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47 Janelia Publications

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    07/27/20 | A programmable sequence of reporters for lineage analysis.
    Garcia-Marques J, Espinosa-Medina I, Ku K, Yang C, Koyama M, Yu H, Lee T
    Nature Neuroscience. 2020 Jul 27:. doi: 10.1038/s41593-020-0676-9

    We present CLADES (cell lineage access driven by an edition sequence), a technology for cell lineage studies based on CRISPR-Cas9 techniques. CLADES relies on a system of genetic switches to activate and inactivate reporter genes in a predetermined order. Targeting CLADES to progenitor cells allows the progeny to inherit a sequential cascade of reporters, thereby coupling birth order to reporter expression. This system, which can also be temporally induced by heat shock, enables the temporal resolution of lineage development and can therefore be used to deconstruct an extended cell lineage by tracking the reporters expressed in the progeny. When targeted to the germ line, the same cascade progresses across animal generations, predominantly marking each generation with the corresponding combination of reporters. CLADES therefore offers an innovative strategy for making programmable cascades of genes that can be used for genetic manipulation or to record serial biological events.

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    05/28/20 | Enhanced Golic+: Highly effective CRISPR gene targeting and transgene HACKing in .
    Chen H, Yao X, Ren Q, Chang C, Liu L, Miyares RL, Lee T
    Development. 2020 May 28:. doi: 10.1242/dev.181974

    Gene targeting is an incredibly valuable technique. Sometimes however, it can also be extremely challenging for various intrinsic reasons (e.g. low target accessibility or nature/extent of gene modification). To bypass these barriers, we designed a transgene-based system in Drosophila that increases the number of independent gene targeting events while at the same time enriching for correctly targeted progeny. Unfortunately, with particularly challenging gene targeting experiments, our original design yielded numerous false positives. Here we deliver a much-improved technique named Enhanced Golic+ (E-Golic+). E-Golic+ incorporates genetic modifications to tighten lethality-based selection while simultaneously boosting efficiency. With E-Golic+, we easily achieve previously unattainable gene targeting. Additionally, we built an E-Golic+ based, high-efficiency genetic pipeline for transgene swapping. We demonstrate its utility by transforming GAL4 enhancer-trap lines into tissue-specific Cas9-expressing lines. Given the superior efficiency, specificity and scalability, E-Golic+ promises to expedite development of additional sophisticated genetic/genomic tools in .

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    05/01/20 | Neuronal upregulation of Prospero protein is driven by alternative mRNA polyadenylation and Syncrip-mediated mRNA stabilisation.
    Samuels TJ, Arava Y, Järvelin AI, Robertson F, Lee JY, Yang L, Yang C, Lee T, Ish-Horowicz D, Davis I
    Biology Open. 2020 May;9(5):. doi: 10.1242/bio.049684

    During and vertebrate brain development, the conserved transcription factor Prospero/Prox1 is an important regulator of the transition between proliferation and differentiation. Prospero level is low in neural stem cells and their immediate progeny, but is upregulated in larval neurons and it is unknown how this process is controlled. Here, we use single molecule fluorescent hybridisation to show that larval neurons selectively transcribe a long mRNA isoform containing a 15 kb 3' untranslated region, which is bound in the brain by the conserved RNA-binding protein Syncrip/hnRNPQ. Syncrip binding increases the mRNA stability of the long isoform, which allows an upregulation of Prospero protein production. Adult flies selectively lacking the long isoform show abnormal behaviour that could result from impaired locomotor or neurological activity. Our findings highlight a regulatory strategy involving alternative polyadenylation followed by differential post-transcriptional regulation.

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    04/07/20 | Conservation and divergence of related neuronal lineages in the central brain.
    Lee Y, Yang C, Miyares RL, Huang Y, He Y, Ren Q, Chen H, Kawase T, Ito M, Otsuna H, Sugino K, Aso Y, Ito K, Lee T
    eLife. 2020 Apr 07;9:. doi: 10.7554/eLife.53518

    Wiring a complex brain requires many neurons with intricate cell specificity, generated by a limited number of neural stem cells. central brain lineages are a predetermined series of neurons, born in a specific order. To understand how lineage identity translates to neuron morphology, we mapped 18 central brain lineages. While we found large aggregate differences between lineages, we also discovered shared patterns of morphological diversification. Lineage identity plus Notch-mediated sister fate govern primary neuron trajectories, whereas temporal fate diversifies terminal elaborations. Further, morphological neuron types may arise repeatedly, interspersed with other types. Despite the complexity, related lineages produce similar neuron types in comparable temporal patterns. Different stem cells even yield two identical series of dopaminergic neuron types, but with unrelated sister neurons. Together, these phenomena suggest that straightforward rules drive incredible neuronal complexity, and that large changes in morphology can result from relatively simple fating mechanisms.

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    03/18/20 | CAMIO: a transgenic CRISPR pipeline to create diverse targeted genome deletions in Drosophila.
    Chen H, Marques JG, Sugino K, Wei D, Miyares RL, Lee T
    Nucleic Acids Research. 2020 Mar 18:. doi: 10.1093/nar/gkaa177

    The genome is the blueprint for an organism. Interrogating the genome, especially locating critical cis-regulatory elements, requires deletion analysis. This is conventionally performed using synthetic constructs, making it cumbersome and non-physiological. Thus, we created Cas9-mediated Arrayed Mutagenesis of Individual Offspring (CAMIO) to achieve comprehensive analysis of a targeted region of native DNA. CAMIO utilizes CRISPR that is spatially restricted to generate independent deletions in the intact Drosophila genome. Controlled by recombination, a single guide RNA is stochastically chosen from a set targeting a specific DNA region. Combining two sets increases variability, leading to either indels at 1-2 target sites or inter-target deletions. Cas9 restriction to male germ cells elicits autonomous double-strand-break repair, consequently creating offspring with diverse mutations. Thus, from a single population cross, we can obtain a deletion matrix covering a large expanse of DNA at both coarse and fine resolution. We demonstrate the ease and power of CAMIO by mapping 5'UTR sequences crucial for chinmo's post-transcriptional regulation.

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    12/01/19 | High-throughput dense reconstruction of cell lineages.
    Espinosa-Medina I, Garcia-Marques J, Cepko C, Lee T
    Open Biology. 2019 Dec 01;9(12):190229. doi: 10.1098/rsob.190229

    The first meeting exclusively dedicated to the 'High-throughput dense reconstruction of cell lineages' took place at Janelia Research Campus (Howard Hughes Medical Institute) from 14 to 18 April 2019. Organized by Tzumin Lee, Connie Cepko, Jorge Garcia-Marques and Isabel Espinosa-Medina, this meeting echoed the recent eruption of new tools that allow the reconstruction of lineages based on the phylogenetic analysis of DNA mutations induced during development. Combined with single-cell RNA sequencing, these tools promise to solve the lineage of complex model organisms at single-cell resolution. Here, we compile the conference consensus on the technological and computational challenges emerging from the use of the new strategies, as well as potential solutions.

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    10/23/19 | Unlimited genetic switches for cell-type-specific manipulation.
    Garcia-Marques J, Yang C, Espinosa-Medina I, Mok K, Koyama M, Lee T
    Neuron. 2019 Oct 23;104(2):227-38. doi: https://doi.org/10.1016/j.neuron.2019.07.005

    Gaining independent genetic access to discrete cell types is critical to interrogate their biological functions as well as to deliver precise gene therapy. Transcriptomics has allowed us to profile cell populations with extraordinary precision, revealing that cell types are typically defined by a unique combination of genetic markers. Given the lack of adequate tools to target cell types based on multiple markers, most cell types remain inaccessible to genetic manipulation. Here we present CaSSA, a platform to create unlimited genetic switches based on CRISPR/Cas9 (Ca) and the DNA repair mechanism known as single-strand annealing (SSA). CaSSA allows engineering of independent genetic switches, each responding to a specific gRNA. Expressing multiple gRNAs in specific patterns enables multiplex cell-type-specific manipulations and combinatorial genetic targeting. CaSSA is a new genetic tool that conceptually works as an unlimited number of recombinases and will facilitate genetic access to cell types in diverse organisms.

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    09/23/19 | Mamo decodes hierarchical temporal gradients into terminal neuronal fate.
    Liu L, Long X, Yang C, Miyares RL, Sugino K, Singer RH, Lee T
    Elife. 2019 Sep 23;8:. doi: 10.7554/eLife.48056

    Temporal patterning is a seminal method of expanding neuronal diversity. Here we unravel a mechanism decoding neural stem cell temporal gene expression and transforming it into discrete neuronal fates. This mechanism is characterized by hierarchical gene expression. First, neuroblasts express opposing temporal gradients of RNA-binding proteins, Imp and Syp. These proteins promote or inhibit translation, yielding a descending neuronal gradient. Together, first and second-layer temporal factors define a temporal expression window of BTB-zinc finger nuclear protein, Mamo. The precise temporal induction of Mamo is achieved via both transcriptional and post-transcriptional regulation. Finally, Mamo is essential for the temporally defined, terminal identity of α'/β' mushroom body neurons and identity maintenance. We describe a straightforward paradigm of temporal fate specification where diverse neuronal fates are defined via integrating multiple layers of gene regulation. The neurodevelopmental roles of orthologous/related mammalian genes suggest a fundamental conservation of this mechanism in brain development.

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    05/30/19 | CLADES: a programmable sequence of reporters for lineage analysis
    Garcia-Marques J, Yang C, Espinosa-Medina I, Koyama M, Lee T
    bioRxiv. 2019 May 30:. doi: https://doi.org/10.1101/655308

    We present CLADES (Cell Lineage Access Driven by an Edition Sequence), a technology for cell lineage studies based on CRISPR/Cas9. CLADES relies on a system of genetic switches to activate and inactivate reporter genes in a pre-determined order. Targeting CLADES to progenitor cells allows the progeny to inherit a sequential cascade of reporters, coupling birth order with reporter expression. This gives us temporal resolution of lineage development that can be used to deconstruct an extended cell lineage by tracking the reporters expressed in the progeny. When targeted to the germ line, the same cascade progresses across animal generations, marking each generation with the corresponding combination of reporters. CLADES thus offers an innovative strategy for making programmable cascades of genes that can be used for genetic manipulation or to record serial biological events.

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    03/26/19 | Neurotransmitter identity is acquired in a lineage-restricted manner in the Drosophila CNS.
    Lacin H, Chen H, Long X, Singer RH, Lee T, Truman JW
    Elife. 2019 Mar 26;8:. doi: 10.7554/eLife.43701

    The vast majority of the adult fly ventral nerve cord is composed of 34 hemilineages, which are clusters of lineally related neurons. Neurons in these hemilineages use one of the three fast-acting neurotransmitters (acetylcholine, GABA, or glutamate) for communication. We generated a comprehensive neurotransmitter usage map for the entire ventral nerve cord. We did not find any cases of neurons using more than one neurotransmitter, but found that the acetylcholine specific gene ChAT is transcribed in many glutamatergic and GABAergic neurons, but these transcripts typically do not leave the nucleus and are not translated. Importantly, our work uncovered a simple rule: All neurons within a hemilineage use the same neurotransmitter. Thus, neurotransmitter identity is acquired at the stem cell level. Our detailed transmitter- usage/lineage identity map will be a great resource for studying the developmental basis of behavior and deciphering how neuronal circuits function to regulate behavior.

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