Dax1 Up-Regulates Oct4 Expression in Mouse Embryonic Stem Cells via LRH-1 and SRA
ABSTRACT Dax1 (Nr0b1) is an atypical orphan nuclear receptor that has recently been shown to play a role in mouse embryonic stem (mES) cell pluripotency. Here we describe a mechanism by which Dax1 maintains pluripotency. In steroidogenic cells, Dax1 protein interacts with the NR5A nuclear receptor steroidogenic factor 1 (Nr5a1) to inhibit transcription of target genes. In mES cells, liver receptor homolog 1 (LRH-1, Nr5a2), the other NR5A family member, is expressed, and LRH-1 has been shown to interact with Dax1. We demonstrate by coimmunoprecipitation that Dax1 is, indeed, able to form a complex with LRH-1 in mES cells. Because Dax1 was historically characterized as an inhibitor of steroidogenic factor 1-mediated transcriptional activation, we hypothesized that Dax1 would inhibit LRH-1 action in mES cells. Therefore, we examined the effect of Dax1 on the LRH-1-mediated activation of the critical ES cell factor Oct4 (Pou5f1). Chromatin immunoprecipitation localized Dax1 to the Oct4 promoter at the LRH-1 binding site, and luciferase assays together with Dax1 overexpression and knockdown experiments revealed that, rather than repress, Dax1 accentuated LRH-1-mediated activation of the Oct4 gene. Similar to our previously published studies that defined the RNA coactivator steroid receptor RNA activator as the critical mediator of Dax1 coactivation function, Dax1 augmentation of LRH-1-mediated Oct4 activation is dependent upon steroid receptor RNA activator. Finally, utilizing published chromatin immunoprecipitation data of whole-genome binding sites of LRH-1 and Dax1, we show that LRH-1 and Dax1 commonly colocalize at 288 genes (43% of LRH-1 target genes), many of which are involved in mES cell pluripotency. Thus, our results indicate that Dax1 plays an important role in the maintenance of pluripotency in mES cells through interaction with LRH-1 and transcriptional activation of Oct4 and other genes.
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ABSTRACT: We report on a patient with genetically confirmed adrenal hypoplasia congenita (AHC) whose presentation and laboratory abnormalities were consistent with the more common condition, congenital adrenal hyperplasia (CAH). The patient presented with failure to thrive and salt wasting. General appearance showed marked hyperpigmentation and normal male genitalia. He displayed mildly elevated 17-hydroxyprogesterone and markedly elevated 11-deoxycortisol levels at baseline and with ACTH stimulation testing. Results were consistent with 11 -hydroxylase deficiency. He required glucocorticoids and high doses of mineralocorticoids. The marked elevation in 11-deoxycortisol directed our clinical reasoning away from a hypoplastic condition and towards a hyperplasic adrenal condition. Sequencing of the DAX1 gene (named for dosage-sensitive sex reversal (DSS) locus and the AHC locus on the X chromosome) revealed a missense mutation. A review of the literature revealed that elevated 11-deoxycortisol levels have been noted in kindreds with DAX1 mutations, but only when measured very early in life. A mouse model has recently been described that displays elevated 11-deoxycorticosterone levels and evidence for hyperplasia of the zona glomerulosa of the adrenal gland. We conclude that DAX1 testing may be considered in patients with laboratory evidence of 11 -hydroxylase deficiency, especially in those with severe salt wasting.02/2013; 2013:393584. DOI:10.1155/2013/393584
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ABSTRACT: We investigated the relationship between oct4 gene expression patterns and CpG sites methylation profiles during ES cell differentiation into neurons, and identified relevant binding factor. The oct4 gene expression level gradually declined as ES cell differentiation progressed, and the CpG sites in the oct4 proximal enhancer (PE) and promoter regions were methylated in concert with ES cell differentiation. An electro-mobility shift assay (EMSA) showed that putative proteins bind to CpG sites in the oct4 PE/promoter. We purified CpG binding proteins with DNAbinding purification method, and NonO was identified by liquid chromatography-mass spectrometry. EMSA with specific competitors revealed that NonO specifically binds to the conserved CCGGTGAC sequence in the oct4 promoter. Methylation at a specific cytosine residue (CC* GGTGAC) reduced the binding affinity of NonO for the recognition sequence. Chromatin immunoprecipitation analysis confirmed that NonO binds to the unmethylated oct4 promoter. There were no changes in the NonO mRNA and protein levels between ES cells and differentiated cells. The transcriptional role of NonO in oct4 gene expression was evaluated by luciferase assays and knockdown experiments. The luciferase activity significantly increased threefold when the NonO expression vector was cotransfected with the NonO recognition sequence, indicating that NonO has a transcription activator effect on oct4 gene expression. In accordance with this effect, when NonO expression was inhibited by siRNA treatment, oct4 expression was also significantly reduced. In summary, we purified NonO, a novel protein that binds to the CpG island of oct4 promoter, and positively regulates oct4 gene expression in ES cells.Moleculer Cells 11/2012; 35(1). DOI:10.1007/s10059-013-2273-1 · 2.24 Impact Factor
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ABSTRACT: There have been few testicular histology reports of adult patients with congenital adrenal hypoplasia/hypogonadal hypogonadism (AHC/HH), but Leydig cell hyperplasia has been observed, an indicator of the possibility of malignant transformation. We aimed to define the basis of AHC/HH in 4 pedigrees of different ethnic backgrounds. One patient was elected to have testicular biopsy which was examined for evidence of carcinoma in situ (CIS). NR0B1 mutation analysis was performed by sequence analysis. NR0B1 expression was investigated by RT-PCR. Testicular biopsy sections were stained with HE or immunostained for OCT3/4, an established marker of CIS. We identified NR0B1 variants in the 4 AHC pedigrees: pedigree 1 (United Arab Emirates), c.1130A>G predicting p.(Glu377Gly); pedigree 2 (English Caucasian), c.327C>A predicting p.(Cys109*); pedigree 3 (Oman), a 6-bp deletion of a direct repeat, c.857_862delTGGTGC predicting p.(Leu286_Val287del); pedigree 4 (English Caucasian), c.1168+1G>A, a regulatory variant within the NR0B1 splice donor site. This last male patient, aged 30 years, presented with evidence of HH but incomplete gonadotrophin deficiency, following an earlier diagnosis of Addison's disease at 3 years. Hormonal therapy induced virilisation. Testicular biopsy was performed. The c.1168+1G>A variant abrogated normal splicing of testicular mRNA. Histological examination showed poorly organised testicular architecture and absence of spermatozoa. Morphological analyses and the absence of immunohistochemical staining for OCT3/4 excluded the presence of malignant germ cell cancer and its precursor lesion, CIS. These studies add to the knowledge of the types and ethnic diversity of NR0B1 mutations and their associated phenotypes, and provide insight into the assessment and interpretation of testicular histology in AHC and HH.Sexual Development 09/2012; 6(6). DOI:10.1159/000342295 · 1.76 Impact Factor