxg1^WT and Foxg1^KO mPSCs. These results show that loss of dorsal telencephalic progenitors can be detected using a simple and rapid differentiation protocol. This study is a first hint that this differentiation method can be used to analyze even extreme phenotypes that are lethal in vivo.

Transforming growth factor-β: A therapeutic target for cancer

Transforming growth factor-β (TGF-β) regulates cell growth and differentiation, apoptosis, cell motility, extracellular matrix production, angiogenesis, and cellular immunity. It has a paradoxical role in cancer. In the early stages it inhibits cellular transformation and prevents cancer progression. In later stages TGF-β plays a key role in promoting tumor progression through mainly 3 mechanisms: facilitating epithelial to mesenchymal transition, stimulating angiogenesis and inducing immunosuppression. As a result of its opposing tumor promoting and tumor suppressive abilities, TGF-β and its pathway has represented potential opportunities for drug development and several therapies targeting the TGF-β pathway have been identified. This review focuses on identifying the mechanisms through which TGF-β is involved in tumorigenesis and current therapeutics that are under development.

Derivation of Functional Human Astrocytes from Cerebral Organoids

Astrocytes play a critical role in the development and homeostasis of the central nervous system (CNS). Astrocyte dysfunction results in several neurological and degenerative diseases. However, a major challenge to our understanding of astrocyte physiology and pathology is the restriction of studies to animal models, human post-mortem brain tissues, or samples obtained from invasive surgical procedures. Here, we report a protocol to generate human functional astrocytes from cerebral organoids derived from human pluripotent stem cells. The cellular isolation of cerebral organoids yielded cells that were morphologically and functionally like astrocytes. Immunolabelling and proteomic assays revealed that human organoid-derived astrocytes express the main astrocytic molecular markers, including glutamate transporters, specific enzymes and cytoskeletal proteins. We found that organoid-derived astrocytes strongly supported neuronal survival and neurite outgrowth and responded to ATP through transient calcium wave elevations, which are hallmarks of astrocyte physiology. Additionally, these astrocytes presented similar functional pathways to those isolated from adult human cortex by surgical procedures. This is the first study to provide proteomic and functional analyses of astrocytes isolated from human cerebral organoids. The isolation of these astrocytes holds great potential for the investigation of developmental and evolutionary features of the human brain and provides a useful approach to drug screening and neurodegenerative disease modelling.

FOXG1 expression shows correlation with neuronal differentiation in cerebellar development, aggressive phenotype in medulloblastomas, and survival in a xenograft model of medulloblastoma

FOXG1 is a transcription factor that interacts with multiple signaling pathways and modulates neuronal differentiation in the telencephalon. Dysregulation of FOXG1 expression has been previously reported in medulloblastoma. In this study, we demonstrate a regional specific expression of FOXG1 and its colocalization with Nestin expression in the premigratory mitotically active (outer) layer of the external granular layer of the cerebellum. An inverse expression of the granular precursor cell markers, Math1 and Musashi1, in the inner nonmitotic migratory layer of the external granular layer and in the internal granular layer was observed. Furthermore, modulation of FOXG1 in the medulloblastoma cell line, DAOY, was associated with the induction of neuronal differentiation markers and significant changes in multiple signaling pathways regulating cell proliferation, differentiation, survival, and apoptosis. Additionally, we observed enhanced survival in intracerebellar mice xenografts injected with DAOY cells bearing shFOXG1 constructs versus shLuciferase construct. Overall, these findings suggest that down-modulation of FOXG1 is a prerequisite for the onset of neuronal differentiation during cerebellar development and that a decrease of FOXG1 in medulloblastoma cells offers a survival advantage in mice. We propose that the disruption of signaling pathways that promote mature neuronal differentiation by overexpressed FOXG1 is a contributing event in the neoplastic transformation of cerebellar stem cells.

TGF-β1 promotes cerebral cortex radial glia-astrocyte differentiation in vivo

The major neural stem cell population in the developing cerebral cortex is composed of the radial glial cells, which generate glial cells and neurons. The mechanisms that modulate the maintenance of the radial glia (RG) stem cell phenotype, or its differentiation, are not yet completely understood. We previously demonstrated that the transforming growth factor-β1 (TGF-β1) promotes RG differentiation into astrocytes in vitro (Glia 2007; 55:1023-33) through activation of multiple canonical and non-canonical signaling pathways (Dev Neurosci 2012; 34:68-81). However, it remains unknown if TGF-β1 acts in RG-astrocyte differentiation in vivo. Here, we addressed the astrogliogenesis induced by TGF-β1 by using the intraventricular in utero injection in vivo approach. We show that injection of TGF-β1 in the lateral ventricles of E14,5 mice embryos resulted in RG fibers disorganization and premature gliogenesis, evidenced by appearance of GFAP positive cells in the cortical wall. These events were followed by decreased numbers of neurons in the cortical plate (CP). Together, we also described that TGF-β1 actions are region-dependent, once RG cells from dorsal region of the cerebral cortex demonstrated to be more responsive to this cytokine compared with RG from lateral cortex either in vitro as well as in vivo. Our work demonstrated that TGF-β1 is a critical cytokine that regulates RG fate decision and differentiation into astrocytes in vitro and in vivo. We also suggest that RG cells are heterogeneous population that acts as distinct targets of TGF-β1 during cerebral cortex development.

Molecular and functional definition of the developing human striatum

The complexity of the human brain derives from the intricate interplay of molecular instructions during development. Here we systematically investigated gene expression changes in the prenatal human striatum and cerebral cortex during development from post-conception weeks 2 to 20. We identified tissue-specific gene coexpression networks, differentially expressed genes and a minimal set of bimodal genes, including those encoding transcription factors, that distinguished striatal from neocortical identities. Unexpected differences from mouse striatal development were discovered. We monitored 36 determinants at the protein level, revealing regional domains of expression and their refinement, during striatal development. We electrophysiologically profiled human striatal neurons differentiated in vitro and determined their refined molecular and functional properties. These results provide a resource and opportunity to gain global understanding of how transcriptional and functional processes converge to specify human striatal and neocortical neurons during development.

Electroacupuncture Analgesia Is Improved by Adenoviral Gene Transfer of Dopamine Beta-hydroxylase into the Hypothalamus of Rats

Electroacupuncture (EA) is a modified form of acupuncture that utilizes electrical stimulation. We previously showed that EA stimulated rats were divided into responders that were sensitive to EA and non-responders that were insensitive to EA based on the tail flick latency (TFL) test. The dopamine beta-hydroxylase (DBH) gene was more abundantly expressed in the hypothalamus of responder rats than non-responder rats. To determine whether overexpression of DBH gene expression in the hypothalamus modulate EA analgesia, we constructed a DBH encoding adenovirus and which was then injected into the hypothalamus of SD rats. Microinjection of DBH or control GFP virus into the hypothalamus had no changes on the basal pain threshold measured by a TFL test without EA treatment. However, the analgesic effect of EA was significantly enhanced from seven days after microinjection of the DBH virus, but not after injection of the control GFP virus. DBH expression was significantly higher in the hypothalamus of DBH virus injected rat than control GFP virus or PBS injected rats. Moreover, expression of the DBH gene did not affect the body core temperature, body weight, motor function or learning and memory ability. Although the functional role of DBH in the hypothalamus in the analgesic effect of EA remains unclear, our findings suggest that expression of the DBH gene in the hypothalamus promotes EA analgesia without obvious side-effects.

Smad4 and Trim33/Tif1γ redundantly regulate neural stem cells in the developing cortex

During central nervous system (CNS) development, proliferation and differentiation of neural stem cells (NSCs) have to be regulated in a spatio-temporal fashion. Here, we report different branches of the transforming growth factor β (TGFβ) signaling pathway to be required for the brain area-specific control of NSCs. In the midbrain, canonical TGFβ signaling via Smad4 regulates the balance between proliferation and differentiation of NSCs. Accordingly, Smad4 deletion resulted in horizontal expansion of NSCs due to increased proliferation, decreased differentiation, and decreased cell cycle exit. In the developing cortex, however, ablation of Smad4 alone did not have any effect on proliferation and differentiation of NSCs. In contrast, concomitant mutation of both Smad4 and Trim33 led to an increase in proliferative cells in the ventricular zone due to decreased cell cycle exit, revealing a functional redundancy of Smad4 and Trim33. Furthermore, in Smad4-Trim33 double mutant embryos, cortical NSCs generated an excess of deep layer neurons concurrent with a delayed and reduced production of upper layer neurons and, in addition, failed to undergo the neurogenic to gliogenic switch at the right developmental stage. Thus, our data disclose that in different regions of the developing CNS different aspects of the TGFβ signaling pathway are required to ensure proper development.

Foxg1 is required to limit the formation of ciliary margin tissue and Wnt/β-catenin signalling in the developing nasal retina of the mouse

The ciliary margin (CM) develops in the peripheral retina and gives rise to the iris and the ciliary body. The Wnt/β-catenin signalling pathway has been implicated in ciliary margin development. Here, we tested the hypothesis that in the developing mouse retina Foxg1 is responsible for suppressing the Wnt/β-catenin pathway and restricting CM development. We showed that there is excess CM tissue in Foxg1^−/− null embryos and this expansion is more pronounced in the nasal retina where Foxg1 normally shows its highest expression levels. Results on expression of a reporter allele for Wnt/β-catenin signalling and of Lef1, a target of Wnt/β-catenin signalling, displayed significant upregulation of this pathway in Foxg1^−/− nulls at embryonic days 12.5 and 14.5. Interestingly, this upregulation was observed specifically in the nasal retina, where normally very few Wnt-responsive cells are observed. These results indicate a suppressive role of Foxg1 on this signalling pathway. Our results reveal a new role of Foxg1 in limiting CM development in the nasal peripheral retina and add a new molecular player in the developmental network involved in CM specification.

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Foxg1 is expressed in a nasal-high to temporal-low gradient in developing retina.

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Ciliary margin expansion is observed nasally in the Foxg1^−/− mutant retina.

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Wnt/β-catenin signalling is upregulated in the Foxg1^−/− peripheral retina nasally.

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A new role of Foxg1 in controlling ciliary margin development is proposed.

Foxg1 coordinates the switch from nonradially to radially migrating glutamatergic subtypes in the neocortex through spatiotemporal repression

The specification of neuronal subtypes in the cerebral cortex proceeds in a temporal manner; however, the regulation of the transitions between the sequentially generated subtypes is poorly understood. Here, we report that the forkhead box transcription factor Foxg1 coordinates the production of neocortical projection neurons through the global repression of a default gene program. The delayed activation of Foxg1 was necessary and sufficient to induce deep-layer neurogenesis, followed by a sequential wave of upper-layer neurogenesis. A genome-wide analysis revealed that Foxg1 binds to mammalian-specific noncoding sequences to repress over 12 transcription factors expressed in early progenitors, including Ebf2/3, Dmrt3, Dmrta1, and Eya2. These findings reveal an unexpected prolonged competence of progenitors to initiate corticogenesis at a progressed stage during development and identify Foxg1 as a critical initiator of neocorticogenesis through spatiotemporal repression, a system that balances the production of nonradially and radially migrating glutamatergic subtypes during mammalian cortical expansion.

Annual Research Review: Development of the cerebral cortex: implications for neurodevelopmental disorders

The cerebral cortex has a central role in cognitive and emotional processing. As such, understanding the mechanisms that govern its development and function will be central to understanding the bases of severe neuropsychiatric disorders, particularly those that first appear in childhood. In this review, I highlight recent progress in elucidating genetic, molecular and cellular mechanisms that control cortical development. I discuss basic aspects of cortical developmental anatomy, and mechanisms that regulate cortical size and area formation, with an emphasis on the roles of fibroblast growth factor (Fgf) signaling and specific transcription factors. I then examine how specific types of cortical excitatory projection neurons are generated, and how their axons grow along stereotyped pathways to their targets. Next, I address how cortical inhibitory (GABAergic) neurons are generated, and point out the role of these cells in controlling cortical plasticity and critical periods. The paper concludes with an examination of four possible developmental mechanisms that could contribute to some forms of neurodevelopmental disorders, such as autism.

FoxG1 promotes the survival of postmitotic neurons

The transcription factor FoxG1 regulates neurogenesis in the embryonic telencephalon as well as a number of other neurodevelopmental processes. While FoxG1 continues to be expressed in neurons postnatally and through adulthood, its role in fully differentiated neurons is not known. The current study demonstrates that FoxG1 promotes the survival of postmitotic neurons. In cerebellar granule neurons primed to undergo apoptosis, FoxG1 expression is reduced. Ectopic expression of FoxG1 blocks neuronal death, whereas suppression of its expression induces death in otherwise healthy neurons. The first 36 residues of FoxG1 are necessary for its survival-promoting effect, while the C-terminal half of the protein is dispensable. Mutation of Asp219, a residue necessary for DNA binding, abrogates survival promotion by FoxG1. Survival promotion is also eliminated by mutation of Thr271, a residue phosphorylated by Akt. Pharmacological inhibition of Akt blocks the survival effects of wild-type FoxG1 but not forms in which Thr271 is replaced with phosphomimetic residues. Treatment of neurons with IGF-1, a neurotrophic factor that promotes neuronal survival by activating Akt, prevents the apoptosis-associated downregulation of FoxG1 expression. Moreover, the overexpression of dominant-negative forms of FoxG1 blocks the ability of IGF-1 to maintain neuronal survival suggesting that FoxG1 is a downstream mediator of IGF-1/Akt signaling. Our study identifies a new and important function for FoxG1 in differentiated neurons.

FoxG1 and TLE2 act cooperatively to regulate ventral telencephalon formation

FoxG1 is a conserved transcriptional repressor that plays a key role in the specification, proliferation and differentiation of the telencephalon, and is expressed from the earliest stages of telencephalic development through to the adult. How the interaction with co-factors might influence the multiplicity and diversity of FoxG1 function is not known. Here, we show that interaction of FoxG1 with TLE2, a Xenopus tropicalis co-repressor of the Groucho/TLE family, is crucial for regulating the early activity of FoxG1. We show that TLE2 is co-expressed with FoxG1 in the ventral telencephalon from the early neural plate stage and functionally cooperates with FoxG1 in an ectopic neurogenesis assay. FoxG1 has two potential TLE binding sites: an N-terminal eh1 motif and a C-terminal YWPMSPF motif. Although direct binding seems to be mediated by the N-terminal motif, both motifs appear important for functional synergism. In the neurogenesis assay, mutation of either motif abolishes functional cooperation of TLE2 with FoxG1, whereas in the forebrain deletion of both motifs renders FoxG1 unable to induce the ventral telencephalic marker Nkx2.1. Knocking down either FoxG1 or TLE2 disrupts the development of the ventral telencephalon, supporting the idea that endogenous TLE2 and FoxG1 work together to specify the ventral telencephalon.

Altered response to antidepressant treatment in FoxG1 heterozygous knockout mice

Evidence from a variety of sources suggests that structural alterations in the brain, including neurogenesis, may play a role in both the pathogenesis of mood disorders and the mechanism of action of antidepressants. Previous studies have implicated both the transforming growth factor-beta (TGF-beta), and the phosphatidyl inositol-3 kinase (PI3K)-Akt pathways in the neurogenesis-promoting and behavioral properties of antidepressants. Forkhead box protein G1 (FoxG1) is a major regulator of both of these pathways, and FoxG1 heterozygous null mice (FoxG1+/-) have previously been reported to have deficits in adult hippocampal neurogenesis and behavioral abnormalities including deficits in contextual fear learning. However the role of FoxG1, if any, in the response to antidepressants has not been previously investigated.To investigate the role of the FoxG1 gene in the behavioral and neurogenic properties of antidepressants, we tested FoxG1+/- mice and littermate controls in two different rodent models of antidepressant action: the tail suspension test and the forced swim test. FoxG1+/- mice showed no response to antidepressants in either of these tests. These results suggest that normal levels of FoxG1 may be required for the behavioral response to antidepressants.

The role of foxg1 in the development of neural stem cells of the olfactory epithelium

The olfactory epithelium (OE) of the mouse is an excellent model system for studying principles of neural stem cell biology because of its well-defined neuronal lineage and its ability to regenerate throughout life. To approach the molecular mechanisms of stem cell regulation in the OE, we have focused on Foxg1, also known as brain factor 1, which is a member of the Forkhead transcription factor family. Foxg1(-/-) mice show major defects in the OE at birth, suggesting that Foxg1 plays an important role in OE development. We find that Foxg1 is expressed in cells within the basal compartment of the OE, the location where OE stem and progenitor cells are known to reside. Since FoxG1 is known to regulate proliferation of neuronal progenitor cells during telencephalon development, we performed bromodeoxyuridine pulse-chase labeling of Sox2-expressing neural stem cells during primary OE neurogenesis. We found the percentage of Sox2-expressing cells that retained bromodeoxyuridine was twice as high in Foxg1(-/-) OE cells as in the wild type, suggesting that these cells are delayed and/or halted in their development in the absence of Foxg1. Our findings suggest that the proliferation and/or subsequent differentiation of Sox2-expressing neural stem cells in the OE is regulated by Foxg1.

Overexpression of FOXG1 contributes to TGF-beta resistance through inhibition of p21WAF1/CIP1 expression in ovarian cancer

Background:

Loss of growth inhibitory response to transforming growth factor-β (TGF-β) is a common feature of epithelial cancers. Recent studies have reported that genetic lesions and overexpression of oncoproteins in TGF-β/Smads signalling cascade contribute to the TGF-β resistance. Here, we showed that the overexpressed FOXG1 was involved in attenuating the anti-proliferative control of TGF-β/Smads signalling in ovarian cancer.

Methods:

FOXG1 and p21^WAF1/CIP1 expressions were evaluated by real-time quantitative reverse-transcription polymerase chain reaction (RT–PCR), western blot and immunohistochemical analyses. The effect of FOXG1 on p21^WAF1/CIP1 transcriptional activity was examined by luciferase reporter assays. Cell lines stably expressing or short hairpin RNA interference-mediated knockdown FOXG1 were established for studying the gain-or-loss functional effects of FOXG1. XTT cell proliferation assay was used to measure cell growth of ovarian cancer cells.

Results:

Quantitative RT–PCR and western blot analyses showed that FOXG1 was upregulated and inversely associated with the expression levels of p21^WAF1/CIP1 in ovarian cancer. The overexpression of FOXG1 was significantly correlated with high-grade ovarian cancer (P=0.025). Immunohistochemical analysis on ovarian cancer tissue array was further evidenced that FOXG1 was highly expressed and significantly correlated with high-grade ovarian cancer (P=0.048). Functionally, enforced expression of FOXG1 selectively blocked the TGF-β-induced p21^WAF1/CIP1 expressions and increased cell proliferation in ovarian cancer cells. Conversely, FOXG1 knockdown resulted in a 20–26% decrease in cell proliferation together with 16–33% increase in p21^WAF1/CIP1 expression. Notably, FOXG1 was able to inhibit the p21^WAF1/CIP1 promoter activity in a p53-independent manner by transient reporter assays.

Conclusion

Our results suggest that FOXG1 acts as an oncoprotein inhibiting TGF-β-mediated anti-proliferative responses in ovarian cancer cells through suppressing p21^WAF1/CIP1 transcription.

Reducing betaglycan expression by RNA interference (RNAi) attenuates inhibin bioactivity in LbetaT2 gonadotropes

Betaglycan is an inhibin-binding protein co-receptor, the forced expression of which confers inhibin responsiveness on cells previously non-responsive to inhibin. The present study determines whether removal of betaglycan expression in otherwise inhibin-responsive cells will render the cells insensitive to inhibin. Small interfering RNAs (siRNAs) designed to the betaglycan gene were transfected into LbetaT2 gonadotrope cells to 'knock-down' betaglycan expression. To control for non-specific effects, siRNAs corresponding to an unrelated sequence (BF-1) were used. Two activin-responsive promoter constructs were used to assess inhibin bioactivity; an ovine FSHbeta promoter (oFSHbeta-lux), and a construct containing three copies of the activin-responsive sequence from the GnRHR promoter (3XpGRAS-PRL-lux). Activin stimulated the activity of both promoters 5-8-fold. Inhibin suppressed these activin-stimulated promoter activities by 52+/-11% and 51+/-7%, respectively. Similar inhibin suppression was also seen for cells co-transfected with the control BF-1 siRNAs. In contrast, inhibin's ability to suppress activin-stimulated activity was significantly reduced (33+/-3%, p<0.005 and 24+/-4%, p<0.045, respectively) in cells co-transfected with betaglycan siRNAs. These results demonstrated that endocrine effects of inhibin as a negative feedback controller of FSH production in gonadotropes are dependent on betaglycan expression.

Integration of telencephalic Wnt and hedgehog signaling center activities by Foxg1

The forebrain is patterned along the dorsoventral (DV) axis by Sonic Hedgehog (Shh). However, previous studies have suggested the presence of an Shh-independent mechanism. Our study identifies Wnt/beta-catenin-activated from the telencephalic roof-as an Shh-independent pathway that is essential for telencephalic pallial (dorsal) specification during neurulation. We demonstrate that the transcription factor Foxg1 coordinates the activity of two signaling centers: Foxg1 is a key downstream effector of the Shh pathway during induction of subpallial (ventral) identity, and it inhibits Wnt/beta-catenin signaling through direct transcriptional repression of Wnt ligands. This inhibition restricts the dorsal Wnt signaling center to the roof plate and consequently limits pallial identities. Concomitantly to these roles, Foxg1 controls the formation of the compartment boundary between telencephalon and basal diencephalon. Altogether, these findings identify a key direct target of Foxg1, and uncover a simple molecular mechanism by which Foxg1 integrates two opposing signaling centers.

Foxg1 promotes olfactory neurogenesis by antagonizing Gdf11

Foxg1, a winged-helix transcription factor, promotes the development of anterior neural structures; in mice lacking Foxg1, development of the cerebral hemispheres and olfactory epithelium (OE) is severely reduced. It has been suggested that Foxg1 acts by positively regulating the expression of growth factors, such as Fgf8, which support neurogenesis. However, Foxg1 also binds Smad transcriptional complexes, allowing it to negatively regulate the effects of TGFbeta family ligands. Here, we provide evidence that this latter effect explains much of the ability of Foxg1 to drive neurogenesis in the OE. We show that Foxg1 is expressed in developing OE at the same time as the gene encoding growth differentiation factor 11 (Gdf11), a TGFbeta family member that mediates negative-feedback control of OE neurogenesis. Mutations in Gdf11 rescue, to a considerable degree, the major defects in Foxg1(-/-) OE, including the early, severe loss of neural precursors and olfactory receptor neurons, and the subsequent collapse of both neurogenesis and nasal cavity formation. Rescue is gene-dosage dependent, with loss of even one allele of Gdf11 restoring substantial neurogenesis. Notably, we find no evidence for a disruption of Fgf8 expression in Foxg1(-/-) OE. However, we do observe both a failure of expression of follistatin (Fst), which encodes a secreted Gdf11 antagonist normally expressed in and around OE, and an increase in the expression of Gdf11 itself within the remaining OE in these mutants. Fst expression is rescued in Foxg1(-/-);Gdf11(-/-) and Foxg1(-/-);Gdf11(+/-) mice. These data suggest that the influence of Foxg1 on Gdf11-mediated negative feedback of neurogenesis may be both direct and indirect. In addition, defects in development of the cerebral hemispheres in Foxg1(-/-) mice are not rescued by mutations in Gdf11, nor is Gdf11 expressed at high levels within these structures. Thus, the pro-neurogenic effects of Foxg1 are likely to be mediated through different signaling pathways in different parts of the nervous system.

Adenomatous polyposis coli is required for early events in the normal growth and differentiation of the developing cerebral cortex

Background

Adenomatous polyposis coli (Apc) is a large multifunctional protein known to be important for Wnt/β-catenin signalling, cytoskeletal dynamics, and cell polarity. In the developing cerebral cortex, Apc is expressed in proliferating cells and its expression increases as cells migrate to the cortical plate. We examined the consequences of loss of Apc function for the early development of the cerebral cortex.

Results

We used Emx1^Cre to inactivate Apc specifically in proliferating cerebral cortical cells and their descendents starting from embryonic day 9.5. We observed reduction in the size of the mutant cerebral cortex, disruption to its organisation, and changes in the molecular identity of its cells. Loss of Apc leads to a decrease in the size of the proliferative pool, disrupted interkinetic nuclear migration, and increased apoptosis. β-Catenin, pericentrin, and N-cadherin proteins no longer adopt their normal high concentration at the apical surface of the cerebral cortical ventricular zone, indicating that cell polarity is disrupted. Consistent with enhanced Wnt/β-catenin signalling resulting from loss of Apc we found increased levels of TCF/LEF-dependent transcription and expression of endogenous Wnt/β-catenin target genes (Axin2 (conductin), Lef1, and c-myc) in the mutant cerebral cortex. In the Apc mutant cerebral cortex the expression of transcription factors Foxg1, Pax6, Tbr1, and Tbr2 is drastically reduced compared to normal and many cells ectopically express Pax3, Wnt1, and Wt1 (but not Wnt2b, Wnt8b, Ptc, Gli1, Mash1, Olig2, or Islet1). This indicates that loss of Apc function causes cerebral cortical cells to lose their normal identity and redirect to fates normally found in more posterior-dorsal regions of the central nervous system.

Conclusion

Apc is required for multiple aspects of early cerebral cortical development, including the regulation of cell number, interkinetic nuclear migration, cell polarity, and cell type specification.

Adenoviral gene transfer of acetylcholinesterase T subunit in the hypothalamus potentiates electroacupuncture analgesia in rats

Our previous studies, using cDNA microarray and real-time reverse transcription-polymerase chain reaction, showed that acetylcholinesterase T subunit (AChET) gene was more abundantly expressed in the hypothalamus of the responder rats that were sensitive to electroacupuncture (EA) in the tail flick latency (TFL) test than in that of the non-responder rats that were insensitive to EA. In this study, we hypothesized that the expression of the AChET gene in the hypothalamus modulates EA analgesia in rats. To explore the hypothesis, we constructed an AChET-encoding adenovirus and a control virus expressing only green fluorescence protein, either of which was then injected into the hypothalamus of Sprague-Dawley rats. The hypothalamic activity of acetylcholinesterase was significantly higher in rats that were injected with the AChET virus than in rats that were injected with the control virus. The basal pain threshold measured by a TFL test was not changed by microinjection of AChET or control virus into the hypothalamus when EA treatment was not conducted. However, the analgesic effect of EA was significantly enhanced from 7 days after microinjection of the AChET virus into the hypothalamus but not after injection of the control virus. Furthermore, expression of the AChET in the hypothalamus did not affect body core temperature, body weight, motor function or learning and memory ability. Taken together, these results suggest that adenoviral expression of the AChET gene in the hypothalamus potentiates EA analgesia in rats without apparent side-effects.

Cross-talk between MCP-3 and TGFbeta promotes fibroblast collagen biosynthesis

Recent studies have demonstrated upregulation of monocyte chemoattractant protein-3 (MCP-3/CCL7) in fibrosis and have suggested that in addition to a major role in regulating leucocyte recruitment this chemokine may also promote extracellular matrix (ECM) overproduction by fibroblasts. In the present study we explore interplay between MCP-3 and transforming growth factor beta (TGFbeta), a potent profibrotic cytokine. We demonstrate that MCP-3 promotes activation of TGFbeta signalling pathways leading to increased type I collagen secretion. In addition we show that MCP-3 gene expression is stimulated by recombinant TGFbeta1, raising the possibility for synergy between these two mediators in the fibrotic microenvironment. Comparison of downstream signalling pathways that regulate collagen gene activation by both cytokines confirms the central role of MAPK pathway activation in mediating the effects of both factors. An additive effect of these two agonists was demonstrated by comparative microarray analysis for key TGFbeta regulated transcripts including PAI-1, OSF2 and IGFBP6. Together, our results confirm cross-talk between MCP-3 and TGFbeta that may be critical in the development of fibrosis.

Foxg1 haploinsufficiency reduces the population of cortical intermediate progenitor cells: effect of increased p21 expression

Foxg1 is a transcription factor that is critical for forebrain development. Foxg1(+/Cre) mice were used to test the hypotheses 1) that the subventricular zone (SZ) generates supragranular neurons, 2) that Foxg1-regulated activities define the output from the SZ, and 3) that Foxg1 is involved in the suppression of p21-initiated cell-cycle exit. Foxg1(+/Cre) mice have thinner neocortices than wild-type controls, specifically in the supragranular layers, as detected by Brn2 immunostaining. Cell proliferation in the ventricular zone (VZ) and SZ was examined to investigate the reduction in upper layer neurons. The number of cycling VZ cells was similar in Foxg1(+/+) and Foxg1(+/Cre) brains. Interestingly, cell proliferation in the SZ and intermediate progenitor cell (IPC) production (noted by Tbr2-immunostaining) was reduced in Foxg1(+/Cre) brains. These decreases coincided with increased expression of the cell-cycle inhibitor p21 in the VZ and SZ. Furthermore, colocalization of p21 with markers of cell proliferation and IPCs indicated that p21 was temporally expressed to influence the proliferative fate of IPCs. Thus, the present data are consistent with the above hypotheses, particularly, that during corticogenesis, Foxg1-regulated activities enable the expansion of the IPC population likely through suppression of p21-dependent cell-cycle exit.

Foxg1 is required for development of the vertebrate olfactory system

Illuminating the molecular identity and regulation of early progenitor cells in the olfactory sensory epithelium represents an important challenge in the field of neural development. We show in both mouse and zebrafish that the winged helix transcription factor Foxg1 is expressed in an early progenitor population of the olfactory placode. In the mouse, Foxg1 is first expressed throughout the olfactory placode but later becomes restricted to the ventrolateral olfactory epithelium. The essential role of Foxg1 in olfactory development is demonstrated by the strikingly severe phenotype of Foxg1 knock-out mice: older embryos have no recognizable olfactory structures, including epithelium, bulb, or vomeronasal organs. Initially, a small number of olfactory progenitors are specified but show defects in both proliferation and differentiation. Similarly, antisense RNA knockdown of Foxg1 expression in the zebrafish shows a reduction in the number of neurons and mitotic cells in olfactory rosettes, mirroring the phenotype seen in the mouse Foxg1 null mutant. Using mosaic analysis in the zebrafish, we show that Foxg1 is required cell-autonomously for the production of mature olfactory receptor neurons. Therefore, we identified an evolutionarily conserved requirement for Foxg1 in the development of the vertebrate olfactory system.