BackgroundHuntington’s disease (HD) is an incurable hereditary neurodegenerative disorder, which manifests itself as a loss of GABAergic medium spiny (GABA MS) neurons in the striatum and caused by an expansion of the CAG repeat in exon 1 of the huntingtin gene. There is no cure for HD, existing pharmaceutical can only relieve its symptoms.ResultsHere, induced pluripotent stem cells were established from patients with low CAG repeat expansion in the huntingtin gene, and were then efficiently differentiated into GABA MS-like neurons (GMSLNs) under defined culture conditions. The generated HD GMSLNs recapitulated disease pathology in vitro, as evidenced by mutant huntingtin protein aggregation, increased number of lysosomes/autophagosomes, nuclear indentations, and enhanced neuronal death during cell aging. Moreover, store-operated channel (SOC) currents were detected in the differentiated neurons, and enhanced calcium entry was reproducibly demonstrated in all HD GMSLNs genotypes. Additionally, the quinazoline derivative, EVP4593, reduced the number of lysosomes/autophagosomes and SOC currents in HD GMSLNs and exerted neuroprotective effects during cell aging.ConclusionsOur data is the first to demonstrate the direct link of nuclear morphology and SOC calcium deregulation to mutant huntingtin protein expression in iPSCs-derived neurons with disease-mimetic hallmarks, providing a valuable tool for identification of candidate anti-HD drugs. Our experiments demonstrated that EVP4593 may be a promising anti-HD drug.Electronic supplementary materialThe online version of this article (doi:10.1186/s13024-016-0092-5) contains supplementary material, which is available to authorized users.

In the larval salivary glands of C. tentans, it is possible to visualize by electron microscopy how Balbiani ring (BR) pre-mRNA associates with proteins to form pre-mRNP particles, how these particles move to and through the nuclear pore, and how the BR RNA is engaged in the formation of giant polysomes in the cytoplasm. Here, we study C. tentans hrp36, an abundant protein in the BR particles, and establish that it is similar to the mammalian hnRNP A1. By immuno-electron microscopy it is demonstrated that hrp36 is added to BR RNA concomitant with transcription, remains in nucleoplasmic BR particles, and is translocated through the nuclear pore still associated with BR RNA. It appears in the giant BR RNA-containing polysomes, where it remains as an abundant protein in spite of ongoing translation.

The p53 tumor-suppressor protein has previously been shown to bind double-stranded and singlestranded DNA. We report that the p53 protein can bind single-stranded DNA ends and catalyze DNA renaturation and DNA strand transfer. Both a bacterially expressed wild-type p53 protein and a glutathione S-transferase-wild-type p53 fusion protein catalyzed renaturation of different short (25-to 76-nt) complementary single-stranded DNA fragments and promoted strand transfer between short (36-bp) duplex DNA and complementary single-stranded DNA. Mutant p53 fusion proteins carrying amino acid substitutions Glu-213, Ile-237, or Tyr-238, derived from mutant p53 genes of Burkitt lymphomas, failed to catalyze these reactions. Wild-type p53 had sigicantly higher binding affinity for short (36-to 76-nt) than for longer (.462-nt) single-stranded DNA fragments in an electrophoretic mobility-shift assay. Moreover, electron microscopy showed that p53 preferentially binds single-stranded DNA ends. Binding of DNA ends to p53 oligomers may allow alignment of complementary strands. These findings suggest that p53 may play a direct role in the repair of DNA breaks, including the joining of complementary single-stranded DNA ends.

SUMMARYThe nuclear envelope (NE) is a fundamental structure of eukaryotic cells with a dual role: it separates two distinct compartments, and enables communication between them via nuclear pore complexes (NPCs). Little is known about NPCs and NE structural organization in plants. We investigated the structure of NPCs from both sides of the NE in tobacco BY-2 cells. We detected structural differences between the NPCs of dividing and quiescent nuclei. Importantly, we also traced the organizational pattern of the NPCs, and observed nonrandom NPC distribution over the nuclear surface. Lastly, we observed an organized filamentous protein structure that underlies the inner nuclear membrane, and interconnects NPCs. The results are discussed within the context of the current understanding of NE structure and function in higher eukaryotes.