Summary MicroRNAs (miRNAs) regulate various biological processes, but evidence for miRNAs that control the differentiation program of specific neural cell types has been elusive. To determine the role of miRNAs in the formation of myelinating oligodendrocytes, we selectively deleted a miRNA-processing enzyme Dicer1 in oligodendrocyte lineage cells. Mice lacking Dicer1 display severe myelinating deficits despite an expansion of oligodendrocyte progenitor pool. To search for miRNAs responsible for the induction of oligodendrocyte maturation, we identified miR-219 and miR-338 as oligodendrocyte-specific miRNAs in spinal cord. Overexpression of these miRNAs is sufficient to promote oligodendrocyte differentiation. Additionally, blockage of these miRNA activities in oligodendrocyte precursor culture and knockdown of miR-219 in zebrafish inhibit oligodendrocyte maturation. miR-219 and miR-338 function in part by directly repressing negative regulators of oligodendrocyte differentiation, including transcription factors Sox6 and Hes5. These findings illustrate that miRNAs are important regulators of oligodendrocyte differentiation, providing new targets for myelin repair.

This report describes the synthesis of two cyclic RGD (Arg-Gly-Asp) conjugates, HYNIC-2PEG 4 -dimer (HYNIC = 6-hydrazinonicotinyl; 2PEG 4 -dimer = E[PEG 4 -c(RGDfK)] 2 ; and PEG 4 = 15-amino-4,7,10,13-tetraoxapentadecanoic acid) and HYNIC-3PEG 4 -dimer (3PEG 4 -dimer = PEG 4 -E [PEG 4 -c(RGDfK)] 2 ), and evaluation of their 99m Tc complexes [ 99m Tc(HYNIC-2PEG 4 -dimer) (tricine)(TPPTS)] ( 99m Tc-2PEG 4 -dimer: TPPTS = trisodium triphenylphosphine-3,3′,3″-trisulfonate) and [ 99m Tc(HYNIC-3PEG 4 -dimer)(tricine)(TPPTS)] ( 99m Tc-3PEG 4 -dimer) as novel radiotracers for imaging integrin α v β 3 expression in athymic nude mice bearing U87MG glioma and MDA-MB-435 breast cancer xenografts. The integrin α v β 3 binding affinities of RGD peptides were determined by competitive displacement of 125 I-c(RGDyK) on U87MG glioma cells. It was found that the two PEG 4 linkers between RGD motifs in HYNIC-2PEG 4 -dimer (IC 50 = 2.8 ± 0.5 nM) and HYNIC-3PEG 4 -dimer (IC 50 = 2.4 ± 0.7 nM) are responsible for their higher integrin α v β 3 binding affinity than that of HYNIC-PEG 4 -dimer (PEG 4 -dimer = PEG 4 -E[c(RGDfK)] 2 ; IC 50 = 7.5 ± 2.3 nM). Addition of extra PEG 4 linker in HYNIC-3PEG 4 -dimer has little impact on integrin α v β 3 binding affinity. 99m Tc-2PEG 4 -dimer and 99m Tc-3PEG 4 -dimer were prepared in high yield with >95% radiochemical purity and the specific activity of > 10 Ci/μmol. Biodistribution studies clearly demonstrated that PEG 4 linkers are particularly useful for improving the tumor uptake and clearance kinetics of 99m Tc-2PEG 4 -dimer and 99m Tc-3PEG 4 -dimer from non-cancerous organs. It was also found that there was a linear relationship between the tumor size and radiotracer tumor uptake expressed as %ID (percentage of the injected dose) in U87MG glioma and MDA-MB-435 breast tumor models. The blocking experiment showed that the tumor uptake of 99m Tc-2PEG 4 -dimer is integrin α v β 3 -mediated. In the metabolism study, 99m Tc-2PEG 4 -dimer had high metabolic stability during its excretion from renal and hepatobiliary routes. 99m Tc-3PEG 4 -dimer also remained intact during thee excretion from the renal route, but, had ~30% metabolism during the excretion from the hepatobiliary route. Planar imaging studies in U87MG glioma and MDA-MB-435 breast tumor models showed that the tumors of ~5 mm in diameter could be readily visualized with excellent contrast. Thus, 99m Tc-3PEG 4 -dimer is a very promising radiotracer for the early detection of integrin α v β 3 -positive tumors, and may have the potential for non-invasive monitoring of tumor growth or treatment efficacy.

Differently sized NaGdF(4) nanocrystals with narrow particle size distributions were synthesized by a high temperature approach. Upon ligand exchange, the as-prepared hydrophobic NaGdF(4) nanocrystals were transferred into water by using asymmetric PEGs simultaneously bearing phosphate and maleimide groups. Further investigations demonstrated that the water-soluble NaGdF(4) nanocrystals, coated by PEG bearing two phosphate groups on the same side, exhibit not only excellent colloidal stability in water and PBS buffer, but also higher T1 relaxivity than Gd-DTPA (Magnevist). Through "click" reaction between the maleimide residue on particle surface and thiol group from the partly reduced anti-EGFR monoclonal antibody (mAb), NaGdF(4)-PEG-mAb nanoprobes were constructed, and their biocompatibility and binding specificity were evaluated through in vitro experiments. A series of in vivo experiments were then carried out for detecting intraperitoneal tumor xenografts in nude mice by using magnetic resonance (MR) imaging technique. The results revealed that the NaGdF(4)-PEG-mAb probes possessed satisfying tumor-specific targeting ability and strong MR contrast enhancement effects.

Super-enhancers are important for controlling and defining the expression of cell-specific genes. With research on human disease and biological processes, human H3K27ac ChIP-seq datasets are accumulating rapidly, creating the urgent need to collect and process these data comprehensively and efficiently. More importantly, many studies showed that super-enhancer-associated single nucleotide polymorphisms (SNPs) and transcription factors (TFs) strongly influence human disease and biological processes. Here, we developed a comprehensive human super-enhancer database (SEdb, http://www.licpathway.net/sedb) that aimed to provide a large number of available resources on human super-enhancers. The database was annotated with potential functions of super-enhancers in the gene regulation. The current version of SEdb documented a total of 331 601 super-enhancers from 542 samples. Especially, unlike existing super-enhancer databases, we manually curated and classified 410 available H3K27ac samples from >2000 ChIP-seq samples from NCBI GEO/SRA. Furthermore, SEdb provides detailed genetic and epigenetic annotation information on super-enhancers. Information includes common SNPs, motif changes, expression quantitative trait locus (eQTL), risk SNPs, transcription factor binding sites (TFBSs), CRISPR/Cas9 target sites and Dnase I hypersensitivity sites (DHSs) for in-depth analyses of super-enhancers. SEdb will help elucidate super-enhancer-related functions and find potential biological effects.