Period2 3'-UTR and microRNA-24 regulate circadian rhythms by repressing PERIOD2 protein accumulation.

We previously created two PER2::LUCIFERASE (PER2::LUC) circadian reporter knockin mice that differ only in the Per2 3'-UTR region: Per2::Luc, which retains the endogenous Per2 3'-UTR and Per2::LucSV, where the endogenous Per2 3'-UTR was replaced by an SV40 late poly(A) signal. To delineate the in vivo functions of Per2 3'-UTR, we analyzed circadian rhythms of Per2::LucSV mice. Interestingly, Per2::LucSV mice displayed more than threefold stronger amplitude in bioluminescence rhythms than Per2::Luc mice, and also exhibited lengthened free-running periods (∼24.0 h), greater phase delays following light pulse, and enhanced temperature compensation relative to Per2::Luc Analysis of the Per2 3'-UTR sequence revealed that miR-24, and to a lesser degree miR-30, suppressed PER2 protein translation, and the reversal of this inhibition in Per2::LucSV augmented PER2::LUC protein level and oscillatory amplitude. Interestingly, Bmal1 mRNA and protein oscillatory amplitude as well as CRY1 protein oscillation were increased in Per2::LucSV mice, suggesting rhythmic overexpression of PER2 enhances expression of Per2 and other core clock genes. Together, these studies provide important mechanistic insights into the regulatory roles of Per2 3'-UTR, miR-24, and PER2 in Per2 expression and core clock function.

Perilipin+ embryonic preadipocytes actively proliferate along growing vasculatures for adipose expansion.

Despite the growing interest in adipose tissue as a therapeutic target of metabolic diseases, the identity of adipocyte precursor cells (preadipocytes) and the formation of adipose tissue during embryonic development are still poorly understood. Here, we clarified the identity and dynamic processes of preadipocytes in mouse white adipose tissue during embryogenesis through direct examination, lineage tracing and culture systems. Surprisingly, we found that lipid-lacking but perilipin(+) or adiponectin(+) proliferating preadipocytes started to emerge at embryonic day 16.5, and these cells underwent active proliferation until birth. Moreover, these preadipocytes resided as clusters and were distributed along growing adipose vasculatures. Importantly, the embryonic preadipocytes exhibited considerable coexpression of stem cell markers, such as CD24, CD29 and PDGFRα, and a small portion of preadipocytes were derived from PDGFRß(+) mural cells, in contrast to the adult preadipocytes present in the stromal vascular fraction. Further analyses with in vitro and ex vivo culture systems revealed a stepwise but dynamic regulation of preadipocyte formation and differentiation during prenatal adipogenesis. To conclude, we unraveled the identity and characteristics of embryonic preadipocytes, which are crucial for the formation and expansion of adipose tissue during embryogenesis.

The essential role of FKBP38 in regulating phosphatase of regenerating liver 3 (PRL-3) protein stability.

The phosphatase of regenerating liver-3 (PRL-3) is a member of protein tyrosine phosphatases and whose deregulation is implicated in tumorigenesis and metastasis of many cancers. However, the underlying mechanism by which PRL-3 is regulated is not known. In this study, we identified the peptidyl prolyl cis/trans isomerase FK506-binding protein 38 (FKBP38) as an interacting protein of PRL-3 using a yeast two-hybrid system. FKBP38 specifically binds to PRL-3 in vivo, and that the N-terminal region of FKBP38 is crucial for binding with PRL-3. FKBP38 overexpression reduces endogenous PRL-3 expression levels, whereas the depletion of FKBP38 by siRNA increases the level of PRL-3 protein. Moreover, FKBP38 promotes degradation of endogenous PRL-3 protein via protein-proteasome pathway. Furthermore, FKBP38 suppresses PRL-3-mediated p53 activity and cell proliferation. These results demonstrate that FKBP38 is a novel regulator of the oncogenic protein PRL-3 abundance and that alteration in the stability of PRL-3 can have a dramatic impact on cell proliferation. Thus, FKBP38 may play a critical role in tumorigenesis.

A genetic screen for modifiers of Drosophila caspase Dcp-1 reveals caspase involvement in autophagy and novel caspase-related genes.

BACKGROUND: Caspases are cysteine proteases with essential functions in the apoptotic pathway; their proteolytic activity toward various substrates is associated with the morphological changes of cells. Recent reports have described non-apoptotic functions of caspases, including autophagy. In this report, we searched for novel modifiers of the phenotype of Dcp-1 gain-of-function (GF) animals by screening promoter element- inserted Drosophila melanogaster lines (EP lines). RESULTS: We screened approximately 15,000 EP lines and identified 72 Dcp-1-interacting genes that were classified into 10 groups based on their functions and pathways: 4 apoptosis signaling genes, 10 autophagy genes, 5 insulin/IGF and TOR signaling pathway genes, 6 MAP kinase and JNK signaling pathway genes, 4 ecdysone signaling genes, 6 ubiquitination genes, 11 various developmental signaling genes, 12 transcription factors, 3 translation factors, and 11 other unclassified genes including 5 functionally undefined genes. Among them, insulin/IGF and TOR signaling pathway, MAP kinase and JNK signaling pathway, and ecdysone signaling are known to be involved in autophagy. Together with the identification of autophagy genes, the results of our screen suggest that autophagy counteracts Dcp-1-induced apoptosis. Consistent with this idea, we show that expression of eGFP-Atg5 rescued the eye phenotype caused by Dcp-1 GF. Paradoxically, we found that over-expression of full-length Dcp-1 induced autophagy, as Atg8b-GFP, an indicator of autophagy, was increased in the eye imaginal discs and in the S2 cell line. Taken together, these data suggest that autophagy suppresses Dcp-1-mediated apoptotic cell death, whereas Dcp-1 positively regulates autophagy, possibly through feedback regulation. CONCLUSIONS: We identified a number of Dcp-1 modifiers that genetically interact with Dcp-1-induced cell death. Our results showing that Dcp-1 and autophagy-related genes influence each other will aid future investigations of the complicated relationships between apoptosis and autophagy.

Angiogenic role of LYVE-1-positive macrophages in adipose tissue.

Here we report the discovery of a characteristic dense vascular network (DVN) in the tip portion of epididymal adipose tissue in adult mice. The DVN is formed by angiogenesis rather than by vasculogenesis, and has functional blood circulation. This DVN and its subsequent branching may provide a new functional route for adipogenesis. The recruitment, infiltration, and accumulation of bone marrow-derived LYVE-1(+) macrophages in the tip region are crucial for the formation of the DVN. Matrix metalloproteinases (MMPs) and the VEGF-VEGFR2 system are responsible not only for the formation of the DVN, but also for the recruitment and infiltration of LYVE-1(+) macrophages into the epididymal adipose tissue tip region. SDF-1, but not the MCP-1-CCR2 system, is a critical factor in recruitment and ongoing retention of macrophages in this area. We also demonstrate that the tip region of epididymal adipose tissue is highly hypoxic, and thus provides a microenvironment conducive to the high expression and enhanced activities of VEGF, VEGFR2, MMPs, and SDF-1 in autocrine and paracrine manners, to create an ideal niche for the recruitment, retention, and angiogenic action of macrophages. These findings shed light on the complex interplay between macrophage infiltration, angiogenesis, and adipogenesis in the tip region of adult epididymal adipose tissue, and provide novel insight into the regulation of alternative outgrowth of adipose tissue.

Angiopoietin-1 suppresses choroidal neovascularization and vascular leakage.

PURPOSE: To investigate the role of angiopoietin-1 (Ang1) in choroidal neovascularization (CNV) and vascular leakage. METHODS: We generated laser-induced CNV in mice and measured the size of CNV and vascular leakage after intravitreal administration of Ang1. The expressions and distributions of endothelial junctional proteins were analyzed using immunohistochemistry and Western blot. Moreover, we compared the sizes of CNV and vascular leakage in Ang1-overexpressing, Ang1-deficient, and their littermate control mice. In addition, following the transplantation of GFP(+) bone marrow cells into these Ang1-genetically modified mice, we evaluated the recruitment of VEGF-A producing macrophages from the bone marrow after CNV induction. RESULTS: Intravitreal administration of Ang1 was as effective as VEGF-Trap in inhibiting CNV formation. Furthermore, Ang1 suppressed vascular leakage by increasing endothelial junctional proteins, which was more effective than VEGF-Trap. Genetic deletion of Ang1 exacerbated, while overexpression of Ang1 suppressed CNV formation and vascular leakage. We attribute these Ang1-induced, anti-angiogenic, and anti-leakage effects to its inhibitory actions against the recruitment and infiltration of VEGF-A-producing macrophages from bone marrow into the inflammatory lesions. CONCLUSIONS: Ang1 supplementation can be established as a therapeutic strategy to suppress the CNV formation and vascular leakage by inhibiting the recruitment of angiogenic macrophages and tightening the endothelial junctions.

Angiopoietin-1 guides directional angiogenesis through integrin αvß5 signaling for recovery of ischemic retinopathy.

Retinopathy of prematurity (ROP) and proliferative diabetic retinopathy (PDR) are ischemic retinal diseases caused by insufficient vascular network formation and vascular regression in addition to aberrant angiogenesis. We examined the role of angiopoietin-1 (Ang1) in retinal vascular network formation during postnatal development using Ang1 gain- and loss-of-function mouse models, and tested the effects of intraocular administration of Ang1 in an oxygen-induced retinopathy (OIR) mouse model that mimics cardinal features of ROP and PDR. We observed that Ang1 plays a substantial role in the formation of the retinal vascular network during postnatal development and that Ang1 supplementation can rescue vascular retinopathies by simultaneously promoting healthy vascular network formation and inhibiting subsequent abnormal angiogenesis, vascular leakage, and neuronal dysfunction in the retinas of the OIR model. We attribute these Ang1-induced effects to a dual signaling pathway-Tie2 signaling in the vascular region and integrin αvß5 signaling in the astrocytes. The activation of integrin αvß5 signaling promoted fibronectin accumulation and radial distribution along the sprouting endothelial cells, which consequently stimulated guided angiogenesis in the retina. These findings shed light on the role of Ang1 in the recovery of ischemic retinopathies such as ROP, PDR, and retinal vascular occlusive disease.

Altered expression of phosphatase of regenerating liver gene family in non-small cell lung cancer.

Protein tyrosine phophatases (PTPs) are implicated in the tumorigenesis and metastasis of human cancer. The phosphatase of regenerating liver (PRL) gene family, a subgroup of PTPs is also linked to these processes. In many solid cancers, high levels of PRL-3 expression are related with metastasis and poor prognosis. However, the expression patterns of PRL-1 and -2 have not been explored in lung cancer yet. Thus, we investigated the expression levels of PRL-1, -2 and -3 in the tissues of primary lung cancer patients. The protein expression levels of PRL-2, but not PRL-1 and -3 were increased in cancer tissues. However, there was no correlation between mRNA and protein expression levels of the PRLs. Reporter assays showed that PRLs suppressed the activity of the p21 promoter but promoted AP-1 activity. Furthermore, transfection of PRLs showed significantly increased cell proliferation. Therefore, these results suggest that PRL-2 plays an important role in lung cancer and can be a biomarker of lung cancer, substituting for the function of other PRLs.

The BTB/POZ-ZF transcription factor dPLZF is involved in Ras/ERK signaling during Drosophila wing development.

In Drosophila, broad complex, tramtrack, bric à brac (BTB)/poxvirus and zinc finger (POZ) transcription factors are essential regulators of development. We searched the Drosophila genome for BTB/POZ-ZF domains and discovered an unknown Drosophila gene, dPLZF, which encodes an orthologue of human PLZF. We then characterized the biological function of the dPLZF via genetic interaction analysis. Ectopic expression of dPLZF in the wing induced extra vein formation during wing development in Drosophila. Genetic interactions between dPLZF and Ras or extracellular signal-regulated kinase (ERK) significantly enhanced the formation of vein cells. On the other hand, loss-of-function mutations in dPLZF resulted in a dramatic suppression of the extra and ectopic vein formation induced by elevated Ras/ERK signaling. Moreover, dPLZF activity upregulated the expression of rhomboid (rho) and spitz, which perform crucial functions in vein cell formation in the developing wing. These results indicate that dPLZF is a transcription factor controlled by the Ras/ERK signaling pathway, which is a prominent regulator of vein cell formation during wing development in Drosophila.

Downregulation of p53 by phosphatase of regenerating liver 3 is mediated by MDM2 and PIRH2.

AIMS: The phosphatase of regenerating liver (PRL) family is related to tumorigenesis and metastasis in various cancer types. Its overexpression increases cell motility and proliferation via the downregulation of p21 expression. In a previous study, we reported that PRL-1 downregulates p53 and is a target gene of p53. In this study, we investigated whether a member of the PRL family, PRL-3, could regulate p53 like PRL-1 in cancer cells. MAIN METHODS: To elucidate the role of PRL-3 in regulating p53 in cancer cells, we used a cell culture system to measure protein level, transcriptional level, apoptosis or localization. KEY FINDINGS: We determined that PRL-3 overexpression reduced the activity of the p21 and p53 reporters. Additionally, the levels of endogenous and exogenous p53 protein were reduced in cells transiently expressing PRL-3, whereas the ablation of PRL-3 by siRNA increased levels of the p53 protein. The downregulation of p53 by PRL-3 inhibited p53-mediated apoptosis. However, the phosphatase-dead mutant C104S, prenylated-site mutant C170S, and C104S/C170S PRL-3 evidenced minimal effects on the downregulation of p53 protein as compared with wild-type PRL-3. Further examinations revealed that PRL-3 expression reduced the stability of p53 by inducing the transcription of p53 induced protein with a RING-H2 domain (PIRH2) through early growth response (EGR) and by increasing the phosphorylation of mouse double minute 2 (MDM2), and then both negatively regulated p53. SIGNIFICANCE: These findings demonstrated that PRL-3, like PRL-1, can negatively regulate p53 via the activation of PIRH2 and MDM2 in cancer cells.

COMP-angiopoietin-1 promotes wound healing through enhanced angiogenesis, lymphangiogenesis, and blood flow in a diabetic mouse model.

Microvascular dysfunction is a major cause of impaired wound healing seen in diabetic patients. Therefore, reestablishment of structural and functional microvasculature could be beneficial to promote wound healing in these patients. Angiopoietin-1 (Ang1) is a specific growth factor functioning to generate a stable and functional vasculature through the Tie2 and Tie1 receptors. Here we determined the effectiveness of cartilage oligomeric matrix protein (COMP)-Ang1, a soluble, stable, and potent form of Ang1, on promotion of healing in cutaneous wounds of diabetic mice. An excisional full-thickness wound was made in the dorsal side of the tail of diabetic (db/db) mice, and mice were then treated systemically with adenovirus (Ade) encoding COMP-Ang1 or with control virus encoding beta-gal (Ade-beta-gal) or treated topically with recombinant COMP-Ang1 protein or BSA. Time course observations revealed that mice treated with Ade-COMP-Ang1 or COMP-Ang1 protein showed accelerated wound closure and epidermal and dermal regeneration, enhanced angiogenesis and lymphangiogenesis, and higher blood flow in the wound region compared with mice treated with control virus or BSA. COMP-Ang1 promotion of wound closure and angiogenesis was not dependent on endothelial nitric oxide synthase or inducible nitric oxide synthase alone. Taken together, these findings indicate that COMP-Ang1 can promote wound healing in diabetes through enhanced angiogenesis, lymphangiogenesis, and blood flow.

Identification of an enhancer region in the mouse ephA8 locus directing expression to the anterior region of the dorsal mesencephalon.

Eph receptors and ephrins are dynamically expressed in a wide range of regions of the vertebrate during embryogenesis. The dorsal mesencephalon appears to be segmented into two broad regions demarcated by the mutually exclusive expression of EphA receptors and ephrinA ligands. It is of considerable interest to elucidate how these expression domains are established in the development of the mesencephalon. In this study, we used a transgenic approach to define the cis-acting DNA regulatory elements involved in the anterior mesencephalon-specific expression of the mouse ephA8 gene. Our analyses of the temporal and spatial expression patterns of various ephA8/lacZ gene fusions in transgenic mice revealed that the 10-kb genomic DNA 5' immediately upstream of the ephA8 coding sequence is capable of directing lacZ expression in an ephA8-specific manner. Further deletion analyses of the ephA8 genomic region led to the identification of a 1-kb enhancer region, which directs expression in the embryo to the anterior region of the developing midbrain. This ephA8-specific regulatory DNA sequences can now be used in biochemical analyses to identify proteins modulating the anterior differentiation of the optic tectum, and in functional analyses to direct the expression of other developmentally important genes to this region.

Nuclear proteins that bind to metal response element a (MREa) in the Wilson disease gene promoter are Ku autoantigens and the Ku-80 subunit is necessary for basal transcription of the WD gene.

Wilson disease (WD), an inherited disorder affecting copper metabolism, is characterized by hepatic cirrhosis and neuronal degeneration, which result from toxic levels of copper that accumulate in the liver and brain, respectively. We reported previously that the approximately 1.3-kb promoter of the WD gene contains four metal response elements (MREs). Among the four MREs, MREa plays the most important role in the transcriptional activation of the WD promoter. Electrophoretic mobility shift assays (EMSAs) using synthetic MREa and an oligonucleotide containing the binding site for transcription factor Sp1 revealed the presence of nuclear factors that bind specifically to MREa. Two MREa-binding proteins of 70 and 82 kDa were purified using avidin-biotin affinity chromatography. Amino acid sequences of peptides from each protein were found to be highly homologous to the Ku proteins. Immunoblot analysis and EMSAs showed that the MREa-binding proteins are immunologically related to the Ku proteins. To study further the functional significance of these Ku-related proteins in transcriptional regulation of the WD gene, we performed RNA interference (RNAi) assays using a Ku-80 inverted-repeat gene to inhibit expression of the Ku-80 gene in vivo. Results of the RNAi assays showed that expression of the Ku-80 protein was suppressed in transfected cells, which in turn led to the suppression of the WD gene. In addition, a truncated Ku-80 (DeltaKu-80) mutant inhibited WD promoter activity in HepG2 cells in a dominant-negative manner. We also found that WD promoter activity was decreased in Xrs5 cells, which, unlike the CHO-K1 cells, are defective in the Ku-80 protein. When Ku-80 cDNA was transfected into Xrs5 and CHO cells, WD promoter activity was recovered only in Xrs5 cells. Taken together, our findings suggest that the Ku-80 subunit is required for constitutive expression of the WD gene.