Project description:Single cell RNA-seq is a powerful methodology, but with important limitations. In particular, the process of enzymatic separation of cells at 37O C can be expected to result in artifact changes in gene expression patterns. We here describe a dissociation method that uses protease from a psychrophilic microorganism with high activity in the cold. The entire procedure is carried out at 6O C or colder, where mammalian transcriptional machinery is largely inactive. To test this method we carry out single cell RNA-seq on about 9,000 cells, comparing the results of the cold method with a method using 37O C incubations for multiple times. We show that the cold active protease method results in a great reduction in gene expression artifacts.
Project description:We characterized membranes with chloroplast ribosomes during chloroplast development (using the yellow-in-the-dark 1 mutant) and carried out proteomic analyses of two distinct membrane types as translation platforms for chloroplast ribosomes. The results support roles of “low-density membrane” as a platform for preliminary stages of translation and of a denser “chloroplast translation membrane” as a platform for ongoing translation. These roles are based on the proteomes of these membranes, which include proteins in translation, photosystem biogenesis and the biosynthesis of chlorophyll and correlations of their relative levels and the translational status of the chloroplast before, during and after chloroplast differentiation.
Project description:The morphogen and mitogen, Sonic Hedgehog, activates a Gli1-dependent transcription program that drives proliferation of granule neuron progenitors (GNPs) within the external germinal layer of the postnatally developing cerebellum. Medulloblastomas with mutations activating the Sonic Hedgehog signaling pathway preferentially arise within the external germinal layer, and the tumor cells closely resemble GNPs. Atoh1/Math1, a basic helix-loop-helix transcription factor essential for GNP histogenesis, does not induce medulloblastomas when expressed in primary mouse GNPs that are explanted from the early postnatal cerebellum and transplanted back into the brains of naïve mice. However, enforced expression of Atoh1 in primary GNPs enhances the oncogenicity of cells overexpressing Gli1 by almost three orders of magnitude. Unlike Gli1, Atoh1 cannot support GNP proliferation in the absence of Sonic Hedgehog signaling and does not govern expression of canonical cell cycle genes. Instead, Atoh1 maintains GNPs in a Sonic Hedgehog-responsive state by regulating genes that trigger neuronal differentiation, including many expressed in response to bone morphogenic protein-4. Therefore, by targeting multiple genes regulating the differentiation state of GNPs, Atoh1 collaborates with the pro-proliferative Gli1-dependent transcriptional program to influence medulloblastoma development. Keywords: disease state analysis