Biomedical subjects

Franco Cotelli

Publications and source records attributed to Franco Cotelli.

8 recordsLinked to original sources

PubMed2006

Bone morphogenic protein antagonist Drm/gremlin is a novel proangiogenic factor.

Angiogenesis plays a key role in various physiologic and pathologic conditions, including tumor growth. Drm/gremlin, a member the Dan family of bone morphogenic protein (BMP) antagonists, is commonly thought to affect different processes during growth, differentiation, and development by heterodimerizing various BMPs. Here, we identify Drm/gremlin as a novel proangiogenic factor expressed by endothelium. Indeed, Drm/gremlin was purified to homogeneity from the conditioned medium of transformed endothelial cells using an endothelial-cell sprouting assay to follow protein isolation. Accordingly, recombinant Drm/gremlin stimulates endothelial-cell migration and invasion in fibrin and collagen gels, binds with high affinity to various endothelial cell types, and triggers tyrosine phosphorylation of intracellular signaling proteins. Also, Drm/gremlin induces neovascularization in the chick embryo chorioallantoic membrane. BMP4 does not affect Drm/gremlin interaction with endothelium, and both molecules exert a proangiogenic activity in vitro and in vivo when administered alone or in combination. Finally, Drm/gremlin is produced by the stroma of human tumor xenografts in nude mice, and it is highly expressed in endothelial cells of human lung tumor vasculature when compared with non-neoplastic lung. Our observations point to a novel, previously unrecognized capacity of Drm/gremlin to interact directly with target endothelial cells and to modulate angiogenesis.

Amino Acid Sequence↗

PubMed2006

Differential regulation of the zebrafish orthopedia 1 gene during fate determination of diencephalic neurons.

BACKGROUND: The homeodomain transcription factor Orthopedia (Otp) is essential in restricting the fate of multiple classes of secreting neurons in the neuroendocrine hypothalamus of vertebrates. However, there is little information on the intercellular factors that regulate Otp expression during development. RESULTS: Here, we identified two otp orthologues in zebrafish (otp1 and otp2) and explored otp1 in the context of the morphogenetic pathways that specify neuroectodermal regions. During forebrain development, otp1 is expressed in anterior groups of diencephalic cells, positioned in the preoptic area (PO) (anterior alar plate) and the posterior tuberculum (PT) (posterior basal plate). The latter structure is characterized by Tyrosine Hydroxylase (TH)-positive cells, suggesting a role for otp1 in the lineage restriction of catecholaminergic (CA) neurons. Disruptions of Hedgehog (HH) and Fibroblast Growth Factor (FGF) pathways point to the ability of SHH protein to trigger otp1 expression in PO presumptive neuroblasts, with the attenuating effect of Dzip1 and FGF8. In addition, our data disclose otp1 as a determinant of CA neurons in the PT, where otp1 activity is strictly dependent on Nodal signaling and it is not responsive to SHH and FGF. CONCLUSION: In this study, we pinpoint the evolutionary importance of otp1 transcription factor in cell states of the diencephalon anlage and early neuronal progenitors. Furthermore, our data indicate that morphogenetic mechanisms differentially regulate otp1 expression in alar and basal plates.

Amino Acid Sequence↗

PubMed2006

Comparative genome analysis of the neurexin gene family in Danio rerio: insights into their functions and evolution.

Neurexins constitute a family of proteins originally identified as synaptic transmembrane receptors for a spider venom toxin. In mammals, the 3 known Neurexin genes present 2 alternative promoters that drive the synthesis of a long (alpha) and a short (beta) form and contain different sites of alternative splicing (AS) that can give rise to thousands of different transcripts. To date, very little is known about the significance of this variability, except for the modulation of binding to some of the Neurexin ligands. Although orthologs of Neurexins have been isolated in invertebrates, these genes have been studied mostly in mammals. With the aim of investigating their functions in lower vertebrates, we chose Danio rerio as a model because of its increasing importance in comparative biology. We have isolated 6 zebrafish homologous genes, which are highly conserved at the structural level and display a similar regulation of AS, despite about 450 Myr separating the human and zebrafish species. Our data indicate a strong selective pressure at the exonic level and on the intronic borders, in particular on the regulative intronic sequences that flank the exons subject to AS. Such a selective pressure could help conserve the regulation and consequently the function of these genes along the vertebrates evolutive tree. AS analysis during development shows that all genes are expressed and finely regulated since the earliest stages of development, but mark an increase after the 24-h stage that corresponds to the beginning of synaptogenesis. Moreover, we found that specific isoforms of a zebrafish Neurexin gene (nrxn1a) are expressed in the adult testis and in the earliest stages of development, before the beginning of zygotic transcription, indicating a potential delivery of paternal RNA to the embryo. Our analysis suggests the existence of possible new functions for Neurexins, serving as the basis for novel approaches to the functional studies of this complex neuronal protein family and more in general to the understanding of the AS mechanism in low vertebrates.

Alternative Splicing↗

PubMed2005

Antiangiogenic and vascular-targeting activity of the microtubule-destabilizing trans-resveratrol derivative 3,5,4'-trimethoxystilbene.

Neovascularization plays an important role in neoplasia and angioproliferative diseases. Two major modalities have been developed so far to affect neovascularization: its prevention by antiangiogenic compounds, and immature vessel disruption by vascular-targeting agents. trans-Resveratrol, found in grapes and wine, exerts antioxidant, antineoplastic, and antiangiogenic activities. Here, among various synthetic trans-resveratrol derivatives tested, 3,5,4'-trimethoxystilbene was an antiangiogenic agent 30 to 100 times more potent than parent compound in inhibiting endothelial cell proliferation, sprouting, collagen gel invasion, and morphogenesis (ID50 = 0.3-3.0 microM). In addition, 3,5,4'-trimethoxystilbene acts as a vascular-targeting agent by causing microtubule disassembling and tubulin depolymerization and by impairing the repositioning of the microtubule organization center and the formation of membrane ruffles in migrating endothelial cells. In keeping with a vascular-targeting ability, 3,5,4'-trimethoxystilbene induced apoptosis only in subconfluent endothelial cells and apoptotic regression of immature vessels in the ex vivo rat aorta ring assay. In vivo, 3,5,4'-trimethoxystilbene caused the rapid stasis of blood flow and regression of intersegmental vessels in the trunk of zebrafish embryos. In addition, it inhibited blood vessel growth and caused the disappearance of pre-existing blood vessels in the area vasculosa of the chick embryo. In conclusion, 3,5,4'-trimethoxystilbene associates an antiangiogenic profile to a significant vascular-targeting activity.

Angiogenesis Inhibitors↗

PubMed2004

Regulated expression pattern of gremlin during zebrafish development.

Xenopus laevis Gremlin has been isolated as a novel dorsalizing factor, belonging to a family of secreted proteins with axial patterning activity . In a search for genes that control development in zebrafish (Danio rerio), we have identified a sequence homologous to Xenopus gremlin. This paper describes the cloning of zebrafish gremlin (grm) and its expression pattern during development. Our results show that grm encodes a maternal transcript, and the zygotic transcription is turned on at the mid-blastula transition (MBT), when grm is detected in the entire blastoderm. In the gastrula grm becomes restricted to the dorsolateral region of the embryo, and during somitogenesis it is strongly expressed in the presomitic mesoderm and developing somites, and in the ventral neural tube. From 24 hpf to 48 hpf, we show that grm transcription is downregulated in the whole embryo, even though Grm protein is still present and localized into the entire myotome at 48-72 hpf. Finally, grm transcript is strongly downregulated in fibroblast growth factor-8 (fgf8) and sonic hedgehog (shh) mutants, thus implicating a putative role of Fgf/Shh signalling loop in grm expression regulation.

Amino Acid Sequence↗

PubMed2004

Functional and hierarchical interactions among zebrafish vox/vent homeobox genes.

The vertebrate Vox/Vent family of transcription factors plays a crucial role in the establishment of the dorsoventral (DV) axis, by repressing organizer genes such as bozozok/dharma, goosecoid, and chordino. In Danio rerio (zebrafish), members of the vox/vent gene family (vox/vega1, vent/vega2, and ved) are thought to share expression patterns and functional properties. Bringing novel insights in the differential activity of the zebrafish vox/vent genes, we propose a critical role for the ved gene in DV patterning of vertebrate embryos. ved is not only expressed as a maternal gene, but it also appears to function as a repressor of dorsal factors involved in organizer formation. At early- and mid-gastrula stage, ved appears to be finely controlled by antagonist crosstalks in a complex regulatory network, involving gradients of bone morphogenetic protein (BMP) activity, dorsal factors, and vox/vent family members. We show that ved transcripts are ventrally restricted by BMP factors such as bmp2b, bmp7, smad5, and alk8, and by dorsal factors (chd and gsc). Alteration of ved expression in both vox and vent deletion mutants and vox and vent mRNAs-injected embryos, suggests that vox and vent function downstream of BMP signaling to negatively regulate ved expression. This inhibitory role is emphasized by a vox and vent redundant activity, compared with single gene effects.

Amino Acid Sequence↗

PubMed2004

Ectopic expression and knockdown of a zebrafish sox21 reveal its role as a transcriptional repressor in early development.

Sox proteins are DNA-binding proteins belonging to the HMG box superfamily and they play key roles in animal embryonic development. Zebrafish Sox21a is part of group B Sox proteins and its chicken and mouse orthologs have been described as transcriptional repressor and activator, respectively, in two different target gene contexts. Zebrafish sox21a is present as a maternal transcript in the oocyte and is mainly expressed at the developing midbrain-hindbrain boundary from the onset of neurulation. In order to understand its role in vivo, we ectopically expressed sox21a by microinjection. Ectopic expression of full length sox21a leads to dorsalization of the embryos. A subset of the dorsalized embryos shows a partial axis splitting, and hence an ectopic neural tube, as an additional phenotype. At gastrulation, injected embryos show expansion of the expression domains of organizer-specific genes, such as chordin and goosecoid. Molecular markers used in somitogenesis highlight that sox21a-injected embryos have shortened AP axis, undulating axial structures, enlarged or even radialized paraxial territory. The developmental abnormalities caused by ectopic expression of sox21a are suggestive of defects in convergence-extension morphogenetic movements. Antisense morpholino oligonucleotides, designed to functionally knockdown sox21a, cause ventralization of the embryos. Moreover, gain-of-function experiments with chimeric constructs, where Sox21a DNA-binding domain is fused to a transcriptional activator (VP16) or repressor (EnR) domain, suggests that zebrafish Sox21a acts as a repressor in dorso-ventral patterning.

Animals↗

PubMed2004

Identification and expression pattern of mago nashi during zebrafish development.

In a search for zebrafish genes expressed during early stages of development, we have identified two ESTs encoding proteins related to Drosophila mago nashi. Zebrafish mago nashi codes for a small protein with no clearly identified functional domains, and which is highly conserved during evolution. This paper describes the identification and a detailed gene expression analysis of zebrafish mago nashi during development. Our results demonstrate that mago nashi encodes a maternal transcript detected in both blastomeres and yolk cell at the 1-2 cell stages, and in the blastoderm during segmentation. We show that a putative microtubule-mediated transport of mago nashi mRNA from the vegetal hemisphere into animal blastomeres determines the localization of the transcript in the animal pole, immediately after fertilization. Furthermore, the microtubule array contained into the yolk cell seems to be responsible for the high level of mago nashi transcript detected in the central blastomeres at the 8-16 cell stages. Zygotic mago nashi is expressed into the dorsal-marginal region during gastrulation, and starting from somitogenesis to 24 hpf, the expression domain becomes progressively restricted to the developing neural tube and paraxial structures, and ventrally to the pronephric ducts.

Amino Acid Sequence↗