Project description:Understanding the emergence of complex multicellular organisms from single totipotent cells, or ontogenesis, represents a foundational question in biology. The study of mammalian development is particularly challenging due to the difficulty of monitoring embryos in utero, the variability of progenitor field sizes, and the indeterminate relationship between the generation of uncommitted progenitors and their progression to subsequent stages. Here, we present a flexible, high information, multi-channel molecular recorder with a single cell (sc) readout and apply it as an evolving lineage tracer to define a mouse cell fate map from fertilization through gastrulation. By combining lineage information with scRNA-seq profiles, we recapitulate canonical developmental relationships between different tissue types and reveal an unexpected transcriptional convergence of endodermal cells from extra-embryonic and embryonic origins, illustrating how lineage information complements scRNA-seq to define cell types. Finally, we apply our cell fate map to estimate the number of embryonic progenitor cells and the degree of asymmetric partitioning within the pluripotent epiblast during specification. Our approach enables massively parallel, high-resolution recording of lineage and other information in mammalian systems to facilitate a quantitative framework for describing developmental processes.
Project description:The CRISPR-Cas universe continues to expand. The type II CRISPR-Cas system from Streptococcus pyogenes (SpyCas9) is most widely used for genome editing due to its high efficiency in cells and organisms. However, concentrating on a single CRISPR-Cas system imposes limits on target selection and multiplexed genome engineering. We hypothesized that CRISPR-Cas systems originating from different bacterial species could operate simultaneously and independently due to their distinct single-guide RNAs (sgRNAs) or CRISPR-RNAs (crRNAs), and protospacer adjacent motifs (PAMs). Additionally, we hypothesized that CRISPR-Cas activity in zebrafish could be regulated through the expression of inhibitory anti-CRISPR (Acr) proteins. Here, we use a simple mutagenesis approach to demonstrate that CRISPR-Cas systems from Streptococcus pyogenes (SpyCas9), Streptococcus aureus (SauCas9), Lachnospiraceae bacterium (LbaCas12a, previously known as LbCpf1), Acidaminococcus sp. (AspCas12a, previously known as AsCpf1) and Neisseria meningitidis (Nme2Cas9) are orthogonal systems capable of operating simultaneously in zebrafish. We implemented multichannel CRISPR recording using up to three CRISPR systems, and show that LbaCas12a may provide superior information density compared to previous methods. We also demonstrate that type II Acrs (anti-CRISPRs) are effective inhibitors of SpyCas9 in zebrafish. These results indicate that at least five CRISPR-Cas systems and two anti-CRISPR proteins are functional in zebrafish embryos. These orthogonal CRISPR-Cas systems and Acr proteins will enable combinatorial and intersectional strategies for spatiotemporal control of genome editing and genetic recording in animals.
Project description:Induced pluripotent stem cell (iPSC) derived organoid systems provide models to study human organ development. Single-cell transcriptome sequencing enables highly-resolved descriptions of cell state heterogeneity within these systems and computational methods can reconstruct developmental trajectories. However, new approaches are needed to directly measure lineage relationships in these systems. Here we establish an inducible dual channel lineage recorder, iTracer, that couples reporter barcodes, inducible CRISPR/Cas9 scarring, and single-cell transcriptomics to analyze state and lineage relationships in iPSC-derived systems. This data set include the iTracer-perturb data of one cerebral organoid with simultaneous TSC2 perturbation and lineage recording.
Project description:The mammalian brain is heterogeneous, containing billions of neurons and trillions of synapses forming various neural circuitries, through which sense, movement, thought, and emotion are generated. The cellular heterogeneity of the brain has made it difficult to study the molecular logic of neural circuitry wiring, pruning, activation, and plasticity, until recently, transcriptome analyses with single-cell resolution makes decoding of gene regulatory networks underlying aforementioned circuitry properties possible. Here, we report success in performing both electrophysiological and whole-genome transcriptome analyses on single human neurons in culture. Using Weighted Gene Coexpression Network Analyses (WGCNA), we identified gene clusters highly correlated with neuronal maturation judged by electrophysiological characteristics. A tight link between neuronal maturation and genes involved in ubiquitination and mitochondrial function was revealed. Moreover, we identified a list of candidate genes, which could potentially serve as biomarkers for neuronal maturation. Coupled electrophysiological recording and single-cell transcriptome analysis will serve as powerful tools in the future to unveil molecular logics for neural circuitry functions.
Project description:Cornelia de Lange syndrome (CdLS) is an autosomal dominant disease mainly caused by mutations in the Nipped-B-like protein (NIPBL) gene resulting in the alteration of the cohesin pathway. Here, we generated human induced pluripotent stem cells (hiPSCs) from a CdLS patient carrying a mutation in the NIPBL gene, c.5483G>A, and tested CRISPR-Cas based approaches to repair the genetic defect. We applied an efficient and precise method of gene correction through CRISPR-Cas induced homology directed repair (HDR), which allowed the generation of hiPSC clones with regular karyotype and preserved stemness. The efficient and precise gene replacement strategy developed in this study can be extended to the modification of other genomic loci in hiPSCs. Isogenic wild-type and mutated hiPSCs produced with the CRISPR-Cas technology are fundamental CdLS cellular models to study the disease molecular determinants and identifying therapeutic targets.