Biomedical subjects

Tiziana Giordano

Publications and source records attributed to Tiziana Giordano.

5 recordsLinked to original sources

PubMed2006

Monoclonal antibody 76F distinguishes IA-2 from IA-2beta and overlaps an autoantibody epitope.

IA-2 and IA-2beta are highly related proteins that are autoantigens in type 1 diabetes, and provide a model for developing reagents and assays that distinguish similar proteins with unique autoantibody epitopes. Monoclonal antibodies (mAb) to IA-2 and IA-2beta were prepared and tested for their ability to bind to the related proteins and their ability to compete for specific autoantibody epitope binding by sera from patients with type 1 diabetes. Monoclonal antibodies that specifically bound IA-2 (76F) or bound both IA-2 and IA-2beta (A9) were isolated and characterized. 76F mAb recognized IA-2 of human, rat and mouse origin in native and denatured forms and had an epitope specificity for residues 626-630 (FEYQD) which are found in the juxtamembrane (JM) region of human and mouse IA-2, but not IA-2beta. This region overlaps with the autoantibody epitope JM2. Binding to the 76F monoclonal antibody was specifically inhibited by sera with antibodies to the JM2 epitope but not with antibodies to the adjacent JM1 epitope, indicating that unique epitopes can be distinguished by this approach. 76F mAb has the unique property to distinguish between the two closely related autoantigens IA-2 and IA-2beta by targeting an IA-2 specific epitope of the juxtamembrane region. The findings define an approach to develop assays for specific antibody epitope measurements which may be relevant for disease prognosis and monitoring intervention therapies.

Amino Acid Sequence↗

PubMed2005

Bone marrow mesenchymal stem cells express a restricted set of functionally active chemokine receptors capable of promoting migration to pancreatic islets.

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are stromal cells with the ability to proliferate and differentiate into many tissues. Although they represent powerful tools for several therapeutic settings, mechanisms regulating their migration to peripheral tissues are still unknown. Here, we report chemokine receptor expression on human BM-MSCs and their role in mediating migration to tissues. A minority of BM-MSCs (2% to 25%) expressed a restricted set of chemokine receptors (CXC receptor 4 [CXCR4], CX3C receptor 1 [CX3CR1], CXCR6, CC chemokine receptor 1 [CCR1], CCR7) and, accordingly, showed appreciable chemotactic migration in response to the chemokines CXC ligand 12 (CXCL12), CX3CL1, CXCL16, CC chemokine ligand 3 (CCL3), and CCL19. Using human pancreatic islets as an in vitro model of peripheral tissue, we showed that islet supernatants released factors able to attract BM-MSCs in vitro, and this attraction was principally mediated by CX3CL1 and CXCL12. Moreover, cells with features of BM-MSCs were detected within the pancreatic islets of mice injected with green fluorescent protein (GFP)-positive BM. A population of bona fide MSCs that also expressed CXCR4, CXCR6, CCR1, and CCR7 could be isolated from normal adult human pancreas. This study defines the chemokine receptor repertoire of human BM-MSCs that determines their migratory activity. Modulation of homing capacity may be instrumental for harnessing the therapeutic potential of BM-MSCs.

Animals↗

PubMed2004

A new susceptibility locus for migraine with aura in the 15q11-q13 genomic region containing three GABA-A receptor genes.

Migraine is the most common type of chronic episodic headache. Several population-based family studies have suggested a strong genetic predisposition to migraine, especially migraine with aura (MA). Although several susceptibility loci have been identified, none of the numerous studies performed to date have led to the identification of a gene responsible for the more common forms of migraine. GABA-A receptors and their modulator sites seem to be involved in the pathophysiological events that underlie migraine. We report on clinical and molecular data from a total of 10 families with MA, in which MA segregates as an autosomal dominant trait and presents with homogeneous clinical features. After excluding linkage with the known candidate loci, we used a functional candidate approach and genotyped these families with markers from the 15q11-q13 genomic region, which contains the genes encoding GABA-A receptor subunits. Evidence of linkage was obtained with a parametric two-point linkage analysis (maximum LOD score of 5.56 at a recombination fraction of 0.001 for marker GABRB3) and was supported by multipoint analysis (maximum LOD score of 6.54 between markers D15S113 and D15S1019). The critical region spanned 3.6 Mb. These results provide the basis for further investigation of the hypothesized relationship between a GABA-A receptor dysfunction and migraine.

Adolescent↗

PubMed2004

Dense-core granules: a specific hallmark of the neuronal/neurosecretory cell phenotype.

Expression of dense-core granules, a typical exocytic organelle, is widely believed to be controlled by coordinate gene expression mechanisms specific to neurones and neurosecretory cells. Recent studies in PC12 cells, however, have suggested the number of granules/cells depends on the levels of only one of their cargo proteins, chromogranin A, regulating the metabolism of the other proteins, and thus the composition of the organelles, by an on/off switch mechanism. In addition, transfection of chromogranin A was reported to induce appearance of dense-core granules in the non-neurosecretory fibroblasts of the CV-1 line. Here the role of chromogranin A has been reinvestigated using not the heterogeneous PC12 line but several clones isolated therefrom. In these clones, investigated as such or after transfection with chromogranin A antisense sequences, the ratio between chromogranin A and its secretory protein mate, chromogranin B, was not constant but highly and apparently randomly variable. Variability of the chromogranin A/chromogranin B ratio was seen by confocal immunofluorescence also among the cells of single clones and subclones and among the granules of single cells. Moreover, stable and transient transfections of chromogranin A in a PC12 clone characterised by a low number of dense-core granules (one fifth of the reference clone) failed to modify significantly the number of the organelles, despite the several-fold increase of the granin. Finally, in three types of non-neurosecretory cells (CV-1, adenocarcinoma TS/A and a clone of PC12 incompetent for secretion) the transfected chromogranin A accumulated mostly in the Golgi/transGolgi area and was released rapidly from resting cells (constitutive secretion) as revealed by both immunofluorescence during cycloheximide treatment and pulse-chase experiments. Only a minor fraction was sorted to discrete organelles that were not dense-core granules, but primarily lysosomes because they contained no chromogranin B, and were largely positive for the late endosomal-lysosomal markers, lamp1 and lamp3. Dense-core granules are therefore true hallmarks of neurones and neurosecretory cells. Their number/cell appears independent of chromogranin A and their composition does not appear to be constant; in particular, they exhibit considerable, and so far unexplained variability in the chromogranin A/chromogranin B ratio.

Animals↗

PubMed2002

Neurosecretion competence. A comprehensive gene expression program identified in PC12 cells.

The phenotype of neurosecretory cells is characterized by clear vesicles and dense granules, both discharged by regulated exocytosis. However, these organelles are lacking completely in a few neurosecretion-incompetent clones of the pheochromocytoma PC12 line, in which other specific features are maintained (incompetent clones). In view of the heterogeneity of PC12 cells, a differential characterization of the incompetent phenotype based on the comparison of a single incompetent and a single wild-type clone would have been inconclusive. Therefore, we have compared two pairs of PC12 clones, studying in parallel the transcript levels of 4,200 genes and 19,000 express sequence tags (ESTs) by high density oligonucleotide arrays. After accurate data processing for quality control and filtration, a total of 755 transcripts, corresponding to 448 genes and 307 ESTs, was found consistently changed, with 46% up-regulated and 54% down-regulated in incompetent versus wild-type clones. Many but not all neurosecretion genes were profoundly down-regulated in incompetent cells. Expression of endocytosis genes was normal, whereas that of many nuclear and transcription factors, including some previously shown to play key roles in neurogenesis, was profoundly changed. Additional differences appeared in genes involved in signaling and metabolism. Taken together these results demonstrate for the first time that expression of neurosecretory vesicles and granules is part of a complex gene expression program that includes many other features that so far have not been recognized.

Animals↗