Rationale Cardiomyocytes in adult mammalian hearts are terminally differentiated cells that have exited from the cell cycle and lost most of their proliferative capacity. Death of mature cardiomyocytes in pathological cardiac conditions and the lack of regeneration capacity of adult hearts are primary causes of heart failure and mortality. However, how cardiomyocyte proliferation in postnatal and adult hearts becomes suppressed remains largely unknown. The miR-17-92 cluster was initially identified as a human oncogene that promotes cell proliferation. However, its role in the heart remains unknown. Objective To test the hypothesis that miR-17-92 participates in the regulation of cardiomyocyte proliferation in postnatal and adult hearts. Methods and Results We deleted miR-17-92 cluster from embryonic and postnatal mouse hearts and we demonstrated that miR-17-92 is required for cardiomyocyte proliferation in the heart. Transgenic overexpression of miR-17-92 in cardiomyocytes is sufficient to induce cardiomyocyte proliferation in embryonic, postnatal and adult hearts. Moreover, overexpression of miR-17-92 in adult cardiomyocytes protects the heart from myocardial infarction-induced injury. Similarly, we found that members of miR-17-92 cluster, miR-19 in particular, are required for and sufficient to induce cardiomyocyte proliferation in vitro. We identified PTEN, a tumor suppressor, as a miR-17-92 target to mediate the function of miR-17-92 in cardiomyocyte proliferation. Conclusions Our studies therefore identify miR-17-92 as a critical regulator of cardiomyocyte proliferation and suggest this cluster of miRNAs could become therapeutic targets for cardiac repair and heart regeneration.

Photonic nanostructures are created in organo-metal halide perovskites by thermal nanoimprint lithography at a temperature of 100 °C. The imprinted layers are significantly smoothened compared to the initially rough, polycrystalline layers and the impact of surface defects is substantially mitigated upon imprint. As a case study, 2D photonic crystals are shown to afford lasing with ultralow lasing thresholds at room temperature.

Thermoelectric (TE) materials convert heat energy directly into electricity, and introducing new materials with high conversion efficiency is a great challenge because of the rare combination of interdependent electrical and thermal transport properties required to be present in a single material. The TE efficiency is defined by the figure of merit ZT=(S(2) σ) T/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the total thermal conductivity, and T is the absolute temperature. A new p-type thermoelectric material, CsAg5 Te3 , is presented that exhibits ultralow lattice thermal conductivity (ca. 0.18 Wm(-1)  K(-1) ) and a high figure of merit of about 1.5 at 727 K. The lattice thermal conductivity is the lowest among state-of-the-art thermoelectrics; it is attributed to a previously unrecognized phonon scattering mechanism that involves the concerted rattling of a group of Ag ions that strongly raises the Grüneisen parameters of the material.

To investigate roles of the discriminator and open complex (OC) lifetime in transcription initiation by Escherichia coli RNA polymerase (RNAP; α 2 ββ'ωσ 70 ), we compare productive and abortive initiation rates, short RNA distributions, and OC lifetime for the λP R and T7A1 promoters and variants with exchanged discriminators, all with the same transcribed region. The discriminator determines the OC lifetime of these promoters. Permanganate reactivity of thymines reveals that strand backbones in open regions of longlived λP R -discriminator OCs are much more tightly held than for shorter-lived T7A1-discriminator OCs. Initiation from these OCs exhibits two kinetic phases and at least two subpopulations of ternary complexes. Long RNA synthesis (constrained to be single round) occurs only in the initial phase (<10 s), at similar rates for all promoters. Less than half of OCs synthesize a full-length RNA; the majority stall after synthesizing a short RNA. Most abortive cycling occurs in the slower phase (>10 s), when stalled complexes release their short RNA and make another without escaping. In both kinetic phases, significant amounts of 8-nt and 10-nt transcripts are produced by longer-lived, λP R -discriminator OCs, whereas no RNA longer than 7 nt is produced by shorter-lived T7A1-discriminator OCs. These observations and the lack of abortive RNA in initiation from short-lived ribosomal promoter OCs are well described by a quantitative model in which ∼1.0 kcal/mol of scrunching free energy is generated per translocation step of RNA synthesis to overcome OC stability and drive escape. The different length-distributions of abortive RNAs released from OCs with different lifetimes likely play regulatory roles.RNA polymerase | open complex lifetime | transcription initiation | abortive RNA | hybrid length M any facets of transcription initiation by E. coli RNA polymerase (RNAP; α 2 ββ′ωσ 70 ) have been elucidated, but significant questions remain about the mechanism or mechanisms by which initial transcribing complexes (ITC) with a short RNA-DNA hybrid decide to advance and escape from the promoter to enter elongation mode, or, alternately, to stall, release their short RNA, and reinitiate (abortive cycling). For RNAP to escape, its sequencespecific interactions with promoter DNA in the binary open complex (OC) must be overcome.The open regions of promoter DNA in the binary OC are the −10 region (six residues, with specific interactions between σ 2.2 and the nontemplate strand), the discriminator region (typically six to eight residues with no consensus sequence, the upstream end of which interacts with σ 1.2 ), and the transcription start site (TSS, +1) and adjacent residue (+2), which are in the active site of RNAP (Table 1). The interactions involving and directed by the six-residue λP R discriminator make its OC longlived and highly stable (1). A six-residue discriminator allows the OC to form without deforming (prescrunching) either open discriminator strand (2). Less extensive interactions involving and directed...