Immediate Early Response 3 Research Articles

Role of the immediate early response 3 (IER3) gene in cellular stress response, inflammation and tumorigenesis

The expression of the early response gene immediate early response 3 (IER3), formerly known as IEX-1, is induced by a great variety of stimuli, such as growth factors, cytokines, ionizing radiation, viral infection and other types of cellular stress. Being of a rather unique protein structure not sharing any similarity to other vertebrate proteins, IER3 plays a complex and to some extent contradictory role in cell cycle control and apoptosis. As outlined in this review, these effects of IER3 relate to an interference with certain signalling pathways, in particular NF-κB, MAPK/ERK and PI3K/Akt. In addition to numerous functional data relying on cell culture based studies, transgenic and knock-out mouse models revealed an involvement of IER3 expression in immune functions and in the physiology of the cardiovascular system. Deficiency of IER3 expression in mice results in an aberrant immune regulation and enhanced inflammation, in an alteration of blood pressure control and hypertension or in an impaired genomic stability. A number of patient related studies revealed an involvement of IER3 in tumorigenesis in a cell-type dependent but not yet understood manner. Future studies should establish the potential of IER3 as a new predictive marker and as a molecular target in human diseases such as cancer, inflammatory diseases or hypertension.

Analysis of potential transcriptomic biomarkers for Huntington's disease in peripheral blood

Highly quantitative biomarkers of neurodegenerative disease remain an important need in the urgent quest for disease-modifying therapies. For Huntington's disease (HD), a genetic test is available (trait marker), but necessary state markers are still in development. In this report, we describe a large battery of transcriptomic tests explored as state biomarker candidates. In an attempt to exploit the known neuroinflammatory and transcriptional perturbations of disease, we measured relevant mRNAs in peripheral blood cells. The performance of these potential markers was weak overall, with only one mRNA, immediate early response 3 (IER3), showing a modest but significant increase of 32% in HD samples compared with controls. No statistically significant differences were found for any other mRNAs tested, including a panel of 12 RNA biomarkers identified in a previous report [Borovecki F, Lovrecic L, Zhou J, Jeong H, Then F, Rosas HD, Hersch SM, Hogarth P, Bouzou B, Jensen RV, et al. (2005) Proc Natl Acad Sci USA 102:11023-11028]. The present results may nonetheless inform the future design and testing of HD biomarker strategies.

Complementary action of the PGC-1 coactivators in mitochondrial biogenesis and brown fat differentiation

Mitochondria play an essential role in the ability of brown fat to generate heat, and the PGC-1 coactivators control several aspects of mitochondrial biogenesis. To investigate their specific roles in brown fat cells, we generated immortal preadipocyte lines from the brown adipose tissue of mice lacking PGC-1alpha. We could then efficiently knockdown PGC-1beta expression by shRNA expression. Loss of PGC-1alpha did not alter brown fat differentiation but severely reduced the induction of thermogenic genes. Cells deficient in either PGC-1alpha or PGC-1beta coactivators showed a small decrease in the differentiation-dependant program of mitochondrial biogenesis and respiration; however, this increase in mitochondrial number and function was totally abolished during brown fat differentiation when both PGC-1alpha and PGC-1beta were deficient. These data show that PGC-1alpha is essential for brown fat thermogenesis but not brown fat differentiation, and the PGC-1 coactivators play an absolutely essential but complementary function in differentiation-induced mitochondrial biogenesis.

Demethylation Profiling of CD34-Positive Hematopoietic Cells in Patients with Myelodysplastic Syndromes.

Myelodysplastic syndromes (MDS) are a genetic and epigenetic disease of the hematopoietic stem cell. Aberrant CpG islands methylation in the contex of the promoter of multiple genes plays a pivotal role in the pathogenesis of MDS and leads to silencing of tumor suppressor genes, including cell-cycle inhibitors, inducers of apoptosis, DNA repair genes, transcription factors, cell adhesion mediators, hormonal receptors and detoxifiers. Demethylating agents, such as decitabine and azacitidine, are able to revert epigenetic silencing induced by hypermethylation and are currently used to treat all subtypes of MDS. Some of the target genes of demethylating drugs have been well studied and correlated to clinical response of patients, such as p15INK4B, but most of them remain to be identified and characterized. We isolated CD34+ cells from two patients with previously untreated MDS, a 70 year old female, with a diagnosis of Refractory Anemia with Excess Blasts (RAEB) and a complex karyotype including deletion of 5q11–q34 and trisomy 8, and a 59 years old male, with a diagnosis of RAEB in transformation, according to FAB and a normal karyotype. CD34+ cells were isolated from bone marrow samples by immunomagnetic beads, with a yield of about 2 x 106 cells per patients. Purity of the CD34+ cell fraction, evaluated by flow cytometry, was 58% and 86%, respectively. Cells were cultured in 24-well plates in IMDM medium with L-Glutamine, antibiotics, 30% of inactivated Foetal Bovine Serum and 10 ng/ml each of IL-3, Stem Cell Factor (SCF), Thrombopoietin and FLT3-ligand. After 24 hours, decitabine was added to the culture medium to a final concentration of 1 m M. A corresponding amount of acetic acid was added to different wells for the mock treatment control. Each experiment was conducted in triplicate. Cells were collected after 72 hours of treatment and RNA was extracted by the Qiagen RNeasy Kit, processed by two-cycle cDNA synthesis kit (Invitrogen), in vitro transcripted to cRNA and hybridized on Affymetrix HG-U133A chips. Five chips were used for each patient: three for treated cells and two for mock -treated cells. Microarray data were normalized and analysed by GeneSpring software version 7.2 and the ANOVA Welch's test was applied. We selected genes with a p value less than 0.01 and a fold change higher than 2. Using these conditions, 60 genes were upregulated by decitabine in both patients. Some of the most interesting genes were GATA binding protein 2 (GATA2), cyclin-dependent kinase inhibitor 1A (CDKN1A, p21), cyclin A1 (CCNA1), decay accelerating factor for complement (CD55, DAF), immediate early response 3 (IER3), nuclear factor interleukin 3 regulated (NFIL3) and chemokine (C-X-C motif) receptor 4 (CXCR4).Interestingly, the patient with a normal karyotype showed a higher percentage of up-regulated genes after decitabine treatment compared to the patient with the 5q11-q34 deletion and a trisomy 8. This suggests that epigenetic changes in gene expression may have higher impact when the karyotype is normal. Functional significance of these data remains to be elucidated. Expression and methylation status of these genes will be investigated in a larger group of MDS patients. This approach aims to characterize new genes, as methylation targets in MDS and possible markers of disease, and to identify patients responding to demethylating agents.