Project description:Neurons in posterior parietal cortex contribute to the execution of goal-directed navigation and other decision-making tasks. Although molecular studies have catalogued over fifty cortical cell types, it remains unknown what distinct functions they serve during goal-directed navigation. Here, we identified a molecularly defined subset of somatostatin (Sst) inhibitory neurons that, in mouse posterior parietal cortex, carry a novel cell type-specific error correction signal for navigation. We obtained repeatable experimental access to these cells using an adeno-associated virus (AAV) in which gene expression is driven by an enhancer that functions specifically in a subset of Sst cells. We found that during goal-directed navigation in a virtual environment, this subset of Sst neurons activates in a synchronous pattern that is distinct from the activity of surrounding neurons, including other Sst neurons. Using in vivo two-photon photostimulation and ex vivo paired patch clamp recordings, we show that nearby cells of this Sst subtype excite each other through gap junctions, revealing a self-excitation circuit motif that contributes to the synchronous activity of this cell type. Remarkably, these cells selectively activate as mice execute course corrections for deviations in their virtual heading during navigation toward a reward location, both for self- and experimentally-induced deviations. We propose that this subtype of Sst neurons provides a self-reinforcing and cell type-specific error-correction signal in posterior parietal cortex that may aid the execution and learning of accurate goal-directed navigation trajectories.
Project description:Chromatin assembled with histone H3 variant CENP-A is the heritable epigenetic determinant of human centromere identity. Using genome-wide mapping and reference models for 23 human centromeres, CENP-A is shown in early G1 to be assembled into nucleosomes within megabase, repetitive a-satellite DNAs at each centromere and onto 11,390 sites on the chromosome arms. Centromere-bound CENP-A is found to be quantitatively maintained during DNA replication by coordinated action of the MCM2 helicase, CAF1, HJURP, and the CCAN network of constitutive centromere components. CCAN serves to tether CENP-A removed by MCM2, thereby enabling local reassembly onto both daughter centromeres with identical DNA sequence preferences and nucleosome phasing as the loading in G1 and independent of CENP-B. Conversely, without CCAN-mediated tethering, DNA replication removes CENP-A from sites on the chromosome arms. Our data identify an MCM2/CAF1/HJURP- and CCAN-dependent error correction mechanism that acts in S-phase to maintain CENP-A-dependent centromere identity.
Project description:Droplet-based single-cell sequencing techniques have provided unprecedented insight into cellular heterogeneities within tissues. However, these approaches only allow for the measurement of the distal parts of a transcript following short-read sequencing. Therefore, splicing and sequence diversity information is lost for the majority of the transcript. The application of long-read Nanopore sequencing to droplet-based methods is challenging because of the low base-calling accuracy currently associated with Nanopore sequencing. Although several approaches that use additional short-read sequencing to error-correct the barcode and UMI sequences have been developed, these techniques are limited by the requirement to sequence a library using both short- and long-read sequencing. Here we introduce a novel approach termed single-cell Barcode UMI Correction sequencing (scBUC-seq) to efficiently error-correct barcode and UMI oligonucleotide sequences synthesized by using blocks of dimeric nucleotides. The method can be applied to correct both short-read and long-read sequencing, thereby allowing users to recover more reads per cell that permits direct single-cell Nanopore sequencing for the first time. We illustrate our method by using species-mixing experiments to evaluate barcode assignment accuracy and multiple myeloma cell lines to evaluate differential isoform usage and Ewing’s sarcoma cells to demonstrate Ig fusion transcript analysis.
Project description:The gene expression profiles of murine visceral and parietal mesothelia were analyzed by microarray. Visceral and parietal mesothelia were isolated from the same adult Wt1-cre;Rosa26ReYFP reporter mice and analyzed. Whole tracscriptome expression analysis of total RNA was performed using Affymetrix mouse Gene 1.0 ST arrays.