A novel type of macrothrombocytopenia associated with a defect in α2,3-sialylation.

We describe a novel type of human thrombocytopenia characterized by the appearance of giant platelets and variable neutropenia. Searching for the molecular defect, we found that neutrophils had strongly reduced sialyl-Lewis X and increased Lewis X surface expression, pointing to a deficiency in sialylation. We show that the glycosylation defect is restricted to α2,3-sialylation and can be detected in platelets, neutrophils, and monocytes. Platelets exhibited a distorted structure of the open canalicular system, indicating defective platelet generation. Importantly, patient platelets, but not normal platelets, bound to the asialoglycoprotein receptor (ASGP-R), a liver cell-surface protein that removes desialylated thrombocytes from the circulation in mice. Taken together, this is the first type of human thrombocytopenia in which a specific defect of α2,3-sialylation and an induction of platelet binding to the liver ASGP-R could be detected.

Novel ALG8 mutations expand the clinical spectrum of congenital disorder of glycosylation type Ih.

Congenital disorders of glycosylation (CDG) are an expanding group of inherited disorders caused by defects in the N- or O-Glycosylation of proteins and lipids. Several CDG subtypes have been described so far, including CDG type Ih which is caused by a deficiency of the dolichyl-P-Glc:Glc(1)Man(9)GlcNAc(2)-PP-dolichyl alpha1,3-glucosyltransferase (hALG8). The defect leads to an accumulation of Dol-PP-GlcNAc(2)Man(9) and Dol-PP-GlcNAc(2)Man(9)Glc(1) in the endoplasmic reticulum of patients' fibroblasts that can be detected by analyzing the lipid-linked oligosaccharyl intermediates. Five patients with CDG-Ih have been described so far. The clinical presentation of four of these patients was severe with death in early infancy. In this report, we describe two mildly affected siblings with CDG-Ih caused by two novel mutations. While one mutation (c.1434delC) causes a frame shift resulting in a premature termination codon (p.485X), the point mutation of the other allele (c.845C>T, p.A282V) causes an amino acid replacement in a highly conserved region of the hALG8 gene. The two siblings show similar symptoms, including pseudo-gynecomastia, epicanthus, muscular hypotonia, mental retardation and ataxia, expanding the genetic and clinical spectrum of CDG-Ih.

Microdiesel: Escherichia coli engineered for fuel production.

Biodiesel is an alternative energy source and a substitute for petroleum-based diesel fuel. It is produced from renewable biomass by transesterification of triacylglycerols from plant oils, yielding monoalkyl esters of long-chain fatty acids with short-chain alcohols such as fatty acid methyl esters and fatty acid ethyl esters (FAEEs). Despite numerous environmental benefits, a broader use of biodiesel is hampered by the extensive acreage required for sufficient production of oilseed crops. Therefore, processes are urgently needed to enable biodiesel production from more readily available bulk plant materials like sugars or cellulose. Toward this goal, the authors established biosynthesis of biodiesel-adequate FAEEs, referred to as Microdiesel, in metabolically engineered Escherichia coli. This was achieved by heterologous expression in E. coli of the Zymomonas mobilis pyruvate decarboxylase and alcohol dehydrogenase and the unspecific acyltransferase from Acinetobacter baylyi strain ADP1. By this approach, ethanol formation was combined with subsequent esterification of the ethanol with the acyl moieties of coenzyme A thioesters of fatty acids if the cells were cultivated under aerobic conditions in the presence of glucose and oleic acid. Ethyl oleate was the major constituent of these FAEEs, with minor amounts of ethyl palmitate and ethyl palmitoleate. FAEE concentrations of 1.28 g l(-1) and a FAEE content of the cells of 26 % of the cellular dry mass were achieved by fed-batch fermentation using renewable carbon sources. This novel approach might pave the way for industrial production of biodiesel equivalents from renewable resources by employing engineered micro-organisms, enabling a broader use of biodiesel-like fuels in the future.