POU domain factors in the neuroendocrine system: lessons from developmental biology provide insights into human disease

POU6F2 mutation in humans with pubertal failure alters GnRH transcript expression

Idiopathic hypogonadotropic hypogonadism (IHH) is characterized by the absence of pubertal development and subsequent impaired fertility often due to gonadotropin-releasing hormone (GnRH) deficits. Exome sequencing of two independent cohorts of IHH patients identified 12 rare missense variants in POU6F2 in 15 patients. POU6F2 encodes two distinct isoforms. In the adult mouse, expression of both isoform1 and isoform2 was detected in the brain, pituitary, and gonads. However, only isoform1 was detected in mouse primary GnRH cells and three immortalized GnRH cell lines, two mouse and one human. To date, the function of isoform2 has been verified as a transcription factor, while the function of isoform1 has been unknown. In the present report, bioinformatics and cell assays on a human-derived GnRH cell line reveal a novel function for isoform1, demonstrating it can act as a transcriptional regulator, decreasing GNRH1 expression. In addition, the impact of the two most prevalent POU6F2 variants, identified in five IHH patients, that were located at/or close to the DNA-binding domain was examined. Notably, one of these mutations prevented the repression of GnRH transcripts by isoform1. Normally, GnRH transcription increases as GnRH cells mature as they near migrate into the brain. Augmentation earlier during development can disrupt normal GnRH cell migration, consistent with some POU6F2 variants contributing to the IHH pathogenesis.

Microfibril-associated protein 2 is activated by POU class 2 homeobox 1 and promotes tumor growth and metastasis in tongue squamous cell carcinoma

Tongue squamous cell carcinoma (TSCC) represents the most frequent malignancy of the oral cavity, characterized by a high metastasis rate and poor prognosis. Microfibril-associated protein 2 (MFAP2), as an extracellular matrix protein, has been found to drive tumor progression. The function and underlying mechanism of MFAP2 in TSCC remain unknown. The expression levels of MFAP2 were analyzed in tissue samples from 30 TSCC patients by real time-polymerase chain reaction and western blot assays. Our results revealed that the expression of MFAP2 mRNA and protein was upregulated in TSCC tissue samples compared with that in the matched para-carcinoma tissue samples. By performing in vitro gain-of-function or loss-of-function experiments and in vivo mouse xenograft experiments, we found that overexpression of MFAP2 induced proliferation and promoted transition from G1 to S phase of TSCC cells. Stronger invasive and migratory capabilities were observed in MFAP2-overexpressing TSCC cells. In contrast, knockdown of MFAP2 exhibited anti-proliferative, apoptosis-promoting and pro-migratory roles in TSCC cells. Knockdown of MFAP2 significantly inhibited xenograft tumor growth. Mechanistically, POU class 2 homeobox 1 (POU2F1) was recruited to the region of MFAP2 promoter and upregulates the expression of MFAP2. Silencing of MFAP2 effectively blocked the proliferation, migration, and invasion of TSCC cells caused by POU2F1 overexpression. Our results indicate that the role of MFAP2 in TSCC may attribute to transcriptional regulation of POU2F1.

Role of transcription factors and chromatin modifiers in driving lineage reprogramming in treatment-induced neuroendocrine prostate cancer

Therapy-induced neuroendocrine prostate cancer (NEPC) is a highly lethal variant of prostate cancer that is increasing in incidence with the increased use of next-generation of androgen receptor (AR) pathway inhibitors. It arises via a reversible trans-differentiation process, referred to as neuroendocrine differentiation (NED), wherein prostate cancer cells show decreased expression of AR and increased expression of neuroendocrine (NE) lineage markers including enolase 2 (ENO2), chromogranin A (CHGA) and synaptophysin (SYP). NEPC is associated with poor survival rates as these tumors are aggressive and often metastasize to soft tissues such as liver, lung and central nervous system despite low serum PSA levels relative to disease burden. It has been recognized that therapy-induced NED involves a series of genetic and epigenetic alterations that act in a highly concerted manner in orchestrating lineage switching. In the recent years, we have seen a spurt in research in this area that has implicated a host of transcription factors and epigenetic modifiers that play a role in driving this lineage switching. In this article, we review the role of important transcription factors and chromatin modifiers that are instrumental in lineage reprogramming of prostate adenocarcinomas to NEPC under the selective pressure of various AR-targeted therapies. With an increased understanding of the temporal and spatial interplay of transcription factors and chromatin modifiers and their associated gene expression programs in NEPC, better therapeutic strategies are being tested for targeting NEPC effectively.

POU-M2 promotes juvenile hormone biosynthesis by directly activating the transcription of juvenile hormone synthetic enzyme genes in Bombyx mori

Juvenile hormone (JH) plays a key role in preventing larval precocious metamorphosis, maintaining larval state, controlling adult sexual development and promoting insect egg maturation. Genetic studies have shown that POU factor ventral veins lacking regulates JH synthesis to control the timing of insect metamorphosis. However, how POU factor regulates JH synthesis is largely unknown. Here, we found POU-M2 was highly expressed in corpora allata (CA) and specifically localized in the nucleus of CA. The overexpression of POU-M2 promoted the expression of JH synthase genes and kr-h1 and enhanced the activity of JH synthase genes promoter. Further, POU-M2 promoted the transcription of JH acid O-methyltransferase (JHAMT) by directly binding to the key cis-regulatory elements -207, -249 and -453 within the proximal regions of JHAMT promoter. Both the POU domain and homeodomain were vital for the activation of POU-M2 on JHAMT transcription. Our study reveals the mechanism by which POU-M2 regulates JHAMT transcription.

Autophagy: A Novel Horizon for Hair Cell Protection

As a general sensory disorder, hearing loss was a major concern worldwide. Autophagy is a common cellular reaction to stress that degrades cytoplasmic waste through the lysosome pathway. Autophagy not only plays major roles in maintaining intracellular homeostasis but is also involved in the development and pathogenesis of many diseases. In the auditory system, several studies revealed the link between autophagy and hearing protection. In this review, we aimed to establish the correlation between autophagy and hair cells (HCs) from the aspects of ototoxic drugs, aging, and acoustic trauma and discussed whether autophagy could serve as a potential measure in the protection of HCs.

POU1F1 transcription factor induces metabolic reprogramming and breast cancer progression via LDHA regulation

Metabolic reprogramming is considered hallmarks of cancer. Aerobic glycolysis in tumors cells has been well-known for almost a century, but specific factors that regulate lactate generation and the effects of lactate in both cancer cells and stroma are not yet well understood. In the present study using breast cancer cell lines, human primary cultures of breast tumors, and immune deficient murine models, we demonstrate that the POU1F1 transcription factor is functionally and clinically related to both metabolic reprogramming in breast cancer cells and fibroblasts activation. Mechanistically, we demonstrate that POU1F1 transcriptionally regulates the lactate dehydrogenase A (LDHA) gene. LDHA catalyzes pyruvate into lactate instead of leading into the tricarboxylic acid cycle. Lactate increases breast cancer cell proliferation, migration, and invasion. In addition, it activates normal-associated fibroblasts (NAFs) into cancer-associated fibroblasts (CAFs). Conversely, LDHA knockdown in breast cancer cells that overexpress POU1F1 decreases tumor volume and [¹⁸F]FDG uptake in tumor xenografts of mice. Clinically, POU1F1 and LDHA expression correlate with relapse- and metastasis-free survival. Our data indicate that POU1F1 induces a metabolic reprogramming through LDHA regulation in human breast tumor cells, modifying the phenotype of both cancer cells and fibroblasts to promote cancer progression.

The Role of VP16 in the Life Cycle of Alphaherpesviruses

The protein encoded by the UL48 gene of alphaherpesviruses is named VP16 or alpha-gene-transactivating factor (α-TIF). In the early stage of viral replication, VP16 is an important transactivator that can activate the transcription of viral immediate-early genes, and in the late stage of viral replication, VP16, as a tegument, is involved in viral assembly. This review will explain the mechanism of VP16 acting as α-TIF to activate the transcription of viral immediate-early genes, its role in the transition from viral latency to reactivation, and its effects on viral assembly and maturation. In addition, this review also provides new insights for further research on the life cycle of alphaherpesviruses and the role of VP16 in the viral life cycle.

A Case Series of X-Linked Deafness-2 with Sensorineural Hearing Loss, Stapes Fixation, and Perilymphatic Gusher: MR Imaging and Clinical Features of Hypothalamic Malformations

X-linked deafness-2 (DFNX2) is an X-linked recessive disorder characterized by profound sensorineural hearing loss and a pathognomonic temporal bone deformity. Because hypothalamic malformations associated with DFNX2 have been rarely described, we aimed to further describe these lesions and compare them with features of a nonaffected population. All patients diagnosed with DFNX2 between 2006 and 2019 were included and compared with age-matched patients with normal MR imaging findings and without hypothalamic dysfunction. MR imaging features differing between groups were selected to help identify DFNX2. Sensitivity and specificity were calculated for these features. Agreement among 3 radiologists was quantified using the index κ. Information on the presence or absence of gelastic seizures, precocious puberty, or delayed puberty was also gathered. We selected distinctive MR imaging features of hypothalamic malformations in DFNX2. The feature selected on axial T2 images was the folded appearance of the ventromedial hypothalamus (sensitivity, 100%; specificity, 95.8%) characterized by an abnormal internal/external cleft (sensitivity, 100%; specificity, 95.7%). On coronal T2, the first distinctive feature was a concave morphology of the medial eminence (sensitivity, 100%; specificity, 97.1%), the second feature was at least 1 hypothalamic-septum angle ≥90° (sensitivity, 90%; specificity, 72.5%), and the third feature was a forebrain-hypothalamic craniocaudal length of ≥6 mm (sensitivity, 70%; specificity, 79.7%). Clinical features were also distinctive because 9 patients with DFNX2 did not present with gelastic seizures or precocious puberty. One patient had delayed puberty. The κ index and intraclass correlation coefficient ranged between 0.78 and 0.95. Imaging and clinical features of the hypothalamus suggest that there is a hypothalamic malformation associated with DFNX2. Early assessment for pubertal delay is proposed.

The POU Transcription Factor POU-M2 Regulates Vitellogenin Receptor Gene Expression in the Silkworm, Bombyx mori

Vitellogenin receptors (VgRs) play critical roles in egg formation by transporting vitellogenin (Vg) into oocytes in insects. Although the function of VgR in insects is well studied, the transcriptional regulation of this gene is still unclear. Here, we cloned the promoter of the VgR gene from Bombyx mori (BmVgR), and predicted many POU cis-response elements (CREs) in its promoter. Electrophoretic mobility shift and chromatin immunoprecipitation assays showed that the POU transcription factor POU-M2 bound directly to the CREs of the promoter. Overexpression of POU-M2 in an ovarian cell line (BmNs) enhanced BmVgR transcription and promoter activity detected by quantitative reverse transcription PCR and luciferase reporter assays. Analyses of expression patterns indicated that POU-M2 was expressed in ovary at day two of wandering stage initially, followed by BmVgR. RNA interference of POU-M2 significantly reduced the transcription of BmVgR in ovary and egg-laying rate. Our results suggest a novel function for the POU factor in silkworm oogenesis by its involvement in BmVgR regulation and expands the understanding of POU factors in insect VgR expression.

Identification of a molecular basis for the juvenile sleep state

Across species, sleep in young animals is critical for normal brain maturation. The molecular determinants of early life sleep remain unknown. Through an RNAi-based screen, we identified a gene, pdm3, required for sleep maturation in Drosophila. Pdm3, a transcription factor, coordinates an early developmental program that prepares the brain to later execute high levels of juvenile adult sleep. PDM3 controls the wiring of wake-promoting dopaminergic (DA) neurites to a sleep-promoting region, and loss of PDM3 prematurely increases DA inhibition of the sleep center, abolishing the juvenile sleep state. RNA-Seq/ChIP-Seq and a subsequent modifier screen reveal that pdm3 represses expression of the synaptogenesis gene Msp300 to establish the appropriate window for DA innervation. These studies define the molecular cues governing sleep behavioral and circuit development, and suggest sleep disorders may be of neurodevelopmental origin.

Structural facets of POU2F1 in light of the functional annotations and sequence-structure patterns

POU domain class 2 homebox 1 or POU2F1 is broadly known as an important transcription factor. Due to its association with different types of malignancies, POU2F1 became one of the key factors in pancancer analysis. However, in spite of considering this protein as a potential drug target, none of the drug targeting POU2F1 has been designed as of yet due to the extreme structural flexibility of this protein. In this article, we have proposed a three-level comprehensive framework for understanding the structural conservation and co-variation of POU2F1. First, a gene regulatory network based on the normal and pathological functions of POU2F1 has been created for better understanding the strong association between POU2F1 deregulation and cancers. After that, based on the evolutionary sequence space analysis, the comparative sequence dynamics of the protein members of POU domain family has been studied mostly between non-human and human species. Subsequently, the reciprocity effect of the residual co-variation has been identified through direct coupling analysis. Along with that, the structure of POU2F1 has been analyzed depending on quality assessment and normal mode-based structure network. Comparing the sequence and structure space information, the most significant set of residues viz., 3, 9, 13, 17, 20, 21, 28, 35, and 36 have been identified as structural facet for function. This study demonstrates that the structural malleability of POU2F1 serves as one of the prime reason behind its functional multiplicity in terms of protein moonlighting. Communicated by Ramaswamy H. Sarma.

Congenital Hypopituitarism During the Neonatal Period: Epidemiology, Pathogenesis, Therapeutic Options, and Outcome

Introduction: Congenital hypopituitarism (CH) is characterized by a deficiency of one or more pituitary hormones. The pituitary gland is a central regulator of growth, metabolism, and reproduction. The anterior pituitary produces and secretes growth hormone (GH), adrenocorticotropic hormone, thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin. The posterior pituitary hormone secretes antidiuretic hormone and oxytocin. Epidemiology: The incidence is 1 in 4,000-1 in 10,000. The majority of CH cases are sporadic; however, a small number of familial cases have been identified. In the latter, a molecular basis has frequently been identified. Between 80-90% of CH cases remain unsolved in terms of molecular genetics. Pathogenesis: Several transcription factors and signaling molecules are involved in the development of the pituitary gland. Mutations in any of these genes may result in CH including HESX1, PROP1, POU1F1, LHX3, LHX4, SOX2, SOX3, OTX2, PAX6, FGFR1, GLI2, and FGF8. Over the last 5 years, several novel genes have been identified in association with CH, but it is likely that many genes remain to be identified, as the majority of patients with CH do not have an identified mutation. Clinical manifestations: Genotype-phenotype correlations are difficult to establish. There is a high phenotypic variability associated with different genetic mutations. The clinical spectrum includes severe midline developmental disorders, hypopituitarism (in isolation or combined with other congenital abnormalities), and isolated hormone deficiencies. Diagnosis and treatment: Key investigations include MRI and baseline and dynamic pituitary function tests. However, dynamic tests of GH secretion cannot be performed in the neonatal period, and a diagnosis of GH deficiency may be based on auxology, MRI findings, and low growth factor concentrations. Once a hormone deficit is confirmed, hormone replacement should be started. If onset is acute with hypoglycaemia, cortisol deficiency should be excluded, and if identified this should be rapidly treated, as should TSH deficiency. This review aims to give an overview of CH including management of this complex condition.

BRN4 Is a Novel Driver of Neuroendocrine Differentiation in Castration-Resistant Prostate Cancer and Is Selectively Released in Extracellular Vesicles with BRN2

PURPOSE

Neuroendocrine prostate cancer (NEPC), an aggressive variant of castration-resistant prostate cancer (CRPC), often emerges after androgen receptor-targeted therapies such as enzalutamide or de novo, via trans-differentiation process of neuroendocrine differentiation. The mechanistic basis of neuroendocrine differentiation is poorly understood, contributing to lack of effective predictive biomarkers and late disease recognition. The purpose of this study was to examine the role of novel proneural Pit-Oct-Unc-domain transcription factors (TF) in NEPC and examine their potential as noninvasive predictive biomarkers.Experimental Design: Prostate cancer patient-derived xenograft models, clinical samples, and cellular neuroendocrine differentiation models were employed to determine the expression of TFs BRN1 and BRN4. BRN4 levels were modulated in prostate cancer cell lines followed by functional assays. Furthermore, extracellular vesicles (EV) were isolated from patient samples and cell culture models, characterized by nanoparticle tracking analyses, Western blotting, and real-time PCR.

RESULTS

We identify for the first time that: (i) BRN4 is amplified and overexpressed in NEPC clinical samples and that BRN4 overexpression drives neuroendocrine differentiation via its interplay with BRN2, a TF that was previously implicated in NEPC; (ii) BRN4 and BRN2 mRNA are actively released in prostate cancer EVs upon neuroendocrine differentiation induction; and (iii) enzalutamide treatment augments release of BRN4 and BRN2 in prostate cancer EVs, promoting neuroendocrine differentiation induction.

CONCLUSIONS

Our study identifies a novel TF that drives NEPC and suggests that as adaptive mechanism to enzalutamide treatment, prostate cancer cells express and secrete BRN4 and BRN2 in EVs that drive oncogenic reprogramming of prostate cancer cells to NEPC. Importantly, EV-associated BRN4 and BRN2 are potential novel noninvasive biomarkers to predict neuroendocrine differentiation in CRPC.

Biochemical and structural characterization of a novel cooperative binding mode by Pit-1 with CATT repeats in the macrophage migration inhibitory factor promoter

Overexpression of the proinflammatory cytokine macrophage migration inhibitory factor (MIF) is linked to a number of autoimmune diseases and cancer. MIF production has been correlated to the number of CATT repeats in a microsatellite region upstream of the MIF gene. We have characterized the interaction of pituitary-specific positive transcription factor 1 (Pit-1) with a portion of the MIF promoter region flanking a microsatellite polymorphism (-794 CATT5-8). Using fluorescence anisotropy, we quantified tight complex formation between Pit-1 and an oligonucleotide consisting of eight consecutive CATT repeats (8xCATT) with an apparent Kd of 35 nM. Using competition experiments we found a 23 base pair oligonucleotide with 4xCATT repeats to be the minimum DNA sequence necessary for high affinity interaction with Pit-1. The stoichiometry of the Pit-1 DNA interaction was determined to be 2:1 and binding is cooperative in nature. We subsequently structurally characterized the complex and discovered a completely novel binding mode for Pit-1 in contrast to previously described Pit-1 complex structures. The affinity of Pit-1 for the CATT target sequence was found to be highly dependent on cooperativity. This work lays the groundwork for understanding transcriptional regulation of MIF and pursuing Pit-1 as a therapeutic target to treat MIF-mediated inflammatory disorders.

BmILF and i-motif structure are involved in transcriptional regulation of BmPOUM2 in Bombyx mori

Guanine-rich and cytosine-rich DNA can form four-stranded DNA secondary structures called G-quadruplex (G4) and i-motif, respectively. These structures widely exist in genomes and play important roles in transcription, replication, translation and protection of telomeres. In this study, G4 and i-motif structures were identified in the promoter of the transcription factor gene BmPOUM2, which regulates the expression of the wing disc cuticle protein gene (BmWCP4) during metamorphosis. Disruption of the i-motif structure by base mutation, anti-sense oligonucleotides (ASOs) or inhibitory ligands resulted in significant decrease in the activity of the BmPOUM2 promoter. A novel i-motif binding protein (BmILF) was identified by pull-down experiment. BmILF specifically bound to the i-motif and activated the transcription of BmPOUM2. The promoter activity of BmPOUM2 was enhanced when BmILF was over-expressed and decreased when BmILF was knocked-down by RNA interference. This study for the first time demonstrated that BmILF and the i-motif structure participated in the regulation of gene transcription in insect metamorphosis and provides new insights into the molecular mechanism of the secondary structures in epigenetic regulation of gene transcription.

Hypothalamic malformations in patients with X-linked deafness and incomplete partition type 3

Patients with X-linked deafness carry mutations in the POU3F4 gene and have pathognomonic inner ear malformations characterised by symmetrical incomplete partition type 3 (absent modiolus and lamina spiralis but preserved interscalar septum in a normal-sized cochlea) and large internal auditory meatus (IAM) with an increased risk of gusher during stapes surgery. We describe a range of fairly characteristic malformations in the hypothalamus of some patients with this rare condition, ranging from subtle asymmetric appearance and thickening of the tuber cinereum to more marked hypothalamic enlargement. We discuss the role of POU3F4 in the normal development of both the inner ear and hypothalamus and the proposed pathophysiology of incomplete partition type 3.

Relationship between SNPs of POU1F1 Gene and Litter Size and Growth Traits in Shaanbei White Cashmere Goats

POU (Pit-Oct-Unc) class 1 homeobox 1 (POU1F1, or Pit-1) is a transcription factor that directly regulates pituitary hormone-related genes, as well as affects the reproduction and growth in mammals. Thus, POU1F1 gene was investigated as a candidate gene for litter size and growth performance in goats. In the current study, using direct DNA sequencing, c.682G > T, c.723T > G and c.837T > C loci were genotyped in Shaanbei white cashmere (SBWC) goats (n = 609), but c.876 + 110T > C was monomorphic. Besides, the c.682G > T locus was first identified by HinfI (Haemophilus influenzae Rf) restriction endonuclease. Association analysis results showed that the c.682G > T, c.837T > C loci and diplotypes were significantly associated with goat litter size (p < 0.05). The positive genotypes were GT and TT for the two SNPs, respectively, and the optimal diplotype was H3H7 (GTTT-TTTT). On the other hand, the c.682G > T, c.723T > G and c.837T > C strongly affected growth traits and body measurement indexes in SBWC goats (p < 0.05). The positive genotypes or allele of these SNPs were GT, G and TT, respectively. Additionally, the goats with H3H7 diplotype also had a greater growth status than others (p < 0.05). Here, individuals with same genotype had both a better litter size and growth traits, showing a positive correlation between these economic traits. Meanwhile, the positive genotypes of four SNPs were combined to obtain the optimal diplotype, which was also H3H7. These SNPs, especially the diplotype, could be used for the genomic selection of excellent individuals with a greater litter size and better growth status in goat breeding.

BRN2 suppresses apoptosis, reprograms DNA damage repair, and is associated with a high somatic mutation burden in melanoma

Herbert et al. show that BRN2 is associated with DNA damage response proteins and suppresses an apoptosis-associated gene expression program to protect against UVB-, chemotherapy-, and vemurafenib-induced apoptosis.

Whether cell types exposed to a high level of environmental insults possess cell type-specific prosurvival mechanisms or enhanced DNA damage repair capacity is not well understood. BRN2 is a tissue-restricted POU domain transcription factor implicated in neural development and several cancers. In melanoma, BRN2 plays a key role in promoting invasion and regulating proliferation. Here we found, surprisingly, that rather than interacting with transcription cofactors, BRN2 is instead associated with DNA damage response proteins and directly binds PARP1 and Ku70/Ku80. Rapid PARP1-dependent BRN2 association with sites of DNA damage facilitates recruitment of Ku80 and reprograms DNA damage repair by promoting Ku-dependent nonhomologous end-joining (NHEJ) at the expense of homologous recombination. BRN2 also suppresses an apoptosis-associated gene expression program to protect against UVB-, chemotherapy- and vemurafenib-induced apoptosis. Remarkably, BRN2 expression also correlates with a high single-nucleotide variation prevalence in human melanomas. By promoting error-prone DNA damage repair via NHEJ and suppressing apoptosis of damaged cells, our results suggest that BRN2 contributes to the generation of melanomas with a high mutation burden. Our findings highlight a novel role for a key transcription factor in reprogramming DNA damage repair and suggest that BRN2 may impact the response to DNA-damaging agents in BRN2-expressing cancers.

Hypothalamic sonic hedgehog is required for cell specification and proliferation of LHX3/LHX4 pituitary embryonic precursors

Sonic hedgehog (SHH) is an essential morphogenetic signal that dictates cell fate decisions in several developing organs in mammals. In vitro data suggest that SHH is required to specify LHX3⁺/LHX4⁺ Rathke's pouch (RP) progenitor identity. However, in vivo studies have failed to reveal such a function, supporting instead a crucial role for SHH in promoting proliferation of these RP progenitors and for differentiation of pituitary cell types. Here, we have used a genetic approach to demonstrate that activation of the SHH pathway is necessary to induce LHX3⁺/LHX4⁺ RP identity in mouse embryos. First, we show that conditional deletion of Shh in the anterior hypothalamus results in a fully penetrant phenotype characterised by a complete arrest of RP development, with lack of Lhx3/Lhx4 expression in RP epithelium at 9.0 days post coitum (dpc) and total loss of pituitary tissue by 12.5 dpc. Conversely, overactivation of the SHH pathway by conditional deletion of Ptch1 in RP progenitors leads to severe hyperplasia and enlargement of the Sox2⁺ stem cell compartment by the end of gestation.

Expression of developing neural transcription factors in diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH)

DIPNECH is characterized by neuroendocrine cell hyperplasia, tumorlets, and eventually carcinoid tumors. Although it is regarded by some authors as a preneoplastic condition, this issue is controversial. New pathologic criteria have recently been proposed for the diagnosis of DIPNECH, and a subgroup of carcinoid tumors expressing developing neural transcription factors (DNTFs), with clinicopathologic features similar to those of DIPNECH, has been recognized. This paper reports on the clinical and pathological findings in three cases of DIPNECH and investigates the expression of three DNTFs (TTF1, ASCL1, and POU3F2). All patients were female, with a mean age of 63 years, and all lesions were located in the periphery of the lung. In two cases, typical carcinoids were associated with a spindle-cell component. All neuroendocrine proliferations were DNTF positive. The morphologic (spindle-cell component), phenotypic (DNTF expression), and clinicopathologic (peripheral tumors, female predominance) similarities suggest that DIPNECH may be a preneoplastic lesion for peripheral carcinoids.

Substituting mouse transcription factor Pou4f2 with a sea urchin orthologue restores retinal ganglion cell development

Pou domain transcription factor Pou4f2 is essential for the development of retinal ganglion cells (RGCs) in the vertebrate retina. A distant orthologue of Pou4f2 exists in the genome of the sea urchin (class Echinoidea) Strongylocentrotus purpuratus (SpPou4f1/2), yet the photosensory structure of sea urchins is strikingly different from that of the mammalian retina. Sea urchins have no obvious eyes, but have photoreceptors clustered around their tube feet disc. The mechanisms that are associated with the development and function of photoreception in sea urchins are largely unexplored. As an initial approach to better understand the sea urchin photosensory structure and relate it to the mammalian retina, we asked whether SpPou4f1/2 could support RGC development in the absence of Pou4f2. To answer this question, we replaced genomic Pou4f2 with an SpPou4f1/2 cDNA. In Pou4f2-null mice, retinas expressing SpPou4f1/2 were outwardly identical to those of wild-type mice. SpPou4f1/2 retinas exhibited dark-adapted electroretinogram scotopic threshold responses, indicating functionally active RGCs. During retinal development, SpPou4f1/2 activated RGC-specific genes and in S. purpuratus, SpPou4f2 was expressed in photoreceptor cells of tube feet in a pattern distinct from Opsin4 and Pax6. Our results suggest that SpPou4f1/2 and Pou4f2 share conserved components of a gene network for photosensory development and they maintain their conserved intrinsic functions despite vast morphological differences in mouse and sea urchin photosensory structures.

Functional characterization of a human POU1F1 mutation associated with isolated growth hormone deficiency: a novel etiology for IGHD

POU1F1, a pituitary-specific POU-homeo domain transcription factor, plays an essential role in the specification of the somatotroph, lactotroph and thyrotroph lineages and in the activation of GH1, PRL and TSHβ transcription. Individuals with mutations in POU1F1 present with combined deficiency of GH, PRL and TSH. Here, we identified a heterozygous missense mutation with evidence of pathogenicity, at the POU1F1 locus, in a large family in which an isolated growth hormone deficiency segregates as an autosomal dominant trait. The corresponding p.Pro76Leu mutation maps to a conserved site within the POU1F1 transactivation domain. Bandshift assays revealed that the mutation alters wild-type POU1F1 binding to cognate sites within the hGH-LCR and hGH1 promoter, but not to sites within the PRL promoter, and it selectively increases binding affinity to sites within the hGH-LCR. Co-immunoprecipitation studies reveal that this substitution enhances interactions of POU1F1 with three of its cofactors, PITX1, LHX3a and ELK1, and that residue 76 plays a critical role in these interactions. The insertion of the mutation at the mouse Pou1f1 locus results in a dramatic loss of protein expression despite normal mRNA concentrations. Mice heterozygous for the p.Pro76Leu mutation were phenotypically normal while homozygotes demonstrated a dwarf phenotype. Overall, this study unveils the involvement of POU1F1 in dominantly inherited isolated GH deficiency and demonstrates a significant impact of the Pro76Leu mutation on DNA-binding activities, alterations in transactivating functions and interactions with cofactors. Our data further highlight difficulties in modeling human genetic disorders in the mouse despite apparent conservation of gene expression pathways and physiologic functions.

A novel mutation in POU3F4 in a Chinese family with X-linked non-syndromic hearing loss

Objective

Based on the clinical manifestations of a hearing loss patient, the POU3F4 gene was tested for diagnosis of etiology.

Methods

A comprehensive physical examination was performed on the proband to exclude abnormalities of other organs, and detailed audiological testing and temporal bone CT scan were also performed. Genomic DNA was extracted using the proband's peripheral blood leukocytes. Polymerase chain reactions (PCR) were performed in the coding sequence of the POU3F4 gene. Direct DNA sequencing was subsequently applied to screen the entire coding region of the POU3F4 gene.

Results

The proband had severe sensorineural hearing loss. Temporal CT showed bilateral cochlear incomplete partition, vestibule dysplasia, internal auditory canal fundus expansion, and cochlear interlink with the internal auditory canal fundus. A novel mutation (c.530C > A (p.S177X)) in the POU3F4 gene was found in this patient, creating an new stop codon and was predicted to result in a truncated protein lacking normal POU3F4 transcription factor function.

Conclusion

Through analysis of the POU3F4 gene and clinical manifestations in the patient, we conclude that a novel mutation may have resulted in a premature stop codon, contributing to the mutation of POU3F4 gene.

The homeodomain transcription factors antennapedia and POU-M2 regulate the transcription of the steroidogenic enzyme gene Phantom in the silkworm

The steroid hormone ecdysone, which controls insect molting and metamorphosis, is synthesized in the prothoracic gland (PG), and several steroidogenic enzymes that are expressed specifically in the PG are involved in ecdysteroidogenesis. In this study, we identified new regulators that are involved in the transcriptional control of the silkworm steroidogenic enzyme genes. In silico analysis predicted several potential cis-regulatory elements (CREs) for the homeodomain transcription factors Antennapedia (Antp) and POU-M2 in the proximal promoters of steroidogenic enzyme genes. Antp and POU-M2 are expressed dynamically in the PG during larval development, and their overexpression in silkworm embryo-derived (BmE) cells induced the expression of steroidogenic enzyme genes. Importantly, luciferase reporter analyses, electrophoretic mobility shift assays, and chromatin immunoprecipitation assays revealed that Antp and POU-M2 promote the transcription of the silkworm steroidogenic enzyme gene Phantom (Phm) by binding directly to specific motifs within overlapping CREs in the Phm promoter. Mutations of these CREs in the Phm promoter suppressed the transcriptional activities of both Antp and POU-M2 in BmE cells and decreased the activities of mutated Phm promoters in the silkworm PG. In addition, pulldown and co-immunoprecipitation assays demonstrated that Antp can interact with POU-M2. Moreover, RNA interference-mediated down-regulation of either Antp or POU-M2 during silkworm wandering not only decreased the ecdysone titer but also led to the failure of metamorphosis. In summary, our results suggest that Antp and POU-M2 coordinate the transcription of the silkworm Phm gene directly, indicating new roles for homeodomain proteins in regulating insect ecdysteroidogenesis.

Dose-dependent dual role of PIT-1 (POU1F1) in somatolactotroph cell proliferation and apoptosis

To test the role of wtPIT-1 (PITWT) or PIT-1 (R271W) (PIT271) in somatolactotroph cells, we established, using inducible lentiviral vectors, sublines of GH4C1 somatotroph cells that allow the blockade of the expression of endogenous PIT-1 and/or the expression of PITWT or PIT271, a dominant negative mutant of PIT-1 responsible for Combined Pituitary Hormone Deficiency in patients. Blocking expression of endogenous PIT-1 induced a marked decrease of cell proliferation. Overexpressing PITWT twofold led also to a dose-dependent decrease of cell proliferation that was accompanied by cell death. Expression of PIT271 induced a strong dose-dependent decrease of cell proliferation accompanied by a very pronounced cell death. These actions of PIT271 are independent of its interaction/competition with endogenous PIT-1, as they were unchanged when expression of endogenous PIT-1 was blocked. All these actions are specific for somatolactotroph cells, and could not be observed in heterologous cells. Cell death induced by PITWT or by PIT271 was accompanied by DNA fragmentation, but was not inhibited by inhibitors of caspases, autophagy or necrosis, suggesting that this cell death is a caspase-independent apoptosis. Altogether, our results indicate that under normal conditions PIT-1 is important for the maintenance of cell proliferation, while when expressed at supra-normal levels it induces cell death. Through this dual action, PIT-1 may play a role in the expansion/regression cycles of pituitary lactotroph population during and after lactation. Our results also demonstrate that the so-called “dominant-negative” action of PIT271 is independent of its competition with PIT-1 or a blockade of the actions of the latter, and are actions specific to this mutant variant of PIT-1.

Cis-regulatory mechanisms for robust olfactory sensory neuron class-restricted odorant receptor gene expression in Drosophila

Odor perception requires that each olfactory sensory neuron (OSN) class continuously express a single odorant receptor (OR) regardless of changes in the environment. However, little is known about the control of the robust, class-specific OR expression involved. Here, we investigate the cis-regulatory mechanisms and components that generate robust and OSN class-specific OR expression in Drosophila. Our results demonstrate that the spatial restriction of expression to a single OSN class is directed by clusters of transcription-factor DNA binding motifs. Our dissection of motif clusters of differing complexity demonstrates that structural components such as motif overlap and motif order integrate transcription factor combinations and chromatin status to form a spatially restricted pattern. We further demonstrate that changes in metabolism or temperature perturb the function of complex clusters. We show that the cooperative regulation between motifs around and within the cluster generates robust, class-specific OR expression.

Our neurons can become over a hundred years old. Even if neurons are restructured and remodeled by their constant work of receiving, storing and sending information, they stay devoted to one single task and retain their identity for their whole life. How a neuron keeps its identity is not well understood. In the olfactory system, the identity of the olfactory sensory neuron (OSN) is a result of the expression of a single odorant receptor (OR) from a large receptor gene repertoire in the genome. Neurons that share an expressed receptor make a functional class. Here, we identify clusters of transcription factor binding motifs to be the smallest unit that drive expression in a single olfactory sensory neuron class. We further demonstrate that it is the structure of the cluster that determines the class specific expression. However, environmental stress, such as temperature changes or starvation, destabilizes the expression produced by the cluster. Our results demonstrate that stable expression is generated from redundant motifs outside the cluster and suggest that cooperative regulation generates robust expression of the genes that determine neuronal identity and function.

Melatonin regulates somatotrope and lactotrope function through common and distinct signaling pathways in cultured primary pituitary cells from female primates

Melatonin (MT) is secreted by the pineal gland and exhibits a striking circadian rhythm in its release. Depending on the species studied, some pituitary hormones also display marked circadian/seasonal patterns and rhythms of secretion. However, the precise relationship between MT and pituitary function remains controversial, and studies focusing on the direct role of MT in normal pituitary cells are limited to nonprimate species. Here, adult normal primate (baboons) primary pituitary cell cultures were used to determine the direct impact of MT on the functioning of all pituitary cell types from the pars distalis. MT increased GH and prolactin (PRL) expression/release in a dose- and time-dependent fashion, a response that was blocked by somatostatin. However, MT did not significantly affect ACTH, FSH, LH, or TSH expression/release. MT did not alter GHRH- or ghrelin-induced GH and/or PRL secretions, suggesting that MT may activate similar signaling pathways as ghrelin/GHRH. The effects of MT on GH/PRL release, which are likely mediated through MT1 receptor, involve both common (adenylyl cyclase/protein kinase A/extracellular calcium-channels) and distinct (phospholipase C/intracellular calcium-channels) signaling pathways. Actions of MT on pituitary cells also included regulation of the expression of other key components for the control of somatotrope/lactotrope function (GHRH, ghrelin, and somatostatin receptors). These results show, for the first time in a primate model, that MT directly regulates somatotrope/lactotrope function, thereby lending support to the notion that the actions of MT on these cells might substantially contribute to the define daily patterns of GH and PRL observed in primates and perhaps in humans.

Regulation of the orphan nuclear receptor Nr2f2 by the DFNA15 deafness gene Pou4f3

Hair cells are the mechanotransducing cells of the inner ear that are essential for hearing and balance. POU4F3--a POU-domain transcription factor selectively expressed by these cells--has been shown to be essential for hair cell differentiation and survival in mice and its mutation in humans underlies late-onset progressive hearing loss (DFNA15). The downstream targets of POU4F3 are required for hair cell differentiation and survival. We aimed to identify such targets in order to elucidate the molecular pathways involved in hair cell production and maintenance. The orphan thyroid nuclear receptor Nr2f2 was identified as a POU4F3 target using a subtractive hybridization strategy and EMSA analysis showed that POU4F3 binds to two sites in the Nr2f2 5' flanking region. These sites were shown to be required for POU4F3 activation as their mutation leads to a reduction in the response of an Nr2f2 5' flanking region reporter construct to POU4F3. Immunocytochemistry was carried out in the developing and adult inner ear in order to investigate the relevance of this interaction in hearing. NR2F2 expression in the postnatal mouse organ of Corti was shown to be detectable in all sensory epithelia examined and characterised. These data demonstrate that Nr2f2 is a direct target of POU4F3 in vitro and that this regulatory relationship may be relevant to hair cell development and survival.

The POU factor ventral veins lacking/Drifter directs the timing of metamorphosis through ecdysteroid and juvenile hormone signaling

Although endocrine changes are known to modulate the timing of major developmental transitions, the genetic mechanisms underlying these changes remain poorly understood. In insects, two developmental hormones, juvenile hormone (JH) and ecdysteroids, are coordinated with each other to induce developmental changes associated with metamorphosis. However, the regulation underlying the coordination of JH and ecdysteroid synthesis remains elusive. Here, we examined the function of a homolog of the vertebrate POU domain protein, Ventral veins lacking (Vvl)/Drifter, in regulating both of these hormonal pathways in the red flour beetle, Tribolium castaneum (Tenebrionidae). RNA interference-mediated silencing of vvl expression led to both precocious metamorphosis and inhibition of molting in the larva. Ectopic application of a JH analog on vvl knockdown larvae delayed the onset of metamorphosis and led to a prolonged larval stage, indicating that Vvl acts upstream of JH signaling. Accordingly, vvl knockdown also reduced the expression of a JH biosynthesis gene, JH acid methyltransferase 3 (jhamt3). In addition, ecdysone titer and the expression of the ecdysone response gene, hormone receptor 3 (HR3), were reduced in vvl knockdown larvae. The expression of the ecdysone biosynthesis gene phantom (phm) and spook (spo) were reduced in vvl knockdown larvae in the anterior and posterior halves, respectively, indicating that Vvl might influence ecdysone biosynthesis in both the prothoracic gland and additional endocrine sources. Injection of 20-hydroxyecdysone (20E) into vvl knockdown larvae could restore the expression of HR3 although molting was never restored. These findings suggest that Vvl coordinates both JH and ecdysteroid biosynthesis as well as molting behavior to influence molting and the timing of metamorphosis. Thus, in both vertebrates and insects, POU factors modulate the production of major neuroendocrine regulators during sexual maturation.

Hormones play major roles in initiating major developmental transitions, such as puberty and metamorphosis. However, how organisms coordinate changes across multiple hormones remains unclear. In this study, we show that silencing the POU domain transcription factor Ventral veins lacking (Vvl)/Drifter in the red flour beetle Tribolium castaneum leads to precocious metamorphosis and an inability to molt. We show that Vvl regulates the biosynthesis and signaling of two key insect developmental hormones, juvenile hormone (JH) and ecdysteroids. Vvl therefore appears to act as a potential central regulator of developmental timing by influencing two major hormones. Because POU factors are known as a major regulator of the onset of puberty, POU factors play a major role during sexual maturation in both vertebrates and insects.

The transcription factor Pou3f1 promotes neural fate commitment via activation of neural lineage genes and inhibition of external signaling pathways

The neural fate commitment of pluripotent stem cells requires the repression of extrinsic inhibitory signals and the activation of intrinsic positive transcription factors. However, how these two events are integrated to ensure appropriate neural conversion remains unclear. In this study, we showed that Pou3f1 is essential for the neural differentiation of mouse embryonic stem cells (ESCs), specifically during the transition from epiblast stem cells (EpiSCs) to neural progenitor cells (NPCs). Chimeric analysis showed that Pou3f1 knockdown leads to a markedly decreased incorporation of ESCs in the neuroectoderm. By contrast, Pou3f1-overexpressing ESC derivatives preferentially contribute to the neuroectoderm. Genome-wide ChIP-seq and RNA-seq analyses indicated that Pou3f1 is an upstream activator of neural lineage genes, and also is a repressor of BMP and Wnt signaling. Our results established that Pou3f1 promotes the neural fate commitment of pluripotent stem cells through a dual role, activating internal neural induction programs and antagonizing extrinsic neural inhibitory signals.

Obestatin plays an opposite role in the regulation of pituitary somatotrope and corticotrope function in female primates and male/female mice

Obestatin is a 23-amino-acid amidated peptide that is encoded by the ghrelin gene. Previous studies have shown obestatin can modulate the hypothalamic neuronal circuitry that regulates pituitary function, perhaps by modulating the actions of ghrelin. However, the direct actions of obestatin on pituitary function remain controversial. Here, primary pituitary cell cultures from a nonhuman primate (baboon) and mice were used to test the effects of obestatin on pituitary hormone expression and secretion. In pituitary cultures from both species, obestatin had no effect on prolactin, LH, FSH, or TSH expression/release. Conversely, obestatin stimulated proopiomelanocortin expression and ACTH release and inhibited GH expression/release in vitro, actions that were also observed in vivo in mice treated with obestatin. In vitro, obestatin inhibited the stimulatory actions of ghrelin on GH but not ACTH release. The inhibitory effect of obestatin on somatotrope function was associated with an overall reduction in pituitary transcription factor-1 and GHRH receptor mRNA levels in vitro and in vivo as well as a reduction in hypothalamic GHRH and ghrelin expression in vivo. The stimulatory effect of obestatin on ACTH was associated with an increase in pituitary CRF receptors. Obestatin also reduced the expression of pituitary somatostatin receptors (sst1/sst2), which could serve to modify its impact on hormone secretion. The in vitro actions of obestatin on both GH and ACTH release required the adenylyl cyclase and MAPK routes. Taken together, our results provide evidence that obestatin can act directly at the pituitary to control somatotrope and corticotrope function, and these effects are conserved across species.

Direct conversion of human fibroblasts into neuronal restricted progenitors

Neuronal restricted progenitors (NRPs) represent a type of transitional intermediate cells that lie between multipotent neural progenitors and terminal differentiated neurons during neurogenesis. These NRPs have the ability to self-renew and differentiate into neurons, but not into glial cells, which is considered an advantage for cellular therapy of human neurodegenerative diseases. However, difficulty in the extraction of highly purified NRPs from normal nervous tissue prevents further studies and applications. In this study, we report the conversion of human fetal fibroblasts into human induced NRPs (hiNRPs) in 11 days by using just three defined factors: Sox2, c-Myc, and either Brn2 or Brn4. The hiNRPs exhibited distinct neuronal characteristics, including cell morphology, multiple neuronal marker expression, self-renewal capacity, and a genome-wide transcriptional profile. Moreover, hiNRPs were able to differentiate into various terminal neurons with functional membrane properties but not glial cells. Direct generation of hiNRPs from somatic cells will provide a new source of cells for cellular replacement therapy of human neurodegenerative diseases.

Oct-2 transcription factor binding activity and expression up-regulation in rat cerebral ischaemia is associated with a diminution of neuronal damage in vitro

Brain plasticity provides a mechanism to compensate for lesions produced as a result of stroke. The present study aims to identify new transcription factors (TFs) following focal cerebral ischaemia in rat as potential therapeutic targets. A transient focal cerebral ischaemia model was used for TF-binding activity and TF-TF interaction profile analysis. A permanent focal cerebral ischaemia model was used for the transcript gene analysis and for the protein study. The identification of TF variants, mRNA analysis, and protein study was performed using conventional polymerase chain reaction (PCR), qPCR, and Western blot and immunofluorescence, respectively. Rat cortical neurons were transfected with small interfering RNA against the TF in order to study its role. The TF-binding analysis revealed a differential binding activity of the octamer family in ischaemic brain in comparison with the control brain samples both in acute and late phases. In this study, we focused on Oct-2 TF. Five of the six putative Oct-2 transcript variants are expressed in both control and ischaemic rat brain, showing a significant increase in the late phase of ischaemia. Oct-2 protein showed neuronal localisation both in control and ischaemic rat brain cortical slices. Functional studies revealed that Oct-2 interacts with TFs involved in important brain processes (neuronal and vascular development) and basic cellular functions and that Oct-2 knockdown promotes neuronal injury. The present study shows that Oct-2 expression and binding activity increase in the late phase of cerebral ischaemia and finds Oct-2 to be involved in reducing ischaemic-mediated neuronal injury.

Bioinformatic analysis of the four transcription factors used to induce pluripotent stem cells

Induced pluripotent stem (iPS) cells are a type of pluripotent stem cell artificially derived from non-pluripotent cells by overexpressing the transcription factors Oct4, Sox2, Klf4 and Nanog. These transcription factors play a pivotal role in stem cells; however, the function of these factors are not fully characterized. In this study, we analyzed Oct4, Sox2, Klf4 and Nanog in ten different species using bioinformatics, to provide more knowledge of the function of these genes. Nanog does not exist in the invertebrates Caenorhabditis elegans and Drosophila melanogaster, indicating that the absence of Nanog may be responsible for the developmental differences between vertebrates and invertebrates. Construction of phylogenetic trees confirmed that the function of Nanog is conserved from fish to mammals. The effect of alternative splicing on the protein domains present in Oct4, Sox2, Klf4 and Nanog were also analyzed. Examination of the expression patterns in human stem cells, iPS cells and normal tissues showed that Oct4, Sox2, Klf4 and Nanog are expressed at similar levels in iPS cells and embryonic stem cells, and expression of all four transcription factors decreases after differentiation. Expression of Klf4 reduced to the least during differentiation, and Klf4 was found to be specifically expressed in several normal tissues, especially the salivary gland. In this paper, we systematically indentified the family proteins of the four transcription factors used to induce pluripotent stem cells, and then analyzed their evolution status, composed of those protein domains, alternative splicing translation, expression status and interaction networks. Those analysis could shed a light for further research of iPS.

PROP1 overexpression in corticotrophinomas: evidence for the role of PROP1 in the maintenance of cells committed to corticotrophic differentiation

OBJECTIVE

The expression of transcription factors involved in early pituitary development, such as PROP1 and POU1F1, has been detected in pituitary adenoma tissues. In this study, we sought to characterize the transcriptional profiles of PROP1, POU1F1, and TBX19 in functioning and nonfunctioning pituitary adenomas in an attempt to identify their roles in tumorigenesis and hormone hypersecretion.

METHODS

RT-qPCR analyses were performed to assess the transcriptional pattern of PROP1, POU1F1, TBX19, and hormone-producing genes in tissue samples of corticotrophinomas (n=10), somatotrophinomas (n=8), and nonfunctioning adenomas (n=6).

RESULTS

Compared with normal pituitary tissue, POU1F1 was overexpressed in somatotrophinomas by 3-fold. PROP1 expression was 18-fold higher in corticotrophinomas, 10-fold higher in somatotrophinomas, and 3-fold higher in nonfunctioning adenomas. TBX19 expression was 27-fold higher in corticotrophinomas. Additionally, the level of TBX19 mRNA positively correlated with that of pro-opiomelanocortin (r=0.49, p=0.014).

CONCLUSIONS

Our data demonstrate that PROP1 is overexpressed in pituitary adenomas, mainly in corticotrophinomas. Together with previously published data showing that patients who harbor PROP1 loss-of-function mutations present a progressive decline in corticotrope function, our results support a role for PROP1 in pituitary tumor development and in the maintenance of cell lineages committed to corticotrophic differentiation.

Paired related homeobox protein 1 is a regulator of stemness in adult neural stem/progenitor cells

Newborn neurons are generated from neural stem cells (NSCs) in two major niches of the adult brain. Maintenance of self-renewal and multipotency of adult NSCs is controlled by multiple transcription factor networks. We show here that paired related homeobox protein Prx1 (MHox1/Prrx1) plays an important role in the maintenance of adult NSCs. Prx1 works with the transcription factor Sox2 as a coactivator, and depletion of Prx1 in cultured adult mouse NSCs reduces their self-renewal. In addition, we find that Prx1 protein is expressed in Sox2(+)/GFAP(+)/Nestin(+) astrocytes in the germinal regions of the adult mouse forebrain. The continuous expression of Prx1 in proliferating adult mouse hippocampal stem/progenitor cells in vivo leads to the generation of radial/horizontal-shaped astrocyte progenitor- and oligodendrocyte progenitor-like cells with no newborn neurons in the neurogenic niche. These data suggest that Prx1 plays an important role as a key switch for neural cell lineage determination and the maintenance of the self-renewal of adult NSCs at several stages in the adult brain.

A novel transcription mechanism activated by ethanol: induction of Slc7a11 gene expression via inhibition of the DNA-binding activity of transcriptional repressor octamer-binding transcription factor 1 (OCT-1)

Solute carrier family 7, member 11 (Slc7a11) is a plasma membrane cystine/glutamate exchanger that provides intracellular cystine to produce glutathione, a major cellular antioxidant. Oxidative and endoplasmic reticulum stresses up-regulate Slc7a11 expression by activation of nuclear factor erythroid 2-related factor 2 and transcription factor 4. This study examined the effect of ethanol on Slc7a11 expression and the underlying mechanism involved. Treatment of mouse hepatic stellate cells with ethanol significantly increased Slc7a11 mRNA and protein levels. Deletion of a 20-bp DNA sequence between -2044 to -2024 upstream of the transcription start site significantly increased basal activity and completely abolished the ethanol-induced activity of the Slc7a11 promoter. This deletion did not affect Slc7a11 promoter activity induced by oxidative or endoplasmic reticulum stress. DNA sequence analysis revealed a binding motif for octamer-binding transcription factor 1 (OCT-1) in the deleted fragment. Mutation of this OCT-1 binding motif resulted in a similar effect as the deletion experiment, i.e. it increased the basal promoter activity and abolished the response to ethanol. Ethanol exposure significantly inhibited OCT-1 binding to the Slc7a11 promoter region, although it did not alter OCT-1 mRNA and protein levels. OCT-1 reportedly functions as either a transcriptional enhancer or repressor, depending on the target genes. Results from this study suggest that OCT-1 functions as a repressor on the Slc7a11 promoter and that ethanol inhibits OCT-1 binding to the Slc7a11 promoter, thereby increasing Slc7a11 expression. Taken together, inhibition of the DNA binding activity of transcriptional repressor OCT-1 is a mechanism by which ethanol up-regulates Slc711 expression.

POU1F1 is a novel fusion partner of NUP98 in acute myeloid leukemia with t(3;11)(p11;p15)

Background

NUP98 gene rearrangements have been reported in acute myeloid leukemia, giving rise to fusion proteins that seem to function as aberrant transcription factors, and are thought to be associated with poor prognosis.

Findings

A patient with treatment-related acute myeloid leukemia presented a t(3;11)(p11;p15) as the only cytogenetic abnormality. FISH and molecular genetic analyses identified a class 1 homeobox gene, POU1F1, located on chromosome 3p11, as the fusion partner of NUP98. In addition, we have found that the patient harbored an FLT3-ITD mutation, which most likely collaborated with the NUP98-POU1F1 fusion gene in malignant transformation.

Conclusions

We have identified POU1F1 as the NUP98 fusion partner in therapy-related AML with a t(3;11)(p11;p15). This is the first POU family member identified as a fusion partner in human cancer.

Homeodomain POU and Abd-A proteins regulate the transcription of pupal genes during metamorphosis of the silkworm, Bombyx mori

A cascade of 20-hydroxyecdysone-mediated gene expression and repression initiates larva-to-pupa metamorphosis. We recently showed that two transcription factors, BmPOUM2 and BmβFTZ-F1, bind to the cis-regulatory elements in the promoter of the gene coding for cuticle protein, BmWCP4, and regulate its expression during Bombyx mori metamorphosis. Here we show that down-regulation of BmPOUM2 expression by RNA interference during the wandering stage resulted in failure to complete metamorphosis. The thorax epidermis of RNA interference-treated larvae became transparent, wing disc growth and differentiation were arrested, and the larvae failed to spin cocoons. Quantitative real-time PCR analysis showed that expression of the genes coding for pupal-specific wing cuticle proteins BmWCP1, BmWCP2, BmWCP3, BmWCP4, BmWCP5, BmWCP6, BmWCP8, and BmWCP9 were down-regulated in BmPOUM2 dsRNA-treated animals, whereas overexpression of BmPOUM2 protein increased the expression of BmWCP4, BmWCP5, BmWCP6, BmWCP7, and BmWCP8. Pull-down assays, far-Western blot, and electrophoretic mobility shift assay showed that the BmPOUM2 protein interacted with another homeodomain transcription factor, BmAbd-A, to induce the expression of BmWCP4. Immunohistochemical localization of BmPOUM2, BmAbd-A, and BmWCP4 proteins revealed that BmAbd-A and BmPOUM2 proteins are colocalized in the wing disc cell nuclei, whereas BmWCP4 protein is localized in the cytoplasm. Together these data suggest that BmPOUM2 interacts with the homeodomain transcription factor BmAbd-A and regulates the expression of BmWCP4 and probably other BmWCPs to complete the larva-to-pupa transformation. Although homeodomain proteins are known to regulate embryonic development, this study showed that these proteins also regulate metamorphosis.

Gbx2 directly restricts Otx2 expression to forebrain and midbrain, competing with class III POU factors

Otx2 plays essential roles in rostral brain development, and its counteraction with Gbx2 has been suggested to determine the midbrain-hindbrain boundary (MHB) in vertebrates. We previously identified the FM enhancer that is conserved among vertebrates and drives Otx2 transcription in forebrain/midbrain from the early somite stage. In this study, we found that the POU homeodomain of class III POU factors (Brn1, Brn2, Brn4, and Oct6) associates with noncanonical target sequence TAATTA in the FM enhancer. MicroRNA-mediated knockdown of Brn2 and Oct6 diminished the FM enhancer activity in anterior neural progenitor cells (NPCs) differentiated from P19 cells. The class III POU factors associate with the FM enhancer in forebrain and midbrain but not in hindbrain. We also demonstrated that the Gbx2 homeodomain recognizes the same target TAATTA in the FM enhancer, and Gbx2 associates with the FM enhancer in hindbrain. Gbx2 misexpression in the anterior NPCs repressed the FM enhancer activity and inhibited Brn2 association with the enhancer, whereas Gbx2 knockdown caused ectopic Brn2 association in the posterior NPCs. These results suggest that class III POU factors and Gbx2 share the same target site, TAATTA, in the FM enhancer and that their region-specific binding restricts Otx2 expression at the MHB.

Diversity, phylogeny and expression patterns of Pou and Six homeodomain transcription factors in hydrozoan jellyfish Craspedacusta sowerbyi

Formation of all metazoan bodies is controlled by a group of selector genes including homeobox genes, highly conserved across the entire animal kingdom. The homeobox genes from Pou and Six classes are key members of the regulation cascades determining development of sensory organs, nervous system, gonads and muscles. Besides using common bilaterian models, more attention has recently been targeted at the identification and characterization of these genes within the basal metazoan phyla. Cnidaria as a diploblastic sister group to bilateria with simple and yet specialized organs are suitable models for studies on the sensory organ origin and the associated role of homeobox genes. In this work, Pou and Six homeobox genes, together with a broad range of other sensory-specific transcription factors, were identified in the transcriptome of hydrozoan jellyfish Craspedacusta sowerbyi. Phylogenetic analyses of Pou and Six proteins revealed cnidarian-specific sequence motifs and contributed to the classification of individual factors. The majority of the Craspedacusta sowerbyi Pou and Six homeobox genes are predominantly expressed in statocysts, manubrium and nerve ring, the tissues with sensory and nervous activities. The described diversity and expression patterns of Pou and Six factors in hydrozoan jellyfish highlight their evolutionarily conserved functions. This study extends the knowledge of the cnidarian genome complexity and shows that the transcriptome of hydrozoan jellyfish is generally rich in homeodomain transcription factors employed in the regulation of sensory and nervous functions.

An RNA-independent linkage of noncoding transcription to long-range enhancer function

The detection of noncoding transcription at multiple enhancers within the mammalian genome raises critical questions regarding whether and how this activity contributes to enhancer function. Here, using in vivo analysis of a human growth hormone (hGH) transgene locus, we report that activation of a domain of noncoding transcription adjacent to the long-range hGH-N enhancer, HSI, is established by the enhancer independent of any interactions with its target promoter. We further demonstrate that the appearance of this enhancer-linked noncoding transcription is temporally and spatially concordant with induction of hGH-N in the embryonic pituitary. Finally, we show that the level of transcriptional enhancement of hGH-N by HSI is directly related to the intensity of HSI-dependent noncoding transcription and is fully independent of the structure of the locally transcribed RNA. These data extend our understanding of the relationship of long-range enhancer activity to enhancer-dependent noncoding transcription and establish a model that may be of general relevance to additional mammalian loci.

Interplay between minor and major groove-binding transcription factors Sox2 and Oct1 in translocation on DNA studied by paramagnetic and diamagnetic NMR

The pathways whereby Sox2 scans DNA to locate its specific binding site are investigated by NMR in specific and nonspecific Sox2·DNA complexes and in a specific ternary complex with Oct1 on the Hoxb1 regulatory element. Direct transfer of Sox2 between nonspecific sites on different DNA molecules occurs without dissociation into free solution at a rate of ∼10(6) M(-1) s(-1), whereas one-dimensional sliding proceeds with a diffusion constant of ≥0.1 μm(2)·s(-1). Translocation of Sox2 from one specific DNA site to another occurs via jumping, involving complete dissociation into free solution (k(d) ∼5-6 s(-1)) followed by reassociation (k(a) ∼5 × 10(8) M(-1) s(-1)). In the presence of Oct1 bound to an adjacent specific site, k(d) is reduced by more than 10-fold. Paramagnetic relaxation measurements, however, demonstrate that sparsely populated (<1%), transient states involving nonspecifically bound Sox2 in rapid exchange with specifically bound Sox2 are sampled in both binary Sox2·DNA- and ternary Oct1·Sox2·Hoxb1-DNA-specific complexes. Moreover, Sox2 modulates the mechanism of translocation of Oct1. Both Sox2 and the Oct1 POU(HD) domain are transiently released from the specific ternary complex by sliding to an adjacent nonspecific site, followed by direct transfer to another DNA molecule, whereas the Oct1 POU(S) domain is fixed to its specific site through direct interactions with Sox2. Intermolecular translocation of POU(HD) results in the formation of a bridged intermediate spanning two DNA molecules, enhancing the probability of complete intermolecular translocation of Oct1. By way of contrast, in the specific Oct1·DNA binary complex, POU(S) undergoes direct intermolecular translocation, whereas POU(HD) scans the DNA by sliding.

Characterization of the intronic portion of cadherin superfamily members, common cancer orchestrators

Cadherins are cell-cell adhesion proteins essential for the maintenance of tissue architecture and integrity, and their impairment is often associated with human cancer. Knowledge regarding regulatory mechanisms associated with cadherin misexpression in cancer is scarce. Specific features of the intronic-structure and intronic-based regulatory mechanisms in the cadherin superfamily are unidentified. This study aims at systematically characterizing the intronic portion of cadherin superfamily members and the identification of intronic regions constituting putative targets/triggers of regulation, using a bioinformatic approach and biological data mining. Our study demonstrates that the cadherin superfamily genes harbour specific characteristics in comparison to all non-cadherin genes, both from the genomic and transcriptional standpoints. Cadherin superfamily genes display higher average total intron number and significantly longer introns than other genes and across the entire vertebrate lineage. Moreover, in the human genome, we observed an uncommon high frequency of MIR (mammalian-wide interspersed repeats) and MaLR (mammalian-wide interspersed repeats, a subtype of LTR) regulatory-associated repetitive elements at 5'-located introns, concomitantly with increased de novo intronic transcription. Using this approach, we identified cadherin intronic-specific sites that may constitute novel targets/triggers of cadherin superfamily expression regulation. These findings pinpoint the need to identify mechanisms affecting particularly MIR and MaLR elements located in introns 2 and 3 of human cadherin genes, possibly important in the expression modulation of this superfamily in homeostasis and cancer.

Phosphorylation of BRN2 modulates its interaction with the Pax3 promoter to control melanocyte migration and proliferation

MITF-M and PAX3 are proteins central to the establishment and transformation of the melanocyte lineage. They control various cellular mechanisms, including migration and proliferation. BRN2 is a POU domain transcription factor expressed in melanoma cell lines and is involved in proliferation and invasion, at least in part by regulating the expression of MITF-M and PAX3. The T361 and S362 residues of BRN2, both in the POU domain, are conserved throughout the POU protein family and are targets for phosphorylation, but their roles in vivo remain unknown. To examine the role of this phosphorylation, we generated mutant BRN2 in which these two residues were replaced with alanines (BRN2TS→BRN2AA). When expressed in melanocytes in vitro or in the melanocyte lineage in transgenic mice, BRN2TS induced proliferation and repressed migration, whereas BRN2AA repressed both proliferation and migration. BRN2TS and BRN2AA bound and repressed the MITF-M promoter, whereas PAX3 transcription was induced by BRN2TS but repressed by BRN2AA. Expression of the BRN2AA transgene in a Mitf heterozygous background and in a Pax3 mutant background enhanced the coat color phenotype. Our findings show that melanocyte migration and proliferation are controlled both through the regulation of PAX3 by nonphosphorylated BRN2 and through the regulation of MITF-M by the overall BRN2 level.

Intra- and intermolecular translocation of the bi-domain transcription factor Oct1 characterized by liquid crystal and paramagnetic NMR

The intra- and intermolecular translocation processes whereby the bi-domain transcription factor Oct1 searches for its specific DNA target site have been investigated by residual dipolar coupling (RDC) and paramagnetic relaxation enhancement (PRE) measurements. The RDC data show that the orientation of the POU(S) and POU(HD) domains of Oct1 relative to the long axis of the DNA is the same for specific and nonspecific complexes with DNA. In the context of the specific Oct1-DNA complex, sparsely-populated, spectroscopically "invisible" states reveal their footprints on the PRE profiles observed for the specific complex. Analysis of the PRE data indicates that the POU(HD) domain searches the DNA primarily by rotation-coupled sliding (intramolecular translocation), while the POU(S) domain functions as an antenna to promote intersegment transfer via intermolecular translocation. The latter involves the formation of a bridged intermediate in which the POU(HD) domain is located on the first DNA molecule and the POU(S) domain on the second. The formation of the bridge intermediate promotes the completion of intermolecular translocation of Oct1 via a first order process involving dissociation and association of the POU(HD) domain from one DNA molecule to another. Thus cross-talk between the POU(S) and POU(HD) domains, each fulfilling different and complementary components of the search process ensures efficient sampling of DNA, thereby facilitating the location of specific Oct1 target sites.

Deregulation of the Pit-1 transcription factor in human breast cancer cells promotes tumor growth and metastasis

The Pit-1 transcription factor (also know as POU1F1) plays a critical role in cell differentiation during organogenesis of the anterior pituitary in mammals and is a transcriptional activator for pituitary gene transcription. Increased expression of Pit-1 has been reported in human tumorigenic breast cells. Here, we found that Pit-1 overexpression or knockdown in human breast cancer cell lines induced profound phenotypic changes in the expression of proteins involved in cell proliferation, apoptosis, and invasion. Some of these protumorigenic effects of Pit-1 were mediated by upregulation of Snai1, an inductor of the epithelial-mesenchymal transition. In immunodeficient mice, Pit-1 overexpression induced tumoral growth and promoted metastasis in lung. In patients with invasive ductal carcinoma of the breast and node-positive tumor, high expression of Pit-1 was significantly correlated with Snai1 positivity. Notably, in these patients elevated expression of Pit-1 was significantly and independently associated with the occurrence of distant metastasis. These findings suggest that Pit-1 could help to make a more accurate prognosis in patients with node-positive breast cancer and may represent a new therapeutic target.

The POU transcription factor Drifter/Ventral veinless regulates expression of Drosophila immune defense genes

Innate immunity operates as a first line of defense in multicellular organisms against infections caused by different classes of microorganisms. Antimicrobial peptides (AMPs) are synthesized constitutively in barrier epithelia to protect against microbial attack and are also upregulated in response to infection. Here, we implicate Drifter/Ventral veinless (Dfr/Vvl), a class III POU domain transcription factor, in tissue-specific regulation of the innate immune defense of Drosophila. We show that Dfr/Vvl is highly expressed in a range of immunocompetent tissues, including the male ejaculatory duct, where its presence overlaps with and drives the expression of cecropin, a potent broad-spectrum AMP. Dfr/Vvl overexpression activates transcription of several AMP genes in uninfected flies in a Toll pathway- and Imd pathway-independent manner. Dfr/Vvl activates a CecA1 reporter gene both in vitro and in vivo by binding to an upstream enhancer specific for the male ejaculatory duct. Further, Dfr/Vvl and the homeodomain protein Caudal (Cad) activate transcription synergistically via this enhancer. We propose that the POU protein Dfr/Vvl acts together with other regulators in a combinatorial manner to control constitutive AMP gene expression in a gene-, tissue-, and sex-specific manner, thus promoting a first-line defense against infection in tissues that are readily exposed to pathogens.

Mutant huntingtin fragment selectively suppresses Brn-2 POU domain transcription factor to mediate hypothalamic cell dysfunction

In polyglutamine diseases including Huntington's disease (HD), mutant proteins containing expanded polyglutamine stretches form nuclear aggregates in neurons. Although analysis of their disease models suggested a significance of transcriptional dysregulation in these diseases, how it mediates the specific neuronal cell dysfunction remains obscure. Here we performed a comprehensive analysis of altered DNA binding of multiple transcription factors using R6/2 HD model mice brains that express an N-terminal fragment of mutant huntingtin (mutant Nhtt). We found a reduction of DNA binding of Brn-2, a POU domain transcription factor involved in differentiation and function of hypothalamic neurosecretory neurons. We provide evidence supporting that Brn-2 loses its function through two pathways, its sequestration by mutant Nhtt and its reduced transcription, leading to reduced expression of hypothalamic neuropeptides. In contrast to Brn-2, its functionally related protein, Brn-1, was not sequestered by mutant Nhtt but was upregulated in R6/2 brain, except in hypothalamus. Our data indicate that functional suppression of Brn-2 together with a region-specific lack of compensation by Brn-1 mediates hypothalamic cell dysfunction by mutant Nhtt.

Genetic regulation of pituitary gland development in human and mouse

Normal hypothalamopituitary development is closely related to that of the forebrain and is dependent upon a complex genetic cascade of transcription factors and signaling molecules that may be either intrinsic or extrinsic to the developing Rathke's pouch. These factors dictate organ commitment, cell differentiation, and cell proliferation within the anterior pituitary. Abnormalities in these processes are associated with congenital hypopituitarism, a spectrum of disorders that includes syndromic disorders such as septo-optic dysplasia, combined pituitary hormone deficiencies, and isolated hormone deficiencies, of which the commonest is GH deficiency. The highly variable clinical phenotypes can now in part be explained due to research performed over the last 20 yr, based mainly on naturally occurring and transgenic animal models. Mutations in genes encoding both signaling molecules and transcription factors have been implicated in the etiology of hypopituitarism, with or without other syndromic features, in mice and humans. To date, mutations in known genes account for a small proportion of cases of hypopituitarism in humans. However, these mutations have led to a greater understanding of the genetic interactions that lead to normal pituitary development. This review attempts to describe the complexity of pituitary development in the rodent, with particular emphasis on those factors that, when mutated, are associated with hypopituitarism in humans.