GGA1 acts as a spatial switch altering amyloid precursor protein trafficking and processing

The beta-amyloid (Abeta) precursor protein (APP) is cleaved sequentially by beta-site of APP-cleaving enzyme (BACE) and gamma-secretase to release the Abeta peptides that accumulate in plaques in Alzheimer's disease (AD). GGA1, a member of the Golgi-localized gamma-ear-containing ARF-binding (GGA) protein family, interacts with BACE and influences its subcellular distribution. We now report that overexpression of GGA1 in cells increased the APP C-terminal fragment resulting from beta-cleavage but surprisingly reduced Abeta. GGA1 confined APP to the Golgi, in which fluorescence resonance energy transfer analyses suggest that the proteins come into close proximity. GGA1 blunted only APP but not notch intracellular domain release. These results suggest that GGA1 prevented APP beta-cleavage products from becoming substrates for gamma-secretase. Direct binding of GGA1 to BACE was not required for these effects, but the integrity of the GAT (GGA1 and TOM) domain of GGA1 was. GGA1 may act as a specific spatial switch influencing APP trafficking and processing, so that APP-GGA1 interactions may have pathophysiological relevance in AD.     

Identification and characterization of novel uroporphyrinogen decarboxylase gene mutations in a large series of porphyria cutanea tarda patients and relatives

Porphyria cutanea tarda (PCT) arises from decreased hepatic activity of uroporphyrinogen decarboxylase (UROD). Both genetic and environmental factors interplay in the precipitation of clinically overt PCT, but these factors may vary between different geographic areas. Decreased activity of UROD in erythrocytes was used to identify patients with UROD mutations among a group of 130 Spanish PCT patients. Nineteen patients (14.6%) were found to harbor a mutation in the UROD gene. Eight mutations were novel: M1I, 5del10, A22V, D79N, F84I, Q116X, T141I and Y182C. Five others were previously described: F46L, V134Q, R142Q, P150L and E218G. The new missense mutations and P150L were expressed in Escherichia coli. D79N and P150L resulted in proteins that were localized to inclusion bodies. The other mutations produced recombinant proteins that were purified and showed reduced activity (range: 2.3–73.2% of wild type). These single amino acid changes were predicted to produce complex structural alterations and/or reduced stability of the enzyme. Screening of relatives of the probands showed that 37.5% of mutation carriers demonstrated increased urinary porphyrins. This study emphasizes the role of UROD mutations as a strong risk factor for PCT even in areas where environmental factors (hepatitis C virus) have been shown to be highly associated with the disease.     

Epogam evening primrose oil treatment in atopic dermatitis and asthma

Essential fatty acids are claimed to have positive effects in atopic diseases. In a double blind, placebo controlled, parallel group study 58 out of 60 children, with atopic dermatitis and the need for regular treatment with topical skin steroids, completed a 16 weeks' treatment period with either Epogam evening primrose oil or placebo capsules. Twenty two of these subjects also had asthma. The parents used diaries to record symptom scores and concomitant medication. Peak expiratory flow was measured and disease activity was monitored by the clinician every four weeks. The plasma concentrations of essential fatty acids increased significantly in the group treated with Epogam capsules. The study demonstrated significant improvements of the eczema symptoms but no significant difference was found between the placebo and the Epogam groups. No therapeutic effect was shown on asthma symptoms or fidget.     

Pericardial effusion complicating a percutaneous central venous line in a neonate

A premature infant developed pericardial effusion four days after the insertion of a 25-gauge silastic percutaneous central venous catheter. The effusion contained parenteral nutrition fluid and resolved rapidly after withdrawal of the catheter. Pericardial effusion is a potential complication of percutaneous, as well as surgically placed, central venous catheters.     

The STR system in the human phenylalanine hydroxylase gene: true fragment length obtained with fluorescent labelled PCR primers

We present a simple, fast, non-radioactive method for the analysis of the polymorphic short tandem repeat (STR) system in the human phenylalanine hydroxylase gene. Previously, sizing of the STR marker involved radiolabelling of PCR amplified fragments and resolution on denaturing polyacrylamide gels using M13 sequencing ladder as a standard. However, this method consistently gave sizes 2 bp longer than the known sequence. The fluorescent method presented here employs internal lane standards and enables accurate sizing of the fragments. To avoid confusion, we suggest that the true fragment lengths are used as reference values in the future. The analysis of STR alleles is valuable for population genetic studies and for targeted mutation screening in phenylketonuria (PKU). It can replace RFLP-based haplotype analysis for carrier detection, and we report its use for prenatal diagnosis in a Northern Irish family with PKU. The analysis of 250 Northern Irish chromosomes, including 128 PKU alleles, showed no significant difference between normal and PKU alleles, with fragment lengths of 238 and 242 bp most common in both groups.     

Molecular analysis of PKU in Ireland

Classical phenylketonuria (PKU: McKusick No. 261600) is caused by mutations occurring at the phenylalanine hydroxylase (PAH) locus on chromosome 12 and has a prevalence in Ireland of 1 in 4500. We examined 304 independent alleles from 350 patients for the presence of six mutations and have characterized VNTR alleles within the minisatellite region 3' to the PAH gene in patients carrying the most prevalent mutation. R408W was the most common mutation found, with a relative frequency of 42%. All other mutations had relative frequencies of <10%. VNTR analysis showed that the R408W mutation is associated with the VNTR-8 allele in the Irish population, indicating that R408W is associated with RFLP haplotype 1. This differs from that reported from eastern Europe where R408W is associated with RFLP haplotype 2/VNTR-3; an observation which has led several groups to propose a Balto-Slavic origin for this mutation. These results support the hypothesis of a second, independent founding event for the R408W mutation on an RFLP haplotype 1 VNTR-8 chromsome background in the Irish/Celtic population.     

Fructosamine and glycated haemoglobin in the assessment of long term glycaemic control in diabetes

Fructosamine and glycated haemoglobin were measured simultaneously in 147 children with diabetes. If glycated haemoglobin is considered as the 'gold standard' for long term glycaemic control, then fructosamine is a poor indicator of actual glycated haemoglobin values, with wide 95% confidence (fiducial) limits. This shows that it is impossible to accurately predict glycated haemoglobin concentrations and therefore, by implication, longer term glycaemic control, from measurements of fructosamine. As the major studies on the prevention of microvascular complications in diabetes have used glycated haemoglobin levels to assess glycaemic control, it is suggested that this measurement should be used in all children with diabetes in preference to the measurement of fructosamine.