The Alternative Lengthening of Telomeres (ALT) pathway is a telomerase-independent pathway for telomere maintenance that is active in a significant subset of human cancers and in vitro immortalized cell lines. ALT is thought to involve templated extension of telomeres through homologous recombination, but the genetic or epigenetic changes that unleash ALT are not known. Recently, mutations in the ATRX/DAXX chromatin remodeling complex and histone H3.3 were found to correlate with features of ALT in pancreatic neuroendocrine cancers, pediatric glioblastomas, and other tumors of the central nervous system, suggesting that these mutations might contribute to the activation of the ALT pathway in these cancers. We have taken a comprehensive approach to deciphering ALT by applying genomic, molecular biological, and cell biological approaches to a panel of 22 ALT cell lines, including cell lines derived in vitro. Here we show that loss of ATRX protein and mutations in the ATRX gene are hallmarks of ALT–immortalized cell lines. In addition, ALT is associated with extensive genome rearrangements, marked micronucleation, defects in the G2/M checkpoint, and altered double-strand break (DSB) repair. These attributes will facilitate the diagnosis and treatment of ALT positive human cancers.

The microRNA miR-137 represses expression of Ezh2, a histone methyltransferase, which in turn alters the epigenetic architecture of chromatin that is important for regulation of miR-137 levels.

Fragile X syndrome (FXS), the most common form of inherited mental retardation, is caused by the loss of functional fragile X mental retardation protein (FMRP). FMRP is an RNA–binding protein that can regulate the translation of specific mRNAs. Adult neurogenesis, a process considered important for neuroplasticity and memory, is regulated at multiple molecular levels. In this study, we investigated whether Fmrp deficiency affects adult neurogenesis. We show that in a mouse model of fragile X syndrome, adult neurogenesis is indeed altered. The loss of Fmrp increases the proliferation and alters the fate specification of adult neural progenitor/stem cells (aNPCs). We demonstrate that Fmrp regulates the protein expression of several components critical for aNPC function, including CDK4 and GSK3β. Dysregulation of GSK3β led to reduced Wnt signaling pathway activity, which altered the expression of neurogenin1 and the fate specification of aNPCs. These data unveil a novel regulatory role for Fmrp and translational regulation in adult neurogenesis.

Small interfering RNAs (siRNAs) and microRNAs (miRNAs) are sequence-specific posttranscriptional regulators of gene expression. Although major components of the RNA interference (RNAi) pathway have been identified, regulatory mechanisms for this pathway remain largely unknown. Here we demonstrate that the RNAi pathway can be modulated intracellularly by small molecules. We have developed a cell-based assay to monitor the activity of the RNAi pathway and find that the small-molecule enoxacin (Penetrex) enhances siRNA-mediated mRNA degradation and promotes the biogenesis of endogenous miRNAs. We show that this RNAi-enhancing activity depends on the trans-activation-responsive region RNA-binding protein. Our results provide a proofof-principle demonstration that small molecules can be used to modulate the activity of the RNAi pathway. RNAi enhancers may be useful in the development of research tools and therapeutics.

Scleroderma renal crisis (SRC) is a rare, potentially life-threatening complication that affects 2-15% of patients with systemic sclerosis (SSc, also known as scleroderma). SRC typically presents in patients with early, rapidly progressive, diffuse cutaneous SSc within the first 3-5 years after the onset of a non-Raynaud sign or symptom. SRC is characterized by an acute, usually symptomatic increase in blood pressure, a rise in serum creatinine levels, oliguria and thrombotic microangiopathy in about 50% of patients. The prognosis of SRC substantially improved in the 1980s with the introduction of angiotensin-converting-enzyme inhibitors for rapid blood pressure control, with additional antihypertensive agents as required. However, the survival of patients with SRC can still be improved. Current patient survival is 70-82% at 1 year, but decreases to 50-60% at 5 years despite dialysis support. Patients with SRC who show no signs of renal functional recovery despite timely blood pressure control are candidates for transplantation. In this Review, we discuss progress made in the identification and proactive management of patients at risk of SRC and make recommendations aimed at optimizing management for those who progress to chronic kidney failure.

The spin and orbital angular momentum (SAM and OAM) of light is providing a new gateway toward high capacity and robust optical communications. While the generation of light with angular momentum is well studied in linear optics, its further integration into nonlinear optical devices will open new avenues for increasing the capacity of optical communications through additional information channels at new frequencies. However, it has been challenging to manipulate the both SAM and OAM of nonlinear signals in harmonic generation processes with conventional nonlinear materials. Here, we report the generation of spin-controlled OAM of light in harmonic generations by using ultrathin photonic metasurfaces. The spin manipulation of OAM mode of harmonic waves is experimentally verified by using second harmonic generation (SHG) from gold meta-atom with 3-fold rotational symmetry. By introducing nonlinear phase singularity into the metasurface devices, we successfully generate and measure the topological charges of spin-controlled OAM mode of SHG through an on-chip metasurface interferometer. The nonlinear photonic metasurface proposed in this work not only opens new avenues for manipulating the OAM of nonlinear optical signals but also benefits the understanding of the nonlinear spin-orbit interaction of light in nanoscale devices.

Fragile X–associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder seen in Fragile X premutation carriers. Previous studies found that Fragile X rCGG repeats are sufficient to cause neurodegeneration and that the rCGG repeat-binding proteins Pur α and hnRNP A2/B1 can modulate rCGG–mediated neuronal toxicity. To explore the role of Pur α in rCGG–mediated neurodegeneration further, we took a proteomic approach and identified more than 100 proteins that interact with Pur α. Of particular interest is Rm62, the Drosophila ortholog of p68 RNA helicase, which could modulate rCGG–mediated neurodegeneration. Here we show that rCGG repeats decreased the expression of Rm62 posttranscriptionally, leading to the nuclear accumulation of Hsp70 transcript, as well as additional mRNAs involved in stress and immune responses. Together these findings suggest that abnormal nuclear accumulation of these mRNAs, likely as a result of impaired nuclear export, could contribute to FXTAS pathogenesis.

presence of nanoclay in aqueous system. Here, novel natural tube-like nanoparticles, halloysite nanotubes (HNTs), are firstly used as multifunctional cross-linkers for polyacrylamide (PAAm) to form a new type of organic/inorganic hybrid hydrogels. Significant improvements in mechanical properties of the PAAm-HNTs NC gels are found by the addition of HNTs as shown by the static mechanical testing and dynamic viscoelasticity measurement. HNTs are uniformly dispersed in the NC gels from the morphological result. HNTs can be intercalated by PAAm chains as observed by the X-ray diffraction result. Hydrogen bonding interactions between HNTs and PAAm are confirmed by the infrared spectroscopy and X-ray photoelectron spectroscopy. The maximum equilibrium degree of swelling (EDS) for the NC gel is 4000% and the EDS decreases with the concentration of clay nanotubes. The present work provides a novel routine for preparing NC gels using "green" onedimensional nanoparticle. The prepared NC gels have promising application in biomedical areas due to the superior mechanical properties of the gels and good biocompatibility of HNTs.Keywords Halloysite nanotubes . Hydrogel . Mechanical properties . Nanocomposite mer and inorganic nanoparticle was first proposed and fabricated by Haraguchi, a Japanese scientist, in 2002 [1]. The NC gels can be synthesized through in situ free-radical polymerization of water-soluble monomers such as acrylamide and 2-methoxyethylacrylate in the presence of nanoclay in aqueous system, in which the nanoclays act as the multifunctional cross-linking points for the polymer chains [2][3][4]. Compared with traditional organic cross-linked hydrogel, the NC gels have a unique structure and properties, for example, super optical transparency, ultrahigh tensile extensibility, high swollen ratio and stimuli sensitivities [2]. Therefore, NC gels have been found to be applicable as super-absorbent materials, biomedical materials, smart materials, and so on. A wide range of clay minerals with layered crystal structures, good water swellability, and strong interactions with the water soluble monomers are used as the inorganic component for the NC gels. Typical examples include the smectite-group clays (hectorite, saponite, montmorillonite and so on) and mica-group clays (synthetic fluorine mica). Among these, the artificially synthesized layered silicate "Laponite," with the molecular formula of [Mg 5.34 Li 0.66 Si 8 O 20 (OH) 4 ]Na 0.66 , is mostly used for the preparation of NC gels. Laponite has sufficiently small platelet size (30 nm (diameter)×1 nm (thickness)) and high swelling ability in water (about 35×) for forming clear and colorless colloid dispersion. A series of NC gels have been prepared by combining Laponite with different monomers [1,[4][5][6]. The ability of forming inorganic/organic hybrid network for NC gels depends on the interactions between the nanoclay and the monomer/polymers, such as, hydrogen bonding and/or ionic interaction. On the other hand, the NC gels cannot be obtained by the polymer...