Citations

AbstractMany congenital disorders of glycosylation (CDG) can be diagnosed by observing the extent of glycosylation of the abundant serum glycoprotein transferrin (Trf). Trf is an N‐glycosylated protein with two asparagine glycation sites. CDG types I are those genetic defects which occur prior to transfer of the complex oligosaccharide to the acceptor asparagine in the cotranslated polypeptide chain. CDG Ia constitutes by far the most frequent form of CDG and is the result of mutations in the phosphomannomutase gene. CDG Ia and the Ib subtype (Phosphomannoisomerase deficiency) result in low cellular mannose‐1‐phosphate levels, a required precursor for oligosaccharide assembly in the endoplasmic reticulum. The deficiency in oligosaccharides with branched mannose structures is thereafter expressed by the appearance of glycoproteins with unoccupied N‐glycosylation sites (hypoglycosylation). Currently, there have been at least 11 Type I defects, type Ia being by far the most frequently occurring. Most, if not all type I defects result in unoccupied N‐glycation sites. Hypoglycosylated Trf, also known as carbohydrate‐deficient Trf (CDT), can be detected using mass spectrometry (MS) to measure the masses of the serum Trf. The methods for sample preparation using affinity chromatography and MS analysis are described in this unit. Curr. Protoc. Hum. Genet. 54:17.4.1‐17.4.9 © 2007 by John Wiley & Sons, Inc.

Mild cognitive impairment is a topic of great activity from both clinical and research perspectives. It represents a transitional state between the cognitive changes of aging and the earliest clinical manifestations of dementia. We present a case for its inclusion in the Diagnostic and Statistical Manual of Mental Disorders (5th ed; DSM-V) based on clinical, outcome, epidemiological, neuroimaging, and pathophysiological data. The strongest case for inclusion can be made for the amnestic subtype, which is likely a clinical precursor of Alzheimer’s disease. Arguments are presented as to why mild cognitive impairment can be considered as an entity distinct from normal aging and from clinically probable Alzheimer’s disease and why it deserves consideration as a separate construct. In many respects, mild cognitive impairment fulfills criteria for inclusion more adequately than many other conditions currently codified in DSM-IV. Future research directions to help clarify some of the remaining uncertainties are proposed.

SummaryA follow‐up over 7 years on a patient with congenital disorder of glycosylation type Ia showed a significant normalization of hypoglycosylated transferrin. Isoelectric focusing for serum transferrin is a widely used screening method but there could be a limit of detection and the subtle changes can be also overlooked. Re‐test with a different method is desirable, especially when the clinical suspicion for congenital disorder of glycosylation is high.

Abstract Background: Transthyretin-associated hereditary amyloidosis (ATTR) is an inherited disease in which variants in the primary structure of transthyretin (TTR; prealbumin) lead to the extracellular polymerization of insoluble protein fibrils, causing organ failure and ultimately death when major organs are involved. We have developed an integrated approach to molecular diagnosis with initial analysis of intact plasma TTR by electrospray ionization mass spectrometry (MS) and referral of positive samples for DNA sequence analysis and real-time PCR to confirm the common Gly6Ser polymorphism. Methods: Samples from 6 patients previously diagnosed with ATTR and from 25 controls with (n = 15) or without (n = 10) polyneuropathy were analyzed in a blinded fashion for the presence of variant TTR. TTR protein was extracted with an immunoaffinity resin from 20 μL of archived plasma samples. The purified TTR was reduced with tris(2-carboxyethyl)phosphine and analyzed by MS. The appearance of two peaks (or a single peak shifted in mass indicative of a homozygous variant), including the wild-type mass of 13 761 Da, was indicative of the presence of a variant, and the individual was referred for DNA sequence analysis. Results: MS analysis of intact reduced TTR correctly identified each of six samples known to contain variant TTR. These results were corroborated by subsequent DNA sequence analysis. Additionally, all Gly6Ser polymorphisms were correctly called based on the +30 mass shift and an equal relative abundance of the +30 polymorphism relative to wild-type TTR. No false-positive results were seen. Conclusions: This referral method eliminates the necessity of sequencing most samples and allows screening for the familial forms of amyloidosis in a broad patient population in a timely fashion. This method correctly identified all previously known variants and also identified a novel variant, Val94Ala.