Molecular evolution of olfactomedin

Olfactomedin is a secreted polymeric glycoprotein of unknown function,originally discovered at the mucociliary surface of the amphibian olfactoryneuroepithelium and subsequently found throughout the mammalian brain. As afirst step toward elucidating the function of olfactomedin, itsphylogenetic history was examined to identify conserved structural motifs.Such conserved motifs may have functional significance and provide targetsfor future mutagenesis studies aimed at establishing the function of thisprotein. Previous studies revealed 33% amino acid sequence identity betweenrat and frog olfactomedins in their carboxyl terminal segments. Furtheranalysis, however, reveals more extensive homologies throughout themolecule. Despite significant sequence divergence, cysteines essential forhomopolymer formation such as the CXC motif near the amino terminus areconserved, as is the characteristic glycosylation pattern, suggesting thatthese posttranslational modifications are essential for function.Furthermore, evolutionary analysis of a region of 53 amino acids of fish,frog, rat, mouse, and human olfactomedins indicates that an ancestralolfactomedin gene arose before the evolution of terrestrial vertebrates andevolved independently in teleost, amphibian, and mammalian lineages.Indeed, a distant olfactomedin homolog was identified in Caenorhabditiselegans. Although the amino acid sequence of this invertebrate protein islonger and highly divergent compared with its vertebrate homologs, theprotein from C. elegans shows remarkable similarities in terms of conservedmotifs and posttranslational modification sites. Six universally conservedmotifs were identified, and five of these are clustered in the carboxylterminal half of the protein. Sequence comparisons indicate that evolutionof the N-terminal half of the molecule involved extensive insertions anddeletions; the C-terminal segment evolved mostly through point mutations,at least during vertebrate evolution. The widespread occurrence ofolfactomedin among vertebrates and invertebrates underscores the notionthat this protein has a function of universal importance. Furthermore,extensive modification of its N-terminal half and the acquisition of aC-terminal SDEL endoplasmic-reticulum- targeting sequence may have enabledolfactomedin to adopt new functions in the mammalian central nervoussystem.     

Identification of a novel UDP-Glc:GlcNAc beta1-->4-glucosyltransferase in Lymnaea stagnalis that may be involved in the synthesis of complex-type oligosaccharide chains

Several studies suggest, that the snail Lymnaea stagnalis contains glycoproteins whose oligosaccharide side chains have structural features not commonly found in mammalian glycoproteins. In this study, prostate glands of L. stagnalis were incubated in media containing either [(3)H]-mannose, [(3)H]-glucosamine, or [(3)H]-galactose, and the metabolically radiolabeled protein-bound oligosaccharides were analyzed. The newly synthesized diantennary-like complex-type asparagine-linked chains contained a considerable amount of glucose, next to mannose, GlcNAc, fucose, galactose, and traces of GalNAc. Since glucose has not been found before as a constituent of diantennary N-linked glycans as far as we know, we assayed the prostate gland of L. stagnalis for a potential glucosyltransferase activity involved in the biosynthesis of such structures. We report here, that the prostate gland of L. stagnalis contains a beta1-->4-glucosyltransferase activity that transfers glucose from UDP-glucose to acceptor substrates carrying a terminal N-acetylglucosamine. The enzyme prefers substrates carrying a terminal GlcNAc that is beta6 linked to a Gal or a GalNAc, structures occurring in O-linked glycans, or a GlcNAc that is beta2 linked to mannose, as is present in N-linked glycans. Based on combined structural and enzymatic data, we propose that the novel beta1-->4-gluco-syltransferase present in the prostate gland may be involved in the biosynthesis of Glcbeta1-->4GlcNAc units in complex-type glycans, in particular in N-linked diantennary glycans.     

A major difference between the divergence patterns within the lines-1 families in mice and voles

L1 retroposons are represented in mice by subfamilies of interspersed sequences of varied abundance. Previous analyses have indicated that subfamilies are generated by duplicative transposition of a small number of members of the L1 family, the progeny of which then become a major component of the murine L1 population, and are not due to any active processes generating homology within preexisting groups of elements in a particular species. In mice, more than a third of the L1 elements belong to a clade that became active approximately 5 Mya and whose elements are > or = 95% identical. We have collected sequence information from 13 L1 elements isolated from two species of voles (Rodentia: Microtinae: Microtus and Arvicola) and have found that divergence within the vole L1 population is quite different from that in mice, in that there is no abundant subfamily of homologous elements. Individual L1 elements from voles are very divergent from one another and belong to a clade that began a period of elevated duplicative transposition approximately 13 Mya. Sequence analyses of portions of these divergent L1 elements (approximately 250 bp each) gave no evidence for concerted evolution having acted on the vole L1 elements since the split of the two vole lineages approximately 3.5 Mya; that is, the observed interspecific divergence (6.7%-24.7%) is not larger than the intraspecific divergence (7.9%-27.2%), and phylogenetic analyses showed no clustering into Arvicola and Microtus clades.      

Fc specific IgG glycosylation profiling by robust nano-reverse phase HPLC-MS using a sheath-flow ESI sprayer interface

Biological activities of immunoglobulin G such as effector functions via Fc receptor interactions are influenced by Fc-linked N-glycans. Here we describe a fast, robust and sensitive nano-LC-ESI-MS method for detailed subclass specific analysis of IgG Fc N-glycosylation. A sheath-flow ESI sprayer was used as a sensitive zero dead volume plug-and-play interface for online MS coupling, generating a very constant spray and ionization over the entire LC gradient. The propionic acid containing sheath-liquid effectively suppressed TFA gas-phase ion-pairing, enabling the use of TFA containing mobile phases. The fixed position of the sheath-flow ESI sprayer, far away from the glass capillary inlet, reduced MS contamination as compared to conventional nano-ESI. The method was found to be suitable for fast and detailed subclass specific IgG Fc N-glycosylation profiling in human plasma. The obtained subclass specific IgG Fc N-glycosylation profiles were processed automatically using in house developed software tools. For each of the IgG subclasses the 8 major glycoforms showed an interday analytical variation below 5%. The method was used to profile the IgG Fc N-glycosylation of 26 women at several time points during pregnancy and after delivery, revealing pregnancy-associated changes in IgG galactosylation, sialylation and incidence of bisecting N-acetylglucosamine.     

心脏特异表达LMNA^E82K转基因小鼠的建立

目的建立心脏特异表达LMNAE82K转基因小鼠,为研究LMNAE82K与心肌病发病机制的关系提供工具动物。方法把LMNAE82K基因插入α-MHC启动子下游,构建转基因表达载体,显微注射法建立C57BL/6JLMNAE82K转基因小鼠,PCR鉴定转基因小鼠的基因型,采用Western Blot鉴定LMNAE82K在心脏组织中的表达,H＆E染色和超声检测转基因小鼠心脏的病理改变。结果建立了2个心脏组织特异表达LMNAE82K的转基因小鼠品系。超声检查显示转基因小鼠心室壁变薄,收缩期容积和舒张期容积增加,射血分数及短轴缩短率降低。结论LMNAE82K转基因小鼠具有LMNAE82K引起的家族性扩心病有类似的病理变化,为研究LMNAE82K与心肌病发病机制的关系的研究提供了有价值的疾病动物模型。