The N=4 effective action of type IIA supergravity compactified on SU(2)-structure manifolds

We study compactifications of type IIA supergravity on six-dimensional manifolds with SU(2) structure and compute the low-energy effective action in terms of the non-trivial intrinsic torsion. The consistency with gauged N=4 supergravity is established and the gauge group is determined. Depending on the structure of the intrinsic torsion, antisymmetric tensor fields can become massive.Comment: 29 pages, latex, v2: minor corrections, added references, published versio

Spatial Transcriptomics of C. elegans Males and Hermaphrodites Identifies Sex-Specific Differences in Gene Expression Patterns

To advance our understanding of the genetic programs that drive cell and tissue specialization, it is necessary to obtain a comprehensive overview of gene expression patterns. Here, we have used spatial transcriptomics to generate high-resolution, anteroposterior gene expression maps of C. elegans males and hermaphrodites. To explore these maps, we have developed computational methods for discovering region- and tissue-specific genes. We have found extensive sex-specific gene expression differences in the germline and sperm and discovered genes that are specifically expressed in the male reproductive tract. These include a group of uncharacterized genes that encode small secreted proteins that are required for male fertility. We conclude that spatial gene expression maps provide a powerful resource for identifying tissue-specific gene functions in C. elegans. Importantly, we found that expression maps from different animals can be precisely aligned, enabling transcriptome-wide comparisons of gene expression patterns

Spatial Transcriptomics of C. elegans Males and Hermaphrodites Identifies Sex-Specific Differences in Gene Expression Patterns

To advance our understanding of the genetic programs that drive cell and tissue specialization, it is necessary to obtain a comprehensive overview of gene expression patterns. Here, we have used spatial transcriptomics to generate high-resolution, anteroposterior gene expression maps of C. elegans males and hermaphrodites. To explore these maps, we have developed computational methods for discovering region- and tissue-specific genes. We have found extensive sex-specific gene expression differences in the germline and sperm and discovered genes that are specifically expressed in the male reproductive tract. These include a group of uncharacterized genes that encode small secreted proteins that are required for male fertility. We conclude that spatial gene expression maps provide a powerful resource for identifying tissue-specific gene functions in C. elegans. Importantly, we found that expression maps from different animals can be precisely aligned, enabling transcriptome-wide comparisons of gene expression patterns

Spatio-temporal mRNA tracking in the early zebrafish embryo

Early stages of embryogenesis are known to depend on subcellular localization and transport of maternal mRNA, but systematic analyses have been hindered by a lack of methods for tracking of RNA. Here the authors combine spatially-resolved transcriptomics and single-cell RNA labeling to perform a spatio-temporal analysis of the transcriptome during early zebrafish development, revealing insights into this process

Postnatal Cardiac Gene Editing Using CRISPR/Cas9 With AAV9-Mediated Delivery of Short Guide RNAs Results in Mosaic Gene Disruption

RATIONALE: CRISPR/Cas9 (clustered regularly interspaced palindromic repeats/CRISPR-associated protein 9)-based DNA editing has rapidly evolved as an attractive tool to modify the genome. Although CRISPR/Cas9 has been extensively used to manipulate the germline in zygotes, its application in postnatal gene editing remains incompletely characterized. OBJECTIVE: To evaluate the feasibility of CRISPR/Cas9-based cardiac genome editing in vivo in postnatal mice. METHODS AND RESULTS: We generated cardiomyocyte-specific Cas9 mice and demonstrated that Cas9 expression does not affect cardiac function or gene expression. As a proof-of-concept, we delivered short guide RNAs targeting 3 genes critical for cardiac physiology, Myh6, Sav1, and Tbx20, using a cardiotropic adeno-associated viral vector 9. Despite a similar degree of DNA disruption and subsequent mRNA downregulation, only disruption of Myh6 was sufficient to induce a cardiac phenotype, irrespective of short guide RNA exposure or the level of Cas9 expression. DNA sequencing analysis revealed target-dependent mutations that were highly reproducible across mice resulting in differential rates of in- and out-of-frame mutations. Finally, we applied a dual short guide RNA approach to effectively delete an important coding region of Sav1, which increased the editing efficiency. CONCLUSIONS: Our results indicate that the effect of postnatal CRISPR/Cas9-based cardiac gene editing using adeno-associated virus serotype 9 to deliver a single short guide RNA is target dependent. We demonstrate a mosaic pattern of gene disruption, which hinders the application of the technology to study gene function. Further studies are required to expand the versatility of CRISPR/Cas9 as a robust tool to study novel cardiac gene functions in vivo

A single-cell atlas of de novo β-cell regeneration reveals the contribution of hybrid β/δ-cells to diabetes recovery in zebrafish

Regeneration-competent species possess the ability to reverse the progression of severe diseases by restoring the function of the damaged tissue. However, the cellular dynamics underlying this capability remain unexplored. Here, we have used single-cell transcriptomics to map de novo β-cell regeneration during induction and recovery from diabetes in zebrafish. We show that the zebrafish has evolved two distinct types of somatostatin-producing δ-cells, which we term δ1- and δ2-cells. Moreover, we characterize a small population of glucose-responsive islet cells, which share the hormones and fate-determinants of both β- and δ1-cells. The transcriptomic analysis of β-cell regeneration reveals that β/δ hybrid cells provide a prominent source of insulin expression during diabetes recovery. Using in vivo calcium imaging and cell tracking, we further show that the hybrid cells form de novo and acquire glucose-responsiveness in the course of regeneration. The overexpression of dkk3, a gene enriched in hybrid cells, increases their formation in the absence of β-cell injury. Finally, interspecies comparison shows that plastic δ1-cells are partially related to PP cells in the human pancreas. Our work provides an atlas of β-cell regeneration and indicates that the rapid formation of glucose-responsive hybrid cells contributes to the resolution of diabetes in zebrafish.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Integrated genome and transcriptome sequencing of the same cell

Single-cell genomics and single-cell transcriptomics have emerged as powerful tools to study the biology of single cells at a genome-wide scale. However, a major challenge is to sequence both genomic DNA and mRNA from the same cell, which would allow direct comparison of genomic variation and transcriptome heterogeneity. We describe a quasilinear amplification strategy to quantify genomic DNA and mRNA from the same cell without physically separating the nucleic acids before amplification. We show that the efficiency of our integrated approach is similar to existing methods for single-cell sequencing of either genomic DNA or mRNA. Further, we find that genes with high cell-to-cell variability in transcript numbers generally have lower genomic copy numbers, and vice versa, suggesting that copy number variations may drive variability in gene expression among individual cells. Applications of our integrated sequencing approach could range from gaining insights into cancer evolution and heterogeneity to understanding the transcriptional consequences of copy number variations in healthy and diseased tissues