Bivalent Histone Codes on WNT5A during Odontogenic Differentiation

Lineage-committed differentiation is an essential biological program during odontogenesis, which is tightly regulated by lineage-specific genes. Some of these genes are modified by colocalization of H3K4me3 and H3K27me3 marks at promoter regions in progenitors. These modifications, named "bivalent domains," maintain genes in a poised state and then resolve for later activation or repression during differentiation. Wnt5a has been reported to promote odontogenic differentiation in dental mesenchyme. However, relatively little is known about the epigenetic modulations on Wnt5a activation during tooth development. Here, we investigated the spatiotemporal patterns of H3K4me3 and H3K27me3 marks in developing mouse molars. Associated H3K4me3 methylases (mixed-lineage leukemia [MLL] complex) and H3K27me3 demethylases (JMJD3 and UTX) were dynamically expressed between early and late bell stage of human tooth germs and in cultured human dental papilla cells (hDPCs) during odontogenic induction. Poised WNT5A gene was marked by bivalent domains containing repressive marks (H3K27me3) and active marks (H3K4me3) on promoters. The bivalent domains tended to resolve during inducted differentiation, with removal of the H3K27me3 mark in a JMJD3-dependent manner. When JMJD3 was knocked down in cultured hDPCs, odontogenic differentiation was suppressed. The depletion of JMJD3 epigenetically repressed WNT5A activation by increased H3K27me3 marks. In addition, JMJD3 could physically interact with ASH2L, a component of the MLL complex, to form a coactivator complex, cooperatively modulating H3K4me3 marks on WNT5A promoters. Overall, our study reveals that transcription activities of WNT5A were epigenetically regulated by the negotiated balance between H3K27me3 and H3K4me3 marks and tightly mediated by JMJD3 and MLL coactivator complex, ultimately modulating odontogenic commitment during dental mesenchymal cell differentiation.

[Precision treatment after resistance to first-generation EGFR-TKI in patients with non-small cell lung cancer]

Recently, with the research progress in molecular classification, the treatment of advanced non-small cell lung cancer (NSCLC) has been established as a model of anti-tumor treatment of precision medicine. The discovery of epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) has transformed the treatment of NSCLC from platinum based doublet chemotherapy into era of target therapy. EGFR-TKI, such as erlotinib and gefitinib, have been recommended as standard first-line treatment of patients with EGFR mutation. However, acquired resistance, defined as tumor progression after initial response, seems to be an inevitable consequence of this treatment approach. Clinical modes of EGFR-TKI failure are classified into three types: dramatic progression, gradual progression and local progression. A threonine-to-methionine substitution (T790M) in exon 20 of the EGFR gene is the most common mechanism of resistance. Other mechanisms of resistance include MET amplification, epithelial to mesenchymal transition, small cell transformation, and PIK3CA mutation. This brief comment will provide an overview of the complex and heterogeneous problem of acquired resistance to EGFR-TKI therapy in NSCLC, and the clinical treatment options and new targeted drugs overcoming EGFR-TKI acquired resistance.

Investigation of bipolar resistive switching and the time-dependent SET process in silver sulfide/silver thin films and nanowire array structures

We report on the bipolar resistive switching (RS) behaviour observed from silver sulfide/silver (Ag2S/Ag) nanowire array and thin film structures fabricated under similar conditions. By examining the RS parameters measured using electrical probing with a similar tungsten probe on both types of structures, we conclude that the larger SET voltage and lower ON-state conductance in the thin film structures are the result of the longer conductive filamentary paths formed during the SET process. In addition, we found that the metal filament can be established at a constant voltage bias which is much lower than the measured SET voltage for a sweeping voltage bias, as long as the constant bias/stress voltage is applied for a sufficiently long duration. This time dependency in the SET process is possibly related to the migration and reduction of silver ions to form silver atoms at the filamentary formation site. Experimental results also show that an applied voltage bias, either with increasing magnitude or duration, will increase the ON-state conductance. This is explained by the increased cross-sectional area of the conductive filamentary path. From the comparative investigation of the RS parameter values obtained from the two different structures, it is concluded that nanostructuring of the Ag2S/Ag heterostructure from a two-dimensional thin film to a one-dimensional nanowire structure results in an improvement in the SET process parameters.

[Impregnation and liberation of nicotine with hydrogen copolymer discs]

Reticulated copolymers with products N-vinyl-2 pyrrolidone (NVP), hydroxy-2 ethyl (HEMA) and methyl methacrylate (MMA) were realized in disc form. Nicotine was used as active principle. On these discs the following study was carried out: permeation, percentage of liquid absorbed, texture, as well as nicotine release kinetics. A 2-variable (NVP and HEMA/MMA), 5-level experimental plan has enabled the outlining of the significant differences on the action of these parameters. The release kinetics show particularly that these discs behave as forms of prolonged released and that the released quantities are sufficient to envisage the use of these reticulated copolymers within the framework of a transdermal system.