| 1. |
- Kaleviste, Epp, et al.
(författare)
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Interferon signature in patients with STAT1 gain-of-function mutation is epigenetically determined
- 2019
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Ingår i: European Journal of Immunology. - : WILEY. - 0014-2980 .- 1521-4141. ; 49:5, s. 790-800
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Tidskriftsartikel (refereegranskat)abstract
- STAT1 gain-of-function (GOF) variants lead to defective Th17 cell development and chronic mucocutaneous candidiasis (CMC), but frequently also to autoimmunity. Stimulation of cells with STAT1 inducing cytokines like interferons (IFN) result in hyperphosphorylation and delayed dephosphorylation of GOF STAT1. However, the mechanism how the delayed dephosphorylation exactly causes the increased expression of STAT1-dependent genes, and how the intracellular signal transduction from cytokine receptors is affected, remains unknown. In this study we show that the circulating levels of IFN-alpha were not persistently elevated in STAT1 GOF patients. Nevertheless, the expression of interferon signature genes was evident even in the patient with low or undetectable serum IFN-alpha levels. Chromatin immunoprecipitation (ChIP) experiments revealed that the active chromatin mark trimethylation of lysine 4 of histone 3 (H3K4me3), was significantly enriched in areas associated with interferon-stimulated genes in STAT1 GOF cells in comparison to cells from healthy donors. This suggests that the chromatin binding of GOF STAT1 variant promotes epigenetic changes compatible with higher gene expression and elevated reactivity to type I interferons, and possibly predisposes for interferon-related autoimmunity. The results also suggest that epigenetic rewiring may be responsible for treatment failure of Janus kinase 1/2 (JAK1/2) inhibitors in certain patients.
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| 2. |
- Liu, Liang, 1972-
(författare)
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Epigenetic Control of Mammalian Development : Studies on an imprinting control region
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A subset of autosomal genes is preferentially or exclusively expressed from one of the parental alleles. This phenomenon, termed genomic imprinting, is highlighted by the neighboring Igf2 and H19 genes, which are monoallelically expressed on opposite parental chromosomes. These features are governed by a 2.2 kb differentially methylated domain, hereafter termed imprinting control region (ICR) in the 5'-flank of the H19 gene. It was shown that the H19 ICR displays unique chromatin conformation features with nuclease hypersensitive sites in linker elements flanked by positioned nucleosomes on the maternally derived allele. Moreover, it was demonstrated that the unmethylated ICR functions as a unidirectional chromatin insulator, which involves the chromatin insulator protein CTCF.The methylated and unmethylated states of the paternal and maternal H19 ICR alleles are known to be stably propagated in the soma throughout development. During in vitro organogenesis, however, the stability of the H19 ICR was demonstrated to be disturbed due to presence of environmental cues. The methylation plasticity of the H19 ICR was nevertheless tolerated without affecting the imprinted status of either Igf2 or H19 genes. It was also observed that some human cancer cell lines possess strong de novo methylation activities. Following transfection of an episomal construct, which contains the H19 miningene with the core H19 ICR and its human counterpart, the H19 reporter gene became rapidly do novo methylated and eventually silenced in choriocarcinoma cells (JEG-3), but not in heptoma cells (HEP3B). Although the H19 ICR was initially protected from being methylated by JEG3 cells, progressive waves of de novo methylation generated a heavily methylated H19 ICR in later passages, with concomitant loss of its insulator function. It is generally accepted that parental marks undergo erasure and reestablishment during gametogenesis. It was shown that CTCF and its paralogue, BORIS, are expressed in reciprocal patterns during adult male germline development. By means of laser-dissection and bisulfite genomic sequencing, it was observed that de novo methylation of CTCF target sites occurred in BORIS-expressing spermatocytes that exhibit repression of CTCF gene. It was also shown, by chromatin immunopurification analyses of adult mouse testes, that CTCF and BORIS were associated with H19 ICR. A model is proposed to explain the acquisition of differential methylation marks in molecular terms.
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