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Natural variation of H3K27me3 determines genes important for cell fate in the unicellular eukaryotic model Phaeodactylum tricornutum

ABSTRACT: In multicellular organisms, tri-methylation of lysine 27 of histone H3 (H3K27me3) was shown to be deposited by Polycomb Repressive Complex 2 (PRC2) to establish and maintain silencing, critical for cell fate and developmentally regulated processes. PRC2 complex is absent in both yeast Saccharomyces cerevisiae and S. pombe which initially suggested that PRC2 arose with the emergence of multicellularity. However, its discovery in several microalgae questions its role in this important class of organisms. Here, we show using mutants of the homologue of catalytic unit of PRC2, enhancer of zeste E(z) in the model diatom P. tricornutum (Pt), which presents different morphotypes (fusiform, triradiate, oval and cruciform) that Pt E(z) is responsible of di and tri-methylation of lysine 27. Indeed, H3K27me3 depletion causes the distortion of the morphology providing evidence for a role of H3K27me3 in cell differentiation in unicellular species. H3K27me3 genome wide profiling in fusiform and triradiate further revealed genes important for cell identity. These results suggest a role of PRC2 and its associated mark in cell fate in unicellular species and their ancestral function in a broad evolutionary context.

INSTRUMENT(S): TripleTOF 6600

ORGANISM(S): Phaeodactylum Tricornutum

SUBMITTER: Guillaume Arras

LAB HEAD: Damarys Loew

PROVIDER: PXD012347 | Pride | 2020-12-07

REPOSITORIES: Pride

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Project description:Gliadin triggers T-cell mediated immunity in celiac disease, and has cytotoxic effects on enterocytes mediated through obscure mechanisms. In addition, gliadin transport mechanisms, potential cell surface receptors and gliadin-activated downstream signaling pathways are not completely understood. In order to screen for novel downstream gliadin target genes we performed a systematic whole genome expression study on intestinal epithelial cells. Undifferentiated Caco-2 cells were exposed to pepsin- and trypsin- digested gliadin (PT-G), a blank pepsin-trypsin control (PT) and to a synthetic peptide corresponding to gliadin p31-43 peptide for six hours. RNA from four different experiments was used for hybridization on Agilent one color human whole genome DNA microarray chips. The microarray data were analyzed using the Bioconductor package LIMMA. Genes with nominal p < 0.01 were considered statistically significant. Compared to the untreated cells 1705, 1755 and 211 probes were affected by PT-G, PT and p31-43 respectively. 46 probes were significantly different between PT and PT-G treated cells. Among the p31-43 peptide affected probes, 10 and 21 probes were affected by PT-G and PT respectively. Only PT-G affected genes could be validated by quantitative real-time polymerase chain reaction. All the genes were, nonetheless, also affected to a comparable level by PT treated negative controls. In conclusion, we could not replicate previously reported direct effects of gliadin peptides on enterocytes. The PT-G affected genes in the microarray analysis were validated by qRT-PCR, however these genes were also affected by PT treated negative controls suggesting that certain epitopes derived from pepsin and trypsin may also affect epithelial cell gene transcription. Our study demonstrates novel non-enzymatic effects of pepsin and trypsin on cells and calls for proper controls in pepsin and trypsin digested gliadin experiments. It is conceivable that gliadin effects on enterocytes are secondary mediated through oxidative stress, NFkB activation and IL-15 up-regulation. In total, 16 samples were analyzed of which 4 were control (MED) samples, 4 samples of p31-43 treatment, 4 samples of PT treatmetn and 4 samples of PT-G treatment

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Natural variation of H3K27me3 determines genes important for cell fate in the unicellular eukaryotic model Phaeodactylum tricornutum

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