Biomedical subjects

Elena M Comelli

Publications and source records attributed to Elena M Comelli.

6 recordsLinked to original sources

PubMed2006

Activation of murine CD4+ and CD8+ T lymphocytes leads to dramatic remodeling of N-linked glycans.

Differentiation and activation of lymphocytes are documented to result in changes in glycosylation associated with biologically important consequences. In this report, we have systematically examined global changes in N-linked glycosylation following activation of murine CD4 T cells, CD8 T cells, and B cells by MALDI-TOF mass spectrometry profiling, and investigated the molecular basis for those changes by assessing alterations in the expression of glycan transferase genes. Surprisingly, the major change observed in activated CD4 and CD8 T cells was a dramatic reduction of sialylated biantennary N-glycans carrying the terminal NeuGcalpha2-6Gal sequence, and a corresponding increase in glycans carrying the Galalpha1-3Gal sequence. This change was accounted for by a decrease in the expression of the sialyltransferase ST6Gal I, and an increase in the expression of the galactosyltransferase, alpha1-3GalT. Conversely, in B cells no change in terminal sialylation of N-linked glycans was evident, and the expression of the same two glycosyltransferases was increased and decreased, respectively. The results have implications for differential recognition of activated and unactivated T cells by dendritic cells and B cells expressing glycan-binding proteins that recognize terminal sequences of N-linked glycans.

Animals↗

PubMed2005

A focused microarray approach to functional glycomics: transcriptional regulation of the glycome.

Glycosylation is the most common posttranslational modification of proteins, yet genes relevant to the synthesis of glycan structures and function are incompletely represented and poorly annotated on the commercially available arrays. To fill the need for expression analysis of such genes, we employed the Affymetrix technology to develop a focused and highly annotated glycogene-chip representing human and murine glycogenes, including glycosyltransferases, nucleotide sugar transporters, glycosidases, proteoglycans, and glycan-binding proteins. In this report, the array has been used to generate glycogene-expression profiles of nine murine tissues. Global analysis with a hierarchical clustering algorithm reveals that expression profiles in immune tissues (thymus [THY], spleen [SPL], lymph node, and bone marrow [BM]) are more closely related, relative to those of nonimmune tissues (kidney [KID], liver [LIV], brain [BRN], and testes [TES]). Of the biosynthetic enzymes, those responsible for synthesis of the core regions of N- and O-linked oligosaccharides are ubiquitously expressed, whereas glycosyltransferases that elaborate terminal structures are expressed in a highly tissue-specific manner, accounting for tissue and ultimately cell-type-specific glycosylation. Comparison of gene expression profiles with matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) profiling of N-linked oligosaccharides suggested that the alpha1-3 fucosyltransferase 9, Fut9, is the enzyme responsible for terminal fucosylation in KID and BRN, a finding validated by analysis of Fut9 knockout mice. Two families of glycan-binding proteins, C-type lectins and Siglecs, are predominately expressed in the immune tissues, consistent with their emerging functions in both innate and acquired immunity. The glycogene chip reported in this study is available to the scientific community through the Consortium for Functional Glycomics (CFG) (http://www.functionalglycomics.org).

Animals↗

PubMed2005

Neonatal antibiotic treatment alters gastrointestinal tract developmental gene expression and intestinal barrier transcriptome.

The postnatal maturation of the gut, partially modulated by bacterial colonization, ends up in the establishment of an efficient barrier to luminal antigens and bacteria. The use of broad-spectrum antibiotics in pediatric practices alters the gut bacterial colonization and, consequently, may impair the maturation of the gut barrier function. To test this hypothesis, suckling Sprague-Dawley rats received a daily intragastric gavage of antibiotic (Clamoxyl; an amoxicillin-based commercial preparation) or saline solution from postnatal day 7 (d7) until d17 or d21. Luminal microbiota composition and global gene expression profile were analyzed on samples from small intestine and colon of each group. The treatment with Clamoxyl resulted in the almost-complete eradication of Lactobacillus in the whole intestine and in a drastic reduction of colonic total aerobic and anaerobic bacteria, in particular Enterobacteriacae and Enterococcus. The global gene expression analysis revealed that Clamoxyl affects the maturation process of 249 and 149 Affymetrix probe sets in the proximal and distal small intestine, respectively, and 163 probe sets in the colon. The expression of genes coding for Paneth cell products (defensins, matrilysin, and phospholipase A2) was significantly downregulated by the Clamoxyl treatment. A significant downregulation of major histocompatibility complex (MHC) class Ib and II genes, involved in antigen presentation, was also observed. Conversely, mast cell proteases expression was upregulated. These results suggest that early treatment with a large-spectrum antibiotic deeply affects the gut barrier function at the suckling-weaning interface, a period during which the gut is challenged by an array of novel food-borne antigens.

Aging↗

PubMed2004

Peanut agglutinin high phenotype of activated CD8+ T cells results from de novo synthesis of CD45 glycans.

Following activation in the periphery, murine CD8+ T cells exhibit a characteristic increased binding of peanut agglutinin (PNA), reflecting an increased expression of hyposialylated O-linked glycans (Galbeta1-3GalNAcalpha-O-Thr/Ser) on the cell surface. In this report, we show that the majority of the PNA receptors expressed on activated CD8+ T cells are carried by CD45. Other glycoproteins (e.g. CD8) and the glycolipid asialo-GM1 also carry PNA receptors, although to a much lesser extent. Analysis of enzymes involved in the sialylation/de-sialylation pathways showed that generation of PNA receptors in activated CD8+ T cells is not due to up-regulation of endogenous sialidases. Instead, our results indicate that the PNA(high) phenotype results from de novo synthesis of CD45 carrying reduced sialylated core 1 O-glycans.

Animals↗

PubMed2003

Identification and expression of Neu4, a novel murine sialidase.

A partial murine gene homologous to known mammalian sialidases reported in the Celera database is shown to encode a novel neuraminidase, designated as murine neuraminidase 4 (Neu4). The complete gene contains four exons and an open reading frame of 501 amino acids. It shows significant homology to the previously cloned neuraminidases with characteristic conserved motifs ascribed to the neuraminidase active site. Of the other known murine sialidases, it is most similar to Neu3 (42%). A cDNA encoding the entire coding sequence was isolated from mouse brain and expressed as a recombinant protein in COS-7 cells. Cell lysates contained significantly increased sialidase activity over mock transfected cells, demonstrating that Neu4 is a bona fide neuraminidase.

Amino Acid Sequence↗

PubMed2002

Custom microarray for glycobiologists: considerations for glycosyltransferase gene expression profiling.

The development of microarray technology offers the unprecedented possibility of studying the expression of thousands of genes in one experiment. Its exploitation in the glycobiology field will eventually allow the parallel investigation of the expression of many glycosyltransferases, which will ultimately lead to an understanding of the regulation of glycoconjugate synthesis. While numerous gene arrays are available on the market, e.g. the Affymetrix GeneChip arrays, glycosyltransferases are not adequately represented, which makes comprehensive surveys of their gene expression difficult. This chapter describes the main issues related to the establishment of a custom glycogenes array.

DNA Probes↗