Smooth Muscle miRNAs Are Critical for Post-Natal Regulation of Blood Pressure and Vascular Function

Phenotypic modulation of smooth muscle cells (SMCs) plays a key role in vascular disease, including atherosclerosis. Several transcription factors have been suggested to regulate phenotypic modulation of SMCs but the decisive mechanisms remain unknown. Recent reports suggest that specific microRNAs (miRNAs) are involved in SMC differentiation and vascular disease but the global role of miRNAs in postnatal vascular SMC has not been elucidated. Thus, the objective of this study was to identify the role of Dicer-dependent miRNAs for blood pressure regulation and vascular SMC contractile function and differentiation in vivo. Tamoxifen-inducible and SMC specific deletion of Dicer was achieved by Cre-Lox recombination. Deletion of Dicer resulted in a global loss of miRNAs in aortic SMC. Furthermore, Dicer-deficient mice exhibited a dramatic reduction in blood pressure due to significant loss of vascular contractile function and SMC contractile differentiation as well as vascular remodeling. Several of these results are consistent with our previous observations in SM-Dicer deficient embryos. Therefore, miRNAs are essential for maintaining blood pressure and contractile function in resistance vessels. Although the phenotype of miR-143/145 deficient mice resembles the loss of Dicer, the phenotypes of SM-Dicer KO mice were far more severe suggesting that additional miRNAs are involved in maintaining postnatal SMC differentiation

Clock genes and their genomic distributions in three species of salmonid fishes: Associations with genes regulating sexual maturation and cell cycling

<p>Abstract</p> <p>Background</p> <p>Clock family genes encode transcription factors that regulate clock-controlled genes and thus regulate many physiological mechanisms/processes in a circadian fashion. Clock1 duplicates and copies of Clock3 and NPAS2-like genes were partially characterized (genomic sequencing) and mapped using family-based indels/SNPs in rainbow trout (RT)(<it>Oncorhynchus mykiss</it>), Arctic charr (AC)(<it>Salvelinus alpinus</it>), and Atlantic salmon (AS)(<it>Salmo salar</it>) mapping panels.</p> <p>Results</p> <p>Clock1 duplicates mapped to linkage groups RT-8/-24, AC-16/-13 and AS-2/-18. Clock3/NPAS2-like genes mapped to RT-9/-20, AC-20/-43, and AS-5. Most of these linkage group regions containing the Clock gene duplicates were derived from the most recent 4R whole genome duplication event specific to the salmonids. These linkage groups contain quantitative trait loci (QTL) for life history and growth traits (i.e., reproduction and cell cycling). Comparative synteny analyses with other model teleost species reveal a high degree of conservation for genes in these chromosomal regions suggesting that functionally related or co-regulated genes are clustered in syntenic blocks. For example, anti-müllerian hormone (amh), regulating sexual maturation, and ornithine decarboxylase antizymes (oaz1 and oaz2), regulating cell cycling, are contained within these syntenic blocks.</p> <p>Conclusions</p> <p>Synteny analyses indicate that regions homologous to major life-history QTL regions in salmonids contain many candidate genes that are likely to influence reproduction and cell cycling. The order of these genes is highly conserved across the vertebrate species examined, and as such, these genes may make up a functional cluster of genes that are likely co-regulated. CLOCK, as a transcription factor, is found within this block and therefore has the potential to cis-regulate the processes influenced by these genes. Additionally, clock-controlled genes (CCGs) are located in other life-history QTL regions within salmonids suggesting that at least in part, trans-regulation of these QTL regions may also occur via Clock expression.</p

Identification of a Mouse Homolog of the Human BTEB2 Transcription Factor as a β-Catenin-Independent Wnt-1-Responsive Gene

The Wnt/Wg signaling pathway functions during development to regulate cell fate determination and patterning in various organisms. Two pathways are reported to lie downstream of Wnt signaling in vertebrates. The canonical pathway relies on the activation of target genes through the β-catenin–Lef/TCF complex, while the noncanonical pathway employs the activation of protein kinase C (PKC) and increases in intracellular calcium to induce target gene expression. cDNA subtractive hybridization between a cell line that overexpresses Wnt-1 (C57MG/Wnt-1) and the parental cell line (C57MG) was performed to identify downstream target genes of Wnt-1 signaling. Among the putative Wnt-1 target genes, we have identified a mouse homolog of the gene encoding human transcription factor basic transcription element binding protein 2 (mBTEB2). The mBTEB2 transcript is found at high levels in mammary tissue taken from a transgenic mouse overexpressing Wnt-1 (both tissue prior to active proliferation and tumor tissue) but is barely detectable in wild-type mouse mammary glands. The regulation of mBTEB2 by Wnt-1 signaling in tissue culture occurs through a β-catenin–Lef/TCF-independent mechanism, as it is instead partially regulated by PKC. The Wnt-1-induced, PKC-dependent activation of mouse BTEB2 in C57MG cells, as well as the ability of Wnt-1 to stabilize β-catenin in these cells, is consistent with the hypothesis that both the noncanonical and canonical Wnt pathways are activated concomitantly in the same cell. These results suggest that mBTEB2 is a biologically relevant target of Wnt-1 signaling that is activated through a β-catenin-independent, PKC-sensitive pathway in response to Wnt-1