Hierarchal single-cell lineage tracing reveals differential fate commitment of CD8 T-cell clones in response to acute infection.

Generating balanced populations of CD8 effector and memory T cells is necessary for immediate and durable immunity to infections and cancer. Yet, a definitive understanding of CD8 differentiation remains unclear. We used CARLIN, a processive lineage recording mouse model with single-cell RNA-seq and TCR-seq to track endogenous antigen-specific CD8 T cells during acute viral infection. We identified a diverse repertoire of expanded T-cell clones represented by seven transcriptional states. TCR enrichment analysis revealed differential memory- or effector-fate biases within clonal populations. Shared Vb segments and amino acid motifs were found within biased categories despite high TCR diversity. Using single-cell CARLIN barcode-seq we tracked multi-generational clones and found that unlike unbiased or memory-biased clones, which stably retain their fate profiles, effector-biased clones could adopt memory- or effector-bias within subclones. Collectively, our study demonstrates that a heterogenous T-cell repertoire specific for a shared antigen is composed of clones with distinct TCR-intrinsic fate-biases.

Multiplexed Assembly and Annotation of Synthetic Biology Constructs Using Long-Read Nanopore Sequencing.

Recombinant DNA is a fundamental tool in biotechnology and medicine. These DNA sequences are often built, replicated, and delivered in the form of plasmids. Validation of these plasmid sequences is a critical and time-consuming step, which has been dominated for the last 35 years by Sanger sequencing. As plasmid sequences grow more complex with new DNA synthesis and cloning techniques, we need new approaches that address the corresponding validation challenges at scale. Here we prototype a high-throughput plasmid sequencing approach using DNA transposition and Oxford Nanopore sequencing. Our method, Circuit-seq, creates robust, full-length, and accurate plasmid assemblies without prior knowledge of the underlying sequence. We demonstrate the power of Circuit-seq across a wide range of plasmid sizes and complexities, generating full-length, contiguous plasmid maps. We then leverage our long-read data to characterize epigenetic marks and estimate plasmid contamination levels. Circuit-seq scales to large numbers of samples at a lower per-sample cost than commercial Sanger sequencing, accelerating a key step in synthetic biology, while low equipment costs make it practical for individual laboratories.

Rac1 plays an essential role in axon growth and guidance and in neuronal survival in the central and peripheral nervous systems.

BACKGROUND: Rac1 is a critical regulator of cytoskeletal dynamics in multiple cell types. In the nervous system, it has been implicated in the control of cell proliferation, neuronal migration, and axon development. RESULTS: To systematically investigate the role of Rac1 in axon growth and guidance in the developing nervous system, we have examined the phenotypes associated with deleting Rac1 in the embryonic mouse forebrain, in cranial and spinal motor neurons, in cranial sensory and dorsal root ganglion neurons, and in the retina. We observe a widespread requirement for Rac1 in axon growth and guidance and a cell-autonomous defect in axon growth in Rac1 (-/-) motor neurons in culture. Neuronal death, presumably a secondary consequence of the axon growth and/or guidance defects, was observed in multiple locations. Following deletion of Rac1 in the forebrain, thalamocortical axons were misrouted inferiorly, with the majority projecting to the contralateral thalamus and a minority projecting ipsilaterally to the ventral cortex, a pattern of misrouting that is indistinguishable from the pattern previously observed in Frizzled3 (-/-) and Celsr3 (-/-) forebrains. In the limbs, motor-neuron-specific deletion of Rac1 produced a distinctive stalling of axons within the dorsal nerve of the hindlimb but a much milder loss of axons in the ventral hindlimb and forelimb nerves, a pattern that is virtually identical to the one previously observed in Frizzled3 (-/-) limbs. CONCLUSIONS: The similarities in axon growth and guidance phenotypes caused by Rac1, Frizzled3, and Celsr3 loss-of-function mutations suggest a mechanistic connection between tissue polarity/planar cell polarity signaling and Rac1-dependent cytoskeletal regulation.

Role of apoptosis signal-regulating kinase 1 (ASK1) as an activator of the GAPDH-Siah1 stress-signaling cascade.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) plays roles in both energy maintenance, and stress signaling by forming a protein complex with seven in absentia homolog 1 (Siah1). Mechanisms to coordinate its glycolytic and stress cascades are likely to be very important for survival and homeostatic control of any living organism. Here we report that apoptosis signal-regulating kinase 1 (ASK1), a representative stress kinase, interacts with both GAPDH and Siah1 and is likely able to phosphorylate Siah1 at specific amino acid residues (Thr-70/Thr-74 and Thr-235/Thr-239). Phosphorylation of Siah1 by ASK1 triggers GAPDH-Siah1 stress signaling and activates a key downstream target, p300 acetyltransferase in the nucleus. This novel mechanism, together with the established S-nitrosylation/oxidation of GAPDH at Cys-150, provides evidence of how the stress signaling involving GAPDH is finely regulated. In addition, the present results imply crosstalk between the ASK1 and GAPDH-Siah1 stress cascades.

Oxidative stress and schizophrenia: recent breakthroughs from an old story.

PURPOSE OF REVIEW: Oxidative stress has become an exciting area of schizophrenia research, and provides ample opportunities and hope for a better understanding of its pathophysiology, which may lead to novel treatment strategies. This review describes how recent methodological advances have allowed the study of oxidative stress to tackle fundamental questions and have provided several conceptual breakthroughs to the field. RECENT FINDINGS: Recent human studies support the notion that intrinsic susceptibility to oxidative stress may underlie the pathophysiology of schizophrenia. More than one animal model that may be relevant to study the biology of schizophrenia also shows sign of oxidative stress in the brain. SUMMARY: These advances have made this topic of paramount importance to the understanding of schizophrenia and will play a role in advancing the treatment options. This review covers topics from the classic biochemical studies of human biospecimens to the use of magnetic resonance spectroscopy and novel mouse models, and focuses on highlighting the promising areas of research.