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1.
BMC Cancer ; 22(1): 526, 2022 May 11.
Article in English | MEDLINE | ID: mdl-35545761

ABSTRACT

BACKGROUND: A current critical need remains in the identification of prognostic and predictive markers in early breast cancer. It appears that a distinctive trait of cancer cells is their addiction to hyperactivation of ribosome biogenesis. Thus, ribosome biogenesis might be an innovative source of biomarkers that remains to be evaluated. METHODS: Here, fibrillarin (FBL) was used as a surrogate marker of ribosome biogenesis due to its essential role in the early steps of ribosome biogenesis and its association with poor prognosis in breast cancer when overexpressed. Using 3,275 non-metastatic primary breast tumors, we analysed FBL mRNA expression levels and protein nucleolar organisation. Usage of TCGA dataset allowed transcriptomic comparison between the different FBL expression levels-related breast tumours. RESULTS: We unexpectedly discovered that in addition to breast tumours expressing high level of FBL, about 10% of the breast tumors express low level of FBL. A correlation between low FBL mRNA level and lack of FBL detection at protein level using immunohistochemistry was observed. Interestingly, multivariate analyses revealed that these low FBL tumors displayed poor outcome compared to current clinical gold standards. Transcriptomic data revealed that FBL expression is proportionally associated with distinct amount of ribosomes, low FBL level being associated with low amount of ribosomes. Moreover, the molecular programs supported by low and high FBL expressing tumors were distinct. CONCLUSION: Altogether, we identified FBL as a powerful ribosome biogenesis-related independent marker of breast cancer outcome. Surprisingly we unveil a dual association of the ribosome biogenesis FBL factor with prognosis. These data suggest that hyper- but also hypo-activation of ribosome biogenesis are molecular traits of distinct tumors.


Subject(s)
Breast Neoplasms , Biomarkers/metabolism , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Chromosomal Proteins, Non-Histone , Female , Humans , RNA, Messenger/genetics , RNA, Messenger/metabolism , Ribosomes/genetics , Ribosomes/metabolism
2.
Dev Biol ; 437(1): 1-16, 2018 05 01.
Article in English | MEDLINE | ID: mdl-29477341

ABSTRACT

Fibrillarin (Fbl) is a highly conserved protein that plays an essential role in ribosome biogenesis and more particularly in the methylation of ribosomal RNAs and rDNA histones. In cellular models, FBL was shown to play an important role in tumorigenesis and stem cell differentiation. We used the zebrafish as an in vivo model to study Fbl function during embryonic development. We show here that the optic tectum and the eye are severely affected by Fbl depletion whereas ventral regions of the brain are less impacted. The morphogenesis defects are associated with impaired neural differentiation and massive apoptosis. Polysome gradient experiments show that fbl mutant larvae display defects in ribosome biogenesis and activity. Strikingly, flow cytometry analyses revealed different S-phase profiles between wild-type and mutant cells, suggesting a defect in S-phase progression.


Subject(s)
Cell Differentiation/genetics , Chromosomal Proteins, Non-Histone/metabolism , Mesencephalon/embryology , Retina/embryology , S Phase/genetics , Animals , Apoptosis , Larva/metabolism , Mesencephalon/metabolism , Morphogenesis/genetics , Neurogenesis/genetics , RNA, Ribosomal/metabolism , Retina/metabolism , Zebrafish/embryology
3.
Curr Opin Genet Dev ; 34: 61-70, 2015 Oct.
Article in English | MEDLINE | ID: mdl-26343009

ABSTRACT

Although considered a 'house-keeping' function, ribosome biogenesis is regulated differently between cells and can be modulated in a cell-type-specific manner. These differences are required to generate specialized ribosomes that contribute to the translational control of gene expression by selecting mRNA subsets to be translated. Thus, differences in ribosome biogenesis between stem and differentiated cells indirectly contribute to determine cell identity. The concept of the existence of stem cell-specific mechanisms of ribosome biogenesis has progressed from an attractive theory to a useful working model with important implications for basic and medical research.


Subject(s)
Cell Differentiation/genetics , RNA, Ribosomal/genetics , Ribosomes/genetics , Stem Cells/metabolism , Animals , Homeostasis/genetics , Humans , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , Ribosomes/metabolism , Stem Cells/cytology , Tumor Suppressor Protein p53/genetics
4.
Development ; 140(24): 4860-9, 2013 Dec.
Article in English | MEDLINE | ID: mdl-24198278

ABSTRACT

Investigating neural stem cell (NSC) behaviour in vivo, which is a major area of research, requires NSC models to be developed. We carried out a multilevel characterisation of the zebrafish embryo peripheral midbrain layer (PML) and identified a unique vertebrate progenitor population. Located dorsally in the transparent embryo midbrain, these large slow-amplifying progenitors (SAPs) are accessible for long-term in vivo imaging. They form a neuroepithelial layer adjacent to the optic tectum, which has transitory fast-amplifying progenitors (FAPs) at its margin. The presence of these SAPs and FAPs in separate domains provided the opportunity to data mine the ZFIN expression pattern database for SAP markers, which are co-expressed in the retina. Most of them are involved in nucleotide synthesis, or encode nucleolar and ribosomal proteins. A mutant for the cad gene, which is strongly expressed in the PML, reveals severe midbrain defects with massive apoptosis and sustained proliferation. We discuss how fish midbrain and retina progenitors might derive from ancient sister cell types and have specific features that are not shared with other SAPs.


Subject(s)
Mesencephalon/embryology , Mesencephalon/metabolism , Neural Stem Cells/metabolism , Retina/metabolism , Zebrafish/embryology , Animals , Cell Cycle , Cell Differentiation/genetics , Cell Proliferation , Cells, Cultured , Embryo, Nonmammalian/metabolism , Gene Expression Regulation, Developmental , Gene Regulatory Networks , Mitosis , Morphogenesis
5.
Dev Dyn ; 240(10): 2354-63, 2011 Oct.
Article in English | MEDLINE | ID: mdl-21932313

ABSTRACT

The highly conserved POU genes encode homeodomain transcription factors involved in various developmental events, with some, the Brn genes, playing key roles in neurogenesis. We investigated the evolutionary relationships between these genes, by studying the POU gene complement of a model teleost, the medaka (Oryzias latipes). We identified 17 POU genes and carried out a comprehensive in situ hybridization analysis focusing on the optic tectum, a cortical structure of the mesencephalon, in which cell positions and their differentiation states are spatially and temporally correlated. Six POU genes displayed patterned expression in the optic tectum: two genes were expressed in the center of the organ (a zone with differentiated neurons), two in an intermediate zone in which cells exit the cell cycle and two in the peripheral proliferation zone. These results suggest that POU genes may play key roles in both late neurogenesis and in multipotent neural progenitors.


Subject(s)
Oryzias/anatomy & histology , Oryzias/genetics , Oryzias/metabolism , POU Domain Factors/genetics , POU Domain Factors/metabolism , Superior Colliculi/metabolism , Animals , Evolution, Molecular , Gene Expression Regulation, Developmental , Genome , Genome-Wide Association Study , Molecular Sequence Data , POU Domain Factors/classification , Phylogeny , Somites/embryology , Superior Colliculi/cytology , Superior Colliculi/embryology
6.
J Neurosci ; 30(48): 16383-90, 2010 Dec 01.
Article in English | MEDLINE | ID: mdl-21123584

ABSTRACT

The adult mammalian brain and spinal cord contain glial precursors that express platelet-derived growth factor receptor α subunit (PDGFRA) and the NG2 proteoglycan. These "NG2 cells" descend from oligodendrocyte precursors in the perinatal CNS and continue to generate myelinating oligodendrocytes in the gray and white matter of the postnatal brain. It has been proposed that NG2 cells can also generate reactive astrocytes at sites of CNS injury or demyelination. To test this we examined the fates of PDGFRA/NG2 cells in the mouse spinal cord during experimental autoimmune encephalomyelitis (EAE)--a demyelinating condition that models some aspects of multiple sclerosis in humans. We administered tamoxifen to Pdgfra-CreER(T2):Rosa26R-YFP mice to induce yellow fluorescent protein (YFP) expression in PDGFRA/NG2 cells and their differentiated progeny. We subsequently induced EAE and observed a large (>4-fold) increase in the local density of YFP(+) cells, >90% of which were oligodendrocyte lineage cells. Many of these became CC1-positive, NG2-negative differentiated oligodendrocytes that expressed myelin markers CNP and Tmem10/Opalin. PDGFRA/NG2 cells generated very few GFAP(+)-reactive astrocytes (1-2% of all YFP(+) cells) or NeuN(+) neurons (<0.02%). Thus, PDGFRA/NG2 cells act predominantly as a reservoir of new oligodendrocytes in the demyelinated spinal cord.


Subject(s)
Antigens/physiology , Astrocytes/physiology , Encephalomyelitis, Autoimmune, Experimental/physiopathology , Neurogenesis/physiology , Neuroglia/physiology , Oligodendroglia/physiology , Proteoglycans/physiology , Animals , Astrocytes/cytology , Demyelinating Diseases/metabolism , Demyelinating Diseases/pathology , Demyelinating Diseases/physiopathology , Encephalomyelitis, Autoimmune, Experimental/metabolism , Encephalomyelitis, Autoimmune, Experimental/pathology , Female , Male , Mice , Mice, Inbred C57BL , Mice, Inbred CBA , Mice, Transgenic , Neuroglia/cytology , Oligodendroglia/cytology
7.
Cell Stem Cell ; 6(6): 578-90, 2010 Jun 04.
Article in English | MEDLINE | ID: mdl-20569695

ABSTRACT

After central nervous system (CNS) demyelination-such as occurs during multiple sclerosis-there is often spontaneous regeneration of myelin sheaths, mainly by oligodendrocytes but also by Schwann cells. The origins of the remyelinating cells have not previously been established. We have used Cre-lox fate mapping in transgenic mice to show that PDGFRA/NG2-expressing glia, a distributed population of stem/progenitor cells in the adult CNS, produce the remyelinating oligodendrocytes and almost all of the Schwann cells in chemically induced demyelinated lesions. In contrast, the great majority of reactive astrocytes in the vicinity of the lesions are derived from preexisting FGFR3-expressing cells, likely to be astrocytes. These data resolve a long-running debate about the origins of the main players in CNS remyelination and reveal a surprising capacity of CNS precursors to generate Schwann cells, which normally develop from the embryonic neural crest and are restricted to the peripheral nervous system.


Subject(s)
Demyelinating Diseases/metabolism , Multiple Sclerosis/metabolism , Nerve Regeneration , Oligodendroglia/metabolism , Schwann Cells/metabolism , Adult Stem Cells/metabolism , Adult Stem Cells/pathology , Animals , Astrocytes/metabolism , Astrocytes/pathology , Basic Helix-Loop-Helix Transcription Factors/biosynthesis , Basic Helix-Loop-Helix Transcription Factors/genetics , Cells, Cultured , Central Nervous System/drug effects , Central Nervous System/pathology , Central Nervous System/surgery , Demyelinating Diseases/chemically induced , Demyelinating Diseases/genetics , Demyelinating Diseases/pathology , Demyelinating Diseases/physiopathology , Disease Models, Animal , Female , Integrases/genetics , Lysophosphatidylcholines/administration & dosage , Mice , Mice, Transgenic , Microscopy , Multiple Sclerosis/genetics , Multiple Sclerosis/pathology , Multiple Sclerosis/physiopathology , Nerve Tissue Proteins/biosynthesis , Nerve Tissue Proteins/genetics , Oligodendrocyte Transcription Factor 2 , Oligodendroglia/pathology , Receptor, Fibroblast Growth Factor, Type 3/biosynthesis , Receptor, Fibroblast Growth Factor, Type 3/genetics , Receptor, Platelet-Derived Growth Factor alpha/biosynthesis , Receptor, Platelet-Derived Growth Factor alpha/genetics , Schwann Cells/pathology
8.
Dev Neurobiol ; 70(10): 693-713, 2010 Sep.
Article in English | MEDLINE | ID: mdl-20506557

ABSTRACT

Few adult neural stem cells have been characterized in vertebrates. Although teleosts continually generate new neurons in many regions of the brain after embryogenesis, only two types of neural stem cells (NSCs) have been reported in zebrafish: glial cells in the forebrain resembling mammalian NSCs, and neuroepithelial cells in the cerebellum. Here, following our previous studies on dividing progenitors (Nguyen et al. [1999]: J Comp Neurol 413:385-404.), we further evidenced NSCs in the optic tectum (OT) of juvenile and adult in the medaka, Oryzias latipes. To detect very slowly cycling progenitors, we did not use the commonly used BrdU/PCNA protocol, in which PCNA may not be present during a transiently quiescent state. Instead, we report the optimizations of several protocols involving long subsequent incubations with two thymidine analogs (IdU and CldU) interspaced with long chase times between incubations. These protocols allowed us to discriminate and localize fast and slow cycling cells in OT of juvenile and adult in the medaka. Furthermore, we showed that adult OT progenitors are not glia, as they express neither brain lipid-binding protein (BLBP) nor glial fibrillary acidic protein (GFAP). We also showed that expression of pluripotency-associated markers (Sox2, Musashi1 and Bmi1) colocalized with OT progenitors. Finally, we described the spatio-temporally ordered population of NSCs and progenitors in the medaka OT. Hence, the medaka appears as an invaluable model for studying neural progenitors that will open the way to further exciting comparative studies of neural stem cells in vertebrates.


Subject(s)
Cell Proliferation , Models, Animal , Neurogenesis/physiology , Neurons/cytology , Oryzias/anatomy & histology , Stem Cells/cytology , Superior Colliculi/cytology , Animals , Biomarkers/metabolism , Cell Differentiation/physiology , Cell Lineage/physiology , Neurons/metabolism , Oryzias/growth & development , Oryzias/metabolism , Pluripotent Stem Cells/cytology , Pluripotent Stem Cells/metabolism , Stem Cells/metabolism , Superior Colliculi/growth & development , Superior Colliculi/metabolism , Thymidine/analogs & derivatives , Thymidine/metabolism , Time Factors , Transcription Factors/metabolism
9.
Neuron Glia Biol ; 5(3-4): 57-67, 2009 Nov.
Article in English | MEDLINE | ID: mdl-20346197

ABSTRACT

Oligodendrocyte precursors (OLPs or 'NG2 cells') are abundant in the adult mouse brain, where they continue to proliferate and generate new myelinating oligodendrocytes. By cumulative BrdU labelling, we estimated the cell cycle time TC and the proportion of NG2 cells that is actively cycling (the growth fraction) at approximately postnatal day 6 (P6), P60, P240 and P540. In the corpus callosum, TC increased from <2 days at P6 to approximately 9 days at P60 to approximately 70 days at P240 and P540. In the cortex, TC increased from approximately 2 days to >150 days over the same period. The growth fraction remained relatively invariant at approximately 50% in both cortex and corpus callosum - that is, similar numbers of mitotically active and inactive NG2 cells co-exist at all ages. Our data imply that a stable population of quiescent NG2 cells appears before the end of the first postnatal week and persists throughout life. The mitotically active population acts as a source of new oligodendrocytes during adulthood, while the biological significance of the quiescent population remains to be determined. We found that the mitotic status of adult NG2 cells is unrelated to their developmental site of origin in the ventral or dorsal telencephalon. We also report that new oligodendrocytes continue to be formed at a slow rate from NG2 cells even after P240 (8 months of age).


Subject(s)
Aging/physiology , Antigens/metabolism , Brain/cytology , Brain/growth & development , Cell Cycle/physiology , Oligodendroglia/physiology , Proteoglycans/metabolism , Age Factors , Animals , Bromodeoxyuridine/metabolism , Cell Count/methods , Cell Cycle/drug effects , Estrogen Antagonists/pharmacology , Gene Expression Regulation, Developmental/drug effects , Gene Expression Regulation, Developmental/physiology , Luminescent Proteins/genetics , Mice , Mice, Transgenic , Oligodendroglia/metabolism , Receptor, Platelet-Derived Growth Factor alpha/genetics , Tamoxifen/pharmacology
10.
Nat Neurosci ; 11(12): 1392-401, 2008 Dec.
Article in English | MEDLINE | ID: mdl-18849983

ABSTRACT

Platelet-derived growth factor alpha receptor (PDGFRA)/NG2-expressing glia are distributed throughout the adult CNS. They are descended from oligodendrocyte precursors (OLPs) in the perinatal CNS, but it is not clear whether they continue to generate myelinating oligodendrocytes or other differentiated cells during normal adult life. We followed the fates of adult OLPs in Pdgfra-creER(T2)/Rosa26-YFP double-transgenic mice and found that they generated many myelinating oligodendrocytes during adulthood; >20% of all oligodendrocytes in the adult mouse corpus callosum were generated after 7 weeks of age, raising questions about the function of the late-myelinating axons. OLPs also produced some myelinating cells in the cortex, but the majority of adult-born cortical cells did not appear to myelinate. We found no evidence for astrocyte production in gray or white matter. However, small numbers of projection neurons were generated in the forebrain, especially in the piriform cortex, which is the main target of the olfactory bulb.


Subject(s)
Adult Stem Cells/physiology , Antigens/metabolism , Cerebral Cortex/cytology , Neurons/physiology , Oligodendroglia/physiology , Proteoglycans/metabolism , Receptor, Platelet-Derived Growth Factor alpha/physiology , 2',3'-Cyclic-Nucleotide Phosphodiesterases/metabolism , Adult Stem Cells/drug effects , Animals , Basic Helix-Loop-Helix Transcription Factors/metabolism , Bromodeoxyuridine/metabolism , Cell Differentiation/drug effects , Cell Differentiation/physiology , Cerebral Cortex/physiology , Estrogen Antagonists/pharmacology , Gene Expression Regulation/drug effects , Gene Expression Regulation/genetics , Humans , Luminescent Proteins/biosynthesis , Luminescent Proteins/genetics , Mice , Mice, Transgenic , Myelin Basic Protein/metabolism , Nerve Tissue Proteins/metabolism , Neural Pathways/physiology , Oligodendrocyte Transcription Factor 2 , Phosphopyruvate Hydratase/metabolism , Proteins/genetics , Proteins/metabolism , RNA, Untranslated , Receptor, Fibroblast Growth Factor, Type 3/genetics , Receptor, Platelet-Derived Growth Factor alpha/genetics , SOXE Transcription Factors/metabolism , Tamoxifen/pharmacology
11.
Dev Biol ; 309(1): 1-17, 2007 Sep 01.
Article in English | MEDLINE | ID: mdl-17559827

ABSTRACT

Through whole-mount in situ hybridisation screen on medaka (Oryzias latipes) brain, Ol-insm1b, a member of the Insm1/Mlt1 subfamily of SNAG-domain containing genes, has been isolated. It is strongly expressed during neurogenesis and pancreas organogenesis, with a pattern that suggests a role in cell cycle exit. Here, we describe Ol-insm1b expression pattern throughout development and in adult brain, and we report on its functional characterisation. Our data point to a previously unravelled role for Ol-insm1b as a down-regulator of cell proliferation during development, as it slows down the cycle without triggering apoptosis. Clonal analysis demonstrates that this effect is cell-autonomous, and, through molecular dissection studies, we demonstrate that it is likely to be non-transcriptional, albeit mediated by zinc-finger domains. Additionally, we report that Ol-insm1b mRNA, when injected in one cell of two-cell stage embryos, exhibits a surprising behaviour: it does not spread uniformly amongst daughter cells but remains cytoplasmically localised in the progeny of the injected blastomere. Our experiments suggest that Insm1 is a negative regulator of cell proliferation, possibly through mechanisms that do not involve modulation of transcription.


Subject(s)
Brain/metabolism , Cell Cycle/physiology , Fish Proteins/metabolism , Gene Expression Regulation, Developmental , Oryzias/metabolism , Transcription Factors/metabolism , Amino Acid Sequence , Animals , Brain/embryology , Brain/growth & development , Embryo, Nonmammalian/metabolism , Molecular Sequence Data , Oryzias/embryology , Oryzias/growth & development , Phylogeny
12.
Development ; 131(6): 1289-98, 2004 Mar.
Article in English | MEDLINE | ID: mdl-14960493

ABSTRACT

Sonic hedgehog (SHH) and fibroblast growth factor 2 (FGF2) can both induce neocortical precursors to express the transcription factor OLIG2 and generate oligodendrocyte progenitors (OLPs) in culture. The activity of FGF2 is unaffected by cyclopamine, which blocks Hedgehog signalling, demonstrating that the FGF pathway to OLP production is Hedgehog independent. Unexpectedly, SHH-mediated OLP induction is blocked by PD173074, a selective inhibitor of FGF receptor (FGFR) tyrosine kinase. SHH activity also depends on mitogen-activated protein kinase (MAPK) but SHH does not itself activate MAPK. Instead, constitutive activity of FGFR maintains a basal level of phosphorylated MAPK that is absolutely required for the OLIG2- and OLP-inducing activities of SHH. Stimulating the MAPK pathway with a retrovirus encoding constitutively active RAS shows that the requirement for MAPK is cell-autonomous, i.e. MAPK is needed together with SHH signalling in the cells that become OLPs.


Subject(s)
Fibroblast Growth Factors/metabolism , Mitogen-Activated Protein Kinases/metabolism , Neocortex/embryology , Signal Transduction/physiology , Trans-Activators/metabolism , Animals , Basic Helix-Loop-Helix Transcription Factors , Fibroblast Growth Factor 2/metabolism , Hedgehog Proteins , Mice , Neocortex/metabolism , Nerve Tissue Proteins/metabolism , Oligodendrocyte Transcription Factor 2 , Oligodendroglia/metabolism , Receptor Protein-Tyrosine Kinases/metabolism , Receptor, Fibroblast Growth Factor, Type 1 , Receptors, Fibroblast Growth Factor/metabolism
13.
J Neurochem ; 82(5): 1199-207, 2002 Sep.
Article in English | MEDLINE | ID: mdl-12358767

ABSTRACT

The pituitary adenylate cyclase-activating polypeptide type-1 receptor (PAC1) has been involved in the survival and differentiation of neuroblasts during development. This study examined the effects of various neurotrophins on the activity of the mouse PAC1 promoter/luciferase reporter constructs in rat PC12 cells and in 8-day-old mouse cerebellar granule cells. In PC12 cells, both differentiating factors such as nerve growth factor (NGF) and mitogens such as epidermal growth factor (EGF) and insulin growth factor-1 (IGF-1) up-regulated PAC1 promoter activity by 2-4-fold in a concentration-dependent manner. Although PACAP differentiated the PC12 cells, it had no effect on the PAC1 promoter and antagonized the stimulatory effect of NGF. In cerebellar granule cells, IGF-1 and brain-derived neurotrophic factor (BDNF) also stimulated the activity of the PAC1 promoter. NGF and IGF-1 increased endogenous PAC1 mRNA levels, and the NGF-induced up-regulation is the result of an increase in transcription from PAC1 promoter instead of an increase in mRNA stability. The mitogen-activated protein kinase (MAPK) kinase inhibitor, PD98059, prevented the transcriptional effects both in PC12 and cerebellar granule cells. Moreover, expression of dominant-negative Ras protein in PC12 cells also prevented the NGF effect. Our results show that the PAC1 promoter can be up-regulated by diverse neurotrophins via an MAPK-dependent pathway and suggest a role for the Ras protein.


Subject(s)
MAP Kinase Signaling System/physiology , Nerve Growth Factors/pharmacology , Neurons/metabolism , Promoter Regions, Genetic/drug effects , Receptors, Pituitary Hormone/genetics , ras Proteins/metabolism , Animals , Brain-Derived Neurotrophic Factor/pharmacology , Cells, Cultured , Cerebellum/cytology , Cerebellum/drug effects , Cerebellum/metabolism , Insulin-Like Growth Factor I/pharmacology , MAP Kinase Signaling System/drug effects , Mice , Nerve Growth Factor/pharmacology , Neurons/cytology , Neurons/drug effects , Neuropeptides/pharmacology , PC12 Cells , Phosphatidylinositol 3-Kinases/metabolism , Pituitary Adenylate Cyclase-Activating Polypeptide , Promoter Regions, Genetic/physiology , RNA, Messenger/metabolism , Rats , Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide , Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide , Receptors, Pituitary Hormone/metabolism , Transcription, Genetic/drug effects , Up-Regulation/drug effects
14.
Biochim Biophys Acta ; 1576(1-2): 157-62, 2002 Jun 07.
Article in English | MEDLINE | ID: mdl-12031496

ABSTRACT

Regulations of the PACAP type 1 (PAC1) receptor expression have been described in the brain and the anterior pituitary. To understand the molecular mechanisms underlying mouse PAC1 gene regulation, we first mapped its transcription start sites (tss). PAC1 receptor RNA initiates from two major sites in embryos and adult tissues. Functional analysis revealed a basal promoter within the first 180 bp upstream of transcription start. Negative regulatory sequences upstream of this minimal promoter control the cell type-specific transcription of a luciferase reporter gene. Zac1, a zinc finger protein mainly expressed in the brain and the pituitary gland, binds to a GC-rich motif of the promoter regulatory elements. The Zac1 DNA binding site is required to positive and negative regulations of the promoter. Our findings provide bases for future studies on the regulatory elements controlling PAC1 gene transcription and demonstrate the PAC1 receptor promoter as a target of Zac1.


Subject(s)
Cell Cycle Proteins/metabolism , Genes, Tumor Suppressor , Receptors, Pituitary Hormone/genetics , Trans-Activators/metabolism , Transcription Factors , Animals , Binding Sites , Brain/metabolism , Cell Cycle Proteins/genetics , Cell Line , Cloning, Molecular , DNA/isolation & purification , DNA/metabolism , Gene Expression Regulation , Genes, Regulator , Genes, Reporter , Genomic Library , Luciferases/genetics , Mice , Pituitary Gland/metabolism , Promoter Regions, Genetic , Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide , Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide , Trans-Activators/genetics , Transcription, Genetic , Transfection
15.
Endocrinology ; 143(4): 1253-9, 2002 Apr.
Article in English | MEDLINE | ID: mdl-11897681

ABSTRACT

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a potentiator of glucose-induced insulin secretion. PACAP binds to a PACAP-specific receptor (PAC1) and to VPAC receptors (VPAC1 and VPAC2), which share high affinity for vasoactive intestinal polypeptide (VIP). In the present study, the molecular expression of PACAP receptor isoforms and the signaling pathways involved in the insulin secretory effect of PACAP were investigated in isolated rat and mouse pancreatic islets. mRNA encoding PAC1-short, -hop, and -very short variants, as well as VPAC1 and VPAC2, were expressed in pancreatic islets. PACAP and VIP were equipotent in potentiating glucose-induced insulin release. Both peptides were also equipotent in increasing cAMP production, but PACAP was more efficient than VIP. Unlike carbachol, PACAP and VIP had no effect on inositol phosphate production. In the PAC1-deficient mouse, the insulinotropic effect of PACAP was reduced, and its differential effect on cAMP production was abolished, whereas the effects of VIP remained unchanged. These results clearly show that the insulinotropic effect of PACAP involved both VPAC and PAC1. The PAC1 variants expressed in rat and mouse pancreatic islets seem to be coupled to adenylate cyclase but not to PLC.


Subject(s)
Adenylyl Cyclases/metabolism , Insulin/metabolism , Islets of Langerhans/metabolism , Receptors, Pituitary Hormone/metabolism , Type C Phospholipases/metabolism , Animals , Cyclic AMP/biosynthesis , In Vitro Techniques , Islets of Langerhans/enzymology , Male , Mice , Neuropeptides/pharmacology , Pituitary Adenylate Cyclase-Activating Polypeptide , RNA, Messenger/biosynthesis , Rats , Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide , Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide , Receptors, Pituitary Hormone/biosynthesis , Receptors, Vasoactive Intestinal Peptide/biosynthesis , Receptors, Vasoactive Intestinal Peptide/metabolism , Receptors, Vasoactive Intestinal Peptide, Type II , Receptors, Vasoactive Intestinal Polypeptide, Type I , Signal Transduction/physiology , Vasoactive Intestinal Peptide/pharmacology
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