SummaryThe gene encoding the ABCC6 protein, an ABC transporter of the multidrug resistance-associated protein (MRP), is mainly expressed in liver and kidney. Mutations in ABCC6 are responsible for the development of the pseudoxanthoma elasticum (PXE) phenotype. PXE is a recessive disease characterized by the calcification of elastic fibers resulting in dermal, vascular and ocular clinical manifestations. The physiological function of ABCC6 and the rodent orthologs Abcc6 is unknown and their precise relationship to elastic fibers is only a matter of speculation. Despite several studies focused on the transcriptional regulation of ABCC6/Abcc6, the molecular signals conferring the tissue-specificity to the ABCC6/Abcc6 expression are not well defined. In this report, we determined the level of the mouse Abcc6 promoter methylation in tissues with low level of expression (tail extremity and skin), intermediate (kidney) and high level of expression (liver). We observed that high and moderate levels of methylation correlated with low levels of Abcc6 expression. Moreover, we determined that CpG methylation of the Abcc6 proximal promoter region was interfering with the binding of the Sp1 transcription factor thereby inhibiting Sp1-dependent transactivation. Thus, our data provides the first direct evidence that an epigenetic mechanism regulates the binding of the transcription factor Sp1 to the proximal promoter and participates in the tissue-specific expression control of the mouse Abcc6 gene.

Background: Early, accurate diagnosis of mild traumatic brain injury (mTBI) can improve clinical outcomes for patients, but mTBI remains difficult to This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

SUMMARYMutations in an ABC transporter gene called ABCC6 are responsible for pseudoxanthoma elasticum (PXE), a rare heritable disease characterized by elastic fiber calcification in skin, ocular and vascular tissues. The presumed function of this ABC transporter is to export metabolites from polarized cells. However, the endogenous substrate(s) are unknown and the exact relationship with elastic fibers is unclear. As ABCC6 is expressed at high level only in liver and kidneys, tissues seemingly unrelated to the PXE phenotype, we explored the transcriptional regulation of the murine Abcc6 gene to define transcriptional regulation conferring tissue specificity and to gather clues on its possible biological function. We cloned 2.9 kb of the mAbcc6 5′-flanking region and several deletion constructs linked to a luciferase reporter gene. We delineated a proximal promoter and a liver-specific enhancer region. We also demonstrated that the proximal region is a TATA-less promoter requiring an intact CCAATbox and Sp1 binding for its basal activity. By using reporter assays and chromatin immunoprecipitations, we showed that HNF4α and surprinsingly, NF-E2, enhanced the mAbcc6 promoter activity. The involvement of both HNF4α and NF-E2 in the mAbcc6 gene regulation suggests that Abcc6 might be involved in a detoxification processes related to hemoglobin or heme.

␤-Thalassemia and pseudoxanthoma elasticum (PXE) are distinct genetic disorders. Yet, a dystrophic mineralization phenotype similar to PXE has frequently been associated with ␤-thalassemia or sickle cell anemia patients of Mediterranean descent. These calcifications are clinically and structurally identical to inherited PXE. As we previously excluded the presence of PXE-causing mutations in the ABCC6 gene of ␤-thalassemia patients with PXE manifestations, we hypothesized that a molecular mechanism independent of gene mutations either altered the ABCC6 gene expression or disrupted the biologic properties of its product in the liver or kidneys, which are the tissues with the highest levels of expression. To test this possibility, we investigated Abcc6 synthesis in the liver and kidneys of a ␤-thalassemia mouse model (Hbb th3/؉ ). We found a progressive liver-specific down-regulation of the Abcc6 gene expression and protein levels by quantitative PCR, Western blotting, and immunofluorescence. The levels of Abcc6 protein decreased significantly at 6 months of age and stabilized at 10 months and older ages at ϳ25% of the wild-type protein levels. We studied the transcriptional regulation of the Abcc6 gene in wild-type and Hbb th3/؉ mice, and we identified the erythroid transcription factor NF-E2 as the main cause of the transcriptional down-regulation using transcription factor arrays and chromatin immunoprecipitation. The Hbb th3/؉ mice did not develop spontaneous calcification as seen in the Abcc6 ؊/؊ mice probably because the Abcc6 protein decrease occurred late in life and was probably insufficient to promote mineralization in the Hbb th3/؉ mouse C57BL/6J genetic background. Nevertheless, our result suggested that a similar decrease of ABCC6 expression occurs in the liver of ␤-thalassemia patients and may be responsible for their frequent PXE-like manifestations.

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Recurrent concussions increase risk for persistent post-concussion symptoms, and may lead to chronic neurocognitive deficits. Little is known about the molecular pathways that contribute to persistent concussion symptoms. We hypothesized that salivary measurement of microribonucleic acids (miRNAs), a class of epitranscriptional molecules implicated in concussion pathophysiology, would provide insights about the molecular cascade resulting from recurrent concussions. This hypothesis was tested in a case-control study involving 13 former professional football athletes with a history of recurrent concussion, and 18 age/sex-matched peers. Molecules of interest were further validated in a cross-sectional study of 310 younger individuals with a history of no concussion (n = 230), a single concussion (n = 56), or recurrent concussions (n = 24). There was no difference in neurocognitive performance between the former professional athletes and their peers, or among younger individuals with varying concussion exposures. However, younger individuals without prior concussion outperformed peers with prior concussion on three balance assessments. Twenty salivary miRNAs differed (adj. p < 0.05) between former professional athletes and their peers. Two of these (miR-28-3p and miR-339-3p) demonstrated relationships (p < 0.05) with the number of prior concussions reported by younger individuals. miR-28-3p and miR-339-5p may play a role in the pathophysiologic mechanism involved in cumulative concussion effects.

Abstract:In spite of current standard therapies to target the major pathomechanisms in myocardial infarction (MI), inflammatory gene expression patterns have been consistently revealed in MI patients. In a multiethnic cohort, we aimed to identify MI-associated pathomechanisms that may be unresponsive to medical treatment to improve diagnosis and therapy. Gene expression profiles in whole blood were analyzed in medicated Asian, African American and Caucasian patients living in Hawaii with a history of early MI and age, ethnicity, risk factor and medication-matched controls. PANTHER ontological and Ingenuity Pathway analysis and functional evaluation of the consistently differentially expressed genes identified coordinated up-regulation of genes for inflammation (LGALS3, PTX3, ZBTB32, BCL2L1), T-cell activation (IL12RB1, VAV3, JAG1, CAMP), immune imbalance (IL-8, IL2RA, CCR7, AHNAK), and active atherosclerosis (NR1H4, BIN1, GSTT1, MARCO) that persist in MI patients in spite of concerted treatment efforts to control vascular pathology. Furthermore, significant ethnic differences appear to exist within the active disease mechanisms that need to be further investigated to identify key targets for effective medical intervention.