DNA AND CELL BIOLOGY Volume 25, Number 8, 2006 © Mary Ann Liebert, Inc. Pp. 465–474 Murine Ortholog of the Novel Glycosyltransferase, B3GTL: Primary Structure, Characterization of the Gene and Transcripts, and Expression in Tissues TAISTO Y.K. HEINONEN, 1 MARKKU PELTO-HUIKKO, 2 LEENA PASTERNACK, 1 MARKKU MÄKI, 1 and HEIKKI KAINULAINEN 3 ABSTRACT Glycosylation of proteins and lipids is important in cellular communication and maintenance of tissues. B3GTL (3-glycosyltransferase-like) is a novel glycosyltransferase that is found in multicellular animals ranging from mammals to insects and nematodes. The aim of this work was to identify and characterize the B3GTL gene in the mouse and to study its expression in various tissues. The murine gene codes for a protein which shares 84% amino acid sequence identity with its human ortholog, and contains all the primary structural features that characterize B3GTL proteins. The murine and human B3GTL genes share an identical exon/intron or- ganization, and both genes utilize multiple polyadenylation signals. Their promoter regions show extensive conservation, implying that the two genes also share regulatory similarities. This notion was reinforced by Northern hybridization analysis of mouse tissues, which showed the tissue distribution of B3GTL mRNA to be similar to that previously found in human tissues, with the heart, kidney, and brain being major sites of expression in both species. The localization of B3GTL mRNA was studied by in situ hybridization in an ex- tensive collection of mouse tissues, of which the granular cells of the olfactory bulb and the epithelium of the seminal vesicle displayed particularly strong signals. Together, these analyses indicate that the B3GTL mRNA is subject to strong tissue-specific and developmental regulation. The findings reported here make possible the design of a B3GTL “knock-out” mouse, provide a framework for analyzing the regulation of the gene, and provide an extensive catalog of tissues in which this novel protein acts. 465 INTRODUCTION G LYCOSYLATION IS A COMMON MODIFICATION that effects the structure and biological properties of many cell surface proteins and lipids, thereby modulating cellular recognition, ad- hesion, migration, and signaling (Hakomori, 2002; Haltiwanger and Lowe, 2004). The various oligosaccharide side chains, called glycans, show enormous structural diversity, and have a vast capacity for information storage, forming the basis of a “sugar code” that directs cellular communication in tissues (Gabius et al., 2004). An integral part of the deciphering mech- anism of the code is provided by endogenous lectins, proteins that recognize and bind specific carbohydrate structures. Each individual glycan is built up sequentially from mono- saccharide units by the coordinated action of a number of gly- cosyltransferases, enzymes that function primarily in the endo- plasmic reticulum or the Golgi apparatus (Breton et al., 2001; Hu and Walker, 2002). More than 230 glycosyltransferase ac- tivities or potential enzyme sequences have already been iso- lated from human cells (Coutinho and Henrissat, 1999), but the full set of enzymes responsible for the biosynthesis of the hu- man “glycome” remains to be identified. Glycan expression is subject to tissue-specific as well as de- velopmental regulation, each cell and tissue expressing a char- acteristic set of glycan structures. This set is synthesized by the repertoire of glycosyltransferases active in that cell or tissue, 1 Paediatric Research Centre, University of Tampere Medical School and Tampere University Hospital, Tampere, Finland. 2 Department of Developmental Biology, University of Tampere Medical School, and Department of Pathology, Tampere University Hospi- tal, Tampere, Finland. 3 Institute of Medical Technology, University of Tampere, Tampere, Finland, and Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.