Methylation enrichment pyrosequencing: combining the specificity of MSP with validation by pyrosequencing

It has been suggested that detection of aberrant DNA methylation in clinical specimens such as sputum or saliva may be a valuable tumour biomarker. Any clinically applicable detection technique must combine high sensitivity with high specificity. In this study we describe methylation enrichment pyrosequencing (MEP), which benefits from the high sensitivity and specificity of methylation-specific PCR (MSP) but has a second, confirmatory, pyrosequencing step. The pyrosequencing reaction is rapid, relatively inexpensive and offers significant logistical advantages over previously described validation methods. As proof of principle, we illustrate MEP using assays of p16 and cyclin A1 promoters in a methylated DNA dilution matrix and also in a clinical setting using paired saliva and oral tumour specimens. Our results confirm that mis-priming of MSP, with subsequent false positive results, can occur frequently (perhaps 10%) in assays combining high numbers of PCR cycles and low concentrations of starting DNA. In our clinical example, MEP of saliva-derived DNA was more sensitive than standard non-methylation-specific pyrosequencing as illustrated using p16 and cyclin A1 promoter methylation assays.     

Length of Variable Numbers of Tandem Repeats in the Carboxyl Ester Lipase (CEL) Gene May Confer Susceptibility to Alcoholic Liver Cirrhosis but Not Alcoholic Chronic Pancreatitis

BackgroundCarboxyl-ester lipase (CEL) contributes to fatty acid ethyl ester metabolism, which is implicated in alcoholic pancreatitis. The CEL gene harbours a variable number of tandem repeats (VNTR) region in exon 11. Variation in this VNTR has been linked to monogenic pancreatic disease, while conflicting results were reported for chronic pancreatitis (CP). Here, we aimed to investigate a potential association of CEL VNTR lengths with alcoholic CP.MethodsOverall, 395 alcoholic CP patients, 218 patients with alcoholic liver cirrhosis (ALC) serving as controls with a comparable amount of alcohol consumed, and 327 healthy controls from Germany and the United Kingdom (UK) were analysed by determination of fragment lengths by capillary electrophoresis. Allele frequencies and genotypes of different VNTR categories were compared between the groups.ResultsTwelve repeats were overrepresented in UK ACP patients (P = 0.04) compared to controls, whereas twelve repeats were enriched in German ALC compared to alcoholic CP patients (P = 0.03). Frequencies of CEL VNTR lengths of 14 and 15 repeats differed between German ALC patients and healthy controls (P = 0.03 and 0.008, respectively). However, in the genotype and pooled analysis of VNTR lengths no statistical significant association was depicted. Additionally, the 16–16 genotype as well as 16 repeats were more frequent in UK ALC than in alcoholic CP patients (P = 0.034 and 0.02, respectively). In all other calculations, including pooled German and UK data, allele frequencies and genotype distributions did not differ significantly between patients and controls or between alcoholic CP and ALC.ConclusionsWe did not obtain evidence that CEL VNTR lengths are associated with alcoholic CP. However, our results suggest that CEL VNTR lengths might associate with ALC, a finding that needs to be clarified in larger cohorts.     

Pyruvate sparing by butyrate and propionate in proliferating colonic epithelium

1. The effects of fasting and fasting followed by refeeding on the relative activities of the pyruvate dehydrogenase (PDH) complex and the tricarboxylic acid (TCA) cycle in isolated rat colonocytes were estimated by the rate of production of 14CO2 from [1-14C]pyruvate and [3-14C]pyruvate, respectively. 2. Decarboxylation of pyruvate by the PDH complex exceeded that by the TCA cycle in both fasted and fasted/refed colonocytes, was higher in distal than in proximal colon, and was stimulated by refeeding following a fast. 3. Oxidation of pyruvate by both the PDH complex and the TCA cycle was inhibited by butyrate. 4. Propionate alone had no effect, but synergized with butyrate to further reduce pyruvate decarboxylation by the TCA cycle. 5. Preferential utilization of butyrate by proliferating colonic epithelial cells is postulated to maximize the energy yield and spare pyruvate and its precursors for alternative synthetic roles necessary for active cell division.     

ATX expression and LPA signalling are vital for the development of the nervous system

Autotaxin (ATX) is a secreted glycoprotein widely present in biological fluids, originally isolated from the supernatant of melanoma cells as an autocrine motility stimulation factor. Its enzymatic product, lysophosphatidic acid (LPA), is a phospholipid mediator that evokes growth-factor-like responses in almost all cell types through G-protein coupled receptors. To assess the role of ATX and LPA signalling in pathophysiology, a conditional knockout mouse was created. Ubiquitous, obligatory deletion resulted to embryonic lethality most likely due to aberrant vascular branching morphogenesis and chorio-allantoic fusion. Moreover, the observed phenotype was shown to be entirely depended on embryonic, but not extraembryonic or maternal ATX expression. In addition, E9.5 ATX null mutants exhibited a failure of neural tube closure, most likely independent of the circulatory failure, which correlated with decreased cell proliferation and increased cell death. More importantly, neurite outgrowth in embryo explants was severely compromised in mutant embryos but could be rescued upon the addition of LPA, thus confirming a role for ATX and LPA signalling in the development of the nervous system. Finally, expression profiling of mutant embryos revealed attenuated embryonic expression of HIF-1a in the absence of ATX, suggesting a novel effector pathway of ATX/LPA.