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Optimized Sample Preparation Workflow for Improved Identification of Ghost Proteins

ABSTRACT: Large scale proteomic strategies rely on database interrogation. Thus, only referenced proteins can be identified. Recently, Alternative Proteins (AltProts) translated from nonannotated Alternative Open reading frame (AltORFs) were discovered using customized databases. Because of their small size which confers them peptide-like physicochemical properties, they are more difficult to detect using standard proteomics strategies. In this study, we tested different preparation workflows for improving the identification of AltProts in NCH82 human glioma cell line. The highest number of identified AltProts was achieved with RIPA buffer or boiling water extraction followed by acetic acid precipitation.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

DISEASE(S): Brain Glioblastoma Multiforme

SUBMITTER: Tristan Cardon

LAB HEAD: Michel Salzet

PROVIDER: PXD024134 | Pride | 2021-02-15

REPOSITORIES: Pride

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Project description:Our previous research demonstrated that caffeine exposure on embryonic day (E) 8.5 increased body weight, altered cardiac morphology and function in adult male mice. However, these adverse effects were not observed in adenosine A1 receptor knockout (A1AR-/-) mice. Our hypothesis is that A1AR action mediates changes in DNA methylation patterns in mice exposed in utero to caffeine and that these changes in methylation lead to long-term effects in adult mice. To test this hypothesis, DNA Methylation 2.1M Deluxe Promoter Arrays (NimbleGen) were used to examine the methylation patterns of DNA isolated from adult left ventricles of the A1AR knockout line exposed to 20 mg/kg caffeine at E8.5 in utero. In A1AR+/+ mice, 4,896 hypermethylated and 2,823 hypomethylated regions were discovered in the left ventricles of the caffeine group compared to the normal saline group. In A1AR-/- mice, 1,024 hypermethylated and 1,757 hypomethylated regions were found in the caffeine group. The differentially methylated regions (DMRs) in the caffeine treated A1AR+/+ hearts mapped to 6,148 genes, 4,853 promoters, 4,111 primary transcripts, 816 CpG islands, and 98 miRNAs. Functional annotation clustering of genes revealed that many genes were involved in the development of hypertrophic cardiomyopathy and other heart diseases, which may explain our earlier findings of thickening of the left ventricular wall after in utero caffeine treatment. The methylation changes in several DMRs, mef2c, ins2, tnnt2, and myh6, were validated by bisulfite sequencing. In summary, in utero caffeine exposure caused DNA methylation changes in adult left ventricles and that these changes may be mediated by A1ARs. Pregnant mice were injected at embryonic day 8.5 with 0.9% NaCl (vehicle) or 20 mg/kg caffeine in vehicle i.p. Pups were born and raised until 8-10 weeks of age. Analysis was performed on the following groups vehicle A1AR+/+ (veh+/+), vehicle A1AR-/- (veh-/-), caffeine A1AR+/+ (caff+/+), and caffeine A1AR-/- (caff-/-). Genomic DNA from left ventricles of adult male mice was used. Two biological replicates were measured for each group.

Project description:Traditional serrated adenoma (TSA) remains the least understood of all the colorectal adenomas although these lesions have been associated with a significant cancer risk- twice that of the conventional adenoma (CAD) and of the sessile serrated adenoma (SSA/P). This study was performed to investigate the proteomic profiles of the different colorectal adenomas to better assess the pathogenesis of TSA. We performed a global quantitative expression profile of 44 colorectal adenomas (12 TSA, 15 CAD, 17 SSA/Ps) and 17 normal colonic mucosa, conserved as formalin-fixed paraffin-embedded samples, by the label-free quantification (LFQ) method. Unsupervised consensus hierarchical clustering applied to the whole proteomic profile of the 44 colorectal adenomas identified four subtypes. The C1 and C2 were well-individualized clusters composed of most of the CAD (14/15) and most of the SSA (13/17) respectively. This is consistent with the fact that CAD and SSA/Ps are homogeneous but distinct colorectal adenoma entities. In contrast, TSA were subdivided into C3 and C4 clusters that also contained CAD and SSA/Ps, consistent with the more heterogeneous entity of TSA at the morphological and molecular levels. The comparison of the proteome expression profile between the adenoma subtypes and normal colonic mucosa further confirmed the heterogeneous nature of TSA that merged either on CAD or SSA, while CAD and TSA formed homogeneous and distinct entities. Furthermore, we identified LEFTY1 a new potential marker for TSA that may be relevant for the TSA pathogenesis. LEFTY1 is an inhibitor of the Nodal/TGFb pathway that we found to be one of the most overexpressed proteins specifically in the TSA and confirmed by immunohistochemistry. Taken together, our study confirms that CAD and SSA form homogenous but distinct colorectal adenoma entities while TSA are an heterogeneous entity and may arise from either SSA or from normal mucosa that will evolve along the conventional adenoma pathway.

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Optimized Sample Preparation Workflow for Improved Identification of Ghost Proteins

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